TW201304865A - Chemical looping combustion method applied with dual metal compound oxidation - Google Patents

Abstract

A chemical looping combustion method applied with dual metal compound oxidation includes the following steps: proceeding a combustion reaction of a fuel material with a dual metal compound oxidation in a first reactor to obtain a metal product; applying the metal product obtained in the first reactor to a second reactor, and the metal product reacting with the air in the second reactor to obtain the dual metal compound oxidation; and, applying the dual metal compound oxidation obtained in the second reactor to the first reactor. By the dual metal compound oxidation, the chemical looping process is provided with high oxidation rate and high reduction rate so as to increase the efficiency of the chemical looping combustion process.

Description

Chemical loop method using bimetal composite oxide

The present invention relates to a chemical loop method using a bimetallic composite oxide, and in particular, to a chemical loop method which increases the reaction rate of the chemical loop procedure and reduces the difficulty of designing a chemical loop procedure.

Although human science and technology have advanced by leaps and bounds in recent years, due to the excessive exploitation of resources and the pollution caused by industrialization, human beings have to look back at the impact of various technologies on the living environment. Environmental issues have therefore received the attention of countries around the world. In general, the development of human science and technology is closely related to the use of energy. Therefore, the environmental impact caused by various power plants and the development of green energy are quite important parts of various environmental issues.

Thermal power generation is the most widely used power generation method. It uses a fossil fuel such as coal, oil, natural gas to heat water to generate steam to drive the generator to output electricity. Compared with other power generation methods, the air pollution generated by thermal power generation is relatively serious. Since the thermal power generation uses a variety of fossil fuels to react with oxygen in the air in the reactor, the exhaust gas composition of the exhaust gas contains carbon dioxide. Carbon dioxide is generally considered to be a greenhouse gas causing greenhouse effect. At present, all countries in the world are working towards carbon dioxide emission reduction. In general, in addition to reducing the production of carbon dioxide, carbon dioxide emission reduction can also be achieved through storage or reuse. However, in addition to carbon dioxide, the exhaust gas emitted from thermal power plants contains pollutants such as nitrogen oxides. If the carbon dioxide emissions are to be reduced by means of sequestration and reuse, the above pollutants must be separated before proceeding. This separation procedure is quite energy intensive, and part of the power generation of the power plant must be supplied to this separation procedure, which is equivalent to reducing the power generation efficiency of the thermal power plant.

In the prior art, in order to solve the above problems, a chemical loop process using a metal oxygen carrier instead of air as a combustion aid has been proposed. The chemical loop process utilizes two fluidized bed reactors, a Fuel Reactor and an Air Reactor, to perform a reductive oxidation reaction to generate heat. In detail, in the combustion reactor, the fuel reacts with the metal carrier to generate a heat reaction, and the combustion reaction is a reduction reaction to the metal carrier, so that the metal carrier is reduced to a metal after combustion. Then, the reduced metal is sent to an air reactor for oxidation reaction with air or other gas capable of supplying oxygen atoms, and then a metal carrier is formed to be supplied to the combustion reactor for loop circulation.

Since the metal oxygen carrier of the chemical loop process provides the oxygen atom required for the combustion reaction, unlike the conventional method of supplying oxygen atoms by air in the conventional combustion reaction, the exhaust gas generated after combustion is condensed to remove the gas remaining after the water vapor. It is carbon dioxide with a content of up to 99%. Such a pure amount of carbon dioxide can be directly sealed or reused without going through a highly energy-consuming gas separation process. Therefore, the chemical loop process is beneficial to the reduction of carbon dioxide emissions from a thermal power plant, without wasting energy in separating gases. The process, in other words, energy efficiency is better.

In the chemical loop process, the metal oxygen-carrying system is usually used as a pure iron carrier and a pure nickel carrier. The pure iron carrier has a fast oxidation rate and a slow reduction rate, while the pure nickel carrier has a slow oxidation rate and a fast reduction rate. Due to the difference in the above redox rates, the two reaction times of the chemical loop process are asymmetrical, which makes the design of the chemical loop procedure quite difficult, which is disadvantageous for the application of the thermal power plant.

Accordingly, one aspect of the present invention is to provide a new type of chemical looping method to solve the problems of the prior art.

According to a specific embodiment, the chemical loop method of the present invention comprises the steps of: providing a bimetallic composite oxide in a first reactor; and reacting a bimetallic composite oxide with a fuel in a first reactor to produce a metal product And a gas; providing a metal product produced in the first reactor to the second reactor; reacting the metal product with air in the second reactor to produce a bimetallic composite oxide; and providing a second reactor The bimetallic composite oxide produced in the first reactor. The bimetal composite oxide includes an oxide of the first metal, a second metal oxide, and an oxide of a composite of the first metal and the second metal.

In the present embodiment, the preparation of the bimetal composite oxide can be carried out by uniformly mixing the metal salt of the first metal with the metal salt of the second metal to obtain a bimetallic aqueous solution; adding a water soluble solution to the bimetallic aqueous solution Molecules to obtain a precipitate and dry the precipitate; and, pulverize and calcine the dried precipitate to obtain a bimetallic composite oxide.

The advantages and spirit of the present invention will be further understood from the following detailed description of the invention.

Referring to FIG. 1, FIG. 1 is a flow chart showing the steps of a chemical loopback method according to an embodiment of the present invention.

As shown in FIG. 1, the chemical loop method of the present embodiment includes the following steps: in step S10, providing a bimetallic composite oxide to the first reactor; and in step S12, the bimetallic composite oxide is in the first reactor. a combustion reaction with the fuel to produce a metal product, a gas, and thermal energy; then, in step S14, the metal product produced by the combustion in the first reactor is supplied to the second reactor; in step S16, the metal product is In the second reactor, an oxidation reaction with air is performed to produce a bimetallic composite oxide; and, in step S18, the bimetallic composite oxide produced by the second reactor is supplied to the first reactor.

In this embodiment, the bimetal composite oxide of step S10 may comprise an oxide of the first metal, an oxide of the second metal, and an oxide of the first metal and the second metal chemically bonded. Complex. For example, if the first metal is iron and the second metal is nickel, the bimetal composite oxide may be an iron-nickel composite oxide containing iron oxide (Fe ₂ O ₃ ), nickel oxide (NiO), iron nickel. A composite of oxides (NiFe ₂ O ₄ ).

In step S12, the fuel may be a fossil fuel such as methane or propane, and a combustion reaction with the bimetallic composite oxide to produce a metal product, gas and heat. For example, a combustion reaction of methane and an iron-nickel composite oxide can obtain an iron metal, a nickel metal, an iron-nickel composite, a gas and heat, and therefore, for a bimetallic composite oxide, it is tied to the first reaction. The reduction reaction is carried out in the apparatus. Note that in order for the fuel to only react with the bimetallic composite oxide, the first reactor is filled with a non-oxygen atmosphere to avoid reaction of the fuel with other oxygen atoms. In practice, the inert gas may be first charged in the first reactor and then subjected to a combustion reaction.

The heat energy generated in step S12 can be used to heat the water to generate steam and cause the steam to drive the generator to generate electricity. Further, since the fuel-based fossil fuel in step S12, such as methane or propane, the generated gas contains carbon dioxide and water vapor. According to another embodiment, the gas produced in step S12 can be treated by discharging the generated gas from the first reactor; separating the water vapor in the gas by condensation; and sequestering the condensation After the gas. The condensed gas has separated the water vapor, so the remaining gas is a carbon dioxide of relatively high purity, which can be directly sealed for the purpose of reducing carbon dioxide emissions. In addition, the condensed gas can be directly reused rather than sealed, and the same can be achieved for carbon dioxide emission reduction.

Referring to FIG. 1 again, in the specific embodiment, the first reactor and the second gas reactor may be a fluidized bed reactor, and when the metal product is reacted in the first reactor (combustion reactor), Directly supplied to the second reactor (air reactor) as described in step S14. Next, in step S16, when the metal product is located in the second reactor, a suitable environment is provided therein to oxidize the metal product to produce a bimetallic composite oxide. For example, as described above, a metal product comprising an iron metal, a nickel metal, and an iron-nickel composite, which is oxidized, produces a composite comprising iron oxide, nickel oxide, iron nickel oxide, etc., that is, a step An iron-nickel composite oxide that reacts with fuel in S12. Since the metal product is subjected to an oxidation reaction in the second reactor, the second reactor may be filled with air or other oxygen-containing atmosphere.

Finally, the bimetallic composite oxide produced in the second reactor is supplied to the first reactor in step S18. In practice, when a suitable environment and sufficient fuel are provided in the first reactor, the bimetallic composite oxide can again undergo a combustion reaction with the fuel to produce a metal product, gas, and heat. Please refer to FIG. 2, which is a flow chart of the steps of the chemical loop method according to another embodiment of the present invention. As shown in FIG. 2, after the bimetal composite oxide produced in the second reactor in step S16 is supplied to the first reactor through step S18, step S12 may be continued to form a continuous loop cycle, thereby continuing the heat release. The steps of the specific embodiments are substantially the same as the steps corresponding to the above specific embodiments, and thus will not be further described herein.

In the present embodiment, the chemical loop method of the present invention performs step S12 and step S16 in a phased manner, that is, after the reduction reaction of the bimetallic composite oxide is completed, the product is subjected to an oxidation reaction to obtain The original bimetallic composite oxide. According to the ratio of the two metals in the bimetallic composite oxide, the reaction time of the reduction reaction and the oxidation reaction can be adjusted. In summary, the chemical ring process is performed by the bimetal composite oxide, and the oxidation rate is high and the reduction rate is high. In other words, the oxidation and reduction time can be shortened and the two can be made close to each other, so that the reaction efficiency can be improved and the chemical loop process can be designed.

Referring to FIG. 3, FIG. 3 is a flow chart showing the steps of a method for preparing a bimetal composite oxide according to another embodiment of the present invention. The bimetallic composite oxide prepared by the method of the present embodiment can be used in the above specific embodiment as an oxygen carrier for a combustion reaction of a fuel. As shown in FIG. 3, the method for preparing a bimetallic composite oxide comprises the steps of: uniformly mixing a metal salt of a first metal and a metal salt of a second metal in an aqueous solution in step S20 to obtain a bimetal aqueous solution; In step S22, a water-soluble polymer is added to the aqueous solution of the bimetal, and a precipitate is obtained by the reaction, and the precipitate is dried; finally, in step S24, the dried precipitate is pulverized and calcined to obtain a bimetallic composite oxide. .

Taking the iron-nickel bimetal composite oxide as an example, the step S20 is to uniformly mix the iron metal salt and the nickel metal salt in the aqueous solution, wherein the iron metal salt may be iron nitrate and the nickel metal salt may be nickel nitrate, and the two kinds of nitric acid The metal salt can be added to water in different proportions to obtain an aqueous solution of iron-nickel metal. Next, a water-soluble polymer, for example, polyethylene glycol, is added to an aqueous solution of iron-nickel metal as a dispersing agent, and a precipitate is obtained by reaction and dried, as described in step S22.

In step S24, the dried precipitate is pulverized and then calcined. When the temperature range of the calcination reaches a specific temperature range, the metal iron and nickel in the precipitate are oxidized to form iron oxide (Fe ₂ O ₃ ) and oxidized. Nickel (NiO), and both iron and nickel are sintered and oxidized to form iron nickel oxide (NiFe ₂ O ₄ ). Therefore, the iron-nickel composite oxide produced includes the above three, and the composite of the above three Things. In practice, the above iron-nickel composite oxide may be calcined at a temperature ranging from 500 ° C to 1600 ° C, and preferably, the temperature may range from 700 ° C to 1100 ° C. Please note that depending on the type of the first metal and the second metal, the calcination temperature can be adjusted accordingly.

Please refer to Table 1 below. Table 1 describes the preparation conditions of the iron-nickel composite oxide according to the above specific examples. As shown in Table 1, samples 1 to 4 were mixed with nickel nitrate and iron nitrate in water at different ratios, and then polyethylene glycol was selectively added, followed by calcining the precipitate at 700 ° C or 1000 ° C for 6 hours. And get the product, that is. Iron-nickel composite oxide. In addition, referring to the following Table 2, Table 2 shows that the iron-nickel composite oxide, pure iron oxide, pure nickel oxide and pure iron nickel oxide produced in the samples 1 to 4 of Table 1 are used in the chemical loop process. The time required for the oxidation and reduction reactions.

As shown in Table 1 and Table 2, the conditions for preparing iron-nickel composite oxides in samples 1 to 4 are different, and the oxidation time and reduction time required for the chemical loop process are also different depending on the preparation conditions. There is a difference, however, compared to pure iron oxide, pure nickel oxide and pure iron nickel oxide, the complete oxidation time and complete reduction time required for the sample 1~4 iron-nickel composite oxide used in the chemical loop process And the two are similar, in other words, they have a high oxidation rate and a high reduction rate. In contrast, the oxidation rate of pure iron oxide and pure iron nickel oxide is much higher than the reduction rate, and the reduction rate of pure nickel oxide is much higher than its oxidation rate. Since the complete oxidation time of the iron-nickel composite oxide prepared in the samples 1 to 4 is close to the complete reduction time in the chemical loop process, it is advantageous for the design of the chemical loop program.

Further, according to another embodiment of the present invention, the bimetallic composite oxide in the above chemical loop method may be supported on a support, and then subjected to reduction or oxidation in the first reactor or the second reactor. For example, when the iron-nickel composite oxide is prepared by the method of FIG. 3, the iron-nickel composite oxide may be further supported on a support composed of an inert material. Next, the iron-nickel composite oxide is supplied together with the support to the first reactor of the method of FIG. 1, and the iron-nickel composite oxide is subjected to a combustion reaction with the fuel on the support, and In the case of the iron-nickel composite oxide, the reduction reaction of the iron-nickel composite oxide is carried out in the first reactor. When the reduction reaction of the iron-nickel composite oxide is completed, a metal product is produced on the support, and then the metal product is supplied together with the support to the second reactor to carry out an oxidation reaction of the metal product. The bimetal composite oxide is supported on the support and placed in a chemical loop process to further increase the reactivity of the chemical loop process and lower the operating temperature.

In summary, the chemical loop method of the present invention performs reduction and oxidation reactions in the two reactors of the double metal composite oxide in the loop, so that the loop can be continuously continued and an exothermic reaction is continuously generated for power generation. Compared with the prior art, the bimetal composite oxide used in the method of the invention has both a high oxidation rate and a high reduction rate, so that the time required for the two reactions in the chemical loop process is short and the two are similar, and therefore, It effectively solves the shortcomings of the technical loop design process in the prior art, and further makes the chemical loop program easier to apply to the carbon dioxide emission reduction of thermal power plants.

The features and spirit of the present invention will be more apparent from the detailed description of the preferred embodiments. On the contrary, the intention is to cover various modifications and equivalents within the scope of the invention as claimed. Therefore, the scope of the patented scope of the invention should be construed as broadly construed in the

S10~S18. . . Process step

S20~S24. . . Process step

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart showing the steps of a chemical loopback method in accordance with an embodiment of the present invention.

2 is a flow chart showing the steps of a chemical loop method in accordance with another embodiment of the present invention.

Figure 3 is a flow chart showing the steps of a method for preparing a bimetallic composite oxide according to another embodiment of the present invention.

S10~S18. . . Process step

Claims (10)

A chemical loop method using a bimetal composite oxide, comprising the steps of: providing a bimetal composite oxide in a first reactor, wherein the bimetal composite oxide comprises a first metal oxide, a first a metal oxide and an oxide of a composite of the first metal and the second metal; the bimetal composite oxide is subjected to a combustion reaction with a fuel in the first reactor to produce a metal product and a gas; The metal product produced in the first reactor to a second reactor; the metal product is reacted with air in the second reactor to produce the bimetallic composite oxide; and the second reactor is provided The bimetallic composite oxide is passed to the first reactor. The chemical loop method according to claim 1, wherein the bimetallic composite oxide is an iron-nickel composite oxide, and the metal product comprises iron, nickel, and an iron-nickel composite. The chemical loop method of claim 2, wherein the iron-nickel composite oxide comprises a composite of iron oxide, nickel oxide, and iron nickel oxide. The chemical loopback method of claim 1, further comprising the steps of uniformly mixing the metal salt of the first metal and the metal salt of the second metal in an aqueous solution to obtain a bimetal aqueous solution; A water-soluble polymer is obtained in the aqueous solution of the bimetal to obtain a precipitate, and the precipitate is dried; and the precipitate is dried and calcined to obtain the bimetal composite oxide. The chemical loop method of claim 4, wherein the temperature of the precipitate after calcination drying is between 500 ° C and 1600 ° C, and preferably between 700 ° C and 1100 ° C. The chemical loopback method of claim 4, wherein the bimetallic composite oxide is an iron-nickel composite oxide, and the first metal-based iron, the second metal-based nickel, and the first metal The metal salt is iron nitrate, the metal salt of the second metal is nickel nitrate, and the water-soluble polymer is polyethylene glycol. The chemical loop method of claim 1, wherein the fuel is methane. The chemical loopback method of claim 1, further comprising the steps of: supporting the bimetallic composite oxide on a support; and providing the bimetallic composite oxide and the support in the first In a reactor. The chemical loop method of claim 1, wherein the first reactor and the second reactor are fluidized bed reactors. The chemical loop method of claim 1, further comprising the steps of: removing the gas generated in the first reactor; condensing the gas to remove water vapor in the gas; and sequestering the condensation This gas is later.