Variable-load chemical looping combustion system and using method

Abstract

The invention discloses a variable-load chemical looping combustion system which comprises an air reactor, a fuel reactor, a feeding loop and a material returning loop. An industrial steam supply heating surface A is arranged in the air reactor, and 1-N load regulators are connected in parallel between the air reactor and the fuel reactor; each load regulator comprises a furnace body, a fluidization device arranged in the furnace body, a gas inlet connected with the furnace body below the fluidization device, a gas outlet connected with the furnace body above the fluidization device, oxygen carrier inlet pipes and oxygen carrier outlet pipes, the oxygen carrier inlet pipes are connected with the fuel reactor and are provided with regulating valves, and the oxygen carrier outlet pipes are connected with the air reactor; an industrial steam supply heating surface B is arranged in the furnace body above the fluidizing device; the invention further discloses a using method of the variable-load chemical looping combustion system. According to the invention, the load can be flexibly and stably adjusted in a wide range, meanwhile, negative effects caused by cooling of the reaction area and reduction of the activity of the oxygen carrier are avoided, and efficient and reliable operation of the chemical looping combustion system under the wide-load working condition is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to a chemical looping combustion system and a use method, in particular to a variable load chemical looping combustion system and a use method. BACKGROUND

[0002] Chemical looping combustion technology realizes efficient and clean combustion of fuel by circulating oxygen carriers between fuel reactors and air reactors to transfer oxygen, and its core advantage is that it can directly separate high-concentration CO2 (carbon capture cost reduction of more than 60%) and inhibit the generation of NOx (emission reduction of 80%), and it is considered as a key technology for realizing carbon neutralization in the field of thermal power and industrial heat supply.

[0003] Although the chemical looping combustion technology has the advantage of efficient carbon dioxide capture, its large-scale application is restricted by the inherent contradiction between load regulation and constant temperature operation. Although the technology is derived from circulating fluidized bed boilers, there are significant differences in operating characteristics between the two: when the circulating fluidized bed adjusts the air volume to achieve load regulation (such as from high load to low load), the bed temperature will decrease but still maintain normal operation; when the chemical looping combustion system is adjusted in the same way, the bed temperature of the air reactor and the fuel reactor will decrease simultaneously, and when the load decreases to 90%, the temperature of the fuel reactor will drop to the critical value of 900 ℃; however, the system must be strictly maintained at a temperature range of 900-1050 ℃, because once the temperature is lower than 900 ℃, a chain reaction will be triggered: the reduction rate of fuel and oxygen carriers will decrease sharply, resulting in a sharp decrease in CO2 capture efficiency, and a large amount of by-products such as carbon and CO will be generated, and the surface of the oxygen carriers will be permanently deactivated by carbon / ash covering, ultimately leading to the difficulty of stable operation of the chemical looping combustion system. However, the traditional load regulation method will inevitably be accompanied by temperature fluctuations, and existing technical means cannot meet the requirements of wide load regulation from 30% to 100% and cannot solve the contradiction between temperature control and load response, which has become a key obstacle to the engineering application of the technology. SUMMARY

[0004] The purpose of the present application is to overcome the above-mentioned deficiencies of the prior art, and to provide a variable load chemical looping combustion system and a use method, which can realize flexible and stable regulation of load in a wide range by adding several load regulators and controlling the start and stop of the load regulators, while avoiding the negative effects of temperature drop in the reaction zone and reduction of oxygen carrier activity, and ensuring the efficient and reliable operation of the chemical looping combustion system under wide load conditions.

[0005] In order to achieve the above object, a variable load chemical looping combustion system of the present application comprises an air reactor, a fuel reactor, a feed loop and a return loop; characterized in that: the air reactor is provided with an industrial steam heating surface A, and 1-N load regulators are connected in parallel between the air reactor and the fuel reactor, wherein N is a positive integer; each load regulator comprises a furnace body, a fluidization device arranged in the furnace body, a gas inlet connected to the furnace body below the fluidization device, a gas outlet connected to the furnace body above the fluidization device, an oxygen carrier inlet pipe and an oxygen carrier outlet pipe, the oxygen carrier inlet pipe is connected to the fuel reactor and provided with a regulating valve, and the oxygen carrier outlet pipe is connected to the air reactor; the furnace body above the fluidization device is provided with an industrial steam heating surface B, and each industrial steam heating surface is in communication with an industrial steam pipeline. The load parameters of each load regulator can be equal. The load parameters of each load regulator can be unequal. As a further improvement of the present application, the regulating valves are all leak-proof valves; the leakage of fluidization air can be prevented, and the working state of the load regulator can be prevented from fluctuating. The use method of a variable load chemical looping combustion system of the present application comprises the following steps: A) the air reactor and the fuel reactor are put into operation, the air reactor and the fuel reactor are both connected to a certain fluidization gas, the oxygen carrier is circulated by the air reactor, the feed loop, the fuel reactor and the return loop, and the industrial steam heating surface A exchanges heat under the basic load; characterized in that: B) when the unit load increases, the regulating valve of the corresponding load regulator is opened, the corresponding load regulator is gradually filled with oxygen carrier particles, then the fluidization gas air is connected to the gas inlet of the load regulator, the load regulator enters the bubbling bed state, the oxygen carrier in the load regulator starts to overflow and release heat, exchanges heat with the industrial steam heating surface B in the load regulator, and the basic load + the adjustment load is the total load of the system; the overflowed oxygen carrier enters the air reactor for continuous circulation through the oxygen carrier outlet pipe; C) when the unit load decreases, the regulating valve of the corresponding load regulator is closed, the overflow amount of oxygen carrier particles and the oxidation heat in the corresponding load regulator gradually decrease, then the oxygen carrier particles in the load regulator are emptied, and the connection of the fluidization gas air is stopped, so that the inside of the corresponding load regulator is in a full empty state. The oxygen carrier and the air volume of the air reactor of the application are basically unchanged, the operating temperature of the air reactor and the combustion reactor is basically stable, the industrial steam supply heating surface A is always operated at the optimal temperature under the constant basic load, when the load increases or decreases, the adjusting valve of the corresponding number of load adjusters is opened or closed to adapt to the corresponding adjusting load, the total load can be adjusted in the range of the basic load to the full load, the flexible and stable adjustment of the load in a wide range can be realized, the requirements of various working conditions can be met, at the same time, the oxygen carrier in each load adjuster is full or empty in the stable state, the negative effects caused by the temperature drop of the reaction zone and the reduction of the activity of the oxygen carrier can be avoided, and the efficient and reliable operation of the chemical looping combustion system under wide load working conditions is ensured; each load adjuster is modularly designed, the construction and maintenance costs can be reduced, the economy is improved, and the different scale requirements can be adapted by increasing or decreasing the number of load adjusters; As a further improvement of the application, in step B), the amount of air introduced into the air reactor and the corresponding load adjuster is matched with the respective load parameter; the staged oxidation of the oxygen carrier and the temperature field coordinated management can be realized, and the energy loss can be reduced; As a further improvement of the application, in steps B) and C), when any corresponding load adjuster fails, the corresponding adjusting valve is closed; the dependence on key components can be reduced, the basic operation ability can be maintained under the fault condition, and the continuous production is ensured; In summary, by adding several load adjusters and controlling the start and stop of the load adjusters, the flexible and stable adjustment of the load in a wide range can be realized, the negative effects caused by the temperature drop of the reaction zone and the reduction of the activity of the oxygen carrier can be avoided, and the efficient and reliable operation of the chemical looping combustion system under wide load working conditions is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0006] Figure 1 The structure diagram of the embodiment of the variable load chemical looping combustion system of the application. DETAILED DESCRIPTION

[0007] The application will be further described below with reference to the drawings, taking a 100 MWth chemical looping combustion system as an example.

[0008] As Figure 1As shown, the load-variable chemical looping combustion system of the embodiment comprises an air reactor 1, a fuel reactor 2, a feed loop 3, a return loop 4, and a steam-water system (not shown). The air reactor 1 and the fuel reactor 2 are connected by the feed loop 3 and the return loop 4 to form a basic circulation loop, and the load parameter of the basic circulation loop is 30 MWth. The air reactor 1 is provided with an industrial steam heating surface A5 in the steam-water system. Five load regulators 6 (only the first and last two are shown) are connected in parallel between the air reactor 1 and the fuel reactor 2. Each load regulator 6 comprises a furnace body 7, a fluidizing device 8 arranged in the furnace body, a gas inlet 9 connected to the furnace body below the fluidizing device, a gas outlet 10 connected to the furnace body above the fluidizing device, an oxygen carrier inlet pipe 11, and an oxygen carrier outlet pipe 12. The oxygen carrier inlet pipe 11 is connected to the fuel reactor 2 and is provided with an adjusting valve 13. The adjusting valve 13 is a leak-proof valve and responds quickly. The valve body is high-temperature resistant. The oxygen carrier outlet pipe 12 is connected to the air reactor 1. The furnace body above the fluidizing device 8 is provided with an industrial steam heating surface B14. The five load regulators 6 are completely identical, and the load parameter of each load regulator 6 is 14 MWth. The industrial steam heating surface A5 and each industrial steam heating surface B14 are connected to an industrial steam pipeline (not shown) in the steam-water system. An embodiment of the present invention provides a method for using a variable load chemical loop combustion system, comprising the following steps: A) Basic load operation: Air reactor 1 and fuel reactor 2 are put into operation, and a certain amount of fluidizing gas is introduced into both air reactor 1 and fuel reactor 2. The fluidizing gas in air reactor 1 is air, and the amount of air introduced into air reactor 1 is matched with its load parameters. The fluidizing gas in fuel reactor 2 is not air. The oxygen carrier is circulated by air reactor 1, feed circuit 3, fuel reactor 2 and return circuit 4. The oxygen carrier releases 30 MWth of heat in air reactor 1, and after heat exchange by industrial steam supply heating surface A5, 15.069 MWth is carried away. The temperature inside fuel reactor 2 is 980 ℃, and the temperature inside air reactor 1 is 1050 ℃. At this time, all regulating valves 13 are fully closed, and all load regulators 6 are completely empty. B) Increasing the load from the base load (30%) to 58%: The basic circulation loop operation remains unchanged; the regulating valves 13 of the two load regulators 6 are opened, gradually filling the corresponding two load regulators 6 with oxygen-carrying particles. Then, the amount of fluidized gas air introduced through their gas inlet 9 matches their respective load parameters. The fluidization device 8 puts the load regulators 6 into a bubbling bed state. The oxygen-carrying particles in the two load regulators 6 begin to overflow, releasing 2×14 MWth of heat, which is exchanged with the industrial steam supply heating surface B14 inside. 2×7.032 MWth of heat is carried away by the industrial steam supply heating surface B14. At this time, the base load + the regulating load is the total system load of 58%. When stability is reached, the temperature inside the two load regulators 13 is 1050 ℃, the temperature inside the fuel reactor 2 is still 980 ℃, and the temperature inside the air reactor 1 is 1050 ℃. ℃; The overflowing oxygen carrier in the two load regulators 6 enters the air reactor 1 through the oxygen carrier outlet pipe 12 to continue circulating; then increase to full load: open the regulating valve 13 of the remaining three load regulators 6, so that the corresponding three load regulators 6 are gradually filled with oxygen carrier particles, and then the amount of fluidizing gas air introduced through its gas inlet 9 matches its load parameters. The oxygen carrier in the three load regulators 6 begins to overflow and release 3×14 MWth heat, which is carried away by the three industrial steam supply heating surface B14 with 3×7.032 MWth heat. At this time, the system reaches full load of 100%; C) Reduce from full load (100%) to load 86%: the operation of the basic circulation loop and the four load regulators 6 remains unchanged. Close the regulating valve of the remaining load regulator. The overflow flow of oxygen carrier particles and oxidation and heat release in this load regulator gradually decrease. Then, the oxygen carrier particles in this load regulator are emptied and the fluidizing gas air is stopped, so that its interior is completely empty. Its internal temperature is reduced from 1050℃. The temperature gradually decreases; in steps B) and C), when any load regulator 6 fails, its corresponding regulating valve 13 is closed; this reduces dependence on critical components, and basic operating capacity can still be maintained in the event of a failure, ensuring continuous production; The basic circulation loop of the embodiment bears 30% of the load, and each load regulator 6 bears 70% of the load; when the unit is at 30% of the total load, the oxygen carrier and air volume into the air reactor 1 remain basically unchanged, the operating temperature of the air reactor 1 and the combustion reactor 2 can be basically stable, and the industrial steam heating surface A5 can be operated at the best temperature under the basic constant load; when the load increases or decreases, the adjusting valves 13 of the corresponding number of load regulators 6 are opened or closed to adapt to the corresponding adjusting load, the total load can be adjusted in steps in the range from the basic load to the full load, the flexible and stable adjustment of the load in a wide range can be realized, the needs of various working conditions can be met, at the same time, the oxygen carriers in each load regulator 6 are full or empty in the stable state, the negative effects caused by the temperature drop of the reaction zone and the decrease of the activity of the oxygen carrier can be avoided, and the efficient and reliable operation of the chemical looping combustion system under wide load working conditions can be ensured; the five load regulators 6 are completely the same, which is convenient for collaborative adjustment; the parallel load regulators are modularized, which can reduce the construction and maintenance costs, improve the economy, effectively solve the problems of limited load adjustment range and slow dynamic response of the traditional system, significantly improve the load adjustment precision and response speed, and can also improve the adjustment precision and adapt to different scale requirements by increasing the number of load regulators 6; the basic load can still be maintained when a single point fails, and the robustness of the system is greatly enhanced; The present application is not limited to the above-mentioned embodiments, for example, the load parameters of each load regulator can not be equal, the air volume of the fluidized gas introduced into each load regulator is matched with the load parameter of each load regulator, the staged oxidation of the oxygen carrier and the temperature field collaborative management can be realized, the energy loss can be reduced, and the load adjustment precision can be further improved; The above embodiments are described, but it should be understood that the above embodiments are only for the purpose of example and illustration, and are not intended to limit the present application to the scope of the described embodiments.

Claims

1. A variable load chemical looping combustion system comprising an air reactor, a fuel reactor, a feed loop, and a return loop; characterized in that: The air reactor is provided with an industrial steam heating surface A, and 1-N load regulators are connected in parallel between the air reactor and the fuel reactor, wherein N is a positive integer; each load regulator comprises a furnace body, a fluidization device arranged in the furnace body, a gas inlet connected to the furnace body below the fluidization device, a gas outlet connected to the furnace body above the fluidization device, an oxygen carrier inlet pipe and an oxygen carrier outlet pipe, the oxygen carrier inlet pipe is connected to the fuel reactor and provided with a regulating valve, and the oxygen carrier outlet pipe is connected to the air reactor; the furnace body above the fluidization device is provided with an industrial steam heating surface B, and each industrial steam heating surface is communicated with an industrial steam pipeline.

2. A variable- load chemical-looping combustion system according to claim 1, characterized in that: The load parameters of the load regulators are equal.

3. A variable- load chemical-looping combustion system according to claim 1, characterized in that: The load parameters of the load regulators are not equal.

4. A variable- load chemical-looping combustion system according to claim 1 or 2 or 3, characterized in that: The regulating valves are leak-proof valves.

5. A method of using a variable load chemical looping combustion system, comprising the steps of: A) The air reactor and the fuel reactor are put into operation, the air reactor and the fuel reactor are both connected to a certain fluidizing gas, the oxygen carrier is circulated by the air reactor, the feeding circuit, the fuel reactor and the return circuit, and the industrial steam heating surface A exchanges heat under a basic load; B) when the unit load is increased, the regulating valve of the corresponding load regulator is opened, the corresponding load regulator is gradually filled with oxygen carrier particles, then the fluidizing gas air is introduced through the gas inlet, the load regulator enters a bubbling bed state, the oxygen carrier in the load regulator starts to overflow and release heat, and exchanges heat with the industrial steam heating surface B in the load regulator; the basic load + the adjustment load is the total load of the system; the overflowed oxygen carrier enters the air reactor for continuous circulation through the oxygen carrier outlet pipe; C) when the unit load is reduced, the regulating valve of the corresponding load regulator is closed, the overflow amount of the oxygen carrier particles in the corresponding load regulator and the oxidation heat are gradually reduced, then the oxygen carrier particles in the load regulator are emptied, and the fluidizing gas air is stopped, so that the inside of the corresponding load regulator is in a full empty state.

6. A method of using a variable- load chemical-looping combustion system according to claim 5, characterized in that: In step B), the amount of fluidizing gas air introduced into the air reactor and the corresponding load regulator is matched with the load parameter of each.

7. A method of using a variable- load chemical-looping combustion system according to claim 5 or 6, characterized in that: In steps B) and C), when any of the corresponding load regulators fails, the corresponding regulating valve is closed.

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