Power generation system applied to waste heat recovery of ethylene glycol DMO synthesis device

Abstract

The utility model discloses a power generation system applied to waste heat recovery of an ethylene glycol DMO synthesis device, which comprises a quick-closing valve, a regulating valve, a screw expander, a power generator, a condenser, a vacuum pump, a condensate pump, a circulating water pump, a cooling tower and a recuperator, condensed water discharged by the system can be used as replenishing water of the synthetic steam pocket; the system well solves the problems that the temperature of exhaust steam condensate water of a traditional condensation power generation system is too low, and a synthetic reaction steam pocket cannot be directly recycled for self-use; the difficulty that the steam cannot be well recycled due to low steam pressure and high steam water content in the traditional power generation technology is solved; the comprehensive utilization rate of enterprise energy is improved, and the production cost and production self-consumption of ethylene glycol are reduced.

Description

Technical Field

[0001] The utility model relates to the technical field related to waste heat utilization of a coal-to-ethylene glycol (DMO) synthesis device, and in particular to a power generation system applied to waste heat recovery of an ethylene glycol (DMO) synthesis device. Background Art

[0002] Ethylene glycol is an important basic raw material and chemical intermediate. It is often used in the synthesis of polyester fibers and antifreeze. It has a wide range of downstream uses and can also be used as a solvent, lubricant, plasticizer, surfactant, etc. With the rapid development of my country's polyester industry, it has formed a large industrial field. At present, there are two main technologies for the industrial production of ethylene glycol: one is the ethylene oxide hydration method represented by the traditional petroleum route; the other is to convert coal as a raw material to produce synthesis gas and then synthesize ethylene glycol. In the face of the many shortcomings of the petroleum route and the domestic energy structure of rich coal and poor oil, coal-to-ethylene glycol has received more and more attention.

[0003] The DMO synthesis process of coal-to-ethylene glycol requires the transfer of synthesis reaction heat to generate low-pressure saturated steam. Only a part of this steam is used as heating steam for preheating circulating gas, and the rest of the steam is mostly cooled into steam condensate using circulating water or air coolers. The heat is not fully recovered and utilized, and water and electricity are consumed during the cooling process, which is a large waste of energy.

[0004] In order to maintain a suitable reaction temperature during the production process, the synthesis reactor has high requirements for the internal synthesis reaction temperature control. The synthesis drum temperature control range is between 106 and 130°C. The synthesis catalyst is generally designed to have a service life of 3 years. The drum temperature will gradually increase according to the catalyst activity decay. The drum temperature is controlled at 106-110°C in the first 2 years, and the drum temperature is raised to 130°C in the final year of operation. In order to accurately control the synthesis reaction temperature and ensure the internal temperature control balance, the synthesis drum water supply temperature is designed to be 80°C. A higher water supply temperature can effectively prevent the drum temperature fluctuation caused by the cold water supply, which indirectly affects the internal reaction temperature of the synthesis reactor.

[0005] On the one hand, the pressure of the low-pressure saturated steam produced as a by-product of the synthesis drum is about 0.025-0.17MPa.g, and the temperature is 106-130℃. The steam pressure is too low and the water content is high. Traditional steam turbines are prohibited from running with water. Steam with water can easily cause water hammer and erosion on the blades. The steam pressure is too low and the water content is high under this operating condition, resulting in the inability of traditional power generation technology to recycle it well. On the other hand, the steam exhaust pressure of the traditional condensing power generation system is at -0.09MPa.g and the temperature is 45℃. Under ideal isothermal condensation conditions, the maximum temperature of the condensed water is only 45℃, which cannot meet the synthesis drum feed water temperature requirements. At present, many companies directly condense and recycle this part of the low-pressure steam through circulating water or air cooling during the production process, resulting in energy waste. Utility Model Content

[0006] The utility model aims to provide a power generation system for waste heat recovery of an ethylene glycol DMO synthesis device, which has strong adaptability to working conditions, can operate within a load fluctuation range of 30%-120%, is not afraid of water hammer and water erosion, can directly utilize steam-water two-phase flow, and has efficient utilization of low-pressure saturated steam; and can solve the problem that the condensate temperature of a traditional condensing power generation system is too low and the synthesis reaction drum cannot be directly recovered for self-use.

[0007] The above technical objectives of the utility model are achieved through the following technical solutions:

[0008] A power generation system for waste heat recovery of an ethylene glycol (DMO) synthesis device comprises a screw expander, a generator, a vacuum pump, a condenser, a cooling device, a condensate pump and a recuperator, wherein a steam inlet of the screw expander is connected to a steam side of a synthesis drum through a steam inlet pipeline, the screw expander is transmission-connected to the generator through a coupling, a steam exhaust port of the screw expander is connected to a steam inlet of a condenser through a pipeline, the vacuum pump is connected to a non-condensable gas outlet of the condenser through a pipeline, a circulating cooling port of the condenser is connected to the cooling device, a water outlet of the condenser is connected to a water inlet of a condensate pump through a pipeline, a water outlet of the condenser is connected to a water inlet of a condensate pump through a pipeline, a water outlet of the condensate pump is connected to a water inlet of a recuperator through a pipeline, a water outlet of the recuperator is connected to a water side of a synthesis drum through a pipeline, and a steam inlet of the recuperator is connected to a steam side of a synthesis drum through a recuperation pipeline.

[0009] Furthermore, the cooling device includes a circulating water pump and a cooling tower; the circulating water outlet of the condenser is connected to the return water outlet of the cooling tower through a pipe, the water inlet of the circulating water pump is connected to the water outlet of the cooling tower through a pipe, and the water outlet of the circulating water pump is connected to the circulating water inlet of the condenser through a pipe.

[0010] Furthermore, the condensate outlet of the reheater is connected to the water inlet of the condenser through a pipeline.

[0011] Furthermore, a quick-closing valve and a regulating valve are provided on the steam inlet pipeline, and the regulating valve is installed at the rear end of the quick-closing valve.

[0012] Furthermore, a reheating regulating valve is installed on the reheating pipeline.

[0013] In summary, the utility model has the following beneficial effects:

[0014] 1. Compared with the problem of low condensate temperature in traditional condensing power generation systems, this system can fully recover the heat of low-pressure steam for power generation while ensuring that the condensate temperature discharged from the system reaches 80°C. The synthesis reaction drum can be directly recovered for self-use without affecting the drum temperature and the reaction temperature inside the synthesis reactor;

[0015] 2. The large amount of low-pressure saturated steam generated by the ethylene glycol DMO synthesis unit can be effectively recovered. This is because the screw expander in this system works in a completely different way from the traditional steam turbine. It can effectively recover the waste heat steam with very low pressure. It has a wide range of adaptability to the pressure of the recovered steam and can operate within the load fluctuation range of 30%-120%. It is not afraid of water hammer and water erosion and can directly utilize the steam-water two-phase flow.

[0016] 3. According to statistical data, a set of ethylene glycol production equipment with an annual output of 600,000 tons / year has an installed power of 6000KW and a rated power of 5100KW. The annual power generation can reach 37.92 million degrees, which has considerable economic and social effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the overall structural diagram of the utility model.

[0018] Figure numerals: 1. quick-closing valve; 2. regulating valve; 3. screw expander; 4. generator; 5. vacuum pump; 6. condenser; 7. circulating water pump; 8. cooling tower; 9. condensate pump; 10. reheater; 11. reheating regulating valve; 12. steam inlet pipe; 13. reheating pipe. DETAILED DESCRIPTION

[0019] The utility model is further described in detail below in conjunction with the accompanying drawings, and the technical solutions in the embodiments of the utility model are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0020] like Figure 1As shown, a power generation system for waste heat recovery of an ethylene glycol (DMO) synthesis device includes a screw expander 3, a generator 4, a vacuum pump 5, a condenser 6, a cooling device, a condensate pump 9 and a recuperator 10. The steam inlet of the screw expander 3 is connected to the steam side of a synthesis drum through a steam inlet pipe 12. The synthesis drum is a cylindrical structure, with the upper half being the steam side and the lower half being the water side. The main function of the synthesis drum is to accurately control the temperature of the ethylene glycol (DMO) synthesis reaction, distribute the make-up water to each heating surface, separate the steam-water mixture, and finally remove the heat generated during the reaction in the form of steam. The screw expander 3 is connected to the generator 4 through a coupling, driving the generator 4 to generate electricity; the exhaust port of the screw expander 3 is connected to the steam inlet of the condenser 6 through a pipeline, and the vacuum pump 5 is connected to the non-condensable gas outlet of the condenser 6 through a pipeline to extract the non-condensable gas in the condenser 6 to maintain a high vacuum degree inside it; the circulating cooling port of the condenser 6 is connected to the cooling device, the water outlet of the condenser 6 is connected to the water inlet of the condensate pump 9 through a pipeline, the water outlet of the condensate pump 9 is connected to the water inlet of the recuperator 10 through a pipeline, the water outlet of the recuperator 10 is connected to the synthesis steam drum feed water tank through a pipeline, the condensate is pressurized by the condensate pump 9, heated to 80°C in the recuperator, and sent back to the synthesis steam drum for recycling. The steam inlet of the recuperator 10 is connected to the synthesis steam drum feed water tank through the recuperation pipe 13. A small amount of steam is introduced from the recuperation pipe 13 as a heating source for the recuperator 10. The synthesis steam drum feed water tank is installed in the ethylene glycol DMO synthesis device to supply water to the synthesis steam drum to ensure uninterrupted steam-water circulation in the ethylene glycol DMO synthesis device.

[0021] The cooling device includes a circulating water pump 7 and a cooling tower 8; the circulating water outlet of the condenser 6 is connected to the return water outlet of the cooling tower 8 through a pipeline, the water inlet of the circulating water pump 7 is connected to the water outlet of the cooling tower 8 through a pipeline, and the water outlet of the circulating water pump 7 is connected to the circulating water inlet of the condenser 6 through a pipeline.

[0022] Furthermore, the condensate outlet of the recuperator 10 is connected to the water inlet of the condenser 6 through a pipeline. The condensate in the recuperator 10 absorbs the heat of steam to increase its temperature. After the heat of the steam is taken away, condensate is formed and transported to the condenser 6 through the pipeline for recycling.

[0023] Preferably, a quick-closing valve 1 and a regulating valve 2 are provided on the steam inlet pipe 12, and the regulating valve 2 is installed at the rear end of the quick-closing valve 1, the quick-closing valve 1 is used to quickly close the passage, and the regulating valve 2 is used to adjust the size of the passage.

[0024] Preferably, a reheating regulating valve 11 is installed on the reheating pipeline 13, and the steam flow of the reheating pipeline 13 is controlled by adjusting the opening degree of the reheating regulating valve 11.

[0025] Working principle:

[0026] The low-pressure steam on the steam side of the synthesis drum enters the screw expander 3 through the steam inlet pipe 12, the quick-closing valve 1 and the regulating valve 2 to expand and do work. The screw expander 3 drives the generator 4 to rotate through the coupling. The expansion work of the screw expander 3 drives the generator 4 to generate electricity, and the output electric energy is incorporated into the enterprise intranet.

[0027] The exhaust steam (pressure -0.09MPa.g, temperature 45°C) discharged from the exhaust port of the screw expander 3 enters the condenser 6 and exchanges heat with the circulating cooling water to form 45°C condensate. The condensate is pressurized and transported to the reheater 10 through the condensate pump 9. After the condensate is reheated to 80°C, it is used as water for the synthesis steam drum. The steam is introduced from the reheating pipe 13 through the reheating regulating valve 11, and the condensed water enters the condenser 6 back to the system through the pipe.

[0028] The non-condensable gas in the condenser 6 is extracted by the vacuum pump 5 to maintain a high vacuum degree of the condenser 6; the high-temperature water in the condenser 6 after heat exchange flows into the cooling tower 8 for cooling, and the cooled water in the cooling tower 8 is circulated to the condenser 6 through the circulating water pump 7.

[0029] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as the modifications are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A power generation system for waste heat recovery of an ethylene glycol (DMO) synthesis unit, characterized in that: The invention comprises a screw expander (3), a generator (4), a vacuum pump (5), a condenser (6), a cooling device, a condensate pump (9) and a recuperator (10), wherein the steam inlet of the screw expander (3) is connected to the steam side of the synthesis steam drum through a steam inlet pipeline (12), the screw expander (3) is transmission-connected to the generator (4) through a coupling, the steam exhaust port of the screw expander (3) is connected to the steam inlet of the condenser (6) through a pipeline, and the vacuum pump (5) is connected to the steam outlet of the condenser (6) through a pipeline. The non-condensable gas outlet of the condenser (6) is connected, the circulating cooling port of the condenser (6) is connected to the cooling device, the water outlet of the condenser (6) is connected to the water inlet of the condensate pump (9) through a pipeline, the water outlet of the condensate pump (9) is connected to the water inlet of the recuperator (10) through a pipeline, the water outlet of the recuperator (10) is connected to the synthesis steam drum feed water tank through a pipeline, and the steam inlet of the recuperator (10) is connected to the steam side of the synthesis steam drum through a recuperation pipeline (13).

2. A power generation system for waste heat recovery of an ethylene glycol DMO synthesis device according to claim 1, characterized in that: The cooling device comprises a circulating water pump (7) and a cooling tower (8); the circulating water outlet of the condenser (6) is connected to the water return port of the cooling tower (8) through a pipeline, the water inlet of the circulating water pump (7) is connected to the water outlet of the cooling tower (8) through a pipeline, and the water outlet of the circulating water pump (7) is connected to the circulating water inlet of the condenser (6) through a pipeline.

3. A power generation system for waste heat recovery of an ethylene glycol DMO synthesis device according to claim 2, characterized in that: The condensed water outlet of the reheater (10) is connected to the water inlet of the condenser (6) through a pipeline.

4. The power generation system for waste heat recovery of an ethylene glycol DMO synthesis device according to claim 1, characterized in that: The steam inlet pipeline (12) is provided with a quick-closing valve (1) and a regulating valve (2), and the regulating valve (2) is installed at the rear end of the quick-closing valve (1).

5. The power generation system for waste heat recovery of ethylene glycol DMO synthesis device according to claim 1, characterized in that: The reheating pipe (13) is provided with a reheating regulating valve (11).

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