air pollution control technology japan

Source: Global Environment Centre Foundation (GEC) - Ministry of the Environment of Japan - Website: http://gec.jp/

Exhaust Gas Treatment EquipmentPIPE FILTER (Exhaust Gas Processing Unit)1. Purpose Acidic and oil mist produced in various manufacturing processes are the causes of various types of trouble. Public sentiments and lows and regulations against pollution and environmental problems have become stricter over recent years, increasing demands for exhaust gas treatment for factories. The exhaust gas processing system using a pipe filter which we are now introducing aims at processing floating mist and gases efficiently with a simple unit and with lower maintenance and running costs. 2. Performance and Characteristics Target exhaust gas: Exhaust gases containing any type of mist except for strong alkali or hydrogen fluoride Diameter of mist particles to be processed: 0.025 micro - m or over Collecting efficiency: 95 - 100% Pressure loss: 50 - 250 mmH2O 3. Features The pipe filter consists of cylindrical layers of fine glass fibers would around a base material, through which the original gases pass from the outside to the inside, and collects mist using inertia collision, diffusion and contact. Because the void ratio and the filtering area per filter is very large and the outer and inner densities are diverse, all sizes of mist particles can be collected efficiently with only a small pressure loss. Because of being made of glass, the filter is superior in heat resistance and it does not swell nor change its shape. The mist particles collected by the glass fiber layers are naturally coagulated to drop and be discharged out through a drain. Even if the source gas includes insoluble dust, those of particles diameter 1 micro-m or smaller flows with the collected fluid. (Dust particles of 1 micro-m or larger should be processed in advance.) Such a selfcleaning function allows stable performance for a prolonged period of time without the need for maintenance, as well as having a simple structure; it can be installed cheaper, it is compact, and operation and management are very easy.Reedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 1


4. Applicable Gases Mist and exhaust gases produced by various chemical devices and production processes. 5. Example of Implementation Treated gases: Acid and alkali exhaust gases including fine metallic particles. Gas volume to be processed: 15,000 m3N/h Temperature of processed gas: 60 deg.C The pipe filter is installed at the last process of the normal filling-layer type scrubber to absorb gases and remove mist, resulting in a high processing efficiency. The recirculating fluid lowers the processed gas temperature removing the smoke generated by condensation caused by the temperature difference between the hot exhaust gas from the exhaust pipe and the atmosphere. Exhaust Gas Treatment Equipment

Toxic substance removal technology The flue gas treatment system of the municipal solid waste incineration plant1. IntroductionReedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 2


In Japan, municipal solid waste (MSW) incineration has outweighed others in the intermediate treatment system because of its capabilities to sanitate and reduce volume of waste. However, environmental pollutants such as dust, NOx, SOx, HCl, dioxins and heavy metals are included in the flue gas from MSW incinerators. As awareness to environmental preservation, high efficient flue gas treatment system is being required to reduce these pollutants. In this term, advanced flue gas treatment system using the bag house filter, and catalytic denitrification tower etc. is shown. 2. Constitution Fig.1 Schematic flow diagram of flue gas system

Acid gas cleaning : Slaked lime powders or slurry Dust collector : the bag house filter Filter : A felt filter cloth Cleaning method : Pulse jet Additive : Activated carbon powders, etc. DeNOx : Catalytic denitrification tower Dioxins : Catalytic denitrification tower or Activated coke packed tower 3. Characteristic (1) Dioxins can be removed at high efficiency by the bag house filter followed by the catalytic denitrification tower or the activated coke packed tower. (2) Dioxins and NOx can be removed simultaneously by the catalytic denitrification tower. (3) In order to improve dioxins and Hg removal efficiency, the additives such as activated carbon is fed.Reedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 3


(4) Dust, Heavy metals and acid gas such as HCl, HF, can be removed at high efficiency by the bag house filter. (5) The catalytic denitrification can be conducted effectively even at low temperature using low temperature active catalyst which was developed. 4. Application field Flue gas treatment of MSW and industrial waste incineration and melting furnace of MSW incinerator ash. 5. Operation data and effect Experimental data of flue gas treatment from existing fluidized bed incinerator of MSW are shown below. (1) Dioxins: NH4OH + SReedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 8


By scrubbing crude gas containing hydrogen cyanide with sulfur suspended alkalic solution, hydrogen cyanide is removed in the form of thiocyanate which is non-toxic. (Main Reaction: In case of NH3-alkaline) Reaction of Ammonium Polysulfide Production 2NH3 + H2S + xS -> (NH4)2SX+1 Reaction of Ammonium Thiocyanate Production (NH4)2SX+1 + HCN + NH3 -> NH4SCN + (NH4)2Sx 2. Schematic Diagram An example of the flow sheet of Fumaks, Rhodacs and Compacs processes

3. Advantages - Desulfurization efficiency can be adjusted in the design close to 100% according to the customer's requirement. Stable efficiency can be maintained. - Low cost of chemicals for desulfurization - The absorption liquid can be circulated (recycled) under ambient temperature without pressurization - Efficient regeneration by premix nozzles - Small land space and low installation cost - Sulfur recovery efficiency is as high as 70 to 80% - Decyanization efficiency can be adjusted in the design up to 100% according to the customer's requirement.Reedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 9


- When H2S, NH3 and HCN are contained simultaneously in the process gas, toxic substances can be removed through chemical reactions of these compounds, thus improving the process economy. - Compact system - Easy operation and maintenance 4. Treatment Capacity The process is applied for plants with gas treatment capacity of 1,200 to 200,000Nm3/h. 5. Applications Purification for coal gas or oil gas 6. Installations Since 1960, there have been 23 installations with Fumaks Process, 8 installations with Rhodacs Process, and 11 installations with combined Fumaks-Rhodacs Processes. since 1960. 7. Treatment of the waste water from these Processes There is a waste water burning process which can turn solid sulfur or sulfur compounds into useful products. (See Page about "Compacs Process") Exhaust Gas Treatment Equipment Acid gas purification techniques for CO2 (carbon dioxide) Benfield Process 1. Outline The Benfield Process is applicable to the removal of H2S and CO2 from gases, such as natural gas, oil refinery off gas, reformed gas, etc. This process can be more efficiently adapted to the requirements for treating a gas by a combination of typical flow types provided for the removal of CO2 only, or CO2 and H2S, and for reducing heat consumption. Kobe Steel, Ltd. has obtained technical assistance from Union Cabide Corporation in designing and constructing the plants shown in the Reference section. 2. Features 1) A very effective activator is used to lower the equilibrium partial pressure of acid gases and accelerate the absorption rate.Reedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 10


2) The heat consumption for regeneration of the absorbing liquid is appreciably reduced by the use of a steam ejector. 3) The HiPure Process is a good choice for high purification where H2S must be removed to 1 ppm or less, and CO2 to only a few ppm. 4) No specific anti-corrosive material in needed for the equipment. 5) The absorbing liquid is nontoxic and no proprietary chemicals are used. 6) The absorbing liquid suffers no degradation and a reclaimer is not necessary. 3. Process Flow The absorption and regeneration of acid gases in the Benfield Process are based on the following reactions: K2CO3 + CO2 + H2O = 2KHCO3 K2CO3 + H2S = KHS + KHCO3 (1) (2)

In the HiPure Process, the reactions described below are added. 2R2NH + CO2 + H2O = (R2NH2)2CO3 (R2NH2)2CO3 + CO2 + H2O = 2R2NH2HCO3 2R2NH + H2S = (R2NH2)2S (R2NH2)2S + H2S = 2R2NH2HS (3) (4) (5) (6)

The absorption and regeneration of acid gases are conducted in a similar way to that of the conventional amine or carbonate processes. The gas to be treated is fed to the bottom of the absorber and flows countercurrent to the absorbing liquid supplied at the top of the absorber. Acid gases are then absorbed by the absorbing liquid. The liquid that has absorbed the acid gases is preheated and then supplied to the top of the regenerator where the acid gases are stripped by steam for the regeneration of the liquid. The regenerated liquid is precooled and recirculated to the absorber. 4. Benfield Process

Reedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi.

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Process Flow Diagram

Exhaust Gas Treatment Equipment

Acid gas purification techniques for H2S (hydrogen sulfide) Stretford Process 1. Outline The Stretford Process is a wet-type desulfurization process used in various industries in which hydrogen sulfide is removed from gas streams and sulfur is recovered. About 100 plants have been constructed worldwide and have operated successfully since this process was developed by the British Gas Corporation. It has become one of the most widely used desulfurization processes with an excellent performance record. Kobe Steel, Ltd. first obtained technical assistance from the British Gas Corporation in 1964. Since then we have designed and constructed the plants shown in the Reference section.Reedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 12


2. Features 1) This process is applicable to any gas, such as coke oven gas, natural gas, oil refinery, gas, reformed gas, coal gas, etc. 2) The hydrogen sulfide content in the treated tail gas can be reduced to less than 0.1 ppm at atmospheric and higher pressures. 3) Sulfur is recovered with a high purity of more than 99.5 wt.% 4) Hydrogen sulfide is selectively removed from gas streams containing a high concentration CO2 with high efficiency. 5) Simple operation and energy savings can be achieved as the absorption and regeneration are performed at moderate temperature (30 - 40 deg.C) . 6) The chemicals used in the process are stable, nontoxic and easily treated. 7) Several effluent treatment systems have been established. So there is no problem of secondary pollution due to the effluent. 8) The absorbing solution is weakly alkaline (pH 8.5 - 9.0) and noncorrosive. 3. Reaction Mechanism The absorption and regeneration are based on the socalled "Redox reaction" that causes the catalyst effects of anthraquinone disulfonic acid (in short, ADA)and vanadate in a weakly alkaline solution. 2H2S + 2Na2CO3 -> 2NaHS + 2NaHCO3 2NaHS + 4NaVO3 + 4NaHCO3 -> 2S + Na2V4O2 + 4Na2CO3 + 3H2O (2) Na2V4O2 + 2Na2ADA + 2Na2CO3 + 3H2O -> 4NaVO3 + 2Na2ADA(Redured) + 2NaHCO3 2Na2ADA (Reduced) + O2 -> 2Na2ADA + 2H2O (1)

(3) (4)

4. Process Flow The gas to be treated flows countercurrent to the absorbing solution in the absorber and H2S is removed by the reaction with the absorbing solution. The packings used in the absorber are usually splash-type plates designed in a specific manner. The absorbing solution is delayed at the bottom of the absorber and hydrogen sulfide inReedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 13


the solution is converted to elemental sulfur as a result of the reaction. Then the solution is sent to the oxidizer, where a supply of air is received to regenerate the solution completely and to float elemental sulfur in the slurry. The froth of the sulfur slurry is concentrated by a filter or a centrifuge to form sulfur cake, which is reslurried with water and heated to recover molten sulfur of high purity from the sulfur separator. On the other hand, the solution regenerated in the oxidizer is sent to the balance pit and then pumped up to the absorber. 5. Stretford Process

Flow Diagram

Exhaust Gas Treatment Equipment KAWASAKI LIME MOVING BED HYDROGEN CHLORIDE REMOVAL SYSTEM (KALM SYSTEM) 1. OUTLINE This is completely dry type cross flow moving bed system which removes acid gas constituents effectively from the combustion exhaust gas. The quick lime (calcium oxide) filled in the moving layer removes hydrogen chloride and sulfur oxides effectively according to the following reaction formula. CaO + 2HCl --> CaCl2 + H2O CaO + SOx --> CaSOx


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Fig.1. Diagram of the Device Principle

Fig.2 Schematic of KALM


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2. PROCESS FLOW CHART CASE 1

CASE 2

3. FEATURES (1) Because this is of completely dry type and uses no water, no white smoke is generated and a trouble resulting from calcium ion accumulation does not occur. (2) When installed at downstream of the dust collecting device, reaction products can be separated from fly ashes ensuring remarkable utilization. (3) It is possible to remove hydrogen chloride and sulfur oxides effectively.Reedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 16


4. APPLICATIONS 1) Gas volume 2) Gas temperature 3) Acid gas removal rate

Free 200 - 300 deg.C HCl Less than 50 ppm (In case of MSW Incineration Plant) SO2 Less than 10 ppm (In case of MSW Incineration Plant)


WET TYPE HYDROGEN CHLORIDE AND SULFUR OXIDES REMOVAL SYSTEM1. Introduction In this system, the exhaust gas is washed by water neutralized with caustic soda (sodium hydroxide). This system is made up of a spray tower and a filling tower. A dehumidifying layer should be added for plume prevention. This system has a high efficiency of removing hydrogen chloride and sulfur oxides. The chemical reaction formulae as follow: HCl + NaOH -> NaCl + H2O SO2 + 2NaOH + (1/2) O2 -> Na2SO4 + H2O 2. System outline The exhaust gas from the incineration furnace passes through a dust collector (ESP or baghouse) where its particulate is removed. It is then fed to the spray tower (venturi scrubber) where its temperature is lowered to a saturated level. The exhaust gas then goes into the filling tower. The washing water is neutralized with caustic soda at a value of pH 7 or less.


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Fig.1 shows the flowchart of the wet type hydrogen chloride and sulfur oxides removal system. Fig.1 Wet type hydrogen chloride and sulfur oxides removal system

3. Characteristics The treatment allows for removing 95 to 98% of hydrogen chloride and 85 to 95% of sulfur oxides. Water treatment process and plume preventive equipment are necessary. The mercury elimination efficiency is 80 to 90%. 4. Capacity This system has no limit on the treated gas volume. 5. Sphere of application This system can be applied to any furnace exhaust gas, for example, one for Municipal Solid Waste (MSW) incineration. 6. Actual results Takuma has installed 30 wet type hydrogen chloride and sulfur oxides removal systems in MSW incineration furnaces in Japan. Exhaust Gas Treatment Equipment

SEMI-DRY TYPE HYDROGEN REMOVAL SYSTEM1. Introduction

CHLORIDE

AND

SULFUR

OXIDES


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In this system, hydrated lime (calcium hydroxide) slurry is injected into a quenching reactor to reduce the gas temperature and to neutralize the acid gas contained in the exhaust gas. Hydrated lime powder is injected into a dry venturi to enhance the pollutant removal effect. A baghouse (fabric filter) is designed to allow a formation of a thick dust cake layer on its surface. When the exhaust gas passes through the baghouse, the unreacted hydrated lime contained in the cake layer contacts and reacts with the acid gas in the exhaust gas, thereby improving removal effect. The chemical reaction formulae are as follows: 2HCl + Ca(OH)2 -> CaCl2 + 2H2O SO2 + Ca(OH)2 -> CaSO3 + H2O CaSO3 + (l/2)O2 -> CaSO4 2. System outline In the hydrated lime slurry tank, hydrated lime is mixed with water to form a slurry and then fed into the quenching reactor. Hydrated lime slurry is sprayed with air by dual fluid nozzles. Hydrated lime powder and a powder type special dose are injected into the dry venturi by the blower. The exhaust gas containing hydrated lime powder, special dose auxiliary and reaction products is then fed into the baghouse. Fig.1 shows the flowchart of the semi-dry type hydrogen chloride and sulfur oxides removal system. Fig.1 Semi-dry type hydrogen chloride and sulfur oxides removal system

3. Characteristics


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The treatment allows for removing 90 to 98% of hydrogen chloride and 80 to 95% of sulfur oxides. Water treatment process and plume preventive equipment are not required. The mercury elimination efficiency is 50 to 70%. The removing performance of the semi-dry type is largely dependent on the gas temperature at the baghouse; the gas temperature should be controlled very precisely by spraying hydrated lime slurry in the quenching reactor. At lower gas temperatures, larger amounts of hydrogen chloride and sulfur oxides are removed. 5. Capacity This system has no limit on the treated gas volume. 6. Sphere of application This system can be applied to any furnace exhaust gas, for example, one for Municipal Solid Waste (MSW) incineration. 7. Actual results Takuma has installed 10 semi-dry type hydrogen chloride and sulfur oxides removal systems in MSW incineration furnaces in Japan. Exhaust Gas Treatment Equipment DRY TYPE HYDROGEN CHLORIDE AND SULFUR OXIDES REMOVAL SYSTEM 1. Introduction In this system, hydrated lime (calcium hydroxide) powder is injected into the exhaust gas through a dry venturi to neutralize acid gases. A baghouse (fabric filter) is designed to allow a formation of a thick dust cake layer on its surface. When the exhaust gas passes through the baghouse, the unreacted hydrated lime contained in the cake layer contacts and reacts with the acid gas in the exhaust gas, thereby improving the removal effect. The chemical reaction formulae are as follows: 2HCl + Ca(OH)2 -> CaCl2 + 2H2O SO2 + Ca(OH)2 -> CaSO3 + H2O CaSO3 + (1/2)O2 -> CaSO4 2. System outline Hydrated lime powder and a powder type special dose are injected into the dryventuri by the blower. The exhaust gas containing hydrated lime powder, special dose auxiliary and reaction products is then fed into the baghouse.


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Fig.1 shows the flowchart of the dry type hydrogen chloride and sulfur oxides removal system.

Fig.1 Dry type hydrogen chloride and sulfur oxides removal system 3. Characteristics The treatment allows for removing 80 to 95% of hydrogen chloride and 55 to 75% of sulfur oxides. Water treatment process and plume preventive equipment are not required. The mercury elimination efficiency is 50 to 70%. The removing performance of the dry type is largely dependent on the gas temperature at the baghouse; the gas temperature should be controlled very precisely by spraying water at an upstream quenching cooler. At lower gas temperatures, large amounts of hydrogen chloride and sulfur oxides are removed. 4. Capacity This system has no limit on the treated gas volume. 5. Sphere of application This system can be applied to any furnace exhaust gas, for example, one for Municipal Solid Waste (MSW) incineration. 5. Actual results Takuma has installed 15 dry type hydrogen chloride and sulfur oxides removal systems in MSW incineration furnaces in Japan.


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Exhaust Gas Treatment Equipment Catalytic Incinerator 1. Outline This equipment catches malodorous gases with the platinum catalyst and decomposes them by oxidation to harmless and odorless carbonic acid gas and water. Compared with the direct combustion type, this equipment is capable of treating malodorous gases at low temperature, so running cost is low. In case concentration of malodorous substances is low in particular, it is advisable to install Honeycomb Type Deodorization Equipment as a pre-treatment equipment to save energy greatly. 2. Structure of the equipment - Treating gas containing malodorous substances are pre-heated while it is passing through the heat exchanger. - Treating gas is heated to the predesigned temperature by the auxiliary heater (generally to 300 deg.C ). Electricity, city gas, LPG, kerosene oil, etc. can be selected as heat source.


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- When heated treating gas passes through the catalyst-bed, malodorous substances contained are decomposed by oxidation as they contact the catalyst. - Purified gas is exhausted after passing through the heat exchanger where heat is exchanged between purified gas and treating gas. In combination with a steam heater: In case electricity is used as heat source for the auxiliary heater, it is advisable to use a steam heater together with it to reduce electric consumption greatly, which reduces running cost. 3. Features - Low running cost: Compared with the direct combustion system, this equipment is capable of treating malodorous substance at low temperature, so fuel costs can be reduced by under (1/3). - No secondary air pollution is ensured. - Low boiling organic solvents and wider ranges of malodorous substances can be purified. - Power source for auxiliary gas burner can be selected widely. Since the mixed type gas burner is used, city gas, LPG, butane gas, etc. can be used as heat source with the simple adjustment of the gas burner. Electric system is standardized for smaller units. 4. Applied fields Chemical industries, painting, printing, rubber and casting factories 5. Installation example of system


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DRY TYPE FLUE GAS TREATMENT SYSTEM1. PREFACE Millions of tons of waste are produced worldwide every day; most of it is dumped in landfills or discharged to rivers and sea without prior treatment. However, while the demand for waste disposal capacities is increasing, the availability of suitable sites is on the decline. Waste has become a critical problem for industrial society, particularly in big cities and densely areas. Therefore, the need to avoid or reduce the generation of waste and to recycle the waste produced will become an ever important political and economic issue. However, disposal capacities will continue to decrease in spite of the reduction in the volumes of waste produced. For this reason it is necessary to coordinate and optimize waste management. The future development of incineration as a waste disposal method will of course depend mainly on whether optimum reductions in the total emissions of solid, liquid and gaseous products from waste incineration plants can be ensured without leaving environmental and economic aspects unconsidered. The prevailing trend can be clearly seen from the changes in the European and Japanese emission limits for flue gases from waste incineration plants. HITACHI ZOSEN has been making every effort to research, develop and improve flue gas cleaning systems to meet clean air standards which are getting progressivelyReedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 24


more and more strict and severe in every countries in the world. This document briefly introduces DRY TYPE FLUE GAS TREATMENT SYSTEM which is one of typical types of flue gas cleaning system. 2. PROCESS DESCRIPTION This system consists of the following equipment as shown on fig.1; - Evaporative Type Cooler - Bag Filter - Storage and injection equipment for Lime and Supplemental agent Fig.1 DRY TYPE FLUE GAS TREATMENT PROCESS (Waste Heat Boiler Type Cooler)

Fig.1 is simplified flow chart of this DRY TYPE FLUE GAS TREATMENT SYSTEM (Bag filter system). Flue gas from a refuse incinerator is fed to Evaporative Type Cooler, in which the flue gas temperature is regulated by means of evaporation of injected water. The flue gas temperature at the inlet of Bag Filter is controlled to be appropriate for the reaction, which makes the removal of gaseous pollutants efficient and prevents the filter cloth from clogging caused by melting of reaction products (salt) such as CaCl2 and suffering heat damage. After being temperature-conditioned, the flue gas is mixed with fine-grained Ca(OH)2 and supplemental agent which are supplied into the flue gas duct, where powdered Ca(OH)2 reacts with gaseous pollutants such as SO2, SO3, HCl and HF (if any). In simple terms, the following reactions take place; 2SO2 + 2Ca(OH)2 -> 2CaSO3.(1/2)H2O + H2O (1)25



SO3 + Ca(OH)2 -> CaSO4.2H2O 2HCl + Ca(OH)2 -> CaCl2 + 2H2O If HF is present in the flue gas, 2HF + Ca(OH)2-> CaF2 + 2H2O

(2) (3)

(4)

The powdered Ca(OH)2 reacts with the gaseous pollutants on its surface and core of particle remains unused. The gas/solid mixture is fed into the Bag Filter, in which solids (reaction product, unused Ca(OH)2 and flue gas dust) are effectively separated from the flue gas through the filter cloth. The gaseous pollutants will come in contact with unused Ca(OH)2 for further reaction. The filtrate cake is periodically removed from the filter cloth by means of pulse jet of compressed air injected into clean side of the bag house with a lance(on-line cleaning). Supplemental agent is added to the powdered Ca(OH)2 to facilitate the removal of the cake and the above mentioned reaction, furthermore in case of special supplemental agent supplying, it effects removal of another pollutants which are Dioxins and Hg, due to carbon contained in the supplemental agent. The relation between the flue gas temperature controlled, Equivalent of Ca(OH)2 to HCl/SOx and the gaseous pollutants removal efficiency is shown on fig.2. Fig.2 HCl and SO2 removal efficiency on a bag filter system


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3. SYSTEM FEATURES Nowadays this system has high performance of noxious gases removal at the same as with the Wet Type Process on constant research and much experience on this system (We at HITACHI ZOSEN has 44 plants of actual experience as of April, 1998). This DRY TYPE FLUE GAS TREATMENT SYSTEM has main features as follows; - High removal efficiency for noxious acid gases - Simple and easy maintenance - Stable and easy operation - Low capital costs


WET TYPE FLUE GAS TREATMENT SYSTEM1. PREFACE HITACHI ZOSEN has been making every effort to research, develop and improve flue gas cleaning systems to meet clean air standards which are getting progressively more and more strict and severe in every countries in the world. This document briefly introduces WET TYPE FLUE GAS TREATMENT SYSTEM which is one of typical types of flue gas cleaning system. 2. PROCESS DESCRIPTION This system consists of the following equipment as typically shown on fig.1; - Scrubber and Water circulation pumps - Hydrocyclone and Effluent Pump - Cooling Tower and Gas Reheater - Caustic soda storage and injection equipment


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Fig. 1 WET TYPE FLUE GAS TREATMENT PROCESS

This process can be subdivided into the following steps; (1) Flue gas cooling and scrubbing Flue gas from a refuse incinerator is fed to Scrubber in which the flue gas is cooled to saturation temperature and simultaneously contained gaseous noxious pollutants are absorbed (removed) by contact with circulating water. The noxious pollutants absorbed in the circulating water, reacts with caustic soda injected as follows; SO2 + 2NaOH -> Na2SO3 + H2O SO3 + 2NaOH -> Na2SO4 + H2O HCl + NaOH -> NaCl + H2O If HF is present in the flue gas, HF + NaOH -> NaF + H2O (2) Absorbing and dehumidifying The flue gas from the lower part (Cooling Part) rises to the upper part (Dehumidification Part) of the Scrubber, where the gas is first distributed to the packed bed and contact with circulating water efficiently for further absorption of remained gaseous pollutants. Simultaneously the flue gas is supercooled (dehumidified), because the circulating water is forced to be cooled through Cooling Tower, and it effects prevention of white plume from the Stack. (3) Hot air mixing and Treated flue gas reheating The flue gas leaving this Scrubber is fed into Air/Gas Mixer where the flue gas is mixed with heated air, thus the flue gas is heated up and its water content is reduced to be under less than saturation point. After that the flue gas is fed into Gas ReheaterReedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 28

(1) (2) (3) (4)


where it is heated up again to a temperature above 140 deg.C that is minimum temperature for preventing corrosion trouble of the following metal-made equipment. The condition of flue gas introduced to the Stack; its water content and temperature, is settled for prevention not only of above mentioned corrosion trouble but also of white plume exhausting from the stack. (4) TDS concentration control of the circulating water As is mentioned above, acid gas such as HCl and SOx contained in the flue gas is neutralized with caustic soda injected into the circulating water, and as a result it generate salt such as NaCl and Na2SO4. If this salt was not at all discharged, it is possible to cause clogging of the flue gas entrance of the Scrubber by its drying-up (Crystallising). Therefore, a part of the scrubbing water is withdrawn from the Scrubber sump with adjusting concentration of salt-compounds (TDS) not more than 10% and is sent to Wastewater Treatment Plant. The Scrubber sump bottom is withdrawn periodically and pumped up to Hydrocyclone in order to remove solids or foreign materials which might cause clogging of Spray Nozzles for the circulating water. 3. SYSTEM FEATURES Flue gas introduced into Scrubber is very corrosive due to contained various acid gases, and has a high temperature, therefore it is necessary for the Scrubber to be specially considered to be protected from troubles such as its internal's corrosion and burning out. The inside of this Scrubber is made completely corrosion-proof and thermal resistant by employing firebricks, resin and resin lined material. And further other assistant equipment is designed for keeping not only of its performance, but also its stable operation, on our much experience on this system (We at HITACHI ZONES has 29 plants of actual experience as of April, 1998). Thus this our WET TYPE FLUE GAS TREATMENT SYSTEM has main features as follows: - High efficiency of noxious pollutants removal - Simple structure free from corrosion - Stable and easy operation - Very low pressure loss (This means economical) Exhaust Gas Treatment Equipment

EDV TYPE FLUE GAS TREATMENT SYSTEM1. PREFACE HITACHI ZOSEN has developed various kinds of innovative or improved technologies in the field of environmental protection processes since we firstReedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 29


constructed a refuse incineration plant in 1964. In 1988, we introduced a new technology from LAB. S. A. in France, which treats dedusting and toxic gas absorption simultaneously. This technology is called Electrodynamic Venturi (EDV) Process. 2. PROCESS DESCRIPTION This process consists of the following units; (1) Dedusting unit Flue gas is fed to the top of Dedusting Column from a refuse incinerator, where the flue gas is quickly cooled down and comparatively large particles of dust and gaseous pollutants such as HCl and HF are removed by contact with circulating water sprayed by LAB-G nozzles. Effluent from the bottom of this Dedusting Column is circulated to the top of this Column by a water circulation pump. A part of circulating water is withdrawn and is fed back after sludge removing via Hydrocyclone and Thickener, and the wastewater contains the sludge is sent to Wastewater Treatment System. This circulating water is injected with hydrated lime milk as an absorbent and thus its pH value is controlled to be 1.5 - 2.5. (2) Venturi dust collector unit From the Dedusting Column, the flue gas is introduced to Venturi-type Dust Collector. In this equipment, small particles of dust and water mist which is unable to be removed in previous dedusting, are removed. At both inlet and outlet of this Venturitype Dust Collector, LAB-F nozzle is equipped which were developed by LAB.S.A. The dust is covered by condensate through adiabatic expansion and collected by sprayed water which is circulated via Circulation Tanks installed at inlet and outlet of this Venturi-type Dust Collector respectively. (3) Absorber unit From the Venturi-type Dust Collector, the flue gas is fed to lower part of Absorber where gaseous sulphur oxides are removed by contact with circulating water sprayed through LAB-G nozzles. And here the gas can be dehumidified simultaneously, if the circulating water is cooled through a cooling tower. It is effective to prevent white plume exhausting from the Stack. (4) Electrofiltering module unit Flue gas saturated with water from the Absorber is introduced to the following Electrofiltering module via Mist separator where entrained mist is removed. The Electrofiltering module is one of venturi and it removes very small particles of micronReedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 30


size(organic and inorganic chlorine compounds, heavy metals, etc.) which are contained in the flue gas. The small particles are collected by the filtered water film by means of electromagnetism. (5) Chemical dosing unit Hydrated lime is supplied in powdered form to Lime Silo by lorries. This hydrated lime is fed to a desolving tank where it is adjusted as slurry of concentration of approx. 5 10%, and after that it is injected into circulating water of the Dedusting Column. Further caustic soda of approx. 10% concentration is injected into circulating water of the Absorber. 3. SYSTEM FEATURES This process has the following advantages; (1) Compact, simple and small space required This process has two functions, that is, dust collection and absorption of gaseous pollutants such as HCl, SOx, HF. This process is compact and simple compared with one which treats functions separately. (2) LAB-G nozzle for slurry LAB-G nozzle developed by LAB. S. A. has an original structure which is suitable for a high density slurry with less blockage, erosion and damage. (3) Low chemical cost This process uses hydrated lime or limestone as an absorbent. The chemical cost is very low, approximately one third that of the conventional process, which uses caustic soda. (4) High small-particulate collection efficiency This process effectively collects small particulates of micron size including organic or inorganic chlorine compounds and heavy metals in the last unit, i.e., Electrofiltering modules. (5) No heavy metal in the effluent This process does not discharge any metals in the effluent and so it will be suitable for the stricter effluent limits of the near future. We are very glad if this EDV TYPE FLUE GAS TREATMENT SYSTEM would be of service for worldwide clean air protection.


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Fig.l EDV PROCESS


NIPPON SHOKUBAI'S Catalytic Incineration System1. Principle of Catalytic Incineration System The catalytic incineration method is to convert exhaust-gases into harmless and odorless by complete catalytic oxidation. Basic reaction scheme is expressed as follows; CmHn + O2 -> CO2 + H2O + Reaction Heat On the contrary, in the direct incineration system, exhaust-gases are burnt up in direct contact with a burner flame at higher temperatures of 700~900 deg.C. If a catalyst is used in this process, its excellent catalytic performance will bring about the same effect with that of the direct system at far lower temperatures of 200 ~ 400 deg.C.Reedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 32


2. Basic System The exhaust-gas containing organic compounds is sucked into the heat exchanger for preheating, and further heated in the gas heater before entering into the reactor. After the exhaust-gas is decomposed and purified by the catalyst in the reactor, treated gas is recycled into the heat exchanger to recover the reaction heat and finally discharged from the stack into the atmosphere. Depending on the contents and other conditions of exhaust-gas and the design of heat exchanger, the system provides an energy-saving operation which decreases or does not require auxiliary fuels. 3. Excellent Features of Catalytic Incineration System for Exhaust-Gas Treatment Among NIPPON SHOKUBAI's waste gas control systems, the catalytic incineration system employing catalyst of NIPPON SHOKUBAI's own development provides complete oxidation of pollutants and odorous substances at low temperatures converting them harmless and odorless. It has many excellent features as anti-pollution and energy-saving equipment. - Most suitable design - Low Running Cost - Perfect Treatment - Easy Operation 4. Wide Range of Applications Application - Paint and Ink Manufacturing - Solvent, Adhesives and Synthetic Resin Manufacturing - Chemical Manufacturing - Food Manufacturing - Industrial Wastes Handling - Odor Substances Handling etc.


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An Organic Halogen-Gas Purification System: The "HALOCAT" Catalytic-Incineration Exhaust-Gas Treatment Apparatus1. Introduction This exhaust gas treatment system provides the effective purification of the organic exhaust gas containing halogenated organic compounds by employing catalysts of Nippon Shokubai's own developed (STH-catalyst). Organic exhaust gas containing halogenated organic compounds can be decomposed by catalytic incineration and is converted into CO2, H2O and hydrogen halogenide. Then the hydrogen halogenide is neutralized by alkalied solution in the scrubber. Therefore the above-mentioned exhaust gas can be purified without generating hazardous exhaust gas and waste water.

2. Outline of this system


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3. Excellent feature of this system 1) Organic exhaust gas even containing halogenated organic compounds can be converted effectively into harmless substance. 2) Low running cost. 3) Purification of various kinds of halogenated organic compounds at low temperature. 4) No hazardous waste water is generated. 5) No hazardous by-product such as CO and halogen gas is generated. 6) As the catalyst is a honeycomb form, the pressure drop thereof is low. 7) A catalyst to be used keeps its stable effect for a long span of life-time. 8) Easy operation (can be operated with an automatic control requiring no manpower) and easy maintenance. 4. Purification efficiency of chlorinated organic compounds


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Exhaust Gas Treatment Equipment THE FLUE GAS TREATMENT SYSTEM OF THE MUNICIPAL SOLID WASTE INCINERATION PLANT 1. Introduction The exhaust gas generated from the incineration of municipal solid waste contains harmful substances that cause air pollution, such as dust, acid gases (SOx, HCl, NOx) and heavy metal particles (Pb, Zn, Cu, etc.). This device removes wide range of these harmful substances with high efficiency. 2. Process outline The exhaust gas from the municipal solid waste incinerator is cooled to a temperature of 180 to 200 deg. C by the gas cooler, and then enters the mixing chamber located at the inlet of the bag filter.Reedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 36


Filtration agency and hydrated lime transported by air from those silos are injected into the mixing chamber. When mixed with the exhaust gas, the hydrated lime reacts with hydrogen chloride and sulphur oxides, forming solid matter, which is collected by the bag filter. These chemical reactions are as follows: 2HCl + Ca(OH)2 -> CaCl2 + 2H2O SOx + Ca(OH)2 -> CaSOx + H2O The surface of the bag filter is also coated with filtration agency and hydrated lime, and this coating effectively collects dust and heavy metal particles. Fig. 1 shows the flowchart of exhaust gas treatment system. Fig. 1 Flowchart of exhaust gas treatment system.

3. Process features 1) The device uses dry-type processing which does not affect the exhaust gas temperature directly. Therefore, no corrosion or dust adhesion trouble occurs in the equipment. 2) The filtering effect of the filtration agency and hydrated lime prevents clogging of the filter cloth, providing stable plant operation without an increase in the filtering pressure loss. 3) The filtering effect of the filtration agency and hydrated lime removes dust and microscopic heavy metal particles effectively. 4. Processing capacity 1) Gas volume : no limitation 2) Gas temperature :160 to 220 deg.CReedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 37


5. Application range This device is designed mainly for the treatment of exhaust gas generated by the incineration of municipal solid waste. However, it can also be used to process gases produced from various types of furnace. 6. Performance measurement result Table 1 shows an example of performance measurement. Table 1 Example of performance measurement


NKK LIMAR - Bag System (Dry type)1. Introduction The system is used for removing hydrogen chloride (HCl) and sulfur oxides (SOx) contained in the flue gas. Slaked lime in the powder form is injected into the flue gas to cause contact reaction with HCl and SOx. The system is further provided with bag filters. As the flue gas passes through the dust layers created on the surface of bag filter cloth, unreacted slaked lime reacts with HCl and SOx contained in the flue gas, resulting in a very high removal rate. The reaction formula is given below. Ca(OH)2 + 2HCl -> CaCl2 + 2H2O 2. Process Flow


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Since slaked lime is injected in the powder form, the system simple.

According to the flow described above, HCl can be removed as low as 40 ppm (in terms of 12% O2), but when removing HCl to less than 40 to 25 ppm (in terms of 12% O2), reaction assistant agent has to be injected together with slaked lime as shown in the figure below:

3. Characteristics (1) Equipment is simplified. (2) Lowering the inlet flue gas temperature of bag filter permits higher removal efficiency. However, when the temperature drops below 140 degrees C, low temperature corrosion is generated in the ducts and casing. Therefore, the system should be operated at temperatures above 150 degrees C to prevent the corrosion. (3) The reaction assistant agent which would be injected in order to raise the reaction efficiency, is an extremely porous particles so as to promote the depositing of reaction products on the bug filter cloth dust layers. This arrangement also promotes better permeability and it also aids in increasing the chances of contacting unreacted slaked lime contained in the reaction products.Reedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 39


Relation between reaction temperature, Ca(OH)2 ratio and HCl removal efficiency 4. Results


NKK LIMAR-Bag System (Semi-Dry Type)1. Introduction The system is used for removing hydrogen chloride gas (HCl) and sulfur oxides (SOx) from flue gas to a low concentration of 20 ppm, respectively (in terms of 12% O2). Slaked lime is dissolved in water, and the slurry is refined with an atomizer for injecting into flue gas. HCl and SOx contained in the flue gas are dissolved in droplets containing slaked lime, reacts with slaked lime in the droplet, forms calcium chloride (CaCl2), and stabilizes as solid salt. In the next instance, solid salt is completely dried and formed into a spherical porous reaction products. The unreacted slaked limeReedited by: Environmental Industry Development., JSC No 42/117, Thai Ha str., Hanoi. 40


proceeds to slowly react with HCl and SOx contained into the flue gas. This reaction occurs at bag filters. The reaction process is shown in the figure below. Electronic microscopic photos of reaction products are also shown below. Reaction Process

2. Process Flow


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Slaked lime is atomized into flue gas by dissolving it in water and forming a slurry.

3. Characteristics (1) Since the system uses low cost slake lime and high reaction efficiency, the operating cost is low. (2) Since secondary reaction is present by the use of bag house, a very high removal efficiency is obtained. This is made possible by the porous particles of reaction products captured at the bag filter. As the flue gas slowly passes through the reaction product particles and the dust layers on the bag filter cloth, the chances of unreacted slake lime reacting with HCl and SOx are increased. 4. Removal Efficiency HCl removal efficiency


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Example of measurement


ABB FILSORPTION SYSTEM for controlling toxic elements in flue gas1. ABB Filsorption System ABB Filsorption System stands for simultaneous Filtration and Sorption of flue gases and their contaminants by means of a ABB Fabric Filter acting as both filter and chemical reactor. The system can for example be installed after wet scrubbers in Waste to Energy plants for the final removal of dioxins and heavy metals. It also acts as a polishing filter for dust and acidic gases. The ABB technique with injection of a mixture of lime and activated coke or carbon upstream of the fabric filter for absorption of these contaminants is a safe and proven technology which gives extremely low emission levels. ABB pioneered the Filsorption technology and has now more than 15 years comprehensive operating experience from extremely tough and demanding applications. ABB has also developed the technique of feeding, conveying, collecting and handling the Filsorption product to an impressive level of reliability. With plants in commercial operation for more than one decade, ABB has gained extensive experience from installing Filsorption Systems. Over 90 fabric filter installations in Waste to Energy plants clean safely and effectively more than 11,000,000 m3 of flue gas every hour.


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Pollutants in flue gases

2. The fabric filter The fabric filter used in this application is the wellproven Optipulse filter. This application has a uniform sorbent distribution over the bags, producing a constantly low dust emission. In the Filsorption System the fabric filter acts as a fixed-bed reactor where the flue gases pass the absorbent layer formed on the bags. The filter bags are cleaned by means of compressed air pulses which are directed down through the bag openings. The compressed air expands the bag with a stepped acceleration so that a fraction of the dust on the outside of the bag is detached in a carefully controlled manner. 3. The technology Activated coke or carbon with its high surface area is known to be effective in collecting high molecular weight organic and mercury compounds. In the Filsorption System a mixture of lime and activated coke or carbon is carefully distributed in the gas stream by means of ABB compact reactor. The even distribution over the filter area provides extensive contact between gas and sorbent, which is a prerequisite for efficient cleaning. The lime enables the removal of acidic gases such as HCl, SO2 and SO3 in addition to the removal of mercury and organics by the coke/carbon. The excellent collection characteristics of the fabric filter ensures extremely low particulate emission levels. The end product from the Filsorption System is normally fired in the waste furnace where the lime acts as an absorbent contributing to a pre-separation of acidic gases from the flue gas. Other methods are glassification or for neutralization of waste water.


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The Filsorption system - reactor and filter - is designed with vertical or very steep walls in the ducts and hoppers, making the dust discharge very effective. Consequently all problems with dust deposits and sticking dust are eliminated. 4. Performance By using the ABB Fabric Filter as a fixed bed absorption reactor the total particulate emission is kept extremely low. This also allows the use of a fine-grained coke or carbon while still maintaining a very low dust emission. The fine-grained coke or carbon creates a very large contact area with excellent absorption for a given amount of coke or carbon. The ABB Fabric Filter offers an optimal collection capacity of sob-micron particles thereby ensuring very low emission levels of heavy metals. The even distribution of sorbent over the bag surface is an inherent feature of the ABB design - a small deficit of sorbent anywhere on the surface will decrease local flow resistance. This in turn leads to increased gas flow and due to the continuous feed of sorbent, to immediate local cake repair. In this respect, the system is selfbalancing and automatically assures optimum sorbent/dust cake contact with the flue gases. Results from Installation


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Waste Ozone Decomposition SystemThis system efficiently decomposes ozone in the waste gas with the catalyst composed of metallic oxide. The catalyst is wear resistant and free from hazards of combustion and explosion. As the ozone decomposing reaction using the catalyst is performed even at low temperatures, the system can decompose the waste ozone (low to high concentration) for a long time at low cost. 1. Features 1) Compact size. 2) Low and economical running cost. 3) Simple operation and easy maintenance. 4) Long catalyst life. 5) Excellent ozone decomposing complying with low concentration. 6) A large opening ratio and low pressure drop due to honeycomb structure. 2. Applications Air cleaner (room, car and garbage deodorization) Ozonizer Ozone sterilizer High-concentration ozone treatment Semiconductor manufacturing process Water supply and sewage water treatment Other fields requiring waste ozone treatment 3. System Flow


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Quench towerThe Quench tower is designed and engineered for cooling high temperature exhaust gases from incinerator, melting furnace, drying furnace, etc. Exhaust gas from high temperature sources is cooled down with water vapor to the saturation temperature of the gas by Quench tower. The Quench tower is used as a pre-cooler for scrubbers, electoststic precipitators, etc. Technical Information Specification : The Quench including spray headers and spray nozzles are made of corrosion resistant materials, such as lining carbon steel, type 316L stainless steel, Hastily-C. Uniform water spraying is made by special spray nozzles. Both horizontal flow type and vertical flow type are available. Advantages : - No dioxins is generated in the Quench tower. - The Quench tower can be as a simple scrubber. - For corrosion resistance, lining type and wetted surface type are available.


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air pollution control technology japan

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