JP2007098187A - Waste treatment system and exhaust gas treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste treatment system which is capable of simply conducting the neutralization of an acid component in exhaust gas at a low cost, and to provide an exhaust gas treatment method. <P>SOLUTION: The waste treatment system 1 is provided with an incinerator 2 to incinerate waste, a dust collecting apparatus 4 to collect soot dust contained in the exhaust gas generated in the incinerator 2 and an exhaust gas passage 11 to send the exhaust gas from the incinerator 2 to the dust collecting apparatus 4. A neutralizing agent supply path 13 to supply the neutralizing agent for neutralizing the exhaust gas is connected with the exhaust gas passage 11 and further a steam supply path 26 to supply steam to the neutralizing agent is installed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a waste treatment system for neutralizing acidic components in exhaust gas discharged from an incinerator, and an exhaust gas treatment method.

A car shredder dust of an abandoned automobile generally called ASR (Automobile Shredder Residue) is disposed of through an incineration process such as combustion and melting. Such waste contains various components such as metal, urethane, plastic, etc., and exhaust gas generated by incineration treatment includes dust, hydrogen chloride (HCl), sulfur oxide (SO _x ), nitrogen oxidation. Various harmful substances such as substances (NO _x ) are included. Therefore, detoxification treatment is performed to remove harmful substances in the exhaust gas before releasing the exhaust gas into the atmosphere.

Among such detoxification treatments, a method for removing acidic components (hydrogen chloride, sulfur oxides) from exhaust gas includes alkaline neutralizers such as slaked lime (calcium hydroxide: Ca (OH) ₂ ) powder in the exhaust gas. A method is known in which an acidic component is neutralized by mixing, and the reaction products calcium chloride (CaCl ₂ ), calcium sulfite (CaSO ₃ ), and the like are removed from the exhaust gas by a dust collector. . Moreover, about this method, the method of increasing / decreasing the input amount and particle size of a neutralizing agent according to the density | concentration of the acidic component in waste gas is proposed (refer patent document 1). As a neutralizing agent, sodium hydrogen carbonate (sodium bicarbonate: NaHCO ₃ ) containing activated carbon has been proposed (see Patent Document 2).

JP 2002-113327 A JP 2004-141718 A

  However, in order to change the amount of the neutralizing agent input in accordance with the concentration of the acidic component in the exhaust gas, various control devices are required, leading to an increase in equipment costs and operating costs. Therefore, there has been a demand for a simple apparatus that can reliably neutralize exhaust gas without using a complicated control method. As for the neutralizing agent, in order to reduce the cost of the raw material, there has been a demand for a method capable of reliably neutralizing even a low-quality one.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a waste treatment system and an exhaust gas treatment method capable of simply and inexpensively neutralizing acidic components in exhaust gas. To do.

  In order to solve the above-mentioned problems, according to the present invention, there is provided a system for treating waste, an incinerator for incinerating waste, and a dust collecting unit for collecting soot dust contained in exhaust gas generated in the incinerator. And a neutralizing agent supply path for supplying a neutralizing agent for neutralizing the exhaust gas is connected to the exhaust gas channel. A waste treatment system is provided in which a water vapor supply path for supplying water vapor to the neutralizing agent is provided.

  The water vapor supply path may be connected in the middle of the neutralizer supply path in the vicinity of a junction where the neutralizer supply path merges with the exhaust gas flow path.

  The water vapor supply path may discharge the water vapor in a direction substantially perpendicular to the neutralizer supply path. The water vapor supply path may discharge the water vapor in a direction substantially parallel to the neutralizer supply path.

  Further, according to the present invention, there is provided a method for treating an exhaust gas generated by incineration of waste, wherein a neutralizing agent for neutralizing the exhaust gas and water vapor are mixed and supplied to the exhaust gas, There is provided an exhaust gas treatment method characterized in that a reaction product produced by a reaction between exhaust gas and a neutralizing agent is removed from the exhaust gas.

  In this method, the water vapor may be discharged in a direction substantially perpendicular to the flow of the neutralizing agent. The water vapor may be discharged in a direction substantially parallel to the flow of the neutralizing agent.

  That is, the present invention relates to a technology for neutralizing exhaust gas generated in incineration of waste, and is configured to spray water vapor on the neutralizing agent in order to increase the reactivity of the neutralizing agent. In order to improve the efficiency of the neutralization reaction with certainty, it was found that the influence of the quality of the neutralizing agent can be suppressed by using steam in order to improve the familiarity with the exhaust gas in advance in the supply of the neutralizing agent.

  According to the present invention, the reaction performance of the neutralizing agent can be enhanced by heating the neutralizing agent with water vapor. The neutralization reaction can be promoted with a simple structure, and the investment cost and operation cost required for the equipment of the waste treatment system can be greatly reduced. Even if a low-quality neutralizing agent is used, the neutralizing reaction can be sufficiently performed, and the cost required for the neutralizing agent can be reduced.

  Hereinafter, an example of a preferred embodiment of the present invention will be described. As shown in FIG. 1, a waste treatment system 1 according to the present invention includes an incinerator 2 that performs incineration of waste, a dust collector 4 that collects dust contained in exhaust gas after incineration, and a dust collection process. A chimney 5 for releasing the exhaust gas afterwards into the atmosphere is provided. Further, a first exhaust gas passage 11 for sending exhaust gas from the incinerator 2 to the dust collector 4 and a second exhaust gas passage 12 for sending exhaust gas from the dust collector 4 to the chimney 5 are provided. In the middle of the exhaust gas flow path 11, a neutralizing agent supply path 13 for supplying a processing fluid containing a neutralizing agent to the exhaust gas is connected. Although not shown, the exhaust gas passage 11 is also connected to an activated carbon supply passage for supplying activated carbon (C) for deodorizing exhaust gas and removing dioxins.

  The waste may be, for example, industrial waste such as ASR, or general waste such as household waste. In the case of ASR, various components such as metal, urethane, and plastic are included. The incinerator 2 is, for example, a fluidized bed furnace, and includes a boiler 2a that recovers thermal energy of exhaust gas after incineration. As the dust collector 4, for example, a bag filter incorporating a filter cloth (filter) is used.

At the upstream end of the neutralizer supply path 13, for example, a powder supply path 21 for supplying limestone powder mainly composed of calcium carbonate (CaCO ₃ ) as a neutralizer and a powdery neutralizer are conveyed. For this purpose, a gas supply path 22 for supplying a carrier gas such as air is connected. The gas supply path 22 and the neutralizing agent supply path 13 are connected to each other in a substantially straight tube shape, and the powder supply path 21 is connected between the gas supply path 22 and the neutralizing agent supply path 13. With this configuration, the processing fluid in which the neutralizing agent and the carrier gas are mixed is supplied to the neutralizing agent supply path 13. Further, in the vicinity of the joining portion 25 where the neutralizing agent supply passage 13 joins the exhaust gas passage 11, a steam supply passage 26 for supplying a heating gas containing water vapor (H ₂ O) is provided.

  As shown in FIG. 2, the neutralizing agent supply path 13 is connected in the middle of the straight exhaust gas flow path 11, and is 90% relative to the exhaust gas flow path 11 in a portion upstream of the merging portion 25. They are connected in an inclined state so as to form an angle θ of less than 0 °. A processing fluid is discharged from the neutralizing agent supply path 13 in a direction along the flow of the exhaust gas so as not to flow backward to the flow of the exhaust gas passing through the exhaust gas flow path 11.

  The water vapor supply path 26 is connected to the neutralizer supply path 13 in the vicinity of the junction 25. In the example shown in the figure, the supply port 26a, which is an end opening of the water vapor supply path 26, has a substantially straight tubular shape of the neutralizer supply path 13 on the side facing the exhaust gas flow path 11 across the neutralizer supply path 13. The heating gas (water vapor) is directed to be discharged in a direction substantially perpendicular to the neutralizing agent supply path 13. That is, the heated gas is discharged in a direction substantially perpendicular to the flow of the processing fluid. The heated gas supplied from the water vapor supply path 26 is discharged to the processing fluid immediately before flowing into the exhaust gas flow path 11 from the neutralizer supply path 13 and is swept away by the processing fluid while mixing with the processing fluid. It flows into the merging portion 25.

  By supplying the heating gas to the neutralizing agent in this way, the neutralizing agent is heated and water vapor is supplied to the neutralizing agent. Then, the neutralizing agent is activated, and when it comes into contact with the exhaust gas, the neutralization reaction is efficiently performed. The heated gas supplied from the water vapor supply path 26 may be a mixed gas of water vapor and a gas such as air for carrying the water vapor. The heating gas may contain, for example, about 1 to 10% of water by volume ratio. Further, about 1 to 20% of water may be supplied with respect to the volume flow rate of the processing fluid passing through the neutralizing agent supply path 13. If too much water is supplied from the water vapor supply passage 26, chlorine may be adsorbed to the water when the water is supplied to the exhaust gas, As a result, problems such as a possibility that the temperature of the exhaust gas rapidly drops and the reactivity may decrease may occur. Therefore, the flow rate of the heating gas supplied from the water vapor supply path 26 and the amount of moisture contained in the heating gas are adjusted to appropriate values according to the concentration of acidic components in the exhaust gas and the supply amount of the neutralizing agent. It is preferable to do.

  As shown in FIG. 1, the powder supply path 21 is connected to a neutralizing agent generating device 30 that generates neutralizer powder. The neutralizer generator 30 includes a raw material storage hopper 31 that stores limestone that is a raw material of the neutralizer, a dry pulverizer 32 that pulverizes the raw material, and a classifier 33 that classifies the neutralizer pulverized by the pulverizer 32. It has.

  The raw material is fed into the pulverizer 32 from the raw material storage hopper 31. The pulverizer 32 pulverizes the charged raw material into a powder having a particle diameter of about 1 to 100 μm by using, for example, a hammer mill or a vibration mill. The particle size distribution in the pulverized powder may be wide. For example, the particle size of about 50% of the mass may be about 50 μm or less.

  The classifier 33 classifies the powdery raw material supplied from the pulverizer 32 into fine particles and coarse particles according to the particle size, for example, by wind sorting. That is, an ascending airflow for classification is formed in the classifier 33, and fine particles out of the raw material powder are blown up by the airflow, and coarse particles having a predetermined particle diameter or more fall against the airflow due to gravity. It is the composition which does. The fine particles are supplied to the powder supply path 21 as a neutralizing agent. On the other hand, the coarse particles are returned to the pulverizer 32 and pulverized again by the pulverizer 32. In this way, particles having a predetermined particle size or less are supplied to the powder supply path 21 and supplied to the neutralizing agent supply path 13.

  As an air current for wind classification used in the classifier 33, for example, a part of exhaust gas derived from the dust collector 4 may be used. That is, a branch passage 12a branched from the exhaust gas passage 12 for sending the exhaust gas from the dust collecting device 4 to the chimney 5 is provided, and the branch passage 12a introduces the exhaust gas for wind classification to the classifier 33. Anyway. Since the oxygen concentration in the exhaust gas is low, when the exhaust gas is supplied into the classifier 33, the oxygen concentration in the classifier 33 is diluted, so that the raw material powder can be prevented from being oxidized. Therefore, the reactivity of the neutralizing agent can be prevented from decreasing.

  The finer the particle size of the neutralizing agent, the larger the specific surface area (total surface area of all particles contained in a unit mass of powder). The reactivity with increases. However, if the particle size is made too small, it becomes difficult to control the flow state, and there is a problem that it becomes difficult to carry with the carrier gas or difficult to diffuse in the exhaust gas passage 11. Accordingly, the particle size of the neutralizing agent and the supply amount to the powder supply passage 21 are specifications such as the concentration of acidic components in the exhaust gas passing through the exhaust gas passage 11 and the flow rate of the gas supplied from the gas supply passage 22. Therefore, it is preferable to adjust to an appropriate value.

  A blower (blower) 40 is connected to the gas supply path 22, and a carrier gas such as air is supplied to the neutralizing agent supply path 13 through the gas supply path 22 by the operation of the blower 40. At this time, the powdery neutralizer supplied from the powder supply path 21 to the neutralizer supply path 13 is blown by the carrier gas and introduced into the neutralizer supply path 13 together with the carrier gas. It has become.

  Next, a waste processing method using the waste processing system 1 configured as described above will be described. First, waste is incinerated in the incinerator 2, the exhaust gas is passed through the boiler 2 a of the incinerator 2, and is further led out from the incinerator 2 by the exhaust gas passage 11.

While the exhaust gas passes through the exhaust gas flow path 11, a processing fluid containing a neutralizing agent is supplied from the neutralizing agent supply path 13 and a heating gas containing water vapor is supplied from the water vapor supply path 26 at the junction 25. . From the water vapor supply path 26, the heated gas is discharged substantially perpendicular to the flow of the processing fluid. And it supplies to the exhaust gas flow path 11 in the state which the water vapor | steam in heating gas and the neutralizing agent in a processing fluid mixed. In this way, the heated neutralizing agent and moisture are supplied to the exhaust gas flowing through the exhaust gas passage 11. Then, hydrogen chloride (HCl) and sulfur oxide (SO _x ) contained in the exhaust gas and calcium carbonate (CaCO ₃ ) contained in the neutralizing agent undergo a neutralization reaction, and as a reaction product, calcium chloride (CaCl ₂ ), calcium sulfite (CaSO ₃ ) and the like are produced. By such chemical reaction, acidic components in the exhaust gas are decomposed, and the exhaust gas is neutralized so as to have a pH of about 6-8.

  Thus, the exhaust gas passes through the exhaust gas flow path 11 while being neutralized by the neutralizing agent, is introduced into the dust collector 4, is filtered by the filter cloth, and is cleaned. The reaction product generated in the exhaust gas passage 11 is collected together with the dust in the exhaust gas by a filter cloth or the like in the dust collector 4 and removed from the exhaust gas. Thereby, chlorine and sulfur contained in the exhaust gas immediately after being derived from the incinerator 2 are removed from the exhaust gas, and the exhaust gas is rendered harmless. The exhaust gas after being cleaned in the dust collector 4 is sent to the chimney 5 through the exhaust gas flow channel 12 and is safely discharged into the atmosphere by the chimney 5.

  According to the waste treatment system 1, the neutralization reaction between the neutralizing agent and the acidic component in the exhaust gas is promoted by supplying moisture to the neutralizing agent and heating the neutralizing agent with the heat of steam. Can do. The neutralization reaction can be promoted with a simple configuration without performing complicated control or adjusting the components of the neutralizing agent, and the investment cost and operating cost required for the equipment of the waste treatment system 1 can be reduced. It can be greatly reduced. As the neutralizing agent, naturally produced inexpensive limestone can be used, and it can be sufficiently used as a neutralizing agent simply by crushing limestone. Therefore, the cost required for the neutralizing agent can be reduced.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to such examples. It is obvious for those skilled in the art that various changes and modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

  In the above embodiment, the steam supply path 26 discharges the heating gas containing steam in a direction substantially perpendicular to the neutralizing agent supply path 13, but the supply direction of the heating gas is not limited thereto. . For example, as shown in FIG. 3, the heated gas may be discharged in a direction substantially parallel to the neutralizing agent supply path 13. In the illustrated example, the end 50 of the water vapor supply path 26 is provided inside the neutralizing agent supply path 13. The end portion 50 extends inside the neutralizing agent supply passage 13 toward the upstream side of the neutralizing agent supply passage 13 and extends toward the downstream side of the neutralizing agent supply passage 13. And has a substantially T-shape. A supply port 50c for discharging heated gas toward the upstream side of the neutralizing agent supply path 13 is opened at the end of the arm part 50a, and the neutralizing agent supply path 13 is formed at the end of the arm part 50b. A supply port 50d for discharging the heating gas toward the downstream side is opened. In such a configuration, with respect to the flow of the processing fluid passing through the neutralizing agent supply path 13, the heating gas is discharged from the supply port 50c substantially in parallel with the flow of the processing fluid, and the heating gas flows backward from the supply port 50d. To be discharged. Even in this case, water vapor in the heated gas can be suitably mixed with the neutralizing agent in the processing fluid, and the neutralization reaction between the acidic component in the exhaust gas and the neutralizing agent can be promoted.

  The supply of the heating gas from the water vapor supply path 26 may be performed continuously during the neutralization of the exhaust gas, but may be performed intermittently with a predetermined time interval, or the supply amount may be changed periodically. It may be changed randomly or randomly. In this way, if the heating gas is supplied intermittently or the supply amount of the heating gas is varied, the processing fluid and exhaust gas are stirred by the fluctuation of the heating gas flow, and the water vapor in the heating gas, The neutralizing agent and the acidic component in the exhaust gas can be easily mixed with each other, and the neutralization reaction can be further promoted.

In the above embodiment, the neutralizing agent is a limestone powder, but the neutralizing agent is not limited to this, and may be manufactured by chemical synthesis. The neutralizing agent is an alkaline one having water solubility, and may be any alkali metal salt or alkaline earth metal salt, such as caustic soda (sodium hydroxide: NaOH), sodium hydrogen carbonate (NaHCO ₃ ), percarbonate. sodium _{(Na 2 Co 3 · 3 /} 2H 2 O 2), quicklime (calcium oxide: CaO), slaked lime (calcium hydroxide: Ca _{(OH) 2),} or the like. In particular, in the present invention, since the efficiency of the neutralization reaction can be improved by supplying water vapor, the neutralization reaction is sufficiently performed even when a neutralizing agent having a low quality or a neutralizing agent that cannot obtain an excellent reaction efficiency as it is is used. Can be done. For example, a neutralizing agent mainly composed of sodium hydrogen carbonate can be used as a neutralizing agent even if the sodium hydrogen carbonate content is about 97% or less. Further, there is no need to add another substance such as activated carbon, and it can be used as a neutralizing agent as it is.

  As shown in FIG. 4, a control system that adjusts the supply amount of the neutralizing agent supplied from the powder supply path 21 may be configured. In the example shown in FIG. 4, an adjustment valve 60 for adjusting the supply amount of the neutralizing agent is interposed in the powder supply path 21. Further, an analyzer 61 for measuring the concentration of hydrogen chloride in the exhaust gas passing through the exhaust gas passage 12 is provided. Further, a control unit 62 is provided that adjusts the opening of the control valve 60 by PID adjustment based on the analysis value of the analyzer 61. During the neutralization reaction process of the exhaust gas, the control unit 62 monitors the analysis value of the analyzer 61 and adjusts the opening of the control valve 34 so that the analysis value becomes substantially zero. As a result, the amount of neutralizing agent supplied from the powder supply passage 21 to the neutralizing agent supply passage 13 is increased or decreased, and feedback control is performed so that the concentration of hydrogen chloride in the exhaust gas becomes substantially zero. In this way, hydrogen chloride in the exhaust gas can be reliably removed while minimizing the amount of neutralizer used, and the cost required for the neutralizer can be further reduced. Similarly, you may comprise the control system which controls the supply amount of a neutralizing agent so that the density | concentration of the sulfur oxide in the waste gas discharged | emitted from the dust collector 4 may become zero.

  Moreover, you may enable it to adjust the average particle diameter of a neutralizing agent according to the density | concentration etc. of the acidic component in waste gas. For example, when classifying using wind power in the classifier 33, the particle size serving as a reference for classification can be adjusted by adjusting the flow rate of the airflow used for classification. If the concentration of acidic components in the exhaust gas is high, reduce the air flow rate to reduce the average particle size of the neutralizer. If the concentration of acidic components in the exhaust gas is low, increase the air flow rate. Thus, the average particle size of the neutralizing agent may be increased.

  For example, as shown in FIG. 5, an analyzer 61 that measures the concentration of hydrogen chloride in the exhaust gas that passes through the exhaust gas flow path 12 by installing a flow rate control valve 70 in the branch path 12 a and the analysis of the analyzer 61. A control unit 62 that adjusts the opening degree of the flow control valve 70 based on the value by PID adjustment or the like may be provided. The controller 62 monitors the analysis value of the analyzer 61 during the exhaust gas neutralization reaction process, and adjusts the opening degree of the flow rate control valve 70 so that the analysis value becomes substantially zero. As a result, the flow rate of the air flow in the classifier 33 is increased, the average particle size of the neutralizing agent supplied from the powder supply path 21 to the neutralizing agent supply path 13 is adjusted, and the concentration of hydrogen chloride in the exhaust gas is reduced. Feedback control is performed so that it becomes almost zero. Even in this way, hydrogen chloride in the exhaust gas can be reliably removed. Similarly, you may comprise the control system which controls the average particle diameter of a neutralizing agent so that the density | concentration of the sulfur oxide in the waste gas discharged | emitted from the dust collector 4 may become zero.

  The present invention can be applied to a waste treatment system and an exhaust gas treatment method.

It is explanatory drawing of the waste disposal system concerning this Embodiment. It is explanatory drawing which showed the confluence | merging part of the exhaust gas flow path and the neutralizing agent supply path, and the water vapor supply path. It is explanatory drawing which showed the water vapor | steam supply path concerning another embodiment. It is explanatory drawing of the waste disposal system concerning another embodiment which enabled adjustment of the supply amount of the neutralizing agent. It is explanatory drawing of the waste-treatment system concerning another embodiment which enabled adjustment of the average particle diameter of a neutralizing agent.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Waste disposal system 2 Incinerator 4 Dust collector 11 Exhaust gas flow path 13 Neutralizing agent supply path 26 Water vapor supply path

Claims (7)

A system for treating waste,
An incinerator for incinerating waste, a dust collector for collecting dust contained in the exhaust gas generated in the incinerator, and an exhaust gas passage for sending the exhaust gas from the incinerator to the dust collector. Prepared,
A neutralizing agent supply path for supplying a neutralizing agent for neutralizing the exhaust gas is connected to the exhaust gas flow path,
A waste treatment system, characterized in that a water vapor supply passage for supplying water vapor to the neutralizing agent is provided. 2. The steam supply path according to claim 1, wherein the steam supply path is connected in the middle of the neutralizer supply path in the vicinity of a junction where the neutralizer supply path joins the exhaust gas flow path. Waste treatment system. The waste treatment system according to claim 1 or 2, wherein the water vapor supply path discharges the water vapor in a direction substantially perpendicular to the neutralizer supply path. The waste treatment system according to claim 1 or 2, wherein the water vapor supply path discharges the water vapor in a direction substantially parallel to the neutralizer supply path. A method for treating exhaust gas generated by incineration of waste,
Mix the neutralizing agent that neutralizes the exhaust gas and water vapor, and supply the exhaust gas,
An exhaust gas treatment method, wherein a reaction product generated by a reaction between the exhaust gas and a neutralizing agent is removed from the exhaust gas. The exhaust gas treatment method according to claim 6, wherein the water vapor is discharged in a direction substantially perpendicular to the flow of the neutralizing agent. The exhaust gas treatment method according to claim 5 or 6, wherein the water vapor is discharged in a direction substantially parallel to the flow of the neutralizing agent.

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