Fluidized bed gasification system

Abstract

This utility model discloses a fluidized bed gasification system, which includes a fluidized bed gasifier and a cooling device, a first dust removal device, and a cooling and scrubbing device connected in series at the syngas outlet of the fluidized bed gasifier. The cooling device is used to cool the syngas flowing out of the syngas outlet of the fluidized bed gasifier. The first dust removal device is used to collect fly ash from the syngas flowing out of the cooling device. The cooling and scrubbing device is used to wash the fly ash from the syngas flowing out of the first dust removal device. Based on the fluidized bed gasification system of this utility model, the resulting net syngas has a high CO content, low H2 and CO2 content, small wastewater and circulating water volume, low syngas dew point, and low heat loss from the gasifier.

Description

Technical Field

[0001] This utility model relates to a fluidized bed gasification system. Background Technology

[0002] Fluidized bed high-temperature (1000℃) pressurized (2-65 barg) bubbling gasification is a process in which solid fuels (such as biomass or coal) undergo a gasification reaction with a gasifying agent (usually oxygen, steam, or carbon dioxide) under high temperature and high pressure conditions. In the fluidized bed, the fuel is broken down to a specific particle size and air is introduced through air distribution plates arranged at the bottom of the furnace. As the air velocity increases, the fuel particles are "lifted" by the airflow, and the entire fuel bed exhibits fluid-like boiling characteristics, forming bubbling fluidized bed combustion or boiling combustion.

[0003] Its raw materials include physical materials, coal, and gasifiable waste, which are gasified at high temperature and pressure in a fluidized bed to generate combustible gases (such as syngas), which can be used for power generation, heating, or as chemical raw materials.

[0004] Traditional fluidized bed reactors, due to the fluidization requirements, introduce excessive steam through the distribution plate and central tube. This leads to increased H2 and CO2 content, decreased CO content, higher syngas dew point, increased wastewater and circulating water volume, increased steam consumption, and decreased overall economic efficiency. Consequently, it results in serious operational problems such as higher gasifier surface temperature, increased heat loss, and severe dew point corrosion in the economizer section of the waste heat boiler. Furthermore, the low CO content caused by traditional steam fluidization results in a significant amount of valuable carbon being converted into ineffective CO2 and released into the atmosphere, leading to substantial waste and low carbon utilization. Utility Model Content

[0005] The purpose of this invention is to solve the problems of low CO content, high H2 and CO2 content, and large wastewater and circulating water volume in existing fluidized bed gasification systems that use steam fluidization, and to provide a fluidized bed gasification system. The fluidized bed gasification system of this invention has at least one of the following advantages: (1) high CO content; (2) low H2 and CO2 content; (3) small wastewater and circulating water volume; (4) low syngas dew point; (5) low heat loss from the gasifier.

[0006] This utility model solves the above-mentioned technical problems through the following technical solutions:

[0007] This utility model provides a fluidized bed gasification system, which includes: a fluidized bed gasifier and a cooling device, a first dust removal device, and a cooling and washing device connected in series at the syngas outlet of the fluidized bed gasifier; the cooling device is used to cool the syngas flowing out of the syngas outlet of the fluidized bed gasifier, the first dust removal device is used to collect fly ash in the syngas flowing out of the cooling device, and the cooling and washing device is used to wash the fly ash in the syngas flowing out of the first dust removal device.

[0008] A ash cooling device is connected to the ash discharge port of the fluidized bed gasifier and is used to cool the ash discharged from the ash discharge port by means of a cooling medium.

[0009] The circulating pipeline combines a portion of the syngas flowing out of the cooling device, a portion of the syngas flowing out of the first dust removal device, and a portion of the syngas flowing out of the cooling and washing device, and sends it as circulating gas to the gasifying agent inlet, the fluidizing gas inlet, and the cooling medium inlet of the fluidized bed gasifier.

[0010] The cooling medium outlet of the ash cooling device is connected to the feed inlet of the fluidized bed gasifier. A portion of the circulating gas is used as a cooling medium to exchange heat with the ash and slag in the ash cooling device and then enters the fluidized bed gasifier as raw material.

[0011] This invention returns a portion of the syngas to the fluidized bed gasifier as recirculated gas, replacing part or all of the fluidizing gas and some of the gasifying agent. This reduces the amount of water vapor entering the fluidized bed gasifier, increases the CO and effective gas content in the syngas, and reduces the CO2 and H2 content, resulting in high carbon utilization. Furthermore, it lowers the dew point of the syngas, reduces heat loss in the gasifier, and decreases wastewater and recirculated water volume. Additionally, the recirculated gas is used to cool the ash and slag, reducing water vapor, and can also recover heat from the ash and slag before entering the gasifier, thereby improving the thermal efficiency of the gasification process.

[0012] In this invention, the cooling device is preferably a waste heat boiler.

[0013] In this invention, a second dust removal device is preferably provided between the outlet of the cooling device and the circulation pipeline. The second dust removal device is used to collect fly ash in the syngas flowing out of the cooling device, thereby reducing the impact of fly ash in the syngas on the circulator in the circulation pipeline.

[0014] The second dust removal device is preferably a cyclone separator.

[0015] In this invention, the first dust removal device is preferably a cyclone separator.

[0016] In this invention, the cooling and washing device is preferably a water washing tower.

[0017] In this invention, preferably, the ash cooling device includes a housing and a gas distributor disposed within the housing. The top of the housing has a ash inlet and a cooling medium outlet, while the bottom of the housing has a ash outlet and a cooling medium inlet. The gas distributor is positioned around the ash outlet at the bottom of the housing, and the holes on the gas distributor communicate with the cooling medium inlet. This allows the ash to flow downwards along the housing, while the circulating gas, acting as the cooling medium, flows upwards to exchange heat with the ash, thereby cooling it.

[0018] More preferably, the bottom of the housing is inverted V-shaped, the gas distributor is also inverted V-shaped and is set at the bottom of the inverted V-shaped housing, and the cooling medium inlet is set at the bottom of the inverted V-shaped housing.

[0019] In this invention, the cooling medium outlet of the cold ash device is preferably connected to the top of the dilute phase zone of the fluidized bed gasifier. This zone has less ash and slag, which can reduce or avoid ash and slag clogging the pipes and affecting the utilization of circulating gas, thus making the utilization rate of circulating gas higher. The top of the dilute phase zone usually refers to the upper part of the fluidized bed gasifier near the top.

[0020] In this invention, the cooling medium outlet of the cold ash device is preferably connected to the fluidizing gas inlet. After the circulating gas exchanges heat with the ash slag, its temperature rises, and as a fluidizing gas, it can improve the gasification effect.

[0021] In this invention, the cooling medium outlet of the cold ash device can also be connected in parallel to the top of the dilute phase zone of the fluidized bed gasifier and the fluidizing gas inlet.

[0022] In this invention, a third dust removal device is preferably also provided on the connecting pipeline between the cold ash device and the fluidized bed gasifier. The third dust removal device is used to collect fly ash in the circulating gas after heat exchange.

[0023] The third dust removal device is preferably a cyclone separator.

[0024] In this invention, the circulation pipeline is preferably also connected to the first combustion aid inlet of the fluidized bed gasifier, so as to introduce the circulating gas into the fluidized bed gasifier for oxygen supplementation and combustion assistance. The first combustion aid inlet is located in the lower middle part of the dilute phase zone of the fluidized bed gasifier.

[0025] In this invention, the circulation pipeline is preferably also connected to the second combustion aid inlet of the fluidized bed gasifier, so that the circulating gas is introduced into the fluidized bed gasifier for oxygen supplementation and combustion assistance. The second combustion aid inlet is located in the lower middle part of the dense phase zone of the fluidized bed gasifier.

[0026] In this invention, the first and second combustion aid inlets of the fluidized bed gasifier are conventional in the art, and are usually located above the secondary air nozzle, with the first combustion aid inlet being higher than the second combustion aid inlet.

[0027] In this invention, the circulating pipeline preferably includes a main pipeline, three circulating gas outlet branches, and at least three circulating gas inlet branches. The outlets of the cooling device, the first dust removal device, and the cooling and washing device are all connected in parallel to one of the circulating gas outlet branches. All the circulating gas outlet branches are connected in parallel to one end of the main pipeline. The gasifying agent inlet, the fluidizing gas inlet, and the cooling medium outlet of the cold ash device of the fluidized bed gasifier are all connected to a circulating gas inlet branch. All the circulating gas inlet branches are connected in parallel to the other end of the main pipeline. This allows a portion of the syngas flowing out from the cooling device, the first dust removal device, and the cooling and washing device to converge at the main pipeline via the circulating gas outlet branches, mix, and then flow to the gasifying agent inlet, the fluidizing gas inlet, and the cooling medium inlet of the cold ash device, respectively.

[0028] Preferably, a circulation machine is installed on the main pipeline.

[0029] Preferably, the circulating gas feed branch has five branches, which are respectively the first combustion aid inlet, the second combustion aid inlet, the gasifying agent inlet, the fluidizing gas inlet, and the cooling medium inlet of the cold ash device of the fluidized bed gasifier.

[0030] Preferably, the circulating gas feed branch is also provided with an air inlet for introducing gasifying agent, fluidizing gas, combustion aid or inert gas, etc.

[0031] In this invention, the fluidized bed gasifier is preferably a bubbling fluidized bed gasifier. The fluidized bed gasifier is provided with a central tube and a distribution plate. The gasifying agent inlet is provided on the central tube, and the fluidizing gas inlet is provided on the distribution plate.

[0032] The fluidized bed gasifier of this invention can be a conventional biomass bubbling fluidized bed gasifier in the field. The combustion chamber of the fluidized bed gasifier is formed sequentially from the syngas outlet to the ash discharge port as a dilute phase zone, a transition zone, and a dense phase zone. The dilute phase zone is located in the upper part of the circulating fluidized bed combustion chamber, usually the area above the secondary air nozzle. The dense phase zone is located in the lower part of the circulating fluidized bed combustion chamber and is the area with the highest concentration of solid particles in the gas-solid two-phase flow. The transition zone is the intermediate area connecting the dense phase zone and the dilute phase zone.

[0033] When the above-described fluidized bed gasification of this utility model is used for gasification reaction, the gasification method specifically includes the following steps:

[0034] The solid raw material, gasifying agent, and fluidizing gas are fed into the fluidized bed gasifier for gasification reaction to obtain syngas. The circulation pipeline combines a portion of the syngas flowing out of the cooling device, a portion of the syngas flowing out of the first dust removal device, and a portion of the syngas flowing out of the cooling and scrubbing device, and sends it as circulating gas to the gasifying agent inlet, the fluidizing gas inlet, and the cooling medium inlet of the cooling ash device of the fluidized bed gasifier. The circulating gas entering the cooling ash device exchanges heat with the ash and slag in the cooling ash device before entering the fluidized bed gasifier. The syngas that passes through the cooling device, the first dust removal device, and the cooling and scrubbing device in sequence forms clean syngas.

[0035] In this invention, the volume ratio of the total circulating gas to the net syngas in the circulation pipeline is preferably 20-50%. If this ratio is too high, energy consumption increases and the economy suffers; if it is too low, it cannot meet the requirements of the gasifier. The preferred range is 20-50%.

[0036] In this invention, the gasifying agent in the central tube of the fluidized bed gasifier can be conventional in the art, typically a mixture of oxygen and water vapor, a mixture of inert gas and oxygen, or a mixture of inert gas, oxygen, and water vapor.

[0037] In this invention, the temperature of the gasification reaction is determined according to the actual reaction raw materials, for example, 800~1000℃.

[0038] In this invention, the raw material may be biomass and / or coal.

[0039] In this invention, preferably, the volume of circulating gas diverted from the cooling device accounts for 0-100% of the total volume of circulating gas in the circulation pipeline, the volume of circulating gas diverted from the first dust removal device accounts for 0-100% of the total volume of circulating gas in the circulation pipeline, and the volume of circulating gas diverted from the cooling and washing device accounts for 0-100% of the total volume of circulating gas in the circulation pipeline, and the sum of the volumes of the three accounts for 100% of the total volume of circulating gas.

[0040] More preferably, the volume of the circulating gas diverted from the cooling device accounts for 0-75% of the total circulating gas volume in the circulation pipeline and is not zero, and the volume of the circulating gas diverted from the first dust removal device accounts for 25-100% of the total circulating gas volume in the circulation pipeline and is not 100%, and the sum of the two volumes accounts for 100% of the total circulating gas volume; or,

[0041] The volume of circulating gas diverted from the cooling device accounts for 0-75% of the total circulating gas volume in the circulation pipeline, and is not zero; the volume of circulating gas diverted from the cooling and washing device accounts for 25-100% of the total circulating gas volume in the circulation pipeline, and is not 100%; the sum of the two volumes accounts for 100% of the total circulating gas volume; or,

[0042] The volume of circulating gas diverted from the cooling device accounts for 10-15% of the total circulating gas volume in the circulation pipeline, the volume of circulating gas diverted from the first dust removal device accounts for 50-65% of the total circulating gas volume in the circulation pipeline, and the volume of circulating gas diverted from the cooling and washing device accounts for 25-35% of the total circulating gas volume in the circulation pipeline. The sum of the volumes of the three accounts for 100% of the total circulating gas volume.

[0043] Even more preferably, the volume ratio of the circulating gas diverted from the cooling device, the circulating gas diverted from the first dust removal device, and the circulating gas diverted from the cooling and washing device is 1:6:3. Since the three streams of circulating gas originate from different temperatures, mixing them according to this ratio ensures that the gas entering the gasifier better meets the gasifier's intake requirements.

[0044] In this invention, the volume of circulating gas entering the fluidizing gas inlet preferably accounts for 35-100% of the total volume of circulating gas in the circulating pipeline.

[0045] In this invention, the volume of circulating gas entering the gasifying agent inlet preferably accounts for 0-40% of the total volume of circulating gas in the circulating pipeline, for example, 20%.

[0046] In this invention, the volume of circulating gas entering the cooling medium inlet preferably accounts for 0-40% of the total volume of circulating gas in the circulating pipeline, for example, 20%.

[0047] More preferably, the volume ratio of the circulating gas entering the fluidizing gas inlet, the gasifying agent inlet, and the cooling medium inlet is 6:2:2.

[0048] In this invention, when the circulation pipeline is also connected to the first combustion aid inlet of the fluidized bed gasifier, the circulating gas is introduced into the fluidized bed gasifier for oxygen supplementation and combustion assistance. The first combustion aid inlet is located in the lower middle part of the dilute phase zone of the fluidized bed gasifier. The volume of the circulating gas entering the first combustion aid inlet preferably accounts for 0 to 10% of the total volume of the circulating gas in the circulation pipeline.

[0049] In this invention, when the circulation pipeline is also connected to the second combustion aid inlet of the fluidized bed gasifier, the circulation gas is introduced into the fluidized bed gasifier for oxygen supplementation and combustion assistance. The second combustion aid inlet is located in the lower middle part of the dense phase zone of the fluidized bed gasifier. The volume of the circulation gas entering the second combustion aid inlet preferably accounts for 0 to 10% of the total volume of the circulation gas in the circulation pipeline.

[0050] The positive and progressive effects of this utility model are as follows:

[0051] The gasification reaction based on the fluidized bed gasification system of this invention results in a net syngas with high CO content, low H2 and CO2 content, small wastewater and circulating water volume, low syngas dew point, and low heat loss from the gasifier.

[0052] In one specific embodiment, the effective gas content in the obtained syngas increased from 65.3% to 70.3%, the CO content increased from 25.1% to 55.2%, and the C utilization rate increased from 45.2% to 75.0%; the H2 content decreased from 40.2% to 15.1%, and the CO2 content decreased from 29.7% to 25.1%, reducing the emission of ineffective CO2, saving valuable biomass resources, reducing the dew point of the syngas from 151°C to 72°C, reducing the heat loss of the gasifier by 25.6%, and reducing the wastewater and circulating water volume by 50.6%. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the structure of the fluidized bed gasification system described in the embodiment of this utility model.

[0054] Explanation of reference numerals in the attached figures:

[0055] 1-Fluidized bed gasifier, 2-Cooling device, 3-First dust removal device, 4-Cooling and washing device, 5-Cold ash device, 6-Circulation pipeline, 7-Second dust removal device, 8-Third dust removal device, 9-Circulating machine;

[0056] 101-Gasifying agent inlet, 102-Liquidizing gas inlet, 103-First combustion aid inlet, 104-Second combustion aid inlet, 105-Gasified solids feed inlet;

[0057] 501 - Cooling medium inlet, 502 - Cooling medium outlet;

[0058] 601 - Main pipeline, 602 - Circulating gas discharge branch, 603 - Circulating gas inlet branch, 604 - Air inlet. Detailed Implementation

[0059] The present invention is further illustrated below by way of embodiments, but these embodiments do not limit the present invention to the scope of the embodiments described. Experimental methods in the following embodiments that do not specify specific conditions are performed according to conventional methods and conditions, or as selected according to the product instructions.

[0060] Example 1

[0061] This embodiment discloses a fluidized bed gasification system, which includes: a fluidized bed gasifier 1 and a cooling device 2, a first dust removal device 3, and a cooling and washing device 4 connected in series at the syngas outlet of the fluidized bed gasifier 1; the cooling device 2 is used to cool the syngas flowing out of the syngas outlet of the fluidized bed gasifier 1, the first dust removal device 3 is used to collect fly ash in the syngas flowing out of the cooling device 2, and the cooling and washing device 4 is used to wash the fly ash in the syngas flowing out of the first dust removal device 3.

[0062] The ash cooling device 5 is connected to the ash discharge port of the fluidized bed gasifier 1. The ash cooling device 5 is used to cool the ash discharged from the ash discharge port by means of a cooling medium.

[0063] The circulation pipeline 6 feeds a portion of the syngas flowing out of the cooling device 2, a portion of the syngas flowing out of the first dust removal device 3, and a portion of the syngas flowing out of the cooling and washing device 4 as circulating gas into the gasifying agent inlet 101, the fluidizing gas inlet 102, and the cooling medium inlet 501 of the cold ash device 5 in the fluidized bed gasifier 1. The cooling medium outlet 502 of the cold ash device is connected to the feed inlet of the fluidized bed gasifier 1, and a portion of the circulating gas is used as a cooling medium to exchange heat with the ash and slag in the cold ash device 5 before entering the fluidized bed gasifier 1.

[0064] In this embodiment, the fluidized bed gasifier 1 is a bubbling fluidized bed gasifier. The fluidized bed gasifier 1 is equipped with a central pipe and a distribution plate. A gasifying agent inlet 101 is installed on the central pipe, and a fluidizing gas inlet 102 is installed on the distribution plate. The combustion chamber of the fluidized bed gasifier 1 is sequentially formed from the syngas outlet to the slag discharge port into a dilute phase zone, a transition zone, and a dense phase zone. The dilute phase zone is located in the upper part of the fluidized bed, above the secondary air nozzle. The dense phase zone is located in the lower part of the circulating fluidized bed combustion chamber and is the region with the highest concentration of solid particles in the gas-solid two-phase flow. The transition zone is the intermediate region connecting the dense phase zone and the dilute phase zone.

[0065] In this embodiment, the fluidized bed gasifier 1 is also provided with a first combustion aid inlet 103 and a second combustion aid inlet 104. The first combustion aid inlet 103 is located in the lower middle part of the dilute phase zone of the fluidized bed gasifier 1, and the second combustion aid inlet 104 is located in the lower middle part of the dense phase zone of the fluidized bed gasifier 1. Both are used to introduce circulating gas into the fluidized bed gasifier 1 for oxygen supplementation and combustion assistance.

[0066] In this embodiment, the cooling device 2 is a waste heat boiler, and a second dust removal device 7 is also provided between the outlet of the cooling device 2 and the circulation pipeline 6. The second dust removal device 7 is used to collect fly ash in the synthesis gas flowing out of the cooling device 2. The first dust removal device 3 and the second dust removal device 7 are both cyclone separators.

[0067] In this embodiment, the cooling and washing device 4 is a water washing tower.

[0068] In this embodiment, the cold ash device 5 includes a box and a gas distributor installed inside the box. The top of the box is provided with a slag inlet and a cooling medium outlet 502, and the bottom of the box is provided with a slag outlet. The gas distributor is arranged around the slag outlet at the bottom of the box and is provided with a cooling medium inlet 501. The bottom of the box is inverted V-shaped, and the gas distributor is also inverted V-shaped and is arranged in conjunction with the bottom of the inverted V-shaped box.

[0069] In this embodiment, the cooling medium outlet 502 of the cooling ash device 5 is connected to the top of the dilute phase zone of the fluidized bed gasifier 1.

[0070] In this embodiment, a third dust removal device 8 is also provided on the connecting pipeline of the cold ash device 5 and the fluidized bed gasifier 1. The third dust removal device 8 is used to collect fly ash in the circulating gas after heat exchange. The third dust removal device 8 is a cyclone separator.

[0071] In this embodiment, the circulation pipeline 6 includes a main pipeline 601, three circulating gas outlet branches 602, and five circulating gas inlet branches 603. The outlets of the cooling device 2, the first dust removal device 3, and the cooling and washing device 4 are each connected in parallel to a circulating gas outlet branch 602. All circulating gas outlet branches 602 are connected in parallel to one end of the main pipeline 601. The pipeline includes a first combustion aid inlet 103, a second combustion aid inlet 104, a gasifying agent inlet 101, a fluidizing gas inlet 102, and a cooling medium inlet 501. Each of the above is connected to a circulating gas feed branch 603. All the circulating gas feed branches 603 are connected in parallel to the other end of the main pipeline 601, so that part of the synthesis gas flowing out of the cooling device 2, the first dust removal device 3 and the cooling washing device 4 is gathered in the main pipeline 601 through the circulating gas discharge branch 602 and mixed. Then it flows to the gasifying agent inlet 101, the fluidizing gas inlet 102, the first combustion aid inlet 103, the second combustion aid inlet 104 and the cooling medium inlet 501 of the cold ash device of the fluidized bed gasifier 1 respectively.

[0072] In this embodiment, a circulation machine 9 is also installed on the main pipeline 601.

[0073] In this embodiment, the circulating gas feed branch 603 is also provided with an air inlet 604 for introducing gasifying agent, fluidizing gas or combustion aid.

[0074] Example 2

[0075] This embodiment discloses a fluidized bed gasification method, which uses the fluidized bed gasification system described in Example 1. The gasification method includes the following steps:

[0076] The gasified solid raw materials, gasifying agent, fluidizing gas, and combustion aid are fed into the fluidized bed gasifier 1 through the gasified solid feed inlet 105 and the air inlets 604 on each circulating gas feed branch 603 for gasification reaction. Part of the generated syngas is processed sequentially through the cooling device 2, the first dust removal device 3, and the cooling and washing device 4 to obtain clean syngas. The other part is used as circulating gas and flows through the circulating pipeline into the first combustion aid inlet 103, the second combustion aid inlet 104, the gasifying agent inlet 101, the fluidizing gas inlet 102, and the cooling medium inlet 501 of the cold ash device 5, and then enters the fluidized bed gasifier 1. The circulating gas in the cold ash device 5 is used as a cooling medium to exchange heat with the ash and slag in the cold ash device 5 before entering the fluidized bed gasifier 1 from the top of the dilute phase zone.

[0077] In this embodiment, the solid feedstock for gasification is coal, and the characteristics of coal are shown in Table 1. The gasifying agent, fluidizing gas, and combustion aid are all mixtures of oxygen and water vapor (oxygen volume content is 40%), the gasification temperature is 800~1000℃, and the pressure is atmospheric pressure to 80 barg.

[0078] Table 1 Characteristics of Coal

[0079]

[0080] The amount of coal and oxygen in this embodiment are shown in Table 2. The amount of oxygen refers to the total amount of oxygen added to the entire gasifier. The amount of oxygen entering the gasifying agent inlet 101, the fluidizing gas inlet 102, the first combustion aid inlet 103, and the second combustion aid inlet 104 is distributed in a ratio of 6:1:1.5:1.5.

[0081] In this embodiment, the circulating gas diverted from the cooling device 2 accounts for 10% of the total circulating gas volume in the circulation pipeline, the circulating gas diverted from the first dust removal device 3 accounts for 60% of the total circulating gas volume in the circulation pipeline, and the circulating gas diverted from the cooling washing device 4 accounts for 30% of the total circulating gas volume in the circulation pipeline; the circulating gas entering the fluidizing gas inlet 102, the gasifying agent inlet 101, and the cooling medium inlet 501 is distributed in a volume ratio of 6:2:2, and the circulating gas entering the first combustion aid inlet 103 and the second combustion aid inlet 104 is both 0.

[0082] In this embodiment, 50% of the water vapor is replaced by recirculated gas, and the volume ratio of total recirculated gas to net syngas in the recirculation pipeline is 20%.

[0083] In this embodiment, the amount of syngas, effective gas, CO, H2, CO2 and other component contents obtained from the gasification reaction refer to the content of each component in the syngas at the syngas outlet of the fluidized bed gasifier. The dew point refers to the dew point of the syngas at the syngas outlet of the fluidized bed gasifier, as detailed in Table 2.

[0084] Example 3

[0085] The fluidized bed gasification method in this embodiment also uses the fluidized bed gasification system described in Example 1. The gasification method is basically the same as that in Example 2, except that: in this embodiment, circulating gas is used to replace all water vapor, and the volume ratio of total circulating gas to net syngas in the circulating pipeline in this embodiment is 40%.

[0086] The specific amounts of syngas, effective gas, CO, H2, CO2, other component contents, and syngas dew point obtained from the gasification reaction in this embodiment are shown in Table 2.

[0087] Comparative Example 1

[0088] The fluidized bed gasification system in this comparative example differs from that in Example 1 in that it lacks the cold ash device 5 and the circulation pipeline 6, while the structure of other equipment is the same as that in Example 1.

[0089] The gasification method of this comparative example includes the following steps: gasification solid raw materials, gasification agent and fluidizing gas are fed into fluidized bed gasifier 1 for gasification reaction, and combustion aid is added through the first combustion aid inlet and the second combustion aid inlet. A portion of the generated syngas is processed sequentially through cooling device 2, first dust removal device 3 and cooling and washing device 4 to obtain clean syngas.

[0090] The gasified solid feedstock, gasifying agent, fluidizing gas, and combustion aid are the same as in Example 2.

[0091] The specific amounts of syngas, effective gas, CO, H2, CO2, other component contents, and syngas dew point obtained from the comparative gasification reaction are shown in Table 2.

[0092] Table 2

[0093]

[0094] As can be seen from Table 2, the syngas volume, effective gas volume, and CO content of Examples 2 and 3 are all higher than those of Comparative Example 1, while the contents of H2, CO2, and other components are all lower than those of Comparative Example 1, and the dew point of the syngas is also lower than that of Comparative Example 1.

Claims

1. A fluidized bed gasification system, characterized in that, It includes: fluidized bed A gasifier and a cooling device, a first dust removal device, and a cooling and washing device connected in series at the syngas outlet of the fluidized bed gasifier. The cooling device is used to cool the syngas flowing out of the syngas outlet of the fluidized bed gasifier, the first dust removal device is used to collect fly ash in the syngas flowing out of the cooling device, and the cooling and washing device is used to wash the fly ash in the syngas flowing out of the first dust removal device. A ash cooling device is connected to the ash discharge port of the fluidized bed gasifier and is used to cool the ash discharged from the ash discharge port by means of a cooling medium. The circulating pipeline combines a portion of the syngas flowing out of the cooling device, a portion of the syngas flowing out of the first dust removal device, and a portion of the syngas flowing out of the cooling and washing device, and sends it as circulating gas to the gasifying agent inlet, the fluidizing gas inlet, and the cooling medium inlet of the fluidized bed gasifier. The cooling medium outlet of the ash cooling device is connected to the feed inlet of the fluidized bed gasifier. A portion of the circulating gas is used as a cooling medium to exchange heat with the ash and slag in the ash cooling device before being introduced into the fluidized bed gasifier.

2. The fluidized bed gasification system as described in claim 1, characterized in that, The cooling device is a waste heat boiler; And / or, a second dust removal device is also provided between the outlet of the cooling device and the circulation pipeline, the second dust removal device being used to collect fly ash in the syngas flowing out of the cooling device; And / or, the first dust removal device is a cyclone separator; And / or, the cooling and washing device is a water washing tower.

3. The fluidized bed gasification system as described in claim 1, characterized in that, The cold ash device includes a box and a gas distributor disposed inside the box. The top of the box is provided with a slag inlet and a cooling medium outlet, and the bottom of the box is provided with a slag outlet and a cooling medium inlet. The gas distributor is disposed around the slag outlet at the bottom of the box, and the hole on the gas distributor is connected to the cooling medium inlet.

4. The fluidized bed gasification system as described in claim 1, characterized in that, The cooling medium outlet of the cold ash device is connected to the top of the dilute phase zone of the fluidized bed gasifier; And / or, the cooling medium outlet of the cold ash device is connected to the fluidizing gas inlet.

5. The fluidized bed gasification system as described in claim 1, characterized in that, A third dust removal device is also installed on the connecting pipeline between the cold ash device and the fluidized bed gasifier. The third dust removal device is used to collect fly ash in the circulating gas after heat exchange.

6. The fluidized bed gasification system as described in claim 1, characterized in that, The circulation pipeline is also connected to the first combustion aid inlet of the fluidized bed gasifier, and the circulating gas is introduced into the fluidized bed gasifier for oxygen supplementation and combustion assistance. The first combustion aid inlet is located in the lower middle part of the dilute phase zone of the fluidized bed gasifier. And / or, the circulation pipeline is also connected to the second combustion aid inlet of the fluidized bed gasifier, so as to introduce the circulating gas into the fluidized bed gasifier for oxygen supplementation and combustion assistance. The second combustion aid inlet is located in the lower middle part of the dense phase zone of the fluidized bed gasifier.

7. The fluidized bed gasification system as described in claim 1, characterized in that, The circulation pipeline includes a main pipeline, three circulating gas outlet branches, and at least three circulating gas inlet branches. The outlets of the cooling device, the first dust removal device, and the cooling and scrubbing device are all connected in parallel to one of the circulating gas outlet branches. All the circulating gas outlet branches are connected in parallel to one end of the main pipeline. The gasifying agent inlet, the fluidizing gas inlet, and the cooling medium outlet of the cold ash device of the fluidized bed gasifier are all connected to one of the circulating gas inlet branches. All the circulating gas inlet branches are connected in parallel to the other end of the main pipeline. This allows a portion of the syngas flowing out from the cooling device, the first dust removal device, and the cooling and scrubbing device to converge at the main pipeline via the circulating gas outlet branches, mix, and then flow to the gasifying agent inlet, the fluidizing gas inlet, and the cooling medium inlet of the cold ash device, respectively.

8. The fluidized bed gasification system as described in claim 7, characterized in that, A circulation machine is installed on the main pipeline; And / or, the circulating gas feed branch has five branches, which are respectively the first combustion aid inlet, the second combustion aid inlet, the gasifying agent inlet, the fluidizing gas inlet, and the cooling medium inlet of the cold ash device of the fluidized bed gasifier.

9. The fluidized bed gasification system as described in claim 7, characterized in that, The circulating gas feed branch is also equipped with an air inlet for introducing gasifying agent, fluidizing gas or combustion aid.

10. The fluidized bed gasification system as described in claim 1, characterized in that, The fluidized bed gasifier is a bubbling fluidized bed gasifier. The fluidized bed gasifier is equipped with a central tube and a distribution plate. The gasifying agent inlet is provided on the central tube, and the fluidizing gas inlet is provided on the distribution plate.

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