Comprehensive Industry DocumentSeries: COINDS/30/88-89

MINIMAL NATIONAL STANDARDSPETROCHEMICALS INDUSTRY (BASIC AND INTERMEDIATES)

CENTRAL POLLUTION CONTROL`^^ BOARD DELHI

FOREWORD

The Minimal National Standards (MINAS) for liquid effluent discharged from anyparticular type of industry are such that they are technoeconomically achievableby the industry. A State Pollution Control Board may prescribe stringent stand-ards while stipulating standards to any specific Industrial unit, depending uponerr. ironmental requirements. In the present document MINAS for Petrochemi-cal Industries (Basic and Intermediate) are presented. Downstream productslike manmade fibre, plastics and polymers etc. are already covered in separatedocuments. In this document treatment technology to achieve the standards isalso briefly described.

Petrochemical Industries, State Pollution Control Boards and those concernedwith Environment, I hope, will find this document useful. This summary docu-ment is based on the comprehensive Industry document on Petrochemical in-dustry prepared by M/s Engineers India Limited (EIL) and In-depth studiesconducted by the Central Pollution Control Board In association with Gujaratand Maharashtra State Pollution Control Boards. The service rendered by M/sEIL and the cooperation extended by the two State Pollution Control Boards aredeeply appreciated.

PARITOSH C. TYAGICHAIRMAN

17 FEBRUARY, 1989NEW DELHI

CENTRAL POLLUTION CONTROL BOARD STUDY TEAM

1. Project Leader

2. Data interpretation& analysis

3. Analytical Team

4. Editing of the report and finalisation

5. Dra'r.ings

6. Typing

7. Printing Supervision

Sh. N.K. Verma, Environmental Engineer

Sh. D.D. Basu, Scientist'B'

a. Sh. Sanjeev Kumar PaliwalJr. Scientific Assistant

b. Sh. Mahendra PandeyJr. Scientific Assistant

c. Sh. Ashok Kumar SinghJr. Scientific Assistant

a. Dr. K.R. RatiganathanMember Secetary

b. Sh. G.S. RayConsultant

1. Smt. Bonya Basu

2. Shri K.K. Gupta

1. Sh. Ramesh Chander

2. Sh. Pradeep Biswas

1. Dr. M.A. Hague

2. Sh. Prashanta K Biswas

CONTENTS

Page

1. Introduction1.1 Introduction 31.2 Classification 31.3 Approach for development of Minimal National 3

Standards (MINAS)

2. Status of Petrochemical Industry In India2.1 Status of Petrochemical Industry In India 92.2 Present Status of Petrochemical Industry 92.3 Future of Petrochemical Industry 9

3. Manufacturing Process3.1 Unit Process 13

3.2 Chemistry of Manufacture 13

1. Wastewater Characterisation..4.1 Wastewater Charactérisation 334.2 Water use pattern 33:.3 Wastewater generation 344.4 1.^.ass balance 344-5 Wastewater from utility section 344.5 Process wastewater characterisation 37

Treatment status5.1 Tr ea -er% piosophy 455.2 Treatrner c f waste 475.3 Status of treatment in India 545.4 Cost of effluent treatment plant 60

6. Minimal National Standards6.1 Philosophy of MINAS 65

6.2 Waste water quality parameters 656.3 Economic feasibility 656.4 Comparative statement of standards 666.5 Standards to satisfy environmental requirements 66

LIST OF TABLES

Page51. Table 1.1

2. Table 2.1

3. Table 2.2

4. Table 4.1

5. Table 4.2

6. Table 4.3

7. Tat!9 4.4

8. Table 4.5

9. Table 4.6

10. Table 4.7

11. Table 4.8

12. Table 4.9

13. Table 5.1

14. Table 5.2

15. Table 5.3

16. Table 5.4

17. Table 5.5

18. Table 5.6

19. Table 5.7

20. Table 5.8

21. Table 5.9

22. Table 5.10

Classification of petrochemicalproducts

List of petrochemical Industriesin India

Demand, Supply and Deficit

Water usage pattern in operating units

Wastewater generation

Typical analysis of cooling. towerBlow down

Plantwise storm water characterisation

Storm water characteristic of a petrochemicalComplex

Plantwise process waste profile

Product wise waste water chracteristics

Pollutants from processes

Characteristics of spent caustic waste

Breakup of Hydraulic load

Inplant control measures and recovery system

Performance of cyanide treatment plant

Performance.. data of sulphide removal unit

BOD value for some pure organic compoundsoften found In petrochemical waste

Typical wastewater quality criteria foractivated sludge process

Comparative performance of aerobicbiological process

Performance of treatment unit

Performance evaluation of ETP

Cost module

9

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34

36

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60

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iv

LIST OF FIGURES

Page1 Fig. 1 Petrochemical product tree 4

2. Fig. 3.1 Process flow diagram: olefin plant Ethylene/ 15propylene Manufacture (Napthacracker)

3. Fig. 3.2 Process flow diagram : Vinyl Chloride monomer 17

4. Fig. 3.3 Process flow diagram : Solvent plant (IPA, 18Acetone, DAA, MIBK)

5. Fig. 3.4 Process flow diagram: Solvent plant (NBA, 20IBA, and 2 EHA)

6. Fig. 3.5 Process flow diagram : Acrylonitrile 21

7. Fig. 3.6 Process flow diagram: Benzene/ Toluene/ 23Xyiene

8. Fig. 3.7 Process flow diagram : , Caprolactum 24

9. Fig. 3.8 Process flow diagram: Detergent Alkylate 26

10. Fig. 3.9 Process flow diagram: Phthalic Anhydride 27

11. Fig. 3.10 Process flow diagram: Dimethyl Terephthalate 28

12. Fig. 4.1 Mass balance of water consumption and 35effluent generation

13. Fig. 5.1 Flow Sheet: Effluent treatment 55plant (Phenol, Cumene Complex) of Herdillia complex

14. Fig. 5.2 Flow Sheet: Caprolactum effluent treatment 56plant of GSFC

15. Fig. 5.3 Flow Sheet: Effluent treatment plant of NOCIL 58

16. Fig. 5.4 Flow Sheet : Effluent characteristics of NOCIL 59

17. Fig. 5.5 Flow Sheet: Effluent treatment facility of 61IPCL

vi

23. Table 6.1 Cost of treatment In petrochemical

66Industry

24. Table 6.2 Comparative statements of standards

67and MINAS

25. Table 6.3 Minimal National Standards

67

26. Table 6.4 Water quality criteria

68

66 INTRODUCTION

67 Synthetic organic chemicals are processed from naturally occuring raw materials viz, petroleum, naturalgas, coal etc. Coal was Initially the basic raw material for organic chemical Industry. However, during thelast two decades the basic feedstock has changed from coal to petroleum based raw materials. This Is

67

attributed to the recent Innovation and technological advance in the field of chemical Industry based onpetroleum feedstock. The handling and processing cost of petroleum based raw materials to down-§tream

68 products are cheaper than that based on coal although the cost of coal is about one fourth that ofpetroleum based feedstock. The emergence of manufacturing Industries like high polymers, syntheticfibres, plastics and plasticisers, synthetic rubbers, pesticides, carbon black, detergents, fertilisers andother similar products are the outcome of the technological developments In the field of chemicals, basedon petroleum feedstock.

Synthetic organic chemicals can also be obtained from other alternative sources like ethylalcohol frommolasses or acetylene from calcium carbide or benzene from cokeoven by-products. But through theapplication of new process technology in the field of petrochemicals based on feedstock available fromrefineries, there is a positive shift to petroleum feedstock. Thermoplastics, synthetic fibres and syntheticrubber are available in bulk after introduction of petrochemical industries In the country. Although thereis no precise definition of petrochemicals but generallly it refers to organic. chemicals derived from rawmaterials of petroleum origin. The raw materials of petroleum origin are curde oil, natural gas, off gasesresidues from refinery. In general, the manufacturing processes of petrochemicals involve raw materialsundergoing one or more chemical reactions followed by different unit operations to separate the productfrom side products and co-products.

T he range of chemicals In systematic sequential chain produced in petrochemical Industries are presentedin Fig. 1.1.

CLASSIFICATION

An examination of the product tree (Fig 1.1) reveals that the entire product spectrum can be classifiedinto the following three classes :

Building block or primary petrochemical products• Intermediate products or secondary petrochemical products, produced from building block.• Final or end products, coming from intermediate products.

The chemicals falling under the three classes are listed in Table 1.1. Each class is further classified basedan nature of products.

APPROACH FOR DEVELOPMENT OF MINIMAL NATIONAL STANDARDS (MINAS)

Petrochemical Industries manufacture various products. Thus, the product pattern will reflect in thecharacter of wastewater.

Generally the primary and intermediate products are considered to be the basic chemicals of petrochemi-calindustry. Therefore, the MINAS will be applicable to industries engaged In the manufacture of primaryand intermediate products.

However, in the petrochemical complex, sometimes downstream products are also manufactured be-cause of their inherent linkage with their Immediate predecessor e.g. man-made fibre from DMT/TPA,Accytonitrile or phenolic compounds from phenol, some kind of polymer products from basic materialsetc. in such cases, MINAS will also include additional parameters as given In the MINAS of the end product.The principle adopted may be summed up as follows:

- MINAS of petrochemical units will be for upstream primary and less Intermediate products.

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Downstream products will be covered under separate MINAS like"Manmade Fibre", "Organic Chemi-cals", "Plastics and Polymers", "Soap and detergent" etc.

- If a downstream unit exist in petrochemical complex, the MINAS of petrochemical unit will cover thedownstream units with the addition of the left out parameters stipulated in MINAS of that category ofindustry.

Table 1.1 : Classification of Petrochemicals Products

Feedstock Primary products Intermediate Finalproducts products

Naphtha Olefins/Diolefins : Orq na ics : Plastics and Resins:1. Ethylene 1. Ethylene oxide 1. High density poly

ethylene (HDPE)/Low density poly-ethylene (LDPE)

2. Propylene 2. Ethylene Glycols 2. Polypropylene3. Butadiene 3. Propylenp Oxide 3. Poly Vinyl Chloride (PVC)

4. Isopropyl Alcohol 4. PolystyreneAromatics: 5.2-Ethyl Hexanol 5. Polyester resins1. Benzene 6. Phthalic 6. Alkyl Resins

Anhydride2. Toluene 7. Maleic Anhy- 7. Polyurathene Resins

dride3. Xylene 8. Phenol 8. Pf Resins

9. Styrene 9. Alkyl BenzeneSulphonate (ABS) Resins

10. Polyethylene Synthetic Fibre:11. Chlorinated 1. Nylon Filament Fibre

hydrocarbonO0 12. Isocynates 2. Nylon tyre cord and

other fibreC. 13. Cumene 3. Polyster Filament yarn

14. Acetone 4. Polyster staple fibre15. Butanol 5. Acrylic Fibre

6. Polypropylene fibre Synthetic Fibres:1. Caprolactum

Synthetic Rub:1. Styrene Butadienerubber

2. Dimethyl Terepht- 2. Poly Butadiene Rubberhalate (DMT)/Terephthalic

•= acid (TPA)3. Acrylonitrile

L.

CHAPTER II

STATUS OF PETROCHEMICAL INDUSTRYIN INDIA

STATUS OF PETROCHEMICAL INDUSTRY IN INDIA

Petrochemical industries in India is developing fast. It is predicted that in next ten to fifteen years overallpetrochemicals growth would average 8 to 10% per annum for developed countries like U.S.A., Europeancountries etc. and much larger growth for developing countries like India. The growth of petrochemicalindustry, however, depends on many factors like crude refining capacity, quantum of naphtha available,policy and programme of Government, availability of technical knowhow, financial allocations etc. Thefirst naphtha cracker unit (olefine plant) of M/s Union Carbide of India Limited (UCIL) went into produc-tion in Bombay by the end of 1966. M/s National Organic Chemical Industries Limited (NOCIL) at Thanenear Bombay went into production in 1968. The third and at present the largest enterprise, IndianPetrochemical Corporation Limited (IPCL), Baroda based on naphtha with the facilities of production, ofprimary, intermediate and downstream petrochemicals was commissioned during 1978-79. Based on theabove primary petrochemical units, there was substantial growth of industries for producing petrochemi-cal intermediates and final products.

PRESENT STATUS OF PETROCHEMICAL INDUSTRY

A list of the operating petrochemical units is furnished in Table 2.1 It may be observed from the Table 2.1that the western part of the country accounts for the maximum number of units.

TABLE 2.1 : List of Petrochemical Industries in India

5. No N ame of the Industry Location of the Industry1. Assam Petrochemicals Ltd.2. Bongaingaon Refineries and3. Petrochemicals limited4. Durgapur chemicals

Dyeing Plastic Resinsand Chemicals

5. Gujarat State Fertilisers Co. Ltd.6. Gujarat Refineries Limited7. Herdillia Chemicals Limited8. Indian Petrochemical Corpo-

ration Limited9. Mysore petrochemicals10. National Organic Chemical Ind-

ustries Limited11. Reliance Corporation

12. Snurid Geigy13. Steel Authority of India Limited

FETURE OF PETROCHEMICAL INDUSTRY

The demand and supply of gas upto 1987-88 drawn by the Ministry of Petroleum and Natural gas ispresented in Table 2.2. The table shows continued short supply of intermediates and products.

The report of the working group on petrochemical industry constituted, by Ministry of Petroleum andnatural as indicates that future development in this field will also take place in Gujarat and Maharashtra.

Namrup, AssamBongaingaon, Assam

Durgapur, West Bengal (1968)Tuticorin, TN (1972)

Vadodara, Gujarat (1967)Vadodara (1968)Thane, Bombay,. Maharashtra -(1968)Vadodara, Gujarat (1977)

Raichur, Karnataka (1971)Thane, Bombay (1968)

Patalganga, Rasayani,Maharashtra.Vadodara, GujaratRaurkela, Durgapur, Bhilai

14. Synthetics and chemicalsand Bokaro.

15. The Sir Silk Limited Bareilly, U.P. (1966)Sirpur Khagaz Nagar, A.P.16. Tnirumalai Chemicals _

17. Union Carbide India LimitedChembur, Bombay (1966)

N

This is attributed to the fact that the future availability of petrochemical feedstocks particularly olefins andits downstream units are concentrated in and around the westen part of the country. This may cause in-crease in the concentration of hydrocarbon processing units in Gujarat and Maharashtra which may af-fect the environment of that area. Therefore, measures for protection of environment are necessary fromthe planning stage.

Table 2.2 : Demand, Supply and Deficit

S.NO.

Item Demand82-83 87-88

Supply82-83 87-88 82-83

Deficits87-88

PRIMARY

1.

INTERMEDIATES

Ethylene 334 633 193 242 141 3912. Propylene 147 247 108 135 39 1123. Butadiene 47 104 49 56 -2 484. Benzene 265 441 125 125 140 3165. o-Xylene 52 91 23 24.5 28.6 66.56. p -Xylene 88-119 123-162 31 38 57-58 85-12

SECONDARY INTERMEDIATES

1. Ethylene Oxide 62-76 89-106 25 35 37-51 54-712. Ethylene Glycols 59-76 80-102 22 31 37-54 49-713. Isopropyl Alcohol 3 8 1.4 1.4 1.6 6.64. 2-Ethyl Hexanol 32.4 67 10.5 29.5 21.9 37.55. Acetone 35 56 19 19 16 376. Phthalic Anydride 39.67 70.89 31.5 33.5 8.2 37.47. Phenol 34.5 56.0 13.5 22.5 21.0 33.58. Caprolactum 69.0 125 18.5 18.5 50.5 10.609. Acrylonitrile 25 34 22 22 3 12

10. DMT 131-178 184-241 48 58.5 83-100 125.1811. Maleic Anhydride 7 12 5.4 5.4 1.6 6.612. Detergent Alkylate 67 108 27 27 40 81

10

CHAPTER III

MANUFACTURING PROCESS

11

MANUFACTURING PROCESS•

UNIT PROCESSES

Cracking and reformation are two main unit operations Involved in the manufacture of petrochemicals.

Cracking

- cracking a hydrocarbon molecule Is fractured or broken into two or more smaller fragments. There arethree principal types of cracking : thermal craking, catalytic cracking and hydrocracking.

Thermal cracking for fuel production is performed by subjecting a feedstock to temperatures usually inexcess of 4550 C and at above atmospheric pressures with the objective of converting a residual crudefraction or a heavy distillate Into gasoline and light distillates.

Catalytic cracking is performed in presence of a catalyst at temperature between 4550-5400 C and atsightly above atmospheric pressure. The process converts a distillate feedstock into gasoline as theprimary product with production of light hydrocarbons.

Hydrocracking process operates at elevated pressure In the presence of hydrogen and catalyst attemperatures generally less than 432° C.

Reforming

The purpose of reforming .naphtha is to rearrange or reform the molecular structure of hydrocarbons ; par-ticularly with the objective of producing aromatics. The chemical processes Involved in reformation areas follows :

- Dehydrogenation of naphthenes to aromatics

- Dehydrocyclisation of paraffins to form aromatics

- s omerisation of paraffins to more highly branched isomers

- Fine reaction proceeds the reformed products will contain increasing concentration of aromatics anddecreasing concentrations of heavy paraffins. These reforming reactions are regulated by metal catalystsin an eivironment of hydrogen under moderate pressure.

CHEMISTRY OF MANUFACTURE

The chemistry involves in the manufacturing of Important primary and intermediate products - aredescribed below:

Ethylene and Propylene

Ethane 'Is converted during cracking Into various hydrocarbon fractions under vapour phase, low pres-sure and high temperature. The gas streams from the furnace are cooled, compressed and sent to frac-tureing columns where each fraction is separately recovered. The ethylene/ethane mixture is purifiedin the ethylene.

The propylene stream is recovered in the third stage. It is hydrogenated and dehydrated to yield purepropylene

13

Heavier hydrocarbon fractions, containing Increasing number of carbon atoms, are recovered in succes-sive stages and serve as feedstock for down-steam plants.

The typical cracking reaction is as follows :

C 2 H 6 C2H4 + H2

Ethane Ethylene HydrogenThe process flow sheet is given in Figure 3.1.

3.2.2 Butadiene

The mixed butane/butene fraction from ethylene unit containing four carbon atoms is purified In the firststage by means of extractive distillation with solvent to remove lighter components. In the second stage,butadiene is separated from heavier components in a tailing column.

Ethylene Oxide

Ethylene Oxide (EO) is produced by the direct oxidation of ethylene-with oxygen. Ethylene and oxygenare combined with recycle gas and changed to a reactor. The EO fraction from the reactor effluent isrecovered by absorption in water. Later, it is-stripped from the absorbent, distilled for removal of lightends and water and purified top product recovered :

H2 C = CH2 + 1/2 02 ---' C2 H4 0

Ethylene Ethylene O x i ccEthylene Glycol

A side stream at EO is sent to glycol reactor where it Is hydrated to glycols. The reactor product is precon-centrated, dehydrated and purified in two stages to recover monoethylene glycol (F.1eG) and Diethyleneglycol (DeG) :

H 2 C — C H 2 + H 2 0 --- , OHH 2 C -- CH 2 OH\ 0^

Ethylene Oxide (EO) MeG

EO + MeG ----> D e G (OHH2C — CH2- 0 — CH2 CH20H )

3.2.5 Ethylene dichloride (EDC) Vinyl Chloride Monomer (VCM)

EDC is an intermediate product in the process of manufacture of VCM by chlorination - oxychlorinationroute. In actual industrial practice EDC production is a part of VCM manufacturing facility.

VCM manufacturing processes are of four types :

- Hydrochlorination of acetylene

- Direct chlorination of ethylene and dehydrochlorination

- Chlorination-oxychlorination of ethylene (using air) and dehydrochiorination

- Chlorination-oxychlorination of ethylene (using oxygen) and dehydrochiorination.

3.2.3

3.2.4

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The processes (iii) and (iv) are more or less the same and known commonly as balanced oxychlorina-tion process. Process (iv) is a modified balanced oxychlorination process wherein oxygen instead of airis used to oxidise the hydrogen chloride to chlorine. The advent of balanced oxychlorination process hasmade a major reduction In waste generation problem in VCM production.

As mentioned earlier, EDC is an intermediate product in the manufacture of VCM. It may be manufac-tured by two processes viz (a) direct chlorination of ethylene to form EDC and (b) oxychlorination ofethylene to form EDC. The EDC thus produced by these two different routes is purified anddehydrochiorinated (cracked) to yield VCM. Hydrochloric acid (HCI ) produced during cracking is usedfor oxychlorination of ethylene to EDC. The chemical reactions are

C2 H4 + C12 :0 C2H4C12 (CIH2C - CH2 Cl )Ethylene Chlorine EDCC

CIH2C - CH Cl Washing

H 2 C CHCI + HCL

EDC VCMThe process flow diagram Is given in Fig. 3.2.

3.2.6 Solvents

lsopropyl alcohol (IPA)

This is produced by reacting propylene with sulfuric acid in the liquid phase in a vertical reactor underpressure followed by hydrolysis, stripping and purification in distillation columns:

H 3 C— CH = CH2+ H2H2SO CH3CHOHCH3

Propylene

Diacetone alcohol (DAA)

DAA is prepared by orientation of acetone molecule in presence of atcholic caustic. In OM preparationtemperature control is important. At high temperature, reaction is faster while conversion is less. At lowtemperature, the situation is reverse. Therefore, temperature is required to be brought down from onereactor to other and crude OM formed in the process is purified by distillation in a two-column opera-tion. The reactions are as follows: 3H

Alcoholic CLiUSiC

2H3C— C—CH3 .. H3C— C —C H3Ii I0 1­12C— C — CH3

Acetone Ii

The process flow diagram Is given In Fig. 3.3. L -

Normal Butyl Alcohol (NBA) I [so Butyt Alcohol (IBA) and 2 Ethyl Hexanol (2E HA)

By reacting steam with hydrocarbons (Naphtha) synthetic gas (CO + H2) is produced in a reformer. Thisis reacted with propylene from ethylene unit in presence of catalysts to form crude alcohols consistingof NBA, IBA and 2EHA.

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Chemical reactions are as under:

C —CH =CH 2 +CO+H 2 -- ----- CH 3 CH 2 CH2 CHOPropylene Synthesis gas Butyldehyde

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3.2.7 Acrylonitrile

The process routes for manufacture of acrylonitrile

- Propylene ammoxidationvapour phase oxidation with ammonia and air

- propane ammoxidationvapour phase oxidation with ammonia and air

- propylene cyanisationvapourphase oxidation with nitric acid.

Propylene ammoxidation is generally the most popul process route commonlyknown as Sohio process.The only existing unit in the country (IPCL) is based n Sohio process:

C11 3 CH = CH 2 + NH3 + 1 1120^ ---}.H2 C _ CHCN + 3H 02The reaction takes place between 4800 . 5380 C and at atmospheric pressure with propylene : NH3 : 02feed ratios of about 1:1:5. During acrylonitrile manufacture by propylene ammoxidation process, sig-nificant quantities of acetonitrile and hydrogen cyanide are produced as by-products. (Fig.3.5).

3.2.8 AromaticsBenzene/Toluene/Xylene (BTX) and their intermediates

In petrochemical industries, the pyrolysis of gasoline obtained as a by-product of ethylene production, isprocessed to yield a mixture of BTX aromatics. Generally, for separation of the components of BTX, ex-tractive distillation, azeotropic distillation, solvent extraction and selective adsorption are adopted.

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The separation of BTX from pyrolysis of gasoline or naphthene rich petroleum feedstock is carried outadopting following processes :

a) Hydrotreatingb) Solvent extraction

Hydrotreating is carried out by hydrogenation In presence of catalyst. The light hydrocarbon thusproduced is extracted by solvent.

The dissolved BTX are separated from the solvent in a stripper and further distilled to separate individualcomponents benzene, toluene and xylene. The solvent from the stripper bottom is regenerated andrecycled to the process. The sludge separated at the regeneration column bottom is a waste stream. (Fig.3.6).

3.2.9 Cumene and PhenolCumene is an intermediate product for production of phenol from propylene. Phenol is produced bycumene peroxidation process. Cumene is peroxidised to cumene hydroperoxide which inturn is decom-posed to phenol and acetone by the action of acid.

The excess acid is neutralised and separated in decanter. The washed product is further fractionated toseparate acetone In acetone column. The overhead from the top of acetone column is distilled to obtainpure acetone. The bottom from the acetone column Is subjected to distillation in heavy end column whereheavy ends are separated. The overhead from heavy end column containing phenol is fractionated incumene column to separate cumene. The bottom of the cumene column is further distilled to obtainphenol.

CCHG + CH3 CH2=CH2 C6H5 CH CH3CH + 02

H nzene Propylene Curnene

H3000H3t C6 HSOH CGHSCOOH CIt3 CH3 F

0Acetone Phenol Cumene Hydrogen Peroxide

(C HP)

3.2.10 CaprolactumRaw material for manufacturing caprolactum maybe benzene, cyclohexane, toluene or phenol. In India,benzene being easily available and cheaper, benzene - based process Is followed (Fig.3.7). The onlyoperating of caprolactum unit in the country is based on the benzene. Benzene based process involvesthe following steps:

a) Hydrogenation of benzene to cyclohexane

CH + 3H 2 C6Ht2

Benzene Cyclohexane

b) Oxidation of cyclohexane to cyclohexanone

C6 i 12 ---} C6 H10 0 + C 5 I1 OH + Other ProductsCyclohexanone Cyclohexanal

C F it OH C6 Htn 0 + H 2Ana I Anone

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24

c) Cyclohexane distillation

d) Production of hydroxylamine sulfate

4 NH3 + 502 )-- G NO + 6 H2O

2N0+02 ^--- 2NO2

NO + NO2 + (NH4) 2 CO3 .2 NHG NC2 + CO2

NH 4 NO2 + 2S0 2 + N H4 0H -- > HO - N -- (503 N H4) 2Hydroxytamine disu(phatc

2 HO- N -(503 NH4)2 + 4)42O ----> (NH 4 OH)2 H2SO4+(2NH4) 2 504

Hydroxylamine sulphate

e) Oximation of cyclohexanone

2C H 0 + (NH 0H +HSO NH3 t i C6H N'OH + (NH a SO + 02H6 1Q 2 ^ H2 SO tQ 4 2 L 2

Oximet) Rearrangement of cyclohexanone oxime with oleum to produce caprolactum

H10 N . OH ------- >H2O (CH 2 )G C 0 Ní03 H.Oxime sulDhate

• (CH 2 )4 • CO.N. S03 H + 2 NH 4 0H -----' H2C (CH2)^, CON H+(NH4)2504Caprolactum

: 2.11 Linear Alkyl Benzene - (LAB)

Linear alkyl benzene (LAB) is one of the basic Ingradients for synthetic detergent Industry. The processfor making LAB from kerosene and benzene consists of five distinct sections :

a. Prefractionationb. Hydrobonc. Molexd. Pacole. Alkylation.

Kerosene is prefractionated to obtain C10-C14 range hydrocarbons. The purpose of Hydrobon unit is toremove sulphur compounds from the kerosene. The purpose of the Molex unit is to remove the n- paraf-fins from kerosene by selective absorption process. In the Pacol unit, the normal paraffins are convertedto clefins by dehydrogenation process. The Pacol stripper bottom, fresh benzene, recycle streams con-taining benzene and HF are mixed and fed to alkylation reactor. The alkylated benzene is fractionatedat the benzene column to separate excess benzene which is recycled to alkylation reactor.

C G H 6 + CH3 CH HF

C6H5 CH 3 CH2

The bottom product of the benzene column is further distilled in the paraffin column to separate paraffinat the top. The bottom product from the paraffin column is further distilled to obtain LAB (Fig. 3.8)

25

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Phthalic Anhydride (PAN)

Fhthalic anhydride (PAN) is produced by gas phase oxidation of naphthalene or ortho-xylene in presenceof catalyst (Fig.3.9).

Oxygen in air is the oxidising medium:

C 6 H4(CH 3 )2 + 302 V205 C6 H4(CO2 )0 + 3112 0

Ortho Xylene PAN

The process involves preheating of O-xylene and air before feeding to the reactor where gas phase oxida-tion of orthoxylene to PAN takes place.

3 Dimethyl terephthalate (DMT)

The feedstock for the manufacture of DMT is para-xylene. The process involves catalytic liquid phase airoxidation of p-xylene to yield terepthalic acid (TPA). TPA undergoes process of esterification withmethanol to yield DMT. In one process, TPA is isolated as an intermediate before further processing toDMT. In the other process, p-xylene is converted to DMT without isolating TPA as intermediate.

Cobalt- 4 (C H3)2 NpAceate

C6H4CH3000H + CGH4 (COOH)2 --^ CGH4 (COCH3).2lens Catalyst p tolure acid Terepthalic acid Dimethyltereptha(atc

(DMT)

The product DMT is purified by the process of crystallisation and centrifuging. Two-stages crystallisationis carried out and the recrystalised DMT Is melted and distilled further in the DMT distillation column. PureDMT is recovered at the top of the colum. (Fig. 3.10).

29

CHAPTER IV

WASTEWATER CHARACTERISATION

31^

WASTEWATER CHARACTERISATION

The liquid effluents originate from manufacturing processes and utilities. The Individual waste streamsfrom various sources have a distinct characteristics. The flow, type and concentration of pollutants varywidely depending upon process and water use.

3eneraily, the total volume of wastewater generation per unit petrochemical product varies so widely thatan average value has little importance. In this section, the factors contributing to the variation in waste`low and its characteristics in respect of different sources are analysed to develop a waste profile for theindustry. The development of waste profile involved logical interpretation and analysis of the data avail-able from various publications and the data collected during the survey of operating units.

WATER USE PATTERN

Petrochemical manufacturing facilities consume a large volume of water. The raw water requirementsfor various purposes in a petrochemical industry can be broadly classified as follows :

• Make up for cooling water system• Make up for fire water system• Feed to demineralisation plant• Process water• Service water• Sanitary water

Water usage patterns In a few petrochemical plants are furnished in Table 4.1. It Is Interesting to notethat in almost all the plants, cooling water make up consumption is high ranging from 33 to 56% of totalwater consumption. Feed to DM plant comes next with consumption of 15 to 33%.

Table 4.1 : Water Usage Pattern in Operating Units

Cubic meter per dayNOCIL Herdillia GSFC UCIL IPCL

7 water 4800 690 2000 2223 21400(32.78) (35.57) (55.04) (56.4) (35.91)

L- :: D M 4800 280 840 1080 11200'L (32.78) (14.43) (23.12) (27.4) (18.79)

: =ss water 1200 290 271 271 15,000(8.2) (14.94) (7.46) (7) (25.17)

water 2400 300 523 250 7,000(16.39) (15.46) (14.39) (6.3) (11.74)L - 'water 1440 380 120 5,000(9.84) (19.58) (2.9) (8.39)

r - 14640 1940 3634 3944 59600100) (100) (100) (100) (100)

1 ":: Figures in bracket denote per cent consumption

33

4.3 WASTEWATER GENERATION

The principal wastewater streams are:

• Cooling tower blowdown• DM plant regeneration wastewater and boiler blowdown• Process wastewater• Service water and storm water• Sanitary wastewater

4.4 MASS BALANCE

Mass balance of water consumption and wastewater generation, worked out for a petrochemical com-plex comprising olefinic, EO, EG, PVC, Solvent plants is shown In Fig. 4.1

4.5 WASTEWATER FROM UTILITIES SECTION

The sources of wastewater generation from different petrochemical complexes are furnished in Table 4.2It may be seen from Table 4.2 that cooling tower blowdown amounts to significant quantity with respectto the total wastewater generation. One Industry has adopted higher concentration factor (CF) for thecirculating cooling water. This system substantially reduced water consumption for make up and blowdown of cooling water.

Table 4.2: Wastewater Generation

Cubic meter per hourS. Petrochemi- Phenol Caprolactum Large Petroche-No. cals complex cumene plant mica] complex

plant

1. Cooling water 50 * 17 11200blowdown

2. DM plant regen- 50 3 - t400eration wastewater

3. Process waste 110 12 11 14000water

4. Servicewaste 90 13 22 (see note2)water

5. Sanitary waste 40 8 - 2500water

TOTAL: 340 36 50 29100

* Industry claims Insignificant blowdown

NOTE: 1. Data were collected during study except for the Olefinic plant.Data for olefinic plant Is taken from literature.

2. Service waste water quantity Is Included In the process waste water

Other than the cooling tower blowdown, wastewater generates from the following utilities sections:

• DM plant regeneration wastewater

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35

Boiler House blowdownSanitary wastewater

Another source of wastewater to the storm water drains where significant quantity of contaminated stormwater flows during rains and floor washings.

4.5.1 Characterisation of wastes of utilities section

Cooling water blowdownThe typical characteristics of cooling water blowdown Is presented in Table 4.3. The blowdown usuallycontains :

Table 4.3 : Typical Analysis of Cooling Tower Blowdown

S.No. Parameter Range of wet datafrom a petrochemicalcomplex

1. pH 6.5-7.52. Total suspended 20 - 50

solids (TSS)3. Biochemical 10 - 20

oxygen demand(BODs), 200C

4. Chemical oxygen 60 - 70demand (COD)

5. Oil and Grease present6. Sulphides as S present7. Hexavalent Chromium as Cr 4- 15 8. Total phosphates as P 5 - 159. Total dissolved solids 900 - 150010. Dissolved organic carbon presentif Zinc asZn 3-7

Note : Results expressed as mg/i except pH.

Cooling tower additives used for conditioning,Contamination with process fluid due to leaks.

The data show that cooling tower blowdown water requires treatment for removal of chromates, ifchromate based inhibitors are used as conditioning chemical. It may require additional treatment in caseblowdown water is contaminated with process leaks.

DM water plant

During regeneration of DM plant, wastewater generates which contains high total dissolved solid.

Boiler Blowdown

The boiler blowdown water has high pH, alkalinity and total dissolved solid (IDS).

Storm water

Petrochemical plants generally occupy a very large area. The sources of contaminated storm water are:

• Tank areas including unloading and loading facilities for raw materials, intermediates and finished

36

products• Paved process area• Spillage and leakage from the plants• Washings

The waters of the storm water drains attached to indivldtial plants of a petrochemical complex wereanalysed and the data presented In the Table 4.4. The combined waters of the storm water drains ofanother petrochemical complex were analysed and data presented InTable4.5. The data show significantpollution of the waters of storm water drains. This may be due to leakage, spillage and washings.

Table 4.4 : Plantwise Storm Water Characteristics

S. mg/INo. Plant pH COD CN F

1. Polymer 7.5-8.0 40-100 NA NA2. Acrylonitrile 8.2-10.1 28-600 2.8-7.8 -3. Acrylic Fibre 5.0-10.5 30-626 - -4. Linear Alkyl Benzene 8.2-9.8 10-480 - 2.4-6.25. Olefin 5.2-7.4 60-2550 - -6. Dimethyl Terephthalate 7.2-7.6 20-1140 - -7. Xylene 6.8-7.2 10-170 - -

Table 4.5 : Storm Water Characteristic of a Petrochemical Complex

concentrationS.No. Parameters Unit Min Max Ave1. Flow m3/d - - 2002. pH unit 1.8 11.5 -3. Suspended Solid mg/I 70 342 524. BOD mg/I 12 115 485. COD mg/I 30 330 1206. Oil & Grease mgp 2 40 127. Hexavalent mg/I 0.1 2.7 0.1

Chromium as Cr8. Total organic carbon mg/I 10 110 60

In one of the petrochemical complexes, the waters of the storm water drains are collected separately andtreated in the effluent treatment plant meant for the treatment of process wastewaters. The other unitsdo not practice treatment of the waters of the storm water drains. The contaminated storm water is dis-posed of without treatment. This practice should be avoided and contaminated storm water should besegregated from other wastewaters and rendered appropriate treatment before disposal.

PROCESS WASTEWATER CHARACTERISATION

The process wastewater may be classified as follows:• Process effluents• Leakage, drainages and unforeseen discharges from process equipment

Process wastewaters include scrubbing water from scrubbers, wastewater from strippers, quench waterfrom barometric condensers, water separators of the overhead drums of distillation coloums etc. General-ly, these streams contain raw material, intermediate products and chemicals present In the process. Thequanitity and quality of wastewaters generally depend on the process technology, the design of the

37

petrochemical unit and the water usage pattern. The wastewater data based on the type of plant andproduct are presented In Tables 4.6 and 4.7 respectively. The wastewater pattern during the unit opera-tions are given in Table 4.8.

Table 4.6: Plantwise Process Waste Profile

S. Name Unit Olefin- PAN Ethylene Solvent Alcohol Phenol- Capro- DMT Linear Acrylo- PVC/ BTX Butadiene

No. of the ic Plant oxide/ Plant Plant cumene lactum plant alkyl nitrite VCM

stream Plant Ethylene plant Benzene

glycols

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1. pH 12.1- 3.0-3.9 7.0-8.0 0.7-11.8 6.8-10.5 9.6 6.0-7.0 2.4 5.2 7.9-8.5 2.0-12.0 6.0-8.0 -

12.92. BCD mg/I 350- 3500- 1860- 460- 155 66.25 200- 12000 - 33760- 28-180 1000- 300-400

850 5000 3235 3500 3400 34665 1500

3. COD mg/l 850. 22800 3835- 480- 575- 9600 3200- 20800 530 42200- 61-670 2000- 750-950

4275 44400 6250 2080 9600 42595 3000

4. Suspen- mg/I 220- - 15-215 25-65 145- 30-125 1230 - - - 35-380 50-100 -

ded solid 670 785 _5. Fluoride mg/i - - - - - - - 22002 - -

as F6. Nitrate mg/I - - - - - - 1595 - • - - - -

Nitrogenas N

7. Phenol mg/ 19-30 - 0.25- 0.72- 0.13-1.0 410 - - - -0.8 0.75

8. Cyanide mg/I - - - - - - - - 34-42 -as CN

9. Sulphidemg/l 43-46 - 1-25 10-120 0.4-0.6 • - - - - -as S

10. Total mg/I 300- - 1185- 180- 205-770 - - - - - - -organic 1440 16300 1915carbon

11. Cl and mg/I 150-356 - 5-81 10-20 39-79 76-346 797 - - -Grease

Table 4.7 : Productwise Wastewater Characteristics

S. Product Flow M3/MT BOD mg/ COD mg/I Other Pollutants

No. Low High Low High Low High

A.1.

Primary Intermediate0.19 0.68 100 1000 500 3000 Phenol, oil, spent caustic

Ethylene2. Propylene 0.37 7.44 100 1000 500 3000 Phenol, oil, spent caustic

3. Butadiene 0.37 7.44 25 200 100 400 Oil, Hydrocarbons, solvent

4. Toluene 1.12 11.16 300 2500 1000 5000 Oil, hydrocarbons

5. Xylene 0.75 11.16 '500 - 1000 8000 Oil, hydrocarbons

B.6.

Secondary Intermediate1.86 9.30 1200 10000 2000 -

7000

Phenol, heavy endsCatalyst, oil, aromatic hydrocarbonsCumene/phenol

7. Ethyl Benzene 1.20 10.2037.2

500300

30003000

10001000 6000 Tars, heavy ends

8.9.

StyreneAcetone

3.721.86 5.58 1000 5000 2000 10000 Phenol, heavy ends

10. Glycerine Glycol 3.72 18.60 500 3500 1000 7000 Organic acid, aldehydeOIl & heavy chlorinated Hydrocarbons

II Acetic Anhydride 3.72 29.76 300 5000 5002000

80004000 Alcohols, vaster, heavy chlorinated, metal

12. Terephthalic acid 3.72 11.16 1000 3000150 100 500 Oil, heavy chlorinated hydrocarbon

13. Ethylene dichloride 0.19 3.72 50200 2000 500 5000 Heavyends, chlorinated hydrocarbon

14. Vinyl Chloride 0.09 0.7837.20 200 700 500 1600 Colour, Organics, Cyanides

15. Acrylonitrile 3.723.72 11.16 500 5000 2000 15000 Colour, Odour, Solids, Cyanides

16. Acrylates

C.17.

PolyD-eLPolyethylene 1.50 6.00 - 200- 4000 Solid, catalyst-

18. Polypropylene 1.50 6.00 - --

2001000

440003000 Solid

19. Polystyrene 1.90 3.75 -- 1000 2000 Vinylchlorlde, caustic

20. Polyvinyl Chloride (PVC) 5.60 11.20 -- 2500 5000 Oil, Ught Hydrocarbons

21. Butyl Rubber 7.44 22.50 -- 1000 5000 Acetic Anhydride , Acetic Acid

22. Cellulose Acetate 0.04 0.75

Quench water Inorganic sulphides,spent caustic mercaptans soluble hydro-

carbons,polymensed produ-duct, spent caustic,phenolic compounds,cyanides residual tars,heavy oils,. coke

Desorber and frac- Dissolved organics,

tionator bottoms ethylene oxide, ethylene

glycols, acetaldehyde,formaldehyde

PyrolysisThermal cracking of Naphthaor Natural gas to produceEthylene

3xidationa) Ethylene oxide by oxida-tion of ethylene

Table 4.8 : Pollutants from Processes

Process

Source

Pollutant

b) Aldehydes, acetone andacids from hydrocarbons

c) Aromatics oxidation toproduce phenol andacetone

d) Aromatics oxidation toproduce acids and aldehy-des e.g. phthalic acid

e) Carbon black manufacture

f) Oxylene oxidation to pro-duce phthalic anhydride

Halogenation(principally chlorination)

Hydrochlorination of Acety-lene to vinyl chloride

HydrocarboxylationButyladehyde productionfrom propylene in processof manufacture 2-EthylalcoholAikylation

a) Alkylation of benzene withpropylene to produce cumene

process slopsduring purification

Decanter and puri-fication columnbottom

Process slops dur-ing separation,purification

cooling, quenching

Stock gas bottom, column

Vents, scrubber,VCM purificationcolumn

Still slops

Reactor and stillbottom

soluble organics viz.acetaldehyde, formalde-hyde, acetomethanol,higher alcohols, organicacid

Cumene, phenol, formicacid

Solvent, catalyst andhydrocarbons

Carbon black, particulatesdissolved solids

Phthalic and maleicAnhydride, benzonic acids

Vinyl chloride, hydrogenchloride, heavy chlori-nated hydrocarbons

Alenhydes, butanol,soluble hydrocarbons

Phosphoric acid,polyalkyl benzene

R9

Table 4.8 Con

S. Product Source PollutantsNo.

b) Alkylation of benzen with Column bottom, wash Benzene, AlUminiumethylene to produce ethy bleed chloride/hydroxide,benzene caustic, ethyl benzene

polyethyl benzene

c) Alkylation of benzene with Column b |om hvdrofVPdnaoid,olefins to produce LAB benzene, long chained

hydrocarbons, heavyalkylate

_Butadiene by Dehydrogena Column bottoms, Heavy ends and tars,tion of butane condensates ethylbenzene

Water stripper, Solvent, hydrocarbonssolvent separation oils.

7Hydrogenation of benzene Vent streams Hydrogen, benzenecyclohexane

8.Propylene ammoxidation to Stripper dacanter Ovonideo,annlóni-

9.a) Polyethylene Catalyst Chromium, Nickel,

Cobalt, Molybdenumb) B utyl Rubber Process wastes Scrapbutyl, oil

Ughthvdroomrbonc) Copolymer rubber Process wastes Butudigna, styrene,

oottnér s|udQed) Nylon Process wastes Cylohexane, oxidation

productn, succinicao|d, adipic acid,glutaric acid, hexamethylene diamines,adiponitrile, acetone

10.Butadiehe recovery from by Solvent recovery Solvent,spent causticproduct mixed e.g. hydro caustic, acid wash spent acidcarbons, stream from naphthacracker

40

Contd. _ :e .sal of theTables4.6, 4.7 and 48 it reveals that significant amount of organic wastes are produced :`:e production of petrochemicals. In addition some specific pollutants like phenols, cyanides and

s etc. come from the specific plants. The other common pollutants are suspended solids and oil- ease. The main sources of organic wastes originate during the production of unsaturated hydrovar-

. _ - ^-'efins). Whereas, during chlorination,,ammoxidation, aikylation processes, toxic pollutants like_ - - e, cyanides, benzene etc. generate. These toxic wastes require segregation and separate treat-

_ before taking into common biological treatment unit.

caustic

- sulphur present in the naphtha and that added in the form of dimethyl disulphide to avoid choking:- coke formation in the super heaters in scrubbed with caustic soda (NaOH) solution. The sulphur

-acted to form sodium sulphide (Na2S). The blowdown from scrubbers contains very high .concentra--7, of sodium sulphide and cannot be discharged as such because of very high levels of COD and sul-

- des. The characteristics of spent caustic solution is presented in Table 4.9.

Table 4.9 : Characterisation of Spent Caustic Waste

Parameter UnitConcentrationMin Max Ave

pH 11 13.4 12Suspended Solid mg/I 130 412 273Oil & Grease mg/I 30 570 328COD mg/I 1600 6400 4504Sodium Sulphide mg/I 1900 6300 3500

-2akages

_=akages from pumps, valves, flanges, pipings etc. are significant sources of pollution. These was-.:vaters generally flow to the storm water drain and should be managed alongwith the storm water (Sec-_n 4.5.1).

: -ainage of process equipment and vessels

-a quality of the effluent from the equipment and vessel draining sources are similar to the process ef-:ent. However, the quantity, quality and frequency of generation are variable. The flow and con-

'srninants may vary widely depending upon the factors like age and operation/maintenance practice of- e plant. Segregation and collection of the above wastes based on the characteristics are practised in.me of the petrochemical units.

41

CHAPTER V

TREATMENT STATUS

43

TREATMENT STATUS

= ATMENT PHILOSOPHYis considerable variation in the nature of pollutants normally generated In a petrochemical com-

yL Sefore designing treatment system the following aspects should be looked into:

Segregation of waste waters based on type and strengthRuction of quantity and strength of waste waters by adopting In-process and In-plant controlmeasuresTreatability studies of various waste waters to decide the best combination of treatment system.

Segregation

s now a standard practice to segregate the various waste streams generated from the petrochemical_ ants. The strong process and oily wastes can be separated from the weak wastewaters.' Factory

cooling water blowdown and storm waters also need segregation. By adopting Judicious ap-„. roach of segregation the size of the treatment plant units can be substantially reduced which results inc: erall economy. During the indepth study, it was observed that one of the petrochemical complexesras a sewerage network laid on the basis of the above concept. The sewerage system comprises of thefollowing:

• Chemical sewer• Storm water sewer• Oily sewer

The breakup of hydraulic load in this plant Is furnished in Table 5.1.

Table 5.1 : Break-up of Hydraulic Load

S. SewerNo.

Source Quantity Sub TotalM3/hr M3/hr

1. Chemical Olefins 10and sanitary EO/EG 5sewers Solvents 25

Alcohols 5PVC 5Sanitary 40

2. Storm water sewer Cooling water Blowdown- 50Boiler blowdown 50DM regeneration 10Service water 90

3. Oily sewer Olefin 15Alcohol 5

In another approach, different types of effluents are collected separately and treated in the inside batterylimit (ISBL) of plant for reduction of specific toxic components of the individual streams and thentransported through a common sewer.

90

200

20310

45

5.1.2 Reduction of Quality and strength of wastes

Inplant reduction of quantity and strength of wastewaters Is an ideal approach for control of pollution. InTable 5.2, some inplant control measures and recovery systems for reduction of pollutant discharges Ispresented.

5.1.3 Resource recovery

Utilisation of Tar

The disposal of tar obtained from the phenolic cracker by burning in open pits is a common phenomenon.The quantity of tar in one plant is between 3 and 4 MT/day. Burning of tar in open would cause air pollu-tion. It was observed in an unit, tar was blended with alphamethyl styrenes (AMS) and cumene bottoms.The blend was used as a fuel alongwith furnace oil in boilers and furnaces. The blend constitutes about20% of the fuel oil requirement for the factory effecting an annual saving of five million rupees.

Recovery of fumeric acid from off-gas of phthalic anyhydride plant

In the manufacture of phthalic anhydride, a small quantity (5.6%) of maleic anhydride Is inevitably formedwhich is released to the atmosphere alongwith the off gas causing air pollution problems. It would causewater pollution if scrubbed with water. Instead a process has been developed for the recovery of pure

Table 5.2: In-plant Control Measures and Recovery System

S. Plant Source In-plant controlNo. measures and recovery

1. Ethylene/propylene Spent caustic(Naptha cracker) stream

2. Ethylenedichloroide/ High ends/HeavyVinylchloride Monomer ends vent scrubb- incinerator

er pit to removeHCI and Hydrocar-bon

3. Dimethyl terephtha- Condensate effluent Methanol recoverylate

4. Phthalic analydride5. Phenol-Cumene

system

6. Styrene

7. Caprolactum

offgasa) cumene bottom

b) Clevage product

Transalkylator bottom

Cyclohexane fromcyclohexane-Saponifi-cation organic waste,its salts and ester

Recovery of fumeric acida) Recovery of cumene byTransalkyllationb) Upgradation of wasteproduct Alpha-MethylstyreneRemoval of AI(OH)3

a) Incineration

b) synthetic oil recovery

8. 2-Ethyl Hexanol Aldoling section Catalyst recovery9. Ethyeneoxide/ Barometric Conden- Condensate from evaporat-

Ethylene glycol sers ion system recycle10. Acrylonitrile Cyanide waste from a) Incineration

acrylonitrile b) Biological treatment11. Butadiene Solvent recovery Cuprous.ammonium sulphate

column12. Detergent alkylate (LAB) Hydrofluoric acid Calcium flouride

46

umeric acid from maleic acid. It Is achieved by use of suitable catalyst and optimisation of the processconditions, suitable for obtaining fumeric acid. The cost of the plant Is estimated to be fifteen millionrupees, for a capacity to produce 360 MT/year of fumeric acid worth about five million rupees.

Recovery of cumene

In the process of manufacturing of phenol, the first stage intermediate product Is cumene (obtained bythe reaction of benzene with propylene). The side reaction produced di-isopropyl benzene which isseparated, alongwith other impurities In the cumene column as the bottom waste material. This is usual-ly burnt. A process is available through which di-isopropyl benzene could be converted back to cumeneby reacting with benzene using suitable catalyst. The process Is termed as Transalkylation. The cumeneso obtained had to be purified by giving washes and finally rendering double stage distillation. The capi-tal cost of the recovery plant is about seven million rupees for recovery of 800 MT/year cumene worthabout ten million rupees. This approach results in both economic gain -and pollution control.

Upgradation of waste product

Alpha Methyl Styrene (AMS) is another side product which Is formed during the manufacture of phenolfrom cumene. It is obtained as 80-85% purity product from phenol plant. AMS is a very useful chemicalif obtained in higher purity state.

Due to sub-standard purity product, It Is burnt as fuel. Pure quality AMS is used in the manufacture ofspecialised resins (like ABS), plasticisers, SBR latex and binders. With an Investment of around four mil-lion rupees an unit is reported to earn about six million rupees per year from the sales of pure qualityAMS.

TREATMENT OF WASTES

Incineration

Wastes that are concentrated or too toxic for treatment by conventional physical or biological methodsrequire incineration. For example, cyanide wastes from acrylonitrile plant, strong pesticides wastes,methyl acrylates, organic tars (from LAB plant), hydrocarbons from nylon intermediate manufacture, was-tes from vinyl chloride, styrene residue, DMT residue, cyclohexane waste etc. are too toxic to be economi-cally and technologically treated by conventional methods.

Submerged combustion Is also used by petrochemical industry. A patented process called Zimmermannprocess is used for submerged combustion. Many wastes after submerged combustion contain highBOD which may further be biologically treated. Fluidised bed incinerators are economical in operationbut high in capital cost.

All types of incineration/combustion requires auxiliary fuel which may cause air pollution due to sulphurdioxide. Hence depending upon the nature of fuel and relevant regulations, control measures have to bedecided. Ash disposal facility have also to be provided.

Stripping

Stripping is practised for removal of volatile pollutants from wastewaters. As stripping agent stream withor without air, inert gas, natural gas, flue gas etc. are used. Ammonia and hydrogen sulphide are strippedunder high (above 8.3) and low (below 6.0) pH conditions respectively.

Solvent extraction

This method utilises the preferential solubility of petrochemical in solvents than water. The solvents usedfor extraction of these compunds should have density differential greater than 0.02 between solvent andwaste water, high distribution coefficient for waste component being extracted and low volatility resis-

47

tance to degradation due to heat. Equipment used include countercurrrent towers, mixer-settler units,centrifugal extractors etc. For example, phenols are extracted with aliphatic esters, benzene, light oil,tricresyl phosphates etc.

5.2.4 Adsorption

Polluting substances get adsorbed or attached to the surface of solids by electrical or physical or chemi-cal phenomenon, Activated carbon adsorption method Is adopted to remove traces of organics, phenols,nitriles, chlorinated aromatics like benzene hexachlorlde, chlorobenzene, odour etc. However, wastestreams containing large concentrations of organics cannot be economically treated by active carbonadsorption method.

5.2.5 Cyanide removal

The effluents from Acrylonitnile plant contain hydrocyanic acid and organic toxic chemicals. An in-cinerator with a capacity to burn 10MT/HR wastewater, has been installed in an unit. This incinerator con-sumes about 2.0 MT fuel oil per 10 MT of the wastewater as auxiliary fuel.

Alternatively, biological treatment of cyanide waste after dilution may be adopted which also minimisesthe cost of treatment. Such system is operating in an unit. Sewage effluent is used as dilution waster.The performance of the treatment unit is given in Table 5.3. The data show average removal of cyanideis 74%.

Table 5.3: Performance of Cyanide Treatment System

Feed Effluent

Parameter Max Min Ave Max Min Ave

Flow,m3/d 110 50 80 100 50 82pH 11.4 8.3 9.3 9.5 8.0 8.5COD,mg/I 50,000 30,000 33,980 11,000 2,500 6,395BOD,mg/l 27,000 13,000 16,760 5,725 3,690 4,910Cyanide(CN),mg/I 20 10 13 5.8 1.2 3.4MLSS,mg/l 1,760*Food : Microorganism 0.42*Dissolved oxygen, 0.50*

* One observation, mg/i

5.2.6 Fluoride removal

The pyrolysis gasoline stream containing styrene, methyl styrene, indene and methyl indene from naph-tha cracking unit is polymerised to obtain petroleum resin using BF3 as a catalyst. At the end ofpolymonisation BF3 is neutralised with caustic soda (NaOH) to stop the reaction, whereby sodium fluorideis formed. The neutralised effluent containing fluorides is treated with lime slurry and settled in a clarifier.The fluoride sludge is drawn into a super decanter centrifuge where sludge dewatering is effected. Theclear liquid effluent which contains 4-5% sodium hydroxide. and 10-15 mg/I fluoride is taken to theneutralisation tanks of acidic effluent of DM plant. The dried sludge is sent to the solid disposal area. Thesame precipitation technique may be adopted to remove fluoride from the effluents of liner alkyl benzene(LAB) plant.

5.2.7 Sulphide removal from spent caustic

The sulphur present in naphtha and that added in the form of dimethyl disulphide to avoid choking dueto coke formation in the superheater is scrubbed with caustic soda. The scrubber liquor blowdown con-

48

-ins very high concentration of sodium sulphide and cannot be discharged as such because of very highzv els of COD and sulphides.

order to oxidise these sulphides, a chemical oxidation unit is put up by an unit. In this unit, sulphidese converted to sulphate in the presence of air under high pressure and temperature:

2 Nat S + 2 0 2 1- H 2 O Nat S2 03 + 2 Na OH

Na2 S2 03 + 20 2 + 2Na0H >2 Na2504 + H 2 O

-pree reactors operating in series have been provided for oxidation of Na2S. The air is Introduced at theottom through spargers. The required pressure and temperature are maintained in the reactors. Thefluent from the last reactor is passed through a degasser and cooled. The treated effluents are used

: :r neutralisation of acidic effluents of DM plant. The data on performance study of the treatment unit areresented in Table 5.4.

Table 5.4: Performance Data of Sulphide Removal Unit

Feed effluent

$ er Max Min Ave Max Min Ave

26 20 23 26 20 23

pr- - - 12 - - 12

c : _ - ,' I 6,400 1,600 4,500 1,330 1,200 1.260

2,580 780 1,435 60 16 40k - - :e,mg/1

Biotreatment

To reduce dissolved organics, biological methods are economical in most cases, except those pollutantsin waste waters which are toxic to micro organisms. It is, therefore, a prerequisite to eliminate the toxicand undesirable compounds in inside battery limit (ISBL) treatment by adopting appropriate means assated earlier (section 5.1). Biotreatment may be regarded as outside battery limit (OSBL) treatment.

Biodegradability

The important requrement for biotreatment is biodegradable nature of waste. General amenability to5iodegradation of certain classes of petrochemical are given below:

Aliphatic or cyclic aliphatics are easy for biodegradationAromatics are relatively resistant for biodegradationMolecular size of the organic compound is important in biodegradation. Complex molecular struc-ture offers resistance for biodegradation.

'nsoluble or partly soluble compounds in water are also resistant because of the limited contact surface.. .rger the molecule i.e. more the number of carbon atoms (more than five) more resistance is experiencedi degrade. Open chain compounds are easy to biodegrade than cyclic compounds. Structuralsomerism also affects relative biodegradation e.g. primary and secondary alcohols are easily: odegradable but tertiary alcohols are resistant. Alkyl benzene suiphonates (ABS) using propylene asa base, contain tertiary carbon atoms and are resistant and whereas linear alkyl benzenes (LAB) without

49

tertiary carbon atoms are easily biodegradable. Addition or removal of a functional group like hydroxyl,affects relative biodegradability. The group substitution make a compound (benzene for example) easyto degrade whereas a halogen substitution render it resistant. Many organic compounds are complete-ly degradable at a lower concentrations e.g. phenol. This is why bulk concentrations of many petrochemi-cals upset biological stability. Proper and gradual acclimatisation of microorganism to a particular typeof waste water is extremely necessary. It is generally observed that soil micro organisams are betterdegraders than that of the domestic sewage.

Biodegradability and BOD5 20°C value of some petrochemical compounds are provided in Table 5.5.

Table 5.5: BOD Value for Some Pure Organic Compounds In Petrochemical Wastes

Compound BOD5, 20 C (gm/gm)Acid anhydrides

Phthalic Anhydride 0.72-1.26Maleic Anhydride

Alcohols0.4-0.6

Methanol 0.86-1 12,1.24Ethanol 0.73-1.62,1.26n Propanol 0.43-1.50i Propanol 1.29-1.59n Butanol 1.1-1.65Cyclohexanol 0.08Ethylene Glycol 0.16-0.60

Aldehydes and KetonesFormaldehyde 0.43-1.60Acetaldehyde 1.27Furfural 1.20Acetone 0.31-1.63, 1.19Methyl Ethyl Ketone 1.14

EstersEthyl Acetate 0.56-0.86Ethers Diethyl Formate

Halogenated Hydrocarbons1.12

Ethylene Dichloride 0.002Ethylene Chlorohydrin 0.5Chloroform 0.0.008Monochloro Benzene 0.03Benzene -Xylene -Toluene 0-1.23Napthalene 0-1.23

Nitrogen Containing organicsNitrobenzene -Pyridine 0-1.47Ethanol Amine 0.73Diethanol Amine 0.10Aniline 1.49-2.26p-Toluene 1.44-1.63O.Toluidine 0.24-1.43Acrylamide Monomer 0.97Acrylonitrile 0.72

50

- sound

Adiponitrile -

Hexamethylene Amine 1.31poundd A .ids

Formic Acid 0.02-0.27Acetic Acid 0.34-0.83;0.62Propinic Acid 0.36-0.84:0.66Butyric Acid 0.34-0.90;1.16Maleic Acid 0.38-0.63Benzoic Acid 1.34-1.40;1.36Phthalic Acid 0.85-1.44;1.4

Methanenylic Acid 0.89Salicylic Acid 0.97Succinic Acid 0.57Valeric Acid -

Glutaric Acid 0.72= ndsnnolic compounds

Phenol 1.4-1.8,1.66O-Cresol 1.69,1.74m-Cresol 1.70,1.88p-Cresol 1.40,1.761,3,5-Xylenól 0.82

rr: ; cal processes

ie : :.ving biological processes are generally resorted to for petrochemical waste treatment:

Aerobic Processes Anaeroblp processOxidation pond/lagoon/ Anaerobic lagoonstabilization pondAerated lagoon Anaerobic filterOxidation ditchTrickling filter Anaerobic digestorActivated sledge

1.- - .: : processes

-: 'arge activated sludge process is popular, though expensive and requires skilled operation. Ac-1u_ s:udge has many process variations, such as extended aeration, conventional activated sludgeF : _: ep aeration, tapered aeration, two- stage A.S. etc.

! - _ -:ment of waste water from petrochemical industries in activated sludge process needs pretreat-r- - r effective growth of micro-organisms necessary for biodegradation. The optimal wastewater

-. criteria as a feed to the process is illustrated in Table 5.6, on the basis of literature survey and field= .: -. ations.

:a in the Table 5.6 indicate that pretreatment is necessary even after ISBL treatment to ensure op-_:ndition Of feed to bioreactor particularly In respect of oil and grease and pH. Equalisation Is also-4

-:ment and equalisation systems help to ensure optimal waste water criteria and uniform hydraulic- biotreatment. In the front end of pretreatment one of the following physical treatment systems

- cval of oil and grease may be Incorporated:51

• API separator• Parallel or inclined plate separator• Dissolved air floatation.

The above treatment systems may be followed by clarifloccutation particularly for separation ofsuspended solids and residual oil and grease.

Table 5.6 : Typical Wastewater Quality Criteria for Activated Sludge Process

Parameter Concentration Threshold for Requirementas observed biological of pretreatmentin an unit treatment

pH 0.4-13.0 6.5-8.5 YesSulphides,mg/I 25 200 NoPhenols,mg/I 6 500 NoOil & grease,mg/I 114 50 YesHexavalent 0.1 2 Nochromium,mq/I

The following design criteria for bioreactors are generally adopted :

Organic loading 0.1 to 3.0(kg BODS:kg MLVSS)

- BOD removals as function of K x BOD of effluenteffluent concentrationWhere, K = Kinetic coefficient

(biodegradation rate) 0.00028 to 0.006Oxygen requirement 0.4 to 1.8

(kg oxygen/kg BOD)- Sludge yield 0.22 to 0.60

(kg blosludge produced/kg BOD removed)- Mean cell retention time 6 hrs. to 20 days

These criteria are Indicative and will have to be developed based on laboratory/pilot plant studies for theparticular type of waste water. During field visit volatile solids in the reactors for many petrochemicalwaste water treatment plant e.g. ethylene, butadiene, polymers (poly-butadiene, poly-propylene poly-ethylene) ethylene glycol etc. were found to be of the order of 1000-2000 mg/I which are low. Designshould be made to ensure a higher sludge concentration for stable performance. Biosludge settfeabilityin petrochemical waste water treatment plants is usually poor which needs case to case study. Use ofpoly- electrolytes may be examined.

The stage treatment

Some toxic and/or concentrated petrochemical wastewaters are difficult to degrade in a single stage treat-ment unit. Hence, this is done in two stage treatment providing a clarifier after each stage with provisionof settle sludged recycling system after each stage.

Comparative performances of different aerobic processes are presented in Table 5.7.

52

Table 5.7: Comparative Performance of Aerobic Biological Processes

:ct of Process BOD (mg/1)in out % Removal

COD (mg/I) Remarksin Out % Removal

3 4 5 6 7 8 9

:. ated sludge treatment= alic Anhydride, phenol 45.7 6.1 86.7 - - Effluent from Trickling filter,

:ylic acid, Rubber Brush aeration.-nicals, aspirin, phenacetion

_:adiene, Maleic acid 2000 25 98.8 2990 480 84 -'ene, Propylene, Genezene 600 90 85 700 105 85 90% phenol removalhthalene, Butadiene, 500 60 85-90 600 90 80-85 Effluent from Trickling filter

e, nol, Acrylonitrile, Soft succeeded by pH adjustment

enol,Acrylonitrile, Soft Phenol In 65 mg/Ieergent base resins other Phenol removal 99.9%= -naticsifene, propylene, Butadiene 85 10 99 200 75 62.5 Innfluent from Trickling filter

:=-zene, polyethelene, fuel oils effluent Phenol content 0.01 mg/_ -,iic Fibre 2260 118-226 90-95 - - - The Influent contains acrytonitriledimethylamine, dimethyl for-mamide formic acid. as contaminants.

-:one, Phenol, Cresol, DTP 1950 20 99 7980- 5120- 25-40 Extended aeration, high non-biode- -esol dicumyl peroxode 8540 5950 gradable fraction, followed by

stabilisation pond.-;Ilene and propylene 1950 20 99 7980- 5120- 25-40 Extended aeration, high non-biode-. yes, glycols, ethylene 5950 gradable fraction followed by= a-iines,morpholines stabilisation pond.i -king,lsomeristion 1100 55-110 90-95 - - - 90-95 phenol removal:itane, alkylation,zene, toluene, alcohols,_nes, cresylic acid: ding Filter-_ e iol,salicylic acid Rock media.:er chemicals, aspirin 190 58 89.5 - - - Rock media, treats effluent fromrnacetine, phthalic Anhy- 58 34 41.5 - - - above filter and further treated :e. Inactivated sludge. ..ene, Propylene, Butadiene 170 85 50 400 200 50 Plastic media filter followed

:- :ene Polyethylene, and by activated sludge, phenoloil removal 95%

: - ,:ene, propylene, Buta- 1300 - - 1500 450 60-70 Rock media filter followede, Benzene, Napthalene, by activated sludge,= snol, Acrylonitrite, soft

:_agent base and resin- netic resins, Phenol- - 95-98 - - • Plastic media, 2 stage treatement-.aldehyde, fatty acid,

Influent contains:: alic acid, maleic acid.Phenol-4500 mg/I

•:eroi, pentaerythritolformaldehyde-2000 mg/Iants.Fatty acid - 800 mg/1Phthalic and maleic acid -1000 mg/Iphenol 1.5 mg/Ics, amines, enzymes 1960 37 98.1 2660 230 91.5 Two-stage trickling filter.

_.ed lagoon

=-* - ery,butadiene and 225 100 55 610 350 43 Followed by stabilisation pond,_ .. rubberery and detergent 345 50-100 71-85 855

Temp-32°C150- 71-83 Influent phenol and sulphide are

zhexane, p-Xylene 100 25 75 - 200 160 mg/f and 150 mgf respectively:4 -:ene, praffinftha,

- - Surface aeratorts,waste extensi.- . ene, nylon fibrere etc. vely pretreated followed by pond.

e stablisation pond-e - 7, Butadiene and: _ •' r,rbber

100 50 50 350 200 43 Ponds in series after aerated*' • ene, and propylene

glycols, morphlines,20 - - 5120

lagoon4610 10 25 Facultative ponds to remove some

f- • ene diamines and others. residual COD. High non biodegra-dation fraction after activated

'.y, detergent, alkylate 50- 20.50 50-80 150- 120 20-40 Aftersludge

lagoon200

53

Anaerobic Processes

The petrochemical wastewaters are reported to be effectively degraded anaerobic bacteria which cantolerate a wide variety of toxicants. Organics amenable to anaerobic treatment include: acetaldehyde,acetone, butanol, butylaldehyde, cresol, ethanol, ethylacetate, formaldehyde, methyl acetate nitroben-zene, phenol, propanol etc. Various anaerobid processes used with the efficiency of COD removal aregiven below:

Anaerobic process % COD removalContact process 80-95Upflow packed bed process 80-95Downflow packed bed process 75-88Upflow anaerobic sludge 85-95Vlanket process 85-95Fluid expended bed process 80-87

5.3 STATUS OF TREATMENT IN INDIA

In India, by and large, activated sludge process is practised as OSBL treatment. Elaborate treatment sys-tems i.e. combination of ISBL, primary treatment and secondary treatment are adopted in some cases.Resource recoveries are also accomplished. A few case studies of the treatment system adopted are il-lustrated in following sections.

5.3.1 Phenol -cumene wastewater

Besides resources recovery system (section 5.1.3), the effluents originating from different plants, utilitysections and other areas of M/s Herdillia chemicals Limited, are collected in a sump and pumped to paral-lel plate oil separators. After free oil separation, the effluent is taken into equilisation tank and pH is ad-justed to around 8.0. Equalised effluent is then fed at a steady rate to clariflocculator where alum is addedas floculating agent. Clear effluent from clariflocculator flows to aeration tanks where organic matter isbiodegraded by active biomass to reduce BOD and COD levels. Biomass and solid matter is separatedfrom effluent in a clarifier. Clarified effluent is then discharged into Thane creek. A part of the sludge fromclarifier is recirculated into the aeration tanks and rest is dried in sludge drying beds. Results of perfor-mance test is shown in schematic diagram Fig.5.1. The data indicate that the plant is capable of reduc-ing phenol, BOD and COD levels to meet the relevant standards. The efficiency of phenol and SOD removalis 99% and 95% respectively.

5.3.2 Caprolactum waste

M/s Gujarat State Fertiliser Company Ltd. (GSFC) has installed an effluent treatment facility for theircaprolactum plant. The treatment system comprises of the following unit processes :

• API oil separation• pH adjustment• Aerobic oxidation and sludge separation• Sludge drying

The design criteria and the performance of the treatment system are furnished in the schematic diagramFig. 5.2. It is reported that the plant has as such no problem of COD removal. But BOD removal efficien-cy could not be achieved to comply with the standards.

54

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56

Integrated petrochemical complex

=í National Organic Chemical Industries Limited (NOCIL)

NOCIL complex comprises of five Individual plants. The Industry Installed OSBL activated sludge treat-ment system. The effluents are received at the treatment plant through separate sewerage systems asstated earlier. The flow diagram alongwith observations are given in Fig. 5.3. The performance of thetreatment unit is given in Table 5.8. The graph shown in Fig. 5.4 are the results of eight months in 1987.The curves indicate TOO, COD and BOD did not exceed 50 mg/I, 120 mg/I and 25 mg/I respectively. Theefficiency of BOD removal is 90%.

Table 5.8 : Performance of Treatment Unit

r-:. - aterDesign

Biotreater FeedAnalyses byNOCIL

Analyses byCPCB

Treated EffluentAnalyses by Analyses byNOCIL CPCB

MaharashtraPollution ControlBd Limit

6.5-85 6.4-7.0 6.36-6.96 6.9-7.4 7.31-7.9 5.5-9.0;- ^ded Solds,mg/l - 20-53 - 40-50 18.35 100:-: grease,mg/I 50 8.25 2.8 1-8 1.8-2.4 -

c - Jes (S), mg/I - 1.0 - 1.0 0.15-0.32 5.0_ a, mg/I - 1.5-2.5 - 0.1 1.6-3.1 5.0

2950 905-1360 1535-2040 70-140 80-200 250^' = 200 C, mg/I 1500 625-875 998 5-30 - 100

on fish for - - - 100 - 90survival

u , alent Chromium, - 0.1 - 0.1 0.05 0.1

Indian Petrochemical Corporation Limited (IPCL)

IPCL is the biggest integrated complex in the country. It comprises of eighteen different plants. Thecharacteristics of liquid effluents vary widely because of diversity of manufacturing processes and varietyof raw materials and finished products. The effluents are broadly classified into three categories:

• Process and oily effluents• Sanitary wastes from canteen, toilets and townships• Blowdown of boilers and cooling towers and rainwater.

The effluent streams are segregated at*various production units and first treated through ISBL treatmentfollowed by treatment to reduce strength, toxicity and acidity/alkalinity. The facilities provided In ISBLtreatment are :

• Linear alkyl Benzene Plant-fluoride removal by lime treatment and concentration of sludge.• Polypropylene and LDPE plant-removal of polymers, metals like aluminium and titanium by coagula-

tion/clarification etc.• Poly butadiene rubber plant-removal of rubber scrumbs.• VC/PVC plant-stripping of EDC, neutralisation etc.• ACN plant-acidic effluent neutralisation.

Treated effluents from ISBL treatment facilities are given further OSBL treatment central waste water treat-ment plant which comprises of screw pumps (for prevention of emulsion formation), screen and grit cham-ber, flow measurement devices, surge ponds for equalisation, API oil separator for oil removal,

57

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FIG. 5.4 EFFLUENT CHARACTERISTICS OF Mis NOCIL

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9.38 352 619 442 8.4 17.9 48.8 32 95

6.4- 625- 905- 20-53 6.9- 5.30 70- 40-50967.0 875 1360 7.4 140

5.0- 2400 4050 1226 - 120 233 - 9510.0

6-8 1000-2000 50- 7-8 30 100 100 97-981500 3000 100

NA3.8 2500 5150 62 8.0 75 236 25 97

8.6 1055 1398 451 8.6 63 141 66.5 94system

0.94ActivatedO.1

1. IPCL Aromatic, olefinicglycols, LAB, LDPEpolypropylene,PVR, Acroylonertile,Acrylates, Acrylic-filler VCM/PVC.

2. NOCIL

Olefinic, Alcohol,VCM/PVC, Glycol

3. GSFC Caprolactumplant

4. MIS GujaratAromatics(DMT PLANT)

5. U C I L Olefinic plant

6. Herdillia Phenol-cumenechemicalsltd.

Activated BOD = 0.25 0.58sludge COD+ 1.91 n =12.

Activated NA NAsludge

two-stage BOD =0.38 0.61extended COD+33.19 n =86AerationExtended NA NAaeration

Activated NAsludge

Two steps BOD=

sludge COD+5.27

homogenation and flash mixer, clariflocculators, bioreactors, final clarifier sludge recirculation systemthickener, sludge drying beds and guard ponds for polishing the less treated effluents.

Apart from the centralised treatment, the effluents from a few specific plants are given special treatmeras these may interfere in biological treatment system e.g. sulphide, cyanide and fluoride removal.

The elaborate arrangeménts of effluent collection and treatment are presented schematically in Fig. 5.EIt was observed that the BOD and COD removal efficiencies are 95 percent and 93 percent respectivelw

Apart from the status of effluent treatment of above four plants, information on two other plants, are givenin Table 5.9.

Table 5.9 : Performance Evaluation of ETP

S. Name Type of plants Feed to ETP Effluent BOD Effluent EffluentCoi

No. of the pH BOD COD SS ph BOD COD SS remo- treatment BOD Vs Co-eff.plant val % plant COD relation BOD Vs

efficiency COD

NOTES : Results are expressed as mg/I except pH,

5.4 COST OF. EFFLUENT TREATMENT PLANT

In the cost analyses, OSBL treatment, commonly known as integrated waste water treatment cpetrochemical complex comprising of various petrochemical product processing units is considerec.Cost of ISBL treatment Is not included. In order to arrive at comprehensive treatment alternatives, charac-teristics reported by the existing units in the country furnished in Table 5.9 are considered:

• BOD5 20°C, 300-2500 mg/I• Suspended Solids, 50-500 mg/I• Phenols, 600 mg/I

• Sulphides, 20-60 mg/I

Flow rates between 94-1894 m 3/hourare considered for sizing the units and to develop the cost modules.

60

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61

Two levels of treatment i.e. primary and secondary including sludge handling and disposal were con-sidered for estimation of total cost. Cost estimate for tertiary treatment is avoided because of limited ap-plication in the country.

5.4.1 Development of the cost modules

Modular cost estimating technique is used for various process alternatives (Table 5.10) to develop themodule cost curves for estimating the primary capital investment and operation and maintenance (0 &M) cost for treating a given flow of waste water. The capital cost modules for various process alterna-tives include the cost of the equipment, foundation and civil work, piping, Instrument, chemicalstorage, electrical work, erection etc. The cost of land, site grading and plant lighting are excluded fromthe cost modules. The financial expenses eg. interest on borrowing, preliminary expense, insurance andmargin money for working capital etc. are also not reflected on the capital cost module.

Table 5.10 Cost Module

Primary treatment Secondary treatment Sludge handling Cost (Rs.lakh)

BOD- Cost systems BOD Cost System Cost Total O&M

reduction Rs.lakh reduction Rs.lakh Rs.Iakh capital

Industry System efficiency efficiency

IPCL Screwpump, 20 28 Activated 94 61 Thickener 16.5 105.5 11.9

surgepond, sludge, sludgeAPI separator, clarifier, dryingclarifier guard pond bed

NOCIL API separator 30 17.1 Activated 96.5 42 Sludge 7.7 66.8 11.5

+ neutralisation sludge drying+ Equilisation clarifier bed+clarifloculation

Herdiilia API seprator 17.6 7.5 Two stage 95 25 Sludge 4.8 37.3 9.5

Chemicals Ltd. + neutralisation activcated drying bed+equalisation sludge+clarifloculation

GSFC API+equalisation 17 7.5 Two stage 94 25 Sludge 4.8 37.3 9.5activated drying bedsludgeclarifier

NOTE: Based on dataldrawings collected from industries

The 0 & M costs in the cost modules for various process alternatives Include only the direct cost e.g.chemical, electricity, manpower, overhead etc. Other indirect costs e.g. depreciation, insurance, Inter-est on loan etc. are not included.

The figures are only indicative. Capital and 0 & M costs depends on energy cost. To arrive at the capi-tal cost of an industry, the base module cost should be multiplied by a system factor depending on thetype and the size of the treatment plant. From the cost figures (1987) given by M/s.Engineers IndiaLtd. (EIL), the system factor is estimated at 1.5 to 3.0. Thus, for a given waste water flow and characteris-tics, the suitable treatment alternative can be selected and the preliminary estimates can be made on thebasis of the cost modules as under:

Preliminary capital cost = (Cost of Primary and secondary treatment including sludgedisposal) X (1.5 to 3.0)

62

CHAPTER VI

MINIMAL NATIONAL STANDARDS (MINAS)

63

MINIMAL NATIONAL STANDARDS (MINAS)

6.1 PHILOSOPHY OF MINAS

Generally two main aspects are taken Into consideration for development of standards of wastewater dis-charges. One relates to the adverse effects on health and environment and the other achievability of limitsof pollutants by incorporation of appropriate pollution control measures.

The latter approach aims at use of the best available and economically feasible technology. Economi-cally feasible technology assures that the cost of pollution control measures will remain within the affor-dability of the industrial units. Standards developed on these principles are techno-economic standardsand these standards are uniform throughout the country.

An advantage of the technology-based approach is that within a specific group of industries the extentof pollution control measures are alike. In addition, these standards serve to preserve the environmen-tal quality in non-polluted areas without modification. The disadvantage of this approach is that thesestandards may become unnecessary burden on the industry where the recipient environment does notdemand such control measures. This is because these standards do not relate to the actual environmen-tal situation of the specific site.

However, it may be considered that development of standards based on the local environmental require-ments is not a practicable proposition for a country like India. Therefore, it is logical to evolve Industry-specific standards at the national level. To provide safeguard to the local environmental conditions, thelocal enforcing authorities are required to lower the limit values of pollutants (become stringent) as percase to case evaluation of the respective recipient bodies. On such exercise, these standards serve bothas specific for industry and location.

6.2 WASTEWATER QUALITY PARAMETERS

The parameters of relevance in petrochemical industries are BOD, COD, phenol, sulphide, cyanide,fluoride, total suspended solid (TSS), oil and grease etc. In addition to the above parameters, the pol-lutants like benzene, toluene, xylene, chlorinated hydrocarbons, phthalate esters, acrylonitirile etc are re-quired to be considered in view of their toxicity.

6.3 The four petrochemical industries e.g. IPCL, NOCIL, GSFC and Hardillia Ltd. where studies were con-ducted, installed effluent treatment plants to comply with the relevant standards prescribed by the con-cerned State Pollution Control Boards. The performance study also reveals that the Industries generallyconform to the standards. In view of the above, the cost factors of the above units are relevant in deter-mining the economic feasibility.

The expression of cost factor is represented by the following formula:

Annual Burden (AB)

Annual Turnover (AT)

If the figure on calculation is less than 5 then the cost of pollution co,trol measures is within the affor-dable limit (soft) of the industry.

Annual burden (AB) includes borrowed capital return, Interest on capital and O&M cost. These figuresare necessary for a year for which the annual turnover (AT) has been considered. This means that capi-tal and interest on capital have to be escalated to match the AT of the year concerned. In Table 6.1, thecalculated figures of AB and collected figures of AT are presented. It may be observed that all the fourindustries are in the soft category. It ensures that the industry can afford appropriate treatment of the ef-fluents to comply with standards.

65

Table 6.1 : Cost of Treatment in Petrochemical Industry

S. Name of Industry Annual Burden Annual turnover % Ratio RemarksNo. AB (Rs.Crore) AT (Rs.Crore) P = AB/AT

1. M/s Indian Petrochemicals 2 687 0.3 It is noted that the industryCorporation Ltd. is claiming they have spent

nearly 14 crore rupees fortotal purposes on pollutioncontrol. The ratio still is 2%which is soft. 2 crore takesinto escalation of price andISBL treatment.

2. M/s National Organic 1 275 0.36 M/s NOCIL claims they haveChemicals Ltd. spent Rs. 4 crore for all the

measures taken for installationof pollution control equipment.The ratio (P) is 1.4%. TheIndustry is soft.

3. M/s Hardillia Chemicals 0.5 68.55 0.7 M/s Herdillia chemicals isLtd. also found soft industry and

can take an extra burdenif necessary.

4. M/s GSFC 0.5 Although the annual turnoverdata is not available,the caprolactum plant is theonly one which is housed byM/s GSFC and the criticalratio is definitely in favour ofpollution control.

6.4 A comparative statement of standards of treated effluents is given in Table 6.2. Based on the performancestudy carried out, the standards followed by other authorities and consideration of annual burden, theMINAS has been evolved and presented in Table 6.2 and Table 6.3. It may be noted that the limits oftrace organic toxic compounds have not been Included. In future, limits of such compounds may beprescribed based on the monitoring facility and capability. However, for the present BOD, COD and oil

and grease limits are expected to take care of trace organics. It is recommended to carry out bio-assytest before disposal of treated effluents.

6.5 STANDARDS TO SATISFY ENVIRONMENTAL REQUIREMENTS

The concerned authorities has to modify the MINAS consistent with the local conditions. The receivingbody has much to do with such standards. The following factors should be taken into account in prescrib-ing such standards :

• Degree of dilution available In the receiving system.• Biotic species that will have to be protected.• Mean tolerance limit in respect of pollutants to the identified biotic species.• Application factor in respect of the mean tolerance limit.

Water quality criteria to protect biotic species and different uses of water are listed in Table 6.4 forreference. In evolving environmentally acceptable site specific standards, these criteria may be takeninto consideration.

Table 6.2 : Comparative Statements of Standards and MINAS

Gujarat Maharashtra Japars MINAS'Pollution Poll.Con.Bd., National National limitCon. Bd. (Applicable to limits of of discharge

Authority BIS 2490 BIS 7968 (Appl. to NOCIL and Discharge in India.

Receiving WaterBody

Surfacewater

Marinecoastal area

River Mahi EstuaryThane Creck

- -

pH 5.5-9.0 5.5-9.0 5.5-9.0 5.5-9.0 5.8-8.6 6.5-8.5BODs 20° C,mgII 30 100 100 100 150 50COD,mg/l 250 250 250 250 150 250Sulphide,mg/I 2.0 5.0 1.0 2.0 - 2.0Phenol,mg/I 1.0 5.0 1.0 5.0 5.0 5.0Cyanide as ON. 0.2 0.2 0.2 - 1.0 0.2mg /IFluoride as F 2.0 15 10 - 15 15mg/IHexavaien.t 0.1 1.0 0.1 0.05 0.5 0.5Chromium,mg/ITSS,mg/I 100 100 100 100 150 100Oil and grease 10 20 10 10 5.0 Free oil mustmg/I n-Hexane not be present.

extract

TABLE 6.3 MINIMAL NATIONAL STANDARDS (MINAS) FOR PETROCHEMICAL INDUSTRIES(BASIC AND INTERMEDIATE PRODUCTS)

Parameter Limits not to be exceededpH 6.5-8.5

* BOD5 20° C,mg/I 50COD,mg/l 250

** Phenol,mg/l 5Fluoride as S- r;;g;1 2Cvanide as CN.mg,1 0.2

*** Fluoride as F,mg/l 15***' Hexavaien.tchromium cr,mg/I 0.1

Total chromium as cr.mg/I 2Total snol ls,mg/l 100

* State Board may prescribe a lower BOD value (say 30 mg/I) if the recipient system so demands.

** The limit for phenol shall be conformed at the outlet of effluent treatment of phenol cumenepart. However at the final disposal point, the limit shall be less than 1 mg/I.

*** The limit for fluoride shall be conformed at the outlet of fluoride removal unit. However, atthe disposal point fluoride concentration shall be lower than 5 mg/I.

**** The limit for total and hexavalent chromium shall be conformed at the outlet of the chromateremoval unit. This notes that in the final treated effluent, total and hexavalent chromiumshall be lower than prescribed herein.

67

Table 6.4 : Water Quality Criteria

S. N. Parameters Unit Criteria To protect References

1. pH - 5-9 a) Domestic water Quality criteriasupplies (welfare) for water-Russell

6.5-9.0 b) Fresh water E.Train*aquatic life page 178-179

6.5-8.5 c) Marine aquaticlife

2. Biochemical mg/I 3 Less than 5 for Council of Europeanoxygen demand drinking water Community Directive5 days at 20° C source as per of June 16, 1975,

council of European concerning the qualitycommunity, required for surface

water of drinkingwater in the memberstates, 1975.

3. Chemical Oxygendemand mg/I 30 - -- do --

4. Oil and grease mg/I a) virtually NTAC, 1968 Quality criteriafree from oil and gr- virtually for water-Russelease, parti- absent E.Train,cularly from page 111-112the tastesand colors

mg/I b) 0.3 as Causes for rejec- CPHEEO Drinkingmineral oil tion for acceptable Water Standards-

as drinking water 1976

c) 0.1 as min- Cause for accep-eral oil tance as drink-

ing water

d) 30 on land for Tolerance limitsIrrigation for Industrial eff-

luents dischargedon land for irri-gation purposeIS-3307,IS-1965,IS-1965

e) 0.1 Public water Tolerance limitsupply source of Indian surface

waters subject topollution IS-2296-1974, IS-1974.

68