An ethylene glycol energy-saving device coupled with a cooling and power cogeneration system and a method of using the same

Abstract

The present invention discloses an ethylene glycol energy-saving device coupled with a combined cooling and power generation system and a method for using the device, comprising an ethylene glycol separation device and a combined cooling and power generation system, wherein the combined cooling and power generation system comprises a power generation system and a refrigeration system, wherein the power generation system comprises a first condenser, a first working fluid pump, a first evaporator, a turbine and an intermediate heat exchanger, wherein the first condenser, the first working fluid pump and the intermediate heat exchanger are connected in a closed loop, and the refrigeration system comprises a first regenerator, a second working fluid pump, a flash tank, a second condenser, a first expansion valve, a second evaporator, an absorber, a second expansion valve and a second regenerator; in the present invention, the power generation system and the absorption refrigeration system are combined in a heat integration manner to form an independent combined cooling and power generation system, which can realize the functions of power generation and refrigeration at the same time, realize the purity of the ethylene glycol product, realize the efficient conversion of the waste heat in the device, avoid the heat loss caused by the heat exchange, and improve the energy conversion efficiency of the waste heat recovery system.

Description

Technical Field

[0001] The present invention relates to the technical field of energy conservation and emission reduction in chemical processes, and in particular to an ethylene glycol energy-saving device coupled with a cooling and power cogeneration system and a method for using the same. Background Art

[0002] With growing environmental awareness, energy conservation in industrial processes has become increasingly important. Industrial operations generate significant amounts of waste heat, and effective utilization of this waste heat contributes to energy conservation and environmental protection. Energy conservation and emission reduction within processes, as well as high-quality waste heat utilization, are key approaches to addressing environmental challenges. Increased primary energy demand also increases greenhouse gas emissions. Since primary energy utilization rates are typically low, reducing energy demand can be achieved by improving them.

[0003] The ethylene glycol refining process generates a large amount of waste heat at 130-150°C. The development of energy-saving processes and the effective utilization of waste heat are two important means of reducing ethylene glycol production costs. Therefore, combining ethylene glycol separation processes with low-temperature waste heat utilization technology can achieve higher efficiency and greater energy savings.

[0004] There are many ways to recover and utilize waste heat, including power generation, quality improvement, and refrigeration. Existing waste heat recovery systems are generally not limited to a single method. Combined cooling and power generation systems are an effective means of achieving efficient utilization of low-temperature waste heat.

[0005] Heat integration technology can also be used to achieve energy savings in ethylene glycol plants. Combining a cooling and power cogeneration system with heat integration technology can achieve efficient conversion of waste heat within the plant while maintaining ethylene glycol product purity. This can avoid heat loss caused by heat exchange and improve the energy conversion efficiency of the waste heat recovery system.

[0006] In order to solve the above problems, the present invention provides an ethylene glycol energy-saving device coupled with a cooling and power cogeneration system and a method of using the same to solve the problem of low waste heat utilization in the past. Summary of the Invention

[0007] The purpose of the present invention is to provide an ethylene glycol energy-saving device coupled with a cooling and power cogeneration system and a method for using the same, so as to improve the waste heat utilization rate and the energy conversion efficiency of the waste heat recovery system.

[0008] To achieve the above object, the present invention provides the following solutions:

[0009] A glycol energy-saving device coupled with a combined cooling and power system comprises an ethylene glycol separation device and a combined cooling and power system interconnected, the combined cooling and power system comprising a power generation system and a refrigeration system, the power generation system comprising a first condenser, a first working fluid pump, a first evaporator connected in sequence to form a closed loop, a turbine and an intermediate heat exchanger, the first condenser, the first working fluid pump and the intermediate heat exchanger being connected in a closed loop, the refrigeration system comprising a first regenerator, a second working fluid pump, a flash tank connected in sequence to form a closed loop, a second condenser, a first expansion valve, a second evaporator, an absorber, a second expansion valve and a second regenerator, the first regenerator being connected to the flash tank and the second regenerator respectively, the first evaporator being connected to the first regenerator and being used to drive the first regenerator, the second working fluid pump being connected to the absorber and the second regenerator respectively, and the first evaporator being used to recover waste heat from the ethylene glycol separation device.

[0010] Preferably, the ethylene glycol separation device includes a multiple-effect evaporation device, an ethylene glycol dehydration device, an ethylene glycol refining device and a diethylene glycol refining device, the multiple-effect evaporation device is sequentially connected to a first dehydration tower, a second dehydration tower and a third dehydration tower, the ethylene glycol dehydration device includes a first distillation tower connected to the third dehydration tower, the ethylene glycol refining device includes a second distillation tower connected to the first distillation tower, and the diethylene glycol refining device includes a third distillation tower and a fourth distillation tower connected to the second distillation tower.

[0011] A method for using an ethylene glycol energy-saving device coupled to a cooling and power cogeneration system comprises the following steps:

[0012] The working fluid heated by the waste heat of the glycol separation device passes through the first evaporator to increase its temperature, and then becomes a working gas and enters the turbine. The high-temperature working gas is cooled and depressurized after the turbine generates electricity. The cooled and depressurized working gas passes through the intermediate heat exchanger and the condenser in sequence, and then is further cooled to a liquid phase. The liquid phase working fluid enters the first working fluid pump, and the working fluid discharged from the first working fluid pump enters the intermediate heat exchanger for circulation.

[0013] The secondary waste heat source from the first evaporator drives the first regenerator, and the working fluid is separated into gas and liquid through the flash tank. The gas phase is converted into a low-temperature and low-pressure liquid phase through the second condenser, enters the first expansion valve for pressure reduction, and then evaporates and absorbs heat through the second evaporator, so that the heat exchange fluid is cooled to achieve the purpose of refrigeration; the working fluid in the system after evaporation enters the absorber, obtains a working fluid pair with a certain concentration, and then passes through the second expansion valve to complete a cycle.

[0014] Preferably, the power generated by the turbine is first used for electrical equipment in the ethylene glycol energy-saving device coupled to the combined cooling and power system.

[0015] Preferably, the refrigeration system is used for refrigerating products of an ethylene glycol synthesis unit.

[0016] Compared with the prior art, the present invention has achieved the following technical effects:

[0017] 1. The present invention adopts a heat integration method to combine the power generation system and the absorption refrigeration system to form an independent cogeneration system, which can realize the functions of power generation and refrigeration at the same time. While achieving the purity of the ethylene glycol product, it can also realize the efficient conversion of waste heat in the device, avoid the heat loss caused by heat exchange, and improve the energy conversion efficiency of the waste heat recovery system.

[0018] 2. The present invention uses the overhead steam from the first dehydration tower as the heat source for the reboiler in the bottom of the second dehydration tower, and the overhead steam from the second dehydration tower as the heat source for the reboiler in the bottom of the third dehydration tower, saving significant heating steam consumption through multi-effect evaporation. Ethylene glycol dehydration uses the overhead steam from the third dehydration tower as the heat source for the reboiler in the bottom of the first distillation tower to remove excess moisture from the stream. Ethylene glycol refining uses the overhead steam from the second distillation tower, which is pressurized by a compressor to high-temperature, high-pressure steam, as the heat source for the bottom of the second distillation tower. Diethylene glycol refining uses high- and low-pressure towers, the third distillation tower, and the fourth distillation tower to separate high-purity diethylene glycol and triethylene glycol through pressure swing distillation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 It is a structural flow chart of the present invention;

[0021] Among them, the first evaporator 1, the turbine 2, the intermediate heat exchanger 3, the first condenser 4, the first working fluid pump 5, the first regenerator 6, the flash tank 7, the second condenser 8, the first expansion valve 9, the second evaporator 10, the absorber 11, the second expansion valve 12, the second working fluid pump 13, the first dehydration tower T101, the second dehydration tower T102, the third dehydration tower T103, the first distillation tower T104, the second distillation tower T105, the third distillation tower T106, and the fourth distillation tower T107. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0023] The purpose of the present invention is to provide an ethylene glycol energy-saving device coupled with a cooling and power cogeneration system and a method for using the same, so as to improve the waste heat utilization rate and the energy conversion efficiency of the waste heat recovery system.

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] refer to Figure 1 , a glycol energy-saving device coupled with a cooling and power cogeneration system, comprising an ethylene glycol separation device and a cooling and power cogeneration system that are interconnected, the cooling and power cogeneration system comprising a power generation system and a refrigeration system, the power generation system comprising a first condenser, a first working fluid pump, a first evaporator, a turbine and an intermediate heat exchanger that are sequentially connected to form a closed loop, the first condenser, the first working fluid pump and the intermediate heat exchanger are closed-loop connected, the refrigeration system comprising a first regenerator, a second working fluid pump, a flash tank, a second condenser, a first expansion valve, a second evaporator, an absorber, a second expansion valve and a second regenerator that are sequentially closed-loop connected, the first regenerator They are respectively connected to the flash tank and the second regenerator, the first evaporator is connected to the first regenerator and is used to drive the first regenerator, the second working fluid pump is respectively connected to the absorber and the second regenerator, and the first evaporator is used to recover the waste heat of the ethylene glycol separation device; the present invention adopts a heat integration method to combine the power generation system and the absorption refrigeration system to form an independent cogeneration system, which can simultaneously realize the functions of power generation and refrigeration, and can achieve efficient conversion of waste heat in the device while achieving the purity of the ethylene glycol product, thereby avoiding heat loss caused by heat exchange and improving the energy conversion efficiency of the waste heat recovery system.

[0026] In the power generation process, the low-temperature waste heat is used to heat the first evaporator to convert the working fluid into a high-temperature, high-pressure gas. This gas drives the turbine to expand and generate electricity. The exhaust steam at the turbine outlet is used to preheat the working fluid and then enters the condenser for liquefaction. It is then pressurized by the working fluid pump and enters the first evaporator, thus completing a power generation cycle.

[0027] The refrigeration part uses low-temperature waste heat to heat the first regenerator to vaporize the working fluid, and performs gas-liquid separation in the flash tank. The absorbent in the tower bottom preheats the working fluid at the inlet of the second regenerator and then enters the absorber. The working fluid gas at the top of the tower is cooled and liquefied by the second condenser, and is reduced in pressure by the first expansion valve to become a low-temperature and low-pressure liquid. The low-temperature water returns to heat the second evaporator and then cools down to become low-temperature water. The working fluid is vaporized and enters the absorber. After being absorbed by the absorbent, it enters the second regenerator through the second expansion valve to complete a refrigeration cycle.

[0028] refer to Figure 1 The ethylene glycol separation device includes a multi-effect evaporation device, an ethylene glycol dehydration device, an ethylene glycol refining device and a diethylene glycol refining device. The multi-effect evaporation device is connected to a first dehydration tower, a second dehydration tower and a third dehydration tower in sequence. The ethylene glycol dehydration device includes a first rectifying tower connected to the third dehydration tower. The ethylene glycol refining device includes a second rectifying tower connected to the first rectifying tower. The diethylene glycol refining device includes a third rectifying tower and a fourth rectifying tower connected to the second rectifying tower. The top steam of the first dehydration tower is used as the heat source for the reboiler of the bottom of the second dehydration tower, and the top steam of the second dehydration tower is used as the heat source for the reboiler of the bottom of the third dehydration tower. A large amount of heating steam consumption is saved through multi-effect evaporation. For ethylene glycol dehydration, the top steam of the third dehydration tower is used as the heat source for the reboiler of the first distillation tower kettle to remove the remaining water in the stream. For ethylene glycol refining, the top steam of the second distillation tower is pressurized by a compressor to become high-temperature and high-pressure steam, which is used as the heat source for the kettle of the second distillation tower. For diethylene glycol refining, high- and low-pressure towers, the third distillation tower, and the fourth distillation tower are used for pressure swing distillation to separate high-purity diethylene glycol and triethylene glycol.

[0029] A method for using an ethylene glycol energy-saving device coupled to a cooling and power cogeneration system comprises the following steps:

[0030] The working fluid heated by the waste heat of the glycol separation device passes through the first evaporator to increase its temperature, then becomes a working gas and enters the turbine. The high-temperature working gas is cooled and depressurized after the turbine generates electricity. The cooled and depressurized working gas passes through the intermediate heat exchanger and the condenser in sequence, and is further cooled to a liquid phase. The liquid phase working fluid enters the first working fluid pump, and the working fluid discharged from the first working fluid pump enters the intermediate heat exchanger for circulation.

[0031] The secondary waste heat source from the first evaporator drives the first regenerator, and the working fluid is separated into gas and liquid through the flash tank. The gas phase is converted into a low-temperature and low-pressure liquid phase through the second condenser, enters the first expansion valve for pressure reduction, and then evaporates and absorbs heat through the second evaporator, so that the heat exchange fluid is cooled to achieve the purpose of refrigeration; the working fluid in the system after evaporation enters the absorber, obtains a working fluid pair with a certain concentration, and then passes through the second expansion valve to complete a cycle.

[0032] Furthermore, the electricity generated by the turbine is first used for electrical equipment in the ethylene glycol energy-saving device coupled to the combined cooling and power generation system.

[0033] Furthermore, the refrigeration system is used for refrigerating the products of the ethylene glycol synthesis unit.

[0034] Adaptive changes based on actual needs are all within the scope of protection of the present invention.

[0035] It should be noted that it will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the present invention is defined by the appended claims, not the foregoing description, and it is intended that all variations within the meaning and range of equivalents of the claims be encompassed therein. Any reference signs in the claims should not be construed as limiting the claim to which they relate.

Claims

1. An ethylene glycol energy-saving device coupled with a cooling and power cogeneration system, characterized in that: It includes an ethylene glycol separation device and a combined cooling and power generation system that are interconnected. The combined cooling and power generation system includes a power generation system and a refrigeration system. The power generation system includes a first condenser, a first working fluid pump, a first evaporator, a turbine, and an intermediate heat exchanger that are sequentially connected to form a closed loop. The first condenser, the first working fluid pump, and the intermediate heat exchanger are closed-loop connected. The refrigeration system includes a first regenerator, a second working fluid pump, a flash tank, a second condenser, a first expansion valve, a second evaporator, an absorber, a second expansion valve, and a second regenerator that are sequentially closed and connected. The first regenerator is respectively connected to the flash tank and the second regenerator. The first evaporator is connected to the first regenerator and is used to drive the first regenerator. The second working fluid pump is respectively connected to the absorber and the second regenerator. The first evaporator is used to recover waste heat from the ethylene glycol separation device. The ethylene glycol separation device includes a multi-effect evaporation device, an ethylene glycol dehydration device, an ethylene glycol refining device and a diethylene glycol refining device. The multi-effect evaporation device is sequentially connected to a first dehydration tower, a second dehydration tower and a third dehydration tower. The ethylene glycol dehydration device includes a first distillation tower connected to the third dehydration tower. The ethylene glycol refining device includes a second distillation tower connected to the first distillation tower. The diethylene glycol refining device includes a third distillation tower and a fourth distillation tower connected to the second distillation tower.

2. A method for using an ethylene glycol energy-saving device coupled to a cooling and power cogeneration system, characterized in that: The ethylene glycol energy-saving device for coupling cooling and power cogeneration system according to claim 1 comprises the following steps: The working fluid heated by the waste heat of the glycol separation device passes through the first evaporator to increase its temperature, and then becomes a working gas and enters the turbine. The high-temperature working gas is cooled and depressurized after the turbine generates electricity. The cooled and depressurized working gas passes through the intermediate heat exchanger and the condenser in sequence, and then is further cooled to a liquid phase. The liquid phase working fluid enters the first working fluid pump, and the working fluid discharged from the first working fluid pump enters the intermediate heat exchanger for circulation. The secondary waste heat source from the first evaporator drives the first regenerator, and the working fluid is separated into gas and liquid through the flash tank. The gas phase is converted into a low-temperature and low-pressure liquid phase through the second condenser, enters the first expansion valve for pressure reduction, and then evaporates and absorbs heat through the second evaporator, so that the heat exchange fluid is cooled to achieve the purpose of refrigeration; the working fluid in the system after evaporation enters the absorber, obtains a working fluid pair with a certain concentration, and then passes through the second expansion valve to complete a cycle.

3. The method for using the ethylene glycol energy-saving device coupled with a combined cooling and power generation system according to claim 2, characterized in that: The power generated by the turbine is first used for electrical equipment in the ethylene glycol energy-saving device coupled to the combined cooling and power generation system.

4. The method for using the ethylene glycol energy-saving device coupled to a cooling and power cogeneration system according to claim 2, wherein the refrigeration system is used for refrigerating products of the ethylene glycol synthesis device.

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