A flash gas waste heat recovery system

Abstract

This invention provides a flash gas waste heat recovery system, belonging to the field of chemical equipment technology. The system structure consists of a flash steam pipeline at the top of a low-pressure flash tank connected to a deaerator; a black water pipeline at the bottom of the low-pressure flash tank connected to a vacuum flash tank; a branch line connecting the flash steam pipeline to a low-pressure flash steam bypass pipeline, the downstream of which connects to the shell side of a low-pressure nitrogen heat exchanger, with a condensate pipe connected to the bottom of the shell side of the low-pressure nitrogen heat exchanger; a low-pressure nitrogen pipeline network connecting the downstream of the air separation low-pressure nitrogen main pipeline; a branch line connecting the air separation low-pressure nitrogen main pipeline upstream of the low-pressure nitrogen pipeline network to a low-pressure nitrogen-to-coal mill pipeline; a low-pressure nitrogen heat exchange pipeline connected in parallel to the low-pressure nitrogen-to-coal mill pipeline; and a low-pressure nitrogen heat exchanger connected in series on the low-pressure nitrogen heat exchange pipeline. This invention utilizes low-pressure flash steam to heat a newly added low-pressure nitrogen heat exchanger, while simultaneously reducing the amount of low-pressure steam used, achieving waste heat recovery and utilization, and reducing production costs.

Description

Technical Field

[0001] This utility model relates to the field of chemical equipment technology, specifically a flash gas waste heat recovery system. Background Technology

[0002] Generally, flash waste heat recovery not only significantly reduces energy consumption and production costs, but also reduces emissions of harmful gases such as carbon dioxide, contributing to environmental protection. Its high efficiency and reliability make flash waste heat recovery technology a preferred solution for industrial energy conservation and emission reduction.

[0003] In coal pulverizing systems, the low-pressure steam, low-flash steam, and low-pressure nitrogen contain a large amount of waste heat. How to effectively utilize these waste heat, achieve energy conservation and emission reduction, and recover and reuse this waste heat is an important issue that needs to be addressed and solved in modern processes. Summary of the Invention

[0004] The technical objective of this invention is to address the shortcomings of existing technologies and provide a flash gas waste heat recovery system.

[0005] The technical solution of this utility model is implemented in the following way: a flash gas waste heat recovery system of this utility model, the system structure includes a low-pressure flash tank and an air separation low-pressure nitrogen main pipe;

[0006] The flash vapor line at the top of the low-pressure flash tank is connected to the deaerator;

[0007] The black water pipe at the bottom of the low-pressure flash tank is connected to the vacuum flash tank;

[0008] The flash vapor pipeline is branched and connected to the low flash vapor bypass pipeline. The downstream of the low flash vapor bypass pipeline is connected to the shell side of the low-pressure nitrogen heat exchanger. The bottom of the shell side of the low-pressure nitrogen heat exchanger is connected to the condensate pipe.

[0009] Downstream of the air separation low-pressure nitrogen main pipe is connected to the low-pressure nitrogen pipeline network; upstream of the low-pressure nitrogen pipeline network, the air separation low-pressure nitrogen main pipe is branched and connected to the low-pressure nitrogen to the coal mill pipeline.

[0010] The low-pressure nitrogen heat exchange pipeline is connected in parallel to the low-pressure nitrogen pipeline to the coal mill.

[0011] The low-pressure nitrogen heat exchanger is connected in series with the low-pressure nitrogen heat exchange pipeline, and the low-pressure nitrogen heat exchange pipeline runs through the tube side of the low-pressure nitrogen heat exchanger.

[0012] The end of the low-pressure nitrogen pipeline to the coal mill is connected to the coal milling system.

[0013] Pressure transmitter control electromagnetic regulating valves are installed between the low-pressure flash tank, flash steam pipeline, and deaerator pipeline.

[0014] A shut-off valve is installed on the upstream section of the low-flash steam bypass pipeline. The shut-off valve is switched on and off by a pressure transmitter of the low-flash steam bypass pipeline adjacent to its upstream side.

[0015] The midstream section of the low-flash steam bypass pipeline is equipped with a temperature-controlled electromagnetic regulating valve, which is controlled and regulated by the nitrogen temperature transmitter at the tube-side outlet of the low-pressure nitrogen heat exchanger.

[0016] An upstream nitrogen pressure transmitter and regulating solenoid valve is installed on the upstream section of the low-pressure nitrogen heat exchanger tube side.

[0017] A downstream nitrogen pressure transmitter and regulator solenoid valve is installed on the downstream section of the low-pressure nitrogen heat exchanger tube side.

[0018] The upstream nitrogen pressure transmitter and regulator solenoid valve and the downstream nitrogen pressure transmitter and regulator solenoid valve are interlocked.

[0019] A manual valve or regulating valve is installed in the middle section of the low-pressure nitrogen to coal mill pipeline connected in parallel with the low-pressure nitrogen heat exchange pipeline.

[0020] The working principle of this utility model is as follows:

[0021] 1. The black water from the bottom of the high-pressure flash tank is sent to the low-pressure flash tank for flash evaporation. The flash steam from the top of the low-pressure flash tank is sent to the deaerator for deoxygenation of grey water and system replenishment demineralized water. The black water after low-pressure flash evaporation then enters the vacuum flash tank for further flash evaporation. Some low-pressure flash steam remains after deaeration; this is sent to the newly added low-pressure nitrogen heat exchanger to reduce the amount of low-pressure steam used and achieve waste heat reuse.

[0022] 2. The normal temperature of the low-pressure nitrogen main pipe from the air separation unit is 22 degrees Celsius. It enters the gasification pulverizer system as a protective gas and sealing gas for the mill, with a consumption of about 10,000 standard cubic meters per hour. To ensure that the pulverized coal temperature is qualified, the mill outlet temperature is controlled at about 105 degrees Celsius. The hot blast stove controls the hot blast stove outlet temperature to 330 degrees Celsius by mixing fuel gas with the combustion fan to continuously provide heat to the mill and control the pulverized coal temperature to meet the standard. By adding a low-pressure nitrogen heat exchanger, the temperature of the low-pressure nitrogen entering the pulverizer system is increased, heat loss is reduced, the fuel gas consumption of the hot blast stove is reduced, the crude alcohol production is increased, and the quality and efficiency are improved.

[0023] Effects after technical upgrade: By increasing the heat exchange between low-flash steam and nitrogen, the low-pressure steam can be reduced by about 1-2 tons per hour, the nitrogen temperature can be increased from 22 degrees to 85 degrees, the fuel gas consumption of the coal mill system can be reduced by 300-500 standard cubic meters per hour, and the crude alcohol production can be increased by about 0.13 tons per hour, with significant benefits.

[0024] The beneficial effects of this utility model compared with the prior art are:

[0025] This utility model provides a flash gas waste heat recovery system, which addresses the shortcomings of existing technologies by offering a rationally designed and highly efficient flash gas recovery technology.

[0026] The black water from the gasifier undergoes three stages of flash evaporation: high flash, low flash, and true flash. This process lowers the water temperature and releases gases from the black water. The low flash pressure is normally controlled at 0.25 MPa and the temperature at 135 degrees Celsius. The low-pressure flash vapor from the flash evaporation enters the deaerator tank to provide a heat source for deoxygenating the ash water. The pressure of the low-pressure flash tank is regulated by a pressure regulating valve on the low-pressure flash vapor outlet pipeline. The liquid level in the low-pressure flash tank is regulated by a level regulating valve on the bottom black water outlet pipeline to the true flash tank. Currently, some of the deoxygenated flash vapor can be recycled.

[0027] This invention utilizes low-flash steam to heat a newly added low-pressure nitrogen heat exchanger, while simultaneously reducing the amount of low-pressure steam used, achieving waste heat recovery and utilization, and lowering production costs.

[0028] The core utility model features low-flash steam waste heat recovery. By using a low-pressure nitrogen heat exchanger to increase the temperature of low-pressure nitrogen, the amount of low-pressure steam used is reduced, the temperature of low-pressure nitrogen entering the coal pulverizing system is increased, the amount of fuel gas used in the coal pulverizing system is reduced, and the yield of crude alcohol is increased. While ensuring the effectiveness of nitrogen heat exchange, online switching between low-pressure steam and low-flash steam can be achieved.

[0029] The flash gas waste heat recovery system of this utility model is reasonably designed, simple in structure, safe and reliable, easy to use and maintain, and has great value for promotion and application. Attached Figure Description

[0030] Appendix Figure 1 This is a schematic diagram of the structure of this utility model.

[0031] The markings in the attached diagram represent:

[0032] 1. Low-pressure flash tank,

[0033] 2. Flash vapor piping; 3. Deaerator;

[0034] 4. Black water pipeline; 5. Vacuum flash tank;

[0035] 6. Low-flash steam bypass piping,

[0036] 7. Low-pressure nitrogen heat exchanger; 8. Shell side; 9. Tube side.

[0037] 10. Condensate pipe

[0038] 11. Low-pressure nitrogen main pipe for air separation; 12. Low-pressure nitrogen pipeline network;

[0039] 13. Low-pressure nitrogen gas supply pipeline to the coal mill.

[0040] 14. Low-pressure nitrogen heat exchange piping,

[0041] 15. Heat exchanger tube sheet,

[0042] 16. Coal grinding system

[0043] 17. Pressure transmitter control solenoid regulating valve,

[0044] 18. Shut-off valve

[0045] 19. Temperature-controlled solenoid valve,

[0046] 20. Upstream section nitrogen pressure transmitter and regulating solenoid valve,

[0047] 21. Downstream nitrogen pressure transmitter and regulating solenoid valve,

[0048] 22. Manual valve or regulating valve. Detailed Implementation

[0049] The following is a detailed description of a flash gas waste heat recovery system according to the present invention, with reference to the accompanying drawings.

[0050] As shown in the attached figure, this utility model discloses a flash gas waste heat recovery system, the system structure of which includes a low-pressure flash tank and an air separation low-pressure nitrogen main pipe.

[0051] The flash vapor line at the top of the low-pressure flash tank is connected to the deaerator;

[0052] The black water pipe at the bottom of the low-pressure flash tank is connected to the vacuum flash tank;

[0053] The flash vapor pipeline is branched and connected to the low flash vapor bypass pipeline. The downstream of the low flash vapor bypass pipeline is connected to the shell side of the low-pressure nitrogen heat exchanger. The bottom of the shell side of the low-pressure nitrogen heat exchanger is connected to the condensate pipe.

[0054] Downstream of the air separation low-pressure nitrogen main pipe is connected to the low-pressure nitrogen pipeline network; upstream of the low-pressure nitrogen pipeline network, the air separation low-pressure nitrogen main pipe is branched and connected to the low-pressure nitrogen to the coal mill pipeline.

[0055] The low-pressure nitrogen heat exchange pipeline is connected in parallel to the low-pressure nitrogen pipeline to the coal mill.

[0056] The low-pressure nitrogen heat exchanger is connected in series with the low-pressure nitrogen heat exchange pipeline, and the low-pressure nitrogen heat exchange pipeline runs through the tube side of the low-pressure nitrogen heat exchanger.

[0057] The end of the low-pressure nitrogen pipeline to the coal mill is connected to the coal milling system.

[0058] Pressure transmitter control electromagnetic regulating valves are installed between the low-pressure flash tank, flash steam pipeline, and deaerator pipeline.

[0059] A shut-off valve is installed on the upstream section of the low-flash steam bypass pipeline. The shut-off valve is switched on and off by a pressure transmitter of the low-flash steam bypass pipeline adjacent to its upstream side.

[0060] The midstream section of the low-flash steam bypass pipeline is equipped with a temperature-controlled electromagnetic regulating valve, which is controlled and regulated by the nitrogen temperature transmitter at the tube-side outlet of the low-pressure nitrogen heat exchanger.

[0061] An upstream nitrogen pressure transmitter and regulating solenoid valve is installed on the upstream section of the low-pressure nitrogen heat exchanger tube side.

[0062] A downstream nitrogen pressure transmitter and regulator solenoid valve is installed on the downstream section of the low-pressure nitrogen heat exchanger tube side.

[0063] The upstream nitrogen pressure transmitter and regulator solenoid valve and the downstream nitrogen pressure transmitter and regulator solenoid valve are interlocked.

[0064] A manual valve or regulating valve is installed in the middle section of the low-pressure nitrogen to coal mill pipeline connected in parallel with the low-pressure nitrogen heat exchange pipeline.

[0065] This invention discloses a flash steam waste heat recovery system that operates safely and stably. It allows for online adjustment of low-flash steam and low-pressure steam, ensuring the temperature of low-pressure nitrogen after heat exchange.

[0066] The nitrogen gas originates from a DN500 low-pressure nitrogen main pipe in the air separation unit, with a pressure of 0.4 MPa and a temperature of 22 degrees Celsius. A DN350 pipe is used as a shunt outlet to the gasification unit, and a DN250 pipe is used to connect to the coal milling unit. A DN200 valve is added to the shunt outlet before the manual valve of the DN250 main pipe leading to the coal mill, and then to the low-pressure nitrogen heat exchanger. A DN200 valve is added to the heat exchange gas outlet main pipe, and after the manual valve of the DN250 main pipe leading to the coal mill, the shell side of the low-pressure nitrogen heat exchanger is filled with nitrogen, and the tube side is filled with low-pressure steam and low-flash steam. The low-pressure steam comes from the pipeline network, and the low-flash steam is connected to the regulating valve at the top of the low-flash tank, and a shunt outlet before the oxygenator valve leads to the nitrogen heat exchanger. A manual valve, pressure gauge, and shut-off valve are installed on this pipeline. Temperature, pressure, and flow meters are installed at the inlet and outlet of the low-pressure nitrogen gas. Check valves, pressure, temperature, and flow meters are installed at the inlets of the low-pressure steam and low-flash steam respectively. The low-pressure steam and low-flash steam enter the heat exchanger separately to prevent pressure buildup. Both pipelines are equipped with manual and regulating valves, and the outlet temperature of the low-pressure nitrogen gas after heat exchange is automatically controlled. When the outlet temperature is too high, the regulating valves for the low-pressure steam and low-flash steam are interlocked and closed. When the pressure before the low-flash steam shut-off valve rises to 0.3 MPa, the low-flash steam shut-off valve is interlocked and closed to prevent low-pressure steam from backflowing into the low-pressure flash tank. The outlet temperature of the heat exchange gas automatically switches to manual control. Simultaneously, the heat exchange gas body is equipped with a pressure gauge and safety valve. When the pressure rises to 0.45 MPa, the nitrogen inlet regulating valve is interlocked and closed to ensure equipment safety and controllability. When the low-flash steam flow rate can meet the nitrogen temperature requirements, the low-pressure steam flow rate can be reduced until it is completely withdrawn. The condensate after heat exchange is sent to the condensate pipeline network, maximizing energy savings.

[0067] Before heat exchange, the low-pressure nitrogen temperature was 22 degrees Celsius, and after heat exchange, the temperature could be increased to 85 degrees Celsius, with a significant heat exchange effect. After the nitrogen temperature was increased, the fuel gas consumption of the hot blast stove in the coal pulverizing system was significantly reduced, which indirectly increased the crude alcohol production and further released the production capacity.

[0068] By implementing this utility model, the following can be achieved:

[0069] 1. Low-flash steam waste heat recovery and utilization can save 1 to 2 tons of steam per hour.

[0070] 2. Low-pressure steam and low-flash steam can be used simultaneously according to the nitrogen heat exchanger outlet temperature and the requirements of the coal pulverizing system to maximize the nitrogen temperature and ensure the economical operation of the coal pulverizing system.

[0071] 3. After the temperature increases, the amount of fuel gas used in the hot air furnace is significantly reduced, achieving energy saving and consumption reduction.

[0072] 4. Automatic control, safety interlock, simple structure, easy to operate and convenient to maintain.

[0073] The key features of this invention are safety, energy saving, and environmental protection. Based on the outlet temperature of the low-pressure nitrogen heat exchanger, the low-flash steam and low-pressure steam can be freely adjusted. By increasing the nitrogen temperature, the amount of fuel gas used in the hot air furnace is reduced while ensuring that the mill outlet temperature remains unchanged, thus saving energy and improving quality and efficiency.

[0074] The key technical aspects of this utility model are:

[0075] The newly added nitrogen heat exchanger enables automatic temperature control of the outlet temperature of low-pressure steam and low-flash steam, facilitating adjustment.

[0076] 2. The low-flash steam and low-pressure steam can be freely adjusted according to the heat exchanger outlet temperature and the requirements of the coal pulverizing system. They can be used simultaneously or separately, and the operation is convenient.

[0077] 3. When the temperature and pressure of the heat exchanger exceed the standard, automatic interlocking can be realized to ensure the safety and controllability of the equipment and pipelines.

[0078] 4. This utility model has low investment cost, significant energy-saving effect and high safety factor.

[0079] As shown in the attached diagram:

[0080] PT: Pressure transmitter, used to convert pressure signals into standard signal outputs.

[0081] LT: Level transmitter, used to convert level signals into standard signal outputs.

[0082] FT: Flow transmitter, used to convert flow signals into standard signal outputs.

[0083] T: Temperature indicator, used to display temperature.

[0084] PIC: Pressure controller, used to control pressure.

Claims

1. A flash gas waste heat recovery system characterized by The system structure includes a low-pressure flash tank and a low-pressure nitrogen main for air separation; The flash vapor line at the top of the low-pressure flash tank is connected to the deaerator; The black water pipe at the bottom of the low-pressure flash tank is connected to the vacuum flash tank; The flash vapor pipeline is branched and connected to the low flash vapor bypass pipeline. The downstream of the low flash vapor bypass pipeline is connected to the shell side of the low-pressure nitrogen heat exchanger. The bottom of the shell side of the low-pressure nitrogen heat exchanger is connected to the condensate pipe. Downstream of the air separation low-pressure nitrogen main pipe is connected to the low-pressure nitrogen pipeline network; upstream of the low-pressure nitrogen pipeline network, the air separation low-pressure nitrogen main pipe is branched and connected to the low-pressure nitrogen to the coal mill pipeline. The low-pressure nitrogen heat exchange pipeline is connected in parallel to the low-pressure nitrogen pipeline to the coal mill. The low-pressure nitrogen heat exchanger is connected in series with the low-pressure nitrogen heat exchange pipeline, and the low-pressure nitrogen heat exchange pipeline runs through the tube side of the low-pressure nitrogen heat exchanger. The end of the low-pressure nitrogen pipeline to the coal mill is connected to the coal milling system.

2. The flash gas waste heat recovery system according to claim 1, characterized in that: Pressure transmitter control electromagnetic regulating valves are installed between the low-pressure flash tank, flash steam pipeline, and deaerator pipeline.

3. The flash gas waste heat recovery system according to claim 1, characterized in that: A shut-off valve is installed on the upstream section of the low-flash steam bypass pipeline. The shut-off valve is switched on and off by a pressure transmitter of the low-flash steam bypass pipeline adjacent to its upstream side.

4. A flash gas waste heat recovery system according to claim 1, characterized in that: The midstream section of the low-flash steam bypass pipeline is equipped with a temperature-controlled electromagnetic regulating valve, which is controlled and regulated by the nitrogen temperature transmitter at the tube-side outlet of the low-pressure nitrogen heat exchanger.

5. A flash gas waste heat recovery system according to claim 1, characterized in that: An upstream nitrogen pressure transmitter and regulating solenoid valve is installed on the upstream section of the low-pressure nitrogen heat exchanger tube side. A downstream nitrogen pressure transmitter and regulator solenoid valve is installed on the downstream section of the low-pressure nitrogen heat exchanger tube side. The upstream nitrogen pressure transmitter and regulator solenoid valve and the downstream nitrogen pressure transmitter and regulator solenoid valve are interlocked.

6. A flash gas waste heat recovery system according to claim 1, characterized in that: A manual valve or regulating valve is installed in the middle section of the low-pressure nitrogen to coal mill pipeline connected in parallel with the low-pressure nitrogen heat exchange pipeline.

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