System for producing urea by using blast furnace gas

Abstract

The utility model discloses a system for producing urea by using blast furnace gas. The system comprises a purification device, a heating furnace, a pressure swing adsorption CO2 removal device, a gas mixing device, a synthesis ammonia device, a urea synthesis device, an electrolysis device and a pressure swing adsorption H2 removal device, a blast furnace gas output pipeline of the blast furnace is communicated with a fuel inlet of the heating furnace after passing through the purification device; a flue gas outlet of the heating furnace is communicated with an inlet of the pressure swing adsorption CO2 removal device; an N2 outlet of the pressure swing adsorption CO2 removal device is communicated with an inlet of the ammonia synthesis device through the gas mixing device, and a liquid ammonia outlet of the ammonia synthesis device is communicated with a liquid ammonia inlet of the urea synthesis device; a CO2 outlet of the pressure swing adsorption CO2 removal device is divided into two paths, one path is communicated with a CO2 inlet of the urea synthesis device, and the other path is communicated with an inlet of the electrolysis device. According to the system, under the condition that other gas sources are not introduced, multiple components in the blast furnace gas are recycled to the maximum extent, the problem that the blast furnace gas is difficult to utilize is solved, and high-value chemicals can be produced.

Description

Technical Field

[0001] The utility model relates to the field of resource utilization of steel plant tail gas, in particular to a system for producing urea by using blast furnace gas. Background Technique

[0002] Urea is one of the simplest organic compounds and also the nitrogen fertilizer with the highest nitrogen content at present. It can be used to produce high-polymer materials, plastic paints, adhesives, etc. As the world's largest producer and consumer of chemical fertilizers, China can produce up to 2 million tons of chemical fertilizers in a peak consumption month.

[0003] Blast furnace gas is a combustible gas by-produced in the process of blast furnace ironmaking. Its main components are CO, CO 2 , N 2 , and also contains a certain amount of COS, H 2 S and dust, etc. The CO content in blast furnace gas is about 25%. It is an important secondary energy source. At present, it is mainly used as the self-used fuel gas in the steel industry. On the one hand, it results in low utilization value of the gas. On the other hand, the large amount of CO 2 emissions after gas combustion cause environmental pollution problems. As a major steel-producing country, China can produce tens of billions of cubic meters of blast furnace gas in the steel industry every year. The gas resources are very rich. Therefore, the resource utilization of steel plant gas has become the key focus direction for steel enterprises to extend the industrial chain and create benefits. Based on this, it is urgent to develop a method for producing urea by using blast furnace gas to achieve the maximum resource utilization of blast furnace gas, and at the same time contribute to carbon emission reduction and the green and low-carbon transformation of the steel industry. Content of the Utility Model

[0004] The technical problem to be solved by the utility model is to provide a system for producing urea by using blast furnace gas to realize the comprehensive resource utilization of blast furnace gas.

[0005] To solve the above technical problem, the technical solution adopted by the utility model is: it includes a purification device, a heating furnace, a pressure swing adsorption CO removal 2 device, a gas mixing device, an ammonia synthesis device, a urea synthesis device, an electrolysis device and a pressure swing adsorption H removal 2 device; the blast furnace gas output pipeline of the blast furnace is connected to the fuel inlet of the heating furnace after passing through the purification device, and the flue gas outlet of the heating furnace is connected to the inlet of the pressure swing adsorption CO removal 2 device; the N 2 outlet of the pressure swing adsorption CO removal 2 device is connected to the inlet of the ammonia synthesis device through the gas mixing device, and the liquid ammonia outlet of the ammonia synthesis device is connected to the liquid ammonia inlet of the urea synthesis device; the CO 2 outlet of the pressure swing adsorption CO removal 2 device is divided into two paths, one path is connected to the CO 2The inlet, and another inlet communicating with the electrolysis device; the syngas outlet of the electrolysis device communicates with the inlet of the pressure swing adsorption H removal device. 2 device, and the pressure swing adsorption H removal 2 device's H 2 outlet communicates with the H inlet of the gas mixing device. 2

[0006] Furthermore, the CO outlet of the pressure swing adsorption H removal 2 device communicates with the fuel gas inlet of the blast furnace.

[0007] Furthermore, the O outlet of the electrolysis device communicates with the heating furnace. 2

[0008] Furthermore, it further includes a first compressor, a second compressor, a third compressor, and a fourth compressor; the first compressor is arranged on the pipeline between the heating furnace and the pressure swing adsorption CO removal 2 device, the second compressor is arranged on the pipeline between the electrolysis device and the pressure swing adsorption H removal 2 device, the third compressor is arranged on the pipeline between the gas mixing device and the ammonia synthesis device, and the fourth compressor is arranged on the pipeline between the CO 2 outlet of the pressure swing adsorption CO removal 2 device and the CO 2 inlet of the urea synthesis device.

[0009] The beneficial effects of adopting the above technical solution are as follows: Without introducing other gas sources, various components in the blast furnace gas are maximally resourcefully utilized in the present utility model. Firstly, the blast furnace gas burns fully in the heating furnace to effectively utilize the energy contained therein; Secondly, the problem of a large amount of flue gas emissions caused by the combustion of the blast furnace gas is solved. Through the electrocatalytic technology of the pressure swing adsorption device, CO and H2O in part of the flue gas are converted into CO and H2, especially the CO is recycled to the blast furnace to reduce the coke ratio of the blast furnace; Finally, H2 is used to synthesize liquid ammonia with N2 in the flue gas, and the liquid ammonia is further used to synthesize the chemical product urea with CO in the flue gas. 2 and H 2 O are converted into CO and H 2 , especially the CO is recycled to the blast furnace to reduce the coke ratio of the blast furnace; Finally, H 2 is used to synthesize liquid ammonia with N 2 in the flue gas, and the liquid ammonia is further used to synthesize the chemical product urea with CO 2 in the flue gas.

[0010] The present invention not only solves the problem of difficult utilization of blast furnace gas, but also can produce high-value chemical products, reduce the coke ratio of the blast furnace, and bring economic benefits while contributing to carbon emission reduction in the steel industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The following further describes the present utility model in detail with reference to the drawings and specific embodiments.

[0012] Figure 1 is the system flow schematic diagram of the present utility model.​​ Detailed implementation mode

[0013] Figure 1 As shown, the system for producing urea using blast furnace gas includes a purification device, a heating furnace, a pressure swing adsorption CO removal 2 device, a gas mixing device, an ammonia synthesis device, a urea synthesis device, an electrolysis device, a pressure swing adsorption H removal 2 device and a compressor. The blast furnace gas output pipeline of the blast furnace is connected to the inlet of the purification device, the outlet of the purification device is connected to the fuel inlet of the heating furnace, and the flue gas outlet of the heating furnace is connected to the inlet of the pressure swing adsorption CO removal 2 device through a first compressor. The N 2 outlet of the pressure swing adsorption CO removal 2 device is connected to the N 2 inlet of the gas mixing device, the outlet of the gas mixing device is connected to the inlet of the ammonia synthesis device through a third compressor, and the liquid ammonia outlet of the ammonia synthesis device is connected to the liquid ammonia inlet of the urea synthesis device. The CO 2 outlet of the pressure swing adsorption CO removal 2 device is divided into two paths, one path is connected to the CO 2 inlet of the urea synthesis device through a fourth compressor, and the other path is connected to the inlet of the electrolysis device. The syngas outlet of the electrolysis device is connected to the inlet of the pressure swing adsorption H removal 2 device through a second compressor, the H 2 outlet of the pressure swing adsorption H removal 2 device is connected to the H 2 inlet of the gas mixing device, and the CO outlet of the pressure swing adsorption H removal 2 device is connected to the fuel gas inlet of the blast furnace. The O 2 outlet of the electrolysis device is connected to the O 2 inlet of the heating furnace. The H 2 O inlet of the electrolysis device is connected to the water supply pipeline.

[0014] The purification device of the system for producing urea using blast furnace gas includes 1 electrostatic precipitator and 2 desulfurization towers. The urea synthesis device includes a synthesis tower, a stripper, a decomposer, an evaporator and a granulation tower. A flow control valve is provided on the pipeline between the N 2 outlet of the pressure swing adsorption CO removal 2 device and the gas mixing device. A flow control valve is provided on the pipeline between the H 2 outlet of the pressure swing adsorption H removal 2 device and the gas mixing device.

[0015] As Figure 1 shown, the working process of the system for producing urea using blast furnace gas is as follows:

[0016] First, the top gas provided by the blast furnace is dust-removed by the electrostatic precipitator and desulfurized by the desulfurization tower in the purification device to meet the total sulfur of 1 ppm(V) in the gas. Subsequently, it enters the heating furnace as fuel gas to provide the heat required for the reaction of the ammonia synthesis and urea synthesis devices. O generated by the electrolysis device is sprayed into the heating furnace to make the blast furnace gas burn more fully. The flue gas generated by combustion consists of CO 2 and N 2 . The flue gas is pressurized and transported by the first compressor to the pressure swing adsorption CO 2 removal device to remove CO 2 . Part of the removed CO 2 enters the electrolysis device, and the other part of CO 2 is pressurized to 14 - 20 MPa by the fourth compressor and enters the urea synthesis device as raw material. The adsorbed tail gas N 2 enters the gas mixing device. 2

[0017] The CO 2 removed by the pressure swing adsorption CO 2 removal device and H 2 O are converted into syngas through electrocatalytic technology in the electrolysis device. The main components of the syngas are CO and H 2 . The syngas is pressurized to 2.5 MPa by the second compressor and enters the pressure swing adsorption H 2 removal device. The syngas is separated to obtain 99.5% H 2 . The high-purity tail gas CO is then recycled and sprayed into the blast furnace to reduce the coke ratio. The H 2 removed by the pressure swing adsorption H 2 removal device enters the gas mixing device and is fully mixed with the adsorbed tail gas N 2 from the pressure swing adsorption CO 2 removal device in the gas mixing device to obtain the syngas for ammonia synthesis with a molar ratio of H 2 to N 2 of 3:1. The syngas for ammonia synthesis is pressurized to 15 - 20 MPa by the third compressor and heated to 400 - 500 °C by the heating furnace and then enters the ammonia synthesis device to produce liquid ammonia with a purity of over 99.5%. The liquid ammonia is then transported to the urea synthesis device and reacts with CO 2 from the fourth compressor at 14 - 20 MPa and 190 - 220 °C. Subsequently, it undergoes steps such as stripping, decomposition, evaporation, and granulation to produce urea products.

[0018] To control the molar ratio of H 2 to N 2 in the gas mixing device to be 3:1, it is necessary to install flow meters on the N 2 output pipeline of the pressure swing adsorption CO 2 removal device and the H 2 output pipeline of the pressure swing adsorption H 2 ​A flow control valve is installed in the output pipeline, which can be adjusted during production.

Claims

1. A system for producing urea using blast furnace gas, characterized in that: It includes a purification device, a heating furnace, a pressure swing adsorption de-CO2 device, a gas mixing device, an ammonia synthesis device, a urea synthesis device, an electrolysis device and a pressure swing adsorption de-H2 device; the blast furnace gas output pipeline of the blast furnace is connected to the fuel inlet of the heating furnace after passing through the purification device, and the flue gas outlet of the heating furnace is connected to the inlet of the pressure swing adsorption de-CO2 device; the N2 outlet of the pressure swing adsorption de-CO2 device is connected to the inlet of the ammonia synthesis device through the gas mixing device, and the liquid ammonia outlet of the ammonia synthesis device is connected to the liquid ammonia inlet of the urea synthesis device; the CO2 outlet of the pressure swing adsorption de-CO2 device is divided into two paths, one path is connected to the CO2 inlet of the urea synthesis device, and the other path is connected to the inlet of the electrolysis device; the synthesis gas outlet of the electrolysis device is connected to the inlet of the pressure swing adsorption de-H2 device, and the H2 outlet of the pressure swing adsorption de-H2 device is connected to the H2 inlet of the gas mixing device.

2. A system for producing urea using blast furnace gas according to claim 1, characterized in that: The CO outlet of the pressure swing adsorption H2 removal device is connected to the fuel gas inlet of the blast furnace.

3. The system for producing urea by utilizing blast furnace gas according to claim 1, characterized in that: The O2 outlet of the electrolysis device is connected to the heating furnace.

4. A system for producing urea using blast furnace gas according to claim 1, 2 or 3, characterized in that: It also includes compressor No. 1, compressor No. 2, compressor No. 3 and compressor No. 4; compressor No. 1 is arranged on the pipeline between the heating furnace and the pressure swing adsorption de-CO2 device, compressor No. 2 is arranged on the pipeline between the electrolysis device and the pressure swing adsorption de-H2 device, compressor No. 3 is arranged on the pipeline between the gas mixing device and the synthetic ammonia device, and compressor No. 4 is arranged on the pipeline between the CO2 outlet of the pressure swing adsorption de-CO2 device and the CO2 inlet of the urea synthesis device.

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