JP4648794B2 - Gasification gas purification method and apparatus - Google Patents

Description

  The present invention relates to a method and apparatus for purifying a pyrolysis gas obtained by pyrolyzing combustible waste such as waste tires and waste plastics into fuel gas.

  In general, incineration or landfill disposal methods are generally used for waste treatment. However, in order to effectively use the energy of waste in recent years, the waste is thermally decomposed to combustible gas, tar / light oil, and scattering. A method of obtaining a pyrolysis gas containing char, purifying the pyrolysis gas and using it as a fuel gas has been implemented.

  For example, in Patent Document 1, a carbonization gas (pyrolysis gas) obtained by dry distillation (pyrolysis) of copper-containing organic waste such as shredder dust is mixed with a coke oven gas, and the mixed gas is purified. And the method of utilizing as fuel gas is disclosed. However, when this method is applied to the treatment of wastes rich in volatile matter such as waste plastics, tar in the gas precipitates and solidifies during gas cooling and becomes wax to adhere and block in pipes of coke oven gas refining equipment etc. This was an obstacle to long-term driving.

  For this reason, it is common practice to wash the gas with water or the like to remove tar, but as described in Patent Document 1, the gas is washed with the waterworks of the steelworks, and the drainage is discharged to the waterworks of the steelworks. In the case of treatment with a treatment facility (activated sludge method), the activity of activated sludge may be hindered by the influence of heavy metals contained in waste water, harmful organic compounds, and the like.

On the other hand, as described in Patent Document 2, there is a method in which organic waste is gasified and then reacted with oxygen and water vapor to reduce tar and light oil in the gas by a reforming reaction. However, if the reforming temperature is about 1100 ° C. or higher, the high-calorie component of the hydrocarbon gas such as methane in the gas is also reduced in molecular weight to H ₂ and CO by thermal decomposition, and the gas calorie is reduced. When gas calorie falls, the range of use as gas becomes narrower. On the other hand, if the reforming temperature is about 1000 ° C. or less, tar and light oil remain in the gas, which is not sufficient.

  Moreover, since the chlorine content contained in the waste is volatilized as hydrogen chloride in the gas, there is a risk of corrosion in the coke oven gas refining equipment and other gas utilization destinations. Furthermore, the chlorine content in the waste causes generation of harmful organic chlorine compounds such as dioxins.

  In this way, particularly when volatile-rich waste is pyrolyzed and gasified, if it is combined with the coke oven gas without performing sufficient gas purification treatment on the pyrolysis gas, tar contained in the gas, Various problems are caused by organic chlorine compounds such as light oil and dioxins.

On the other hand, Patent Document 3 discloses a method of gasifying organic waste and recycling the residue in a blast furnace and a coke oven, but tar, ash, and chars that become heavy metals and residues are: Since it contains a lot of organic chlorine compounds such as heavy metals and dioxins, it is not preferable to use this as a raw material for other production facilities.
JP 2003-39056 A JP 2004-238535 A JP 2001-221415 A

  The problem to be solved by the present invention is that when high-calorie and volatile-rich waste such as waste tires and waste plastics is gasified to obtain high-calorie gas, tar, light oil, dioxin contained in the gas It is an object of the present invention to appropriately remove such impurities and to join the obtained gas to an existing coke oven gas line at a steel works so that it can be purified without any problems.

  Another problem is to effectively use the amount of heat of char and tar generated by thermal decomposition and to prevent environmental pollution caused by organic halogen compounds such as heavy metals and dioxins contained in char and tar.

In the gasification gas purification method according to the present invention, combustible waste is gasified in a pyrolysis furnace, the pyrolysis gas is reacted with oxygen and water vapor in a reforming furnace, and the reformed gas is reformed. In the gasification gas purification method to obtain fuel gas by refining, the reformed gas is introduced into the first gas cooler, and the gas temperature is cooled to 90-70 ° C. below the adiabatic saturation temperature by water spray or in-liquid combustion. Then, after the dioxin concentration of the obtained gas was reduced below the standard value (0.1 ng-TEQ / m ³ N (oxygen concentration 12% converted value)), the dry main attached to the existing coke oven at the steel works In the coke oven gas line, and the condensate / collected product of the first gas cooler is discharged and water is separated from the condensed / collected product. The resulting char, tar, light oil, etc. The combustible material is returned to the pyrolysis furnace and pyrolyzed again for gasification. And it is characterized in the Turkey allowed.

Further, the gasification gas purification apparatus according to the present invention reforms a pyrolysis furnace for pyrolyzing and gasifying combustible waste, and reacting the pyrolysis gas generated in the pyrolysis furnace with oxygen and water vapor. In a gasification gas purification apparatus comprising a reforming furnace and purifying the reformed gas generated in the reforming furnace to obtain a fuel gas, the gas temperature is below the adiabatic saturation temperature by spraying the reformed gas with water or in-liquid combustion. The first gas cooler that cools to 90 to 70 ° C. is provided, and the gas emitted from the first gas cooler is dioxin concentration as a reference value (0.1 ng-TEQ / m ³ N (oxygen concentration 12% Conversion value)) After the following, after the refinery by joining the coke oven gas line with the dry main attached to the existing coke oven in the steelworks, the condensed and collected material of the first gas cooler is discharged And char, tar, light Combustibles and a mechanism for returning the separated pyrolysis furnace etc., further, separate combustibles and pyrolyzed again is characterized in the provision of the Ru Organization is gasified.

According to the present invention, the pyrolysis gas obtained by pyrolysis of combustible waste is pretreated to reduce the content of char, tar, light oil, H ₂ S, HCl, HCN, dioxins, etc. Even when wastes rich in volatile components are gasified, the obtained gas can be refined without problems by joining the existing coke oven gas line at the steelworks. Therefore, the existing facilities in the steelworks can be used effectively, and the gas purification cost can be reduced.

  In addition, the combustible material such as char, tar, and light oil separated from the condensed / collected product of the first gas cooler is returned to the pyrolysis furnace and again pyrolyzed to gasify, or the pyrolysis furnace By using it as a fuel to supply a heat source, it is possible to effectively use the amount of heat generated by pyrolysis, such as char and tar, and to prevent environmental pollution caused by heavy metals contained in char and tar, and organic halogen compounds such as dioxins. can do.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a configuration diagram showing a gasification gas purification apparatus according to the present invention.

  First, a gasification process and a combustion exhaust gas treatment process will be described. In the apparatus shown in FIG. 1, combustible waste rich in volatile matter such as waste tires and waste plastics is gasified. The target object is crushed to a certain size or less in advance by the crusher 1 so that the pyrolysis gasification is completed within the residence time of the pyrolysis furnace 2 and then put into the pyrolysis furnace 2. At that time, depending on the combination of the target and the furnace type, unsuitable materials such as metals and incombustible materials may be included. In such cases, unsuitable materials are removed by magnetic sorting, wind sorting, manual sorting, or the like.

  The waste put into the pyrolysis furnace 2 is heated to the pyrolysis temperature by the heat obtained by burning external fuel or the heat obtained by partially burning the waste and consuming its own energy. Generate gas. As a furnace type, a rotary kiln is used in the embodiment, but a shaft furnace, a fluidized bed furnace, and the like can also be used. That is, a method of pyrolysis gasification by external indirect heating such as an external heating kiln or two-column fluidized bed furnace, or a partial combustion method of pyrolyzing waste by partial combustion such as a shaft furnace or fluidized bed furnace Is available.

  In addition, if necessary, wastewater generated in the pretreatment of waste, the purification process of pyrolysis gas, and the like is sprayed on the pyrolysis furnace 2 or the combustion furnace 16 that supplies heat to the pyrolysis furnace 2 to be dried and incinerated. You can also.

  In the case of gasification by external indirect heating, combustion exhaust gas for obtaining a heat source is not mixed on the pyrolysis gas side, so that the calorific value of the pyrolysis gas and the concentration of useful components can be kept high. However, since combustion exhaust gas for obtaining a heat source is generated in a separate system, a separate exhaust gas treatment is required as shown in FIG.

  As a method for treating the exhaust gas of another system, a secondary combustion furnace 3 is provided as necessary, and the temperature and residence time are ensured to a specified value or more to completely decompose dioxins and other unburned components. Further, in the secondary combustion furnace 3, wastewater generated in a pretreatment of waste, a purification process of pyrolysis gas, or the like can be sprayed to be dried and incinerated. As the secondary combustion furnace 3, a furnace shell is often made of a steel plate or a heat transfer tube, and a refractory is lined on the inner surface. In order to promote the decomposition of dioxins, the temperature in the secondary combustion furnace 3 is maintained at a constant level (850 ° C., preferably 900 ° C. or more). The temperature in the secondary combustion furnace 3 is maintained by adjusting the amount of combustion air or dilution air so that the temperature indication value of a thermometer provided in the furnace becomes a certain target value.

  The gas completely burned in the secondary combustion furnace 3 is introduced into the heat exchanger 4 to recover waste heat. Examples of the heat exchanger 4 include a boiler, a hot water generator, an air preheater, and the like.

  When the waste heat is recovered by the boiler, the obtained steam can be converted into electric power by driving the turbine, and because of the reforming reaction in the stirring gas in the pyrolysis furnace 2 and the reforming furnace 13 described later. It can be used as a water vapor source. The boiler is a natural circulation water tube boiler, and the boiler wall is also used as a heat transfer surface to improve heat recovery efficiency. When the object to be treated is waste containing chlorine and sulfur, the melting point of ash tends to be lowered due to the influence of chlorine and alkali metals contained in the waste. Therefore, there is a possibility that dust adheres to the internal heat transfer tube and heat transfer efficiency is lowered or the boiler is blocked. Therefore, in order to prevent adhesion, a steam-driven soot blower is often provided.

  On the other hand, when waste heat is recovered with a hot water generator, residual heat can be used in nearby facilities. Further, when waste heat is recovered by the air preheater, the heated air can be used as combustion air for pyrolysis in the pyrolysis furnace 2, combustion air in the combustion furnace 16, and the like.

  The heat-recovered exhaust gas is sprayed with water in the exhaust gas temperature-decreasing tower 5, and the gas temperature reaches a temperature (200 ° C. or less) at which dust can be removed by a dust remover 6 (bag filter, electrostatic precipitator, etc.) installed downstream. Is reduced. When a bag filter is used for the dust remover 6, slaked lime or activated carbon can be blown by the blowing device 7 on the dust remover 6 entry side in order to adsorb the hydrogen chloride gas and dioxin contained in the gas.

  Although the exhaust gas is sucked by the induction fan 8, the induction fan 8 is generally installed on the outlet side of the dust remover 6. Thereby, dust troubles, such as dust adhering to the impeller of the induction fan 8 and weight balance breaking, can be prevented.

  The gas whose pressure has been increased by the induction fan 8 is heated to 180 ° C. to 250 ° C. in the exhaust gas reheater 9 (steam indirect heat system, external fuel reheating system, etc.) as necessary, and then the catalyst. The gas is passed through the reaction layer or the activated carbon packed bed 10 and the dioxins and NOx in the gas are decomposed and adsorbed. When NOx is decomposed by the catalyst, high NOx decomposition performance can be obtained by blowing ammonia upstream of the catalyst.

  The exhaust gas gas-treated by the dust remover 6, the catalyst, etc. is diffused from the chimney 11 to the atmosphere. At the chimney 11, an exhaust gas analyzer is installed to monitor the amount of NOx, SOx, HCl, and other air pollutants in the exhaust gas. Emissions of air pollutants inside can be kept below the specified value.

  Waste-derived dust is collected from the secondary combustion furnace 3, the heat exchanger 4, the exhaust gas temperature reducing tower 5, and the dust remover 6. The collected dust is collected and mixed with chemicals (chelates) in the ash treatment facility 12 and treated as waste, such as disposal at the final disposal site after taking measures to prevent elution of toxic substances such as heavy metals. . Further, when the concentration of heavy metals such as lead and zinc in the fly ash is high, heavy metals can be extracted, concentrated and recycled.

Next, the purification process of the pyrolysis gas produced | generated by the gasification process is demonstrated. As described above, in the apparatus shown in FIG. 1, wastes rich in volatile components such as waste tires and waste plastics are gasified in the pyrolysis furnace 2. A pyrolysis furnace 2 shown in FIG. 1 is an indirect heating type dry distillation kiln and pyrolyzes and gasifies in an oxygen-free state. The pyrolysis products include a liquid component that condenses when cooled to room temperature, a gas component of a gas body even at room temperature, and a solid component as a pyrolysis residue. In the case of a dry distillation kiln, the gas components include combustible H ₂ , CO, and CH ₄ as main components, and in addition, combustible C ₂ to C ₄ hydrocarbon gas, non-combustible CO ₂ and N ₂ are included. The liquid component includes an oil component and condensed water. Oil has distribution from heavy (tar) to light (light oil), and condensed water contains acidic components such as HCl and H ₂ S and NH ₃ . The solid component includes a carbon residue (char) obtained by carbonizing an organic substance into a fixed carbon main body and an incombustible residue mainly including an inorganic component.

  Since combustible waste rich in volatile content such as waste plastic is thermally decomposed in a low temperature range, the pyrolysis product has many oil components such as tar and light oil, and not many gas components. In such a case, the reforming furnace 13 is provided for the purpose of converting the oil component into gas and increasing the gas yield. In the reforming furnace 13, pure oxygen is introduced at a high flow rate through a nozzle, the temperature is increased by heat generated by partially burning the combustible component, and the oil component is thermally decomposed to be converted into gas and char. . At that time, by mixing water vapor with the introduced oxygen, char generation suppression by water gasification reaction, improvement of gasification rate, strengthening of stirring in the furnace, and uniform reaction temperature are achieved.

The reforming temperature is generally in the range of 700 to 1000 ° C., the gas temperature at the furnace outlet is measured, and the amounts of oxygen and water vapor are adjusted so that the temperature becomes a target value. By this reforming, tar and light oil are converted into gases such as CO, CO ₂ , H ₂ , CH ₄ , H ₂ O and char (soot). Setting a high reforming temperature increases the reforming efficiency, reduces tar and light oil content, and also reduces trace amounts of organic halogen compounds such as dioxins, but at the same time, hydrocarbon gases such as methane, ethane, and propane Is also decomposed into CO and H ₂ , so that the gas calorie decreases and the gas volume increases.

  Further, from the viewpoint of thermal efficiency, the steam used for reforming is desirably steam obtained by heat recovery in the heat exchanger 5 (boiler) described above, and the temperature of the steam is preferably higher (200 ° C. or higher, Preferably 400 ° C. or higher). However, when the temperature is too high, corrosion occurs in the boiler heat transfer tube, so that the steam temperature is preferably about 400 to 450 ° C. However, this is not the case when external fuel is used for the production of steam.

  The hot reformed gas is rapidly cooled by spraying water in the precooler 14 (first gas cooler). Since the reformed gas has a high gas temperature and is unsaturated in water, the sprayed water is instantly vaporized and loses 640 kcal of latent heat of evaporation per kg of water. As a result, the gas is rapidly cooled and cooled to a temperature (70-90 ° C.) slightly below the adiabatic saturation temperature. As the gas temperature decreases, tar having a high boiling point is condensed, and fine char is trapped in water droplets by water spray. As a result, the char and tar are collected at the bottom of the precooler 14 together with the non-evaporated spray water and flow out to the tar decanter 15 (separator). The properties of the collected tar change depending on the water temperature. That is, the tar becomes heavy when the temperature is high, and light when the temperature is low. When tar cools, its viscosity rises and hardens, making handling difficult, and the specific gravity of tar and water is also affected by temperature. Normally, it is experientially adjusted to a cooling temperature of 80 to 85 ° C. and appropriately maintained by steam tracing or the like to maintain the temperature. In the precooler 14, the reformed gas may be rapidly cooled not by water spray but by submerged combustion.

The pyrolysis gas contains acidic gases such as HCl (hydrogen chloride), H ₂ S (hydrogen sulfide), HCN (hydrocyanic acid), NH ₃ (ammonia), alkali salt dust, and water-soluble organic components. Normally, water is acidic with HCl. In order to prevent acid corrosion of the equipment, alkali is added to the spray water (makeup water) of the precooler 14 to adjust the pH, and in order to avoid concentration, it is appropriately blown and diluted. As the alkali, caustic soda, magnesium hydroxide, slaked lime milk, ammonia water or the like is used. In order to appropriately adjust the alkali addition amount, the pH of the circulating water is measured, and the pH is a target value (preferably 5 to 9). ). In addition, when there is a coke oven in the vicinity of the facility, the operation cost can be reduced at low cost by using the low temperature water produced as a by-product in the coke oven as the spray water. Further, when the reforming temperature is high, tar is reduced and char is generated, so that the ratio of tar to char becomes char rich.

  By cooling with the precooler 14, most of the harmful substances (dioxins, heavy metals, etc.) contained in the reformed gas aggregate and become liquid or solid, and tar and char settle in the water at the bottom of the precooler 14 in a turbid state. ,accumulate. However, some of the gas exiting the precooler 14 is scattered as a mist state or a gas state. As a method for reducing such scattering, there are measures such as spraying spray water at a high pressure and reducing the particle size of mist.

  As described above, the char tar collected in the water by the precooler 14 flows out into the tar decanter 15 together with water. Usually, tar has a specific gravity heavier than water and can be separated by scraping the tar that has settled at the bottom of the tar decanter 15. In addition, when the reforming temperature is raised to become char-rich, char is likely to grow in a lump with tar, and the specific gravity is lightened. good.

  Tar and char separated and recovered from the aqueous phase by the tar decanter 15 and the fixed carbon main body in the pyrolysis residue discharged from the pyrolysis furnace 2 are combustible and can be used as fuel. However, it contains substances that require environmental care, such as chlorine, ammonia, dioxins, and is not suitable as a fuel for production facilities.

  Therefore, in this invention, it utilizes as a fuel of a combustion furnace comprised as a waste incinerator, ie, the fuel or raw material for the pyrolysis furnace 2. Specifically, 1) If the pyrolysis furnace 2 is an indirect heating type as shown in FIG. 1, it is used as a fuel for the combustion furnace 16 that is a high-temperature heat source or as a raw material for the pyrolysis furnace 2, or 2) part If it is a combustion system, it can be recharged into a pyrolysis furnace and thermally decomposed by partial combustion. Thereby, tar char can be effectively recovered as a heat source or gas. Thus, by using by-products as fuel, it is possible to reduce part of the external fuel and waste for the pyrolysis furnace and increase the amount of gas obtained. As a method for separation from the aqueous phase, techniques such as pressure levitation, filter press, and centrifugal separation can be used in addition to a decanter.

  The water from which the char tar has been separated is circulated and used, but in order to prevent the concentration of salts, etc. and the resulting corrosion of the equipment, it is appropriately extracted and blown. Blow water contains solid matter (SS), COD, oil (n-HEX), dioxins, etc., and thus is appropriately discharged and discharged.

  When dioxins are not sufficiently removed by gas cooling and gas cleaning by water spraying of the precooler, a primary cooler 17 (second gas cooler) is installed in the downstream and further cooled to 40 ° C. or lower. Reduce gas temperature. When the gas temperature is lowered, the gas phase water vapor and light oil rich tar are further liquefied by condensation, and the dioxins are dissolved in the oil layer and separated from the gas phase. As a result, in the primary cooler 17, condensed water and tar are separated and recovered, and at the same time, dusts such as dioxins and char can be removed from the gas phase. As an apparatus method of the primary cooler 17, an indirect heat exchange method or a water spray method can be adopted. In the indirect heat exchange system, cooling water of about 15 ° C. to 30 ° C. is allowed to flow through a heat transfer tube installed in the primary cooler 17 to indirectly cool the gas. In the water spray method, cooling water of about 15 ° C. to 30 ° C. is sprayed in the primary cooler 17 and the gas is cooled by directly exchanging heat between the low temperature water and the gas.

  In the condensed water, the acidic gas component contained in the gas dissolves and becomes strongly acidic and corrosive. Therefore, an alkali chemical is introduced and neutralized so that the pH is 5-9. It is preferable to use caustic soda and aqueous ammonia as the alkali. For this reason, condensed water added with alkali is circulated on the inner wall of the primary cooler 17 and sprayed into the apparatus, and the condensed water is washed away to prevent the condensed water from becoming acidic. In addition, this water spray prevents the light tar component condensing at the same time from growing on the wall and heat transfer tube, and also has the effect of capturing and removing dust and tar mist. As the alkaline water (neutralizing agent) used in the primary cooler 17, the operation cost can be suppressed at low cost by using the water that is by-produced in the coke oven.

  Here, when there is a large amount of char and tar mist remaining in the gas at the outlet of the precooler 14, an electric dust collector (not shown) is installed between the precooler 14 and the primary cooler 17, and dust such as char or light oil mainly It is also possible to remove tar mist and water vapor mist. As a result, the concentration of dioxins in the gas is further reduced, the load of dusts and oils on the downstream primary cooler 17 is reduced, and troubles such as adhesion and blockage on the inner wall can be easily prevented.

  In the embodiment, as shown in FIG. 1, an electrostatic precipitator 18 is provided on the downstream side of the primary cooler 17 to collect particulate matter such as light oil-based tar mist contained in the gas. Dioxins are also captured and the concentration of dioxins in the gas is reduced.

  The obtained gas is sent to a coke oven gas purification facility 24, which will be described later, by a blower 19 (gas exhauster). An activated carbon packed bed or an activated carbon moving layer 21 is provided on the downstream side of the blower 19, and the gas is contained therein. Dioxin is adsorbed by passing through. Here, activated carbon is activated coke or granular activated carbon. If the gas temperature is lower than the saturation temperature only by the temperature increase due to the pressure increase of the blower, and the condensation of light oil and moisture occurs in the activated carbon packed bed or the activated carbon moving layer 21 where it is easy to cool, the blower 19 and the activated carbon packed bed or activated carbon move. Between the layers 21, a steam indirect heat exchange type gas heater 20 is provided, and the gas temperature can be raised to a temperature at which the condensation can be prevented.

Through the above steps, the dioxin concentration in the gas is set to a reference value (0.1 ng-TEQ / m ³ N (converted value of oxygen concentration 12%)) or less. In the present invention, this cleaned gas is mixed with the coke oven gas (COG) refining equipment 24 of the coke oven 22 to use the existing infrastructure from gas delivery to gas use. Depending on the installation position of the equipment, the distance from the gas cleaning to the COG line may be long. In this case, the gas temperature decreased due to heat dissipation during the gas transfer, and the light oil component precipitated and solidified in the gas duct, causing problems such as duct blockage. For this purpose, after removing light oil and condensed water mist with an electric dust collector, the gas temperature is raised again, and the temperature at the gas supply destination is controlled to be equal to or higher than the condensation temperature of the light oil component.

  Prior to connection to the coke oven gas purification facility 24, impurities such as hydrogen sulfide and light oil are not sufficiently removed, and some chlorine-based gas such as hydrogen chloride remains. These impurities may cause corrosion at the gas application site, condensation / liquefaction of light oil components due to temperature decrease, gas line blockage due to precipitation of naphthalene, anthracene, etc., burner clogging, etc. difficult. Therefore, by using the existing desulfurization device (sulfur content and chlorine content removal) and light oil removal device (light oil scrubber) in the coke oven gas refining facility 24, the purity of gas purification can be increased and the above problem can be avoided.

  When merging into the COG line with the aim of using the coke oven gas refining equipment 24, it is preferable to use the dry main 23 which can use all of the COG refining functions and has a pressure close to atmospheric pressure.

  In the dry main 23, the gas generated in the coke oven 22 is sprayed and washed with water and the gas is cooled to separate tar and sludge from the gas. The gasification gas refined in the waste gasification furnace and gas purification equipment is mixed with COG in the dry main 23. In the dry main 23, tar and sludge contained in the COG are collected together with the low water and transferred to the low water decanter 25. In the low water decanter 25, the mixed liquid of the low water, tar and sludge is gravity settled due to the difference in specific gravity and separated into tar, low water and sludge. The separated tar is recovered and effectively used as a tar product. The recovered water is recycled.

  By-products (mixture of light tar, light oil, char and water) of the primary cooler 17 and the electrostatic precipitator 18 are separated into oil and water in the oil / water separation tank 26, and the oil is separated from the aqueous phase by the tar decanter 15. It is preferable to use it as a heat source in the pyrolysis furnace 2 or the combustion furnace 16 in the same manner as the separated tar and char. Further, the by-products of the primary cooler 17 and the electric dust collector 18 may be joined directly to the tar decanter 15 without going through the oil / water separation tank 26.

  On the other hand, since water contains a lot of harmful substances and cannot be discharged as it is, it is necessary to temporarily store it in the drain tank 27 and then perform water treatment. The activated sludge method is the most suitable water treatment method.

  In the present embodiment, the low water activated sludge treatment facility 28 for treating surplus water from the COG refining process joins the water and main waste water to be treated.

  However, wastewater generated during the cleaning process of the pyrolyzed waste gas contains heavy metals such as zinc and lead, various harmful organic compounds, especially organic chlorine compounds such as dioxins, cyanide compounds and benzonitrile. It is difficult to keep the activity high because the activated sludge is contained. Therefore, in order to join the existing low water activated sludge treatment facility 28 for efficient treatment, it is desirable to remove the inhibitory substance by pretreatment.

  As a pretreatment method, it is effective to apply any one or all of 1) SS separation, 2) coagulation sedimentation, and 3) aqueous distillation.

  SS separation is a technique for separating wastewater containing tar and SS (solid matter) by pressurized flotation or specific gravity difference. Aggregation precipitation is a technique in which the aqueous layer separated by SS separation is cooled, an alkali chemical is added, the pH is adjusted to 9.5 to 12.0, and heavy metals and the like are aggregated and precipitated. Aqueous distillation is a technique for removing nitrogen and ammonia by ammonia stripping of the aqueous layer separated by SS separation. By carrying out any or all of these treatments, the concentration of dioxins in water is set to 10 pg-TEQ / L or less.

  FIG. 2 is a block diagram showing another example of the gasification gas purifying apparatus according to the present invention. In the example shown in the figure, the gas heater 20 on the downstream side of the blower 19 and the activated carbon packed bed or the activated carbon moving layer 21 are omitted in the configuration shown in FIG. 1, and the gasification gas is directly joined from the blower 19 to the COG line. It is what I did. In the case where the concentration of dioxins in the gasification gas is low, the dioxins concentration can be reduced below the reference value also in this example, and the equipment is simplified.

  In the example of FIG. 2, the oil / water separation tank 26 in FIG. 1 is also omitted, and the condensed and collected products of the primary cooler 17 and the electric dust collector 18 are directly joined to the tar decanter 15 to simplify the equipment. That is, the oil (combustible component) of the condensate / collected matter of the primary cooler 17 and the electric dust collector 18 is separated by the tar decanter 15 and is heated similarly to the tar and char separated from the condensate / collected matter of the precooler 14. It is used as a heat source in the cracking furnace 2 or the combustion furnace 16.

It is a block diagram which shows the purification apparatus of the gasification gas which concerns on this invention. It is a block diagram which shows the other example of the purification apparatus of the gasification gas which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crusher 2 Pyrolysis furnace 3 Secondary combustion furnace 4 Heat exchanger 5 Exhaust gas temperature reduction tower 6 Dust remover 7 Blowing device 8 Induction ventilator 9 Exhaust gas reheater 10 Catalytic reaction layer or activated carbon packed bed 11 Chimney 12 Ash processing equipment 13 Reforming furnace 14 Precooler (first gas cooler)
15 Tar decanter (separator)
16 Combustion furnace 17 Primary cooler (second gas cooler)
18 Electric dust collector 19 Blower (Gas exhaust machine)
20 Gas heater 21 Activated carbon packed bed or activated carbon moving bed 22 Coke oven 23 Dry main 24 Coke oven gas purification equipment 25 Aqueous decanter 26 Oil / water separation tank 27 Drainage tank 28 Aqueous activated sludge treatment equipment

Claims (2)

Gasification of combustible waste in a pyrolysis furnace, reforming this pyrolysis gas by reacting with oxygen and water vapor in a reforming furnace, and purifying the reformed gas to obtain fuel gas In the method
The reformed gas is introduced into the first gas cooler, the gas temperature is cooled to 90 to 70 ° C. below the adiabatic saturation temperature by water spray or in-liquid combustion, and the resulting gas is dioxin concentration as a reference value ( 0.1 ng-TEQ / m ³ N (oxygen concentration 12% conversion value) or less, and then refined by joining the steel plant with the coke oven gas line with the dry main attached to the existing coke oven,
The condensed / collected material of the first gas cooler is discharged, the water is separated from the condensed / collected material, and the obtained combustible material such as char, tar, and light oil is returned to the pyrolysis furnace and pyrolyzed again. method for purifying the gasification gas, wherein the benzalkonium is gasified by. A pyrolysis furnace that pyrolyzes and gasifies combustible waste, and a reforming furnace that reforms the pyrolysis gas generated in the pyrolysis furnace by reacting with oxygen and water vapor, In a gasification gas purifier that purifies a gas and obtains a fuel gas,
A first gas cooler is provided to cool the reformed gas to 90-70 ° C. below the adiabatic saturation temperature by spraying with water or burning in liquid, and the gas emitted from the first gas cooler is dioxin concentration Is made below the standard value (0.1 ng-TEQ / m ³ N (oxygen concentration 12% conversion value)), and then refined by joining the steel plant with the coke oven gas line with the dry main attached to the existing coke oven. With
A mechanism for discharging the condensed / collected material of the first gas cooler and a mechanism for separating combustible materials such as char, tar, and light oil from the condensed / collected material and returning them to the pyrolysis furnace were further separated. combustibles pyrolysis again purified apparatus gasification gas, characterized in that a Ru Organization is gasified.

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