CN107043641A - Circulation fluidized bed coal gasifying method and device with fine ash loopback - Google Patents

Abstract

A kind of circulation fluidized bed coal gasifying method with fine ash loopback, comprises the following steps：A) coal (B1) and gasifying agent (A) are passed through circulation fluidized bed coal gasifying stove (1) and carry out gasification reaction, generation coal gas (C) and gasification fine ash (D)；B) coal gas (C) is separated with gasification fine ash (D)；C) the gasification fine ash (D) after separation is collected；D) step c) the gasification fine ash (D) obtained and oxidant (G) are sent into melting plant (3)；E) rich carbon high-temp gas (H1) and high-temperature slag (H2) are generated；And f) rich carbon high-temp gas (H1) and high-temperature slag (H2) be transmitted back in the gasification furnace burner hearth (10) of circulation fluidized bed coal gasifying stove (1).The present invention also provides a kind of circulation fluidized bed coal gasifying device with fine ash loopback.The circulation fluidized bed coal gasifying method and apparatus efficiency of carbon con version with fine ash loopback of the present invention is high, and environmental pollution is small.

Description

Circulating fluidized bed coal gasification method and device with return of fine powder ash

technical field

The invention belongs to the technical field of coal gasification, and relates to a coal gasification method and device, in particular to a circulating fluidized bed coal gasification method with fine powder ash return and a device using the method.

Background technique

Classified according to the movement state of solid fuel, modern coal gasification processes mainly include moving bed (also known as fixed bed) gasification, entrained bed gasification and fluidized bed gasification.

The moving bed coal gasification process mainly uses lump coal as raw material, and its main advantages include: low-quality coal can be used for gasification; high pressure gasification production capacity; low oxygen consumption, which is the lowest oxygen consumption among the three types of coal gasification methods The method; the operating temperature of the reaction furnace and the outlet gas temperature are low, the carbon efficiency is high, and the gasification efficiency is high. However, since the moving bed gasification can only use non-stick lump coal as raw material, not only the raw material is expensive, the gasification intensity is low, but also the gas-solid countercurrent heat exchange, the crude gas contains more phenols, tar, etc., which lengthens the purification process. Increased investment and cost.

The entrained bed coal gasification furnace has a high reaction temperature and adopts liquid slag discharge, which has high gasification intensity, large production capacity, and high carbon conversion rate. High; in order to maintain the high reaction temperature in the furnace, pure oxygen is often used as the oxidizing agent, and the oxygen consumption is high, which affects the economy.

Fluidized bed coal gasification technology can use 0-10mm crushed coal without sieving, and the processing cost is low; the gasification intensity is 2-3 times that of the moving bed; air gasification can be used, and the oxygen consumption is low; crude gas The outlet temperature is high; the product gas hardly contains tar and phenols. Such technologies include traditional fluidized bed coal gasification technology and circulating fluidized bed coal gasification technology developed in recent years. Among them, the circulating fluidized bed coal gasification furnace has a material circulation loop with a high circulation rate, and the fluidization velocity is higher than that of the traditional fluidized bed gasification furnace. It has strong applicability of coal types, sufficient gas-solid mixing, and gasification reaction It has the advantages of high rate, uniform temperature of the whole reactor, desulfurization in the furnace by adding limestone, etc. But there are also limitations: on the one hand, unlike traditional fluidized bed coal gasifiers where the gasification reaction is mainly carried out in the lower part of the furnace, circulating fluidized bed coal gasifiers are Given the location and other factors, the fluidization velocity of the furnace is high, and a large amount of coal particles and unreacted carbon will enter the middle and upper part of the furnace for gasification reaction. Therefore, the middle and upper part of the furnace is in the reduction zone, and a large amount of heat is required to obtain high gasification. efficiency, but at the same time, the heat that can be carried to the upper part of the furnace is limited, which seriously affects the gasification efficiency in the furnace; on the other hand, due to the low gasification operating temperature and high fluidization velocity, although the large particles Carbon will participate in the reaction again through circulation, but the carbon content in the fine powder ash entrained by the airflow is still considerable. Generally, fly ash accounts for 70% to 80% of the total ash, and the mass fraction of carbon accounts for 30% to 50%. As a result, the total carbon utilization rate of the system is not high; in addition, due to the large amount of gasification fine powder ash and high carbon content, the utilization and disposal of fine powder ash is also a big problem.

Aiming at the problems of low total carbon utilization rate of traditional fluidized bed coal gasifier and circulating fluidized bed coal gasifier and the treatment of fine powder ash, there are mainly the following solutions: (1) Combine the fine powder ash brought out of the fluidized bed with The hot gas is introduced into the entrained-bed coal gasifier together for high-temperature secondary gasification, and the high-temperature gas carrying fine powder ash after secondary gasification is discharged into the entrained-bed coal gasifier; (2) the traditional fluidized bed or circulating fluidized bed gas is The fine powder ash carried out in the furnace is separated from the product gas and sent to the entrained bed coal gasifier for high-temperature reaction. The ash and high-temperature gas generated by the reaction are returned to the lower part of the traditional fluidized bed or circulating fluidized bed to realize dry exhaust gasification. (3) Partially separate the fine powder ash carried out in the traditional fluidized bed or circulating fluidized bed coal gasifier from the product gas and send it into the gas flow The bed is burned at high temperature, liquid slag is discharged, and the high-temperature flue gas returns to the lower part of the traditional fluidized bed or circulating fluidized bed to supplement heat for the lower part of the traditional fluidized bed or circulating fluidized bed.

It is an effective way to improve the carbon conversion rate of the system by sending the fine powder ash generated by the reaction in the traditional fluidized bed or circulating fluidized bed coal gasifier into the high temperature reactor for secondary reaction, but there are the following technical problems: first, the gasification The fine powder ash has low volatile content, no water, and poor reactivity. It cannot be ignited by conventional means, let alone achieve stable combustion. There is no practical solution for this in the prior art; secondly, the amount of gasified fine powder ash produced is very Significantly, if it cannot be discharged smoothly after recycling, the circulation volume of the system will continue to increase, and eventually the system cannot continue to operate; thirdly, the heat recycling after carbon conversion in the fine powder ash of the prior art is mainly used for supplementing heat in the lower part of the gasifier , while the upper part of the gasifier furnace is a severe gasification reduction zone, which requires a lot of heat to improve the gasification reaction efficiency. Therefore, for circulating fluidized bed coal gasifiers, supplementing heat from the lower part of the gasifier cannot fundamentally solve the problem of gasification. The problem of supplementary heat; Fourth, if liquid slag discharge is adopted after the secondary reaction, the slag is usually cooled by water quenching, which is easy to produce black water and pollute the environment.

Contents of the invention

The purpose of the present invention is to overcome the defects of the prior art and provide a circulating fluidized bed coal gasification method and device which can properly dispose gasification fine powder ash.

The purpose of the present invention is also to provide a circulating fluidized bed coal gasification method and device that can fully utilize the combustible components in the fine powder ash and improve the carbon conversion rate.

The purpose of the present invention is also to provide a circulating fluidized bed coal gasification method and device which simplify the system, save costs and minimize pollution.

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

According to one aspect of the present invention, a kind of circulating fluidized bed coal gasification method with fine powder ash return is proposed, comprises the steps:

a) Pass coal and gasification agent into circulating fluidized bed coal gasification furnace for gasification reaction to generate coal gas and gasification fine powder ash;

b) separating coal gas from gasification fine powder ash;

c) collecting the gasified fine powder ash after separation;

d) sending the gasified fine powder ash and oxidant obtained in step c) into a melting device;

e) Generate carbon-rich high-temperature gas and high-temperature slag by means of a melting device; and

f) Returning the carbon-rich high-temperature gas and high-temperature slag to the hearth of the gasifier of the circulating fluidized bed coal gasifier.

According to a preferred embodiment of the present invention, further comprising the following steps:

Using the viscosity of high temperature slag, the gasification fine powder ash is converted into bottom slag and sinks into the bottom of the gasifier hearth of the circulating fluidized bed coal gasifier; and

Drain the bottom residue.

According to a preferred embodiment of the present invention, step d) also includes feeding the pulverized coal into a melting device.

According to a preferred embodiment of the present invention, in step e), by adjusting the composition of the oxidant and the ratio of the gasified fine powder ash, the reaction temperature of the oxidant and the gasified fine powder ash is controlled, so that the generated carbon-rich high-temperature gas and the temperature t of the high-temperature slag satisfy t ₂ -50°C≤t≤t ₂ +250°C, where t ₂ is the softening temperature of the ash content of the gasified fine powder ash.

According to a preferred embodiment of the present invention, in step d), the gasified fine powder ash is first preheated to 800°C-950°C in the fuel preheating section of the melting device, and then enters the high temperature melting section of the melting device; Wherein, the oxidizing agent is sent into the high-temperature melting section of the melting device.

According to a preferred embodiment of the present invention, in step d), the gasified fine powder ash and pulverized coal are first preheated to 800°C-950°C in the fuel preheating section of the melting device, and then enter the high temperature of the melting device Melting section; wherein, the oxidizing agent is sent into the high-temperature melting section of the melting device.

According to a preferred embodiment of the present invention, step b) is specifically to use the separation device and/or dust collector of the circulating fluidized bed coal gasifier to separate the coal gas from the gasification fine powder ash, and the coal gas is drawn out.

According to a preferred embodiment of the present invention, the separation device for separating coal gas and gasification fine powder ash is a two-stage or more-stage separation device.

According to a preferred embodiment of the present invention, the carbon-rich high-temperature gas is returned to the reduction zone of the hearth of the gasifier, or the transition zone between the oxidation zone and the reduction zone.

According to another aspect of the present invention, a circulating fluidized bed coal gasification device with fine powder ash return is proposed, including a circulating fluidized bed coal gasification furnace and a melting device:

A circulating fluidized bed coal gasifier has a coal inlet, a gasification agent inlet, a molten product inlet, a coal gas outlet, and one or more outlets for gasification fine powder ash, and the circulating fluidized bed coal gasifier includes a gasification furnace hearth and separation device;

The melting device has an oxidant inlet and a melting product outlet, and the melting device communicates with the gasification fine powder ash discharge port, and the melting device is connected with the circulating fluidized bed coal gasification furnace through the melting product outlet, and is used to convert the carbon-enriched gas produced in the melting process The high temperature gas and high temperature slag are returned to the furnace of the gasifier.

According to a preferred embodiment of the present invention, the gasifier hearth of the circulating fluidized bed coal gasifier has a slagging outlet arranged at the bottom of the gasifier hearth for discharging the slag that sinks into the bottom of the gasifier hearth. scum.

According to a preferred embodiment of the present invention, the melting device is also communicated with the pulverized coal inlet.

According to a preferred embodiment of the present invention, the melting device is composed of a fuel preheating section and a high temperature melting section, the gasification fine powder ash outlet is connected to the fuel preheating section, and the oxidant inlet is arranged on the high temperature melting section.

According to a preferred embodiment of the present invention, the melting device is composed of a fuel preheating section and a high temperature melting section, the gasification fine ash outlet and the pulverized coal inlet are connected to the fuel preheating section, and the oxidant inlet is set on the high temperature melting section.

According to a preferred embodiment of the present invention, the separation device is a two-stage or more-stage separation device.

According to a preferred embodiment of the present invention, the circulating fluidized bed coal gasifier further includes a return valve, at least a part of the circulating material is returned to the gasifier hearth of the circulating fluidized bed coal gasifier through the return valve.

According to a preferred embodiment of the present invention, the circulating fluidized bed coal gasifier further includes an ash collector, at least a part of the gasified fine powder ash separated by the separation device is sent into the ash collector, and the melting device passes the ash collector The device communicates with the gasification fine powder ash outlet.

According to a preferred embodiment of the present invention, the circulating fluidized bed coal gasifier further includes a dust collector, at least a part of the gasification fine dust separated by the separation device and the gasification fine dust collected by the dust collector are sent into An ash collector, the melting device communicates with the gasification fine powder ash outlet through the ash collector.

According to a preferred embodiment of the present invention, the separation device includes a first-stage cyclone separator and a second-stage cyclone separator connected in sequence, and the dust collector is a bag filter; the inlet and outlet of the return valve are respectively connected to the The solid circulating material outlet of the first-stage cyclone separator is connected with the return port of the gasifier hearth, and the solid outlet of the second-stage cyclone separator is connected to the inlet of the ash collector as the gasification fine powder ash discharge outlet. The ash discharge port of the device is connected with the inlet of the ash collector as the gasification fine powder ash discharge port.

According to a preferred embodiment of the present invention, the molten product inlet is arranged in the reduction zone of the hearth of the gasifier, or in the transition zone between the oxidation zone and the reduction zone.

According to a preferred embodiment of the present invention, the high-temperature melting section includes a swirl nozzle and a melting zone, wherein the swirl nozzle communicates with the fuel preheating section, the oxidant inlet is arranged on the swirl nozzle, and the melting zone is provided with the molten product Export.

The invention converts gasified fine powder ash into high-temperature molten slag and sends it back to the furnace of the gasification furnace, utilizes the viscosity of the molten slag to turn it into bottom slag and discharges it out of the gasification furnace, thereby solving the problem of fine powder ash disposal, and at the same time providing The gasification reaction in the furnace provides heat and reactants that increase the carbon conversion of the gasifier. The circulating fluidized bed coal gasification method and device of the present invention have high carbon conversion rate, good gas quality, double zero discharge of flue gas and powdery fly ash, no black water causing secondary pollution to the environment, reliable operation, and low initial investment .

Description of drawings

Fig. 1 is the overall schematic diagram of the circulating fluidized bed coal gasification method according to the present invention with fine powder ash return;

2 is a schematic diagram of a circulating fluidized bed coal gasification method with fine powder ash return according to an embodiment of the present invention; and

Fig. 3 is a schematic diagram of a circulating fluidized bed coal gasification device with fine powder ash return according to an embodiment of the present invention.

detailed description

Exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements. In addition, in the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a comprehensive understanding of the embodiments of the present disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in diagrammatic form to simplify the drawings.

According to the general inventive concept of the present invention (see Fig. 1), the present invention sends coal B1 into circulating fluidized bed coal gasification furnace 1 for gasification, and separates gasification fine powder ash D from coal gas C and passes it into melting device 3 , feed the oxidant G into the melting device 3, make the gasification fine powder ash D react with the oxidant G, generate carbon-rich high-temperature gas H1 and high-temperature slag H2, and pass them back into the hearth of the gasifier to form a gasification reaction Provide heat source and reactants, thereby improving the overall carbon conversion rate and gas quality in the circulating fluidized bed coal gasification process; at the same time, relying on the viscosity of high-temperature slag, the gasification fine powder ash can be transformed into larger particles that can sink into The bottom slag L at the bottom of the furnace is then discharged out of the system, thereby realizing zero discharge of powdery fly ash in the system.

The method and device of the present invention will be further explained below in conjunction with the embodiments of the present invention.

Fig. 2 is a schematic diagram of a circulating fluidized bed coal gasification method with return of fine ash according to an embodiment of the present invention. As shown in Figure 2, the method of the present invention comprises the steps:

a) Pass coal B1 and gasification agent A into circulating fluidized bed coal gasifier 1 for gasification reaction to generate coal gas C and gasified fine powder ash D1;

b) Using the separation device of the circulating fluidized bed coal gasifier 1 to separate the coal gas C from the gasified fine powder ash D1, the coal gas C is dedusted and purified by the dust collector 15 and becomes a clean gas C1 lead-out system;

c) Send the gasified fine powder ash D1 and D2 captured by the separation device of the circulating fluidized bed coal gasifier 1 and the dust collector 15 into the ash collector 2, and mix to obtain the mixed fine powder ash E;

d) Send the mixed fine powder ash E and a certain amount of pulverized coal B2 into the melting device 3, and the two are firstly preheated to 800°C-950°C in the fuel preheating section 31 of the melting device 3, and then enter the high temperature melting section 32;

e) Pass the oxidant G into the high-temperature melting section 32 to react with the mixed fine powder ash E and pulverized coal B2 to generate a molten product H, including carbon-rich high-temperature gas H1 rich in CO and CO and high-temperature slag _H2 ;

f) Return the carbon-rich high-temperature gas H1 and high-temperature slag H2 to the hearth of the gasification furnace to make them participate in the gasification reaction of coal and gasification agent.

Wherein, it is also possible to send only the gasified fine powder ash collected by the separating device or the dust collector 15 of the circulating fluidized bed coal gasification furnace 1 into the melting device 3, and the ash collector 2 is not provided at this time. Circulating fluidized bed coal gasifier 1 may only be provided with a single-stage separation device or a multi-stage separation device, typically a two-stage cyclone separator. When the coal gas C flows through the first-stage separator, a large amount of solid material captured and sent back to the furnace of the gasifier through the return valve; when the gas C flows through the second-stage separator, most of the gasified fine powder ash D1 is captured, and when it flows through the bag filter, the remaining The gasified fine powder ash D2 is further captured. Since the gas generally flows through the heat exchanger before entering the bag filter and is cooled (sometimes a gas cooling device is also arranged between the separators), the temperature of the captured gasified fine powder ash decreases step by step, so The temperature of mixed fine powder ash can generally be lower than 600°C.

Among them, when the circulating fluidized bed coal gasifier 1 is equipped with a multi-stage separation device, typically a two-stage cyclone separator, when the coal gas C flows through the first-stage separator, a large amount of solid materials are captured and passed through the return valve. As circulating material, it is sent back to the furnace of the gasifier, and the gasification fine powder ash with a finer particle size than the circulating material is carried by the gas C, discharged from the gas outlet of the first-stage separator, and enters the second-stage separator. The gasified fine powder ash D1 is captured by the second stage separator, and when the gas flows through the bag filter, the remaining gasified fine powder ash D2 is further captured. When the circulating fluidized bed coal gasifier 1 is equipped with a three-stage separator, the gasified fine powder ash D1 is collected by the second-stage and third-stage separators. (The first stage of the multi-stage separation device is used to separate the circulating materials, and the subsequent stages are used to separate the gasification fine powder ash, so the number of stages of the separation device used to separate coal gas and gasification fine powder ash is always higher than that of the separation device The total number of stages is one less; if the solid material collected by the second stage separator is also sent back to the furnace, then the collected material of this stage separator is also a circulating material, which is not used as gasification fine powder ash, and is used to separate gas at this time The number of stages of the separation device with gasification fine powder ash is two less than the total number of stages of the separation device). Because a gas cooling device is often arranged between the separators to reduce the volume of the rear separator, and at the same time, the gas often flows through the heat exchanger before entering the bag filter to be cooled to a temperature suitable for the filter, and the captured The temperature of gasified fine powder ash decreases step by step, so the temperature of mixed fine powder ash E can generally be lower than 600°C. At this temperature, it is less difficult to convey the fine powder ash, and there is no need to lower the temperature before conveying to the melting furnace 3, which avoids the loss of sensible heat of the fine powder ash and is beneficial to the melting reaction.

When the circulating fluidized bed coal gasifier 1 is only equipped with a single-stage separation device, the separation device only separates the circulating material from the gas, and the gasified fine powder ash is separated from the gas through the dust collector. However, for a coal gasification system without a dust collector, that is, a system that directly utilizes hot raw gas, the gasified fine powder ash only comes from the separation device of the circulating fluidized bed coal gasification furnace 1 except for the first stage; if the separation device There are only two stages, so the circulating fluidized bed coal gasification furnace 1 only has the gasification fine powder ash discharge outlet of the solid outlet of the second-stage separation device. In the above two cases, there is no "send the gasified fine powder ash D1 and D2 collected by the separation device of the circulating fluidized bed coal gasifier 1 and the dust collector 15 into the ash collector 2, and mix them to obtain the mixed fine powder ash E "step, the circulating fluidized bed coal gasification device is also not provided with ash collector 2. For the convenience of description, the following "mixed fine powder ash E" also includes the case of only gasified fine powder ash from the secondary separator.

Wherein, both the gasifying agent A and the oxidizing agent G can be the following components or a combination of components: air, air+steam, oxygen-enriched air, oxygen-enriched air+steam, pure oxygen, pure oxygen+steam, etc. The choice of oxidant G is related to the ash melting point, the operating temperature of the melting device 3, the calorific value of the mixture of mixed fine powder ash E and pulverized coal B2, and the composition of the required carbon-rich high-temperature gas H1. Adjustments are made for changes in the calorific value of the mixture of Ash E and Pulverized Coal B2.

In step d, the amount of pulverized coal B2 added can be zero, and can also be adjusted according to the calorific value of the mixed fine powder ash E, the required operating temperature of the melting device 3, and the composition of the required carbon-rich high-temperature gas H1, the purpose of which is to Ensure that the calorific value of the mixture of fine powder ash E and pulverized coal B2 reaches the required operating temperature of the melting device 3 under the condition that the required carbon-rich high-temperature gas H1 can be obtained.

By adjusting the composition of the oxidant and its ratio to the gasified fine powder ash, the reaction temperature between the gasified fine powder ash and the oxidant is controlled, so that the temperature t of the generated carbon-rich high-temperature gas and high-temperature slag is t ₂ -50℃≤t ≤t ₂ +250°C, t ₂ is the softening temperature of gasified fine powder ash; for common coal types, t is about 1200°C to 1700°C;

Swirl nozzles and directional guide vanes can be installed in the high-temperature melting section 32. By adjusting the structure of the swirling nozzle, the injection speed of the preheated fine powder ash F and the oxidant G, and the angle of the directional guide vanes, it is ensured that a high temperature is formed in the high-temperature melting section 32. The molten slag H2 is sprayed into the hearth of the gasifier 1 along with the carbon-rich high-temperature gas H1.

In step f, the carbon-rich high-temperature gas H1 and high-temperature slag H2 are preferably returned to the reduction zone of the hearth of the circulating fluidized bed coal gasification furnace 1, or the transition zone between the oxidation zone and the reduction zone. On the one hand, the temperature of carbon-rich high-temperature gas H1 and high-temperature slag H2 is very high, and sending them back to the furnace can make full use of their sensible heat and promote gasification reaction; on the other hand, the main component of carbon-rich high-temperature gas H1 is that the oxygen content is close to 0 The flue gas or dry gas, or the mixture of either of them and steam, after being passed into the furnace, the C, CO ₂ , CO and other components in it can also participate in the coal gasification reaction. This action provides a heat source and reactants for the intense gasification reaction in the reduction zone of the gasifier hearth, which makes up for the defect of insufficient heat in the reduction zone of the existing technology, thereby improving the gasification efficiency and gas quality of the circulating fluidized bed coal gasifier . In addition, zero emission of flue gas from the whole system has been realized. The high-temperature slag H2 at 1200°C to 1700°C is viscous and will stick to each other, or stick to other solid particles, or coat the outer layer of other solid particles, so that the particle size becomes larger, and the temperature in the gasifier is generally 950~ At 1000°C, the sensible heat of the high-temperature slag H2 is absorbed by the gasification reaction, the temperature of the slag decreases, and the increase in particle size stops, so that it does not become too large; the slag falls to the lower part of the gasifier under the action of gravity, and finally Ordinary solid bottom slag L is discharged from the system.

Circulating fluidized bed coal gasification furnaces have lower requirements on the particle size of the discharged bottom slag, but it is also necessary to avoid excessive volume of molten slag falling into the lower part of the furnace, which will affect the pressure of the circulating fluidized bed coal gasification furnace and the flow in the furnace. change. The final volume of the slag depends on the temperature of the high-temperature slag H2 and the conditions in the furnace of the gasifier. The droplet-shaped high-temperature melting can be adjusted by adjusting the temperature of the high-temperature melting section 32, the structure of the swirl nozzle, and the angle of the directional vane. The volume and temperature of slag H2.

The melting device 3 includes a fuel preheating section 31 and a high temperature melting section 32 . The mixture of mixed fine powder ash E and pulverized coal B2 is first sent to the fuel preheating section 31, so that the high-temperature melting section 32 is in the half of the fuel with low volatile content, poor reactivity, high ignition point, slow combustion reaction rate, and long burnout time. It is possible to achieve rapid reaction and high-temperature melting under the condition of coke; at the same time, according to the reaction temperature requirements of the high-temperature melting section 32, the calorific value of the mixture of mixed fine powder ash E and pulverized coal B2, and the difference in ash melting point, targeted to the high-temperature melting section 32. Different oxidizing agents G are introduced to make the high-temperature preheated fine powder ash F react quickly and fully with the oxidizing agent, reach the melting temperature, and generate carbon-rich high-temperature gas H1 and high-temperature liquid slag H2.

In the entire gasification system, except for the circulating ash circulating in the main circulation loop and a small amount of fly ash brought back to the circulating fluidized bed coal gasification furnace 1 by the carbon-rich high-temperature gas H1, the rest of the gasification fly ash enters the melting device It is melted at high temperature and enters the circulating fluidized bed coal gasifier 1 in the form of molten slag, and then discharged from the bottom of it. There is no fly ash discharge system, thus realizing zero discharge of powdery fly ash in the entire gasification system. The entire system completes the discharge of all solid waste in the form of bottom slag, and there is no slag cooling link, and no black water is generated, so that it does not cause secondary pollution to the environment. While simplifying the system and saving costs, it minimizes pollution .

The high-temperature melting section 32 can be a reducing atmosphere or an oxidizing atmosphere: on the basis of ensuring the melting temperature, according to the calorific value of the mixture of mixed fine powder ash E and pulverized coal B2 and the needs of the gasifier for the composition of carbon-rich high-temperature gas H1, through The reaction atmosphere of the high-temperature melting section 32 is controlled by adjusting the composition of the oxidant, the amount of the oxidant, and the preheating temperature. In an oxidizing atmosphere, the carbon-rich high-temperature gas H1 can provide high-temperature sensible heat and CO ₂ reactants to the gasifier; in a reducing atmosphere, the carbon-rich high-temperature gas H1 can provide high-temperature sensible heat and CO and other reactants to the gasifier; atmosphere, by controlling the oxygen content in the oxidant G, the oxygen content in the generated carbon-rich high-temperature gas H1 can be nearly zero.

The oxidizing agent G is at room temperature or 500°C to 800°C. When the oxidant G is pure oxygen, it is directly passed into the high-temperature melting section at room temperature. When the oxidant G is air or oxygen-enriched air and the oxidant contains steam, it can be preheated to 500°C to 800°C to facilitate melting.

The circulating fluidized bed coal gasification method according to the present invention has the following advantages:

1) After the fine powder ash entrained by the gas is reacted in the melting device, the semi-coke contained in the fine powder ash with low volatile content, no water, and poor reactivity can be completely converted, thereby increasing the total carbon of gasification. Conversion rate;

2) The carbon-rich high-temperature gas generated in the melting device enters the reduction zone of the gasifier furnace or the transition zone between the oxidation zone and the reduction zone, and its sensible heat is maximized to promote the coal gasification reaction. At the same time, the carbon-rich gas can Participate in the coal gasification reaction, provide chemical heat for it, and improve the gasification efficiency and effective gas composition of the circulating fluidized bed coal gasifier;

3) The high-temperature slag generated in the melting device enters the reduction zone of the gasifier furnace or the transition zone between the oxidation zone and the reduction zone, and its sensible heat is maximized to promote the coal gasification reaction while increasing this part of carbon. The residence time in the gasifier furnace, thereby increasing the carbon conversion rate of the circulating fluidized bed coal gasifier;

4) The entire system completes the discharge of all solid waste in the form of bottom slag, realizes zero discharge of powdery fly ash in the entire system, avoids cooling of slag, and minimizes waste while simplifying the system and saving costs pollution;

5) All the high-temperature gas generated by the reaction in the melting device is passed into the circulating fluidized bed coal gasifier to participate in recirculation, realizing zero emission of system flue gas;

6) In the melting device, by preheating the raw materials and adjusting the oxidant, the problem of rapid high-temperature melting of gasified fine powder ash without auxiliary fuel is solved.

The coal gasification method of the invention can be used not only for the gasification of raw coal, but also for the gasification process of carbon-based fuels such as biomass and garbage.

Fig. 3 is a schematic diagram of a circulating fluidized bed coal gasification device with fine powder ash return according to an embodiment of the present invention. As shown in FIG. 3 , the device of the present invention includes a circulating fluidized bed coal gasifier 1 , an ash collector 2 and a melting device 3 .

Wherein, the circulating fluidized bed coal gasification furnace 1 includes: a gasification furnace hearth 10, which is provided with an outlet, a coal feeding port, a material return port, a molten product inlet, a gasification agent inlet and a slag discharge port; a primary separator 11, It is provided with an inlet, a solid circulating material outlet and a gas outlet, wherein the inlet communicates with the outlet of the gasifier hearth 10; The outlet communicates with the return port of the gasifier hearth 10; the secondary separator 13 is provided with an inlet, a solid outlet and a gas outlet, wherein the inlet communicates with the gas outlet of the primary separator 11; the heat exchanger 14 can be It is a heat exchange device such as an air preheater and a gas cooler, which is provided with a high-temperature gas inlet, an outlet, and a cooling medium inlet and outlet, and its high-temperature gas inlet communicates with the gas outlet of the secondary separator 13; and a bag filter 15, It is provided with an inlet, an ash outlet and a clean gas outlet, and the inlet communicates with the high-temperature gas outlet of the heat exchanger 14 .

The ash collector 2 is used to collect and mix all the gasified fine powder ash in the system, and its inlet is connected to the solid outlet of the secondary separator 13 (that is, the gasified fine powder ash outlet of the secondary separator 13), the bag filter 15 The ash outlet (i.e. the gasification fine powder ash outlet of dust collector 15) communicates.

The melting device 3 is composed of a fuel preheating section 31 and a high-temperature melting section 32. The fuel preheating section 31 is provided with a fuel inlet and a preheated fuel outlet, and its fuel inlet communicates with the outlet of the ash collector 2; the high-temperature melting section 32 includes A swirl nozzle 321 and a melting zone 322, wherein the swirl nozzle 321 is provided with a fuel inlet and an oxidizer inlet, and the melting zone 322 is provided with a molten product outlet; the fuel inlet is directly connected with the preheated fuel outlet of the fuel preheating section 31, and the molten product The outlet communicates directly with the molten product inlet of the furnace 10 of the gasifier.

According to a preferred embodiment of the present invention, the gas is cooled by passing through the heat exchange device after passing through the separation device and before entering the dust collector; the heat exchange device is an air preheating device or a gas cooling device; specifically, in the first stage An air preheating device, gas cooling device or waste heat boiler is arranged between the separator and the second stage separator. The gasification agent A is air, oxygen-enriched air or pure oxygen, or a combination of one of the aforementioned three and steam; the oxidant G is air, oxygen-enriched air or pure oxygen, or a combination of one of the aforementioned three and steam Combination; the oxidizing agent (G) is at room temperature or at a temperature of 500°C to 800°C.

The following briefly describes the working process of the circulating fluidized bed coal gasification device with return of fine powder ash according to the embodiment of the present invention. Coal B is fed into the gasifier hearth 10 from the coal inlet, and gasification agent A enters the gasifier hearth 10 from the gasification agent inlet. After the small particles of carbon and ash pass through the primary separator 11, the incompletely reacted carbon and ash of larger particles are separated by the primary separator 11 and returned to the gasifier hearth 10 through the return valve 12 to form a main circulation loop Material circulation; part of the incompletely reacted small particle carbon and ash is separated by the secondary separator 13 and sent to the ash collector 2 as high-temperature gasification fine powder ash D1 (about 800 ° C); the other part of incompletely reacted small particles Carbon and ash are carried by the gas, and after being cooled by the heat exchanger 14, they enter the bag filter 15 at the tail end. After being separated by the bag filter 15, the clean product gas C1 is discharged from the system, and the low-temperature gasification fine powder ash D2 (about 100°C) Enter ash collector 2. After the high-temperature gasified fine powder ash D1 and the low-temperature gasified fine powder ash D2 are mixed in the ash collector 2, a medium-temperature mixed fine powder ash E of about 400°C is formed, which is sent to the fuel preheating section 31 of the melting device 3 to be preheated to 950°C; then, the preheated fine powder ash F enters the melting zone 322 in the high-temperature melting section 32 through the swirl nozzle 321 and the operating temperature is 1700°C (higher than the ash melting temperature); at the same time, it passes through the swirl nozzle 321 to the melting zone 322 feeds an appropriate amount of normal temperature pure oxygen G (preheated fine powder ash F and normal temperature pure oxygen G are not mixed in the swirl nozzle). The preheated fine powder ash F is burned and melted in a high-temperature oxidizing atmosphere, so that the carbon with poor reactivity contained in it fully reacts with pure oxygen to form a low N ₂ , low O ₂ , and rich CO ₂ carbon-rich high temperature at 1700°C. Gas H1 and high temperature slag H2. The carbon-rich high-temperature gas H1 carries a small amount of high-temperature fly ash and high-temperature slag H2, and returns to the circulating fluidized bed gas through the melting product inlet of the reduction zone or the transition zone between the oxidation zone and the reduction zone set on the gasifier hearth 10 Furnace 1, carbon-rich high-temperature gas H1, on the one hand, supplements heat for the gasification reaction in the circulating fluidized bed coal gasification furnace 10; on the other hand, CO ₂ participates in the gasification reaction as a reactant, thereby effectively increasing the total carbon of the system Conversion rate and effective gas composition; the high-temperature slag H2 at 1700°C and the low-temperature carbon-containing solid material at 950°C in the gasifier hearth 10 adhere to each other to form solid particles that gradually increase in volume. It falls to the lower part of the gasifier, and finally exits the system in the form of bottom slag L. In the above process, the high temperature of the high-temperature slag H2 promotes the gasification reaction, making full use of the sensible heat of the slag; the carbon in the slag continues to react with the surrounding gas phase reactants during the slag falling process, increasing this part The residence time of carbon in the furnace of the gasifier is improved, thereby improving the carbon conversion rate of the circulating fluidized bed coal gasifier.

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

Claims (21)

1. a kind of circulation fluidized bed coal gasifying method with fine ash loopback, comprises the following steps：

A) coal (B1) and gasifying agent (A) are passed through circulation fluidized bed coal gasifying stove (1) and enter promoting the circulation of qi Change reaction, generation coal gas (C) and gasification fine ash (D)；

B) coal gas (C) is separated with gasification fine ash (D)；

C) the gasification fine ash (D) after separation is collected；

D) step c) the gasification fine ash (D) obtained and oxidant (G) are sent into melting plant (3)：

E) rich carbon high-temp gas (H1) and high-temperature slag (H2) are generated by means of melting plant；And

F) rich carbon high-temp gas (H1) and high-temperature slag (H2) are transmitted back to circulation fluidized bed coal gasifying In the gasification furnace burner hearth (10) of stove (1).

2. the circulation fluidized bed coal gasifying method according to claim 1 with fine ash loopback, its It is characterised by, also comprises the following steps：

Using high-temperature slag (H2) viscosity, gasification fine ash (D) is set to be changed into bottom ash (L) Sink to the bottom of the gasification furnace burner hearth (10) of circulation fluidized bed coal gasifying stove (1)；And

Discharge bottom ash (L).

3. the circulation fluidized bed coal gasifying method according to claim 1 with fine ash loopback, its It is characterised by：

Also include fine coal (B2) sending into melting plant (3) in step d).

4. the circulation fluidized bed coal gasifying method according to claim 1 with fine ash loopback, its It is characterised by：

In step e), by adjust oxidant (G) composition and its with gasification fine ash (D) Ratio, control oxidant (G) with gasification fine ash (D) reaction temperature, make the richness of generation The temperature t of carbon high-temp gas (H1) and high-temperature slag (H2) meets t₂-50℃≤t≤t₂+ 250 DEG C, its Middle t2 is the softening temperature of the ash content of gasification fine ash (D).

5. the circulation fluidized bed coal gasifying method according to claim 1 with fine ash loopback, its It is characterised by：

In step d), gasification fine ash (D) is first in the fuel preheating section (31) of melting plant (3) In be preheated to after 800 DEG C~950 DEG C, enter back into melting plant (3) high-temperature fusion section (32)； Wherein, the oxidant (G) is admitted in the high-temperature fusion of melting plant (3) section (32).

6. the circulation fluidized bed coal gasifying method according to claim 3 with fine ash loopback, its It is characterised by：

In step d), gasification fine ash (D) and fine coal (B2) are first in melting plant (3) It is preheated in fuel preheating section (31) after 800 DEG C~950 DEG C, enters back into the height of melting plant (3) Warm melt zone (32)；Wherein, the oxidant (G) is admitted to the high temperature melting of melting plant (3) Melt in section (32).

7. the circulation fluidized bed coal gasifying method according to claim 1 with fine ash loopback, its It is characterised by：

Step b) is specially the separator and/or dedusting using circulation fluidized bed coal gasifying stove (1) Device (15) separates coal gas (C) with gasification fine ash (D), and coal gas (C) is brought out.

8. the circulation fluidized bed coal gasifying method according to claim 7 with fine ash loopback, its It is characterised by：

Separator for separating coal gas (C) and gasification fine ash (D) is two-stage or more level Separator.

9. the circulation fluidized bed coal gasifying method according to claim 1 with fine ash loopback, its It is characterised by：

Rich carbon high-temp gas (H1) is transmitted back to the reducing zone of gasification furnace burner hearth (10), or zoneofoxidation Transition region between reducing zone.

10. a kind of circulation fluidized bed coal gasifying device with fine ash loopback, including recirculating fluidized bed coal Gasification furnace (1) and melting plant (3), it is characterised in that：

Circulation fluidized bed coal gasifying stove (1) have coal filling hole, gasification agent inlet, molten product import, Gas exit and one or more gasification fine ash outlets, the circulation fluidized bed coal gasifying stove (1) gasification furnace burner hearth (10) and separator are included；

There is melting plant (3) oxidant inlet and molten product to export, and melting plant (3) Connected with the gasification fine ash outlet, melting plant (3) is exported with circulating by molten product Fluidized bed coal gasifier (1) is connected, for the rich carbon high-temp gas (H1) that produces melting process and High-temperature slag (H2) is transmitted back to gasification furnace burner hearth (10).

11. the circulation fluidized bed coal gasifying device according to claim 10 with fine ash loopback, It is characterized in that：

The gasification furnace burner hearth (10) of the circulation fluidized bed coal gasifying stove (1), which has, is arranged on gasification The slag-drip opening of the bottom of stove burner hearth (10), the bottom of gasification furnace burner hearth (10) is sunk to for discharging Bottom ash (L).

12. the circulation fluidized bed coal gasifying device according to claim 10 with fine ash loopback, It is characterized in that：

The melting plant (3) also connects with fine coal entrance.

13. the circulation fluidized bed coal gasifying device according to claim 10 with fine ash loopback, It is characterized in that：

Melting plant (3) is made up of fuel preheating section (31) and high-temperature fusion section (32), described Gasification fine ash outlet is connected with fuel preheating section (31), and the oxidant inlet is arranged on In high-temperature fusion section (32).

14. the circulation fluidized bed coal gasifying device according to claim 12 with fine ash loopback, It is characterized in that：

Melting plant (3) is made up of fuel preheating section (31) and high-temperature fusion section (32), described Gasification fine ash outlet and the fine coal entrance are connected with fuel preheating section (31), and the oxygen Agent entrance is arranged in high-temperature fusion section (32).

15. the circulation fluidized bed coal gasifying device according to claim 10 with fine ash loopback, It is characterized in that：

The separator is the separator of two-stage or more level.

16. the circulation fluidized bed coal gasifying device according to claim 10 with fine ash loopback, It is characterized in that：

The circulation fluidized bed coal gasifying stove (1) also includes returning charge valve (12), and at least a portion is circulated Material returns to the gasification furnace burner hearth (10) of circulation fluidized bed coal gasifying stove (1) by returning charge valve (12).

17. the circulation fluidized bed coal gasifying device according to claim 16 with fine ash loopback, It is characterized in that：

The circulation fluidized bed coal gasifying stove (1) also includes cinder catcher (2), at least partially by dividing The gasification fine ash (D1) separated from device is admitted to cinder catcher (2), the melting plant (3) Connected by cinder catcher (2) with the gasification fine ash outlet.

18. the circulation fluidized bed coal gasifying device according to claim 17 with fine ash loopback, It is characterized in that：

The circulation fluidized bed coal gasifying stove (1) also includes deduster (15), at least partially by dividing The gasification fine ash (D1) separated from device and the gasification fine ash (D2) trapped by deduster (15) Cinder catcher (2) is admitted to, the melting plant (3) passes through cinder catcher (2) and the gasification fine powder Grey outlet connection.

19. the circulation fluidized bed coal gasifying device according to claim 18 with fine ash loopback, It is characterized in that：

The separator includes the first order cyclone separator (11) and second level whirlwind being sequentially connected Separator (13), the deduster (15) is sack cleaner；Returning charge valve (12) into and out of The solid circulation material outlet and gasification furnace burner hearth (10) of mouth respectively with first order cyclone separator (11) Returning charge mouth communicate, the solid outlet of second level cyclone separator (13) is used as gasification fine ash discharge Mouth is connected with the import of cinder catcher (2), and the ash discharging hole of the sack cleaner is used as gasification fine ash Outlet is connected with the import of cinder catcher (2).

20. the circulation fluidized bed coal gasifying device according to claim 10 with fine ash loopback, It is characterized in that：

The molten product import is arranged on the reducing zone of gasification furnace burner hearth (10), or zoneofoxidation with Transition region between reducing zone.

21. the circulation fluidized bed coal gasifying with fine ash loopback according to claim 13 or 14 Device, it is characterised in that：

High-temperature fusion section (32) includes swirl nozzle (321) and melting zone (322), wherein eddy flow Nozzle (321) is connected with fuel preheating section (31), and the oxidant inlet is arranged on swirl nozzle (321) on, melting zone (322) is provided with the molten product outlet.