A chemical looping combustion mercury removal system and method based on oxygen carrier oxygen-chlorine double cycle

Abstract

The application discloses a chemical looping combustion mercury removal system and method based on oxygen carrier oxygen-chlorine double circulation. The system comprises an air reactor, a fuel reactor, a chlorine in-situ modification chamber, a separator, a dechlorination chamber, a condenser, a conventional pollutant removal device, a carbon capture and storage device and an oxygen carrier passage. The important position of chlorine in the mercury oxidation reaction is coupled with the synergistic mercury removal effect of the oxygen carrier, greatly improving the oxidation efficiency of elemental mercury in the chemical looping combustion flue gas. The chlorine is used to modify the copper-containing oxygen carrier, an oxygen-chlorine double circulation is constructed in the oxygen carrier, and the oxygen carrier simultaneously realizes the transmission of oxygen and chlorine. The chlorine component is introduced from the chlorine in-situ modification chamber, avoiding the corrosion of chlorine to the heat receiving surface after the fuel reactor. The excess chlorine is absorbed by the dechlorination agent in the dechlorination chamber, meeting the environmental protection requirements. The application realizes deep mercury removal in the chemical looping combustion system, guarantees the safety of the system operation, and has significant environmental and social benefits.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical looping combustion, and particularly relates to a chemical looping combustion mercury removal system and method based on an oxygen-carrier oxygen-chlorine double circulation. BACKGROUND

[0002] Chemical looping combustion technology can effectively increase the CO2 concentration in coal-fired flue gas and significantly reduce the cost of carbon capture. However, the mercury released during combustion is easy to form amalgam (mercury alloy) with aluminum in the chemical looping combustion system, which causes corrosion and fracture of the aluminum CO2 compression and liquefaction equipment, and is a major risk factor for the safe operation of the system.

[0003] The existing coal-fired flue gas mercury removal method is developed based on the current mercury emission standard (30 μg / m 3 ) of coal-fired power plants. For traditional coal-fired power plants, mercury is removed as a flue gas pollutant and does not threaten the safety of the system; but in the chemical looping combustion system, in order to ensure its long-term safe operation, the recommended value of the mercury concentration of the flue gas before entering the CO2 compression and liquefaction equipment is below 0.01 μg / m 3 . Therefore, the existing mercury removal method cannot meet the deep mercury removal demand of the chemical looping combustion system, and is a bottleneck restricting the safe operation of the system.

[0004] Promoting the conversion of elemental mercury to oxidized mercury is the key to improving the mercury removal efficiency. However, there are many reducing components in the fuel reactor of the chemical looping combustion system, which are not conducive to the oxidation of mercury, and the fuel no longer directly contacts with oxygen, but realizes the transmission of oxygen through the oxygen carrier. It can be imagined that the oxygen carrier plays an important role in the migration process of mercury. At present, some scholars have carried out related research on the mercury removal technology of the oxygen carrier. For example, in the patent "Coal chemical looping combustion mercury removal device and method" (authorized publication number: CN111001292B), the General Coal Ash is used as an oxygen carrier to promote the oxidation of elemental mercury in the flue gas; in the patent "Coal chemical looping combustion mercury removal device and method" (publication number: CN114963164A), the magnetic oxygen carrier is used to oxidize and adsorb mercury, and the recycling of the oxygen carrier is realized. In addition, chlorine is an important element for promoting the oxidation of mercury, and the chlorine content in China's coal is generally low, which is not conducive to mercury removal. Some scholars use the method of introducing chlorine-containing components to promote the oxidation of mercury in the flue gas. For example, in the patent "Waste gas treatment system and method for removing mercury in waste gas" (authorized publication number: CN102015070B), dilute hydrochloric acid is used as a chlorine source, and hydrogen chloride is sprayed into the flue gas to promote the oxidation of elemental mercury.

[0005] However, the above research still has some shortcomings: (1) The related research on oxygen carrier synergistic demercuration only uses the metal oxides contained in the oxygen carrier to promote the oxidation of elemental mercury, and the promotion effect of elemental mercury oxidation is limited, which is difficult to meet the needs of deep demercuration of the chemical looping combustion system; (2) The related research on the injection of hydrogen chloride into flue gas to promote demercuration must pass through excess chlorine in actual application to ensure ideal mercury oxidation effect, and high concentration of chlorine will cause corrosion of the metal heating surface, threatening the safety of the system; (3) If chlorine is combined with the oxygen carrier, it is expected to greatly promote the oxidation efficiency of elemental mercury, but the current research does not involve related systems and methods. SUMMARY

[0006] The purpose of the present application is to provide an oxygen-chlorine double cycle based chemical looping combustion demercuration system and method, which couples the important role of chlorine in the mercury oxidation reaction with the synergistic demercuration effect of the oxygen carrier, uses chlorine to modify the oxygen carrier, and uses the method of oxygen carrier chlorine release, so that deep demercuration of the chemical looping combustion system becomes possible. The present application innovatively proposes to use chlorine to modify the copper-containing oxygen carrier in situ, uses the oxygen carrier as a "chlorine carrier" at the same time, constructs an oxygen-chlorine double cycle, opens up a new demercuration path, and greatly improves the oxidation efficiency of elemental mercury, while avoiding the corrosion of the excess chlorine-containing component to the heat receiving surface behind the fuel reactor.

[0007] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0008] An oxygen-chlorine double cycle based chemical looping combustion demercuration system, comprising an air reactor, a fuel reactor, a chlorine in-situ modification chamber, a separator, a dechlorination chamber, a condenser, a conventional pollutant removal device, a carbon capture and storage device, and an oxygen carrier passage;

[0009] One end of the air reactor is connected to the oxygen carrier passage, and the other end of the air reactor is connected to the chlorine in-situ modification chamber; the air reactor is a place where the oxygen carrier is reloaded with oxygen, and the chlorine in-situ modification chamber is a place where the oxygen carrier is modified with chlorine in situ;

[0010] One end of the separator is connected to the chlorine in-situ modification chamber, and the other end of the separator is connected to the dechlorination chamber; the separator is a place where the oxygen carrier is separated from the reacted air and chlorine-containing gas, and the dechlorination chamber is a place where the chlorine-containing gas in the mixed gas is removed;

[0011] The fuel reactor is connected to the separator and the condenser at the top, and the other end of the fuel reactor is connected to the oxygen carrier passage;

[0012] The flue gas generated by the fuel reactor passes through the condenser, the conventional pollutant removal device and the carbon capture and storage device in sequence.

[0013] The present application further improves that the oxygen carrier contains metal copper, and the oxygen carrier reacts with chlorine-containing flue gas in the chlorine in-situ modification chamber to generate copper chloride.

[0014] The further improvement of the present application is that in order to ensure the loading effect of chlorine in the oxygen carrier, the chlorine-containing gas introduced into the chlorine in-situ modification chamber is excessive by 10% to 30%.

[0015] The further improvement of the present application is that the fuel reactor is the place where the fuel occurs combustion reaction, and is also the place where the oxygen carrier transports oxygen and chlorine.

[0016] The further improvement of the present application is that the condenser is the place where water vapor in the flue gas of the fuel reactor is separated.

[0017] The further improvement of the present application is that the dechlorination chamber contains a series of dechlorination agents, such as a calcium-based dechlorination agent, a copper-based dechlorination agent, or an activated alumina dechlorination agent.

[0018] The further improvement of the present application is that the oxygen carrier simultaneously realizes the oxygen-chlorine double circulation process of oxygen loading and chlorine loading between the air reactor, the fuel reactor, and the chlorine in-situ modification chamber.

[0019] The further improvement of the present application is that the conventional pollutant removal equipment includes a denitration device, a dust removal device, and a desulfurization device, and the oxidized mercury mainly in the form of mercury chloride is removed in the desulfurization device.

[0020] A chemical looping combustion mercury removal method based on an oxygen-chlorine double circulation oxygen carrier, which is based on a chemical looping combustion mercury removal system based on an oxygen-chlorine double circulation oxygen carrier, and includes the following steps:

[0021] 1) The mercury-containing fuel enters the fuel reactor and reacts with the oxygen carried by the oxygen carrier to produce flue gas containing mercury;

[0022] 2) The oxygen carrier simultaneously completes the chlorine release process in the fuel reactor, and the released chlorine reacts with elemental mercury in the flue gas to generate mercury chloride. The flue gas containing mercury chloride enters the condenser and the conventional pollutant removal equipment in turn, removes impurities in the flue gas, and leaves carbon dioxide with a concentration higher than 99.5% into a carbon capture and storage device;

[0023] 3) The oxygen carrier that completes the oxygen and chlorine transmission enters the air reactor through the oxygen carrier channel and reacts with oxygen in the air to load oxygen again;

[0024] 4) The oxygen carrier loaded with oxygen enters the chlorine in-situ modification chamber and reacts with the chlorine-containing gas to load chlorine again;

[0025] 5) The oxygen carrier that completes the oxygen and chlorine regeneration enters the separator together with the mixed gas, the particulate phase oxygen carrier is separated into the fuel reactor, and the remaining mixed gas enters the dechlorination chamber;

[0026] 6) In the dechlorination chamber, the unreacted chlorine-containing gas is removed by the dechlorination agent, and the operation of this cycle is completed.

[0027] 7) Repeat steps 1) to 6), the oxygen-chlorine double circulation of the oxygen carrier realizes the flue gas mercury removal of the chemical looping combustion system.

[0028] Compared with the prior art, the present application has at least the following beneficial technical effects:

[0029] The chemical looping combustion mercury removal system based on the oxygen-chlorine double circulation of the oxygen carrier integrates the important position of chlorine in the mercury oxidation reaction and the synergistic mercury removal effect of the oxygen carrier, and greatly promotes the oxidation efficiency of elemental mercury in the flue gas. The chlorine in-situ modification chamber is arranged, the chlorine-containing component is introduced into the system after the air reactor, direct introduction of the chlorine-containing component into the fuel reactor is avoided, and the safety of the heated surface after the fuel reactor is ensured. The dechlorination chamber is arranged, and the excess chlorine-containing component is absorbed before being discharged into the atmosphere, which meets the environmental protection concept.

[0030] The chemical looping combustion mercury removal method based on the oxygen-chlorine double circulation of the oxygen carrier, compared with other mercury removal methods using the oxygen carrier, constructs the oxygen-chlorine double circulation in the oxygen carrier, realizes the transmission of chlorine while transmitting oxygen, greatly improves the oxidation efficiency of elemental mercury in the flue gas of the fuel reactor, and has obvious advantages in deep mercury removal. Compared with the mercury removal method of directly introducing the chlorine-containing component into the flue gas, the present application uses the oxygen carrier as the carrier of chlorine, avoids the corrosion problem of the heated surface caused by the excess chlorine-containing component, and improves the safety of the system. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The figure is a schematic diagram of the system of the present application.

[0032] Explanation of reference signs:

[0033] 1 is an air reactor, 2 is a fuel reactor, 3 is a chlorine in-situ modification chamber, 4 is a separator, 5 is a dechlorination chamber, 6 is a condenser, 7 is a conventional pollutant removal device, 8 is a carbon capture and storage device, and 9 is an oxygen carrier passage. DETAILED DESCRIPTION

[0034] Exemplary embodiments of the present disclosure will be described in greater detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be accurately conveyed to those skilled in the art. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0035] As Figure 1As shown, the application provides a chemical looping combustion mercury removal system based on oxygen carrier oxygen-chlorine double cycle, which comprises an air reactor 1, a fuel reactor 2, a chlorine in-situ modification chamber 3, a separator 4, a dechlorination chamber 5, a condenser 6, a conventional pollutant removal device 7, a carbon capture and storage device 8 and an oxygen carrier passage 9.

[0036] The air reactor 1 is connected with the oxygen carrier passage 9 at one end, and connected with the chlorine in-situ modification chamber 3 at the other end; the air reactor 1 is a place for oxygen carrier to be reloaded with oxygen, and the chlorine in-situ modification chamber 3 is a place for the oxygen carrier to be modified with chlorine in-situ; the oxygen carrier contains copper, and the oxygen carrier can react with the chlorine-containing flue gas in the chlorine in-situ modification chamber 3 to generate copper chloride.

[0037] The separator 4 is connected with the chlorine in-situ modification chamber 3 at one end, and connected with the dechlorination chamber 5 at the other end; the separator 4 is a place for separating the oxygen carrier from the reacted air and chlorine-containing gas, and the dechlorination chamber 5 is a place for removing the chlorine-containing gas in the mixed gas.

[0038] The fuel reactor 2 is connected with the separator 4 and the condenser 6 at the top, and connected with the oxygen carrier passage 9 at the other end; the fuel reactor 2 is a place for combustion reaction of fuel, and also a place for oxygen and chlorine transmission of the oxygen carrier, and the condenser 6 is a place for separating water vapor in the flue gas of the fuel reactor.

[0039] The flue gas generated by the fuel reactor 2 passes through the condenser 6, the conventional pollutant removal device 7 and the carbon capture and storage device 8 in sequence.

[0040] Further, in order to ensure the loading effect of chlorine in the oxygen carrier, the chlorine-containing gas introduced into the chlorine in-situ modification chamber 3 needs to be excessive by 10% to 30%.

[0041] Further, the dechlorination chamber 5 contains a series of dechlorination agents, such as a calcium dechlorination agent, a copper dechlorination agent or an active alumina dechlorination agent.

[0042] Further, the oxygen carrier realizes oxygen-chlorine double cycle process of oxygen transmission and chlorine transmission between the air reactor 1, the fuel reactor 2 and the chlorine in-situ modification chamber 3.

[0043] Further, the conventional pollutant removal device 7 includes a denitration device, a dust removal device and a desulfurization device, and the oxidized mercury mainly in the form of mercury chloride is removed in the desulfurization device.

[0044] The application provides a chemical looping combustion mercury removal method based on oxygen carrier oxygen-chlorine double cycle, which comprises the following steps:

[0045] The mercury-containing fuel enters the fuel reactor 2, and reacts with the oxygen carried by the oxygen carrier to generate mercury-containing flue gas;

[0046] The oxygen carrier simultaneously completes the chlorine release process in the fuel reactor 2, and the released chlorine reacts with elemental mercury in the flue gas to generate mercury chloride. The flue gas containing mercury chloride enters the condenser 6 and the conventional pollutant removal device 7 in turn, removes impurities in the flue gas, and leaves high-concentration carbon dioxide into the carbon capture and storage device 8;

[0047] The oxygen carrier that completes oxygen transmission and chlorine transmission enters the air reactor 1 through the oxygen carrier channel 9, reacts with oxygen in the air, and is loaded with oxygen again;

[0048] The oxygen-loaded oxygen carrier enters the chlorine in-situ modification chamber 3, reacts with chlorine-containing gas, and is loaded with chlorine again;

[0049] The oxygen carrier that completes oxygen and chlorine regeneration enters the separator 4 together with the mixed gas, the particulate phase oxygen carrier is separated into the fuel reactor 2, and the remaining mixed gas enters the dechlorination chamber 5;

[0050] In the dechlorination chamber 5, the unreacted chlorine-containing gas is removed by the dechlorination agent, and the operation of this cycle is completed;

[0051] Repeat the above steps, and the oxygen-chlorine double circulation based on the oxygen carrier realizes the flue gas mercury removal of the chemical looping combustion system.

[0052] Taking copper-iron composite oxygen carriers as an example for research. Copper oxide and iron oxide were used as precursors of oxygen carriers, and their molar ratio was 1:1. After dissolution, stirring, drying, calcination, crushing and screening, copper-iron composite oxygen carriers CuFe2O4 were obtained. HCl gas was used as chlorine-containing gas to modify CuFe2O4 in-situ to obtain chlorine-containing oxygen carriers. Under the conditions of inlet mercury concentration of 1000 μg / m 3 , gas flow of 0.6 L / min, 30 mg chlorine in-situ modified copper-iron composite oxygen carriers can reduce the concentration of elemental mercury in flue gas to 0.25 μg / m 3 Below, the mercury removal efficiency is more than 99.975%, which can meet the needs of deep mercury removal of chemical looping combustion system.

[0053] In general, the present application proposes a chemical looping combustion mercury removal system and method based on oxygen carrier oxygen-chlorine double cycle, which couples the important position of chlorine in mercury oxidation reaction with the synergistic mercury removal effect of oxygen carrier, so that deep mercury removal of chemical looping combustion flue gas is possible. Among many metal chlorides, the copper-chlorine bond energy is the lowest, and the use of chlorine for in-situ modification of copper-containing oxygen carrier can greatly improve the performance of metal chloride in releasing active chlorine. The construction of oxygen-chlorine double cycle in the oxygen carrier enables the oxygen carrier to transport oxygen while realizing the transport of chlorine, greatly promoting the conversion of elemental mercury to oxidized mercury in the fuel reactor flue gas. The chlorine-containing component is introduced into the in-situ modification chamber after the air reactor, which avoids directly introducing the chlorine-containing component into the fuel reactor flue gas, ensuring that the heating surface after the fuel reactor is not corroded by chlorine. The excess chlorine-containing component is absorbed by the dechlorination agent before being discharged into the atmosphere, meeting the environmental protection requirements. The present application can meet the deep mercury removal demand in the operation process of the chemical looping combustion system, and ensure the safety of the system.

[0054] It should be understood that the embodiments are only used to illustrate but not to limit the scope of the present application. Furthermore, it should also be understood that those skilled in the art can make various modifications or changes to the present application after reading the content taught by the present application, however, these equivalent forms also fall within the scope defined by the appended claims of the present application.

Claims

1. An oxygen-carrier-based oxygen-chlorine double-cycle chemical looping combustion mercury removal system, characterized in that, The system comprises an air reactor (1), a fuel reactor (2), a chlorine in-situ modification chamber (3), a separator (4), a dechlorination chamber (5), a condenser (6), a conventional pollutant removal device (7), a carbon capture and storage device (8) and an oxygen carrier channel (9). The air reactor (1) is connected to the oxygen carrier channel (9) at one end and to the chlorine in-situ modification chamber (3) at the other end. The air reactor (1) is a place for the oxygen carrier to reload oxygen, the fuel reactor (2) is a place for the fuel to undergo combustion reaction and also a place for the oxygen carrier to transfer oxygen and chlorine, and the chlorine in-situ modification chamber (3) is a place for the oxygen carrier to undergo chlorine in-situ modification. The oxygen carrier simultaneously realizes oxygen-chlorine double circulation process of oxygen transfer and chlorine transfer between the air reactor (1), the fuel reactor (2) and the chlorine in-situ modification chamber (3). The separator (4) is connected to the chlorine in-situ modification chamber (3) at one end and to the dechlorination chamber (5) at the other end. The separator (4) is a place for the oxygen carrier to be separated from the reacted air and chlorine-containing gas, and the dechlorination chamber (5) is a place for removing the chlorine-containing gas in the mixed gas. The fuel reactor (2) is connected to the separator (4) and the condenser (6) at the top, the condenser (6) is a place for separating water vapor in the flue gas of the fuel reactor (2), and the fuel reactor (2) is connected to the oxygen carrier channel (9) at the other end. The flue gas generated by the fuel reactor (2) passes through the condenser (6), the conventional pollutant removal device (7) and the carbon capture and storage device (8) in sequence.

2. The oxygen carrier-based oxychlorine double-loop chemical looping combustion mercury removal system according to claim 1, characterized in that, The oxygen carrier contains copper, and the oxygen carrier reacts with the chlorine-containing flue gas in the chlorine in-situ modification chamber (3) to generate copper chloride.

3. The oxygen carrier-based oxychlorine double-loop chemical looping combustion mercury removal system according to claim 1, wherein, In order to ensure the loading effect of chlorine in the oxygen carrier, the chlorine-containing gas introduced into the chlorine in-situ modification chamber (3) is 10% to 30% excessive.

4. The oxygen carrier-based oxychlorine double-loop chemical looping combustion mercury removal system according to claim 1, characterized in that, The conventional pollutant removal device (7) comprises a denitration device, a dust removal device and a desulfurization device, and the oxidized mercury mainly in the form of mercury chloride is removed in the desulfurization device.

5. A method for mercury removal by chemical looping combustion based on oxygen carrier oxygen-chlorine double cycle, characterized in that, The method is based on the chemical looping combustion mercury removal system based on the oxygen carrier oxygen-chlorine double circulation according to any one of claims 1-4, and comprises the following steps: 1) The mercury-containing fuel enters the fuel reactor (2) and undergoes combustion reaction with the oxygen carried by the oxygen carrier to generate mercury-containing flue gas; 2) The oxygen carrier simultaneously completes the chlorine release process in the fuel reactor (2), the released chlorine reacts with the elemental mercury in the flue gas to generate mercury chloride, the flue gas containing the mercury chloride enters the condenser (6) and the conventional pollutant removal device (7) in sequence, impurities in the flue gas are removed, and carbon dioxide with a concentration higher than 99.5% is left to enter the carbon capture and storage device (8); 3) The oxygen carrier that has completed oxygen transfer and chlorine transfer enters the air reactor (1) through the oxygen carrier channel (9) and reacts with oxygen in the air to reload oxygen; 4) The oxygen carrier that has loaded oxygen enters the chlorine in-situ modification chamber (3) and reacts with the chlorine-containing gas to reload chlorine; 5) The oxygen carrier that has completed oxygen and chlorine regeneration enters the separator (4) together with the mixed gas, the particulate oxygen carrier enters the fuel reactor (2) after being separated, and the remaining mixed gas enters the dechlorination chamber (5); 6) In the dechlorination chamber (5), the unreacted chlorine-containing gas is removed by the dechlorination agent, and the operation of this cycle is completed. 7) repeating steps 1) to 6), realizing flue gas mercury removal of chemical looping combustion system based on oxygen-carrier oxygen-chlorine double cycle.

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