System for preparing urea by reducing carbon emission through renewable energy sources and urea preparation method

Abstract

The invention provides a system for preparing urea by reducing carbon emission through renewable energy sources. The core of the system is that an electrolytic cell is used to decompose water to produce hydrogen and oxygen, where hydrogen is delivered to the first reaction furnace and oxygen is directed to the gasification furnace. In the first reaction furnace, nitrogen and hydrogen are combined to produce ammonia. And meanwhile, in the gasification furnace, raw material coal is converted into synthesis gas and is conveyed to the combustion furnace through a pipeline. Energy generated by the combustion furnace is used for driving the turbine so as to drive the generator to generate electricity. In addition, supercritical carbon dioxide serves as an energy storage medium, waste heat generated after the supercritical carbon dioxide expands to do work in the turbine is utilized, energy recovery is conducted through the heat regenerator and the condenser, and finally the supercritical carbon dioxide returns to the system to be recycled. By the adoption of the structure, unstable green energy sources such as wind energy and solar energy are ingeniously integrated, and it is ensured that the energy sources can be effectively utilized even if the energy sources cannot be directly connected into a power grid.

Description

Technical Field

[0001] The present invention relates to the technical field of green energy storage, and in particular to a system and a method for preparing urea by utilizing renewable energy to reduce carbon emissions. Background Art

[0002] At present, the generation of green energy such as wind and solar energy faces many challenges. For example, the energy density of wind and solar power generation is relatively low, and a large area of ​​site is required to obtain sufficient energy. In addition, due to natural conditions, the continuous power supply cannot be guaranteed due to the influence of weather, season, geographical location, etc. Most importantly, the cost of current large-scale energy storage technologies (such as battery energy storage, pumped storage, etc.) is still relatively high. The existing power grid infrastructure has insufficient regulation capacity and flexibility, and it is difficult to adapt to the access and fluctuation of large-scale renewable energy. The proportion of wind power and solar power generation in the power grid is limited. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a system and method for preparing urea by using renewable energy to reduce carbon emissions, and to use renewable energy such as wind and solar energy as energy devices for preparing urea, so as to make full use of green energy that cannot be directly incorporated into the power grid for stable power generation. Supercritical carbon dioxide is used as an energy storage medium, and the turbine performs external work to drive the generator to generate electricity, and the waste heat discharged by the turbine is recovered, which effectively reduces the energy loss of the system, greatly reduces the construction cost, and improves the operating economy of the system and the energy utilization efficiency.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a system for preparing urea by using renewable energy to reduce carbon emissions, comprising an electrolyzer, a hydrogen delivery pipeline on the electrolyzer is connected to a first reaction furnace, and an oxygen delivery pipeline on the electrolyzer is connected to a gasifier; The first reaction furnace is also connected to an air separator, which supplies nitrogen to the first reaction furnace; The gasifier contains raw coal, the gasifier is provided with a synthetic gas delivery pipeline connected to the combustion furnace, and the combustion furnace is provided with a delivery pipeline connected to the turbine; The turbine is connected to a generator, the turbine is provided with a pipe connected to a regenerator, the regenerator is provided with a pipe connected to an input condenser, the condenser is connected to a compressor, the compressor and the regenerator are connected again via a pipe and then extended to connect to a combustion furnace.

[0005] In a preferred embodiment, the air separator is provided with a nitrogen delivery pipeline connected to the first reaction furnace, and is also provided with an oxygen delivery pipeline connected between the electrolytic cell and the gasification furnace.

[0006] In a preferred solution, the ammonia gas generated by the backflow of the first reactor is transported to the second reactor through an ammonia transport pipeline. In a preferred solution, the output pipeline of the condenser is provided with a branch pipe connected to the second reaction furnace and a water delivery pipeline connected to the first storage tank.

[0007] In a preferred solution, the second reaction furnace output pipeline is connected to a second storage tank for storing urea.

[0008] In a preferred solution, the energy source of the electrolytic cell is provided by the electricity generated by wind and solar power generation, and the electricity generated by wind and solar power generation also supplies energy for the air separator.

[0009] The urea preparation method of the system for preparing urea by utilizing renewable energy to reduce carbon emissions according to the claim comprises the following steps: 1) The electricity generated by wind and solar power is used to power the electrolyzer and air separator; 2) The electrolyzer performs water electrolysis, and part of the generated hydrogen is transported to the first reaction furnace; 3) The air separator performs air separation, and the separated nitrogen is transported to the first reaction furnace; 4) Hydrogen and nitrogen react to generate ammonia through the catalytic action of the catalyst in the first reaction furnace; 5) Ammonia enters the second reactor and reacts with carbon dioxide to form urea; 6) The generated urea is transported to the second storage tank for storage.

[0010] The preferred solution also includes the following steps: 1) The oxygen generated in the electrolyzer is fed into the gasifier together with the oxygen separated in the air separator; 2) Oxygen reacts with raw coal in the gasifier to produce synthesis gas; 3) The synthesis gas is transported to the combustion furnace for high temperature heating and pressurization to produce supercritical carbon dioxide and water vapor; 4) Supercritical carbon dioxide and water vapor are transported to the turbine to perform work, and then the generator generates electricity; 5) Carbon dioxide and water vapor enter the regenerator to heat the carbon dioxide in the subsequent pipelines; 6) Carbon dioxide and water vapor enter the condenser and the condensed water is input into the first storage tank. The carbon dioxide is divided into two parts, one part enters the second reactor to participate in the production of urea, and the other part enters the compressor for pressurization; 7) The pressurized carbon dioxide is reintroduced into the combustion furnace for high-temperature heating and pressurization to produce supercritical carbon dioxide and repeat steps 3)-6).

[0011] In a preferred embodiment, the synthesis gas components in step 2) include methane, carbon monoxide, hydrogen and carbon dioxide.

[0012] The present invention provides a system and method for preparing urea by using renewable energy to reduce carbon emissions. By adopting the method and system, the following beneficial effects are achieved: (1) Using electricity generated by renewable energy such as wind power and solar energy as energy for water electrolysis and air separator startup can, on the one hand, absorb the energy wasted by unstable wind and photovoltaic power generation due to natural factors, and on the other hand, use green energy to generate hydrogen in the electrolyzer, thus realizing the production of green hydrogen from green electricity. (2) Hydrogen generated by water electrolysis reacts with nitrogen separated by an air separator in a reactor to generate ammonia. Urea generated by the reaction of ammonia and carbon dioxide can be used as fertilizer, animal feed, explosives, glue stabilizer and chemical raw material, etc. It is a very important chemical substance, which realizes the storage of energy that cannot be directly used in another way. (3) Zero carbon dioxide emissions are achieved by using supercritical carbon dioxide as an energy storage medium and utilizing its superior thermodynamic properties to drive the generator to generate electricity through the turbine. The generated electricity is used as energy for the reactor reaction and the waste heat discharged by the turbine is recovered, which effectively reduces the energy loss of the system, greatly reduces the construction cost, and improves the economic operation of the system and the energy utilization efficiency. (4) Only water and urea are discharged from the entire system, which realizes the recycling of carbon dioxide and achieves zero carbon dioxide emissions, greatly reducing construction costs and improving the system's operating economy and energy utilization efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 It is a schematic diagram of the overall structure of the present invention. DETAILED DESCRIPTION

[0014] Embodiment 1: A system for preparing urea by using renewable energy to reduce carbon emissions, comprising an electrolyzer 1, a hydrogen delivery pipeline on the electrolyzer 1 connected to a first reaction furnace 2, and an oxygen delivery pipeline on the electrolyzer 1 connected to a gasifier 4; The first reaction furnace 2 is also connected to an air separator 3, and the air separator 3 supplies nitrogen to the first reaction furnace 2; The gasifier 4 contains raw coal, and the gasifier 4 is provided with a synthetic gas delivery pipeline connected to the combustion furnace 5, and the combustion furnace 5 is provided with a delivery pipeline connected to the turbine 6; The turbine 6 is connected to a generator 7, and the turbine 6 is provided with a pipeline connected to a regenerator 8, and the regenerator 8 is provided with a pipeline connected to an input condenser 9, and the condenser 9 is connected to a compressor 11, and the compressor 11 is connected to the regenerator 8 again via a pipeline and then extended to be connected to the combustion furnace 5.

[0015] In a preferred solution, the air separator 3 is provided with a nitrogen delivery pipeline connected to the first reaction furnace 2 , and is also provided with an oxygen delivery pipeline connected between the electrolytic cell 1 and the gasification furnace 4 .

[0016] In a preferred solution, the ammonia gas generated by the backflow of the first reaction furnace 2 is transported to the second reaction furnace 12 through an ammonia transport pipeline. In a preferred solution, the output pipeline of the condenser 9 is provided with a branch pipe connected to the second reaction furnace 12 and a water delivery pipeline connected to the first storage tank 10 .

[0017] In a preferred solution, the output pipeline of the second reaction furnace 12 is connected to a second storage tank 13 for storing urea.

[0018] In a preferred solution, the energy source of the electrolytic cell 1 is provided by the electric energy generated by wind and solar power generation, and the electric energy generated by wind and solar power generation also supplies energy for the air separator 3 .

[0019] Embodiment 2: The urea preparation method of the system for preparing urea by utilizing renewable energy to reduce carbon emissions described in Example 1 comprises the following steps: 1) The electricity generated by wind and solar power generation is used to power the electrolyzer 1 and the air separator 3; 2) The electrolytic cell 1 performs water electrolysis, and part of the generated hydrogen is transported to the first reaction furnace 2; 3) The air separator 3 performs air separation, and the separated nitrogen is transported to the first reaction furnace 2; 4) Hydrogen and nitrogen react to generate ammonia through the catalytic action of the catalyst in the first reaction furnace 2; 5) Ammonia enters the second reaction furnace 12 and reacts with carbon dioxide to generate urea; 6) The generated urea is transported to the second storage tank 13 for storage.

[0020] The preferred solution also includes the following steps: 1) The oxygen generated in the electrolytic cell 1 is fed into the gasifier 4 together with the oxygen separated in the air separator 3; 2) Oxygen reacts with raw coal in the gasifier 4 to generate synthesis gas; 3) The synthesis gas is transported to the combustion furnace 5 where it is heated and pressurized at high temperature to produce supercritical carbon dioxide and water vapor; 4) The supercritical carbon dioxide and water vapor are transported to the turbine 6 to perform work, and then generate electricity by the generator 7; 5) Carbon dioxide and water vapor enter the regenerator 8 to heat the carbon dioxide in the subsequent pipeline; 6) Carbon dioxide and water vapor enter the condenser 9 and condense to produce water which is input into the first storage tank 10. Carbon dioxide is divided into two parts, one part enters the second reaction furnace 12 to participate in urea production, and the other part enters the compressor 11 for pressurization; 7) The pressurized carbon dioxide is reintroduced into the combustion furnace 5 for high-temperature heating and pressurization to produce supercritical carbon dioxide and repeat steps 3) to 6).

[0021] In a preferred embodiment, the synthesis gas components in step 2) include methane, carbon monoxide, hydrogen and carbon dioxide.

[0022] Embodiment 3: In the above scheme, the electrolytic cell 1 uses a wind turbine and a solar photovoltaic power generation device as energy devices for electrolyzing water, decomposing water to generate hydrogen and oxygen, and is connected to the first reaction furnace 2, the gasification furnace 4 and the combustion furnace 5 respectively through connecting pipes.

[0023] The first reaction furnace 2 is connected to the electrolytic cell 1 through a connecting pipeline to obtain hydrogen, and is connected to the air separator 3 to obtain nitrogen, and ammonia produced by the reaction of the two is transported to the second reaction furnace 12.

[0024] The air separator 3 uses a wind turbine and solar photovoltaic power generation as power sources to start the air separator 3, separates nitrogen and oxygen required for preparing ammonia, and transports the nitrogen to the first reaction furnace 2 and the oxygen to the gasification furnace 4 through a connecting pipeline.

[0025] The gasifier 4 uses coal as raw material, and causes a series of chemical reactions between the organic matter in the coal and a portion of the oxygen produced by the electrolytic cell 1 and the air separator 3 at a certain temperature and pressure, thereby generating a synthesis gas containing combustible gases such as methane and non-combustible gases such as carbon dioxide, and reacts with another portion of the oxygen in the combustion furnace 5 to generate carbon dioxide and water vapor.

[0026] The combustion furnace 5 reacts the synthesis gas produced by coal gasification with the oxygen produced in the electrolytic cell 1 to generate carbon dioxide and water vapor, transports the generated gas to the turbine 6 through a connecting pipeline, and heats and pressurizes the carbon dioxide after temperature adjustment by the regenerator 8 to generate supercritical carbon dioxide.

[0027] The turbine 6 is used to convert the energy contained in the carbon dioxide into mechanical energy to drive the generator 7 to generate electricity, and is connected to the combustion furnace 5 and the regenerator 8 through connecting pipes.

[0028] The regenerator 8 heats the carbon dioxide and water vapor passing through the turbine 6 and the carbon dioxide pressurized by the compressor 11 to a preset temperature, and is connected to the combustion furnace 5, the turbine 6, the condenser 9 and the compressor 11 through connecting pipes.

[0029] The condenser 9 condenses the gas into water and carbon dioxide, thereby separating carbon dioxide from water, and is connected to the first storage tank 10 through a connecting pipe to transport the condensed water to the first storage tank 10 .

[0030] The first storage tank 10 (the second storage tank 13 ) is used to store condensed water (urea produced in the second reaction furnace 12 ).

[0031] The compressor 11 is used to increase the pressure of carbon dioxide, compress low-temperature and low-pressure carbon dioxide into high-temperature and high-pressure gas, and is connected to the regenerator 8 and the condenser 9 through connecting pipes.

[0032] The second reaction furnace 12 is a place where the ammonia generated in the first reaction furnace 2 and the carbon dioxide separated by condensation in the condenser 9 react to synthesize urea, and is connected to a storage tank 13 for storing urea.

[0033] In the above system: The energy storage medium is carbon dioxide, and the working medium is water. The energy storage medium circulates in a closed cycle consisting of the gasifier 4, the combustion furnace 5, the turbine 6, the generator 7, the regenerator 8, the condenser 9, the compressor 11 and the second reaction furnace 12 and their connecting pipelines, and the working medium is reused in the closed cycle consisting of the gasifier 4, the combustion furnace 5, the turbine 6, the generator 7, the regenerator 8 and the condenser 9 and their connecting pipelines.

[0034] Using green energy such as wind and solar energy as energy for electrolyzing water and starting air separators can, on the one hand, absorb the energy wasted by the instability of wind and photovoltaic power generation caused by natural factors. On the other hand, using green energy to generate hydrogen in the electrolyzer 1 and realize the production of "green hydrogen" from "green electricity" is of great significance to accelerating the development of the hydrogen energy industry, reducing carbon emissions, and deepening the construction of renewable energy demonstration areas.

[0035] The oxygen generated in the electrolytic cell 1 is introduced into the gasifier 4 as a gasifying agent for pure oxygen gasification of coal to produce synthesis gas, and is introduced into the combustion furnace 5 for oxygen-enriched combustion with the synthesis gas to produce carbon dioxide and water vapor. At the same time, the carbon dioxide compressed by the compressor 11 and heated by the regenerator 8 is re-introduced into the combustion furnace 5 for high-temperature heating and pressurization to produce supercritical carbon dioxide. The supercritical carbon dioxide generated in this process drives the generator 7 to generate electricity through the turbine 6. The electricity generated by the generator 7 is used as the energy source for the reaction in the reactor, thereby improving the utilization rate of electricity. The waste of carbon dioxide is avoided and zero carbon dioxide emission is achieved, which not only significantly improves the overall efficiency of the system, reduces economic costs, enhances the adaptability of the system, but also reduces greenhouse gas emissions, and has a positive impact on the environment.

[0036] The regenerator 8 utilizes the waste heat of the gas after the turbine 6 does work, and circulates and heats the generated supercritical carbon dioxide, thereby avoiding energy waste. The gas after regenerator 8 is condensed by condenser 9, and water and carbon dioxide can be separated. The condensed water enters the first storage tank 10 through the connecting pipe. Carbon dioxide is recycled in the system. During the whole process, carbon dioxide is zero-emitted, which has a positive impact on environmental protection, realizes the comprehensive utilization of energy, reduces heat loss, and greatly saves energy while improving energy utilization efficiency, reducing enterprise operating costs.

[0037] Using supercritical carbon dioxide as an energy storage medium and taking advantage of its excellent thermodynamic properties and environmentally friendly characteristics not only improves the overall efficiency of the system, reduces economic costs, and enhances the sustainability of the system, but also helps to achieve more efficient energy storage, which is of great significance for promoting the development of sustainable energy solutions. In addition, the use of carbon dioxide as an energy storage medium can also be combined with carbon dioxide capture and storage technology to reduce greenhouse gas emissions and have a positive impact on the environment.

[0038] The hydrogen produced in the electrolyzer 1 and the nitrogen separated by the air separator 3 react chemically under the catalysis of the catalyst in the first reaction furnace 2 to generate ammonia, and the ammonia and the carbon dioxide condensed by the condenser 9 react in the second reaction furnace 12 to generate urea. The use of "green electricity" to prepare urea can use and store power that cannot be directly used in another way, thereby improving the utilization efficiency of electricity generated by renewable energy generation. Urea can be used as fertilizer, animal feed, explosives, glue stabilizer and chemical raw material, etc., and is a very important chemical substance.

Claims

1. A system for preparing urea by using renewable energy to reduce carbon emissions, characterized in that: It comprises an electrolyzer (1), wherein a hydrogen delivery pipeline on the electrolyzer (1) is connected to a first reaction furnace (2), and an oxygen delivery pipeline on the electrolyzer (1) is connected to a gasification furnace (4); The first reaction furnace (2) is also connected to an air separator (3), and the air separator (3) supplies nitrogen to the first reaction furnace (2); The gasifier (4) contains raw coal, the gasifier (4) is provided with a synthetic gas delivery pipeline connected to the combustion furnace (5), and the combustion furnace (5) is provided with a delivery pipeline connected to the turbine (6); The turbine (6) is connected to a generator (7), the turbine (6) is provided with a pipeline connected to a regenerator (8), the regenerator (8) is provided with a pipeline connected to an input condenser (9), the condenser (9) is connected to a compressor (11), the compressor (11) and the regenerator (8) are connected again via a pipeline and then extended to be connected to a combustion furnace (5).

2. A system for preparing urea by using renewable energy to reduce carbon emissions according to claim 1, characterized in that: The air separator (3) is provided with a nitrogen delivery pipeline connected to the first reaction furnace (2), and is also provided with an oxygen delivery pipeline connected between the electrolytic cell (1) and the gasification furnace (4).

3. A system for preparing urea by using renewable energy to reduce carbon emissions according to claim 1 or 2, characterized in that: Ammonia gas generated by backflow in the first reaction furnace (2) is transported to the second reaction furnace (12) through an ammonia transport pipeline.

4. A system for preparing urea by using renewable energy to reduce carbon emissions according to claim 3, characterized in that: The output pipeline of the condenser (9) is provided with a branch pipe connected to the second reaction furnace (12) and a water delivery pipeline connected to the first storage tank (10).

5. The system for preparing urea by utilizing renewable energy to reduce carbon emissions according to claim 3, characterized in that: The output pipe of the second reaction furnace (12) is connected to a second storage tank (13) for storing urea.

6. The system for preparing urea by utilizing renewable energy to reduce carbon emissions according to claim 1, characterized in that: The energy source of the electrolytic cell (1) is provided by the electric energy generated by wind and solar power generation, and the electric energy generated by wind and solar power generation also supplies energy for the air separator (3).

7. A urea preparation method according to any one of claims 1 to 6, characterized in that: The following steps are involved: 1) The electric energy generated by wind and solar power generation is used to power the electrolyzer (1) and the air separator (3); 2) The electrolytic cell (1) performs water electrolysis, and part of the generated hydrogen is transported to the first reaction furnace (2); 3) The air separator (3) performs air separation, and the separated nitrogen is transported to the first reaction furnace (2); 4) Hydrogen and nitrogen react in the first reaction furnace (2) through the catalytic action of the catalyst to generate ammonia; 5) Ammonia enters the second reaction furnace (12) and reacts with carbon dioxide to generate urea; 6) The generated urea is transported to the second storage tank (13) for storage.

8. The method for preparing urea based on a system for preparing urea by utilizing renewable energy to reduce carbon emissions according to claim 7, characterized in that The following steps are also included: 1) The oxygen generated in the electrolytic cell (1) and the oxygen separated in the air separator (3) are input into the gasifier (4); 2) Oxygen reacts with raw coal in the gasifier (4) to generate synthesis gas; 3) The synthesis gas is transported to the combustion furnace (5) for heating and pressurization at a medium-high temperature to produce supercritical carbon dioxide and water vapor; 4) The supercritical carbon dioxide and water vapor are transported to the turbine (6) to perform work, and then the generator (7) generates electricity; 5) Carbon dioxide and water vapor enter the regenerator (8) to heat the carbon dioxide in the subsequent pipeline; 6) Carbon dioxide and water vapor enter the condenser (9), and the water produced by condensation is input into the first storage tank (10). The carbon dioxide is divided into two parts, one part enters the second reaction furnace (12) to participate in the production of urea, and the other part enters the compressor (11) for pressurization; 7) The pressurized carbon dioxide is reintroduced into the combustion furnace (5) for high-temperature heating and pressurization to produce supercritical carbon dioxide and repeat steps 3) to 6).

9. The urea preparation method of the system for preparing urea by utilizing renewable energy to reduce carbon emissions according to claim 8, characterized in that: The synthesis gas components in step 2) include methane, carbon monoxide, hydrogen and carbon dioxide.

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