JP2005147532A - Waste treatment equipment - Google Patents

Abstract

【Task】
An object of the present invention is to provide a waste treatment apparatus that can reduce equipment costs by using equipment without downsizing and reducing the equipment size.
[Solution]
A dryer 3 for removing moisture contained in waste by heated air, a gasification furnace 100 for thermally decomposing dry waste dried by the dryer 3 into pyrolysis gas and char, and this pyrolysis A high-temperature combustion gas obtained by burning the gas is introduced into the gasification furnace and used as a heat source for thermal decomposition, and air is heated by the exhaust gas after heating the gasification furnace. It comprises an air heater 5 for obtaining this heated air. And the 1st recirculation waste gas path | route P1 for mixing a part of waste gas which passed the air heater 5 into the heating air before guide | inducing to the dryer 3 is provided.
[Selection] Figure 1

Description

  The present invention relates to a waste treatment apparatus.

  In recent years, a gasification and melting apparatus has attracted attention as a next-generation waste processing apparatus as one of the waste processing apparatuses. Gasification and melting equipment is used to dry and pyrolyze waste, such as municipal waste, industrial waste, and sludge, whose properties and amount of waste vary greatly, and is called flammable gas (hereinafter referred to as pyrolysis gas). Char is generated as a residue, and the heat obtained by burning the char is used for dry pyrolysis, melting slag of incombustibles in char, power generation, and the like. The main reasons for the attention of gasification and melting equipment are that it is possible to minimize the amount of final waste discharged and make it harmless, and extremely low harmful substances such as dioxins, nitrogen oxides, and carbon monoxide in combustion exhaust gas. It has many advantages for reducing the environmental burden associated with waste treatment, such as being able to control the level.

  However, when general wastes whose water content and flow rate fluctuate over time are to be treated, in order to fully draw out the advantages of this device, exhaust heat and exhaust gas to the atmosphere are improved by increasing the thermal efficiency of the entire device. It is important to control the amount and reduce the environmental burden. In view of economy, it is also desired to reduce the equipment cost by downsizing the apparatus. Furthermore, it is necessary to prevent waste ignition during dry pyrolysis, which leads to a reduction in the operating rate and safety of the apparatus.

  As a conventional waste treatment apparatus, for example, as disclosed in JP-A-9-329911, dry distillation gas discharged from a pyrolysis reactor is combusted, and the pyrolysis reaction vessel is heated by heat during combustion. It is known to generate heated air for the purpose. However, in the thing of Unexamined-Japanese-Patent No. 9-329311, the heat | fever which is insufficient in combustion of dry distillation gas is supplemented using the additional cooking apparatus, and it is necessary to use an external fuel as a heat source of the additional cooking apparatus. However, when external fuel is used, the amount of exhaust gas increases, which is counterproductive to reducing environmental impact. In addition, it is necessary to add a combustion facility and a safety device, and there is a disadvantage that the facility cost and the operation cost increase.

  On the other hand, as described in “Kitani, Mogi,“ Thermal decomposition gasification and melting system ”, Industrial machinery (May 1999), pp. 60-62”, the thermal decomposition reactor (external heat kiln) It has also been proposed that an external heat source is not used by using the pyrolysis gas combustion gas after heating as a heat source for the dryer.

Japanese Patent Laid-Open No. 9-329311

Kitani, Mogi, “Pyrolysis Gasification Melting System”, Industrial Machinery, May 1999, p. 60-62

  However, heating the pyrolysis reactor (external heat kiln) as described in “Kitani, Mogi,“ Pyrolysis Gasification Melting System ”, Industrial Machinery (May 1999), pp. 60-62”. In the case of using the combustion gas as a heat source for the dryer, there is the following problem: the temperature required for heating the pyrolysis reactor is about 700 degrees, whereas the dryer It is necessary to lower the temperature of the hot gas supplied to the exhaust gas, because if too much hot gas is supplied to the dryer, waste is ignited in the dryer. The gas after heating is mixed with external fresh air to lower the temperature.The combustion gas has a low oxygen concentration, so it is suitable as a gas used for drying with a dryer, but usually Mixed with fresh air of different oxygen concentration And the oxygen concentration is high, because the ignition point becomes high, the dryer is disadvantageously becomes large.

  An object of the present invention is to provide a waste treatment apparatus that can reduce equipment costs by reducing the size of equipment without using external fuel.

(1) In order to achieve the above object, the present invention provides a dryer for removing moisture contained in waste by heated air, and the dried waste dried by the dryer as pyrolysis gas and char. A gasification furnace for pyrolysis, a burner for introducing the high-temperature combustion gas obtained by burning the pyrolysis gas to the gasification furnace and using it as a heat source for pyrolysis, and the gasification furnace In the waste treatment apparatus comprising an air heater for heating the air with exhaust gas after heating the air to obtain the heated air, the air heater passed through the heated air before being led to the dryer A first recirculation exhaust gas path for mixing a part of the exhaust gas is provided.
With this configuration, the equipment cost can be reduced without using external fuel and by downsizing the equipment.

  (2) In the above (1), preferably, a combustion melting furnace for burning the char to melt incombustibles in the char and generating steam by using the retained heat of the exhaust gas of the combustion melting furnace An exhaust heat recovery boiler, and a steam superheater for superheating steam generated from the exhaust heat recovery boiler by exhaust gas that has passed through the air heater, wherein the first recirculation exhaust gas path includes the air heating A part of the exhaust gas that has passed through the steam superheater disposed at the rear stage of the heater is used as a path for mixing with the heated air.

  (3) In the above (1), preferably, a primary air supply path for supplying primary air for burning the pyrolysis gas in a reducing atmosphere to the burner, and the air heater at the exhaust gas outlet of the burner. A second recirculation exhaust gas path for mixing a part of the exhaust gas that has passed through, detecting the combustion state of the burner, and based on the detected state, the flow rate of the heated air and the first The recirculated exhaust gas flow rate, the primary air flow rate, and the control means for adjusting the second recirculated exhaust gas flow rate are provided.

  (4) In the above (3), preferably, the control means increases or decreases both the flow rate of the heated air and the flow rate of the primary air so that the combustion state of the burner becomes a predetermined state. Adjusted.

  (5) In the above (3), preferably, the control means sets the flow rate of the first recirculated exhaust gas and the flow rate of the second recirculated exhaust gas so that the combustion state of the burner becomes a predetermined state. When one is increased, the other is adjusted to decrease.

  (6) In the above (1), preferably, the combustion temperature of the burner is detected as the combustion state of the burner, and the control means detects the flow rate of the heated air so that the combustion temperature of the burner becomes a predetermined value. The flow rate of the first recirculated exhaust gas, the flow rate of the primary air, and the flow rate of the second recirculated exhaust gas are adjusted.

  (7) In the above (3), preferably, as the combustion state of the burner, the oxygen concentration of the combustion gas of the burner is detected, and the control means is configured so that the oxygen concentration of the combustion gas of the burner becomes a predetermined value. The flow rate of the heated air, the flow rate of the first recirculated exhaust gas, the flow rate of the primary air, and the flow rate of the second recirculated exhaust gas are adjusted.

  According to the present invention, equipment cost can be reduced without using external fuel and by downsizing the equipment.

Initially, the structure of the waste disposal apparatus by the 1st Embodiment of this invention is demonstrated using FIGS. 1-3. In the following embodiments, a waste gasification and melting apparatus will be described as an example of the waste treatment apparatus.
FIG. 1 is a system block diagram showing a configuration of a waste disposal apparatus according to a first embodiment of the present invention. FIG. 2 is an explanatory diagram of the effects and physical basis of the waste treatment apparatus according to the first embodiment of the present invention. FIG. 3 is a block diagram of the burner combustion temperature control means used in the waste disposal apparatus according to the first embodiment of the present invention.

  A normal waste treatment apparatus has various control means, but FIG. 1 shows a burner combustion temperature control means 400 that is mainly required in the description of the present embodiment. The input to the burner combustion temperature control means 400 is a detection signal, and the output is a target flow rate command for control. However, here, the control means is shown as a block for easy understanding of the control method, but in actuality, it is realized by a main computer installed in the control room or a controller arranged beside each device.

  First, the operation of each device of the gasification and melting apparatus of the present embodiment will be described with reference to FIG. The waste 2 accumulated in the waste pit 1 is first fed from one end of a rotary dryer 3 via a conveyor, a screw feeder or the like (not shown). The thrown-in waste 2 is dried by high-temperature drying air 4 in which the following three heating media are mixed while being transported through the dryer. First, the first heating medium is a medium supplied from the primary air supply path P2, and is a part of the air taken in from the waste pit 1 (sometimes referred to as fresh air in comparison with the exhaust gas). This is the first heated air 6 preheated by the air heater 5. The second heating medium is a medium supplied from the second recirculation exhaust gas path P <b> 3 and is the recirculation air 8 heated by the second air heater 7. The third heating medium is a medium supplied from the first recirculation exhaust gas path P1, and is the recirculation exhaust gas 11 that is a part of the steam superheater exhaust gas 10 that has passed through the steam superheater 9 described later. In this embodiment, the recirculated exhaust gas 11 is used as a part of the heated air, and a part of the exhaust gas that has passed through the steam superheater 9 disposed at the subsequent stage of the air heaters 5 and 7 is used. It is the 1st main point of a form. The reason for this will be described later.

  The waste 2 thrown into the dryer 3 receives heat energy from the drying air 4, is dried until the moisture in the waste reaches about 15%, and is discharged as a dry waste 12.

  Here, the effect of this embodiment and its physical basis will be described with reference to FIG. Fig.2 (a) has shown the ignition limit of the waste material 2 thrown into the dryer in the relationship between the temperature of the dryer inlet air 4, and humidity. As understood from this figure, in order to make the dryer 4 small, it is necessary to increase the air temperature. However, simply raising the temperature may cause ignition. In order to prevent ignition, it is necessary to increase the air flow rate by increasing the size of the first air heater 5 or the second air heater 7 without increasing the air temperature, which is a requirement for downsizing. Conflicts. In addition, air heating using an external fuel as in the prior art increases the operating cost.

  On the other hand, as can be understood from FIG. 2A, ignition can be prevented even if the dryer inlet air humidity is increased. As a method for increasing the humidity, as shown in FIG. 2 (b), there is a method of increasing the flow rate of the recirculated air 8 or introducing a spray into the dryer inlet air. However, the increase in the flow rate of the recirculation air 8 has a capacity limit of the recirculation air fan 40, and the size of the apparatus needs to be increased. In addition, since spraying causes a decrease in drying efficiency, it is against the requirement of improving thermal efficiency.

  As a method for preventing ignition other than the above-described method, in the present embodiment, as shown in FIG. 2C, a method of reducing the oxygen concentration of the dryer inlet air 4 is adopted. As shown in FIG. 2C, if the oxygen concentration can be lowered, ignition can be prevented even if the air temperature is raised. In order to realize this, in the present embodiment, as described above as the first essential point, a part of the steam superheater exhaust gas 10 is mixed into the drying air 4 as the recirculated exhaust gas 11. According to this method, no external fuel is used, the air heater is not enlarged, the recirculation air fan is not enlarged, the spray is not used, and the ignition limit is reached. This makes it possible to reduce the size of the dryer.

  The advantage of using the recirculated exhaust gas 11 which is the first main point of the present embodiment and using a part of the exhaust gas that has passed through the steam superheater 9 disposed in the subsequent stage of the air heaters 5 and 7 will be described. To do. As described above, since the drying air 4 in a low oxygen state is obtained by using the recirculated exhaust gas, the waste can be dried at a high temperature without igniting. That is, since the heat load of the dryer 3 can be increased, the dryer can be reduced in size, and the equipment cost can be reduced.

  Here, if the temperature of the drying air 4 supplied to the dryer 3 is T4, in this embodiment, it is 350 degreeC, for example. The temperature T11 of the recirculated exhaust gas 11 that has passed through the steam superheater 9 is, for example, 500 ° C. Further, the temperature T6 of the first heated air 6 heated by the air heater 5 is set to 250 ° C., for example. Here, in order to simplify the explanation, the recirculated exhaust gas 11 (temperature 500 ° C.) and the first heated air 6 (temperature 250 ° C.) are mixed without the recirculated air 8 being supplied, When the drying air 4 is obtained, the ratio (Q11: Q6) of the flow rate Q11 of the recirculated exhaust gas 11 and the flow rate Q6 of the first heated air 6 is 2: 3. Further, when mixed at this flow rate ratio, if the oxygen concentration of the recirculated exhaust gas 11 is 5% and the oxygen concentration of the first heated air 6 is 21%, the oxygen concentration of the drying air 4 is about 14%. . Due to such a low oxygen concentration, even if the temperature of the drying air 4 is set to 350 ° C., for example, the inside of the dryer 3 can be brought to a state below the ignition point.

  On the other hand, for example, the case where the gasifier exhaust gas 25 discharged from the gasifier 100 is used as the third heating medium will be considered. The temperature T25 of the gasifier exhaust gas 25 is, for example, 750 ° C. When mixing the gasifier exhaust gas 25 (temperature 750 ° C.) and the first heated air 6 (temperature 250 ° C.) to obtain the drying air 4 at 350 ° C., the flow rate Q25 of the gasifier exhaust gas 25 and the first heating The ratio (Q25: Q6) of the flow rate Q6 of the air 6 is 1: 4. Further, when mixed at this flow rate ratio, if the oxygen concentration of the gasifier exhaust gas 25 is 5% and the oxygen concentration of the first heated air 6 is 21%, the oxygen concentration of the drying air 4 is about 18%. Become. In this case, since the oxygen concentration is higher than in the above case, the ignition point is lowered, and the temperature of the drying air 4 may be ignited at 350 ° C., for example. Increasing the heated air 6 further decreases the oxygen concentration. Therefore, in this case, the dryer 3 is increased in size.

  As described above, the gasifier exhaust gas 25 discharged from the gasifier 100 is not directly used as part of the drying air, and the gasifier exhaust gas 25 is used as a heat source for the air heaters 5 and 7 and the steam superheater 9. As a part of the drying air, the heat load of the dryer 3 can be increased by using the exhaust gas whose temperature has been lowered by heat exchange of these devices, so that the dryer can be downsized and the equipment cost can be reduced. It becomes.

  Again, in FIG. 1, the dry waste 12 is further introduced from one end of the rotary gasifier 100 via a screw feeder, a pusher, etc. (not shown). The supplied dry waste 12 is heated from the high-temperature combustion gas 15 (jacket inflow gas as a thermal decomposition heating medium) that flows into the jacket 14 provided on the outer periphery of the drum 13 while being transported in the gasification furnace. Residual moisture is evaporated by receiving energy, and is separated into a char 17 which is a residue containing a combustible gas (pyrolysis gas) 16 and an incombustible material by thermal decomposition, and is discharged from the other end.

  The combustible gas 16 includes carbon monoxide, hydrogen, light gas, and heavy gas as the combustible gas, carbon dioxide as the incombustible gas, evaporated water, pyrolysis generated water, and the like. On the other hand, the char 17 is made of ash, debris, metal, or the like as an incombustible material in addition to carbon, hydrogen, or oxygen as a combustible material.

  The combustible gas 16 generated from the gasification furnace 100 is guided to the burner 18 and burned by two kinds of combustion air described below. The first combustion air is primary air 19 (a part of fresh air taken from the waste pit 1) for burning the combustible gas 16 in a reducing atmosphere. The second combustion air is secondary air 20 (subtracting the recirculation air 8 from the dryer outlet air 15) for further burning the gas burned in the reducing atmosphere in an oxidizing atmosphere. The secondary air 20 is sent to the burner 18 by a circulating air fan 40.

  The second essential point of the present embodiment is that the combustible gas 16 is stably burned in a reducing atmosphere using the primary air 19 having a high oxygen concentration, and the secondary air 20 containing a large amount of water evaporated from the waste is oxidized. This makes it possible to significantly reduce the generation of NOx that accompanies combustion.

  The gas combusted in the reducing atmosphere is mixed with the burner exhaust gas temperature recirculation exhaust gas 21 (a part of the steam superheater outlet exhaust gas 10), thereby being cooled to a predetermined temperature to become the burner exhaust gas 22.

  A part of the burner exhaust gas 22 becomes the jacket inflow gas 15 that is guided to the jacket 14 and contributes to actual thermal decomposition, and the rest becomes the jacket bypass gas 23 that bypasses the jacket. The jacket bypass gas 23 merges with the jacket outlet gas 24 to become a gasifier exhaust gas 25.

  A part of the gasifier exhaust gas 25 is used as the air heating gas 26 for heating the first heated air 6 in the first air heater 5 and the recirculated air 8 in the second air heater 7. Of the gasifier exhaust gas 25, the remaining air heater bypass gas 27, which is divided into the air heating gas 26, is the air-heated exhaust gas 28 that has been lowered in temperature by passing through the two air heaters 5, 7. Combined to become the exhaust gas 29 for the steam superheater.

  The temperature of the steam superheater exhaust gas 29 is lowered by passing through the steam superheater 9 that superheats the steam 37 generated from the exhaust heat recovery boiler 200 described later, and becomes the steam superheater exhaust gas 10. A part of the steam superheater exhaust gas 10 is used as the recirculated exhaust gas 11 for drying the waste and the recirculated exhaust gas 21 for controlling the burner exhaust gas temperature as described above. The remainder is introduced into the upper part of a combustion melting furnace 31 described later and used as a quench gas 32 for rapidly cooling the char combustion exhaust gas in the combustion melting furnace 31.

  In the char 17 discharged from the gasification furnace 100, the metal is removed by the char processing device 33 and pulverized to become a fine powder char 34, which is accumulated in the char hopper 35. The fine powder char accumulated in the char hopper 35 is blown into the furnace together with the carrier air as the combustion char 36 in the combustion melting furnace 31.

  The combustion char 36 blown into the combustion melting furnace 31 is combusted by the char combustion air 30. The char combustion air 30 is a part of the fan supply air 39 taken from the dry waste pit 1 by the pushing air fan 38, and the rest is the pyrolysis gas in the reducing atmosphere of the first heating air 6 and the burner 18 described above. It is the primary air 19 for burning.

  The quench gas 32 introduced into the combustion melting furnace 31 is for rapidly cooling the char combustion exhaust gas so that the slag in the exhaust gas does not adhere to and solidify (slagging) on the furnace wall and the heat transfer tube of the exhaust heat recovery boiler 200. .

  The exhaust heat recovery boiler 200 is for receiving the boiler feed water 41 and recovering heat generated in the combustion melting furnace 31 to generate steam. The steam 37 that has been steam-separated by the boiler drum 42 is guided to the steam superheater 9, becomes superheated steam 43, is introduced into the steam turbine 44 of the turbine power generator 300, and drives the generator 45 to obtain a power generation output.

  The exhaust gas 46 that has passed through the exhaust heat recovery boiler 200 is dedusted, desulfurized, and denitrated by an exhaust gas treatment device 47, rendered harmless, and discharged from the chimney 48 to the outside of the system.

  Exhaust steam from the steam turbine 44 is supplied to the boiler 200 by the boiler feed pump 50 through the condenser 49.

  Next, the control method of the gasification melting apparatus of this embodiment is demonstrated using FIG.1 and FIG.3.

  The burner combustion temperature control means 400 shown in FIG. 1 inputs a burner combustion temperature signal (TC) 52 detected by a thermometer 51 installed in the burner 18, and the next four target flow rates so that this becomes a predetermined value. Outputs a command.

  The first target flow rate command is a signal for adjusting the flow rate of the primary air 19 with respect to the burner 18, and the target flow rate command (for ensuring the required primary air flow rate for the primary air flow rate adjustment valve device 53 ( F1) 54 is output. The second target flow rate command is a signal for adjusting the flow rate of the first heated air 6, and the target flow rate command for securing the necessary first heated air flow rate for the first heated air fan device 55. (F2) 56 is output. The third target flow rate command is a signal for adjusting the flow rate of the recirculated exhaust gas 11, and the target flow rate command (F3) for ensuring the necessary recirculated exhaust gas flow rate for the recirculated exhaust gas fan device 57. 58 is output. The fourth target flow rate command is a signal for adjusting the flow rate of the recirculated exhaust gas 21 for controlling the burner exhaust gas temperature, and the recirculated exhaust gas required for the recirculated exhaust gas flow rate adjusting valve device 59 for controlling the burner exhaust gas temperature. A target flow rate command (F4) 60 for securing the flow rate is output.

  Next, the control method in the burner combustion temperature control means 400 will be described in more detail with reference to FIG. However, here, the control means is shown as a block for easy understanding of the control method, but in actuality, it is realized by a main computer installed in the control room or a controller arranged beside each device.

As shown in FIG. 3, the burner combustion temperature control means 400 is a deviation between the burner combustion temperature setting means 61 for setting the burner combustion temperature target value (T _CR ) and the burner combustion temperature signal (T _C ) 52. Subtraction means 62 for obtaining (E), proportional integration means 63 for proportionally integrating deviation (E) with respect to time, and a proportional constant for the basic flow rate command value (R _F ) obtained by proportional integration means 63. Multiplication means 64, 65, 66, and 67 for multiplying K1, K2, K3, and K4 to obtain the target flow rate commands (F1, F2, F3, and F4), respectively. The proportional integration means 63 multiplies the deviation (E) by proportional constants KP and KI to obtain R1 and R2, respectively, and further integrates R2 over time to obtain R3. Integrating means 63c and adding means 63d for adding R1 and R3 to obtain a basic flow rate command value (R _F ).

  The target flow rate command F4 is for canceling F3, and is calculated as K4 = −K3. That is, the flow rate equal to the recirculation exhaust gas flow rate (F3) is subtracted from the target flow rate command value from the recirculation exhaust gas flow rate control means (not shown) for burner exhaust gas temperature control, thereby circulating the relationship between the dryer 3 and the gasifier 100. This is to stabilize the flow rate of air and gas.

  For example, when the combustible gas 16 is fluctuating, in order to stabilize the temperature Tc of the burner 18, the primary air flow control valve device 53 and the first heated air fan device 55 are adjusted, and the primary air 19 and the secondary air are adjusted. The control means 400 outputs a target flow rate command (F1) and a target flow rate command (F2) so as to increase or decrease both the flow rates of the air 20. Further, with respect to the overall flow rate flowing through the burner 18, the recirculation exhaust gas fan device 57 is adjusted to control the flow rate of the recirculation gas 11. At this time, when increasing the recirculation gas 11, the control means 400 outputs the target flow rate command (F3) and the target flow rate command (F4) so as to decrease the recirculation exhaust gas 21 for burner exhaust gas temperature control.

The above is the control for setting the burner combustion temperature to the target value (T _CR ) by the burner combustion temperature control means 400, and other flow rate control will be briefly described. In order to make the flow rate of the dry air 4 flowing into the dryer 3 constant, the flow rate of the recirculation air 8 is adjusted by an adjustment valve. Moreover, in order to make the temperature of the dry air discharged | emitted from the dryer 3 constant, the flow volume of the air heater bypass gas 27 and the exhaust gas 28 after air heating is controlled. When the temperature of the dry air discharged from the dryer 3 is increased, the flow rate of the air heater bypass gas 27 is increased, and the flow rate of the exhaust gas 28 after the air heating is controlled to be decreased.

  As described above, according to the present embodiment, the recirculation exhaust gas 11 that has passed through the steam superheater 9 disposed in the subsequent stage of the air heaters 5 and 7 is used as a part of the heated air, so that the dryer 3 Therefore, the dryer can be downsized and the equipment cost can be reduced.

Next, the configuration of the waste disposal apparatus according to the second embodiment of the present invention will be described with reference to FIG.
FIG. 4 is a system block diagram showing the configuration of the waste disposal apparatus according to the second embodiment of the present invention. The same reference numerals as those in FIG. 1 indicate the same parts.

  In the embodiment shown in FIG. 1, the recirculation gas 11 is drawn from the outlet of the steam superheater 9. However, in this embodiment, the recirculation gas 11 is placed in front of the steam superheater 9 as indicated by a thick line in the figure. However, it is characterized in that it is drawn from the rear stage of the air heaters 5 and 7.

  Here, the temperature T11 of the recirculated exhaust gas 11 that has passed through the air heater 5 is 600 ° C., for example. Further, the temperature T6 of the first heated air 6 heated by the air heater 5 is set to 250 ° C., for example. Here, in order to simplify the explanation, the recirculated exhaust gas 11 (temperature 600 ° C.) and the first heated air 6 (temperature 250 ° C.) are mixed without being supplied with the recirculated air 8, When the drying air 4 is obtained, the ratio (Q11: Q6) of the flow rate Q11 of the recirculated exhaust gas 11 and the flow rate Q6 of the first heated air 6 is 2: 5. Further, when mixed at this flow rate ratio, if the oxygen concentration of the recirculated exhaust gas 11 is 5% and the oxygen concentration of the first heated air 6 is 21%, the oxygen concentration of the drying air 4 is about 16.5%. It becomes. In this case, since the oxygen concentration is higher than in the example of FIG. 1, the ignition point is lowered, and the temperature of the drying air 4 may be ignited at 350 ° C., for example. However, compared with the case where the gasifier exhaust gas 25 discharged from the gasifier 100 is used as it is as the third heating medium, the ignition point can be lowered and the dryer can be downsized.

  The apparatus in the frame shown by the alternate long and short dash line in the figure, such as the combustion melting furnace 31, the exhaust heat recovery boiler 200, the turbine generator 300, and the steam superheater 9, is a configuration necessary as a waste gasification melting apparatus. However, in the waste treatment apparatus that does not have the combustion melting furnace 31 and uses the char 17 generated in the gasification furnace 100 in another combustion apparatus, the turbine generator 300 is not provided. The steam superheater 9 for supplying the heating steam 43 to the turbine 44 is also unnecessary. In the disposal unit processing apparatus having such a configuration, the configuration of the embodiment shown in FIG. 1 cannot be adopted, and a part of the exhaust gas that has passed through the air heater 5 is dried air as in the present embodiment. By using as part of the dryer, the dryer can be downsized.

  As described above, according to the present embodiment, the recirculated exhaust gas 11 that has passed through the air heaters 5 and 7 is used as part of the drying air, so that the heat load of the dryer 3 can be increased. Can be reduced in size, and the equipment cost can be reduced.

  Various methods other than those shown in the above two embodiments are conceivable as methods for extracting the recirculation gas 11, but in short, heat obtained by the combustion of the combustible gas 16 obtained by thermal decomposition of waste. Utilizing energy is an essential feature of the present invention. Therefore, in practice, the present invention may be applied flexibly according to the arrangement conditions of each device, the amount of exhaust gas, and the temperature conditions.

Next, the configuration of the waste disposal apparatus according to the third embodiment of the present invention will be described with reference to FIGS.
FIG. 5 is a system block diagram showing a configuration of a waste disposal apparatus according to the third embodiment of the present invention. The same reference numerals as those in FIG. 1 indicate the same parts. FIG. 6 is an explanatory diagram of the relationship between the combustion temperature (TC) of the burner 18 and the oxygen concentration (O _2C ). FIG. 7 is a block diagram of oxygen concentration control means used in the waste disposal apparatus according to the third embodiment of the present invention. In addition, the same code | symbol as FIG. 3 has shown the same part.

  In the present embodiment, burner combustion gas oxygen concentration control means 500 is used instead of the burner combustion temperature control means 400 in the embodiment shown in FIG. The other configuration is the same as that shown in FIG.

The burner combustion gas oxygen concentration control means 500 shown in FIG. 5 receives a burner combustion gas oxygen concentration signal (O _2C ) 69 detected by an oxygen concentration meter 68 installed in the burner 18 and next so that this becomes a predetermined value. The four target flow rate commands are output. However, the four target flow rate commands are the same as those shown in the first, second, and third embodiments. That is, the first target flow rate command is a target flow rate command (F1) 54 for ensuring the primary air flow rate necessary for the primary air flow rate adjustment valve device 53. The second target flow rate command is a target flow rate command (F2) 56 for securing a necessary first heated air flow rate for the first heated air fan device 55. The third target flow rate command is a target flow rate command (F3) 58 for ensuring a necessary recirculated exhaust gas flow rate for the recirculated exhaust gas fan device 57. The fourth target flow rate command is a target flow rate command (F4) 60 for ensuring a necessary recirculated exhaust gas flow rate for the recirculated exhaust gas flow rate adjusting valve device 59 for burner exhaust gas temperature control.

Here, in the burner 18, there is a correlation as shown in FIG. 6 between the combustion temperature (TC) and the oxygen concentration (O _2C ). Therefore, similarly to the embodiment of FIG. 1 controlled based on the oxygen concentration, the flow rate can be controlled by the combustion temperature.

Next, the control method in the burner combustion gas oxygen concentration control means 500 will be described in more detail with reference to FIG. The burner combustion gas oxygen concentration control means 500 is a deviation between the burner combustion gas oxygen concentration setting means 70 for setting the burner combustion gas oxygen concentration target value (O _2CR ) and the burner combustion gas oxygen concentration signal (O _2C ) 69. Subtraction means 62A for obtaining (E), proportional integration means 63 for proportionally integrating deviation (E) with respect to time, and proportional constant K1 with respect to the basic flow rate command value (RF) obtained by proportional integration means 63 , K2, K3, K4 and multiplication means 64, 65, 66, 67 for obtaining the target flow rate commands (F1, F2, F3, F4), respectively. The proportional integration means 63 and multiplication means 64, 65, 66, and 67 are the same as those shown in FIG.

  Note that the subtractor 62A has an operational code opposite to that of the subtractor 62 in FIG. 3 due to the relationship between the detection signal and the output signal.

  The embodiment shown in FIG. 5 uses the burner combustion gas oxygen concentration control means 500 in place of the burner combustion temperature control means 400 in the embodiment shown in FIG. 1, but is shown in FIG. Instead of the burner combustion temperature control means 400 in the embodiment, a burner combustion gas oxygen concentration control means 500 may be used.

  As described above, according to the present embodiment, the recirculation exhaust gas 11 that has passed through the steam superheater 9 disposed in the subsequent stage of the air heaters 5 and 7 is used as a part of the heated air, so that the dryer 3 Therefore, the dryer can be downsized and the equipment cost can be reduced.

  In addition, this invention is not limited to the above-mentioned 1st-3rd embodiment, It can apply, without changing the essence also in embodiment described below.

  First, the first to third embodiments of the present invention are all directed to a waste gasification and melting apparatus configured as an apparatus having a combustion melting furnace 31, but do not have a combustion melting furnace 31, The present invention can be applied to a waste treatment apparatus in which the char 17 generated in the conversion furnace 100 is used in another combustion apparatus without changing the essence thereof. For example, instead of the combustion melting furnace 31, a waste treatment device that burns the fine char 36 with a normal combustion boiler, a combustion boiler that is installed separately at a remote location, or a material that is required for cement production, etc. Even when diverted to a heating fuel or the like, it does not depart from the essence of the present invention.

  In addition, the first to third embodiments of the present invention are all directed to the waste gasification and melting device configured as a device having the steam superheater 9 separately provided from the exhaust heat recovery boiler 200. It is not always necessary to limit to this apparatus configuration, and it is also possible to employ an exhaust heat recovery boiler with a built-in steam superheater. In this case, similar to the second embodiment of the present invention, a part of the exhaust gas supplied to the exhaust heat recovery boiler may be recirculated and does not depart from the essence of the present invention.

  In the first to third embodiments of the present invention, the primary air 19 and the secondary air 20 supplied to the burner 18 are respectively defined for combustion in a reducing atmosphere and an oxidizing atmosphere. It is not necessary to strictly define, and the same effect as described in the embodiment of the present invention can be obtained as a supply method in which each is further divided and supplied from a plurality of locations and has a partial flow extending over both atmospheres. Of course, it can be achieved.

  Moreover, although the 1st-3rd embodiment of this invention was set as the apparatus structure isolate | separated into the 1st air heater 5 and the 2nd air heater 7 as an air heater for drying, it does not necessarily need to isolate | separate. Even if the first heated air and the recirculated air are joined together and then led to one air heater, it does not depart from the essence of the present invention.

  In the first to third embodiments of the present invention, in order to calculate and output the target flow rate commands F1 to F2 as control methods, the multipliers 64 to 67 are constants for the basic flow rate command value RF, respectively. Although the method of multiplying by K1 to K4 is used, it is not necessarily limited to a constant, and the present invention can be implemented without any change in its essence as a method of determining by function calculation according to the conditions of device design.

  In the first to third embodiments of the present invention, the result of calculating the deviation (E) by the proportional integration means 63 is used as the basic flow rate command value RF as a control method. There is no need for limitation, and a method using a proportional-integral-derivative unit added with a differential operation or a method using only a proportional unit may be selected as appropriate according to the dynamic characteristics of the apparatus.

As described above, the waste gasification and melting apparatus and the control method thereof according to the present invention can increase the thermal efficiency because exhaust gas is used as a heat source for drying, eliminate the need for external fuel, and greatly reduce the environmental load caused by the exhaust gas. Further, there is an advantage that the dryer can be miniaturized because drying with a heating medium having a high temperature and low oxygen is possible. In addition, since it is possible to prevent the ignition of waste inside the dryer, the safety of operation is improved and the operating rate of the apparatus is also improved.

It is a system block diagram which shows the structure of the waste disposal apparatus by the 1st Embodiment of this invention. It is explanatory drawing of the effect by the waste disposal apparatus by the 1st Embodiment of this invention, and its physical basis. It is a block diagram of the burner combustion temperature control means used for the waste disposal apparatus according to the first embodiment of the present invention. It is a system block diagram which shows the structure of the waste disposal apparatus by the 2nd Embodiment of this invention. It is a system block diagram which shows the structure of the waste disposal apparatus by the 3rd Embodiment of this invention. It is explanatory drawing of the relationship between the combustion temperature (TC) of a burner 18, and oxygen concentration ( _O2C ). It is a block diagram of the oxygen concentration control means used for the waste disposal apparatus by the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Waste pit 2 ... Waste 3 ... Dryer 4 ... Drying air 5 ... 1st air heater 6 ... 1st heating air 7 ... 2nd air heater 8 ... Recirculation air 9 ... Steam superheater 10 ... Steam superheater exhaust gas 11 ... Recirculated exhaust gas 12 ... Dry waste 13 ... Drum 14 ... Jacket 15 ... Combustion gas 16 ... Combustible gas 17 ... Char 18 ... Burner 19 ... Primary air 20 ... Secondary air 21 ... Burner exhaust gas temperature control Recirculation exhaust gas 22 ... Burner exhaust gas 23 ... Jacket bypass gas 24 ... Jacket outlet gas 25 ... Gasifier exhaust gas 26 ... Air heating gas 27 ... Air heater bypass gas 28 ... Air heating exhaust gas 29 ... Steam superheater exhaust gas 30 ... char combustion air 31 ... combustion melting furnace 32 ... quenching gas 33 ... char treatment device 34 ... fine powder char 35 ... char hopper 36 ... combustion char 38 ... air fan 3 ... Steam 39 ... Fan supply air 40 ... Circulating air fan 41 ... Boiler feed water 42 ... Boiler drum 43 ... Superheated steam 44 ... Steam turbine 45 ... Generator 46 ... Exhaust gas 47 ... Exhaust gas treatment device 48 ... Chimney 49 ... Condenser 50 ... boiler feed water pump 51 ... thermometer 52 ... burner combustion temperature signal _(T C)
53 ... Primary air flow rate adjusting valve device 54 ... Target flow rate command (F1)
55 ... First heated air fan device 56 ... Target flow rate command (F2)
57 ... Recirculation exhaust gas fan device 58 ... Target flow rate command (F3)
59 ... Recirculation exhaust gas flow rate regulating valve device 60 for burner exhaust gas temperature control ... Target flow rate command (F4)
61 ... burner combustion temperature setting means 62 ... subtraction means 63 ... proportional integration means 63a ... multiplication means 63b ... multiplication means 63c ... integration means 63d ... addition means 64 ... multiplication means 65 ... multiplication means 66 ... multiplication means 67 ... multiplication means 68 ... Oxygen concentration meter 69 ... Burner combustion gas oxygen concentration signal (O _2C )
70 ... burner combustion gas oxygen concentration setting means 100 ... gasifier 200 ... exhaust heat recovery boiler 300 ... turbine power generator 400 ... burner combustion temperature control means 500 ... burner combustion gas oxygen concentration control means

Claims (7)

A dryer for removing moisture contained in waste by heated air, a gasification furnace for thermally decomposing dry waste dried by this dryer into pyrolysis gas and char, and this pyrolysis gas A burner for introducing the high-temperature combustion gas obtained by combustion to the gasifier and using it as a heat source for pyrolysis, and heating the air with the exhaust gas after heating the gasifier, In a waste treatment apparatus comprising an air heater for obtaining
A waste treatment apparatus comprising a first recirculation exhaust gas path for mixing a part of exhaust gas that has passed through the air heater into the heated air before being led to the dryer. The waste treatment apparatus according to claim 1, further comprising:
A combustion melting furnace for burning the char to melt incombustibles in the char;
An exhaust heat recovery boiler for generating steam using the retained heat of the exhaust gas of the combustion melting furnace,
A steam superheater for superheating steam generated from the exhaust heat recovery boiler by exhaust gas that has passed through the air heater;
The waste reprocessing apparatus according to claim 1, wherein the first recirculation exhaust gas path is a path for mixing a part of the exhaust gas that has passed through a steam superheater disposed in a subsequent stage of the air heater into the heated air. The waste treatment apparatus according to claim 1, further comprising:
A primary air supply path for supplying primary air for burning the pyrolysis gas in a reducing atmosphere to the burner;
A second recirculation exhaust gas path for mixing a part of the exhaust gas that has passed through the air heater at the exhaust gas outlet of the burner;
The combustion state of the burner is detected, and based on the detected state, the flow rate of the heated air, the flow rate of the first recirculated exhaust gas, the flow rate of the primary air, and the second recirculated exhaust gas A waste disposal apparatus comprising a control means for adjusting a flow rate. The waste treatment apparatus according to claim 3, wherein
The waste treatment apparatus characterized in that the control means adjusts both the flow rate of the heated air and the flow rate of the primary air to increase or decrease both so that the combustion state of the burner becomes a predetermined state. . The waste treatment apparatus according to claim 3, wherein
The control means increases the flow rate of the first recirculation exhaust gas and the flow rate of the second recirculation exhaust gas so as to decrease the other when increasing one, so that the burner combustion state becomes a predetermined state. A waste treatment apparatus characterized by adjusting to the above. The waste treatment apparatus according to claim 3, wherein
As the combustion state of the burner, the combustion temperature of the burner is detected,
The control means controls the flow rate of the heated air, the flow rate of the first recirculated exhaust gas, the flow rate of the primary air, and the second recirculated exhaust gas so that the combustion temperature of the burner becomes a predetermined value. A waste treatment apparatus characterized by adjusting a flow rate. The waste treatment apparatus according to claim 3, wherein
As the burner combustion state, the oxygen concentration of the burner combustion gas is detected,
The control means controls the flow rate of the heated air, the flow rate of the first recirculated exhaust gas, the flow rate of the primary air, and the second recycle gas so that the oxygen concentration of the combustion gas of the burner becomes a predetermined value. A waste treatment apparatus that adjusts the flow rate of circulating exhaust gas.

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