CN109439369B - A coal-based chemical chain gasification method - Google Patents

Abstract

The embodiment of the invention discloses a coal-based chemical chain gasification method, which relates to the technical field of coal gasification. Improve syngas selectivity. The coal-based chemical chain gasification method includes adding coal, an oxygen carrier containing tungsten iron ore and a gasification agent into a gasification reactor, so that the coal, the oxygen carrier and the gasification agent undergo a gasification reaction to generate synthetic Gas-phase products and solid-phase products containing reduced oxygen carriers; at least a part of the solid-phase products are sent to a regeneration reactor for oxidation treatment to obtain oxidized oxygen carriers; the oxidized oxygen carriers are returned to the gasification reaction for the gasification reaction. The coal-based chemical chain gasification method provided in the embodiment of the present invention is suitable for a coal gasification process.

Description

A coal-based chemical chain gasification method

technical field

The invention relates to the technical field of coal gasification, in particular to a carbon-based chemical chain gasification method.

Background technique

With the continuous development of science and technology, relevant technicians have proposed a novel chemical chain gasification technology that can utilize solid fuels cleanly and efficiently. The chemical chain gasification technology refers to adding metal oxides to solid fuels to utilize Metal oxides are used as oxygen carriers, so that in the process of fuel gasification, the lattice oxygen in the oxygen carrier can be used to replace molecular oxygen, so as to provide the solid fuel with the oxygen required for fuel gasification, and by controlling the lattice oxygen and the ratio of solid fuel to obtain the target product. For example, the target product to be obtained by the coal-based chemical chain gasification technology is a synthesis gas including CO (carbon monoxide) and H ₂ (hydrogen).

However, at present, when coal-based chemical chain gasification technology is used for solid fuel gasification to obtain target products, it often occurs that the oxygen content supplied by metal or non-metal oxides is relatively high, and in this case, it is easy to cause CO and H ₂ is converted into CO ₂ (carbon dioxide) and H ₂ O (water), respectively, which makes the content of effective components in the obtained synthesis gas (ie, the content of CO and H ₂ ) lower, and the selectivity of synthesis gas is higher Difference.

SUMMARY OF THE INVENTION

The purpose of the embodiments of the present invention is to provide a coal-based chemical chain gasification method. By expanding the temperature range of oxygen supply by the oxygen carrier, the oxygen supply can be uniformly dispersed for the gasification of coal in a larger temperature range, so as to improve the efficiency of synthesis gas. Optional.

To achieve the above purpose, the embodiments of the present invention provide the following technical solutions:

The embodiment of the present invention provides a coal-based chemical chain gasification method, which includes: adding coal, an oxygen carrier including tungsten iron ore and a gasification agent into a gasification reactor, so that the coal, the oxygen carrier and the gasification agent are generated gasification reaction, generating a gas-phase product containing synthesis gas and a solid-phase product containing a reduced oxygen carrier; at least a part of the solid-phase product is transported to a regeneration reactor for oxidation treatment to obtain an oxidized oxygen carrier; the oxidized oxygen carrier is The oxygen is returned to the gasification reactor for gasification reaction.

Optionally, the above coal-based chemical chain gasification method further includes: extracting a part of solid phase products from the gasification reactor, and separating tungsten and tungsten oxides from the extracted solid phase products.

Optionally, the mass of the recovered solid-phase product accounts for 2% to 20% of the total mass of the solid-phase product generated in the gasification reactor.

Optionally, the temperature in the above-mentioned gasification reactor is 700-850°C.

Optionally, when the oxidized oxygen carrier is returned to the gasification reactor, the coal, the tungsten iron ore and the gasification agent are continuously added into the gasification reactor.

Optionally, the mass ratio of the tungsten iron ore added to the gasification reactor to the oxidized oxygen carrier returned to the gasification reactor is 1:15-1:5.

Optionally, the mass ratio of carbon in the coal to the oxygen carrier is 1:25 to 1:5.

Optionally, the temperature in the above-mentioned regeneration reactor is 800-1100°C.

Optionally, the gasification agent includes superheated steam, and the mass ratio of the gasification agent to carbon in the coal is 1:5 to 2:1.

Optionally, the particle size range of the coal is the same as the particle size range of the oxygen carrier.

In the coal-based chemical chain gasification method provided by the embodiment of the present invention, an oxygen carrier containing tungsten iron ore is added to the gasification reactor, so as to utilize the main component FeWO ₄ (ferrous tungstate) in the iron tungsten ore as The coal in the gasification reactor provides the oxygen required for its gasification. Since the temperature range of FeWO ₄ releasing oxygen is large, it can release oxygen evenly dispersed in the large temperature range, which also makes FeWO ₄ enter the gas. Oxygen can be gradually released in the process of continuous heating after the chemical reactor, and the oxygen can gradually react with the coal, avoiding the problem of excessive oxidation of coal caused by the concentration of the temperature range in which the oxygen is released by the existing oxygen carrier. The content of CO and H ₂ in the synthesis gas obtained by the gasification reaction can be effectively increased, and the selectivity of the synthesis gas can be improved.

Description of drawings

The accompanying drawings described herein are used to provide further understanding of the embodiments of the present invention, and constitute a part of the embodiments of the present invention. The schematic embodiments and descriptions of the embodiments of the present invention are used to explain the embodiments of the present invention, and do not constitute an implementation of the present invention. Improper limitation of the example. In the attached image:

Fig. 1 is the schematic flow chart of a kind of coal-based chemical chain gasification method provided in the embodiment of the present invention;

FIG. 2 is a schematic diagram of the existence form of FeWO ₄ provided in the embodiment of the present invention at different temperatures.

Detailed ways

For ease of understanding, the technical solutions provided by the embodiments of the present invention are described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the proposed technical solution, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the embodiments of the present invention.

Referring to FIG. 1, an embodiment of the present invention provides a coal-based chemical chain gasification method, including:

Step S1: adding coal, an oxygen carrier containing tungsten iron ore, and a gasification agent into the gasification reactor, so that the coal, the oxygen carrier and the gasification agent undergo a gasification reaction to generate a gas-phase product containing synthesis gas and a reduced state product. The solid-phase product of the oxygen carrier.

Step S2: at least a part of the solid-phase product is transported to a regeneration reactor for oxidation treatment to obtain an oxygen carrier in an oxidized state.

Step S3: Return the oxidized oxygen carrier to the gasification reactor for gasification reaction.

It should be noted that the main component in the above-mentioned tungsten iron ore is FeWO ₄ , and the formation of iron tungsten ore after reduction reaction mainly includes Fe (iron), W (tungsten), WO ₂ (tungsten dioxide), FeO ( The reduced oxygen carrier of ferrous oxide) can be re-converted into FeWO ₄ after being oxidized in the regeneration reactor to form an oxidized oxygen carrier. Therefore, after the oxidized oxygen carrier is recycled back to the gasification reactor, the above-mentioned oxygen carrier containing tungsten iron ore also contains the oxidized oxygen carrier delivered from the regeneration reactor in addition to the tungsten iron ore.

The above-mentioned gasifying agent may be superheated steam. When using coal, oxygen carrier and gasification agent for gasification reaction, the generated products include gas-phase products and solid-phase products, wherein the gas-phase products include synthesis gas whose active components are CO and H ₂ , and the solid-phase products include coal gas Semi-coke, coal ash and other substances generated after calcination, as well as the reduced oxygen carrier generated after the oxygen carrier is reduced.

The gasification reactions that take place in the gasification reactor are shown in equations (1) to (3):

C+H ₂ O=CO+H ₂ (1)

C+CO ₂ =2CO (2)

CO+H ₂ +FeWO ₄ =CO ₂ +H ₂ O+Fe+WO ₂ (3)

When FeWO ₄ undergoes gasification reaction, its existing forms at different temperatures are shown in Figure 2. It can be seen from Figure 2 that when the temperature range of FeWO ₄ is below 600 °C, FeWO ₄ will release a small amount of oxygen, mainly in a relatively stable form including FeWO ₄ , FeO, WO ₂ and Fe _; When the temperature range is between 600 and 700 °C, FeWO ₄ will release more oxygen, and it mainly exists in a relatively stable form including FeWO ₄ , Fe, WO ₂ , FeO, and W; when the temperature range of FeWO ₄ is 800 °C When the temperature is higher than ℃, FeWO ₄ absorbs more energy, further releases oxygen, and mainly exists in a relatively stable form including Fe, W, WO ₂ and FeO.

It can be seen that in the larger temperature range shown in Figure 2, as the temperature continues to rise from low to high, the chemical bond between oxygen and metal elements in FeWO ₄ can gradually absorb energy, and When the absorbed energy reaches the bond energy of the above-mentioned chemical bonds, the chemical bonds between oxygen and metal elements are broken, and oxygen is gradually released, which means that FeWO ₄ releases oxygen in a wide temperature range. The release of oxygen within the range is relatively uniform.

In the coal-based chemical chain gasification method provided by the embodiment of the present invention, an oxygen carrier including tungsten iron ore is added to the gasification reactor, so as to utilize FeWO ₄ , the main component in the tungsten iron ore, as the oxygen carrier in the gasification reactor. Coal provides the oxygen required for its gasification. Since FeWO ₄ releases oxygen in a wide temperature range, it can release oxygen evenly dispersed in a large temperature range, which makes FeWO ₄ continue to heat up after entering the gasification reactor. Oxygen can be gradually released in the process of gasification, and the oxygen can gradually react with the coal, avoiding the problem of excessive oxidation of coal caused by the concentrated temperature range of the oxygen released by the existing oxygen carrier, thereby effectively improving the gasification reaction. The content of CO and _H2 in the obtained syngas increases the selectivity of syngas.

Exemplarily, the hematite ore whose main component is Fe ₂ O ₃ and the tungsten iron ore whose main component is FeWO ₄ are used as oxygen carriers for illustration. In order to accurately reflect that the coal-based chemical chain gasification method provided in the embodiment of the present invention can effectively improve the selectivity of synthesis gas, the gasification reactions using hematite ore and tungsten iron ore respectively are carried out under the same reaction conditions of. Exemplarily, under the condition that the temperature in the gasification reactor is both 800° C. and the pressure in the gasification reactor is the same as 1 bar, the gasification reaction is carried out by using hematite and tungsten iron ore respectively, and the obtained synthetic The selectivity of gas is shown in Table 1 below.

Table 1

It can be seen from the above table 1 that under the conditions of different mass ratios of oxygen carrier and carbon in coal, the content of active components in the synthesis gas obtained by using tungsten iron ore as the oxygen carrier is higher than The content of active components in the synthesis gas obtained by using hematite as the oxygen carrier, that is, the selectivity of the synthesis gas obtained by using tungsten iron ore as the oxygen carrier is higher than that obtained by using hematite as the oxygen carrier The selectivity of the synthesis gas is high, which means that the coal-based chemical chain gasification method provided in the embodiment of the present invention can effectively improve the selectivity of the synthesis gas.

In some embodiments, when the iron tungsten ore is selected as the oxygen carrier, the iron tungsten ore whose mass fraction of FeWO ₄ in the iron tungsten ore is greater than 80% is usually selected, and the iron tungsten ore with higher grade is used as the carrier. The oxygen carrier can improve the oxygen carrying capacity of the oxygen carrier per unit mass. During the gasification reaction, the oxygen carrier can provide more coal with the oxygen required for its gasification, so that more coal can be gasified. , which can effectively improve the yield of synthesis gas in the gasification reaction.

In order to efficiently perform the gasification reaction in the gasification reactor, in some embodiments, the particle size range of the coal is the same as the particle size range of the oxygen carrier. Exemplarily, the particle size of the coal is in the range of 400-800 μm, and the particle size of the oxygen carrier is also in the range of 400-800 μm, so that after the coal and the oxygen carrier with the same particle size range are added to the gasification reactor, the The coal and the oxygen carrier are fully and uniformly mixed under the action of the gasification agent, so that the oxygen released by the oxygen carrier can be evenly distributed around the coal and gasify with the coal uniformly, which can effectively improve the gasification. The content of active ingredients in the reaction.

It can be understood that the gasification agent usually includes superheated steam. In this case, the superheated steam not only acts as a fluidizing medium to enable sufficient and uniform mixing of coal and oxygen carrier, but also participates in the gasification reaction as a reactant to provide synthesis. The required H (hydrogen) in the gas. In order to avoid that the quality of the gasification agent added to the gasification reactor is low, which makes it difficult to mix the coal and the oxygen carrier well, in some embodiments, the gasification agent added to the gasification reactor is the same as the gasification agent added to the gasification reactor. The mass ratio of carbon in the coal is generally 1:5 to 2:1, which not only enables the coal and the oxygen carrier to be evenly mixed, but also forms a better hydrogen-to-carbon ratio, that is, it can generate a better carbon-hydrogen ratio. Syngas. Of course, the mass ratio of the gasification agent to carbon in the coal can also be set by itself according to actual needs, which is not limited in this embodiment.

It is worth mentioning that the temperature in the gasification reactor can be set to 700-850°C. Referring to Figure 2, when the temperature range is 700-850°C, FeWO ₄ mainly exists in the form of Fe, WO ₂ , FeO, and W, and the components in the above-mentioned forms have gradually become stable, and when When the temperature is higher than 850°C, FeWO ₄ mainly exists in the form of Fe, WO ₂ , FeO, and W, and the components in this form are basically unchanged, that is, when the temperature is higher than 850° C. FeWO ₄ Oxygen is basically no longer released. Therefore, when the temperature in the gasification reactor is set to a temperature range of 700-850 °C, it can not only ensure that the carbon in the coal can be gasified well, but also can make full use of FeWO ₄ , so that the oxygen in FeWO ₄ can be released more completely.

It can be understood that, in step S2, when the solid-phase product is sent to the regeneration reactor for oxidation treatment to obtain an oxidized oxygen carrier, all solid-phase products can be sent to the regeneration reactor for oxidation treatment, or A part of the solid-phase product in the solid-phase product is sent to the regeneration reactor for oxidation treatment, which is not limited in the embodiment of the present invention.

When the oxidation treatment is carried out in the regeneration reactor, the pressure in the regeneration reactor can be kept in the range of 0.1-1Mpa, and air is used as the gasification agent for the oxidation treatment. The oxygen body undergoes redox reaction with oxygen in the air and is converted into FeWO ₄ , the oxidized oxygen carrier; the semi-coke in the solid phase product burns with the oxygen in the air to provide heat for the oxidation of the reduced oxygen carrier.

The oxidation reaction of the reduced oxygen carrier in the regeneration reactor is shown in equation (4):

Fe+W+2WO ₂ +2FeO+3O ₂ =3FeWO ₄ (4)

It should be noted that, in order to ensure that the reduced oxygen carrier can be stably converted into an oxidized oxygen carrier during the oxidation process of the reduced oxygen carrier, the temperature in the regeneration reactor can be set to 800-1100 °C, so that When the reduced oxygen carrier is oxidized, it can avoid the conversion of Fe and FeO in the reduced oxygen carrier into Fe ₂ O ₃ due to the high temperature in the regeneration reactor, and ensure that the reduced oxygen carrier is The oxidized oxygen carrier obtained after the oxidation treatment is still FeWO ₄ , which can effectively ensure that the oxidized oxygen carrier formed by the conversion of the reduced oxygen carrier can still balance the oxygen supply in the gasification reaction and improve the selection of syngas. sex.

In some embodiments, the temperature in the gasification reactor is lower than the temperature in the regeneration reactor, which also makes the temperature of the solid phase product in the gasification reactor lower than the temperature in the regeneration reactor. After being transported into the regeneration reactor, the solid phase product also needs to be heated up. In order to make full use of the heat released by the reaction in the regeneration reactor, in some embodiments, the heat released by the combustion of the semi-coke in the regeneration reactor can be used to increase the temperature of the solid-phase product, which can reduce the waste of heat, Avoid the increase in economic cost caused by using other heating devices to heat the solid phase product.

It is worth mentioning that when a part of the solid-phase products in the solid-phase product is transported to the regeneration reactor for oxidation treatment in step S2, the chemical chain gasification method provided in the embodiment of the present invention further includes step S2': from gas Part of the solid phase product is extracted in the chemical reactor, and tungsten and tungsten oxide are separated from the extracted solid phase product.

The solid phase products generated in the gasification reactor mainly include Fe, W, WO ₂ , FeO, semi-coke and coal ash, among which the above-mentioned W and WO ₂ have high added value, so that when combining W and WO ₂ After being separated from the solid-phase product, W and WO ₂ can be used to improve the economic benefits brought by the methods provided in the embodiments of the present invention, and effectively reduce the economic costs required by the methods.

Since the densities of W and WO ₂ in the above-mentioned substances are relatively high relative to those of Fe, FeO, semi-coke, and coal ash, etc., when the above-mentioned substances are separated, they can be separated by air separation or gravity sieving. In this way, Fe, FeO, semi-coke and coal ash with lower densities are separated from W and WO ₂ with higher densities to obtain W and WO ₂ with higher densities and higher added value. In addition, the separated W and WO ₂ may be mixed with a small amount of Fe, FeO, semi-coke and coal ash, etc. Therefore, W and WO ₂ can be further separated by separation methods such as cooling or magnetic separation to obtain Higher purity W and WO ₂ .

It can be understood that the solid-phase product carries heat, and in order to avoid taking more heat from the gasification reactor when the solid-phase product is extracted from the gasification reactor, in some embodiments, the The mass of the extracted solid-phase product can account for 2% to 20% of the total mass of the solid-phase product generated in the gasification reactor, so that after the solid-phase product is extracted from the gasification reactor, the gasification can be ensured. There is still sufficient heat in the reactor to ensure that the gasification reaction in the gasification reactor can still be carried out well.

It should be noted that, after the reduced oxygen carrier is converted into the oxidized oxygen carrier, the oxidized oxygen carrier needs to be returned to the gasification reactor to continue the gasification reaction using the oxidized oxygen carrier.

When the reduced oxygen carrier is oxidized in the regeneration reactor, it will absorb more heat, so that the oxidized oxygen carrier will carry more heat, so that the oxidized oxygen carrier will be returned to the gasification state. After the reactor, not only can the oxidized oxygen carrier be used to continue to provide the oxygen required for gasification for the gasification reaction in the gasification reactor, but also the heat carried by it can be released in the gasification reactor. A good heat cycle is formed between the chemical reactor and the regeneration reactor.

Since the oxygen carrier is lost when it circulates between the gasification reactor and the regeneration reactor, in order to make up for the loss of the oxygen carrier, when the oxidized oxygen carrier is returned to the gasification reactor, it will also contribute to the gasification reaction. The tungsten iron ore is added to the reactor, and the mass ratio of the tungsten iron ore added to the gasification reactor to the oxidized oxygen carrier returned to the gasification reactor can be set to be 1:15 to 1:5, so that While realizing the recycling of the oxidized oxygen carrier, it can also ensure that the oxygen released by the oxygen carrier added to the gasification reactor can still be gasified with the coal in the gasification reactor, resulting in a relatively high content of active components. high syngas.

In some embodiments, when coal, a gasification agent, and an oxygen carrier comprising tungsten iron ore and an oxidized oxygen carrier are added to the gasification reactor, the carbon in the added coal and the added oxygen carrier The mass ratio can be set to 1:25 ~ 1:5. In this way, the carbon in the coal can be gasified uniformly with the oxygen released by the oxygen carrier, so as to avoid insufficient coal gasification caused by the high carbon content in the coal, or low carbon content in the coal causing the carbon Over-oxidized, reducing the content of active ingredients in the syngas.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention. should be included within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (9)

1. A coal-based chemical looping gasification method is characterized by comprising the following steps:

adding coal, an oxygen carrier containing tungstoferrite and a gasifying agent into a gasification reactor, and carrying out gasification reaction on the coal, the oxygen carrier and the gasifying agent to generate a gas-phase product containing synthesis gas and a solid-phase product containing a reduced-state oxygen carrier;

conveying at least one part of the solid-phase product to a regeneration reactor for oxidation treatment to obtain an oxidation state oxygen carrier;

returning the oxidized oxygen carrier to the gasification reactor for the gasification reaction;

wherein the temperature in the gasification reactor is 700-850 ℃.

2. The coal-based chemical looping gasification method according to claim 1, characterized by further comprising: withdrawing a portion of the solid phase product from the gasification reactor, and separating tungsten and tungsten oxides from the withdrawn solid phase product.

3. The coal-based chemical looping gasification method according to claim 2, characterized in that the mass of the solid phase product recovered accounts for 2-20% of the total mass of the solid phase product generated in the gasification reactor.

4. The coal-based chemical looping gasification method according to claim 1, characterized in that the coal, the wustite ore and the gasification agent are continuously added into the gasification reactor while the oxidation state oxygen carrier is returned to the gasification reactor.

5. The coal-based chemical looping gasification method according to claim 4, wherein the mass ratio of the wustite ore added to the gasification reactor to the oxidation state oxygen carrier returned to the gasification reactor is 1:15 to 1: 5.

6. The coal-based chemical looping gasification method according to claim 1, wherein the mass ratio of carbon in the coal to the oxygen carrier is 1: 25-1: 5.

7. The coal-based chemical looping gasification method according to claim 1, wherein the temperature in the regeneration reactor is 800-1100 ℃.

8. The coal-based chemical looping gasification method according to claim 1, wherein the gasifying agent comprises superheated steam, and the mass ratio of the gasifying agent to carbon in the coal is 1: 5-2: 1.

9. The coal-based chemical looping gasification method according to claim 1, characterized in that the particle size range of the coal is the same as the particle size range of the oxygen carrier.

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