Coal milling nitrogen pressure difference energy utilization device

Abstract

The utility model discloses a coal grinding nitrogen differential pressure energy utilization device, which comprises a coal grinding device and a nitrogen source, and is characterized in that the device further comprises a pressure reduction refrigeration generator and a nitrogen rewarming heat exchanger, low-pressure nitrogen from the nitrogen source enters the pressure reduction refrigeration generator, and the nitrogen after pressure reduction enters the nitrogen rewarming heat exchanger as low-temperature fluid; entering a coal grinding device after heat exchange; high-temperature fluid of the nitrogen rewarming heat exchanger is synthesis gas generated by coal gasification reaction, and the synthesis gas is cooled by the nitrogen rewarming heat exchanger, then enters the circulating water cooler, is cooled to normal temperature and then enters the low-temperature methanol washing device. When the differential pressure energy is utilized to generate power, a low-temperature cold source is obtained to cool the process gas, so that the thermal load of circulating water for cooling the process gas can be reduced, the temperature of nitrogen entering a coal milling system can be increased, the fuel consumption is reduced, and the effects of comprehensively utilizing energy, saving energy and reducing consumption are achieved.

Description

Technical Field

[0001] This utility model belongs to the field of coal gasification technology, specifically relating to a device for utilizing nitrogen pressure difference energy in coal milling. Background Technology

[0002] Coal-water slurry gasification uses coal-water slurry as raw material, which reacts with oxygen in a gasifier to achieve a high carbon conversion rate. Before pulverized coal gasification, the raw coal needs to be ground into pulverized coal. In the coal grinding section, the raw coal with a moisture content of 15%-20% needs to be heated through a mill and hot blast stove to control the moisture content of the pulverized coal to less than 5%. The water vapor removed by the hot blast stove is circulated by the circulating fan. To control the dew point of the coal grinding system and prevent water vapor accumulation and condensation, a portion of the circulating air needs to be continuously discharged. During the discharge process, nitrogen needs to be added to maintain stable system pressure.

[0003] The nitrogen source in the plant is low-pressure, ambient-temperature nitrogen at a pressure of 0.5 MPa. The outlet pressure of the coal mill circulating fan is 2 kPa. The nitrogen needs to be introduced into the coal mill through a pressure reducing agent as a supplement to the coal mill exhaust gas. Due to the high total water content of the raw coal, the amount of circulating air discharged from the mill is considerable.

[0004] On the other hand, the reaction of raw coal and oxygen in the gasifier produces CO2 gas, which is removed by low-temperature methanol washing. Before removal, the high-temperature crude syngas from coal gasification is cooled. The coal gasification process is a high-temperature and high-pressure process. Before entering the low-temperature methanol washing system, the gas needs to be cooled by heat recovery to become room-temperature gas. After heat recovery, the heat load of the circulating water in the syngas heat exchange process is high, and the evaporation loss of water in the cooling tower is relatively large. Summary of the Invention

[0005] The purpose of this invention is to provide a device for utilizing nitrogen pressure difference in coal milling, which solves the problem of nitrogen pressure difference loss in coal milling. By reducing the pressure of nitrogen for cooling and power generation, a low-temperature cold source is obtained to cool the process gas while outputting electricity, thus achieving comprehensive energy utilization of the coal gasification device and realizing the effect of energy saving and consumption reduction.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] A coal mill nitrogen pressure difference energy utilization device includes a coal milling device and a nitrogen source. The device further includes a reduced-pressure refrigeration generator and a nitrogen reheating heat exchanger. Low-pressure nitrogen from the nitrogen source enters the reduced-pressure refrigeration generator. After pressure reduction, the nitrogen, as a low-temperature fluid, enters the nitrogen reheating heat exchanger and, after heat exchange, enters the coal milling device. The high-temperature fluid in the nitrogen reheating heat exchanger is syngas produced by coal gasification. After being cooled by the nitrogen reheating heat exchanger, it enters a circulating water cooler and, after being reduced to ambient temperature, enters a low-temperature methanol washing device.

[0008] Furthermore, in the aforementioned reduced-pressure refrigeration generator, low-pressure nitrogen gas expands and depressurizes to perform work and drives a turbine to generate electricity.

[0009] Furthermore, the nitrogen reheating heat exchanger is a partition wall heat exchanger, preferably a fixed tube sheet heat exchanger with an expansion joint.

[0010] Furthermore, the synthesis gas is sequentially passed through a steam boiling pot and a demineralized water heat exchanger before entering a nitrogen reheating heat exchanger; finally, it enters a low-temperature methanol washing unit after passing through a circulating water cooler.

[0011] Furthermore, the pressure of the low-pressure nitrogen gas is 0.4-0.8 MPa, and after being reduced by the pressure-reducing refrigeration generator, it is 3-6 kPa.

[0012] Furthermore, after heat exchange via a nitrogen reheating heat exchanger, the temperature of the nitrogen is controlled at 40–80°C.

[0013] Beneficial effects: The coal mill nitrogen pressure difference energy utilization device of this utility model can generate electricity by utilizing pressure difference energy, while reducing a large amount of circulating water heat load and increasing the nitrogen temperature entering the coal mill system, thereby reducing fuel consumption.

[0014] 1. Replace the nitrogen pressure reducing valve with a pressure-reducing refrigeration generator to make full use of pressure difference energy.

[0015] 2. The nitrogen gas pressure reducing generator outputs electrical energy, and 150-200 kWh of electricity can be recovered for every 10,000 cubic meters of nitrogen.

[0016] 3. The nitrogen gas vacuum generator outlet can obtain low-temperature, low-pressure nitrogen gas at around -20℃. This gas can be used to cool the process gas, thereby reducing the amount of circulating water used or cooling the circulating water.

[0017] 4. After heat exchange of demineralized water, the process gas temperature is 70-110℃, and the nitrogen temperature after pressure reduction is about -20℃. The nitrogen flow rate is 10% of the total process gas. After heat exchange of nitrogen, the outlet nitrogen temperature is higher than the ambient temperature, which can save a small amount of fuel consumption in the hot blast stove. Attached Figure Description

[0018] Figure 1. Schematic diagram of nitrogen supplementation for coal milling and heat exchange process for low-temperature methanol washing generated gas in raw coal gasification unit.

[0019] Figure 2 is a schematic diagram of the structure of the coal mill nitrogen pressure difference energy utilization device of this utility model;

[0020] The components include: 1. Nitrogen source; 2. Coal mill; 3. Coal gasification crude syngas; 4. Steam boiling boiler; 5. Demineralized water heat exchanger; 6. Circulating water cooler; 7. Reduced pressure refrigeration generator; and 8. Nitrogen reheating heat exchanger. Detailed Implementation

[0021] The technical solution of this utility model will be further described in detail below through specific embodiments. However, it should be noted that the following embodiments are only used to describe the content of the invention and do not constitute a limitation on the protection scope of this utility model.

[0022] like Figure 1 As shown, in the raw coal gasification unit, the raw material coal-water slurry is prepared by the coal grinding system. The nitrogen source to maintain the stable pressure of the coal grinding system is low-pressure ambient temperature nitrogen with a pressure of 0.5 MPa. The outlet pressure of the coal grinding circulating fan is 2 kPa. The nitrogen needs to be depressurized. The method adopted is to use the nitrogen as a supplement to the coal grinding exhaust gas after passing through the pressure reducing valve.

[0023] Pulverized coal and oxygen react in a gasifier to produce high-temperature, high-pressure crude syngas, which is then cooled and purified before entering subsequent processing. The syngas cooling and purification process includes heat recovery (generating steam to recover heat and reduce the process gas temperature) and low-temperature methanol washing. Before entering the low-temperature methanol washing system, the gas needs to be cooled by heat exchange through a steam boiling boiler 4, a demineralized water heat exchanger 5, and a circulating water cooler 6 to reach room temperature before entering the low-temperature methanol washing system.

[0024] like Figure 2 As shown, this utility model's coal mill nitrogen pressure difference energy utilization device integrates a coal gasification unit to achieve comprehensive energy utilization. The device introduces low-pressure nitrogen from nitrogen source 1 into a reduced-pressure refrigeration generator 7. The nitrogen drives a turbine to generate electricity while simultaneously expanding and cooling, obtaining a low-temperature cold source to cool the process gas. The device includes a nitrogen source 1, a coal mill 2, a reduced-pressure refrigeration generator 7, and a nitrogen reheating heat exchanger 8. The low-pressure nitrogen from nitrogen source 1 enters the reduced-pressure refrigeration generator 7, and after depressurization, the nitrogen, as a low-temperature fluid, enters the nitrogen reheating heat exchanger 8. After heat exchange, it enters the coal mill 2. The high-temperature fluid in the nitrogen reheating heat exchanger 8 is the crude syngas produced by the coal gasification reaction.

[0025] The high-temperature, high-pressure crude syngas generated in the gasifier passes through a steam boiling pot 4 and a demineralized water heat exchanger 5 before entering the low-temperature methanol wash system. It then enters a nitrogen reheating heat exchanger 8 to exchange heat with depressurized nitrogen. After passing through a circulating water cooler 6, it reaches ambient temperature before entering the low-temperature methanol wash system. The nitrogen reheating heat exchanger 8 is a shell-and-tube heat exchanger, with the low-temperature nitrogen flowing through the tubes and the crude syngas through the shell. Due to the significant temperature difference between the two gases, the heat exchanger needs to have a certain deformation compensation function; a fixed tube sheet heat exchanger with an expansion joint is preferred.

[0026] Low-pressure nitrogen gas (0.4-0.8 MPa, ambient temperature) is introduced from nitrogen source 1 through a pipeline into vacuum refrigeration generator 7. The shaft power output by the turbine expansion drives the generator to generate electricity and expand to output cooling capacity. The low-temperature nitrogen gas (-20℃, 3-6 kPa) exiting vacuum refrigeration generator 7 enters nitrogen reheating heat exchanger 8. The nitrogen gas exchanges heat with the high-temperature fluid crude syngas and enters the coal pulverizing system 2 at a temperature higher than ambient temperature after absorbing heat. The crude syngas 3 from the gasifier recovers heat by passing through steam boiling pot 4 and demineralized water heat exchanger 5. The temperature of the crude syngas is 70-110℃. After passing through nitrogen reheating heat exchanger 8, the temperature drops to 65-105℃, which can save water consumption in circulating water cooler 6. The nitrogen gas, which is warmer than ambient temperature after reheating, enters the pulverized coal pulverizing device, which can reduce fuel consumption of the hot blast stove.

Claims

1. A device for utilizing nitrogen pressure difference energy in coal milling, comprising a coal milling device (2) and a nitrogen source (1), characterized in that, The device also includes a reduced pressure refrigeration generator (7) and a nitrogen reheating heat exchanger (8). Low-pressure nitrogen from the nitrogen source (1) enters the reduced pressure refrigeration generator (7). After depressurization, the nitrogen enters the nitrogen reheating heat exchanger (8) as a low-temperature fluid. After heat exchange, it enters the coal mill (2). The high-temperature fluid in the nitrogen reheating heat exchanger (8) is the synthesis gas produced by the coal gasification reaction. After being cooled by the nitrogen reheating heat exchanger (8), it enters the circulating water cooler (6) and enters the low-temperature methanol washing device after being cooled to room temperature.

2. The coal mill nitrogen pressure difference energy utilization device according to claim 1, characterized in that, In the aforementioned reduced pressure refrigeration generator (7), low-pressure nitrogen gas expands and depressurizes to do work and drives a turbine to generate electricity.

3. The coal mill nitrogen pressure difference energy utilization device according to claim 1, characterized in that, The nitrogen reheat heat exchanger (8) is a partitioned heat exchanger.

4. The coal mill nitrogen pressure difference energy utilization device according to claim 3, characterized in that, The nitrogen reheat heat exchanger (8) is a fixed tube sheet heat exchanger with an expansion joint.

5. The coal mill nitrogen pressure difference energy utilization device according to claim 1, characterized in that, The synthesis gas is passed through a steam boiling pot (4) and a demineralized water heat exchanger (5) in sequence, and then enters a nitrogen reheating heat exchanger (8); after passing through a circulating water cooler (6) for heat exchange, it enters a low-temperature methanol washing device.

6. The coal mill nitrogen pressure difference energy utilization device according to claim 1, characterized in that, The pressure of the low-pressure nitrogen gas is 0.4-0.8 MPa, and after being reduced by the pressure-reducing refrigeration generator (7), it is 3-6 kPa.

7. The coal mill nitrogen pressure difference energy utilization device according to claim 1, characterized in that, After heat exchange via the nitrogen reheat heat exchanger (8), the temperature of the nitrogen is controlled at 40-80°C.

Images