阅读说明：本技术 一种低温甲醇洗工艺流程中使用的减压节能方法及系统 (Pressure reduction and energy saving method and system used in low-temperature methanol washing process flow ) 是由 孙金菊 孙山 宋鹏 于 2021-01-29 设计创作，主要内容包括：本发明公开了一种低温甲醇洗工艺流程中使用的减压节能方法及系统,包括以下步骤：吸收塔下端输出的高压低温富甲醇溶液进入到液体膨胀机中,通过液体膨胀机将高压低温富甲醇溶液的压力能转换为动能,然后排入下游解析塔中,该方法及系统减少富甲醇溶液流经吸收塔与解析塔之间时减压过程中的酸性气体的析出量,同时降低高压液体节流过程的压力头耗散对系统性能的影响。(The invention discloses a pressure reduction and energy saving method and a system used in a low-temperature methanol washing process flow, which comprises the following steps: the method and the system reduce the precipitation amount of acid gas in the pressure reduction process when the methanol-rich solution flows between the absorption tower and the desorption tower, and simultaneously reduce the influence of pressure head dissipation in the throttling process of the high-pressure liquid on the system performance.)

1. A pressure reduction and energy saving method used in a low-temperature methanol washing process flow is characterized by comprising the following steps: the high-pressure low-temperature methanol-rich solution output from the lower end of the absorption tower (5) enters a liquid expansion machine (4), the pressure energy of the high-pressure low-temperature methanol-rich solution is converted into kinetic energy through the liquid expansion machine (4), and then the kinetic energy is discharged into a downstream desorption tower (6).

2. The reduced-pressure energy-saving method used in the low-temperature methanol washing process flow according to claim 1, which is characterized by comprising the following steps:

the high-pressure low-temperature methanol-rich solution output from the lower end of the absorption tower (5) enters a volute of a liquid expansion machine (4), is uniformly distributed in a nozzle ring, and then is expanded and accelerated in an adjustable spray nozzle in the liquid expansion machine (4), so that the pressure energy of the high-pressure low-temperature methanol solution is converted into kinetic energy to push an impeller in the liquid expansion machine (4) to rotate, and the methanol solution output from the liquid expansion machine (4) enters a desorption tower (6).

3. The pressure reduction energy-saving device used in the low-temperature methanol washing process flow is characterized by being arranged between an absorption tower (5) and an analysis tower (6) and comprising a throttling valve (1), a liquid expansion machine (4), a first stop valve (21) and a second stop valve (22), wherein an outlet at the lower end of the absorption tower (5) is divided into two paths, one path is communicated with one end of the first stop valve (21), the other path is connected with one end of the throttling valve (1), the other end of the first stop valve (21) is communicated with an inlet of the liquid expansion machine (4), an outlet of the liquid expansion machine (4) is communicated with one end of the second stop valve (22), and the other end of the second stop valve (22) is communicated with an inlet of the analysis tower (6) after being connected with the other end of the throttling valve (1) through a pipeline in parallel.

4. The pressure reduction and energy saving device used in the low-temperature methanol washing process flow according to claim 3, wherein the output shaft of the liquid expander (4) is connected with a generator (3) or a power plant.

5. A pressure reduction and energy saving device used in a low temperature methanol washing process flow according to claim 3, characterized by further comprising a cold box, wherein the liquid expander (4) is located in the cold box.

6. The pressure reduction and energy conservation device used in the low-temperature methanol washing process flow according to claim 5, wherein the side wall of the cooling box is provided with a heat insulation layer.

Technical Field

The invention belongs to the technical field of synthesis gas purification in coal chemical industry, and relates to a pressure reduction and energy saving method and system used in a low-temperature methanol washing process flow.

Background

With the development of industry and the improvement of people's living standard of matter, the demand of energy is increasing day by day. Coal is the most abundant fossil resource in the world and is also the most widespread fossil fuel. Coal chemical industry is one of the important bridges for the transition from fossil energy to clean energy because fossil energy such as coal inevitably pollutes the environment when in use. The coal-to-oil, coal-to-gas and integrated gasification combined cycle power generation system can convert stone fuels such as cheap coal and the like into clean synthetic gas (hydrogen, carbon monoxide and the like) for producing liquid fuel or generating power. A key step in the syngas conversion process is the removal of acid gases (CO2, H2S, COs, etc.) that are detrimental to the downstream catalyst.

The low-temperature methanol washing process takes cold methanol as an absorption solvent, utilizes the excellent characteristic that the methanol has great solubility to acid gas at low temperature and high pressure, removes the acid gas in the raw material gas, and is a physical absorption method. The process is the most economic and high-purification-degree gas purification technology which is recognized at home and abroad at present, has the characteristics of good quality of purified gas, high purification degree, selective absorption of H2S, COS and CO2, low price and easy obtainment of a solvent, low energy consumption, low operation cost, stable and reliable production and operation and the like. The process generally comprises one absorption column and a plurality of stripping columns. In the traditional methanol washing process, high-pressure low-temperature methanol solution absorbs acid gas in an absorption tower, a high-pressure rich solution solvent is throttled and decompressed to meet the process requirement through a throttle valve and then is guided into a downstream analysis tower for decomposition, then the acid gas is collected and stored, and lean solution methanol is returned to the absorption tower, so that the aim of recycling the methanol is fulfilled.

In this process, the high-pressure methanol-rich solution achieves throttling and pressure reduction through the throttle valve, but at the same time a huge high-pressure head dissipates into the system in the form of heat energy, which entails the following problems:

1) in the methanol washing process flow, the absorption tower and the analysis tower generally operate at the temperature of-30 to-50 ℃, and the energy efficiency of the whole system is inevitably reduced when pressure heads with dozens of atmospheric pressures are dissipated in the methanol washing process flow in the form of heat energy;

2) mechanical energy with dozens of atmospheres of pressure is dissipated in the methanol washing process flow in the form of heat energy, so that the temperature of the methanol-rich solution is increased, the absorption capacity of the methanol solvent to acid gas is reduced, and the improvement of the acid gas purification capacity of the whole methanol washing process flow is not facilitated;

3) the need to improve the sealing of the relevant components to prevent the large scale of acid gas evolution in the lines outside the absorber and stripper increases the construction and maintenance costs of the methanol wash process.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a pressure reduction and energy saving method and a pressure reduction and energy saving system used in a low-temperature methanol washing process flow, which reduce the precipitation amount of acid gas in the pressure reduction process when a methanol-rich solution flows between an absorption tower and an analysis tower and reduce the influence of the pressure head dissipation of a high-pressure liquid throttling process on the system performance.

In order to achieve the purpose, the pressure reduction and energy saving method used in the low-temperature methanol washing process flow comprises the following steps: the high-pressure low-temperature methanol-rich solution output from the lower end of the absorption tower enters a liquid expander, the pressure energy of the high-pressure low-temperature methanol-rich solution is converted into kinetic energy through the liquid expander, and then the kinetic energy is discharged into a downstream desorption tower.

The method specifically comprises the following steps:

the high-pressure low-temperature methanol-rich solution output from the lower end of the absorption tower enters a volute of a liquid expansion machine and is uniformly distributed in a nozzle ring, then expansion acceleration is carried out in an adjustable nozzle in the liquid expansion machine, the pressure energy of the high-pressure low-temperature methanol solution is converted into kinetic energy to push an impeller in the liquid expansion machine to rotate, and the methanol solution output from the liquid expansion machine enters an analytical tower.

A pressure reduction energy-saving device used in a low-temperature methanol washing process flow is arranged between an absorption tower and an analysis tower and comprises a throttling valve, a liquid expansion machine, a first stop valve and a second stop valve, wherein an outlet at the lower end of the absorption tower is divided into two paths, one path of the outlet is communicated with one end of the first stop valve, the other path of the outlet is connected with one end of the throttling valve, the other end of the first stop valve is communicated with an inlet of the liquid expansion machine, an outlet of the liquid expansion machine is communicated with one end of the second stop valve, and the other end of the second stop valve is communicated with an inlet of the analysis tower after being communicated with the other end of the throttling valve through.

The output shaft of the liquid expansion machine is connected with a generator or power equipment.

The liquid expansion machine is positioned in the cold box.

And a heat insulation layer is arranged on the side wall of the cold box.

The invention has the following beneficial effects:

when the pressure reducing and energy saving method and the pressure reducing and energy saving system used in the low-temperature methanol washing process flow are specifically operated, the pressure reducing and throttling effect of the high-pressure low-temperature methanol-rich solution is utilized, so that the pressure head of the methanol-rich solution entering the liquid expansion machine is accelerated by the nozzle, and the pressure energy and the kinetic energy are converted into mechanical energy in the impeller, thereby realizing the pressure reducing and energy saving benefits, simultaneously avoiding the large-scale separation of acid gas caused by the temperature rise of the methanol-rich solution in the pressure reducing and throttling process, improving the removal performance of the methanol washing process flow on the acid gas, and improving the unit energy consumption output of the system. In addition, the liquid expansion machine is connected with the throttle valve in parallel, so that the temperature of the methanol-rich solution is reduced in the throttling and pressure reducing processes, the cavitation flow generated by large-scale precipitation of acid gas due to temperature rise in the pressure reducing and throttling processes is avoided, the absorption capacity of the methanol solution on the acid gas can be effectively improved, and the unit energy consumption and output of the system are improved.

Drawings

FIG. 1 is a block diagram of a methanol wash process;

fig. 2 is a schematic structural diagram of the present invention.

Wherein, 1 is a throttle valve, 21 is a first stop valve, 22 is a second stop valve, 3 is a generator, 4 is a liquid expander, 5 is an absorption tower, 6 is an analysis tower, 7 is a concentration tower, 8 is a regeneration tower, 9 is a separation tower, and 10 is a methanol pump.

Detailed Description

The invention is described in further detail below with reference to the accompanying drawings:

the pressure reduction and energy saving method used in the low-temperature methanol washing process flow comprises the following steps: the high-pressure low-temperature methanol-rich solution output from the lower end of the absorption tower 5 is input into the liquid expander 4, and the pressure energy of the high-pressure low-temperature methanol-rich solution is converted into kinetic energy through the liquid expander 4.

The method specifically comprises the following steps: the high-pressure low-temperature methanol-rich solution output from the lower end of the absorption tower 5 enters a volute of the liquid expander 4 and is uniformly distributed in a nozzle ring, then expansion acceleration is carried out in an adjustable nozzle in the liquid expander 4, the pressure energy of the high-pressure low-temperature methanol solution is converted into kinetic energy to push an impeller in the liquid expander 4 to rotate, and the methanol solution output from the liquid expander 4 enters the desorption tower 6.

Referring to fig. 1 and 2, the pressure-reducing energy-saving device used in the low-temperature methanol washing process flow of the present invention is installed between an absorption tower 5 and an analytical tower 6, and includes a throttle valve 1, a liquid expander 4, a first stop valve 21 and a second stop valve 22, wherein an outlet at a lower end of the absorption tower 5 is divided into two paths, one path of the two paths is communicated with one end of the first stop valve 21, the other path is connected with one end of the throttle valve 1, the other end of the first stop valve 21 is communicated with an inlet of the liquid expander 4, an outlet of the liquid expander 4 is communicated with one end of the second stop valve 22, the other end of the second stop valve 22 is communicated with an inlet of the analytical tower 6 after being connected with the other end of the throttle valve 1 through a pipeline, and an output shaft of the liquid expander 4 is connected with a.

The invention also comprises a cold box, wherein the liquid expander 4 is positioned in the cold box; and a heat insulation layer is arranged on the side wall of the cold box.

During specific work, when the methanol washing process flow in the prior operation runs stably, the throttle valve 1 is closed, the first stop valve 21 and the second stop valve 22 are opened, the liquid expansion machine 4 runs stably, and the generator 3 is dragged to reach the grid-connected power generation rotating speed, and the specific process is as follows:

first, the high-pressure low-temperature lean methanol solvent purifies the raw material gas in the absorption tower 5 to absorb the acid gas (H)₂S, COS and CO₂Etc.) and collected as the methanol-rich solution at the lower section of the absorption tower 5, then the methanol-rich solution is led out from the lower end of the absorption tower 5, led into the volute to be uniformly distributed on the nozzle ring, then the methanol-rich solution is expanded and accelerated in the adjustable nozzle, the pressure energy is converted into kinetic energy to push the impeller of the liquid expander 4 to rotate at high speed, then the pressure energy and the kinetic energy are converted into the rotating mechanical energy of the rotor and output shaft work, finally the methanol-rich solution flows out of the diffuser pipe, and the methanol-rich solution reaching the pressure required by the methanol washing process flow enters the downstream resolution tower 6.

The above description is only a preferred embodiment of the present invention and does not limit the scope of the present invention, and those skilled in the art should cover the modifications of the equivalent forms in the disclosure of the present invention.