JP6695391B2 - Denitration and corrosion reduction methods for waste incineration equipment - Google Patents

Description

  The present invention mainly relates to a waste incinerator including a waste incinerator and a boiler, and to a method of reducing corrosion of a heat transfer tube of a boiler while reducing a discharge amount of nitrogen oxides.

  Conventionally, in order to reduce nitrogen oxides contained in the exhaust gas generated in a waste incinerator, a method of supplying a chemical such as urea into the furnace has been used. Further, in order to reduce the corrosion of the heat transfer tubes of the boiler that recovers the heat of the waste incinerator, a method of supplying a corrosion reducing agent such as a sulfur compound into the furnace is used.

  Patent Document 1 describes the use of an aqueous urea solution or an aqueous ammonia solution as a chemical for reducing the emission of nitrogen oxides.

  Patent Document 2 describes that a sulfur-containing compound such as ammonium sulfate is used in order to reduce corrosion of a heat transfer tube of a boiler. Patent Document 2 describes that the use of ammonium sulfate can further reduce the emission amount of nitrogen oxides. Further, in Patent Document 2, the concentration of NaCl gas or the concentration of KCl gas contained in the exhaust gas passing through the combustion chamber toward the superheater pipe (heat transfer pipe) of the boiler is measured, and the sulfur-containing compound is measured based on the measurement result of the concentration. It is described that the supply amount of is adjusted.

JP, 2002-136837, A JP, 2016-11813, A

  However, the method of Patent Document 1 can only reduce the emission amount of nitrogen oxides, and cannot reduce the corrosion of the heat transfer tube of the boiler.

  The method of Patent Document 2 can realize both reduction of nitrogen oxide emission and reduction of corrosion of the heat transfer tube of the boiler. However, in Patent Document 2, since the concentration of NaCl gas contained in the exhaust gas before being purified by a dust collector such as a bag filter is measured, the measuring device is easily contaminated and stable measurement is performed for a long period of time. Becomes difficult. Further, Patent Document 2 describes measuring the concentration of NaCl gas or the concentration of KCl gas, but does not describe measuring other chlorine compounds.

  The present invention has been made in view of the above circumstances, and its main purpose is to stably discharge nitrogen oxides over a long period of time with respect to a waste incinerator including a waste incinerator and a boiler. It is to provide a method of reducing corrosion (while causing a denitration reaction) and reducing corrosion occurring in a heat transfer tube of a boiler.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem and its effect will be described.

According to the viewpoint of the present invention, the following denitration and corrosion reduction methods for waste incineration equipment are provided. This method includes a primary combustion zone for performing primary combustion, and a combustion chamber having a secondary combustion zone for performing secondary combustion in which primary combustion gas containing unburned gas generated in primary combustion is burned, A waste incineration facility including a boiler having a heat transfer tube for recovering heat generated in a combustion chamber and a dust collector for purifying exhaust gas generated in the combustion chamber. The denitration and corrosion reduction method for this waste incineration facility includes a chemical supply step, a detection step, a correction step, and a supply step. In the chemical supply step, a chemical for reducing at least hydrogen chloride concentration is supplied to a downstream side of the boiler in the exhaust gas flow direction and an upstream side of the dust collector in the exhaust gas flow direction. In the detection step, how large is the detected value of the concentration of hydrogen chloride contained in the exhaust gas that has been discharged from the combustion chamber and passed through the heat transfer tube, the chemical supply location, and the dust collector as compared to a steady value A change tendency, which is a value indicating that, is detected. In the correction step, the correction amount of ammonium sulfate supplied for denitration and corrosion reduction of the heat transfer tube is calculated based on the change tendency of the hydrogen chloride concentration detected in the detection step and the supply amount of the chemical . In the supply step, a fixed supply amount of ammonium sulfate obtained by correcting the basic supply amount of ammonium sulfate by the correction amount is supplied to the secondary combustion zone.

  As a result, ammonium sulfate is thermally decomposed in the secondary combustion zone to generate ammonia, and the ammonia can reduce nitrogen oxides. Further, since sulfur oxides are generated from ammonium sulfate, the proportion of sulfur oxide salts in the corrosive substance, which is a mixture of various kinds of salts in which metal and acid groups are bonded, increases in the vicinity of the heat transfer tube of the boiler. (On the contrary, the proportion of chlorine salts is reduced). As a result, since the melting point of the corrosive substance increases, the corrosive substance is less likely to exist as a molten salt, so that the progress of corrosion of the heat transfer tube of the boiler can be reduced. In particular, by correcting the supply amount of ammonium sulfate based on the hydrogen chloride concentration, it is possible to supply an appropriate amount of ammonium sulfate in consideration of the amount of salts containing chlorine (that is, the amount necessary for reducing corrosion). Further, since the concentration of hydrogen chloride in the exhaust gas that has passed through the dust collector is measured, the detection device is unlikely to be contaminated, so that the concentration of hydrogen chloride can be detected stably over a long period of time.

  According to the present invention, a waste incinerator equipped with a waste incinerator and a boiler can be stably used for a long period of time while reducing the emission of nitrogen oxides (while causing a denitration reaction), and Corrosion that occurs in the heat transfer tube can be reduced.

The schematic block diagram of the waste incineration equipment containing the incinerator of the object which performs the method of this invention. Functional block diagram of waste incineration facility. The flowchart which shows the process which determines the supply amount of ammonium sulfate. The schematic block diagram of the waste incineration equipment which concerns on another embodiment. The flowchart which shows the process which determines the supply amount of ammonium sulfate, the presence or absence of supply of sulfuric acid / ammonia, and the supply amount.

  <Overall Configuration of Waste Incineration Facility> First, the waste incineration facility 100 including the incinerator 1 of the present embodiment will be described with reference to FIG. 1. FIG. 1 is a schematic configuration diagram of a waste incineration facility 100 including an incinerator 1 according to an embodiment of the present invention. In the following description, the terms “upstream” and “downstream” mean upstream and downstream in the direction in which waste, combustion gas, combustion gas, exhaust gas, etc. flow.

  As shown in FIG. 1, the waste incineration facility 100 includes an incinerator (waste incinerator) 1, a boiler 30, and a steam turbine power generation facility 35. The incinerator 1 incinerates the supplied waste. The detailed configuration of the incinerator 1 will be described later.

  The boiler 30 uses the heat generated by the combustion of the waste to generate steam. In the boiler 30, a large number of heat transfer tubes 31 (specifically, water tubes 31a and superheater tubes 31b) provided on the flow path wall are used to perform heat exchange between high-temperature combustion gas generated in the furnace and water. Generates steam (superheated steam). The steam generated in the water pipe 31 a and the superheater pipe 31 b is supplied to the steam turbine power generation facility 35.

  The steam turbine power generation facility 35 is configured to include a turbine and a power generator which are not shown. The turbine is rotationally driven by the steam supplied from the water pipe 31a and the superheater pipe 31b. The power generator generates electric power by using the rotational driving force of the turbine.

  <Structure of incinerator> The incinerator 1 includes a dust supply device 40 for supplying wastes into the furnace. The dust feeding device 40 includes a waste input hopper 41 and a dust feeding device main body 42. The waste input hopper 41 is a part into which waste is input from outside the furnace. The dust feeder main body 42 is located at the bottom portion of the waste input hopper 41, and is configured to be movable in the horizontal direction. The dust supply device main body 42 supplies the waste put in the waste input hopper 41 to the downstream side. The movement speed, the number of movements per unit time, the movement amount (stroke), and the stroke end position (movement range) of the dust supply device body 42 are controlled by the control device 90 shown in FIG. The dust supply device may be of a type that moves at a slight angle with respect to the horizontal direction.

  The waste supplied into the furnace by the dust supply device 40 is supplied to the combustion chamber 2. The combustion chamber 2 includes a primary combustion zone 10 and a secondary combustion zone 14. The primary combustion zone 10 is a space for primary combustion. The primary combustion is to react the input waste with a gas for primary combustion to burn it. The primary combustion gas is a gas containing oxygen supplied for primary combustion. The primary combustion gas includes primary air, circulating exhaust gas, and a mixed gas thereof. The primary air is air taken in from the outside and is not used for combustion or the like (that is, except for circulating exhaust gas). Therefore, the primary air also includes a gas obtained by heating the air taken in from the outside. Further, the primary combustion generates a primary combustion gas (flue gas after primary combustion) including unburned gas such as CO.

  The primary combustion zone 10 is composed of a drying section 11, a combustion section 12, and a post-combustion section 13. The waste is sequentially supplied to the drying unit 11, the combustion unit 12, and the post-combustion unit 13 by the transport unit 20. The transport unit 20 includes a dry grate 21 provided in the drying unit 11, a combustion grate 22 provided in the combustion unit 12, and a post-combustion grate 23 provided in the post-combustion unit 13. There is. Therefore, the transport unit 20 is composed of a plurality of stages of grate. Each grate is provided on the bottom of each part, and waste is placed on it. The grate is composed of a movable grate and a fixed grate which are arranged side by side in the waste transport direction, and the movable grate intermittently advances and reverses to transport the waste to the downstream side. At the same time, the waste can be stirred. The operation of the grate is controlled by the control device 90. In addition, a gap having a size that allows gas to pass through is formed in the grate.

  The drying unit 11 is a unit that dries the waste supplied to the incinerator 1. The waste in the drying unit 11 is dried by the primary air supplied from below the drying grate 21 and the radiant heat of combustion in the adjacent combustion unit 12. At that time, thermal decomposition gas is generated from the waste in the drying unit 11 due to thermal decomposition. Further, the waste of the drying section 11 is conveyed toward the combustion section 12 by the dry grate 21.

  The combustion unit 12 is a unit that mainly burns the waste material dried by the drying unit 11. In the combustion section 12, the waste mainly causes flame combustion and flame is generated. The waste in the combustor 12, the ash generated by the combustion, and the unburned unburned matter are conveyed toward the post-combustion section 13 by the combustion grate 22. The primary combustion gas and flame generated in the combustion section 12 pass through the throttle section 17 and flow toward the post-combustion section 13. Although the combustion grate 22 is provided at the same height as the dry grate 21, it may be provided at a position lower than the dry grate 21.

  The post-combustion section 13 is a section for burning waste (unburned matter) that has not been completely burned in the combustion section 12. In the post-combustion section 13, the radiant heat of the primary combustion gas and the primary air promote the combustion of unburned substances that could not be completely burned in the combustion section 12. As a result, most of the unburned materials become ash, and the unburned materials decrease. The ash generated in the post-combustion section 13 is conveyed toward the chute 24 by the post-combustion grate 23 provided on the bottom surface of the post-combustion section 13. The ash conveyed to the chute 24 is discharged to the outside of the waste incineration facility 100. Although the post-combustion grate 23 of the present embodiment is provided at a position lower than the combustion grate 22, it may be provided at the same height as the combustion grate 22.

  As described above, since the reactions that occur in the drying unit 11, the combustion unit 12, and the post-combustion unit 13 are different, the respective wall surfaces and the like are configured according to the reactions that occur. For example, since flame combustion occurs in the combustion section 12, a structure having a higher fire resistance level than the drying section 11 is adopted.

  As described above, in the primary combustion zone 10 of the incinerator 1 of the present embodiment, the input waste is dried, burned, and post-burned. In the incinerator 1 of the present embodiment, since the respective constituent stages are clearly separated, the above three treatments are performed in stages. The present invention can be applied to incinerators having various configurations. For example, the present invention is also applicable to incinerators where each stage is not clearly separated. The present invention is also applicable to an incinerator in which at least one of the drying stage and the post combustion stage does not exist. The present invention is also applicable to an incinerator having no grate, for example, a fluidized bed type incinerator or a fixed bed type incinerator.

  The secondary combustion zone 14 is a space for secondary combustion. The secondary combustion is to cause unburned gas contained in the primary combustion gas to react with the secondary combustion gas and burn. The secondary combustion gas is a gas containing oxygen supplied for secondary combustion. The secondary combustion gas includes secondary air, circulating exhaust gas, and mixed gas thereof. Secondary air is air taken in from the outside and is a gas that is not used for combustion or the like (that is, excluding circulating exhaust gas). Combustion completion can be promoted by performing secondary combustion. The secondary combustion zone 14 extends upward from the drying section 11, the combustion section 12, and the post-combustion section 13, and secondary air is supplied in the middle thereof. As a result, the primary combustion gas is mixed and agitated with the secondary air, and the unburned gas contained in the primary combustion gas is burned in the secondary combustion zone 14.

  Ammonium sulfate is supplied to the secondary combustion zone 14 by the ammonium sulfate supply device 57. The ammonium sulfate supply device 57 includes a storage section that stores ammonium sulfate, and a supply path that supplies ammonium sulfate toward the secondary combustion zone 14. Ammonium sulfate has a function of reducing the emission amount of nitrogen oxides (denitration) and a function of reducing corrosion of the heat transfer tube 31 of the boiler 30. The details will be described below.

  First, the reduction of nitrogen oxide emissions will be described. Ammonium sulfate is thermally decomposed by being supplied to the secondary combustion zone 14 having a high temperature, and ammonia, sulfur oxides (for example, sulfur dioxide), nitrogen, water and the like are generated. Since this ammonia acts as a reducing agent, the nitrogen oxide can be reduced to nitrogen. Since this method performs denitration without using a denitration catalyst, it is called non-catalytic denitration.

  Next, reduction of corrosion of the heat transfer tube 31 of the boiler 30 will be described. Corrosion of the heat transfer tube 31 is caused by the combustion gas generated in the incinerator 1. Specifically, since the waste contains various metals, chlorine compounds, sulfur compounds and the like, these react with each other to generate various kinds of salts. This mixture of various types of salts corrodes the heat transfer tube 31 and is henceforth referred to as a corrosive substance. The corrosive substance is in a molten state because it exceeds the melting point in the secondary combustion zone 14 having a high temperature, and flows downstream together with the combustion gas generated by the combustion in the incinerator 1. After that, as the combustion gas is cooled by heat exchange with the heat transfer tube 31, the corrosive substance below the freezing point solidifies. In addition, since the corrosive substance adheres to the heat transfer tube 31 in a molten state, the corrosion of the heat transfer tube 31 easily progresses. As described above, by supplying ammonium sulfate to the secondary combustion zone 14, sulfur oxides are generated. As a result, the proportion of sulfur oxides contained in the combustion gas is high, so the proportion of sulfur oxide salts in the corrosive substance is high, and as a result, the proportion of chlorine salts in the corrosive substance is low. .. Since the salts of sulfur oxides are higher than the melting points of the salts of chlorine, corrosive substances having a low proportion of chlorine salts have a high melting point when viewed as a mixture as a whole. Therefore, a corrosive substance having a low proportion of chlorine salts is unlikely to be in a molten state even under the same temperature condition. Therefore, the corrosive substance that adheres to the heat transfer tube 31 in the molten state can be reduced, so that the corrosion of the heat transfer tube 31 can be reduced.

  In the incinerator 1 of the present embodiment, the downstream end of the secondary combustion zone 14 and the upstream end of the area where the heat transfer tube 31 is arranged are connected. Therefore, in order to increase the salts of sulfur oxides before the corrosive substances reach the heat transfer tube 31, the ammonium sulfate is added comparatively upstream of the secondary combustion zone 14 (for example, more than the center in the flow direction of the combustion gas). It is preferable to supply the flame generated in the upstream combustion zone or the primary combustion zone 10 to the secondary combustion zone 14).

  Further, ammonium sulfate may be supplied in any form of powder, granules and aqueous solution. Which form is supplied is determined in consideration of reaction rate, handleability, amount of money, weight and the like. For example, regarding the reaction rate, an aqueous solution, a powder, and a granule are listed in ascending order. Since the aqueous solution is ionized, the reaction occurs in a short time. On the other hand, since the surface area of the granules is relatively smaller than that of the powder particles, it takes a long time for the reaction to occur.

  As described above, by supplying ammonium sulfate to the secondary combustion zone 14, it is possible to reduce the emission amount of nitrogen oxides and reduce the corrosion of the heat transfer tube 31 of the boiler 30. The process of determining the supply amount of ammonium sulfate will be described later.

  The high temperature secondary combustion gas discharged by the secondary combustion passes through the boiler 30 as described above, and is then discharged as an exhaust gas. The exhaust gas discharged from the incinerator 1 is purified by the filter-type dust collector 6 arranged on the downstream side. In addition, a chemical for reducing the concentration of harmful substances (hydrogen chloride, sulfur oxides, dioxins, etc.) in the gas contained in the exhaust gas is provided in the path (flue) through which the exhaust gas reaches the dust collector 6. Is thrown in.

  In addition, the waste incineration facility 100 includes a chemical tank 7 and a valve 8 as a configuration for charging the chemical. The drug tank 7 stores various drugs for reducing these harmful substances. The valve 8 has a mechanism for adjusting the amount of the medicine supplied to the flue. The control device 90 determines the type and supply amount of the medicine to be used based on the detection result of the property of the exhaust gas, the target value, and the like, and controls the opening of the valve 8 accordingly.

  <Supply of Primary Combustion Gas and Secondary Combustion Gas> The gas supply device 50 is a device that supplies gas (primary combustion gas, secondary combustion gas) into the combustion chamber 2. The gas supply device 50 of the present embodiment includes a primary air supply unit 51, a secondary air supply unit 52, and an exhaust gas supply unit 53. Each supply part is constituted by a blower for attracting or discharging gas.

  The primary air supply unit 51 supplies primary air to the combustion chamber 2 via the primary supply path 71. The primary supply path 71 is provided below the dry grate 21 provided below the dry grate 21, the combustion grate box 26 provided below the combustion grate 22, and the post combustion grate 23. It is a path for supplying primary air to each of the post-combustion blast boxes 27. In the primary supply path 71, a first damper 81 that adjusts the supply amount of primary air that is supplied to the drying air stage 25 and a second damper 82 that adjusts the supply amount of primary air that is supplied to the combustion air stage 26. , A third damper 83 for adjusting the supply amount of the primary air supplied to the post-combustion blast box 27, respectively. As shown in FIG. 2, the first damper 81, the second damper 82, and the third damper 83 are controlled by the control device 90.

  A heater may be provided in the primary supply path 71 so that the temperature of the primary air supplied to the combustion chamber 2 can be adjusted. Further, as described above, the primary combustion gas also includes the circulating exhaust gas and the mixed gas, so that they may be supplied to the combustion chamber 2. Further, in the present embodiment, the primary combustion gas is supplied to the primary combustion zone 10 from below, but may be supplied from the side of the primary combustion zone 10 or the like. The primary combustion gas may be supplied upstream of the primary combustion zone 10 as long as it is used for primary combustion.

  The secondary air supply unit 52 supplies secondary air to the combustion chamber 2 via the secondary supply path 72. Specifically, the secondary air supply unit 52 supplies secondary air to the air gas holding space 16 of the incinerator 1 from its upper portion (ceiling part), and the combustion gas changes its direction by the throttle unit 17. The secondary air is supplied to the secondary combustion zone 14 by supplying the secondary air (in the vicinity of the throttle portion 17). The secondary supply path 72 is provided with a fifth damper 85 for adjusting the supply amount of the secondary air supplied near the air gas holding space 16 and the throttle portion 17. As shown in FIG. 2, the fifth damper 85 is controlled by the control device 90.

  The exhaust gas supply unit 53 supplies (recirculates) the exhaust gas discharged from the waste incineration facility 100 into the furnace via the circulation exhaust gas supply path 73. A part of the exhaust gas discharged from the waste incinerator 100 and purified by the dust collector 6 is supplied to the incinerator 1 from both side surfaces (front side and rear side of the paper surface) of the combustion portion 12 by the exhaust gas supply portion 53. To be done. The position where the exhaust gas is supplied is not particularly limited. For example, the exhaust gas may be supplied from above (the ceiling) of the incinerator 1 or may be supplied from only one side surface. By supplying the exhaust gas to the incinerator 1, the oxygen concentration in the incinerator 1 is reduced, and a local excessive rise in the combustion temperature can be suppressed. As a result, generation of nitrogen oxides can be suppressed. Further, the circulating exhaust gas supply path 73 is provided with a fourth damper 84 for adjusting the supply amount of the circulating exhaust gas. As shown in FIG. 2, the fourth damper 84 is controlled by the control device 90.

  <Various Sensors and Control Device> The incinerator 1 is provided with a plurality of sensors for grasping the combustion state and the like as shown in FIGS. 1 and 2. Specifically, in the incinerator 1, an incinerator gas temperature sensor 91, an incinerator outlet gas temperature sensor 92, a CO concentration sensor 93, a nitrogen oxide concentration sensor 94, a hydrogen chloride concentration sensor 95, And a sulfur oxide concentration sensor 96.

  The in-incinerator gas temperature sensor 91 is arranged in the incinerator 1 (for example, downstream of the air gas holding space 16 and upstream of the post-combustion section 13), detects the incinerator gas temperature, and controls the controller 90. Output to. The incinerator outlet gas temperature sensor 92 is arranged in the vicinity of the incinerator 1 outlet (for example, downstream of the secondary combustion zone 14 and upstream of the boiler 30) and detects the incinerator outlet gas temperature to the control device 90. Output. The CO concentration sensor 93, the nitrogen oxide concentration sensor 94, the hydrogen chloride concentration sensor 95, and the sulfur oxide concentration sensor 96 are all arranged downstream of the dust collector 6, and the CO concentration, the nitrogen oxide concentration, and the nitrogen oxide concentration, respectively. The hydrogen chloride concentration and the sulfur oxide concentration are detected and output to the controller 90.

  Although it is not impossible to provide the CO concentration sensor 93 to the sulfur oxide concentration sensor 96 in the region where the heat transfer tube 31 is arranged, the combustion gas flowing in this region is not yet purified by the dust collector 6. Since each sensor is present and before harmful substances are removed by various chemicals, each sensor is easily contaminated. Therefore, when these sensors are provided in this area, it is difficult to detect data stably over a long period of time.

  The control device 90 includes a CPU, a RAM, a ROM, and the like, performs various calculations, and controls the entire incinerator 1. Specifically, the control device 90 controls the incinerator 1 based on the data acquired by the above-mentioned sensor, the specifications of the incinerator 1, target values of various data, other preset parameters, and the like. For example, the control device 90 controls the first damper 81 to the fifth damper 85 to adjust the supply amount of gas supplied to each part. Although not shown in FIG. 2, the control device 90 controls the dry grate 21, the combustion grate 22, and the post-combustion grate 23 to adjust the waste transport speed. Further, the control device 90 controls the valve 8 to adjust the type and supply amount of the drug that removes harmful substances. Further, the control device 90 controls the ammonium sulfate supply device 57 to adjust the supply amount of ammonium sulfate.

  Hereinafter, the process of adjusting the supply amount of ammonium sulfate will be described with reference to FIG. FIG. 3 is a flowchart showing a process for determining the supply amount of ammonium sulfate.

  First, the control device 90 detects the changing tendency of the nitrogen oxide concentration and the hydrogen chloride concentration, respectively, based on the detection results of the nitrogen oxide concentration sensor 94 and the hydrogen chloride concentration sensor 95 (S101). The change tendency is a value indicating how large the detected value is compared with the steady value.

  Next, the control device 90 calculates the correction amount of the supply of ammonium sulfate based on the changing tendency of the hydrogen chloride concentration (S102), and calculates the fixed supply amount by adding the correction amount to the basic supply amount of ammonium sulfate ( S103). As described above, ammonium sulfate has a function of reducing the emission amount of nitrogen oxides. Therefore, based on the amount of nitrogen oxides to be reduced (for example, the detection result of the nitrogen oxide concentration sensor 94 and the target value). Based on the difference between the above) and the basic supply amount, which is the amount of ammonium sulfate to be supplied. The basic supply amount may be determined according to the property of the waste to be put into the incinerator 1, in addition to the value detected by the nitrogen oxide concentration sensor 94. Alternatively, the basic supply amount may be set without considering the detection result of the nitrogen oxide concentration sensor 94. In this case, the basic supply amount may be a constant value.

  A value obtained by correcting the basic supply amount according to the correction amount is the fixed supply amount, and the fixed supply amount of ammonium sulfate is supplied to the secondary combustion zone 14. Further, in the present embodiment, the correction amount is calculated based on the changing tendency of the hydrogen chloride concentration. Here, the concentration of hydrogen chloride in the exhaust gas passing through the flue is affected by time delays, reduction by chemicals, etc., but hydrogen chloride in the combustion gas passing around the secondary combustion zone 14 and the heat transfer tubes 31 and the like. Correlates with concentration. When the concentration of hydrogen chloride in the combustion gas is high, the proportion of chlorine salts in the corrosive substance is high, so that the melting point of the corrosive substance is low and the corrosive substance in a molten state adheres to the heat transfer tube 31. It will be easier. Therefore, it is preferable to supply a larger amount of ammonium sulfate (sulfur oxide generated due to it) to the secondary combustion zone 14 as the hydrogen chloride concentration in the combustion gas is higher. Therefore, the correction amount calculated by the control device 90 increases as the hydrogen chloride concentration increases.

  Next, the control device 90 controls the ammonium sulfate supply device 57 to supply the fixed supply amount of ammonium sulfate calculated in step S103 to the secondary combustion zone 14 (S104). Further, since the processes of steps S101 to S104 are repeatedly performed at predetermined time intervals, the amount of ammonium sulfate corrected according to the magnitude of the hydrogen chloride concentration is supplied to the secondary combustion zone 14. Thereby, only by supplying ammonium sulfate, it is possible to reduce the discharge amount of nitrogen oxides and reduce the corrosion generated in the heat transfer tube 31 of the boiler 30. Further, when ammonium sulfate is excessively supplied, the generation amount of at least one of ammonia and sulfur oxide increases. However, by determining the fixed supply amount of ammonium sulfate in consideration of both the nitrogen oxide concentration and the hydrogen chloride concentration as in the present embodiment, while suppressing the generation amounts of ammonia and sulfur oxides, the above two effects Can be demonstrated.

  Further, in the present embodiment, the correction amount is calculated only based on the tendency of the change in the hydrogen chloride concentration, but in addition to this, the correction amount may be calculated further based on the supply amount of the drug for removing the harmful substance. .. This is because the hydrogen chloride concentration detected by the hydrogen chloride concentration sensor 95 decreases as the supply amount of this chemical increases. Further, in addition to or instead of the supply amount of the chemical, the correction amount may be calculated based on the change tendency of the sulfur oxide concentration detected by the sulfur oxide concentration sensor 96. This is because the proportion of sulfur oxide salts in the corrosive substance tends to increase as the concentration of sulfur oxides in the exhaust gas increases. Therefore, the correction amount calculated by the control device 90 becomes smaller as the sulfur oxide concentration in the exhaust gas becomes higher. Therefore, the correction amount is calculated based on the result of comparison between the tendency of changes in the hydrogen chloride concentration and the tendency of changes in the concentration of sulfur oxides.

  Next, another embodiment will be described with reference to FIGS. 4 and 5. FIG. 4 is a schematic configuration diagram of a waste incineration facility 100 according to another embodiment. FIG. 5 is a flowchart showing a process of determining the supply amount of ammonium sulfate, the presence / absence of supply of sulfuric acid / ammonia, and the supply amount.

  In the above embodiment, only ammonium sulfate is supplied in order to reduce the emission amount of nitrogen oxides and reduce the corrosion of the boiler 30. Instead of this, in the present embodiment, sulfuric acid (sulfuric acid aqueous solution) or ammonia water (ammonia aqueous solution) may be further supplied. Therefore, as shown in FIG. 4, the incinerator 1 of the present embodiment further includes a sulfuric acid supply device 58 and an ammonia water supply device 59. The sulfuric acid supply device 58 and the ammonia water supply device 59 are arranged in the vicinity of the ammonium sulfate supply device 57, and supply sulfuric acid and ammonia water to the secondary combustion zone 14, respectively. Further, the sulfuric acid supply device 58 includes a storage unit that stores the sulfuric acid and a supply path that supplies the sulfuric acid. The ammonia water supply device 59 includes a storage unit that stores the ammonia water, and a supply path that supplies the ammonia water.

  Here, ammonium sulfate has both functions of reducing the emission amount of nitrogen oxides and reducing the corrosion of the boiler 30, but for example, if the supply amount is increased to reduce the emission amount of nitrogen oxides, sulfur oxides become excessive. Will be supplied (the reverse pattern is also possible). In this embodiment, sulfuric acid and aqueous ammonia are supplied in consideration of them.

  Specifically, the control device 90 uses the nitrogen oxide concentration sensor 94, the hydrogen chloride concentration sensor 95, and the sulfur oxide concentration sensor 96 to detect the nitrogen oxide concentration, the hydrogen chloride concentration, and the sulfur, respectively. The change tendency of the oxide concentration is detected (S201). Next, the control device 90 calculates the correction amount and the fixed supply amount of ammonium sulfate based on the changing tendency of the hydrogen chloride concentration (or further using the changing tendency of the sulfur oxide concentration), as in the above embodiment ( S202, S203).

  Next, the control device 90 determines the presence / absence of supply of sulfuric acid and ammonia water and the supply amount based on the detection result in step S201 (S204). That is, the amount of ammonia to be supplied in order to reduce the emission amount of nitrogen oxide can be calculated from the changing tendency of the nitrogen oxide concentration and other data. Then, the amount of sulfur oxide to be supplied for reducing the corrosion of the boiler 30 can be calculated based on the changing tendency of the hydrogen chloride concentration (or further using the changing tendency of the sulfur oxide concentration). Then, when the amount of ammonia to be supplied and the amount of sulfur oxides are balanced, and when a large excess or deficiency does not occur by supplying only ammonium sulfate, only ammonium sulfate is supplied. On the other hand, when the amount of sulfur oxides to be supplied is relatively large compared to the amount of ammonia, sulfuric acid is supplied in addition to ammonium sulfate, and when the amount of ammonia to be supplied is relatively large compared to the amount of sulfur oxides, ammonium sulfate is supplied. In addition to this, ammonia water is supplied. The supply amount of sulfuric acid / ammonia water is a value obtained by subtracting the sulfur oxide amount / ammonia amount supplied by ammonium sulfate from the sulfur oxide amount / ammonia amount to be supplied.

  The supply amount of ammonia water is determined based on the changing tendency of the nitrogen oxide concentration and the supply amount of ammonium sulfate. Further, the supply amount of ammonium sulfate is determined based on the changing tendency of the hydrogen chloride concentration. Therefore, the supply amount of the ammonia water is determined based on the changing tendency of the hydrogen chloride concentration. It can also be understood that the supply amounts of sulfuric acid and ammonia water are determined based on the correction amount of ammonium sulfate.

  Next, the controller 90 supplies the fixed supply amount of ammonium sulfate calculated in step S203 to the secondary combustion zone 14 in the form of an aqueous solution, and supplies the supply amount of sulfuric acid or ammonia water determined in step S204 to the secondary combustion zone. 14 (S205).

  By performing the above-described processing, it is possible to simultaneously achieve the reduction of nitrogen oxide emissions, the reduction of boiler 30 corrosion, the reduction of ammonia emissions, and the reduction of sulfur oxide emissions.

  The waste incineration facility 100 of this embodiment includes both the sulfuric acid supply device 58 and the ammonia water supply device 59. Instead of this, the waste incineration facility 100 may be configured to include only one of the sulfuric acid supply device 58 and the ammonia water supply device 59.

  Further, in the waste incineration facility 100 of this embodiment, the ammonium sulfate supply device 57, the sulfuric acid supply device 58, and the ammonia water supply device 59 are arranged side by side, but each substance is supplied to the secondary combustion zone 14. For example, they may be arranged at distant positions.

  As described above, according to the aspect of the present invention, the following denitration and corrosion reduction methods for the waste incinerator 100 are provided. This method includes a combustion chamber 2 having a primary combustion zone 10 for performing primary combustion, and a secondary combustion zone 14 for performing secondary combustion in which primary combustion gas including unburned gas generated in primary combustion is burned. And a boiler 30 having a heat transfer tube 31 for recovering the heat generated in the combustion chamber 2 and a dust collector 6 for purifying the exhaust gas generated in the combustion chamber 2. .. The denitration and corrosion reduction method of the waste incineration facility 100 includes a detection process, a correction process, and a supply process. In the detection step, the changing tendency of the concentration of hydrogen chloride contained in the exhaust gas discharged from the combustion chamber 2 and passing through the heat transfer tube 31 and the dust collector 6 is detected. In the correction step, the correction amount of ammonium sulfate supplied for denitration and for reducing corrosion of the heat transfer tube is calculated based on the change tendency of the hydrogen chloride concentration detected in the detection step. In the supply step, a fixed supply amount of ammonium sulfate corrected by the correction amount of the basic supply amount of ammonium sulfate is supplied to the secondary combustion zone 14.

  As a result, ammonium sulfate is thermally decomposed in the secondary combustion zone 14 to generate ammonia, so that nitrogen oxide can be reduced by this ammonia. Further, since sulfur oxides are generated from ammonium sulfate, in the vicinity of the heat transfer pipe 31 of the boiler 30, the ratio of the salts of the sulfur oxides in the corrosive substance, which is a mixture of various kinds of salts in which the metal and the acid group are bonded, is increased. Higher (on the contrary, lower proportion of chlorine salts). As a result, since the melting point of the corrosive substance increases, the corrosive substance is less likely to exist as a molten salt, so that the progress of corrosion of the heat transfer tube 31 of the boiler 30 can be reduced. In particular, by correcting the supply amount of ammonium sulfate based on the hydrogen chloride concentration, it is possible to supply a proper amount of ammonium sulfate (that is, the amount necessary for reducing corrosion) in consideration of the generation amount of salts containing chlorine. Furthermore, since the hydrogen chloride concentration sensor 95, which is a detection device, is less likely to be contaminated because the hydrogen chloride concentration in the exhaust gas that has passed through the dust collector 6 is measured, the hydrogen chloride concentration can be detected stably over a long period of time. .

  Further, in the denitration and corrosion reduction method of the waste incineration facility 100 of the above embodiment, in the supply step, a fixed supply amount of ammonium sulfate is supplied to the secondary combustion zone 14 in the form of an aqueous solution, and the hydrogen chloride detected in the detection step. The supply amount of sulfuric acid determined based on the changing tendency of the concentration is supplied to the secondary combustion zone 14.

  Thus, by supplying sulfuric acid, the effect of reducing corrosion can be enhanced without increasing the amount of ammonia generated. Further, by supplying ammonium sulfate and sulfuric acid as an aqueous solution, it is possible to shorten the time required to contribute to denitration and reduction of corrosion.

  Further, in the denitration and corrosion reduction method of the waste incineration facility 100 of the above-described embodiment, in the supply step, the fixed supply amount of ammonium sulfate is supplied to the secondary combustion zone 14 in the form of an aqueous solution, and the hydrogen chloride detected in the detection step is supplied. The supply amount of ammonia water determined based on the tendency of change in concentration is supplied to the secondary combustion zone 14.

  Thus, by supplying the ammonia water, the denitration effect can be enhanced without increasing the amount of sulfur oxides generated. Further, by supplying ammonium sulfate and ammonia as an aqueous solution, it is possible to shorten the time required to contribute to denitration and corrosion reduction.

  Further, in the denitration and corrosion reduction method of the waste incineration facility 100 of the above-described embodiment, in the detection step, the change tendency of the sulfur oxide concentration contained in the exhaust gas passing through the dust collector 6 is further detected, and in the correction step. A correction amount is calculated based on the comparison result of the change tendency of the hydrogen chloride concentration and the change tendency of the sulfur oxide concentration.

  This makes it possible to supply a more appropriate amount of ammonium sulfate in consideration of not only the hydrogen chloride concentration but also the sulfur oxide concentration.

1 Incinerator 10 Primary Combustion Zone 14 Secondary Combustion Zone 30 Boiler 31 Heat Transfer Tube 57 Ammonium Sulfate Supply Device 94 Nitrogen Oxide Concentration Sensor 95 Hydrogen Chloride Concentration Sensor 96 Sulfur Oxide Concentration Sensor

Claims (4)

A combustion chamber having a primary combustion zone for performing primary combustion and a secondary combustion zone for performing secondary combustion in which primary combustion gas including unburned gas generated in the primary combustion is burnt, and the combustion chamber A waste incineration facility comprising a boiler having a heat transfer tube for recovering the heat, and a dust collector for purifying the exhaust gas generated in the combustion chamber,
On the downstream side of the exhaust gas flow direction from the boiler and on the upstream side of the exhaust gas flow direction from the dust collector, at least a chemical supply step of supplying a chemical for reducing the hydrogen chloride concentration,
A value indicating how large the detected value of the hydrogen chloride concentration contained in the exhaust gas that has been discharged from the combustion chamber and passed through the heat transfer tube, the chemical supply point, and the dust collector is compared with a steady value. A detection step of detecting a certain change tendency,
Based on the change tendency of the hydrogen chloride concentration detected in the detection step and the supply amount of the chemical, a correction step of calculating a correction amount of ammonium sulfate supplied for denitration and corrosion reduction of the heat transfer tube,
A supply step of supplying a fixed supply amount of ammonium sulfate corrected to the basic supply amount of ammonium sulfate to the secondary combustion zone.
A denitration and corrosion reduction method for a waste incineration facility, which comprises performing treatment including A denitration and corrosion reduction method for the waste incinerator according to claim 1,
In the supply step, the fixed supply amount of ammonium sulfate is supplied to the secondary combustion zone in the form of an aqueous solution, and the supply amount of sulfuric acid determined based on the change tendency of the hydrogen chloride concentration detected in the detection step is added. A denitration and corrosion reduction method for a waste incineration facility, which is characterized by supplying to a secondary combustion zone. A denitration and corrosion reduction method for the waste incineration facility according to claim 1 or 2,
In the supply step, while supplying the fixed supply amount of ammonium sulfate to the secondary combustion zone in the form of an aqueous solution, the supply amount of ammonia water determined based on the change tendency of the hydrogen chloride concentration detected in the detection step is supplied. A denitration and corrosion reduction method for a waste incineration facility, which comprises supplying the secondary combustion zone. A denitration and corrosion reduction method for the waste incineration facility according to claim 1,
The agent further reduces the concentration of sulfur oxides,
In the detection step, further, the change tendency of the concentration of sulfur oxides contained in the exhaust gas that has passed through the dust collector and the supply location of the chemical is detected,
In the correction step, based on the change tendency of the hydrogen chloride concentration, the change tendency of the sulfur oxide concentration , and the supply amount of the chemical, the correction amount such that the sulfur oxide concentration contained in the exhaust gas does not become too high. A denitration and corrosion reduction method for waste incineration facilities, which is characterized by calculation.

Images