CN110205164B - Circulating fluidized bed gasification device and circulating fluidized bed gasification method - Google Patents

Abstract

A circulating fluidized bed gasification device, comprising a gasifier, a gas-solid separator and a feeder, wherein the gasifier is communicated with the gas-solid separator, the gas-solid separator is communicated with the feeder, and the feeder is communicated with the gasifier The gasification furnace is connected with the furnace, and the gasification furnace is provided with a gasification agent inlet, a feeding port, a material return port and a gasification product outlet, wherein the gasification agent inlet includes a primary gasification agent inlet and a secondary gasification agent inlet , and the primary gasification agent inlet is located at a first position, and the secondary gasification agent inlet is located at a second position different from the first position. The invention also provides a circulating fluidized bed gasification method. According to the circulating fluidized bed gasification device and the circulating fluidized bed gasification method of the present invention, the problem of coking at the bottom of the furnace can be alleviated.

Description

Circulating fluidized bed gasification device and circulating fluidized bed gasification method

technical field

The present invention relates to the technical field of fuel gasification, in particular, to a circulating fluidized bed gasification device and a circulating fluidized bed gasification method, especially a circulating fluidized bed oxygen-enriched gasification device and a circulating fluidized bed oxygen-enriched gasification method .

Background technique

Coal gasification is one of the important ways for the clean utilization of coal. It is mainly used to convert coal into gaseous clean energy such as CO, _H2 and _CH4 . It is currently widely used in metallurgy, synthesis and other fields or for combined cycle power generation and as fuel gas etc.

According to the state of solid movement in the system, coal gasification technology can be divided into fixed bed gasification, fluidized bed gasification and entrained bed gasification. Among them, the fluidized bed has the advantages of low raw material cost, less environmental pollution, and high gasification efficiency, while the circulating fluidized bed has the advantages of mild reaction conditions, high circulation rate, uniform furnace temperature distribution, sufficient gas-solid contact, and raw materials require a wide range of particle sizes and other advantages, and has been widely used.

According to the type of gasification agent, circulating fluidized bed gasification technology can be divided into air gasification, oxygen-enriched gasification and pure oxygen gasification. Among them, oxygen-enriched gasification is widely used in coal production of high calorific value industrial gas and synthesis gas production and other fields. In the conventional CFB oxygen-enriched gasification process, the oxygen-enriched air is used as a gasification agent to enter the gasification system from the air distribution device at the bottom of the gasifier furnace, and the raw pulverized coal undergoes combustion, gasification and other reactions under the action of the gasification agent. The generated gas and incompletely reacted carbon-containing solid particles are discharged from the upper part of the furnace and enter the gas-solid separation device for gas-solid separation. Most of the carbon-containing solid particles are separated and returned to the gasifier by the return device, while the rest The dust gas enters the subsequent dust removal and cooling system.

In a conventional circulating fluidized bed gasifier, all the gasification agents enter the gasifier from the bottom of the furnace. Influenced by the gas-solid flow and reaction distribution characteristics in the furnace, the bottom of the gasifier is a high temperature zone, and the main solid material is ash High-volume large-particle semi-coke; along the height direction of the furnace, the furnace temperature gradually decreases, and the main solid material in the upper part of the furnace is small-particle semi-coke with low ash content. For the relationship between temperature, particle ash concentration and furnace height in a conventional circulating fluidized bed furnace, please refer to Figure 1. From the point of view of the operation stability of the gasifier, the high temperature and high ash content at the bottom of the furnace make the bottom of the furnace prone to coking; in addition, due to the influence of oxygen concentration on the combustion reaction rate, the oxygen-enriched oxidant is more likely to cause local damage at the bottom of the furnace. High temperature coking. From the perspective of gasification performance optimization, the reduction of the temperature in the upper part of the furnace limits the gasification reaction between the small particle semi-coke with high carbon content and the CO ₂ and water vapor in the gas phase, which affects the gasification index of the system. promote.

In addition, in order to ensure a large circulation flux, the amount of gasification introduced from the bottom of the furnace must meet the requirements of the fluidization velocity at the bottom of the furnace, and some larger particles are also carried to the upper part of the furnace. The residence time is short and the reaction is insufficient. In addition, the position of the material return port in the conventional circulating fluidized bed gasifier is relatively low, and part of the material returned to the furnace will enter the lower part of the furnace and be discharged from the bottom slag discharge pipe together with the large-sized solid particles, and the residence time is short, resulting in circulating fluidization. Bed gasification bottom slag has high carbon content.

To sum up, the following technical defects mainly exist in the conventional CFB oxygen-enriched gasification process:

(1) The oxygen-to-carbon ratio at the bottom of the furnace is high, the heat release of combustion is large, and the temperature is high, and the bottom of the furnace is large particle material with high ash content, which is easy to coke at high temperature;

(2) Along the height direction of the furnace, the temperature of the furnace shows a downward trend. Although the carbon concentration in the upper part of the furnace is high, the gasification reaction is limited due to the low temperature, which affects the oxygen-enriched gasification efficiency of the circulating fluidized bed;

(3) The carbon content of the system ash is high, the main reasons include: on the one hand, the temperature distribution does not match the gasification reaction, the gasification efficiency is low, the solid particle reaction is incomplete, and the formed ash has high carbon content; , the fluidization speed at the bottom of the furnace is high, the residence time of solid particles in the oxidation zone with sufficient oxidant is short, and the reaction is insufficient, resulting in high carbon content in the ash; Part of the high carbon-containing solid particles are discharged together with the bottom slag, resulting in a high carbon content in the gasified bottom slag.

SUMMARY OF THE INVENTION

The purpose of the present invention is to at least partially overcome the defects of the prior art, and to provide a new circulating fluidized bed gasification device and a circulating fluidized bed gasification method.

Another object of the present invention is to provide a circulating fluidized bed gasification device and a circulating fluidized bed gasification method, which can alleviate the problem of coking at the bottom of the furnace.

Another object of the present invention is to provide a circulating fluidized bed gasification device and a circulating fluidized bed gasification method with high gasification efficiency and carbon conversion rate.

Another object of the present invention is to provide a circulating fluidized bed gasification device and a circulating fluidized bed gasification method, wherein the bottom slag has a low carbon content.

In order to achieve the above-mentioned purpose or one of the purposes, the technical solution of the present invention is as follows:

A circulating fluidized bed gasification device, comprising a gasifier, a gas-solid separator and a feeder, wherein the gasifier is communicated with the gas-solid separator, the gas-solid separator is communicated with the feeder, and the feeder is communicated with the gasifier The gasification furnace is connected with the furnace, and the gasification furnace is provided with a gasification agent inlet, a feeding port, a material return port and a gasification product outlet, wherein the gasification agent inlet includes a primary gasification agent inlet and a secondary gasification agent inlet , and the primary gasification agent inlet is located at a first position, and the secondary gasification agent inlet is located at a second position different from the first position.

According to a preferred embodiment of the present invention, the primary gasification agent inlet is located at the bottom of the gasifier, and the secondary gasification agent inlet is located below the middle of the gasifier.

According to a preferred embodiment of the present invention, the height of the hearth of the gasifier is H, the height of the material return port from the bottom of the hearth is h ₀ , and 0.1H≤h ₀ ≤0.3H.

According to a preferred embodiment of the present invention, the height of the inlet of the secondary gasification agent from the bottom of the furnace is h, and h≤h ₀ .

According to a preferred embodiment of the present invention, the gasification agent inlet includes a plurality of secondary gasification agent inlets, and the plurality of secondary gasification agent inlets are distributed in the same layer, or distributed in multiple layers along the height direction of the gasifier .

According to a preferred embodiment of the present invention, the projections of the secondary gasification agent inlets of different layers on the cross section perpendicular to the height direction of the gasifier are staggered from each other.

According to a preferred embodiment of the present invention, the gasifier includes an oxidation zone, a transition zone and a reduction zone from bottom to top, the diameter of the transition zone and the reduction zone is D, and the diameter of the oxidation zone is D ₁ , and D≤D ₁ .

According to a preferred embodiment of the present invention, the secondary gasification agent inlet is located in the transition zone of the gasifier.

According to a preferred embodiment of the present invention, the gasifier includes a throat with a reduced diameter relative to the body of the gasifier.

According to a preferred embodiment of the present invention, the throat opening is located below the material return opening.

According to another aspect of the present invention, there is provided a circulating fluidized bed gasification method using the circulating fluidized bed gasification device according to any one of the preceding embodiments, the circulating fluidized bed gasification method comprising: :

(1) The fuel enters the gasifier from the feed port, the circulating solid particles containing incompletely reacted carbon enter the gasifier from the return port, the primary gasification agent enters the gasifier from the primary gasification agent inlet, and the fuel The reaction with the return material and the primary gasification agent is mainly based on the combustion reaction, and heat is released;

(2) The secondary gasification agent enters the gasifier from the inlet of the secondary gasification agent, contacts with carbon particles, reacts and releases heat, and at the same time burns part of the generated combustible gas to release heat;

(3) the gasification product carries the incompletely reacted carbonaceous material into the gas-solid separator from the gasification product outlet;

(4) The circulating solid particles separated by the gas-solid separator are returned to the gasifier through the return device, and the gasified substances separated by the gas-solid separator are collected.

According to a preferred embodiment of the present invention, the fluidization velocity at the bottom of the gasifier is controlled at 1.5m/s˜2.5m/s.

According to a preferred embodiment of the present invention, the gasifier forms a bottom-up oxidation zone, a transition zone and a reduction zone during operation, and the temperature of the oxidation zone is controlled not to be higher than 950°C.

According to a preferred embodiment of the present invention, the reaction temperature of the gasifier is between 850°C and 1200°C.

According to a preferred embodiment of the present invention, the primary gasification agent is air or oxygen-enriched air with an oxygen-enriched concentration <40%, or a mixture of air or oxygen-enriched air with an oxygen-enriched concentration <40% and water vapor.

According to a preferred embodiment of the present invention, the secondary gasification agent is oxygen-enriched air with an oxygen-enriched concentration>50% or oxygen, or oxygen-enriched air with an oxygen-enriched concentration>50% or a mixture of oxygen and water vapor.

According to a preferred embodiment of the present invention, the ratio of the amount of oxygen in the secondary gasification agent to the total amount of oxygen in the gasification agent is 10% to 60%.

According to the circulating fluidized bed gasification device and the circulating fluidized bed gasification method of the present invention, the gasification agent is not all entered from the bottom of the furnace, thus providing a good partition of the atmosphere and temperature of the gasifier, and the temperature of the lower oxidation zone It is relatively low (not more than 950°C) to avoid coking at the bottom due to overtemperature; the introduction of the secondary gasification agent forms a local high temperature area, and the temperature of the furnace transition zone and reduction zone is increased due to radiation and fluidization. These regional gasification reactions provide heat, promote the endothermic gasification reaction, and improve the gasification efficiency and carbon conversion rate of the system. 2 is a graph showing the variation of the temperature T in the circulating fluidized bed gasification device with the furnace height H. It can be seen that the temperature T in the circulating fluidized bed gasification device does not decrease with the furnace height H.

At the same time, the circulating fluidized bed gasification device and the circulating fluidized bed gasification method of the present invention realize the reasonable distribution of solid particles in the gasifier: the lower fluidization speed in the oxidation zone makes the large-diameter solids with high ash content The particles stay in the oxidation zone for a long time, which can fully react with the gasification agent, while the small-sized solid particles circulate for many times in the circulation system composed of the gasifier furnace, gas-solid separator and return feeder. Reacts with the gasification agent in the high temperature region. Particles with different particle sizes can fully contact and react with the gasification agent in different regions, improve the gasification efficiency and carbon conversion rate, and reduce the carbon content of the system ash.

The circulating fluidized bed gasification device and the circulating fluidized bed gasification method of the present invention are more suitable for the oxygen-enriched gasification of the circulating fluidized bed.

Description of drawings

Fig. 1 is the relation diagram of temperature (T) in conventional circulating fluidized bed furnace, particle ash concentration (θ) and furnace height (H);

Fig. 2 is the temperature distribution diagram of the circulating fluidized bed gasification device of the present invention;

3 is a schematic diagram of a circulating fluidized bed gasification device according to Embodiment 1 of the present invention;

4 is a schematic diagram of a circulating fluidized bed gasification apparatus according to Embodiment 2 of the present invention; and

5 is a schematic diagram of a circulating fluidized bed gasification device according to Embodiment 3 of the present invention.

Detailed ways

Exemplary embodiments of the present invention are described in detail below with reference to the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements. Furthermore, in the following detailed description, for convenience of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present disclosure. Obviously, however, one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in diagram form in order to simplify the drawings.

According to the general concept of the present invention, a circulating fluidized bed gasification device is provided, which includes a gasifier, a gas-solid separator and a return material. The gasifier is communicated with the gas-solid separator, and the gas-solid separator is connected with the return material. The feeder is communicated with the gasifier, and the gasifier is communicated with the gasifier, and the gasifier is provided with a gasification agent inlet, a feeding port, a material return port and a gasification product outlet, wherein the gasification agent inlet includes a primary gasification A gasification agent inlet and a secondary gasification agent inlet, and the primary gasification agent inlet is located at a first position, and the secondary gasification agent inlet is located at a second position different from the first position.

The gasifier includes an oxidation zone, a transition zone and a reduction zone from the bottom up. The oxidation zone, the transition zone and the reduction zone may have the same cross-sectional area, or their cross-sectional area may be different, for example, the transition zone and the reduction zone The diameter of the region is D, the diameter of the oxidized region is D ₁ , and D≦D ₁ .

Specifically, the primary gasification agent inlet is located at the bottom of the gasifier, and the secondary gasification agent inlet is located below the middle of the gasifier. Advantageously, the secondary gasification agent inlet is located in the transition zone of the gasifier. The gasification agent enters the gasifier in two stages, especially when the oxygen concentration of the first-stage gasification agent is low (for example, air or oxygen-enriched air with an oxygen-enriched concentration <40%), all of the gasification agent and the oxygen-enriched oxidant are passed through the bottom. Compared with the input, the oxygen-carbon ratio in the oxidation zone is reduced, the heat release is reduced, the temperature at the bottom of the furnace is effectively lowered, and the coking of the bottom of the furnace with high ash concentration due to high temperature is avoided.

In addition, after the secondary gasification agent enters the furnace, a local high temperature is formed, and the heat here is carried to the upper part of the furnace with the material and the fluidizing wind, which increases the temperature in the upper part of the furnace, provides heat for the gasification reaction, and promotes the gasification reaction. It can improve the gasification efficiency and carbon conversion rate of the system. This effect is more pronounced especially when the oxygen concentration of the secondary gasification agent is high.

Preferably, the height of the hearth of the gasifier is H, the height of the material returning port from the bottom of the hearth is h ₀ , and 0.1H≤h ₀ ≤0.3H. Limit the height of the return port to avoid the problem of high carbon content in the CFB gasification bottom slag caused by the low position of the return port.

Further, the height of the secondary gasification agent inlet from the bottom of the furnace is h, and h≤h ₀ . When the secondary gasification agent is introduced below the material return port, it will carry the carbon-containing solid material returning to the furnace upward, which increases the concentration of carbon-containing solid particles in the transition zone and the reduction zone, and further improves the gasification efficiency and carbon conversion rate of the system. .

The gasification agent inlet may include a plurality of secondary gasification agent inlets, and the plurality of secondary gasification agent inlets are distributed in the same layer, or distributed in multiple layers along the height direction of the gasifier. The projections of the secondary gasification agent inlets of different layers on the cross-section perpendicular to the height direction of the gasifier are staggered from each other. The staggered secondary gasification agent inlets are beneficial to the uniform distribution of the gasification agent.

According to a preferred embodiment of the present invention, the gasifier includes a throat with a reduced diameter relative to the body of the gasifier. Advantageously, the throat is located below the return opening. The throat is set below the material return port, which strengthens the internal circulation of the oxidation zone at the bottom of the furnace, the middle and upper transition zone and the reduction zone, and realizes a clearer division of atmosphere, particle size and temperature: below the throat, the fluidization speed is low, the temperature is low In the low oxidation zone, large particle materials are circulated here for many times, which reduces the carbon content of the bottom slag; the setting of the throat further reduces the back mixing of the returned material to the lower part of the furnace, and improves the high temperature circulation loop of the small particle material above the throat. The concentration in the fly ash promotes the gasification reaction, improves the gasification efficiency, and reduces the carbon content of the fly ash.

According to another aspect of the present invention, there is provided a circulating fluidized bed gasification method, the circulating fluidized bed gasification method comprising:

(1) The fuel enters the gasifier from the feed port, the circulating solid particles containing incompletely reacted carbon enter the gasifier from the return port, the primary gasification agent enters the gasifier from the primary gasification agent inlet, and the fuel The reaction with the return material and the primary gasification agent is mainly based on the combustion reaction, and heat is released;

(2) The secondary gasification agent enters the gasifier from the inlet of the secondary gasification agent, contacts with carbon particles, reacts and releases heat, and at the same time burns part of the generated combustible gas to release heat;

(3) the gasification product carries the incompletely reacted carbonaceous material into the gas-solid separator from the gasification product outlet;

(4) The circulating solid particles separated by the gas-solid separator are returned to the gasifier through the return device, and the gasified substances separated by the gas-solid separator are collected.

According to a preferred embodiment of the present invention, the fluidization velocity at the bottom of the gasifier is controlled at 1.5m/s˜2.5m/s. The fluidization speed at the bottom of the gasifier is controlled so that the circulating material with larger particles stays in the oxidation zone with sufficient gasification agent for a sufficient time to make the reaction more sufficient.

During the operation of the gasifier, an oxidation zone, a transition zone and a reduction zone are formed from the bottom up, and the temperature of the oxidation zone is controlled not to be higher than 950°C. The reaction temperature of the gasifier is between 850°C and 1200°C. The lower oxidation zone has a lower temperature to avoid coking at the bottom due to overheating.

Preferably, the primary gasification agent is air or oxygen-enriched air with an oxygen-enriched concentration <40%, or a mixture of air or oxygen-enriched air with an oxygen-enriched concentration <40% and water vapor, and the secondary gasification agent is an oxygen-enriched air Oxygen-enriched air with an oxygen concentration > 50% or oxygen, or oxygen-enriched air with an oxygen concentration > 50% or a mixture of oxygen and water vapor. Advantageously, the proportion of oxygen in the secondary gasification agent to the total oxygen content of the gasification agent is 10% to 60%.

According to the circulating fluidized bed gasification device and the circulating fluidized bed gasification method of the present invention, the gasification agent is not all entered from the bottom of the furnace, thus providing a good partition of the atmosphere and temperature of the gasifier, and the temperature of the lower oxidation zone It is relatively low (not more than 950°C) to avoid coking at the bottom due to overtemperature; the introduction of the secondary gasification agent forms a local high temperature area, and the temperature of the furnace transition zone and reduction zone is increased due to radiation and fluidization. These regional gasification reactions provide heat, promote the endothermic gasification reaction, and improve the gasification efficiency and carbon conversion rate of the system. 2 is a graph showing the variation of the temperature T in the circulating fluidized bed gasification device with the furnace height H. It can be seen that the temperature T in the circulating fluidized bed gasification device does not decrease with the furnace height H.

At the same time, the circulating fluidized bed gasification device and the circulating fluidized bed gasification method of the present invention realize the reasonable distribution of solid particles in the gasifier: the lower fluidization speed in the oxidation zone makes the large-diameter solids with high ash content The particles stay in the oxidation zone for a long time, which can fully react with the gasification agent, while the small-sized solid particles circulate for many times in the circulation system composed of the gasifier furnace, gas-solid separator and return feeder. Reacts with the gasification agent in the high temperature region. Particles with different particle sizes can fully contact and react with the gasification agent in different regions, improve the gasification efficiency and carbon conversion rate, and reduce the carbon content of the system ash.

The circulating fluidized bed gasification device and the circulating fluidized bed gasification method of the present invention are more suitable for the oxygen-enriched gasification of the circulating fluidized bed.

Example 1

3 is a schematic diagram of a circulating fluidized bed gasification device according to Embodiment 1 of the present invention. The circulating fluidized bed oxygen-enriched gasification device includes a gasifier 1 , a gas-solid separator 2 , a descending pipe 3 , a returner 4 and a return inclined pipe 5 . The furnace is provided with a primary gasification agent inlet a, a secondary gasification agent inlet (including the first secondary gasification agent inlet b1 and the second secondary gasification agent inlet b2), a feeding port c, a material return port d and a gas Chemical product export e.

The gasifier 1 is divided into a plurality of sections from bottom to top, which are an oxidation zone 1-A, a transition zone 1-B and a reduction zone 1-C in sequence. The diameter of the transition zone and the reduction zone is D, the diameter of the oxidation zone is D ₁ , D and D ₁ are determined by the fluidization velocity of their corresponding regions, D and D ₁ can be equal, wherein, the fluidization velocity of the oxidation zone is 2m/s, The fluidization velocity in the lower part of the transition zone is 3.5 m/s. The feeding port c is located in the transition area 1-B, and the material returning port d is located in the middle and lower part of the transition area 1-B, h ₀ above the air distribution point of the primary gasification agent, and h ₀ =0.15H. In this embodiment, two secondary gasification agent inlets are set, namely b ₁ and b ₂ , which are located on the same level of the furnace. The inlet of the secondary gasification agent is located at h above the air distribution point of the primary gasification agent, and h=0.2H. The inlet direction of the secondary gasification agent is perpendicular to the vertical centerline of the furnace.

The first-stage gasification agent inlet a is located at the bottom of the furnace, and the 0-6mm pulverized coal enters the gasifier 1 from the feeding port c, and the large particles enter the lower oxidation zone 1-A, and the combustion reaction occurs with the first-stage gasification agent. The main reaction and release of heat, the small particles are carried into the upper part of the furnace. The first-stage gasifying agent is a mixture of air and water vapor. Compared with the oxygen-rich gasifying agent being introduced from the bottom of the furnace, the oxygen-carbon ratio in the oxidation zone 1-A and the oxygen concentration in the oxygen-rich air are reduced, and the combustion heat is reduced. , the temperature of the oxidation zone 1-A is reduced, and the temperature of the oxidation zone 1-A is maintained at 900 ℃ ~ 950 ℃, so as to avoid over-temperature coking at the bottom of the furnace.

Keep the fluidizing wind speed at the bottom of the furnace at 2m/s, the larger particles that are not carried to the upper part of the furnace flow in a bubbling state in the oxidation zone 1-A, and react with the primary gasification agent, and the particles stay for a long time, which promotes The sufficient reaction of the solid particles reduces the carbon content of the bottom slag.

Small-sized solid particles and heat move from bottom to top in the furnace. During this process, the gasification agent is gradually consumed, and after passing through the transition zone 1-B, it enters the reduction zone 1-C, which is dominated by gasification reaction. The secondary gasification agent is a mixture of oxygen and water vapor. It enters the gasifier 1 from the secondary gasification agent inlet of the transition zone, contacts with high-concentration carbon particles, and produces an oxidation-based reaction and releases heat, and burns part of the gas. The generated combustible gas forms a local high temperature area, which promotes the gasification reaction near this area. At the same time, the heat at the local high temperature is carried to the upper part of the furnace under the action of thermal radiation and fluidization, which increases the temperature in the upper part of the furnace. Since the gasification reaction is an endothermic reaction, the increase in temperature provides heat for the gasification reaction in the region above it, which promotes the gasification reaction, thereby improving the gasification efficiency and carbon conversion rate of the system.

The generated gas carries the incompletely reacted carbonaceous material and enters the gas-solid separator 2 from the gasification product outlet e, and most of the particles are collected and returned to the furnace through the descending pipe 3, the return material device 4 and the material return inclined pipe 5 in turn, and continue. The cycle participates in the reaction, and a small part escapes from the gas-solid separator 2 into the subsequent cooling and purification system.

Among them, the primary gasification agent is a mixture of air and water vapor, the amount of steam is adjusted according to the requirements of the fluidization speed and temperature at the bottom of the furnace, and the secondary gasification agent is a mixture of oxygen and water vapor. The proportion of oxygen in the secondary gasification agent to the total oxygen in the system is 30%.

Embodiment 2

4 is a schematic diagram of a circulating fluidized bed gasification device according to Embodiment 2 of the present invention. The circulating fluidized bed oxygen-enriched gasification device includes a gasifier 1 , a gas-solid separator 2 , a descending pipe 3 , a returner 4 and a return inclined pipe 5 . The furnace is provided with a primary gasification agent inlet a, a secondary gasification agent inlet (including the first secondary gasification agent inlet b1, the second secondary gasification agent inlet b2, the third secondary gasification agent inlet b3, the second Four-stage gasification agent inlet b4), feed port c, return material port d and gasification product outlet e.

The gasifier 1 is divided into a plurality of sections from bottom to top, which are an oxidation zone 1-A, a transition zone 1-B and a reduction zone 1-C in sequence. The diameters of the transition zone 1-B and the reduction zone 1-C of the gasifier 1 are both D, and the diameter of the oxidation zone 1-A is D ₁ , D and D ₁ are determined by the fluidization velocity of their corresponding regions, D≤D ₁ . Among them, the fluidization velocity in the oxidation zone is 1.5m/s, and the fluidization velocity in the lower part of the transition zone is 3.8m/s. The feeding port c is located in the upper part of the oxidation zone 1-A; the feeding port d is located in the middle and lower part of the transition zone 1-B, h ₀ above the air distribution point of the primary gasification agent, and h ₀ =0.2H. In this embodiment, four secondary gasification agent inlets are set, which are b ₁ to b ₄ , which are located on the same horizontal plane of the furnace and are evenly arranged around the circumference. The inlet of the secondary gasification agent is located at h above the air distribution point of the primary gasification agent, and h=0.18H. The inlet direction of the secondary gasification agent is perpendicular to the vertical centerline of the furnace.

The first-stage gasification agent inlet a is located at the bottom of the furnace, and the 0-6mm pulverized coal enters the gasifier 1 from the feeding port c, and in the oxidation zone 1-A, the first-stage gasification agent reacts mainly with combustion reaction, and release heat. Adjust the air volume of the primary gasification agent, keep the fluidization wind speed at the bottom of the furnace at 1.5m/s, and the large particles that are not carried into the upper part of the furnace flow in a bubbling state in the oxidation zone 1-A, and are combined with the primary gasification. Reaction with the agent, the particle residence time is long, and the full reaction of the solid particles is promoted, and the discharged bottom slag has a low carbon content. Adjust the amount of steam to keep the temperature in the oxidation zone 1-A not higher than 950°C to avoid coking of particles with high ash concentration at the bottom due to high temperature.

Small particles of pulverized coal and carbon-containing solid particles returned to the furnace from the return port d are carried by the gas-solid mixture to move from bottom to top in the furnace. During this process, the gasification agent is gradually consumed and goes through the transition zone 1-B After that, it enters the reduction zone 1-C, which is mainly based on gasification reaction. The secondary gasification agent enters the gasifier 1 from the secondary gasification agent inlet of the transition zone, contacts with high-concentration carbon particles, undergoes an oxidation-based reaction and releases heat, and burns part of the generated combustible gas to form a local The high temperature area promotes the gasification reaction near this area. At the same time, the heat at the local high temperature is carried to the upper part of the furnace under the action of thermal radiation and fluidization, which increases the temperature in the upper part of the furnace. Since the gasification reaction is an endothermic reaction, the increase in temperature provides heat for the gasification reaction in the region above it, which promotes the gasification reaction, thereby improving the gasification efficiency and carbon conversion rate of the system.

The generated coal gas carries the incompletely reacted carbonaceous material into the gas-solid separator 2 from the gasification product outlet e, and most of the particles are collected and returned to the furnace through the descending pipe 3, the return material device 4 and the material return inclined pipe 5 in turn. A small part escapes from the gas-solid separator 2 and enters the subsequent cooling and purification system.

The carbon-containing solid particles returned to the gasifier 1 from the material return port d continue to circulate and participate in the reaction. Since the inlet of the secondary gasification agent is below the material return port c, more returned materials are carried into the area above the material return port c, reducing the It reduces the amount of particles back mixed into the bottom oxidation zone 1-A, increases the concentration of carbon-containing solid particles in the furnace transition zone 1-B and the reduction zone 1-C, promotes the gasification reaction, and increases the retention of solid particles. time, the carbon conversion rate was increased, and the carbon content of the fly ash was reduced.

Among them, the primary gasification agent is a mixture of air and oxygen, and the oxygen-enriched concentration is 30%, and steam is introduced to adjust the temperature and fluidization speed in the bottom oxidation zone 1-A; the secondary gasification agent is the oxygen-enriched concentration. It is 60% oxygen-enriched air, and water vapor is introduced to adjust the fluidization speed and temperature.

Embodiment 3

5 is a schematic diagram of a circulating fluidized bed gasification device according to Embodiment 3 of the present invention. The circulating fluidized bed oxygen-enriched gasification device includes a gasifier 1 , a gas-solid separator 2 , a descending pipe 3 , a returner 4 and a return inclined pipe 5 . The furnace is provided with a primary gasification agent inlet a, a secondary gasification agent inlet (including the first secondary gasification agent inlet b1, the second secondary gasification agent inlet b2, the third secondary gasification agent inlet b3, the second The fourth and secondary gasification agent inlet b4), the feeding port c, the material returning port d, the gasification product outlet e and the throat port f.

The gasifier 1 is divided into a plurality of sections from bottom to top, which are an oxidation zone 1-A, a transition zone 1-B and a reduction zone 1-C in sequence. The diameters of the transition zone 1-B and the reduction zone 1-C of the gasifier 1 are both D, and the diameter of the oxidation zone 1-A is D ₁ , D and D ₁ are determined by the fluidization velocity of their corresponding regions, D≤D ₁ . Among them, the fluidization velocity in the oxidation zone is 2.0m/s, and the fluidization velocity in the lower part of the transition zone is 3.8m/s. The minimum diameter of the throat f is D ₂ =0.6D. The feeding port is located in the upper part of the oxidation zone 1-A; the material returning port is located in the middle and lower part of the transition zone 1-B, at a distance h ₀ above the air distribution point of the primary gasification agent, and h ₀ =0.18H. The throat is located in the lower part of the transition zone 1-B, below the return port. In this embodiment, four secondary gasification agent inlets are set, which are b ₁ to b ₄ , which are located on the same horizontal plane of the furnace and are evenly arranged around the circumference. The inlet of the secondary gasification agent is located at h above the air distribution point of the primary gasification agent, and h=0.25H. The secondary gasification agent enters the inside of the furnace vertically into the gasification furnace 1 .

The first-stage gasification agent inlet a is located at the bottom of the furnace, and the 0-6mm pulverized coal enters the gasifier 1 from the feeding port c, and in the oxidation zone 1-A, the first-stage gasification agent reacts mainly with combustion reaction, and release heat. Adjust the air volume of the primary gasification agent, keep the fluidization wind speed in the oxidation zone at 2.0m/s, and the large particles that are not carried into the upper part of the furnace flow in a bubbling state in the oxidation zone 1-A, and are combined with the primary gasification. Reaction with the agent, the particle residence time is long, and the full reaction of the solid particles is promoted, and the discharged bottom slag has a low carbon content. Adjust the amount of steam to keep the temperature in the oxidation zone 1-A not higher than 950°C to avoid coking of particles with high ash concentration at the bottom due to high temperature.

Small particles of pulverized coal and carbon-containing solid particles returned to the furnace from the return port d are carried by the gas-solid mixture and move from bottom to top in the furnace. After that, it enters the reduction zone 1-C, which is mainly based on gasification reaction. The secondary gasification agent enters the gasifier 1 from the secondary gasification agent inlet of the transition zone, contacts with high-concentration carbon particles, undergoes an oxidation-based reaction and releases heat, and burns part of the generated combustible gas to form a local The high temperature area promotes the gasification reaction near this area. At the same time, the heat at the local high temperature is carried to the upper part of the furnace under the action of thermal radiation and fluidization, which increases the temperature in the upper part of the furnace. Since the gasification reaction is an endothermic reaction, the increase in temperature provides heat for the gasification reaction in the region above it, which promotes the gasification reaction, thereby improving the gasification efficiency and carbon conversion rate of the system.

On the one hand, the throat f set in the gasifier 1 reduces the back-mixing of small particle materials to the lower part of the furnace, improves the concentration of solid particles in the transition zone and the reduction zone, and promotes the gasification reaction in the upper and middle high temperature regions of the furnace. The gasification efficiency and carbon conversion rate are improved, and the carbon content of the fly ash is reduced; on the other hand, the circulation of large-particle solid materials in the oxidation zone is enhanced, the residence time is increased, and the carbon content of the bottom slag is reduced.

The generated coal gas carries the incompletely reacted carbonaceous material into the gas-solid separator 2 from the gasification product outlet e, and most of the particles are collected and returned to the furnace through the descending pipe 3, the return material device 4 and the material return inclined pipe 5 in turn. A small part escapes from the gas-solid separator 2 and enters the subsequent cooling and purification system.

Among them, the first-stage gasification agent is oxygen-enriched air with an oxygen-enriched concentration of 25%, and steam is introduced to adjust the temperature and fluidization speed in the bottom oxidation zone 1-A; the second-stage gasification agent is an oxygen-enriched concentration of 70%. % oxygen-enriched air, and water vapor is introduced to adjust the fluidization speed and temperature.

Embodiment 4

The following takes pulverized coal as an example to specifically describe a circulating fluidized bed oxygen-enriched gasification method according to an embodiment. The method includes the following steps:

(1) The pulverized coal is fed into the furnace from the coal feeding port, the circulating solid particles containing a large amount of incompletely reacted carbon enter the furnace from the return port, and the primary gasification agent enters the furnace from the primary gasification agent inlet at the bottom of the furnace. Coal and return material react with primary gasification agent mainly by combustion reaction, and release heat;

(2) The fluidization velocity at the bottom of the furnace is low (1.5m/s ~ 2.5m/s), so that the large particle materials are not carried into the upper part of the furnace, but continue in the state of bubbling and fluidization in the oxidation zone at the bottom of the furnace React with the primary gasification agent; adjust the proportion and composition of the primary gasification agent, and control the temperature of the oxidation zone not to be higher than 950 °C.

(3) The unreacted primary gasification agent and the generated gas carry the incompletely reacted small particles of carbonaceous materials and heat in the furnace from bottom to top. During this process, the oxidant is gradually consumed, and the reaction in the furnace gradually changes. For the gasification-based reaction, the gasification reaction absorbs heat and consumes the heat released by the combustion reaction.

(4) The secondary gasification agent enters the furnace from the inlet of the secondary gasification agent, contacts with high-concentration carbon particles, reacts and releases heat, and also burns some of the generated combustible gas to release heat, and the released heat is in the second stage. The area near the inlet of the first-stage gasification agent forms a local high temperature area (the maximum temperature can reach 1200 ℃);

(5) The heat released by the reaction between the secondary gasification agent and the combustible material is carried to the upper part of the furnace under the action of thermal radiation and fluidization, which increases the temperature of the upper part of the furnace, provides heat for the gasification reaction in this area, and promotes gasification. the conduct of the reaction;

(6) The generated gas carries the incompletely reacted carbon-containing materials from the gasification product outlet and enters the gas-solid separator. Most of the particles are collected and returned to the furnace through the return feeder, and a small part escapes from the gas-solid separator and enters the Subsequent cooling and purification system.

(7) Most of the small particles of carbon-containing solid materials returned from the material return port are carried to the upper part of the furnace, and continue to circulate and participate in the reaction, and a part of the small particles of carbon-containing materials are mixed back into the lower part of the furnace.

Further, the introduction of the secondary gasification agent is carried out at the position below the material return port, increasing the fluidization speed at the material return port, and more materials returned from the material return port are carried into the area above the material return port. multiple cycles.

Preferably, a throat port is provided below the material return port, and the setting of the throat port enables the small particle materials returned from the material return port to move more toward the upper part of the furnace under the structural constraints and high fluidization speed at the throat port. The back mixing of the returned material to the lower part of the furnace is improved, and the concentration of the small particle material in the high temperature circulation loop above the throat is increased.

It should be noted that, by adjusting the furnace diameter and the distribution ratio of the gasification agent, it is possible to maintain a low fluidization speed in the oxidation zone at the bottom of the furnace, prolong the residence time of large-particle solid materials here, ensure its full reaction, and reduce the bottom of the furnace. Slag carbon content.

Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that changes may be made to these embodiments without departing from the principles and spirit of the present invention. The scope of applicability of the present invention is defined by the appended claims and their equivalents.

List of reference numbers:

1 Gasifier

2 Gas-solid separator

3 Downpipes

4 Feeder

5 Return inclined tube

1-A Oxidation Zone

1-B Transition Area

1-C Recovery Area

a Primary gasification agent inlet

b1 First and second stage gasification agent inlet

b2 Second stage gasification agent inlet

b3 The third stage gasification agent inlet

b4 Fourth stage gasification agent inlet

c feed port

d return port

e Gasification product outlet

f Throat.

Claims (11)

1. A circulating fluidized-bed gasification device, comprising a gasifier, a gas-solid separator and a returner, the gasifier is communicated with the gas-solid separator, the gas-solid separator is communicated with the returner, and the returner is connected with the feeder. The gasifier is connected, and it is characterized in that: The gasification furnace is provided with a gasification agent inlet, a feeding port, a material return port and a gasification product outlet, wherein the gasification agent inlet includes a primary gasification agent inlet and a secondary gasification agent inlet, and the the primary gasification agent inlet is located at a first position, the secondary gasification agent inlet is located at a second position different from the first position, Wherein, the gasifier includes a throat with a diameter reduced relative to the main body of the gasifier, Wherein, the throat is located below the material return port, Wherein, the gasifier is divided into an oxidation zone, a transition zone and a reduction zone from bottom to top, the throat is located at the lower part of the transition zone, and the throat is a "><" type structure, Wherein, the inlet of the primary gasification agent is located at the bottom of the gasifier, the inlet of the secondary gasification agent is located in the transition zone of the gasifier, the feeding port is located at the upper part of the oxidation zone, and the primary gasification agent is air or Oxygen-enriched air with an oxygen-enriched concentration <40%, or air or a mixture of oxygen-enriched air and water vapor with an oxygen-enriched concentration of <40%, and the secondary gasification agent is oxygen-enriched air with an oxygen-enriched concentration >50% or oxygen, or For oxygen-enriched air with an oxygen-enriched concentration greater than 50% or a mixture of oxygen and water vapor, the fluidization velocity at the bottom of the gasifier is controlled at 1.5m/s to 2.5m/s. 2 . The circulating fluidized bed gasification device according to claim 1 , wherein the inlet of the secondary gasification agent is located below the middle of the gasifier. 3 . 3. The circulating fluidized bed gasification device according to claim 2, characterized in that: the height of the furnace of the gasifier is H, the height of the material return port from the bottom of the furnace is h ₀ , and 0.1H≤h ₀ ≤ 0.3H. 4 . The circulating fluidized bed gasification device according to claim 3 , wherein the height of the secondary gasification agent inlet from the bottom of the furnace is h, and h≦h ₀ . 5 . 5. The circulating fluidized bed gasification device according to claim 1, wherein the gasification agent inlet comprises a plurality of secondary gasification agent inlets, and the plurality of secondary gasification agent inlets are distributed in the same layer, Or distributed in multiple layers along the height direction of the gasifier. 6 . The circulating fluidized bed gasification device according to claim 5 , wherein the projections of the secondary gasification agent inlets of different layers on the cross section perpendicular to the height direction of the gasifier are staggered. 7 . 7. The circulating fluidized bed gasification device according to claim 1, wherein the gasifier comprises an oxidation zone, a transition zone and a reduction zone from bottom to top, and the diameters of the transition zone and the reduction zone are is D, the diameter of the oxidized region is D ₁ , and D≦D ₁ . 8. A circulating fluidized bed gasification method, using the circulating fluidized bed gasification device according to any one of claims 1-7, wherein the circulating fluidized bed gasification method comprises: (1) The fuel enters the gasifier from the feed port, the circulating solid particles containing incompletely reacted carbon enter the gasifier from the return port, the primary gasification agent enters the gasifier from the primary gasification agent inlet, and the fuel The reaction with the return material and the primary gasification agent is mainly based on the combustion reaction, and heat is released; (2) The secondary gasification agent enters the gasifier from the inlet of the secondary gasification agent, contacts with carbon particles, reacts and releases heat, and at the same time burns part of the generated combustible gas to release heat; (3) the gasification product carries the incompletely reacted carbonaceous material into the gas-solid separator from the gasification product outlet; (4) The circulating solid particles separated by the gas-solid separator are returned to the gasifier through the return device, and the gasified substances separated by the gas-solid separator are collected, The fluidization speed at the bottom of the gasifier is controlled at 1.5m/s to 2.5m/s, wherein the primary gasification agent is air or oxygen-enriched air with an oxygen-enriched concentration <40%, or air or an oxygen-enriched concentration of less than 40%. <40% mixture of oxygen-enriched air and water vapor, and the secondary gasification agent is oxygen-enriched air or oxygen with oxygen-enriched concentration >50%, or oxygen-enriched air with oxygen-enriched concentration >50% or oxygen and water vapor mixture. 9. The circulating fluidized bed gasification method according to claim 8, wherein the gasifier forms bottom-up oxidation zone, transition zone and reduction zone during operation, and the temperature of the oxidation zone is controlled not to higher than 950°C. 10 . The circulating fluidized bed gasification method according to claim 8 , wherein the reaction temperature of the gasifier is between 850° C. and 1200° C. 11 . 11 . The circulating fluidized bed gasification method according to claim 8 , wherein the oxygen content in the secondary gasification agent accounts for 10% to 60% of the total oxygen content of the gasification agent. 12 .

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