Energy-saving preheating system for preparing methanol from coke-oven gas

Abstract

The utility model discloses an energy-saving preheating system for preparing methanol from coke-oven gas, which comprises a gas delivery pipe, the end part of the gas delivery pipe is communicated with a tube pass inlet of a preheater, a tube pass outlet of the preheater is sequentially connected with a converter of a mixer, and superheated steam inlets are arranged at the tops of the mixer and the converter. An air outlet of the converter is sequentially connected with a first waste heat recoverer and a second waste heat recoverer, low-temperature steam outlets in the first waste heat recoverer and the second waste heat recoverer are connected with a steam superheater through steam pipelines, and an outlet of the steam superheater is communicated with a superheated steam inlet through a circulation pipeline. A gas outlet of the second waste heat recoverer is communicated with a shell pass inlet of the preheater, and a shell pass outlet of the preheater is sequentially connected with a cooler and a methanol synthesizer through a gas guide pipe. According to the device, the use quantity of subsequent waste heat recovery can be remarkably reduced, efficient recovery of waste heat is achieved, cyclic utilization of the waste heat can be achieved, and a good energy-saving effect is achieved.

Description

Technical Field

[0001] This utility model belongs to the field of deep processing technology of coke oven gas, specifically relating to an energy-saving coke oven gas to methanol preheating system. Background Technology

[0002] Coke oven gas is a combustible gas produced during the coking process. Its main components are hydrogen and methane, accounting for 56% and 27% respectively, with small amounts of carbon monoxide, carbon dioxide, nitrogen, oxygen, and other hydrocarbons. Besides its uses as domestic and industrial fuel, for power generation, direct reduction of iron as a reducing agent, and hydrogen production via pressure swing adsorption, coke oven gas can also be used as a raw material to produce high-value-added chemical products such as nitrogen fertilizer, methanol, dimethyl ether, natural gas, and fuel oil. Currently, methanol production from coke oven gas is one of the most ideal ways to increase its added value. The process for producing methanol from coke oven gas mainly includes the following steps: Gas holder buffering: After arriving from the coking plant, the coke oven gas first enters a gas holder for buffering and pressure stabilization to ensure a stable gas supply; Coke oven gas compression: The buffered coke oven gas enters a compressor for compression, increasing the pressure to 2.5 MPa and the temperature to approximately 40°C; Fine desulfurization: The compressed coke oven gas enters a fine desulfurization unit to remove impurities. Organic and inorganic sulfur are controlled to ensure the total sulfur content is below 0.1 ppm to meet the requirements of subsequent conversion catalysts. Conversion: The desulfurized coke oven gas enters the conversion unit, where it undergoes a pressurized catalytic partial oxidation reaction to convert methane and higher carbon hydrocarbons into hydrogen and carbon monoxide. These gases are the effective components for methanol synthesis. Syngas Compression: The converted gas is pressurized by a syngas compressor and then sent to the methanol synthesis tower for the synthesis reaction. Methanol Synthesis: In the methanol synthesis tower, hydrogen and carbon monoxide are synthesized into methanol under the action of a catalyst. The resulting crude methanol is purified by distillation to obtain high-grade refined methanol that meets national standards. Tail Gas Treatment: The off-gas and tail gas generated during the synthesis process are treated; part of it is used as fuel, and the other part is recycled. In the aforementioned coke oven gas to methanol process, superheated steam is introduced to heat the coke oven gas during the conversion process to promote the conversion. After being heated by superheated steam, the coke oven gas has a high temperature and needs to be cooled multiple times before the methanol synthesis reaction can proceed. This not only results in a significant waste of heat energy but also leads to low conversion efficiency due to uneven preheating of the coke oven gas. Therefore, it is objectively necessary to develop an energy-saving coke oven gas to methanol preheating system with a reasonable process design that can improve both conversion efficiency and heat recovery rate. Summary of the Invention

[0003] The purpose of this utility model is to provide an energy-saving preheating system for methanol production from coke oven gas that has a reasonable process design and can improve both conversion efficiency and heat recovery rate.

[0004] The purpose of this utility model is achieved as follows: It includes a gas delivery pipe, the end of which is connected to the tube-side inlet of a preheater. The tube-side outlet of the preheater is sequentially connected to a converter of a mixer. Both the mixer and the converter have superheated steam inlets at their tops. The outlet of the converter is sequentially connected to a first waste heat recovery unit and a second waste heat recovery unit. The first and second waste heat recovery units have low-temperature steam outlets. The low-temperature steam outlets are connected to a steam superheater via a steam pipeline. The outlet of the steam superheater is connected to the superheated steam inlet via a circulation pipeline. The outlet of the second waste heat recovery unit is connected to the shell-side inlet of the preheater. The shell-side outlet of the preheater is sequentially connected to a cooler and a methanol synthesizer via a gas guide pipe.

[0005] Compared with existing technologies, the advantages of this system are as follows: This system optimizes the structure between coke oven gas conversion and synthesis. A first and second waste heat recovery unit are installed between the converter and preheater. These two units can recover waste heat from the converted gas. The first and second preheaters efficiently cool the converted gas, reducing the processing burden on subsequent preheaters and coolers. This streamlines the gas processing flow, accelerates the cooling rate, and improves production efficiency and coke oven gas conversion efficiency. Simultaneously, the low-temperature steam generated by the first and second waste heat recovery units, after being reheated by a steam superheater, can be returned to the mixer and converter for reuse. This achieves waste heat recycling, reducing energy consumption. This system features a simple processing flow, high conversion efficiency, and low energy consumption, making it easy to promote and use. Attached Figure Description

[0006] Figure 1 This is a schematic diagram of the overall structure of this utility model;

[0007] Figure 2 This is a schematic diagram of the structure of the first waste heat recovery unit 7 in this utility model;

[0008] In the diagram: 1-Gas transmission pipe, 2-Preheater, 3-Mixer, 4-Converter, 5-Superheated steam inlet, 6-First waste heat recovery unit, 61-Upper tank, 62-Lower tank, 63-Intermediate partition, 64-Heat exchange chamber, 65-Steam storage chamber, 66-Water inlet pipe, 67-Steam pipe, 68-Heat exchange pipe, 69-Heat exchange fins, 610-Support shaft, 611-Breakthrough blades, 612-Steam cap, 7-Second waste heat recovery unit, 8-Low-temperature steam outlet, 9-Steam superheater, 10-Cooler, 11-Methanol synthesizer, 12-Buffer tank. Detailed Implementation

[0009] The present invention will be further described below with reference to the accompanying drawings, but this description is not intended to limit the present invention in any way. Any changes or improvements made based on the teachings of the present invention shall fall within the protection scope of the present invention.

[0010] like Figure 1-2 As shown, this utility model includes a gas supply pipe 1, the end of which is connected to the tube-side inlet of a preheater 2. The preheater 2 is a structure used in the prior art, mainly employing a shell-and-tube heat exchanger structure. The tube-side outlet of the preheater 2 is sequentially connected to a converter 4 of a mixer 3. The mixer 3 and converter 4 adopt a structure used in the prior art. Both the mixer 3 and converter 4 are provided with superheated steam inlets 5 at their tops. The outlet of the converter 4 is sequentially connected to a first waste heat recovery unit 6 and a second waste heat recovery unit 7. The first waste heat recovery unit... The recovery unit 6 and the second waste heat recovery unit 7 are provided with a low-temperature steam outlet 8. The low-temperature steam outlet 8 is connected to a steam superheater 9 through a steam pipeline. The outlet of the steam superheater 9 is connected to the superheated steam inlet 5 through a circulation pipeline. The outlet of the second waste heat recovery unit 7 is connected to the shell-side inlet of the preheater 2. The shell-side outlet of the preheater 2 is connected to a cooler 10 and a methanol synthesizer 11 in sequence through a gas guide pipe. The cooler 10 adopts the shell-and-tube heat exchanger used in the prior art, and the methanol synthesizer is the structure used in the prior art.

[0011] The working process of this system is as follows: Coke oven gas, after being preheated by preheater 2, first enters mixer 3. Superheated steam is then supplied to mixer 3 through superheated steam inlet 5. The superheated steam mixes with the coke oven gas in mixer 3 and then enters converter 4. Superheated steam is again supplied to converter 4 through superheated steam inlet 5. The superheated steam and coke oven gas undergo a catalytic reaction in converter 4 to form converted gas. The converted gas is first cooled by the first waste heat recovery unit 6, and then cooled a second time in the second waste heat recovery unit 7. After the second cooling, the converted gas enters preheater 2 to preheat the coke oven gas. After absorbing heat, the coke oven gas's temperature rises and it enters mixer 3. The converted gas in preheater 2, after absorbing heat from the coke oven gas, reaches a temperature... The temperature of the converted gas is reduced again. After a second cooling process, the gas enters the preheater 2 and then the cooler 10 to reach the required synthesis temperature. It can then enter the methanol synthesizer 11 for synthesis. During this process, the low-temperature steam generated by the converted gas after exchanging heat with cooling water in the first waste heat recovery unit 6 and the second waste heat recovery unit 7 is reheated by the steam superheater 9 and can be returned to the mixer 3 and the converter 4 for reuse. This enables the recycling of waste heat, further improving the utilization rate of waste heat and achieving better energy-saving effects. At the same time, the converted gas cooled by the second waste heat recovery unit 7 enters the preheater 2 to preheat the coke oven gas, which can further improve the utilization rate of waste heat and reduce the energy consumption of the system.

[0012] In order to ensure that the flow and pressure of the conversion gas entering the methanol synthesizer 11 are stable and uniform, a buffer tank 12 is provided on the gas guide pipe between the cooler 10 and the methanol synthesizer 11. The structure of the buffer tank 12 can adopt the structure of the gas buffer tank used in the prior art.

[0013] To achieve efficient recovery of waste heat from the converted gas and realize better energy-saving effects, the first waste heat recovery unit 6 and the second waste heat recovery unit 7 have the same structure. The first waste heat recovery unit 6 includes an upper tank 61 and a lower tank 62. A middle partition 63 is horizontally installed in the upper part of the first waste heat recovery unit 6, which divides the inner cavity of the first waste heat recovery unit 6 into a heat exchange chamber 64 and a steam storage chamber 65. The lower tank 62 is fixedly installed in the lower part of the heat exchange chamber 64, and the upper tank 61 is fixedly installed in the upper part of the heat exchange chamber 64. Two rows of heat exchange tube bundles are symmetrically arranged on both sides of the upper tank 61 and the lower tank 62. One end of the lower tank 62 is connected to a water inlet pipe 66. The top of the upper tank 61 is provided with multiple steam pipes 67 communicating with the steam storage chamber 65. The low-temperature steam outlet 8 is located at the top of the steam storage chamber 65. In use, the converted gas enters the heat exchange chamber 64, and cooling water is simultaneously delivered to the lower tank 62 through the water inlet pipe 66. After entering the heat exchange chamber 64, the cooling water that has entered the lower tank 62 is evenly distributed within it. The heat exchange tube bundle absorbs heat from the converted gas, heating the cooling water. This heated cooling water then enters the upper tank 61. Heated by the converted gas, it generates low-temperature steam. This low-temperature steam enters the steam storage chamber 65 through the steam pipe 67 and is then discharged through the low-temperature steam outlet 8. The converted gas, after absorbing heat from the cooling water... After the temperature drops, it will be discharged from the heat exchange chamber 64. In order to improve the heat exchange effect and increase the heat exchange area between the converted gas and the cooling water, each row of heat exchange tube bundles includes multiple heat exchange tubes 68 arranged at equal intervals. The multiple heat exchange tubes 68 are arranged along the axial direction of the upper tank 61 and the lower tank 62, and the heat exchange tubes 68 of adjacent rows of heat exchange tube bundles are staggered. Heat exchange fins 69 are installed on the heat exchange tubes 68. The heat exchange fins 69 can achieve a better heat transfer effect and improve the efficient recovery of waste heat from the converted gas.

[0014] Furthermore, in order to prolong the uniform contact between the converted gas and the cooling water in the heat exchange chamber 64, multiple turbulence-inducing components are installed at equal intervals along the axial direction between the upper tank 61 and the lower tank 62 between the heat exchange tube bundles. The turbulence-inducing components include a support shaft 610 fixedly installed between the upper tank 61 and the lower tank 62. Multiple bushings are installed at equal intervals along the axial direction on the support shaft 610. Multiple turbulence-inducing blades 611 are evenly distributed on each bushing. After the converted gas enters the heat exchange chamber 64, it will impact the turbulence-inducing blades 611. The turbulence-inducing blades 611 will rotate when impacted. During the rotation, the converted gas will be agitated. The agitated converted gas will be evenly distributed in the heat exchange chamber 64, so that it can evenly contact the heat exchange tubes 68 and achieve a better heat exchange effect.

[0015] Furthermore, in order to reduce the moisture content of the low-temperature steam, a gas-liquid separation component is installed inside the steam pipe 67. The top of the steam pipe 67 extends into the steam storage chamber 65, and a steam cap 612 is installed on the top of the steam pipe 67. Multiple steam outlet holes are evenly distributed on the steam cap 612. The gas-liquid separation component can separate the low-temperature steam into gas and liquid, preventing excessive moisture in the low-temperature steam from entering the steam storage chamber 65. This can reduce the moisture content of the low-temperature steam and improve the efficiency of coke oven gas conversion.

Claims

1. An energy-saving preheating system for methanol production from coke oven gas, comprising a gas transmission pipe (1), characterized in that: The end of the gas pipeline (1) is connected to the tube inlet of the preheater (2). The tube outlet of the preheater (2) is connected to a mixer (3) and a converter (4) in sequence. The top of the mixer (3) and the converter (4) are provided with superheated steam inlets (5). The outlet of the converter (4) is connected to a first waste heat recovery unit (6) and a second waste heat recovery unit (7) in sequence. The first waste heat recovery unit (6) and the second waste heat recovery unit (7) are provided with low-temperature steam outlets (8). The low-temperature steam outlets (8) are connected to a steam superheater (9) through a steam pipeline. The outlet of the steam superheater (9) is connected to the superheated steam inlet (5) through a circulation pipeline. The outlet of the second waste heat recovery unit (7) is connected to the shell inlet of the preheater (2). The shell outlet of the preheater (2) is connected to a cooler (10) and a methanol synthesizer (11) in sequence through a gas guide pipe.

2. The energy-saving coke oven gas to methanol preheating system according to claim 1, characterized in that: A buffer tank (12) is installed on the gas duct between the cooler (10) and the methanol synthesizer (11).

3. The energy-saving coke oven gas to methanol preheating system according to claim 1, characterized in that: The first waste heat recovery unit (6) and the second waste heat recovery unit (7) have the same structure.

4. The energy-saving coke oven gas to methanol preheating system according to claim 1, characterized in that: The first waste heat recovery unit (6) includes an upper tank (61) and a lower tank (62). A middle partition (63) is horizontally installed in the upper part of the first waste heat recovery unit (6). The middle partition (63) divides the inner cavity of the first waste heat recovery unit (6) into a heat exchange chamber (64) and a steam storage chamber (65). The lower tank (62) is fixedly installed in the lower part of the heat exchange chamber (64). The upper tank (61) is fixedly installed in the upper part of the heat exchange chamber (64). Two rows of heat exchange tube bundles are symmetrically arranged on both sides of the upper tank (61) and the lower tank (62). One end of the lower tank (62) is connected to a water inlet pipe (66). The top of the upper tank (61) is provided with multiple steam pipes (67) communicating with the steam storage chamber (65). The low-temperature steam outlet (8) is located at the top of the steam storage chamber (65).

5. The energy-saving coke oven gas to methanol preheating system according to claim 4, characterized in that: Each row of heat exchange tube bundles includes multiple heat exchange tubes (68) arranged at equal intervals. The multiple heat exchange tubes (68) are arranged along the axial direction of the upper tank (61) and the lower tank (62), and the heat exchange tubes (68) of adjacent rows of heat exchange tube bundles are arranged alternately.

6. The energy-saving coke oven gas to methanol preheating system according to claim 5, characterized in that: The heat exchange tube (68) is equipped with heat exchange fins (69).

7. The energy-saving coke oven gas to methanol preheating system according to claim 4, characterized in that: Multiple turbulence-inducing components are installed at equal intervals along their axial direction between the upper tank (61) and the lower tank (62) between the heat exchange tube bundles.

8. The energy-saving coke oven gas to methanol preheating system according to claim 7, characterized in that: The turbulence-disrupting assembly includes a support shaft (610) fixedly installed between the upper tank (61) and the lower tank (62). Multiple bushings are installed at equal intervals along the axial direction on the support shaft (610), and multiple turbulence-disrupting blades (611) are evenly distributed on each bushing.

9. The energy-saving coke oven gas to methanol preheating system according to claim 4, characterized in that: The steam pipe (67) is equipped with a gas-liquid separation component inside. The top of the steam pipe (67) extends into the steam storage chamber (65). A steam cap (612) is installed on the top of the steam pipe (67), and multiple steam outlet holes are evenly distributed on the steam cap (612).

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