WO2011029278A1

WO2011029278A1 - Catalyst recycling method in process of coal gasification

Info

Publication number: WO2011029278A1
Application number: PCT/CN2010/001398
Authority: WO
Inventors: 毕继诚; 张�荣; 孙志强; 陈意心; 李金来; 甘中学
Original assignee: 新奥科技发展有限公司
Priority date: 2009-09-14
Filing date: 2010-09-13
Publication date: 2011-03-17
Also published as: CN102021036A; CN102021036B

Abstract

A catalyst recycling method in the process of coal gasification in a single reactor is disclosed. The method comprises the following steps: a) coal contacts with a counter flow of gas product and gaseous catalyst from the step b) in a moderate temperature section of the reactor, where the catalyst vapor condenses on the coal and catalyzes reaction between the coal and the gas product from the step b), to obtain a target gas product and solid residue; b) the catalyst and solid residue enter into a high temperature section of the reactor, where the solid residue reacts with the gas oxidant in the high temperature section to obtain the gas product, and in the mean time the catalyst is volatilized into the gaseous catalyst under high temperature so as to be separated from the solid residue and returns to the moderate temperature section of the reactor along with the gas product to perform step a). In a preferred embodiment, the method further comprises step c): a part of the gaseous catalyst, which leaves the moderate temperature section along with the target gas product, enters into a low temperature section of the reactor and condenses on the coal powder completely therein.

Description

Catalyst recycling method in coal gasification process

The present invention relates to a process for recycling a catalyst, and more particularly to a process for recycling a catalyst in the gasification process of coal.

Background technique

With the increasing shortage of oil and natural gas resources in the world, coal-based energy conversion technology represented by coal gasification has become an increasingly important focus of countries around the world. In particular, China is rich in coal and oil, and the geographical distribution of coal resources is uneven. Developing efficient and clean coal conversion technology has long-term significance for safeguarding national energy security and economic development. Among them, methane has become one of the targets of many coal gasification industrialization technologies due to its cleanliness, high energy density and easy transportation. The current methanation technology can be roughly divided into indirect method and direct method. The indirect method refers to the gasification of coal into products such as H ₂ and CO by using existing mature technologies (such as gas stream coal gasification), and then synthesizing silane by syngas under the action of a catalyst. The direct method is to directly vaporize coal into methane under the action of a catalyst. Compared with the indirect method, the direct method has the advantages of simple process and high efficiency of cold gas. Current direct decaneization techniques are typically operated using a fluidized bed. Exxon, with the support of the US Department of Energy, conducted a large number of researches on coal catalytic gasification in the 1970s and 1980s. The general process is to fluidize superheated steam and coal mixed with catalyst. The gasification reaction is carried out. The catalyst and the coal may be mechanically mixed or may be mixed by a dipping method or the like. Most of the catalysts used are alkali metal catalysts such as potassium carbonate, sodium carbonate, or polybasic alkali metal composite catalysts such as potassium carbonate-sodium carbonate binary catalyst, or potassium carbonate-sodium carbonate-lithium carbonate three-way catalyst. A catalytic gasification process is disclosed in US 4,094,650. The optimum temperature and pressure range for coal catalytic gasification is 700 and 34 a tm, using monobasic potassium carbonate as a catalyst. In addition to coal, petroleum coke and other materials containing high fixed carbon can also be used in similar processes. For example, US2007/0083072 proposes a process stream for catalytic gasification of petroleum slag. The process describes the entire process and optimizes and utilizes the energy of the system.

In order to increase the yield of decane, the amount of the catalyst used in the prior art is maintained at 5 to 15 wt%. Due to the large amount of catalyst used and high cost, it is necessary to add a separate catalyst recovery process in addition to the catalytic reaction process to separate and recycle the catalyst and ash, residual coke, and the like. However, the separation of the coal ash residue and the catalyst after gasification is difficult because the coal ash residue and the catalyst are present in a form of tightly bound solid solution after cooling. Patent EP0090109 The recovery of readily soluble alkali metal ions is achieved with an aqueous solution of sulfurous acid.

EP 0 098 429 proposes a process for recovering an alkali metal catalyst with water or an aqueous solution. The coal ash residue contains minerals such as silicate. Under the gasification reaction conditions, it is easy to vitrify with alkali metal catalyst to form stable and insoluble alkali metal silicate. US4365975 uses electromagnetic radiation to recover water-insoluble alkali. A metal salt such as potassium aluminum silicate or the like. CA1130230 recovers alkali metal components by replacing the potassium ions in the water-insoluble potassium salt with an aqueous solution containing calcium ions or magnesium ions by ion exchange reaction. US 2007/008307 proposes the use of an acidic water recovery catalyst in the system and the like. A common disadvantage of these catalyst recovery processes is that the recovery of the catalyst is carried out in a separate separation and recovery unit outside of the gasification reactor, and then the recovered catalyst is recycled back to the reactor for reuse, which not only increases process complexity. Moreover, it greatly increases equipment investment costs and production operation costs, and hinders further large-scale industrialization of coal catalytic gasification technology.

The invention adopts a novel catalyst circulation method, so that the catalyst recovery and the catalytic gasification reaction of coal are carried out in a single reactor, thereby eliminating the disadvantages of the above existing processes, not only the process is simple, but also the investment of the separation and recovery equipment is saved. And operating costs. Summary of invention

The invention relates to a method for recycling a catalyst in a single reactor during gasification of coal, comprising the steps of: a contacting the coal with the gaseous product from step b and the catalyst vapor in the intermediate temperature section of the reactor, the catalyst vapor condensing on the coal and catalyzing the reaction between the coal and the gaseous product from step b, producing a target gas reaction product and solid residue ;

b The catalyst enters the high temperature section of the reactor together with the solid residue, and the solid residue reacts with the gaseous oxidant passing through the section to form a gas product in the high temperature section, and the catalyst is vaporized at a high temperature into a catalyst vapor to be separated from the solid residue, and The gaseous product is returned to the intermediate temperature section of the reactor for step a.

In a preferred embodiment of the present invention, in addition to the above steps, the method of the present invention further comprises passing a portion of the catalyst vapor leaving the intermediate temperature range with the target gas reaction product into the low temperature section of the reactor where it is completely condensed in the coal. Step c on the powder. DRAWINGS

Figure 1 is a schematic illustration of the process of the invention. The drawings are merely illustrative and are not intended to limit the invention in any way. Detailed description of the invention

The catalyst recycling process of the present invention is carried out in a multistage reactor (also referred to as a multistage gasifier). The basic principle is to divide the reactor into two or more gasification sections. The gasification of the catalyst in the high temperature section (separation from solid residue such as coal ash and coal char) is achieved by using different temperatures in each section, and the middle temperature section is condensed. The pulverized coal plays a catalytic role, and the recycling of the catalyst in the reactor is realized by means of an overall approximate relative reverse flow between the gas and solid.

In the method of the present invention, the reactor is placed vertically or obliquely at an angle sufficient to cause the coal to move downward under its own weight. Wherein the reactor is divided into at least two sections from top to bottom, namely a medium temperature section and a high temperature section. Optionally, the reactor can be divided into three sections from top to bottom, namely a low temperature section, a medium temperature section and a high temperature section. Where the high temperature The temperature of the section is 900-1500 Ό, the temperature in the middle temperature section is 600-900, and the temperature in the low temperature section is 600 or less.

The coal in the process of the invention is selected from the group consisting of bituminous coal, anthracite, lignite, or mixtures thereof.

In the startup step prior to the process of the invention, the gaseous oxidant is fed from the high temperature section of the reactor. Coal and catalyst can be fed in a variety of ways, for example: In a two-stage reactor containing only the intermediate temperature section and the high temperature section, all of the coal is fed in the intermediate temperature section of the reactor, or a portion of the coal is in the intermediate temperature section of the reactor. Feeding while another part of the coal is fed in the high temperature section of the reactor, and the catalyst can be fed in the high temperature section and/or the intermediate temperature section of the reactor; in a three-stage reactor comprising a low temperature section, a medium temperature section and a high temperature section, At least a portion of the coal is required to be fed in the low temperature section of the reactor, preferably all of the coal is fed from the low temperature section of the reactor, and the catalyst is fed from any one or several of the high temperature section, the intermediate temperature section or the low temperature section of the reactor. . In a preferred embodiment of the invention, a portion of the coal is fed in the low temperature section of the reactor and the remaining coal is fed from the high temperature section and/or the intermediate temperature section. The coal and catalyst may be fed separately by respective feed equipment or may be mixed as a mixture of the two. In the reactor, the gas moves from the bottom up and the coal moves from the top to the bottom, and the two move in the reactor in a countercurrent contact as a whole. Regardless of how the coal and catalyst are fed, they will eventually come into contact with each other at the intermediate temperature of the reactor while contacting the gas and starting the reaction. Once the reaction has begun, the recycling of the catalyst of the present invention in the reactor is initiated, i.e., the steps a and b of the present invention are repeated, or steps a, b and c of the present invention are repeated.

In step a of the present invention, the coal is contacted with the gaseous product from step b and the catalyst vapor at the intermediate temperature stage of the reactor, the catalyst vapor is condensed on the coal and catalyzes the reaction between the coal and the gaseous product from step b, producing a target Gas reaction product and solid residue. The intermediate temperature section can also be referred to as a medium temperature catalytic gasification section. The temperature of the intermediate temperature section is generated by the endothermic heat of the coal itself and the reaction of the coal with the gaseous reaction product from step b to form decane or Syngas is used to absorb heat and/or heat from the reactor to maintain. Due to the endothermic heat of the coal itself and the endothermic heat of the gasification reaction and optionally the heat of the reactor, the temperature of the gaseous product and catalyst vapor from step b is rapidly reduced, for example such that the temperature in the section is lower than the boiling point of the catalyst, so The catalyst vapor of step b is condensed on the coal powder and is in full contact with the coal powder. It should be pointed out here that, depending on the specific temperature of the medium temperature section and the type of catalyst, the catalyst vapor is condensed on the coal powder in the form of a liquid, or first condensed on the coal powder in the form of a liquid and then solidified into a solid attached to the coal powder. Above, or the catalyst vapor is directly condensed from the vapor state on the coal powder, the present invention does not make a fine distinction between the three forms, but is collectively referred to as the catalyst "condensation" on the solid, that is, the "condensation" referred to herein is a generalized It does not only include narrowly defined condensation from gas to liquid, but includes three forms as described above. The contact area of the catalyst with the coal powder is much larger than the contact area that can be achieved by conventional impregnation mixing methods. Therefore, in the intermediate temperature range, the coal reacts with the gas product from the step b under the action of the catalyst to generate the target gas reaction product and the solid residue, wherein the target gas reaction product may be methane or a synthesis gas containing hydrogen and carbon monoxide, depending on The specific type of catalyst employed. The target gas reaction product is further moved upward away from the intermediate temperature section. The solid residue is mainly unreacted residual carbon and ash, to which the already condensed catalyst is attached. The solid residue moves downward under the action of its own gravity to the high temperature section of the reactor to carry out step b.

In the step b of the present invention, the catalyst enters the high temperature section of the reactor together with the solid residue, and the solid residue reacts with the gaseous oxidant introduced into the section in the high temperature section to form a gas product, and the catalyst is vaporized therein to form a catalyst vapor to The solid residue is separated and returned to the intermediate temperature section of the reactor with the gaseous product to carry out step a. Wherein the gaseous oxidant is passed to the bottom and/or sides of the high temperature section selected from the group consisting of oxygen, air, water vapor or mixtures thereof. These gaseous oxidants undergo a vigorous oxidation reaction upon contact with the solid residue from step a at a high temperature to form a gaseous product containing at least one of C0, C0 ₂ and H ₂ . For example, when the gas oxidant is In the case of air or oxygen, the reaction produces CO and/or co ₂ ; when the gaseous oxidant is water vapor, the reaction produces H ₂ and CO and/or C0 ₂ , and excess water vapor is present; when the gaseous oxidant is oxygen and water vapor In the case of a mixture, the reaction produces 11 ₂ and CO and/or co ₂ . This severe oxidation reaction simultaneously releases a large amount of heat of reaction to maintain the high temperature in the high temperature zone. The catalyst is rapidly vaporized to a catalyst vapor at this temperature and separated from the solid residue, and moved upward together with the generated hot gas product to the intermediate temperature section to carry out step a. The solid residue continues to be oxidized or burned, and finally ash is formed, which exits the reactor from the bottom of the high temperature section. Since the violent oxidation reaction occurs in the high temperature section and the catalyst is vaporized, this section can also be referred to as a residue combustion/catalyst gasification section.

Optionally, there may be a low temperature section above the intermediate temperature section. As shown in FIG. 1, the temperature of the low temperature section is lower than the intermediate temperature section, for example, 600 or less, preferably 400 to 600 °C. If the low temperature section is not used, the target gas reaction product of step a leaves the intermediate temperature section and is further treated as a gas product by cooling, purification, etc.; if the reactor has a low temperature section in the middle temperature section, then The target gas reaction product can also be used to preheat the pulverized coal fed from the low temperature section to utilize the remaining heat to cause a partial pyrolysis reaction of the pulverized coal to form a part of decane, and then all the gaseous products leave the reactor. Cooling, purification, etc. are further processed as a gas product. In addition to the use of waste heat, another benefit of using the low temperature section is that in the mid-temperature range, there may be a small portion of the catalyst vapor that is not condensed due to short-circuiting of the gas stream or the catalyst vapor generated by re-gasification due to local overheating reacts with the target gas. The product leaves the intermediate temperature range, and the catalyst vapor can be completely condensed on the feed coal powder in the low temperature stage, thereby avoiding the loss of the catalyst and reducing the trouble of purifying the target gas reaction product. The preheated pulverized coal carries a catalyst condensed thereon and enters the intermediate temperature section for reaction under its own gravity.

The absolute pressure in the reactor of the present invention is generally from atmospheric pressure to 40 atmospheres, preferably from 10 to 40 atmospheres.

The catalyst used in the process of the invention is mainly an alkali metal salt or an alkaline earth metal a salt or an alkali metal hydroxide or an alkaline earth metal hydroxide such as a potassium salt, a sodium salt, a lithium salt or a calcium salt. Generally, the catalyst comprises one or more alkali metal carbonates or hydroxides thereof, such as potassium carbonate, sodium carbonate, lithium carbonate, cesium carbonate, calcium carbonate, or lithium hydroxide, sodium hydroxide, Potassium hydroxide, barium hydroxide, barium hydroxide, magnesium hydroxide, calcium hydroxide, etc., or a binary or multicomponent composition thereof, such as potassium carbonate-sodium carbonate-lithium carbonate, potassium carbonate-sodium carbonate-cesium carbonate, Potassium carbonate-calcium carbonate, potassium carbonate-sodium carbonate-calcium carbonate, and the like.

In view of the operation of the process of the present invention, a loss of a portion of the catalyst is inevitably caused. For example, the catalyst and the coal ash react to cause catalyst deactivation, so that fresh catalyst is periodically added during operation. The reactor is replenished with fresh catalyst at least at one of the high temperature zone, the intermediate temperature zone or the low temperature zone of the reactor. The fresh catalyst can be supplemented separately or supplemented with pulverized coal entering the reactor.

The method of the present invention has been described above by taking coal as an example, but it will be apparent to those skilled in the art that the method of the present invention can also be applied to a gasification process of a petroleum-rich material such as petroleum coke or biomass.

The advantages of the present invention are apparent. First, the recycling of the catalyst in a single reactor is achieved by condensation-gasification-condensation of the catalyst, which is a technique in which the catalyst is "in situ" separated and recycled, avoiding The disadvantages of a separate separation and recovery process are required in existing processes. Second, catalytic gasification and catalyst circulation are highly coupled in one reactor, reducing the total equipment investment. Again, for different catalyst combinations, the recycling of the hydrazine can be achieved by appropriately adjusting the temperature of the different sections of the reactor.

Claims

1. A method of recycling a catalyst in a single reactor during gasification of coal, comprising the following steps:

a contacting the coal with the gaseous product from step b and the catalyst vapor in the intermediate temperature section of the reactor, the catalyst vapor condensing on the coal and catalyzing the reaction between the coal and the gaseous product from step b, producing a target gas reaction product and solid residue ;

The method of claim 1 further comprising the step c of passing a portion of the catalyst vapor leaving the intermediate temperature section of the target gas reaction product into the low temperature section of the reactor where it is completely condensed on the coal powder.

The method according to claim 1 or 2, wherein the high temperature section temperature is 900-1500 ° C and the intermediate temperature section temperature is 600-900 °.

4. The method of claim 2 wherein said low temperature section temperature is below 600 。.

5. A process according to claim 1 wherein all of the coal is fed in the intermediate temperature section of the reactor or a portion of the coal is fed in the intermediate temperature section of the reactor and another portion of the coal is fed in the high temperature section of the reactor.

6. The method of claim 2 wherein at least a portion of the coal is fed at a low temperature stage of the reactor.

7. The method of claim 1 wherein the gaseous oxidant is selected from the group consisting of oxygen, air, water vapor, or mixtures thereof.

8. The method of claim 1 wherein between the solid residue and the oxidant The heat of reaction of the reaction that occurs is maintained at a high temperature in the high temperature section.

9. The method according to claim 1, wherein the gaseous product of step b comprises at least one of C0, C0 ₂ , H ₂ , H ₂ 0.

10. The method of claim 1 wherein the target gas reaction product is methane or syngas.

11. The method according to claim 1, wherein the temperature of the intermediate temperature section is maintained by the endothermic heat of the coal itself and the reaction of the coal with the gaseous reaction product from step b to form a decane or syngas to absorb heat and/or heat of the reactor. .

12. The method of claim 1 wherein the catalyst is fed at a high temperature and/or a medium temperature range of the reactor.

13. Process according to claim 2, wherein the catalyst is fed in the high temperature section and / or the intermediate temperature section and / or low temperature section of the reactor.

14. A process according to claim 1 or 2 wherein the reactor is replenished with fresh catalyst at least at one of the high temperature zone, the intermediate temperature zone or the low temperature zone of the reactor.

15. Process according to claim 1 or 2, wherein the catalyst and pulverized coal are fed separately to the reactor or mixed together to feed the reactor.

16. Process according to claim 1 or 2, wherein the catalyst is selected from one or more of an alkali metal or alkaline earth metal salt or an alkali metal hydroxide or an alkaline earth metal hydroxide.

17. Process according to claim 1 or 2, wherein the catalyst is selected from one or more of a potassium salt, a sodium salt, a lithium salt or a calcium salt.

18. The method according to claim 16, wherein the alkali metal salt is selected from the group consisting of potassium carbonate, sodium carbonate, lithium carbonate or cesium carbonate.

19. A method according to claim 1 or 2, wherein the coal is selected from the group consisting of bituminous coal, anthracite, lignite or mixtures thereof.

20. A method according to claim 1 or 2, wherein the coal is replaced with petroleum coke or biomass.

21. The method according to claim 1, wherein the reactor is divided into a medium temperature section and a high temperature section from top to bottom.

22. The method according to claim 2, wherein the reactor is divided into a low temperature section, a medium temperature section, and a high temperature section from top to bottom.

23. The method of claim 16 wherein said alkali metal hydroxide is selected from the group consisting of potassium hydroxide, lithium hydroxide, sodium hydroxide or barium hydroxide or a mixture thereof, said alkaline earth metal hydroxide being selected from the group consisting of hydroxides Bismuth, magnesium hydroxide or calcium hydroxide or a mixture thereof.