JP2009240981A - Waste disposal system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the variation of a hydrogen chloride concentration in tail gas and to stabilize the hydrogen chloride concentration at a low level, in a waste disposal system for executing combustion treatment of combustion ash together with waste. <P>SOLUTION: The waste disposal system comprises: a combustion melting furnace 13 for melting incombustibles accompanying pyrolysis gas generated in a pyrolysis reactor 7; a second tail gas treatment means 31 arranged in the post stage of a first tail gas treatment means 29 for removing fly ash in the tail gas for executing desalination treatment of the tail gas; and an ash supply means 53 for segmenting the combustion ash from a hopper 51 storing the combustion ash and supplying it to the pyrolysis reactor or the combustion melting furnace. In this case, by controlling the segmentation amount of the combustion ash on the basis of the detected value of the hydrogen chloride concentration in the tail gas flowing between the first tail gas treatment means and the second tail gas treatment means, the variation of the hydrogen chloride concentration is suppressed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a waste treatment system that burns combustion ash generated in other incineration facilities together with waste such as garbage into a molten slag, and in particular controls the concentration of hydrogen chloride in exhaust gas within a predetermined range. Regarding technology.

  Conventionally, in a waste treatment system that treats general waste such as municipal waste and waste containing combustible waste such as waste plastic, for example, the waste is put into a pyrolysis reactor and pyrolyzed in a low oxygen atmosphere. As a result, a pyrolysis residue composed of pyrolysis gas and mainly non-volatile components is generated, and the combustible component separated from the pyrolysis residue and the previous pyrolysis gas are guided to the combustion melting furnace for combustion treatment. In addition, ash contained in pyrolysis gas or the like is melted to form molten slag, and the molten slag discharged from the combustion melting furnace is guided to a water tank and recovered as solid slag.

  Further, in such a waste treatment system, in order to remove acidic gas such as hydrogen chloride in exhaust gas discharged from the combustion melting furnace, a desalting agent is blown into the exhaust gas to filter the filter cloth of the desalting bag filter. A powder layer of a desalting agent is formed on the surface, and an acid gas is passed through the powder layer to neutralize and remove the acid gas.

  Here, slaked lime or baking soda is used as the desalting agent. For example, the concentration of hydrogen chloride in the exhaust gas flowing downstream of the desalting bag filter is detected, and the amount of sodium bicarbonate supplied based on this detected value. Has been disclosed (see Patent Document 1). In this way, the running cost can be reduced by controlling the supply amount of the desalting agent to optimize the supply amount.

JP 2002-113327 A

  By the way, in the waste processing system which makes ash into molten slag in the combustion processing as in Patent Document 1, the combustion discharged from other waste processing facilities (for example, including incineration equipment having no melting furnace) Combustion treatment of ash together with waste makes it possible to reduce the volume of combustion ash into molten slag.

  However, since such combustion ash contains a relatively large amount of chlorine, a large amount of hydrogen chloride gas is generated when the combustion ash is combusted. That is, the hydrogen chloride gas derived from the combustion ash is contained in the exhaust gas discharged from the combustion melting furnace, and accordingly, the hydrogen chloride concentration in the exhaust gas shows a high value. Furthermore, since the amount of chlorine contained in the combustion ash varies depending on the incineration facility, for example, if the combustion ash recovered from a plurality of incineration facilities is continuously charged and processed, the concentration of hydrogen chloride in the exhaust gas greatly fluctuates. Sometimes.

  Here, the supply amount of the combustion ash is set to an arbitrary amount so that the hydrogen chloride concentration in the exhaust gas falls within the allowable range. However, when the fluctuation range of the hydrogen chloride concentration increases, as in Patent Document 1, Controlling only the supply amount of the desalting agent cannot cope with the increase in the hydrogen chloride concentration, and the hydrogen chloride concentration may temporarily exceed the limit value. It is also conceivable to suppress the fluctuation of the hydrogen chloride concentration by making the supply amount of the desalting agent excessive. However, in such a case, an increase in running cost accompanying an increase in the supply amount of the desalting agent becomes a problem.

  An object of the present invention is to suppress fluctuations in the concentration of hydrogen chloride in exhaust gas and stabilize the hydrogen chloride concentration at a low level in a waste treatment system that burns combustion ash together with waste.

  In order to solve the above-mentioned problems, the present invention provides a pyrolysis reactor that pyrolyzes waste to generate pyrolysis gas and pyrolysis residue, and combusts the pyrolysis gas and noncombustible material accompanying the pyrolysis gas. A melting and melting furnace for discharging molten slag, a first exhaust gas processing means for removing fly ash in the exhaust gas discharged from the combustion melting furnace, and an exhaust gas discharged from the first exhaust gas processing means A second exhaust gas treatment means for performing a desalination treatment by adding a desalting agent therein, an ash supply means for cutting out the combustion ash from a hopper in which the combustion ash is stored and supplying it to the thermal decomposition reactor or the combustion melting furnace; A control means for controlling the amount of combustion ash cut out based on a detected value of the concentration of hydrogen chloride in the exhaust gas flowing between the first exhaust gas treatment means and the second exhaust gas treatment means. With features That.

  According to this, for example, when the chlorine content of the combustion ash increases and the hydrogen chloride concentration in the exhaust gas increases, the increase in the hydrogen chloride concentration can be suppressed by decreasing the supply amount of the combustion ash. In this way, by suppressing fluctuations in the hydrogen chloride concentration, for example, by supplying a predetermined amount of a desalting agent, the hydrogen chloride concentration can be maintained at a low level, which is accompanied by an excessive supply of the desalting agent. An increase in running cost can be suppressed. When the hydrogen chloride concentration decreases, the supply amount of the combustion ash can be increased as appropriate, so that a reduction in the processing capacity of the combustion ash can be suppressed.

  Specifically, the control unit decreases the cutout amount when the detected value exceeds the first specified value, and the cutout amount when the detected value falls below the second specified value that is lower than the first specified value. Control to increase. Thus, for example, by setting a predetermined control range of the hydrogen chloride concentration to a range lower than the limit value of the hydrogen chloride concentration, and controlling the supply amount of combustion ash based on these ranges, the hydrogen chloride concentration can be reduced. It can be stabilized at a low level easily.

  Furthermore, it is preferable that the second exhaust gas treatment means includes an addition amount control means for controlling the addition amount of the desalting agent based on the detected value. In other words, the hydrogen chloride concentration can be further stabilized at a low level by appropriately controlling the supply amount of the desalting agent while controlling the supply amount of the combustion ash and suppressing the fluctuation of the hydrogen chloride concentration. it can. Furthermore, since the supply amount of the desalting agent can be optimized, the running cost can be further reduced.

  ADVANTAGE OF THE INVENTION According to this invention, in the waste treatment system which burns combustion ash with a waste, the fluctuation | variation of the hydrogen chloride concentration in waste gas can be suppressed, and a hydrogen chloride concentration can be stabilized to a low level.

  Hereinafter, embodiments of a waste treatment system to which the present invention is applied will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of an embodiment in which the present invention is applied to a waste plant.

  Waste stored in a garbage pit (not shown) is conveyed by the conveyor 1 in a state of being crushed to a predetermined size (for example, 150 mm) by a garbage crusher, and is put into the hopper 3. The waste conveyed from the hopper 3 by the screw feeder 5 is put into a rotary drum type pyrolysis reactor 7. The waste is heated in a low-oxygen atmosphere (for example, 300 to 600 ° C.) and thermally decomposed in the thermal decomposition reactor 7, thereby generating a thermal decomposition residue composed of a pyrolysis gas and mainly nonvolatile components. The pyrolysis gas and the pyrolysis residue are led to the discharge device 9 and separated, and the pyrolysis gas is supplied to the combustion melting furnace 13 through the gas line 11, and the pyrolysis residue is supplied to a predetermined temperature (by a cooling device not shown). For example, after cooling to 80 ° C., it is separated into combustible components and non-combustible components. The combustible components including fine incombustible materials such as ash thus separated are finely pulverized to a predetermined size (for example, 1 mm) and then supplied to the combustion melting furnace 13.

  The combustion melting furnace 13 is provided with a burner at the top, and an air nozzle 15 is provided on the furnace wall below the burner. The pyrolysis gas and the combustible component are supplied into the furnace from the vicinity of the burner, and the air nozzle 15 is supplied with, for example, air pressure-fed through the air supply line from the garbage pit. A slag discharge port 17 for discharging molten slag is provided at the bottom of the combustion melting furnace 13, and a water tank 19 for storing cooling water is provided below the slag discharge port 17. The ash content heated and melted at a high temperature (for example, 1300 ° C.) in the combustion melting furnace 13 becomes molten slag, falls from the slag discharge port 17 into the water tank 19, and is cooled with water to become solid slag. The solid slag is carried out of the water tank 19 by a conveyor or the like and collected in the slag yard 21.

  The high-temperature exhaust gas discharged from the combustion melting furnace 13 is sequentially recovered by the high-temperature air heater 23 and the waste heat boiler 25, and then is guided to the temperature-decreasing tower 27 to be cooled. Then, dust removal and desalination treatment are performed through the desalting bag filter 31, and the dust is discharged from the chimney 35 to the atmosphere via the induction blower 33.

  A part of the high-temperature air recovered by the high-temperature air heater 23 and heated to a high temperature is returned to the pyrolysis reactor 7 via the air line 37 and used as heating air, and the remaining air is It is cooled by the heated air cooler 39 and returned to the high temperature air heater 23 via the heated air blower 41. The steam generated by the heat recovered by the waste heat boiler 25 is used for power generation by the steam turbine or the generator 43. The desalted residue recovered by the desalting bag filter 31 is recovered by the desalted residue recovering device 45 to remove heavy metals and the like, and then discharged out of the system and reused as appropriate.

  All of the waste treatment systems described above have a well-known configuration, but the waste treatment system of the present embodiment further includes an HCl analyzer 47, a control device 49, a hopper 51, and a screw feeder. 53 and the like.

  The HCl analyzer 47 samples and analyzes the hydrogen chloride (HCl) concentration in the exhaust gas flowing through the exhaust gas flow path connecting the dust removal bag filter 29 and the desalting bag filter 31. A result detected by the HCl analyzer 47 is input to the control device 49, and the cutting amount of the screw feeder 53 is controlled based on this input information. The combustion ash stored in the hopper 51 is supplied to one end side of the screw feeder 53, and the supplied combustion ash is transported to the other end side and then dropped onto the transporter 1.

  Combustion ash is combustion ash discharged from one or more other incineration facilities, and specifically includes, for example, boiler ash generated from a boiler, dust ash collected by removing exhaust gas, etc. . The waste treatment system of this embodiment is intended to burn combustion ash together with waste to form molten slag and to reduce the volume, and to control the supply amount of combustion ash under predetermined conditions It is characterized by doing. Note that the combustion ash can include the combustion ash generated in the waste treatment system of the present embodiment.

  Hereinafter, the operation of the waste treatment system of this embodiment will be described in detail.

  Combustion ash collected from each incineration facility is put into the hopper 51, dropped from the hopper 51 onto one end side of the screw feeder 53, and then transported, and then falls onto the lower transporter 1 from the other end side. The waste and combustion ash that have fallen from the conveyor 1 are supplied to the thermal decomposition reactor 7 via the hopper 3. Here, it is not necessary to forcibly mix the combustion ash and the waste, but they may be supplied to the pyrolysis reactor 7 after being mixed in advance by a mixing device or the like.

  When waste and combustion ash are supplied to the pyrolysis reactor 7, the waste is mainly pyrolyzed to produce pyrolysis gas and pyrolysis residue. The combustion ash discharged from the pyrolysis reactor 7, the combustible components in the pyrolysis residue, and the pyrolysis gas are all supplied to the combustion melting furnace 13 for combustion treatment. In the combustion melting furnace 13, the ash contained in the pyrolysis residue or pyrolysis gas and the combustion ash are melted to produce molten slag, and then the molten slag is cooled in the water tank 19 to form solid slag, which is a slag yard. Then, it is formed into a predetermined shape and reused for building materials or paving materials.

  On the other hand, the exhaust gas discharged from the combustion melting furnace 13 is heat-recovered by the high-temperature air heater 23 and the waste heat boiler 25, respectively, and further sent to the temperature-reducing tower 27 to be lowered in temperature. The exhaust gas whose temperature has been lowered by the temperature reducing tower 27 is sent to a dust removal bag filter 29 to filter fly ash. Here, the fly ash collected from the waste heat boiler 25, the temperature reducing tower 27, and the dust removal bag filter 29 can be treated as combustion ash as needed.

  The exhaust gas that has passed through the dust removal bag filter 29 is supplied with a desalting agent (hereinafter referred to as baking soda) from the desalting agent supply device 55 to form a powder layer of baking soda on the filter cloth surface of the desalting bag filter 31. Then, hydrogen chloride in the exhaust gas is removed by passing the exhaust gas through the powder layer. The desalting agent supply device 55 is based on, for example, the hydrogen chloride concentration detected by the HCl analyzer 47 or the hydrogen chloride concentration detected by sampling the exhaust gas after passing through the desalting bag filter 31 (not shown). The amount of baking soda is controlled.

  The HCl analyzer 47 detects the concentration of hydrogen chloride in the exhaust gas flowing downstream of the dust bag filter 29 and upstream of the desalting agent supply position, and converts the detection result into an electrical signal. Output to the control device 49. The control device 49 outputs the result of the arithmetic processing based on the input information to the drive motor of the screw feeder 53, thereby controlling the rotation speed of the motor to control the amount of combustion ash cut out.

  Fig. 3 shows the time change (line a) of the hydrogen chloride concentration in the exhaust gas when the combustion ash and waste are treated simultaneously with the amount of combustion ash cut out (line c) fixed, and only the waste is treated. The time change (line b) of the hydrogen chloride concentration in the exhaust gas is shown in comparison.

  From the figure, comparing the concentration of hydrogen chloride derived from waste with the time change of the concentration of hydrogen chloride when treating combustion ash and waste simultaneously, the concentration of hydrogen chloride derived from combustion ash is It can be seen that the fluctuation range is much larger than the hydrogen chloride concentration. For this reason, when treating the combustion ash with waste, if the hydrogen chloride concentration rapidly increases, for example, even if the amount of sodium bicarbonate supplied is increased based on the hydrogen chloride concentration, the removal rate depends on the supply capacity. There is a possibility that the treatment with the salt agent is not in time, and the hydrogen chloride concentration exceeds the limit value.

  In contrast, FIG. 2 shows an example of control over time of the hydrogen chloride concentration in the exhaust gas (d line) and the supply amount of combustion ash (e line) when the control of this embodiment is performed.

  In the present embodiment, when the amount of combustion ash cut out is controlled based on the detection value of the HCl analyzer 47 (hereinafter simply referred to as the detection value), an upper limit value and a lower limit value are provided as a management range of the hydrogen chloride concentration, When the detected value exceeds the upper limit value, the cutout amount of the screw feeder 53 is decreased, and when the detected value falls below the lower limit value, the cutout amount is increased. When the detected value is not less than the lower limit and not more than the upper limit, for example, the cutout amount is kept constant. Thus, by providing the management width and performing the dead zone control, it is possible to stabilize the fluctuation of the detection value. Here, the upper and lower limits of the management width and the set value of the management width can be determined as appropriate. In the present embodiment, control is performed by providing a dead zone. However, control may be performed using one specified value without providing a management width.

  FIG. 4 is a flowchart for explaining the control process for the amount of combustion ash cutout in FIG. 3.

  First, in step 1, the control device 49 determines whether or not the detected value exceeds the upper limit value. Here, if it is determined that the detected value exceeds the upper limit value, the process proceeds to step 2, and the rotational speed of the drive motor of the screw feeder 53 is controlled so as to reduce the cutout amount by ΔQ.

  On the other hand, if it is determined that the detected value does not exceed the upper limit value, the process proceeds to step 3, and the control device 49 determines whether or not the detected value is below the lower limit value. Here, if it is determined that the detected value is below the lower limit value, the process proceeds to step 4 and the rotational speed of the drive motor of the screw feeder 53 is controlled so as to increase the cutout amount by ΔQ. On the other hand, if it is determined in step 3 that the detected value is not below the lower limit value, the process proceeds to step 5 and the cutout amount at that time is held.

  Steps 1 to 5 are repeated according to the sampling period of the hydrogen chloride concentration. In the present embodiment, the increase / decrease control of the cutout amount is performed step by step in a preset ΔQ. However, the present invention is not limited to this example. For example, the upper limit value, the lower limit value, and the detection value Control may be performed so that ΔQ is determined according to the difference between the two.

  As described above, in the present embodiment, since the amount of combustion ash cut out is controlled based on the detected value of the hydrogen chloride concentration in the exhaust gas, the fluctuation of the hydrogen chloride concentration in the exhaust gas is suppressed, and the hydrogen chloride concentration Can be stabilized to a low level. In addition, according to the present embodiment, since fluctuations in the hydrogen chloride concentration in the exhaust gas can be suppressed, the supply amount control of the desalting agent based on the hydrogen chloride concentration or the supply of a constant amount of the desalting agent as in the past. Even with this method, the hydrogen chloride concentration can be maintained at a low level, thereby suppressing an increase in running cost associated with excessive supply of the desalting agent.

  Furthermore, in this embodiment, although the example which supplies combustion ash to the thermal decomposition reactor 7 with a waste was demonstrated, it is not restricted to this example, For example, combustion ash is thrown into the combustion melting furnace 13 directly, The input amount may be controlled.

1 is an overall configuration diagram of an embodiment in which the present invention is applied to a waste plant. It is a figure which shows an example of control of the time change of the hydrogen chloride density | concentration in waste gas when the control of this embodiment is performed, and the supply amount of combustion ash. Comparison of changes over time in the concentration of hydrogen chloride in exhaust gas when combustion ash and waste are treated simultaneously with a fixed amount of cut out combustion ash, and changes over time in the concentration of hydrogen chloride when only waste is treated FIG. It is a flowchart for demonstrating the control processing of the cut-out amount of the combustion ash of FIG.

Explanation of symbols

7 Pyrolysis reactor 13 Combustion melting furnace 29 Dust bag filter 31 Desalination bag filter 47 HCl analyzer 49 Controller 51 Hopper 53 Screw feeder

Claims (3)

A pyrolysis reactor that pyrolyzes waste to generate pyrolysis gas and pyrolysis residue, and combusts the pyrolysis gas, and melts incombustible substances accompanying the pyrolysis gas and discharges molten slag. A combustion melting furnace, a first exhaust gas treatment means for removing fly ash in the exhaust gas discharged from the combustion melting furnace, and a desalting agent added to the exhaust gas discharged from the first exhaust gas treatment means Waste treatment comprising: second exhaust gas treatment means for performing desalting treatment; and ash supply means for cutting out the combustion ash from a hopper in which combustion ash is stored and supplying the combustion ash to the thermal decomposition reactor or the combustion melting furnace In the system,
It comprises control means for controlling the cut-out amount of the combustion ash based on the detected value of the hydrogen chloride concentration in the exhaust gas flowing between the first exhaust gas treatment means and the second exhaust gas treatment means. Waste disposal system.   The control means decreases the cut-out amount when the detected value exceeds a first specified value, and when the detected value falls below a second specified value lower than the first specified value, The waste disposal system according to claim 1, wherein the amount of cutout is increased.   The waste treatment system according to claim 1 or 2, wherein the second exhaust gas treatment means includes an addition amount control means for controlling an addition amount of the desalting agent based on the detected value. .

Images