JP7477198B2 - Combustion system and combustion method - Google Patents

Description

The present invention relates to a combustion system and a combustion method that uses an oxidizing agent to burn waste, and in particular to a technology for suppressing carbon dioxide emissions and reducing the amount of exhaust gas released into the atmosphere.

Conventionally, so-called stoker-type incinerators have been used to treat general waste and industrial waste. Stoker-type incinerators are incinerators in which waste moves forward as multiple fire grates called stokers are arranged in the front-to-back and left-to-right directions, causing the waste to gradually dry and burn as it moves forward. Despite its relatively simple structure, it is capable of treating large amounts of waste regardless of the moisture content or evaporation rate of the waste fed in, and is therefore adopted in many incineration treatment facilities.

In a stoker-type incinerator, the entire grate is usually made up of three stokers: a drying stoker, a combustion stoker, and a post-combustion stoker. Air is supplied from under each stoker to dry, combust, and post-combust the waste.

Generally, the waste put into an incinerator often does not have a constant property or composition. Therefore, in order to stabilize the combustion on the stoker, the feed speed of each of the drying, combustion, and post-combustion stokers is controlled. Also, the air supplied from below the stoker is divided into separate units, and the amount of air supplied to each unit is controlled to ensure stable combustion. Alternatively, the air supplied from below the stoker is mixed with recirculated combustion exhaust gas and oxygen to change the oxygen concentration, thereby suppressing or promoting combustion and ensuring stable combustion.

However, this type of control mainly relies on adjusting the amount of air, and if too much air is supplied to an area where combustible waste is concentrated, it is unavoidable that the grate will burn due to a localized rise in temperature.

In addition, in recent years, various attempts have been considered to capture the carbon dioxide contained in combustion exhaust gas to prevent global warming. However, the combustion exhaust gas discharged from stoker incinerators contains a large amount of nitrogen contained in the combustion air, so the concentration of carbon dioxide is low and the flow rate of the combustion exhaust gas is also high, so a huge amount of energy is required to separate and capture the carbon dioxide.

In an attempt to efficiently separate and capture carbon dioxide contained in combustion exhaust gas, it has been proposed in the field of coal-fired boiler technology to use a mixture of oxygen and recirculated combustion exhaust gas in a specified ratio, rather than air as the oxidizing agent for combustion (Non-Patent Document 1, Non-Patent Document 2).

According to the inventions described in Non-Patent Documents 1 and 2, when a mixture of oxygen and recirculated gas is used as an oxidizing agent, the main component of the combustion exhaust gas discharged from the boiler is carbon dioxide. A portion of the carbon dioxide discharged from the boiler is mixed with oxygen as the recirculated gas, and the remainder is separated and recovered. This combustion technology is called O2/CO2 combustion, since the main components of the oxidizing agent are oxygen and carbon dioxide.

By performing O2/CO2 combustion, the carbon dioxide concentration in the flue gas can be increased to approximately 97%, and the flue gas flow rate is approximately one-fifth of that in air combustion, making it possible to separate and capture carbon dioxide more economically.

However, even if this type of O2/CO2 combustion is applied to a stoker-type incinerator, combustion control is still performed by adjusting the stoker feed rate and the amount of oxidant supplied, so burning of the fire grate due to localized temperature increases is unavoidable. In addition, Patent Documents 1, 2, and 3 propose methods for controlling the oxygen concentration of the oxidant supplied to the stoker, but these methods are not based on the assumption of separating and capturing carbon dioxide, and instead focus solely on controlling combustion (Patent Documents 1, 2, and 3).

Terutoshi Uchida, "Toward the realization of a coal-fired power plant that does not emit CO2 using oxyfuel combustion - Operational status of the Callide oxyfuel combustion project", Proceedings of the Thermal and Nuclear Power Generation Conference 2013, April 2014 Sumie Nakayama and 3 others, "CO2 capture type coal-fired power generation system using O2/CO2 combustion," Energy and Resources, Vol. 14, No. 1 (1993)

JP 2006-57963 A JP 2020-91054 A JP 2006-242490 A

The present invention was made in consideration of these problems, and aims to provide a combustion system and a combustion method that can efficiently separate and capture carbon dioxide, and can prevent localized temperature increases in a stoker-type incinerator, thereby preventing burnout of the fire grate.

The present invention provides the following solutions:

The invention according to the first aspect is a combustion system comprising a stoker-type incinerator having a plurality of stokers that supply an oxidant from below, an oxidant supplying means that supplies a gas in which oxygen is mixed with recirculated combustion exhaust gas as an oxidant to the plurality of stokers, and an oxygen concentration adjusting means that adjusts the oxygen concentration of the oxidant supplied to the plurality of stokers for each stoker, and a carbon dioxide separation means that separates and recovers carbon dioxide in the combustion exhaust gas discharged from the stoker-type incinerator.

According to the invention relating to the first feature, by using oxygen and recirculated gas as oxidizing agents, the components in the combustion exhaust gas become almost entirely carbon dioxide and water. In other words, the carbon dioxide concentration in the combustion exhaust gas can be increased compared to when air is used as the oxidizing agent, making it possible to efficiently capture carbon dioxide in the carbon dioxide separation means. In addition, the flow rate of the combustion exhaust gas discharged from the stoker-type incinerator is half or less compared to when air is used as the oxidizing agent, making it possible to miniaturize the carbon dioxide separation means.

In addition, by supplying each stoker with an oxidizer with an adjusted oxygen concentration, the oxygen required for combustion can be supplied to each stoker, and the combustion in each stoker can be appropriately controlled, avoiding localized temperature increases and preventing the fire grate from burning.

The second aspect of the invention is the first aspect of the invention, in which the oxygen concentration adjustment means is composed of an oxygen supply amount adjustment means that adjusts the amount of oxygen mixed into the recirculated combustion exhaust gas for each stoker.

According to the invention relating to the second feature, the recirculated flue gas flow rate is fixed, and the flow rate of oxygen mixed into the flue gas is adjusted for each stoker to adjust the individual oxygen concentrations, so that oxygen concentrations can be adjusted according to the individual combustion conditions without increasing the overall flue gas flow rate. Since there is no significant change in the overall flue gas flow rate, exhaust gas treatment equipment such as carbon dioxide separation means can also be made smaller.

The invention according to the third characteristic is the invention according to the first or second characteristic, and includes a combustion state detection means for detecting the combustion state on the multiple stokers, and a control means for controlling the oxygen concentration of the oxidizer supplied to a specific stoker among the multiple stokers according to the combustion state detected by the combustion state detection means.

According to the third feature of the invention, the oxygen concentration of the oxidizer supplied to a specific stoker is controlled according to the combustion state in each region of the multiple stokers, so that local temperature increases in the stoker can be suppressed and the thermal loss of the incineration residue can be suppressed to below the regulated value.

The fourth feature of the invention is the third feature of the invention, in which the combustion exhaust gas after temperature reduction and dust collection is used as the recirculation gas.

According to the invention relating to the fourth feature, the combustion exhaust gas after removing acidic components and impurities by dust collection is recycled and used as an oxidizing agent, so the oxidizing agent is composed almost entirely of carbon dioxide and oxygen. This makes it possible to increase the carbon dioxide concentration in the combustion exhaust gas, and to separate and capture carbon dioxide with high efficiency.

The fifth aspect of the invention is the third aspect of the invention, in which oxygen produced by pressure swing adsorption (PSA) is used as the oxygen to be mixed with the recirculated combustion exhaust gas.

According to the fifth aspect of the invention, by using high-purity oxygen produced by pressure swing adsorption (PSA) as part of the oxidant, the oxidant components can be made up almost entirely of carbon dioxide and oxygen. This makes it possible to increase the carbon dioxide concentration in the combustion exhaust gas, and to separate and capture carbon dioxide more efficiently.

The sixth aspect of the invention is the third aspect of the invention, further comprising a water separation means for separating moisture from the combustion exhaust gas discharged from the stoker-type incinerator, and the carbon dioxide separation means separates carbon dioxide from the combustion exhaust gas from which moisture has been separated by the water separation means.

According to the sixth aspect of the invention, carbon dioxide is separated from the combustion exhaust gas after the water has been removed by the water separation means, so that the carbon dioxide concentration in the combustion exhaust gas treated by the carbon dioxide separation means can be increased, and carbon dioxide can be separated and recovered more efficiently.

The invention according to the seventh characteristic is the invention according to the third characteristic, and is provided with a water separation means for separating water from the combustion exhaust gas discharged from the stoker-type incinerator, and a water electrolysis device for electrolyzing the water separated by the water separation means, and uses the oxygen generated by electrolysis in the water electrolysis device as the oxygen to be mixed with the recirculated combustion exhaust gas.

According to the seventh aspect of the invention, by using oxygen generated by electrolyzing water separated and recovered from combustion exhaust gas as part of the oxidizing agent, the oxygen used as the oxidizing agent can be supplied within the waste treatment process system, and energy for transporting or generating oxygen can be saved.

The eighth aspect of the invention is the third aspect of the invention, in which air is used as an oxidizer for secondary combustion.

According to the eighth aspect of the invention, by using air as an oxidizer for secondary combustion, it is possible to reduce the energy required to generate oxygen. In addition, secondary combustion using air as an oxidizer is limited to a temperature range where thermal NOx is unlikely to be generated, so there is no significant increase in the amount of NOx generated.

The invention according to the ninth aspect is a combustion method using a stoker-type incinerator equipped with multiple stokers that supply an oxidizing agent from below, and includes the steps of: supplying a gas in which oxygen is mixed with recirculated combustion exhaust gas to the multiple stokers as an oxidizing agent; adjusting the oxygen concentration of the oxidizing agent supplied to the multiple stokers for each stoker; and separating and recovering carbon dioxide in the combustion exhaust gas discharged from the stoker-type incinerator.

According to the ninth aspect of the invention, as with the first aspect, oxygen and recirculated gas are used as oxidizing agents, so that the components in the flue gas are mostly carbon dioxide and water. In other words, the carbon dioxide concentration in the flue gas can be increased compared to when air is used as the oxidizing agent, making it possible to efficiently capture carbon dioxide in the carbon dioxide separation means. In addition, the flow rate of the flue gas discharged from the stoker-type incinerator is half or less compared to when air is used as the oxidizing agent, so the carbon dioxide separation means can be made smaller.

The present invention provides a combustion system and a combustion method that can efficiently separate and capture carbon dioxide, and can prevent localized temperature increases in a stoker-type incinerator, thereby preventing burnout of the fire grate.

FIG. 1 is a schematic diagram showing a combustion system using a stoker-type incinerator according to the present invention. FIG. 2 is a schematic diagram showing an oxidant supplying means of the stoker type incinerator according to the present invention. FIG. 3 is a flow diagram showing a combustion method using a stoker-type incinerator according to the first embodiment. FIG. 4 is a flow diagram showing a combustion method using a stoker-type incinerator according to the second embodiment.

Below, an embodiment of the present invention will be described with reference to the drawings. Note that this is merely an example, and the technical scope of the present invention is not limited to this. Note that in the present invention, the term oxidizing agent includes not only gases for oxidizing waste materials, but also gases used for drying.

[Overall configuration of a combustion system using a stoker-type incinerator]
The overall configuration of a combustion system using a stoker-type incinerator 100 according to this embodiment will be described with reference to FIG.

Figure 1 shows a schematic diagram of the combustion system according to this embodiment, which is composed of a stoker-type incinerator 100, an exhaust gas cooling device 200, a bag filter 300, a water separation means 400, an exhaust gas recirculation blower 500, a carbon dioxide separation means 600, a water electrolysis device 700, an oxygen generation device 800, a control device 900, and a chimney (not shown).

As shown in FIG. 1, the stoker-type incinerator 100 of this embodiment incinerates waste such as general waste of irregular shape and industrial waste, and is equipped with a combustion chamber 110 equipped with multiple stokers 130 consisting of a drying stoker 131 located at the most upstream side as viewed from the upstream side of the flow of waste input, combustion stokers 132 to 135, and a post-combustion stoker 136 located at the most downstream side, a supply device 120 that supplies waste to the combustion chamber 110, an oxidizing agent supplying means 140 that supplies oxidizing agent to the combustion chamber 110 through the stoker 130 from a wind box located below the stoker 130, an incineration residue discharge mechanism 150 that discharges incineration residue, a combustion state detection means 160, a secondary oxidizing agent supplying means 170 that supplies additional oxidizing agent to the combustion chamber, and a cooling water tank (not shown).

The supply device 120 is composed of supply means such as a hopper and a pusher that temporarily store waste. It stores waste supplied to the supply device 120 by a waste crane from a waste pit (not shown) and intermittently feeds it into the combustion chamber 110.

The stoker 130 is composed of multiple stages of grates, consisting of the drying stoker 131, the combustion stokers 132-135, and the post-combustion stoker 136, each of which slides back and forth at a predetermined transport speed. In addition, below the drying stoker 131, the combustion stokers 132-135, and the post-combustion stoker 136, wind boxes 131W-136W, which are connected to the oxidizer supply means 140, are provided, respectively.

Because of this structure, the waste supplied to the combustion chamber 110 by the supply device 120 advances downstream of the combustion chamber 110, that is, toward the incineration residue discharge mechanism 150, as the grate slides or swings, and is dried, combusted, and post-combusted by the oxidizer supplied by the oxidizer supply means 140 according to each stage. In other words, the drying grate 131 is supplied with an oxidizer for drying from below, and the waste on the drying stoker 131 is dried as the moisture evaporates and supplied to the combustion stoker 132. The combustion stokers 132 to 135 are supplied with an oxidizer for combustion from below, and the waste on the combustion stokers 132 to 135 is combusted by the oxidizer and supplied to the post-combustion stoker 136. The post-combustion stoker 136 is supplied with an oxidizer for post-combustion from below, and the waste on the post-combustion stoker 136 is post-combusted by the oxidizer. The waste post-combusted in the post-combustion stoker 136 is sent to the incineration residue discharge mechanism 150 and discharged into a cooling water tank (not shown) provided below.

The incineration residue discharge mechanism 150 is composed of gates and dampers (not shown), and discharges the waste that has been post-combusted in the post-combustion stoker 136 at predetermined intervals into a cooling water tank located below.

The combustion state detection means 160 is installed to detect the combustion state in the combustion chamber 110, preferably the individual combustion states on each of the stokers 131-136, and is composed of, for example, a temperature detection means for detecting the temperature inside the combustion chamber above each of the stokers 131-136, an infrared camera or a light quantity sensor for detecting the position of the burnout point of the waste, etc. However, the combustion state detection means 160 is not limited to the above, as long as it can detect the combustion state on each of the stokers 131-136.

The secondary oxidant supply means 170 supplies additional oxidant into the combustion chamber 110 to completely burn the unburned fuel that cannot be completely burned with the oxidant supplied from the oxidant supply means 140. In this way, the waste is combusted by the oxidant supply means 140 and the secondary oxidant supply means 170, and the combustion exhaust gas generated by the combustion is sent to the exhaust gas cooling device 200.

The exhaust gas cooling device 200 reduces the temperature of the combustion exhaust gas discharged from the stoker-type incinerator 100 to a temperature at which it can be supplied to the bag filter 300, and is approximately 200°C or less as stated in the "Guidelines for preventing the generation of dioxins in waste treatment." For example, it is composed of a waste gas boiler 210 and economizer 220 that generate steam using the heat of the combustion exhaust gas, and a temperature reducing tower 230 that sprays cooling water to cool the combustion exhaust gas.

The bag filter 300 is equipped with a filter cloth that collects and filters the combustion exhaust gas that has been cooled by the exhaust gas cooling device 200, and removes soot and harmful components contained in the combustion exhaust gas. A chemical supply device (not shown) for injecting chemicals into the bag filter 300 is disposed in the exhaust gas flue at the bag filter inlet. The alkaline chemicals supplied from the chemical supply device cause a neutralization reaction with the acidic components in the combustion exhaust gas on the filter cloth of the bag filter 300, thereby purifying the combustion exhaust gas.

The water separation means 400 separates and recovers the water in the combustion exhaust gas, and is composed of a water vapor separation device 410 that separates water vapor from the combustion exhaust gas whose temperature has been reduced through the exhaust gas cooling device 200 and the bag filter 300 and from which acidic components and impurities have been filtered out, and a condenser 420 that condenses the water vapor separated from the combustion exhaust gas by the water vapor separation device 410 to produce condensed water.

The exhaust gas recirculation blower 500 is a blower that is placed downstream of the bag filter 300, and is used to suck in the combustion exhaust gas from which soot and harmful components have been removed by the bag filter 300, and to supply a portion of it to the stoker-type incinerator 100 as an oxidizing agent.

The carbon dioxide separation means 600 selectively separates the carbon dioxide contained in the combustion exhaust gas discharged from the stoker-type incinerator 100 and purified by the bag filter 300. The means for separating the carbon dioxide from the combustion exhaust gas may be separation using a separation membrane, chemical adsorption, physical adsorption, or cryogenic separation.

The water electrolysis device 700 electrolyzes water to generate oxygen and hydrogen. In this embodiment, the water electrolysis device 700 is composed of an electrolytic cell that stores water, a power source, an anode that is connected to the positive electrode of the power source, and a cathode that is connected to the negative electrode of the power source.

The oxygen generator 800 supplies oxygen as an oxidant to the oxidant supply means 140 of the stoker-type incinerator 100, and is connected to the oxygen supply passage described below.

The control device 900 controls the oxidant supply means 140, the recirculation blower 500, the water electrolysis device 700, etc. according to the combustion state of the stoker-type incinerator 100.

[Configuration of oxidant supply means]
Next, the oxidizing agent supplying means 140 of the stoker type incinerator 100 according to this embodiment will be described with reference to FIG.

The oxidant supplying means 140 according to this embodiment supplies oxidant with an individually adjusted oxygen concentration to each of the stokers 131-136. The oxidant supplying means 140 comprises oxidant supply passages 141a-146a that supply oxidant with an adjusted flow rate and oxygen concentration to the wind boxes 131W-136W disposed below each of the stokers, oxidant flow rate adjusting means 141b-146b that adjust the flow rate of the oxidant supplied to each of the stokers, oxygen supply passages 142c-146c that mix oxygen into the recirculated gas supplied to each of the stokers, and oxygen flow rate adjusting means 142d-146d that adjust the flow rate of oxygen mixed into the recirculated gas.

The oxidizer supplied to the oxidizer supply passage 140a is either recirculated combustion exhaust gas alone or a mixture of recirculated gas and oxygen with an adjusted flow rate. This will be explained in detail below.

The oxidant supply means 141 that supplies oxidant to the drying stoker 131 consists of an oxidant supply path 141a and an oxidant flow rate adjustment means 141b. The drying stoker 131, which is the stoker located at the most upstream, does not need to supply oxygen because it mainly dries waste. Therefore, without connecting an oxygen supply path, only recirculated gas is supplied to the drying stoker 131 via the oxidant supply path 141a and the oxidant flow rate adjustment means 141b.

In the combustion stokers 132, 133, 134, and 135 arranged in multiple stages, an oxidant mixed with oxygen is supplied to combust the dried waste. Therefore, the oxidant supplying means 142-145 that supplies the oxidant to the combustion stokers 132-135 are composed of oxidant supply paths 142a-145a, oxidant flow rate adjusting means 142b-145b, oxygen supply paths 142c-145c, and oxygen flow rate adjusting means 142d-145d, and the gas in which the oxygen whose flow rate is individually adjusted by the oxygen flow rate adjusting means 142d-145d is mixed with the recirculated gas is supplied to the combustion stokers 132-135 as the oxidant.

In the post-combustion stoker 136, which is the stoker located at the most downstream, an oxidizing agent containing oxygen is supplied because it is necessary to burn the unburned waste after combustion and to keep the incineration residue's thermal loss below a standard value. Therefore, the oxidizing agent supplying means 146 that supplies the oxidizing agent to the post-combustion stoker 136 consists of an oxidizing agent supply path 146a, an oxidizing agent flow rate adjustment means 146b, an oxygen supply path 146c, and an oxygen flow rate adjustment means 146d, and supplies the post-combustion stoker 136 with a gas mixed with the recirculating gas, with the flow rate of oxygen adjusted by the oxygen flow rate adjustment means 146d.

In this way, the oxidant supplying means 142-146 that supply oxidant to each combustion stoker 132-135 and post-combustion stoker 136 are each equipped with oxygen flow rate adjusting means 142d-146d, and supply oxidant with individually adjusted oxygen concentration to each stoker 132-136.

As shown in FIG. 2, the secondary oxidant supply means 170 is composed of an oxidant supply path 170a, an oxidant flow rate adjustment means 170b, an oxygen supply path 170c, and an oxygen flow rate adjustment means 170d, and recirculated gas mixed with oxygen as a secondary oxidant is supplied to the combustion chamber 110. Alternatively, air may be supplied as the secondary oxidant by a blower.

[Combustion method]
Next, a combustion method using the stoker-type incinerator 100 according to this embodiment will be described. A situation will be described in which drying, combustion, and post-combustion are already performed on each of the stokers 131 to 136 during normal combustion operation. In this case, the combustion exhaust gas recirculated by the recirculation blower 500 and the oxygen generated by the water electrolysis device 700 or the oxygen generation device 800 are supplied to the oxidizing agent supply means 140. In addition, the carbon dioxide separation means 600 separates and recovers the carbon dioxide in the combustion exhaust gas discharged from the stoker-type incinerator 100.

The oxidant is then supplied by the oxidant supply means 140 configured as described above as follows:

First, only the recirculated gas supplied from the recirculation blower 500 is supplied to the drying stoker 131 via the oxidant supply passage 141a and the oxidant flow rate adjustment means 141b.

In addition, for the combustion stokers 132-135 arranged in multiple stages, the oxygen concentration of the oxidant supplied to each stoker is controlled based on the detection results of the combustion state detection means 160 that detects the combustion state within the combustion chamber 110. At this time, the control device 900 individually controls the oxygen flow rate adjustment means 142d-145d to individually adjust the flow rate of oxygen mixed into the recirculated gas, and adjusts the oxygen concentration of the oxidant supplied to each combustion stoker 132-135 to an appropriate oxygen concentration according to the combustion state.

At this time, the control device 900 controls the feed rate of each stoker and the amount of oxidant supplied to each stoker.

In addition, in the post-combustion stoker 136, since it is necessary to burn the unburned waste after combustion and keep the incineration residue's calorific loss below a standard value, an oxidizer with an oxygen concentration adjusted to be higher than the atmospheric oxygen concentration (for example, about 24 to 28%) is supplied. Even in this case, the control device 900 controls the oxygen flow rate adjustment means 146d to adjust the flow rate of oxygen mixed into the recirculated gas, and adjust the oxygen concentration of the oxidizer supplied to the post-combustion stoker 136 to the desired concentration.

Next, a specific embodiment of the combustion method using the stoker-type incinerator 100 according to the present invention will be described. Note that the description will be given for a situation during normal combustion operation, when drying, combustion, and post-combustion have already been performed on each of the stokers 131 to 136.

<Embodiment 1>
First, the combustion method according to the first embodiment will be described with reference to Fig. 3. In the first embodiment, the combustion state detection means 160 uses a temperature detection means for detecting a local temperature rise.

[Step S100: Detection of Combustion State]
First, the combustion state detection means 160 detects the temperature inside the combustion chamber in the areas corresponding to each of the stokers 131 to 136 (step S100).

[Step S110: Determination of Combustion State]
When detection of the combustion state is started in step S100, the control means 900 executes a process of determining whether or not the temperature inside the combustion chamber in the area corresponding to each of the stokers 131 to 136 exceeds a predetermined temperature (step S110).

[Step S120: Adjustment of oxygen concentration and/or transfer speed]
In step S110, the stoker corresponding to the area determined to have a temperature exceeding the predetermined temperature (Y in step S110) is determined to have a local temperature rise, and the control means 900 adjusts the oxygen concentration of the oxidant supplied to the oxidant supply means 140 and/or the transfer speed of the stokers 131-136 so that the detected temperature falls within a predetermined range (step S120). Then, steps S110 and S120 are repeated until the temperature detection result falls within the predetermined range.

In this case, oxygen flow rate adjustment means 142d to 146d are used to change the oxygen concentration of the oxidant supplied to the oxidant supply means 140.

In other words, if it is determined that a local temperature rise is occurring in any of the stokers, the oxygen flow rate is controlled to be reduced by the oxygen flow rate adjustment means 140d corresponding to the area where the local temperature rise is determined to be occurring, in order to suppress combustion. In this way, the proportion of recirculated gas, i.e., the proportion of carbon dioxide, is increased in the oxidizer supplied to the area where the temperature rise is occurring, and combustion can be performed in an oxygen-deficient state, suppressing combustion and lowering the temperature.

Moreover, in the present invention, the oxygen concentration of the oxidant supplied to each stoker can be changed individually, eliminating localized temperature increases without changing the combustion exhaust gas flow rate or NOx generation rate of the entire system.

In step S110, if the stoker is determined to not have exceeded the predetermined temperature (N in step S110), the stoker will continue combustion without changing the oxygen concentration of the oxidizer or the transport speed of the stoker.

<Embodiment 2>
Next, a combustion method according to the second embodiment will be described with reference to Fig. 4. In the second embodiment, an infrared camera (not shown) disposed in the combustion chamber 110 is used as the combustion state detection means 160 in order to detect the position of the burnout point.

[Step S200: Detection of Combustion State]
First, the combustion state detection means 160 detects the position of the burnout point (step S200), and identifies which of the combustion stokers 132 to 135 the burnout point is located at.

[Step S210: Determination of Burnout Point Position]
In step S200, when the combustion stoker in the area where the burnout point exists is identified, it is determined whether the combustion stoker identified as being in the area where the burnout point exists matches the position of the designed burnout point (step S210). That is, in a stoker-type incinerator, the designed burnout point is predetermined, and in step S210, it is determined whether the combustion stoker in the area where the detected burnout point exists matches the combustion stoker in the area corresponding to the designed burnout point.

[S220: Adjustment of oxygen concentration]
In step S210, if it is determined that the combustion stoker in the area where the detected burnout point exists is the combustion stoker in the area corresponding to the design burnout point (Y in step S210), the oxygen concentration of the oxidizer supplied to each combustion stoker is controlled (step S220).

That is, in the combustion stoker identified in step S200 as being at the burnout point, the control means 900 controls the oxygen flow rate adjustment means 140d to reduce the oxygen concentration of the oxidizer supplied. By lowering the oxygen concentration of the oxidizer supplied near the burnout point, it is possible to suppress the local temperature rise near the burnout point and reduce the generation of NOx.

In addition, in the combustion stoker downstream of the combustion stoker that has reached the burnout point, the oxygen flow rate adjustment means 140d is controlled so that the oxygen concentration of the oxidizer is approximately 24-28%, that is, the oxygen concentration is higher than that of the atmosphere, so that no unburned fuel remains. In this way, local temperature increases in each combustion stoker can be suppressed, and at the same time, the thermal loss of the incineration residue can be suppressed to below the regulated value.

When a predetermined time has elapsed after step S220 is performed, the process returns to step S200 and repeats steps S200 and subsequent steps.

[S230: Setting of Combustion Conditions]
On the other hand, if it is determined in step S210 that the combustion stoker in the area where the detected burnout point exists is not the combustion stoker in the area corresponding to the designed burnout point (N in step S210), new combustion conditions are set so that the burnout point moves to the designed burnout point (step S230), and combustion control is performed according to the set combustion conditions. At this time, one or more parameters of the amount of waste supplied, the feed rate of each stoker, the amount of oxidizer supplied, and the oxygen concentration of the oxidizer are set as new combustion conditions. The control means 900 issues commands to each device based on the newly set combustion conditions. After a predetermined time has elapsed after the command, the process returns to step S200, and the steps following step S200 are repeated.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Furthermore, the effects described in the embodiments of the present invention are merely a list of the most favorable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments of the present invention.

The above-mentioned embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to having all of the configurations described.

The combustion system and method using the stoker-type incinerator of this invention can be applied to waste incineration facilities that incinerate various types of waste, such as household waste, industrial waste, medical waste, and sewage sludge. Furthermore, the technology of this invention can be applied not only to waste incineration facilities that incinerate waste, but also to combustion devices that burn various solid fuels, including biomass, on multiple stokers.

100 Stoker type incinerator 110 Combustion chamber 120 Supply device 130 Stoker 131 Drying stoker 132-135 Combustion stoker 136 Post-combustion stoker 140 Oxidant supply means 140a Oxidant supply path 140b Oxidant flow rate adjustment means 140c Oxygen supply path 140d Oxygen flow rate adjustment means 150 Incineration residue discharge mechanism 160 Combustion state detection means 170 Secondary oxidant supply means 200 Exhaust gas cooling device 300 Bag filter 400 Water separation means 500 Exhaust gas recirculation blower 600 Carbon dioxide separation means 700 Water electrolysis device 800 Oxygen generation device 900 Control means

Claims (5)

A stoker-type incinerator including a plurality of stokers for supplying an oxidant from below, an oxidant supplying means for supplying a gas obtained by mixing oxygen with recirculated combustion exhaust gas as an oxidant to the plurality of stokers, and an oxygen concentration adjusting means for adjusting the oxygen concentration of the oxidant supplied to the plurality of stokers for each of the stokers;
A bag filter having a filter cloth that neutralizes acidic components in the combustion exhaust gas discharged from the stoker-type incinerator and removes soot and dust by blowing in an alkaline agent;
a water separation means for separating water from the combustion exhaust gas from which the soot and acidic components have been removed through the bag filter;
a recirculation blower that supplies the combustion exhaust gas from which soot and acidic components have been removed through the bag filter and from which water has been separated by the water separation means as the recirculation gas to the oxidant supply means;
a carbon dioxide separation means for separating and recovering carbon dioxide in the combustion exhaust gas from which water has been separated by the water separation means ;
A combustion system comprising: The oxygen concentration adjusting means is configured by an oxygen supply amount adjusting means that adjusts the supply amount of oxygen mixed into the recirculated gas for each stoker.
The combustion system of claim 1 . A combustion state detection means for detecting a combustion state on the plurality of stokers;
A control means for controlling an oxygen concentration of the oxidant supplied to a predetermined stoker among the plurality of stokers in accordance with the combustion state detected by the combustion state detection means.
A combustion system according to claim 1 or 2. a water electrolysis device that electrolyzes the water separated by the water separation means,
The oxygen mixed with the recirculated gas is oxygen generated by electrolysis in the water electrolysis device.
The combustion system of claim 3. A combustion method using a stoker-type incinerator equipped with multiple stokers for supplying oxidizer from below,
supplying a gas obtained by mixing oxygen with recirculated combustion exhaust gas as an oxidant to the plurality of stokers;
Adjusting the oxygen concentration of the oxidant supplied to the plurality of stokers for each of the stokers;
A step of filtering the combustion exhaust gas discharged from the stoker-type incinerator with a filter cloth into which an alkaline agent has been blown, thereby neutralizing acidic components in the combustion exhaust gas and removing soot and dust;
A step of separating moisture from the combustion exhaust gas from which the soot and acidic components have been removed;
supplying the combustion exhaust gas from which the soot and acidic components have been removed and from which the moisture has been separated as the recirculated gas to the plurality of stokers ;
A step of separating and recovering carbon dioxide in the combustion exhaust gas from which moisture has been separated ;
A combustion method comprising: