interim report fydp final 86
TRANSCRIPT
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 1/53
CHAPTER 7: INSTRUMENTATION AND CONTROL
7.1 INTRODUCTION
Control in process industries refers to the regulation of all aspects of the process.
Precise control of level, temperature, pressure and flow is important in many process
applications. Refining, combining, handling, and otherwise manipulating fluids to
profitably produce end products can be a precise, demanding, and potentially hazardous
process. Small changes in a process can have a large impact on the end result. Variations
in proportions, temperature, flow, turbulence, and many other factors must be carefully
and consistently controlled to produce the desired end product with a minimum of raw
materials and energy. Process control technology is the tool that enables manufacturers to
keep their operations running within specified limits and to set more precise limits to
maximize profitability, ensure quality and safety.
Process control refers to the methods that are used to control process variables
when manufacturing a product. For example, factors such as the proportion of one
ingredient to another, the temperature of the materials, how well the ingredients are
mixed, and the pressure under which the materials are held can significantly impact the
lit f d d t
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 2/53
lit f d d t
The overriding motivation for modern control systems is safety, which encompasses
the safety of people, environment, and equipment. The safety of plant personal and
people in the community is the highest priority in any plant operation. The design of a
process and associated control systems must always make human safety the prime
objective.
ii. Profit
When people, the environment and plant equipment are properly protected,
control objectives focus on the profit motive. Automatic control systems offer strong
benefits in this intention. Plant wide control objectives motivated by profit include
meeting final product specifications, minimizing waste production, minimizing
environmental impact, minimizing energy use and maximizing overall production
rate. Product specification sets by customers are an essential priority. Example
product specifications range from maximum or minimum values for density, viscosity
or component concentration, to specification on thickness or even color.
iii. Production Rate and Quality
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 3/53
In this chapter, there will be concise description of control strategies for two major
equipments and three minor equipments which are:
• Reactor
• Distillation column
• Heat exchanger
• Pump
• Compressor
7.2 REACTOR CONTROL SYSTEM
The main purpose of the reactor is to provide an area where ethylene and benzene
could react to produce ethylbenzene via liquid phase reaction. Since the reactor is the
main equipment that converts the feed into product, it is crucial that we perform a proper
control around the reactor so that we produce consistent quality product.
The first requirement for a successful control of a reactor is to establish proper
stoichiometry in order to control flow of the reactants (composition control) in proportions required as to satisfy the reaction chemistry (Perry’s, 1997). In this plug flow
reactor, R-101, benzene to ethylene is fed in ratio of 4:1 to guarantee that product
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 4/53
3. Safety
• Provide the safeguards against the process runaway reaction and maintain the safe
operation
• To maximize catalyst and prolong its life cycle
The fail-close valves are employed especially in the case of failure, that is when the
reactor’s internal temperature is becoming too high, the coolant would still be flowing in
the cooling coils via the fail-close valve and vice versa. This is vital to ensure that the
coolant would be flowing to cool down the reactor rather than letting it overheated. A
pressure safety valve, PSV is installed on the reactor to discharge excessive pressure
whenever necessary.
Table 1: Summary of Control Strategy for Reactor
Measured
Variable
Manipulated
Variable
Disturbances Type of Controller
Feed’s flow
rate at R-101
Benzene and
ethylene
flowrate
Compositional
changes in
benzene and
th l
Ratio control
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 5/53
Symbols:
FT – Flow Transmitter
RC – Ratio Controller
FC – Flow Controller
LC – Level Controller
LT – Level Transmitter
Title: Instrumentation and Control Strategy for
Reactor
Note: N/A
Project : Ethylbenzene Plant
Designer: GROUP 9 Date: 03-10-2010
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 6/53
As the reaction scheme requires a stringent control to be exercised in terms of reactants’
compositions to attain optimal yield, therefore a ratio control is chosen to ensure that this
requirement is fulfilled. This ratio control is a special type of feedforward control. Its
objective is to maintain the ratio of (4:1). Therefore it measures the disturbance in which,
is coming from both benzene and ethylene streams in this case.
Secondly, as the reactions involved in the whole process are entirely in liquid phase,
hence, the level of liquid resulted is among the main concern. Therefore, the simple
feedback control scheme is proposed to provide better control of the liquid level. The
liquid level from the reactor is measured and transmitted electronically to a level
controller. The controller compares the measured value to the set point and takes the
appropriate corrective action by sending signal to the control valve.
Thirdly, as the reactor chosen is operating isothermally and that, the reactions carried out
inside it are exothermic in nature, therefore temperature control is significant. For that
reason, cascade control is ideally proposed and has the following features:
1. The output signal of the master controller serves as the set point for the slave
controller.
2 The two feedback control loops are nested with secondary control loop (slave
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 7/53
7.3 DISTILLATION COLUMN CONTROL STRATEGY
This section will introduce the control strategy of distillation column. There are three
distillation columns in Ethylbenzene Plant with different top and bottom products. The
common operation of a distillation column is based on the production of a vapor phase by
boiling the liquid mixture, and condenses the vapor allowing some liquid or reflux to
return to the column. However, only the control system for C-102 is explained in detail in
this report. The other two of distillation columns will be having similar control strategy.
The control system for this column is designed with following control objectives:
1. Feedrate
• To maintain the federate to the distillation column at desired value. It is
achieved by the feed flow is controlled.
2. Column pressure
• To control the pressure of top tray at desired value. It is achieved by
manipulating the flowrate of cooling water. If the cooling water is
increased, then more vapor is condensed at the pressure is reduced.
3. Column Temperature
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 8/53
Table 1: Summary of Control Strategy for Distillation Column
MeasuredVariable
ManipulatedVariable
Disturbances Type of Controller
Column
pressure
Flowrate of
cooling water
Change of
temperaturecooling water
Feedback control
Column
temperature
Steam flow rate
to reboiler
Pressure of steam
flow
Cascade control
Liquid level indistillation
column
Bottom productflowrate Distillate flowrate Feedback and overridecotrol
Top product
composition
Reflux rate Column
temperature
Feedfforward and
feedback
Feedrate Feed flowrate Pressure of feed
flowrate
feedback
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 9/53
Symbols:
PT – Pressure Transmitter
PC – Pressure Controller
TT – Temperature Transmitter ll
Title: Instrumentation and Control Strategy for
Distillation Column
Note: N/A
P j t Eth lb l t
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 10/53
manipulated. But the disturbance is the pressure of the steam flowrate itself. Since the
disturbance variable is associated with the manipulated variable, cascade control is the
best way to overcome it. It consists of primary control loop of which control the column
temperature and secondary control loop which control the steam pressure. If disturbance
in a supply pressure occurs, the pressure controller will act very quickly to hold the steam
pressure at it set point before it upsets the master set point.
Liquid level of the distillation control is simply control by flow controlled. However, the
problem exists here is that the safety concerns. Suppose the base level in a distillation
column is normally held by bottoms product withdrawal. A temperature in the stripping
section is held by steam to the reboiler. Situations can arise where the base level
continues to drop even with the bottoms flow at zero (vapor boilup is greater than the
liquid rate from tray 1). If no corrective action is taken, the reboiler may boil dry and the
bottoms pump could lose suction. Thus, override control is taking place in this matter.
When the level drops below the permitted level, then the temperature controller takes
place in spite of the level controller. The feedrate to the distillation column is also simply
feedback control.
The other parameter most likely to be controlled is the composition of the tops product.
the reason is that the final product come from the top of the column and it is important to
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 11/53
The purpose of performing a control system for heat exchanger is to maintain the desired
temperature of its outlet stream either by providing the heating or cooling utility. The
outlet stream of the heat exchanger will be compared with the set point. If the
temperature is not at the desired level, the controller will take action by manipulating the
flow rate of the utility. In the plant, there are two heat exchangers and two coolers; the
detail description is shown in Table X below. All the heat exchanger and cooler used
same control system. The objective is to control the outlet temperature at the desired set
point. The type of controller being use is cascade controller.
1. Temperature outlet stream
• Cascade control is implemented with the temperature control as the
primary loop and flow control as the secondary loop.
Measured
Variable
Manipulated
Variable
Disturbances Type of Controller
Temperature of
at liquid at
outlet stream
Flowrate of
steam into heat
exchanger
Changes in steam
flowrate
Cascade controller
- (TIC) master loop
To maintain the temperature in the heat exchanger output process stream by manipulating
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 12/53
Symbols:
PT – Pressure Transmitter
PC – Pressure Controller TT – Temperature Transmitter
TC – Temperature Controller
Title: Instrumentation and Control Strategy for Heat
Exchanger
Note: N/A
Project : Ethylbenzene plant
Designer: GROUP 09 Date: 15-09-2010
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 13/53
Pumps are used to transfer liquids from one point to another and woked based on the
principle of pressure difference. It should be noted that all the pumps that are used in our
plant are of minor pumps, where they are working to hike the pressure of supply streams,
and that their content and flow are abundant and will not dry out. Therefore, we will only
allocate a pressure gauge on both of the inlet and outlet of the pump.
Table 5: Summary of Control Strategies for Pump
Control
Variable
Measured
Variable
Manipulated
Variable
Disturbances Type of Controller
1. Inlet
flowrate
Pressure
differenceacross pump
Recycle line
flowrate
Changes in the
inlet’s flowrate
Feedforward control
2. Inlet
pressure
Flowrate of
pump outlet
Pump speed Change in the
inlet flowrate
Close loop ration
control
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 14/53
7.6 COMPRESSOR CONTROL STRATEGY
The main use of a compressor is to increases the pressure of a vapor stream.
Compressor is a single phase unit as it cannot process mixed-phased stream that will
destroy its blades.
Table 6: Summary of Control Strategies for Compressor
Control
Variable
Measured
Variable
Manipulated
Variable
Disturbances Type of Controller
1. Inlet
flowrate
Pressure
across
compressor
and pressure
across
restriction
orifice
Recycle line
flowrate
Changes in the
inlet’s flowrate
Feedforward control
2. Inlet
pressure
Flowrate of
compressor
Compressor
speed
Change in the
inlet flowrate
Close loop ration
control
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 15/53
Symbols:
PG – Pressure Gauge
FT - Flow Transmitter
FC – Flow Controller
Title: Instrumentation and Control Strategy for
Compressor
Note: N/AProject : Ethylbenzene Plant
Designer: GROUP 09 Date: 15-09-2010
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 16/53
8.1 Hazard and Operability Studies (HAZOP)
8.1.1 Description
A Hazard and Operability (HAZOP) study is a structured and systematic examination of
a planned or existing process or operation in order to identify and evaluate problems that
may represent risks to personnel or equipment, or prevent efficient operation. The
HAZOP technique was initially developed to analyze chemical process systems, but haslater been extended to other types of systems and also to complex operations and to
software systems. A HAZOP is a qualitative technique based on guide-words and is
carried out by a multi-disciplinary team (HAZOP team) during a set of meetings.
The HAZOP study should preferably be carried out as early in the design phase as
possible - to have influence on the design. On the other hand; to carry out a HAZOP we
need a rather complete design. As a compromise, the HAZOP is usually carried out as a
final check when the detailed design has been completed. A HAZOP study may also be
conducted on an existing facility to identify modifications that should be implemented to
reduce risk and operability problems.
8 1 2 Prerequisite
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 17/53
To ensure high success rates, we need to provide accuracy of drawings and data used as a
basis for the study, utilize experience and skills of the HAZOP team leader, technical
skills and insights of the team, ability of the team to use the HAZOP approach as an aid
to identify deviations, causes, and consequences, ability of the team to maintain a sense
of proportion, especially when assessing the severity of the potential consequences.
8.1.4 HAZOP Study Procedures
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 18/53
been done for three process lines, in which HAZOP assessments are performed on two
major equipments and one minor equipment. The three equipments are:
• Node 1: Reactor (R-101)
• Node 2: Distillation Column (C-102)
• Node 3: Heat Exchanger (E-1)
Although the basic HAZOP Analysis approach is well established, the way that it is
employed may vary from organization to organization. Table lists guide words that are
commonly used in HAZOP Analysis.
8.1.5 Guidewords
Table 8: List of basic HAZOP guidewords
GUIDEWORDS MEANING No (not, none) None of the design intent is achieved
More (more of, higher) Quantitative increase in a parameter
Less (less of, lower) Quantitative decrease in a parameter
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 19/53
Process Section: Reactor R-101
Intention: To transport raw materials into the reactor, R-101.
Node 1: Stream S7Process parameter: Flow
Table 8: HAZOP Analysis for Node 1 - Flow
Guide
word
Deviation Possible causes Possible consequences Required actions
No No flow • Use of fail closed typed
control valve
• Fracture of pipe
• No feedstock supplied, no product
produced as no reaction taken place
• Reactor shutdown
• Employ fail opened typed control
valve
• Install emergency shutdown (ESD)
valve or shutdown plant immediately
Less Less flow • Leakage in piping
• Blockage in pumps
• Control valve failed
partially opened/closed
position
• Reduced rate of reaction
• Inconsistent production rate
• Reduced amount of process fluids to R-
101
• Install flow indicator
• Install low flow or low level alarm to
R-101
• Install check valve to stream S-7
More More
flow
• Control valve fails open • Increased amount of process fluids to
R-101 and over spillage
• Install flow indicator
• Install high flow alarm and relief valve
104
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 20/53
Reverse Reverse
flow
• Backflow due to
backpressure in reactor
• Reduced amount of feedstock, thus
reduced yielded product
• Install check valve or flow indicator
and alarm to acknowledge the changes
in flow
• Regular inspection and maintenance of
valve
Process parameter: Pressure
Table 10: HAZOP Analysis for Node 1 - Pressure
Guide word Deviation Possible causes Possible consequences Required actions
Less Less
pressure
• Leakage in pipeline • Reverse flow
• Loss of raw material,
desired reaction cannot
be achieved
• Install pressure indicator
• Install low pressure alarm
• Install ESD valve
More More
pressure
• Control valve fails open • High pressure and could
lead to overpressure
(pressure build-ups) in R-
101
• Runaway reaction
• Install pressure indicator and high
pressure alarm
• Install ESD valve
• Install relief valve
Process parameter: Temperature
105
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 21/53
Table 9: HAZOP Analysis for Node 1 - Temperature
Guide
word
Deviation Possible causes Possible consequences Required actions
Less Less
temperatur
e
•Temperature indicator
fails
•Heat exchanger
failure/ inefficient
• Optimal reaction scheme cannot be
attained
• Reduced yield
• Inspect, maintain temperature
indicator and replace it promptly if it
fails
• Inspect and maintain heat exchanger
periodically
More More
temperatur
e
•Temperature indicator
fails
•External heating
• High pressure in reactor
• Uncontrolled and excessive heat release
surrounding R-101
• Install temperature indicator and
high temperature alarm
• Instruct operator by procedures
• Install cooling water flow meter
• Check heat exchanger
Process Section: Distillation Column C-102
Intention: To transport process materials from separator C-101 to separator C-102.
106
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 22/53
Node 2: Stream S11
Process parameter: Flow
Table 11: HAZOP Analysis for Node 2 - FlowGuide
word
Deviation Possible causes Possible consequences Required actions
No No flow • Control valve fails
closed.
• Column C-101
empty.
• Fracture pipe.
• Isolation valve
closed.
• No process material to separator.
• No ethylbenzene produced.
• Plant shutdown.
• Release of hazardous material.
• Use control valve fails open.
• Install low flow alarm to alert
operator
• Install hazardous substance detector
and alarm.
Less Less flow • Pipe leaking.
• Control valve failed
in partially open
position.
• Blockage in pipe or
pump.
• Less process material to separator.
• Ethylbenzene production rate decrease.
• Install flow indicator
• Install low flow or low level alarm to
S-11.
More More flow • Control valve fails
open
• Air pressure to drive
• Increased amount of process material to
C-102.
• Over spillage.
• Install flow indicator
• Install high flow alarm
• Install relief valve at reactor
107
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 23/53
valve fails
• Incorrect instrument
reading.
• Overpressure in separator.
Reverse Reverse
flow
• Backflow due to
backpressure in
reactor
• Reduced amount of feedstock, thus
reduced yielded product.
• Desired flow could not be achieved.
• Plant shutdown
• Install check valve.
• Regular inspection and maintenance
of valve.
Process parameter: Temperature
Table 12: HAZOP Analysis for Node 2 - Temperature
Guide word Deviation Possible causes Possible consequences Required actions
108
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 24/53
Less Less
temperature
•Heat exchanger failure.
•Temperature control error.
• Cooling water control
valves fails closed.
• Possible thermal
runaway
•
Decrease product yield
• Install low temperature alarm.
• Adequate pipe installation.
More More
temperature
•External heating
•Heat exchanger failure.
•Temperature control error.
• Cooling water control
valves fails closed.
• High pressure in
distillation column.
• Uncontrolled and
excessive heat release.
• Desired product cannot
be separated
• Install temperature indicator and high
temperature alarm
• Install cooling water flow meter.
Process parameter: Pressure
Table 13: HAZOP Analysis for Node 2 - Pressure
Guide word Deviation Possible causes Possible consequences Required actions
109
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 25/53
Less Less
pressure
• Leakage/rupture in
pipeline.
• Compressor malfunction.
• Control valve fails close.
• Reverse flow
• Loss of raw material.
• Desired reaction cannot
be achieved
• Install pressure indicator
• Install low pressure alarm
More More
pressure
• Control valve fails open.
• Compressor malfunction.
• Build up pressure in C-
101.
• Runaway reaction • Install pressure indicator and high
pressure alarm
• Install ESD valve
• Install PSV.
110
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 26/53
Process Section: Heat Exchanger E-1
Intention: To transport materials to transkylation reactor, R-102
Node 3: Stream S19
Table 14: HAZOP Analysis for Node 3
Parameter Deviation Possible causes Possible consequences Required Actions
Flow No flow • Upstream flow
disrupted
• Heater, its line and
downstream line
rupture
• Line blockage
• No feed to R-102, less yield
• Release of hazardous and flammable
material
(a) Install control valve that fails open
(b) Install low flow alarm at R-102 inlet
(c) Install hazardous substance detector and
alarm
More flow • Leakage in the heat
exchanger tubes
causing mixture of product of
ethylbenzene streamwith the feed of
transkylation reactor
• Mixture of ethylbenzene with
transkylation feed stream affects the
reaction and produce less product
• Decrease temperature of feed to R-102
• Overflow of reactor and release of
hazardous material
(d) Install high flow alarm at reactor inlet
• Covered by (c)
Less Flow • Line fracture, leakage
(flange/valve and heat
exchanger shell)
• Failure of charge pump
• Flow return to the mixer
• Low feed flow to the reactor
• Feed loss and release
(e) Install bypass valve
• Covered by (a)Covered by (b)
111
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 27/53
Reverse
flow• Heat exchanger/Line
rupture leading to low pressure and no flow
• No/Low feed
• Potential flow back to mixer
• Feed loss and release of hazardous and
flammable material
(f) Install check valve
• Covered by (a)
• Covered by (b)
Temperature Higher
temperature• Heat exchanger failure
• Faulty transmitter
• Change of reactant phase (g) Install high/low temperature indicator
alarm at reactor inlet
(h) Regular patrolling and inspection of the
heat exchanger
(i) Install two transmitter
Lower
temperature• Heat exchanger failure
• Faulty transmitter
• Hot stream temperature
at inlet heat exchanger
is too low
• Reactor conversion cannot be achieved
• Low reaction rate is achieve Covered (g), (h) and (i)
112
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 28/53
Pressure Lower
pressure• Equipment/line rupture
leading to less/no flow
•
Clogging in pipe
• Loss and spillage of feed
• Release of hazardous and flammable
material
• Less feed to the reactor
• Bring damage to the equipment
(j) Install low/high pressure alarm at pump
(water line) outlet
(k) Install a pressure relief valve on pipeline
• Covered by (c)
Higher pressure
• Blockage at reactor
inlet
• Overpressure will lead to line rupture
• Spurge flow into reactor
• Pressure build up in the reactor
• Covered (c) , (j) and (k)
No pressure • Equipment/line rupture
leading to no flow
• Loss and spillage of product
• Release of hazardous and flammable
material
• No feed to reactor
• Reversible flow occur
• Covered (c) , (j) and (k)
113
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 29/53
8.2 PLANT LAYOUT
8.2.1 Introduction
Plant layout and construction design must be considered early in the design work to
ensure economical construction and efficient operation of the completed plant. This
section of the report provides the basic information and safety justifications on the
plant layout designed for the newly proposed ethyl benzene plant.
In general, the layout shows the basic arrangement of main production site,
supporting buildings and few important safety aspects. However, the plant layout
adopted may affect the safe operation of the completed plant and if needed, any
possible modification or extension must be accepted. Plant layout is often a
compromise between a numbers of factors such as:
• The need to keep distances for transfer of materials between plant/storage units to
a minimum to reduce costs and risks
• The geographical limitations of the site
• Interaction with existing or planned facilities on site such as existing roadways,
drainage and utilities routings
• Interaction with other plants on site
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 30/53
8.2.2 Plant Layout Consideration Factors
Based on the previous factors stated, the factor to design plant layout for the ethyl
benzene has been narrowed down to several factors as followed. Thus, to ensure that the
final design for plant layout is complied with all the factors that has been discussed
earlier.
a. Cost - Minimization of construction cost is done by adopting shortest run of
connecting pipe between equipment. The cost is also reduced by having the least
amount of structural steel work. The most important thing is to have an
arrangement for best operation and maintenance.
b. Operation - Equipment such as valves, sample points and instruments are
considered as frequently attended equipments. They are located not far away from
control room, with convenient positions and heights, to ease the operator’s job.
Also, sufficient working and headroom space are provided to allow easy access to
equipments.
c Maintenance - When laying out the plant some considerations were made
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 31/53
d. Safety - Among the safety consideration that we have when laying out this plant
are:
• Operators have 3 escape routes if anything occurs in the main process unit
• To minimize fire from spread, flammables handling process units are
separated from each other
• Process vessels with substantial inventories of flammable liquids are
located at grade
• Elevated areas will have at least one stairway
• Storage farm which stores the flammable materials are located at safe
distance from the main process area
• Equipment subject to explosion hazard is set away from occupied
buildings and areas.
8.2.3 Site Layout
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 32/53
8.2.3.1 Non-Process Area
The non-process area usually occupies a smaller fraction of the overall plant site area. All
the facilities in the non-process area should be located in a logical manner that considers
site terrain, accessibility to roads, soil bearing capability and the climate including the
wind direction and other unusual weather condition. This is important to avoid any
undesired incident due to explosion or fire from the process zone that will be easily
spread to the non-process area.
Taking this into account, the entire process area where the reaction and separation occurs
is surrounded with a buffer zone to ensure that surrounding buildings or sites are not
affected in case of an emergency. Among the buildings or units in the non-process areaare:
a) Guard posts
Guard posts are located at the entrance of the site in order to ensure that only
authorized personnel gets access into the plant. There are three guard posts that aresituated at the crucial entrances in the plant:
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 33/53
material spillage at the plant. With this, the public are less exposed to the
danger of chemicals exposure or accidents with the trucks.
b) Administration building
The administration block is built near the parking area which acts as assembly area
for staffs as well to ensure the staffs can arrive faster at the assembly point during an
emergency. Based on the plant layout, the administration building is placed far from
the process area in order to protect the staffs and visitors from any potential hazards.
c) Canteen
The canteen is located across the administration building for easy access to the
employees and visitors, and far away from the process area to avoid contaminant in
food and ensure safety of the public. The location is so strategic that in order to avoid
the food supplier from being exposed to the process area allowing them to move in
and out easily.
There are other facilities that located in the non-process area including prayer hall,
clinic and parking lot. Prayer hall is located near cafeteria for Muslims employees to perform their prayers during breaks. Clinic and parking lot is located side by side just
next to Gate 4 for the staffs and visitors benefits.
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 34/53
area guard post is to ensure that all the personnel will obey to the plant rule and
regulations.
b) Control building
All the control valves for the whole process area will be controlled and monitored
from this central control building. The control building is designed with blast proof
construction and has emergency backup power and is air conditioned in order to save
and secure the vital documents of the process that it houses during emergency.
c) Laboratory
The quality of the purity of ethyl benzene is tested after the product is recovered to
determine whether it meets the specifications or not. All the results will be sent to the
control room and some adjustments in controlling will be made, if needed. The
distance between laboratory and control room is not too far. Laboratory staffs will
also perform analysis of the waste of the process before being channeled to
wastewater treatment and flare system; or being released to atmosphere.
d) Waste treatment plants
The waste stream from the separation area will flow into the waste treatment plant to
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 35/53
f) Separation site
The main objective of this treatment unit is to separate between the products,
byproducts and unreacted reactants to be recycled back to the transalkylation reactor.
Its location is at a distance away from the reactor site and next to laboratory. The
units are arranged on the production line from high pressure to low pressure so as to
ease the flow of product. The units are properly spaced among each other for
maintenance and also for safety.
g) Utilities site
This unit will supply cooling water, high pressure steam and nitrogen to the main
process unit. Its location is perfectly suitable to give the most economical run of pipe
to and from the process unit.
h) Storage Vessels and Drums
This unit stores vessels and drums containing products that are going to bedistributed locally, chemical substance, lubricants and catalyst used for the process.
It also stores chemicals needed for the waste treatment plant It is situated near the
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 36/53
Ample area is allocated at the process area for future expansion in case the
management decides to increase production rate or other crucial considerations. They
occupy enough space for further expansion, whether for process reaction or
producing the plant’s own utility such as cooling water and steam.
k) Pump house and Compressor house
Pump house and compressor house are located just beside the reactor site to house
the pumps and compressor that are used in the production and distribution of the
product, ethyl benzene to customers.
l) Loading area
Loading area is where the trucks deliver the chemicals used in running of the plant
and also load the products that are going to be distributed locally. Thus, it is directly
located to the storage.
m) Flare area
Flare is used to burn excess gas that is emitted from the process units as well as to
burn some of the waste gas from waste treatment area. The flare is located in thesame area for wastewater treatment plant and far from the process area and
administration complex for this purpose
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 37/53
M a i n r o a d
Chemical Storage Units
Reactor System
L o a d i n g a n d u n l o a d i n g
b a y
Utility Sections
Gate 1Gate 2
Gate 3
Flare
Raw materials
Future expansion site 2 / Assembly area 2
Future expansion
site 1 / Assembly
Area 1
Training
Center/Seminar /Conference Room
Administration and Technical Services
Parking Canteen
Prayer Hall
Clinic
Main Power Supply
Guard House
Wastewater treatment
plant
Laboratory
Future expansion site 3
Fire station
Separation Section
Maintenance
Warehouse
Control building
Minor Equipments
Housing
Gate 4
Figure 2: Plant Layout of Ethylbenzene Production Plan
122
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 38/53
CHAPTER 9: WASTE WATER TREATMENT
9.1 Introduction
Waste is unwanted or unusable materials. Waste is directly linked to human
development, both technologically and socially. The compositions of different wastes
have varied over time and location, with industrial development and innovation beingdirectly linked to waste materials. Wastewater is any water that has been adversely
affected in quality by anthropogenic influence. It comprises liquid waste discharged by
domestic residences, commercial properties, industry, and/or agriculture and can
encompass a wide range of potential contaminants and concentrations.
In a chemical plant, the wastewater is defined as a combination of the liquid or
water that carries waste removed from commercial and industrial establishment.
Wastewater, one of the major contributors to the increasingly heated environmental
problem consists of toxic contaminants that may lead to direct fatal of all organisms
including aquatic or land inhibited animals and even human beings. Non-biodegradable
toxic waste is absorbed into the body system via food chain, which consequently leads to
serious disease such as cancer, food poisoning and others.
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 39/53
Wastewater from Ethylbenzene production plant comprises of unused reactants
and byproducts from the process side due to process divergence. The most appropriate
wastewater treatment to be applied is the one that meets the recommended
microbiological and chemical quality guidelines both at low cost and with minimal
operational and maintenance requirements.
9.2 Laws and Regulations on Industrial Waste (Malaysia)
Generally, all industries in Malaysia must comply with the law and
regulations stated in the Environmental Quality Act 1974 (EQA 1974). Basically,
this is an Act relating to the prevention, abatement, control of pollution and
enhancement of the environment, and for purposes connected therewith. This act
includes 34 regulations, which covers three (3) auxiliary regulations that aresignificant to the plant environmental issues:
i. Environmental Quality (Clean Air) Regulation 1978
ii. Environmental Quality (Sewage and Industrial Effluent) Regulation 1979
iii. Environmental Quality (Scheduled Waste) Regulation 1989.iv. Other closely related regulations
(a) Environmental Quality (Compounding of Offences) Rules 1978
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 40/53
According to Environmental Quality (Scheduled Wastes) Regulations 1989, solid wastes
are categorized in 107 categories in the First Schedule wastes. It consists of two parts:
i. Part I: Scheduled Wastes from Non-Specific Sources
ii. Part II: Scheduled Wastes from Specific Sources
In the schedule, proper reference likes tagging with a specific number is required to make
it easier for classification. It is important for plant management to classify the waste
accordingly before proceed with the treatment. Each treatment differs for different kind
of waste. Therefore, they must follow the guidelines stated in the regulations on waste
collection, packaging, labeling, and transportation of the wastes for further treatment and
disposal. Based on the regulation, schedule waste shall be treated at prescribed premises
or at on-site treatment facilities only.
9.2.2 Liquid Waste
As for the effluent discharge from the industry, it needs to comply with the
Environmental Quality (Sewage and Industrial Effluents) Regulations, (Regulation 8(1)Third Schedule, Standards A, EQ 1979). In this context, industrial effluent means liquid
water or wastewater produced by reason of the production processes taking place at any
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 41/53
Table 15: Plant Wastewater and Standard A Values of EQA
Parameter Unit Standard A Plant wastewaterTemperature ˚C 40 70.00
BOD5 at 20˚C ppm 20 100-200
COD ppm 50 1000-1500
Suspended solids ppm 50 < 100
9.2.3 Gaseous Waste
The gaseous emission limits from the chemical industry must comply with the
Environmental Quality (Clean Air) Regulations, 1977. The primary source of the gas
emission of Ethylbenzene production plant is from the purge gas of benzene side product.
The Clean Air Act that was enacted in 1970 includes the National Emission Standards for Hazardous Air Pollutants. This standard controls air emission levels of harmful toxins
like benzene. It was reported that benzene exposure significantly increased one's risk of
developing leukemia by adding benzene to the list of toxic air pollutants. Oil refineries
and other industrial operations must comply with federal and state environmental law in
regards to benzene emissions.
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 42/53
Treatment
Stage
Description
Preliminary Removal of any constituents from wastewater which can clog or
damage pumps, or interfere with subsequent treatment processes.
Primary Removal of organic and inorganic solids by the physical processes of
sedimentation and flotation.
Secondary Removal of colloidal and dissolved organic and inorganic solids of
effluent from primary treatment. The secondary treatment process
consists of the biological treatment of wastewater by utilizing many
different types of microorganisms in a controlled environment.
Tertiary and/or
Advanced
Removal of dissolved organic matter that cannot be removed by
secondary treatment.
9.3.1 Physical Methods
Physical methods include processes where no gross chemical or biological changes are
carried out and strictly physical phenomena are used to improve or treat the
wastewater. Physical treatment is usually the first step in a larger wastewater treatment
process. In general, the mechanisms involved in physical treatment do not result in
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 43/53
process. In filtration process, sewage is passed through filters to separate the
contaminating solids from the water. Sand filter is a common filter used in this process.
9.3.2 Chemical Methods
In chemical water treatment, chemicals are used to treat wastewater in order to improve
water quality. The most common method to treat water using chemicals is chlorination,
wherein chlorine, a strong oxidizing chemical is used to kill the bacteria and slow downthe rate of decomposition of the wastewater. Bacterial kill is achieved when vital
biological processes are affected by the chlorine. Ozone, an oxidizing disinfectant, is
another oxidizing agent used to treat polluted water . These oxidizing agents affect the
biological growth process of bacteria, thus making the water usable.
Neutralization is another chemical process used in many industrial wastewater treatment
operations. Neutralization consists of acid and basis to adjust the pH levels back to
neutrality. Lime is one of example of base used in the neutralization of acid wastes.
Coagulation consists of the addition of a chemical. There are small particulates in
wastewater where suspended in water forming a colloid. These particles carry the samecharges, and repulsion prevents them from combining into larger particulates to settle.
Thus by adding a chemical reaction will occur and forms an insoluble end product that
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 44/53
In the biological water treatment process, microorganisms, mostly bacteria are used to
biochemical decomposition of wastewaters to stable end products. More
microorganisms, or sludges, are formed and a portion of the waste is converted to carbon
dioxide, water and other end products. There are two sub-divisions of biological waste
treatment which are aerobic and anaerobic, based on availability of dissolved oxygen. In
the aerobic process, bacteria consumes the organic matter and helps convert it to carbon
dioxide in the presence of oxygen, while in the anaerobic process, sludge is fermented at
a particular temperature in the absence of oxygen. Another aerobic process is
composting, where sludge is mixed with carbon sources such as sawdust to treat
wastewater.
Table 17: Summary of Treatment Methods
Properties Physical Chemical Biological
Types of
process
Sedimentation,
aeration and filtration
Chlorination,
neutralization,
coagulation, and carbon
adsorption
Aerobic
Anaerobic
Advantage Simple andinexpensive process
to separate solid and
Capable to improvewater quality using
chemical reaction and it
Consume thecontaminants in
wastewater using
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 45/53
There are three levels of wastewater treatment applied in the Ethylbenzene production
plant which are preliminary, primary, secondary and tertiary (or advanced). In the
preliminary treatment, any constituents which can clog or damage pumps, or interfere
with subsequent treatment processes are removed from the wastewater. Then it proceed
with the primary treatment which involve sedimentation, and is the process by which
about 30 to 50 percent of the suspended solid materials in raw wastewater are removed.
The purpose of preliminary treatment is to protect the operation of the wastewater
treatment plant. This is achieved by removing from the wastewater any constituents
which can clog or damage pumps, or interfere with subsequent treatment processes. The
organic matter remaining after primary treatment is extracted by biological secondary
treatment processes to meet effluent standards. Secondary treatment commonly is carried
out using activated-sludge processes, trickling filters, or rotating biological contactors.
Tertiary wastewater treatment is additional treatment that follows primary and secondary
treatment processes. It is employed when primary and secondary treatment cannot
accomplish all that is required.
9.4.1 Preliminary Treatment
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 46/53
treatment units. Flow equalization and mechanical mixing in the collection sump will
level out the hydraulics load on treatment units.
9.4.2 Primary Treatment
Primary treatment is designed to remove organic and inorganic solids by the physical
processes of sedimentation and flotation. Approximately 25 to 50% of the incoming
biochemical oxygen demand (BOD5), 50 to 70% of the total suspended solids (SS), and
65% of the oil and grease are removed during primary treatment. Some organic nitrogen,
organic phosphorus, and heavy metals associated with solids are also removed during
primary sedimentation but colloidal and dissolved constituents are not affected.
Primary treatment devices reduce the velocity and disperse the flow of wastewater. In
primary treatment the velocity of flow is reduced to 1 to 2 feet per minute to maintain a
quiescent condition so that the material denser than water will settle out and material less
dense than water will float to the surface. The solids that remain in suspension as well as
dissolved solids will usually be biochemically treated in subsequent processes for
physical separation and removal in the final (secondary) settling tanks.
Further the settling rate of a particle depends on the strength and freshness of the
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 47/53
process consists of the biological treatment of wastewater by utilizing many different
types of microorganisms in a controlled environment. In most cases, secondary treatment
uses aerobic biological treatment processes to remove biodegradable dissolved and
colloidal organic matter. Aerobic biological treatment is performed in the presence of
oxygen by aerobic microorganisms (principally bacteria) that metabolize the organic
matter in the wastewater, thereby producing more microorganisms and inorganic end-
products (principally CO2, NH3, and H2O). Several aerobic biological processes are used
for secondary treatment differing primarily in the manner in which oxygen is supplied to
the microorganisms and in the rate at which organisms metabolize the organic matter.
The microorganisms must be separated from the treated wastewater by sedimentation to
produce clarified secondary effluent. The sedimentation tanks used in secondary
treatment, often referred to as secondary clarifiers, operate in the same basic manner as
the primary clarifiers described previously. The biological solids removed during
secondary sedimentation, called secondary or biological sludge, are normally combined
with primary sludge for sludge processing.
9.4.4 Tertiary and/or Advance Treatment
Advanced Wastewater Treatment may be broken into three major categories
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 48/53
(e.g.chemical addition to primary clarifiers or aeration basins to remove phosphorus) or
used in place of secondary treatment (e.g., overland flow treatment of primary effluent).
9.5 Solid Waste
Some examples of possible solid waste obtained from this plant are residue, spent catalyst
and suspended solids. Residues are materials remaining from burning or heat reaction of
coke and combustible or volatile waste. Suspended particles from source of steam (water)
and particulates from equipments and piping lines also contribute to the solid waste..
According to Environmental Pollution Act, the waste can be classified as hazardous as
the waste exhibits the following characteristics: ignitability, corrosivity, reactivity, and
toxicity. Solid waste consist mainly the sludge removed from the liquid waste after
biological treatment and little amount of spent catalyst. Suspended solids can be removed
by settling and sedimentation using clarifiers. The characteristics of solids and sludge
produced during wastewater treatment are summarized in Table 18
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 49/53
Scum/greaseFloatable material from primary and secondary
settling tanks
Primary sludge Usually grey and slimy with foul odour.
Activated sludge Generally has a brownish, flocculants appearance
Digested sludgeBrown and has a flocculants appearance but
usually no offensive odour.
Environmental Quality (Scheduled Wastes) Regulations 1989 requires that scheduled
wastes be treated and disposed of at facilities approved by Department of Environment
(DOE). Presently most local authorities in Malaysia dispose solid wastes in landfills.
Incineration has always been viewed as a risk in terms of costs and effectiveness. The
existing Town and Planning Act do not allow the use of incinerators in urban areas.
Landfills cover 60 to 90 percent of the served areas, and are projected to cover up to 70 to
95 percent in the near future. 80 percent of the waste disposal sites had less than 2 years
of operating life remaining in 1990, emphasizing the urgency for municipalities to secure
new landfills before the existing ones is exhausted.
One of the disposal areas of scheduled wastes for Peninsular Malaysia is provided byKualiti Alam Sdn Bhd. The company owns and operates the Integrated Scheduled Waste
Management Centre (WMC) at Bukit Nanas Negeri Sembilan The waste treatment
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 50/53
Stream (S) Component Composition Amount (kg/hr)
S27 Ethyl Benzene 0.02 22.57
Diethyl Benzene 0.05 56.43Ethyl Toluene 0.01 11.29
Triethyl Benzene 0.31 349.86
Diphenyl Ethane 0.62 699.73
The estimated amount of wastewater that will be entering the wastewater treatment
system is 1128.59 kg/hr. After completing the wastewater treatment, then only the treated
water will be drained back into South China Sea.
Table 20: Plant Wastewater and Standard B Values of EQA
Parameter Unit Standard B Plant wastewaterTemperature ˚C 40 39
PH value 5.5-9.0 6.0-8.0
BOD5 at 20˚C ppm 50 100-200
COD ppm 100 150-250
Suspended solids ppm 100 < 100
Others None
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 51/53
Therefore, total estimated gaseous waste in the plant is 6438.63 kg/hr. National emission
standard or limits have been established pertaining to particular source of gas emissions
with respect to the country regulation itself. Therefore, an efficient and sophisticated
degree of control must be implemented for industrial emission.
These gases must be vented to avoid dangerously high pressure in the operating
equipment, from plant start up and from emergency shutdown. The system for safely
venting process equipment during these situations is called emergency relief systems.
Such system usually has many safety valves tied into one collection system. They are
designed with large pipes to ensure large volume can be handled at low pressure. The
lines lead to a water seal drum and to a flare stack, where the gaseous such as benzene are
flared at a safe height above the process area.
Flare tips use steam to create a turbulent mixing between air and the stack gas at the top.
It also provides some cooling of the flare tip and stack. The flammable gas is ignited at
the top by a continuous pilot. The main control that needs to be maintained along the
flaring process is the control of proper steam flow. This is because with proper steam
flow, smokeless operation can be maintained at all conditions of gas flow, which providean almost complete combustion of gaseous.
The flaring process may results in some smoke emissions to the atmosphere In order to
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 52/53
7/28/2019 Interim Report FYDP Final 86
http://slidepdf.com/reader/full/interim-report-fydp-final-86 53/53
Figure 3: Process Flow Diagram of Wastewater Treatment System for Ethyl Benzene PlantUntreated Waste Water
Treated Water
Equalization
138