Method for recycling energy in high-pressure liquid easy to vaporize through hydraulic turbine

Abstract

The invention relates to the technical field of chemical engineering, in particular to a method for recycling energy in easy-to-vaporize high-pressure liquid through a hydraulic turbine. Comprising the following steps: performing heat exchange and cooling on a liquid-phase product after high-pressure reaction, recovering high-pressure energy by a hydraulic turbine, performing flash evaporation on low-pressure fluid, and enabling a gas phase and a liquid phase to enter subsequent separation equipment. Comprising the following steps: carrying out chemical reaction on a high-pressure liquid-phase raw material through a reactor to obtain a reaction product mainly containing a liquid phase; carrying out heat exchange and cooling on the reacted high-pressure liquid-phase fluid by using a liquid phase obtained by flash evaporation equipment to obtain a gas-phase and liquid-phase mixed fluid; the cooled high-pressure liquid-phase fluid converts pressure energy into mechanical energy through a hydraulic turbine; the low-pressure fluid is introduced into flash evaporation equipment for flash evaporation, and a gas phase and a liquid phase are obtained; and a gas phase and a liquid phase obtained after heat exchange between the gas phase of the low-pressure flash evaporation equipment and the high-pressure liquid phase fluid are introduced into subsequent separation equipment. By means of the characteristic of the high-pressure liquid easy to vaporize, the high-pressure liquid is cooled and then introduced into the hydraulic turbine to recover pressure energy, and energy conservation and consumption reduction of a chemical device are achieved.

Description

Technical Field

[0001] The present invention relates to the field of chemical technology, and more specifically, to a method for recovering energy from easily vaporizable high-pressure liquid by utilizing a hydraulic turbine. Background Art

[0002] High-pressure liquid is generated during the chemical production process. The pressure energy of the high-pressure liquid can be recovered by using a hydraulic turbine and converted into rotational mechanical energy to drive other mechanical equipment to work, thus completing the energy recovery of the high-pressure liquid.

[0003] At present, hydraulic turbines have been widely used in chemical hydrogenation units, synthetic ammonia units, ethylene oxide / ethylene glycol unit absorption section, etc. Xu Chongwen listed the typical turbine application units in the industry in "Characteristics and Applications of Energy Recovery Hydraulic Turbines" in 2015: 1. Residue oil hydrogenation, diesel hydrogenation, wax oil hydrocracking and heavy oil hydrodesulfurization units; 2. Synthetic ammonia units, ethylene oxide / ethylene glycol units, coal-to-liquid tail gas treatment and gas absorption and analysis systems in high-pressure natural gas purification units; 3. Large-scale liquefied gas units and liquefied air transportation; 4. Reverse osmosis seawater desalination systems, polysilicon industry and other water residual pressure energy utilization; 5. From the high pressure of the pipeline to the tank area to transport finished oil or crude oil and other devices with high and low pressure heads. Zheng Xuepeng listed the typical parameters of the hydraulic turbine of the hydrogenation unit in "Design Analysis of Hydraulic Turbines in Refining Units" in 2012, and explained the vaporization rate at the turbine outlet. The general vaporization rate is not high, and the volume ratio is less than 3%. The article draws a schematic diagram of the hydraulic turbine process. The reaction products pass through the hot high-pressure separator, enter the hydraulic turbine, and then enter the hot low-pressure separation system.

[0004] Among the existing hydraulic turbine patents, Patent CN 110296033 invented a gas-liquid two-phase liquid turbine volute to solve the problem of reduced turbine efficiency caused by gas-liquid separation of the working fluid in the volute, but the effect of solving the reduced turbine efficiency is limited. Patent CN 102900477 invented a specific application of a hydraulic turbine, which is suitable for lean liquid energy recovery, where the gas content in the lean liquid is low and the lean liquid is not easy to vaporize. Patent CN 221424614 invented a rapid shutdown device after a hydraulic turbine between the high-pressure tower and the low-pressure tower fails, which is suitable for absorption and analysis processes, and the gas content in the high-pressure lean liquid is low. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for recovering energy from easily vaporized high-pressure liquid using a hydraulic turbine, thereby achieving energy saving and consumption reduction in chemical equipment by recovering the pressure energy from the easily vaporized high-pressure liquid.

[0006] In order to achieve the above-mentioned purpose, the present invention provides a method for recovering energy from easily vaporized high-pressure liquid by using a hydraulic turbine, comprising: heat exchange and cooling of the liquid product after the high-pressure reaction, recovery of high-pressure energy by a hydraulic turbine, flash evaporation of the low-pressure fluid, and entry of the gas phase and the liquid phase into subsequent separation equipment.

[0007] In chemical enterprises, a large amount of high-pressure liquid pressure energy is not utilized. At present, hydraulic turbines are widely used in hydrogenation units and gas absorption and analysis units. For high-pressure liquids that are easy to vaporize, there is currently no hydraulic turbine to recover pressure energy in the industry. The main reason is that hydraulic turbines can only process high-pressure liquids with a volume content of less than 20% at the outlet of the hydraulic turbine, and as the gas content increases, the gas-liquid two-phase flow causes the efficiency of the hydraulic turbine to drop significantly.

[0008] The economics must be considered when recovering the pressure energy of high-pressure liquids with hydraulic turbines. Based on the investment experience of hydraulic turbines, control systems, and related supporting equipment, it is considered economically feasible for a single-stage hydraulic turbine to recover power greater than 22kw and a multi-stage hydraulic turbine to recover power greater than 75kw. For high-pressure liquids that are not economically feasible to set up hydraulic turbines alone, they can be combined and adjusted in the chemical process, and multiple groups of logistics can be merged into the same hydraulic turbine to recover pressure energy.

[0009] The easily vaporizable high-pressure liquid described in the present invention refers to a fluid having a liquid phase content greater than 50 wt% after a liquid phase reaction, and a large amount of liquid phase will be vaporized after the pressure is reduced.

[0010] Based on the above analysis, the present invention is implemented by the following steps, each of which has the following characteristics:

[0011] (1) The high-pressure fluid product mainly in the liquid phase obtained through high-temperature and high-pressure chemical reaction is subjected to heat exchange and cooling.

[0012] The pressure in the high-pressure chemical reaction is greater than 0.8 MPa, and the reaction product is mainly liquid, with a liquid content of >50wt%. The difference from the existing hydraulic turbine application scenario is that the main components in the reaction product in the existing hydraulic turbine application scenario have large differences in boiling points. Gas-liquid separation before the hydraulic turbine can separate the light components that affect the hydraulic turbine. The components entering the hydraulic turbine are liquids that are not easy to vaporize, and the gas light components are usually obtained through gas-liquid separation and returned to the reactor through the circulation compressor.

[0013] The boiling point of liquid decreases with the decrease of pressure. The purpose of heat exchange and cooling of high-pressure fluid is to keep the liquid temperature lower than the boiling point of the remaining raw materials and the main reaction products after the pressure reduction by the hydraulic turbine. The temperature after high-pressure reaction is usually greater than 60°C.

[0014] (2) The cooled high-pressure fluid obtained in step S1 is passed through a hydraulic turbine to obtain a low-pressure fluid, and the pressure energy is converted into mechanical energy.

[0015] Low-pressure fluid is relative to high-pressure reaction, and the pressure is usually more than 0.5MPa lower than that of high-pressure reaction. The difference from the existing hydraulic turbine application scenario is that within the existing hydraulic turbine working pressure range, the remaining raw materials and main reaction products in the fluid will not be vaporized in large quantities. The reason is that a large amount of gas in the hydrogenation unit has been separated in the hot high-pressure separation and cold high-pressure separation; the absorption and analysis process is accompanied by chemical reactions, and the liquid phase is stable within the hydraulic turbine working pressure range, and basically no analysis occurs.

[0016] (3) The low-pressure fluid obtained in step S2 is passed into a flash evaporation device for pressure reduction flash evaporation to obtain a first gas phase and a first liquid phase; or the low-pressure fluid is not separated into gas and liquid phases, and the low-pressure fluid is separated into n liquid phase material streams (n≥1).

[0017] By reducing the pressure, the boiling points of the components in the low-pressure fluid are reduced. In this step, the boiling points of the m components are lower than the outlet temperature of the hydraulic turbine, and the m components evaporate and boil to obtain a first gas phase and a first liquid phase, wherein m≥1.

[0018] The low-pressure fluid does not separate the gas and liquid phases, and the low-pressure fluid separates n liquid phase material streams (n≥1). After the high-pressure fluid passes through step S1, the temperature has dropped to a sufficiently low level. After passing through the hydraulic turbine, the low-pressure fluid continues to reduce the pressure to the feed pressure of the subsequent separation equipment, and the main components will not evaporate or boil quickly. Therefore, there is no engineering significance for gas-liquid separation. This step is replaced by separating part of the low-pressure fluid for heat exchange and temperature increase.

[0019] (4) The first liquid phase obtained in step S3 is subjected to heat exchange and temperature increase to further obtain a second gas phase and a second liquid phase, and the first gas phase obtained in step S3 and the second gas phase and the second liquid phase obtained in step S4 are introduced into a subsequent separation device for separation; or the n liquid phase material streams obtained in step S3 are respectively introduced into n heat exchangers for heat exchange and temperature increase to obtain n groups of Nn-th gas phases and Nn-th liquid phases, and then all the n groups of Nn-th gas phases and Nn-th liquid phases are introduced into a subsequent separation device for separation; or the first gas phase and the first liquid phase obtained in step S3 are directly introduced into a subsequent separation device for separation.

[0020] The boiling point of the m components is lower than the temperature of the hot fluid, and the m components are evaporated by heat exchange and temperature rise to obtain a gas phase, m ≥ 1. The purpose of this step is to absorb heat, increase the enthalpy of the liquid phase, and obtain a second gas phase and a second liquid phase.

[0021] When the subsequent separation equipment is a multiple-effect evaporator, n liquid components can be passed into n heat exchangers for heat exchange and temperature increase, and Nn gas phases and Nn liquid phases can be passed into different effects of the multiple-effect evaporator according to pressure, so that the temperature of the high-pressure fluid after cooling is the lowest.

[0022] The first gas phase and the first liquid phase after flash evaporation realize the separation of light and heavy components, and the effect is similar to a theoretical plate. The gas phase and liquid phase are respectively passed into the subsequent separation equipment to reduce the separation energy consumption.

[0023] Furthermore, in step S1, heat exchange and cooling is the energy exchange between the first hot fluid and the first cold fluid, the first hot fluid is the high-pressure fluid product mainly in liquid phase described in step S1, and the first cold fluid is a fluid with a lower temperature than the high-pressure fluid product in step S1. The first cold fluid is the first liquid phase of step S3 and / or other fluids with a lower temperature than the high-pressure fluid product in step S1.

[0024] Furthermore, in step S2, the mechanical energy is used to generate electricity and / or as a power source for other rotating equipment. For easily vaporized high-pressure liquid, if heat exchange and cooling in step S1 is not performed, the gas phase volume ratio in the low-pressure fluid after decompression is greater than 20%, and the hydraulic turbine cannot be used.

[0025] Furthermore, the first gas phase and the first liquid phase obtained in S4 are passed into a subsequent separation device. When the temperature of the hot fluid is high enough to be directly used as a reboiling heat source for the separation device, this step can save investment in heat exchangers.

[0026] Furthermore, in step S1, at least one component of the reaction product is a liquid phase, and the liquid phase content is greater than 50wt%. After the reaction, the first hot fluid cannot use a gas-liquid separation tank to obtain a gas phase and circulate back to the reactor. High-pressure chemical reactions are liquid-phase exothermic reactions, and the purpose of high pressure is to ensure that the boiling points of the remaining raw materials and main reaction products after the reaction are higher than the temperature of the reaction products. For the hot high-separation and cold high-separation hydraulic turbines of hydrogenation units that are currently widely used, it is easy to separate low-boiling point components such as hydrogen through hot high-separation and cold high-separation, and circulate back to the reactor for continued use, thereby ensuring that the gas content in the subsequent hydraulic turbine fluid is low.

[0027] Furthermore, in step S3, the low-pressure fluid is rapidly evaporated and / or boiled by reducing the pressure to obtain a first gas phase and a first liquid phase, and the pressure drop value is greater than 0. The purpose of reducing the pressure is to cause the liquid phase to evaporate and boil, and the pressure drop value is determined according to the physical properties of the components.

[0028] Furthermore, in step S4, heat exchange and heating is the energy exchange between the second cold fluid and the first hot fluid, or the energy exchange between the second cold fluid and other fluids with a temperature higher than the first liquid phase in step S3. The first hot fluid is the high-pressure fluid product mainly in liquid phase described in step S1, and the second cold fluid is the first liquid phase in step S3.

[0029] Further, the subsequent separation equipment in step S4 has a variety of feed combination methods, specifically: the first gas phase and / or the second gas phase and / or the first liquid phase, and / or the second liquid phase, and / or the Nnth gas phase, and / or the Nnth liquid phase in step S4. Different feed combinations are conducive to achieving different separation requirements, and different feed combinations can reduce the energy consumption of the separation equipment.

[0030] Furthermore, in step S4, the subsequent separation equipment is a plate and / or packed tower, or an n-effect evaporation for achieving the same separation purpose, n≥2. The separation equipment uses the different volatility characteristics of each component to achieve separation, which is a physical process. The difference from the existing hydraulic turbine application scenario is that the existing hydraulic turbine subsequently enters the separation equipment, and the separation equipment is a distillation tower, the tower product is fuel gas, and the tower bottom is gasoline, diesel, etc. The boiling points of the components are greatly different. Within the pressure range of the hydraulic turbine, a large amount of gas will not be generated due to vapor-liquid equilibrium.

[0031] Furthermore, in the step S2, the high-pressure fluid is always kept in a state of liquid phase>70wt% when the pressure is reduced by the hydraulic turbine.

[0032] The beneficial effects of the present invention are:

[0033] 1. Use hydraulic turbine to recover pressure energy from easily vaporized high-pressure liquid;

[0034] 2. Reduce the energy consumption of separation equipment by feeding gas phase and liquid phase separately, and achieve energy saving and consumption reduction in chemical equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative labor.

[0036] Figure 1 This is a process flow diagram of recovering the pressure energy of easily vaporized liquid by using a hydraulic turbine in the production of ethylbenzene by liquid phase alkylation according to Example 1 of the present invention;

[0037] Wherein: 1-alkylation reactor, 2-transalkylation reactor, 4-heat exchanger, 5-bypass device, 6-flash tank (one), 7-plate tower (one), 10-flash tank (two), 12-hydraulic turbine;

[0038] Figure 2 This is a process flow diagram of recovering the pressure energy of easily vaporized liquid by using a hydraulic turbine in the hydration of water and ethylene oxide to produce ethylene glycol according to Example 4 of the present invention;

[0039] Among them: 3-hydration reactor, 4-heat exchanger, 5-bypass equipment, 7-plate tower (one), 8-plate tower (two), 9-reboiler, 11-regulating valve group, 12-hydraulic turbine.

[0040] Figure 3 This is a process flow diagram of recovering the pressure energy of easily vaporized liquid by using a hydraulic turbine in the hydration of water and ethylene oxide to produce ethylene glycol according to Example 5 of the present invention;

[0041] Among them: 3-hydration reactor, 4-1-heat exchanger, 4-2-heat exchanger, 5-bypass equipment, 7-plate tower (one), 8-plate tower (two), 9-reboiler, 11-regulating valve group, 12-hydraulic turbine. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings, but the scope of protection of the present invention is not limited to the following. Any feature disclosed in this specification (including any additional claims, abstract and drawings) can be replaced by other equivalent or alternative features with similar purposes unless otherwise stated. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Various terms appearing in the present application are only used for the purpose of describing specific embodiments and are not intended to be limiting of the present invention; unless the context clearly indicates otherwise, the singular form is intended to include the plural form as well.

[0045] When the terms "include" and / or "comprising" are used in this specification, these terms indicate the existence of the stated features, integers, steps, operations, elements and / or parts, but do not exclude the existence and / or addition of one or more other features, integers, steps, operations, elements, parts and / or groups thereof.

[0046] As described in the background art, the existing hydraulic turbine pressure energy recovery technology does not involve the pressure energy recovery of easily vaporized high-pressure liquid. In order to solve the above problem, the present invention proposes the following technical solution.

[0047] The present invention cools down the liquid phase product after high-pressure reaction by heat exchange, recovers high-pressure energy by hydraulic turbine, flashes low-pressure fluid, and enters the gas phase and liquid phase into the subsequent separation equipment, thereby realizing the recovery of easily vaporized hydraulic pressure energy by hydraulic turbine and reducing separation energy consumption.

[0048] The method comprises the following steps: a high-pressure liquid phase raw material is subjected to a chemical reaction in a reactor to obtain a reaction product mainly in a liquid phase; the high-pressure liquid phase fluid after the reaction is subjected to heat exchange and cooling with a liquid phase obtained by a flash evaporation device to obtain a gas phase and a liquid phase mixed fluid; the high-pressure liquid phase fluid after cooling is subjected to a hydraulic turbine to convert the pressure energy into mechanical energy; a low-pressure fluid is passed into a flash evaporation device for flash evaporation to obtain a gas phase and a liquid phase; the gas phase of the low-pressure flash evaporation device and the gas phase and liquid phase obtained after heat exchange with the high-pressure liquid phase fluid are passed into a subsequent separation device.

[0049] Specifically, the recycling method comprises the following steps:

[0050] S1. Heat exchange and cooling of the high-pressure fluid product mainly in liquid phase obtained through high-temperature and high-pressure chemical reaction;

[0051] S2, passing the cooled high-pressure fluid obtained in step S1 through a hydraulic turbine to obtain a low-pressure fluid, and converting the pressure energy into mechanical energy;

[0052] S3, passing the low-pressure fluid obtained in step S2 into a flash evaporation device for pressure-reducing flash evaporation to obtain a first gas phase and a first liquid phase;

[0053] Or the low-pressure fluid does not separate the gas and liquid phases, and the low-pressure fluid is separated into n liquid phase material streams (n≥1);

[0054] S4, exchanging heat with the first liquid phase obtained in step S3 to further obtain a second gas phase and a second liquid phase, and passing the first gas phase obtained in step S3, the second gas phase obtained in step S4, and the second liquid phase into a subsequent separation device for separation;

[0055] Alternatively, the n liquid-phase material streams obtained in step S3 are respectively passed into n heat exchangers for heat exchange and temperature increase, and n groups of Nn-th gas phases and Nn-th liquid phases are correspondingly obtained, and then all the Nn-th gas phases and Nn-th liquid phases of the n groups are passed into subsequent separation equipment for separation;

[0056] Alternatively, the first gas phase and the first liquid phase obtained in step S3 are directly introduced into a subsequent separation device for separation.

[0057] In step S1, the high-pressure fluid product mainly composed of liquid phase has at least one component as liquid phase, and the liquid phase content is greater than 50wt%.

[0058] In step S1, heat exchange and cooling is the energy exchange between the first hot fluid and the first cold fluid. The first hot fluid is the high-pressure fluid product mainly in liquid phase described in step S1, and the first cold fluid is a fluid with a lower temperature than the high-pressure fluid product in step S1.

[0059] The first cold fluid is the first liquid phase of step S3 and / or other fluids having a lower temperature than the high-pressure fluid product in step S1.

[0060] In step S2, the mechanical energy is used to generate electricity and / or as a power source for other rotating equipment.

[0061] In step S3, the low-pressure fluid is rapidly evaporated and / or boiled by reducing the pressure to obtain a first gas phase and a first liquid phase, and the pressure drop value is greater than 0.

[0062] In step S4, heat exchange and heating is the energy exchange between the second cold fluid and the first hot fluid, or the energy exchange between the second cold fluid and other fluids with a temperature higher than the first liquid phase in step S3. The first hot fluid is the high-pressure fluid product mainly in liquid phase described in step S1, and the second cold fluid is the first liquid phase in step S3.

[0063] In step S4, the subsequent separation equipment is a plate and / or packed tower, or n-effect evaporation for achieving the same separation purpose, n≥2.

[0064] In the step S2, the high-pressure fluid is always kept in a state of liquid phase>70wt% when the pressure is reduced by the hydraulic turbine.

[0065] Embodiment 1, as Figure 1 As shown, the process of recovering the pressure energy of the easily vaporized liquid by using a hydraulic turbine in the production of ethylbenzene by liquid phase alkylation comprises the following steps:

[0066] Step (1), 220°C, 180t / h benzene, 130°C, 21.7t / h ethylene are introduced into a liquid phase alkylation reactor for chemical reaction, and the reaction is an exothermic reaction. The reaction product parameters are 250°C, 3200kPa, 201.7t / h, and all are liquid phase. The reactant product composition is: unreacted raw material benzene 64.3wt%, reaction product ethylbenzene 29.6wt%, reaction product diethylbenzene 5.4wt%, heavy component 0.2wt%, light component 0.2wt%.

[0067] 210℃, 42t / h benzene and 210℃, 17t / h diethylbenzene are introduced into the liquid phase transalkylation reactor for chemical reaction, and the reaction is an exothermic reaction. The reaction product parameters are 215℃, 3250kPa, 65.8t / h, all in liquid phase. The reactant product composition is: unreacted raw material benzene 62.3wt%, unreacted raw material diethylbenzene 6.3wt%, reaction product ethylbenzene 30.5wt%, heavy component 0.5wt%, light component 0.2wt%.

[0068] The alkylation reaction product and the transalkylation reaction product are all in liquid phase. The two reaction products can be recovered by hydraulic turbines respectively to recover pressure energy, but considering the economic efficiency of implementation, and the two reaction products enter the same plate tower for separation, the two reaction products are combined in Example 1. The parameters after the combination are 239°C, 3200kPa, 267.5t / h, and all are in liquid phase.

[0069] Step (2) uses a liquid phase at 182°C, 800 KPa, and 235 t / h to exchange heat with the reaction product in a heat exchanger 4. The first hot fluid is the reaction product of the alkylation reactor 1 and the transalkylation reactor 2, and the first cold fluid is the flash liquid phase of the flash tank (II) 10. The heat exchanger uses a kettle reboiler. After heat exchange, the temperature of the reaction product drops to 192°C, and the temperature of the flash liquid phase rises to 189°C.

[0070] Step (3), the high pressure fluid after cooling through the heat exchanger 4 is passed into the hydraulic turbine 12. The hydraulic turbine adopts a two-stage impeller to convert the mechanical energy of the hydraulic turbine into electrical energy with an efficiency of 75%. The hydraulic turbine inlet pressure is 3200KPa, the outlet is 1050KPa, and the outlet fluid is all liquid phase. The 217kw pressure energy is converted into 162kw electrical energy. A bypass device 5 is set. When the hydraulic turbine fails, the bypass device automatically switches to ensure the normal operation of the chemical process.

[0071] Step (4) is to reduce the pressure of the low-pressure fluid having a pressure of 1050 KPa passing through the hydraulic turbine and flash evaporate. The pressure in the flash tank (II) 10 is reduced to 800 KPa, and a wire mesh demister is provided at the gas phase outlet at the top of the flash tank. The liquid evaporates rapidly into a first gas phase and a first liquid phase. The temperature drops from 191°C to 182°C during the flash evaporate process.

[0072] Step (5), the first liquid phase at the bottom of the flash tank (II) 10 is passed into the heat exchanger 4, and is used as the second cold fluid to absorb heat and increase temperature. The cold fluid pressure out of the heat exchanger 4 is 750 KPa and the temperature is 189°C. In the heat exchanger 4, the cold fluid undergoes a phase change, and the liquid phase absorbs heat and changes into a gas phase.

[0073] Step (6), pass the cold fluid out of the heat exchanger 4 into the flash tank (one) 6. At this time, the gas phase is 44.9wt%, so there is no need for reduced pressure flashing. The second gas phase and the second liquid phase are obtained through the flash tank (one). The subsequent separation equipment is a plate tower, and the control indicators are the benzene content at the bottom of the tower and the ethylbenzene content at the top of the tower. In the order of the first gas phase of the flash tank (two), the second gas phase of the flash tank (one), and the second liquid phase of the flash tank (one), they are respectively passed into the plate tower from bottom to top. The products at the top and bottom of the tower are qualified. The reboiler load is 24690kw.

[0074] Comparative Example 1 does not use cooling, hydraulic turbine, or flash tank structure, and directly introduces the alkylation reaction product and the transalkylation reaction product into a plate tower, with a bottom reboiler load of 24700 kW.

[0075] The energy consumption of the plate tower of the separation equipment in Example 1 is equivalent to that in Comparative Example 1, and Example 1 recovers 217KW of pressure energy.

[0076] Example 2, using a hydraulic turbine to recover the pressure energy of easily vaporized liquid in liquid phase alkylation to produce ethylbenzene, comprises the following steps:

[0077] Step (1) is the same as step (1) of Example 1.

[0078] Step (2): In step 2, 95°C hot water in the device is used as the cold fluid, and the hot fluid is cooled to 192°C by heat exchange in the heat exchanger 4.

[0079] Step (3) is the same as step (3) in Example 1.

[0080] Step (4) is the same as step (4) in Example 1.

[0081] Step (5), according to the order of the first gas phase of the flash tank (II) and the first liquid phase of the flash tank (II), they are respectively introduced into the plate tower from bottom to top. The reboiler load is 24800kw. Compared with comparative example 1, the reboiler energy consumption is increased, but the high-pressure liquid energy recovery is achieved.

[0082] Example 3, using a hydraulic turbine to recover the pressure energy of easily vaporized liquid in the production of cumene by liquid phase alkylation, comprises the following steps:

[0083] Step (1) is similar to step (1) of Example 1, except that benzene and propylene are introduced into a liquid phase alkylation reactor, and the reaction products are all liquid; benzene and dipropylbenzene are introduced into a liquid phase transalkylation reactor, and the reaction products are all liquid. The reaction temperature, pressure, and composition of the reaction products are different.

[0084] Step (2) is similar to Example 1 (2), except for the temperature, pressure and components.

[0085] Step (3) is similar to step (3) of Example 1, except that 111 kw of pressure energy is converted into 83 kw of electrical energy.

[0086] Step (4), step (5), and step (6) are similar to step (4), step (5), and step (6) of Example 1. The differences are temperature, pressure, composition, and reboiler load of 22510 kW.

[0087] Comparative Example 3 does not use cooling, hydraulic turbine, or flash tank structure, and directly introduces the alkylation reaction product and the transalkylation reaction product into a plate tower, with a bottom reboiler load of 22,500 kW.

[0088] The energy consumption of the plate tower of the separation equipment in Example 3 is equivalent to that in Comparative Example 3, and Example 1 recovers 83KW of pressure energy.

[0089] Embodiment 4, as Figure 2 As shown, the process of recovering the pressure energy of the easily vaporized liquid by a hydraulic turbine during the hydration of water and ethylene oxide to produce ethylene glycol comprises the following steps:

[0090] Step (1), 185°C, 69t / h ethylene oxide, 185°C, 876t / h water are introduced into the liquid phase hydration reactor 3 for chemical reaction, and the reaction is an exothermic reaction. The reaction product parameters are 221°C, 3730kPa, 945t / h, and all are liquid phase. The reactant product composition is: unreacted raw material water 88.6wt%, reaction product monoethylene glycol 10.2wt%, heavy component 1.1wt%, light component 0.06wt%.

[0091] Step (2) uses a first cold fluid of 205°C, 2040KPa, and 48t / h to exchange heat with the reaction product in a heat exchanger 4. The first hot fluid is the hydration reaction product, the first cold fluid is a 48t / h liquid phase at the outlet of the hydraulic turbine, and the heat exchanger uses a kettle reboiler. After heat exchange, the temperature of the reaction product is reduced to 216°C. The temperature of the cold fluid is 203°C and the pressure is 1540KPa.

[0092] Step (3) is similar to Example 1, except that the inlet pressure of the hydraulic turbine 12 is 3730 KPa and the outlet pressure is 2050 KPa. The 617 kw pressure energy is converted into 462 kw electrical energy.

[0093] Step (4), the low-pressure liquid with a pressure of 2050 KPa passing through the hydraulic turbine is pressure-regulated through the regulating valve group 11.

[0094] Reasons for not flashing: Due to the physical properties of the fluid, when the pressure drop of the flash evaporation is 0.1 MPa, the flash gas phase volume is 0.006wt%. There is no significance in setting up a flash tank in engineering.

[0095] Step (5), the fluid after the hydraulic turbine is divided into two streams, one liquid phase stream with a temperature of 205°C, 2040KPa, and 48t / h, and the other liquid phase stream with a temperature of 205°C, 2040KPa, and 908t / h. The 48t / h stream is passed into the heat exchanger 4 as the second cold fluid to absorb heat and increase temperature. The cold fluid pressure out of the heat exchanger 4 is 1540KPa and the temperature is 203°C. In the heat exchanger 4, the second cold fluid undergoes a phase change, and the liquid phase absorbs heat and changes into a gas phase.

[0096] Step (6), the gas phase fraction of the cold fluid out of the heat exchanger 4 is 43.5wt%. The subsequent separation equipment is 3 multi-effect distillation towers, and the control index is the water content at the bottom of the tower. From the separation effect, the multi-effect distillation tower can be considered as a distillation tower. The difference is that the multi-effect distillation tower integrates heat and utilizes pressure difference, which is more energy-efficient. 48t of cold fluid with a gas phase fraction of 43.5wt% at the outlet of the heat exchanger 4 is passed into the plate tower (two) 8. Another 908t of fluid at the outlet of the hydraulic turbine passes through the regulating valve group 11 and enters the plate tower (one) 7. The water content at the bottom of the tower is qualified. The reboiler load is 85093kw.

[0097] Comparative Example 4 does not use cooling, hydraulic turbine, and fluid vaporization structure. The hydration reaction product is sequentially introduced into three multi-effect distillation towers, and the load of the tower bottom reboiler is 85321kw.

[0098] The separation equipment distillation tower of Example 4 saves 228kw of energy compared with Comparative Example 4, mainly because 48t / h of gas phase fraction of 43.5wt% is passed into the plate tower (II), avoiding the heat exchange temperature difference of the reboiler 9, and the heat energy utilization rate is higher. Example 4 recovers 617KW of pressure energy.

[0099] Embodiment 5, as Figure 3 As shown, the process of recovering the pressure energy of the easily vaporized liquid by a hydraulic turbine during the hydration of water and ethylene oxide to produce ethylene glycol comprises the following steps:

[0100] Step (1), same as Example 4 (1).

[0101] Step (2), using the first liquid phase material stream of 215°C, 2040Kpa, 100t / h as the first cold fluid to exchange heat with the reaction product in the heat exchanger 4-1. The first hot fluid is the hydration reaction product, the first cold fluid is a 100t / h liquid phase at the outlet of the hydraulic turbine, and the heat exchanger adopts a falling film heat exchanger. After heat exchange, the temperature of the reaction product is reduced to 218°C. The temperature of the cold fluid remains basically unchanged, the pressure is 2030Kpa, and the gas phase fraction changes from 0 to 0.07wt%. Using the second liquid phase material stream of 215°C, 2040Kpa, 24t / h as the first cold fluid to exchange heat with the reaction product in the heat exchanger 4-2. The first hot fluid is the 218°C hot fluid after the hydration reaction product is heat exchanged in the heat exchanger 4-1, the first cold fluid is a 24t / h liquid phase at the outlet of the hydraulic turbine, and the heat exchanger adopts a kettle reboiler. After heat exchange, the temperature of the reaction product is reduced to 216°C. The cold fluid temperature is 203℃ and the pressure is 1540Kpa

[0102] Step (3), Example 4(3).

[0103] Step (4), Example 4 (4).

[0104] Step (5), the fluid after the hydraulic turbine is divided into three streams, one liquid phase stream with a flow rate of 205°C, 2040KPa, and 100 t / h, one liquid phase stream with a flow rate of 205°C, 2040KPa, and 24 t / h, and one liquid phase stream with a flow rate of 205°C, 2040KPa, and 808 t / h. The first liquid phase stream with a flow rate of 100 t / h is passed into the heat exchanger 4-1, as the first cold fluid, to absorb heat and increase in temperature, and undergoes a phase change in the heat exchanger to obtain the N1th liquid phase and the N1th gas phase. The second liquid phase stream with a flow rate of 24 t / h is passed into the heat exchanger 4-2, as the first cold fluid, to absorb heat and increase in temperature, and undergoes a phase change in the heat exchanger to obtain the N2th liquid phase and the N2th gas phase.

[0105] Step (6), the gas phase fraction of the cold fluid out of heat exchanger 4-1 is 0.07wt%. The gas phase fraction of the cold fluid out of heat exchanger 4-2 is 0.63wt%. The subsequent separation equipment is 3 multi-effect distillation towers, and the control index is the water content at the bottom of the tower. From the separation effect, the multi-effect distillation tower can be considered as a distillation tower, the difference is that the multi-effect distillation tower performs heat integration and pressure difference utilization, which is more energy-efficient. 100t of cold fluid with a gas phase fraction of 0.07wt% at the outlet of heat exchanger 4-1 is passed into plate tower (one) 7. 24t of cold fluid with a gas phase fraction of 0.63wt% at the outlet of heat exchanger 4-2 is passed into plate tower (two) 8. Another 808t of liquid phase material at the outlet of the hydraulic turbine passes through the regulating valve group 11 and enters the plate tower (one) 7. The water content at the bottom of the tower is qualified. The reboiler load is 85099kw. Comparing the reboiler energy consumption and flash tank investment saved by using a flash tank, this example does not use a flash tank. Example 5 reduces the amount of cooling fluid introduced into the plate tower (II) 8.

[0106] Through the above steps, the present invention can utilize the hydraulic turbine to recover the energy in the easily vaporized high-pressure liquid, thereby realizing energy saving and consumption reduction of the chemical plant.

[0107] The remaining technical features in this embodiment can be flexibly selected by those skilled in the art according to actual conditions to meet different specific practical needs. However, it is obvious to those of ordinary skill in the art that it is not necessary to adopt these specific details to implement the present invention. In other examples, in order to avoid confusing the present invention, the well-known components, structures or parts are not specifically described, all of which are within the technical protection scope defined by the technical solution claimed for protection in the claims of the present invention. The expression of the textual language (including the drawings) of the specification of the present invention does not constitute any single restrictive interpretation of the claims.

[0108] Modifications and changes made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the scope of protection of the claims attached to the present invention. In the above description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to those of ordinary skill in the art that these specific details are not necessary to practice the present invention. In other examples, in order to avoid confusing the present invention, well-known technologies, such as specific construction details, operating conditions and other technical conditions, are not specifically described.

Claims

1. A method for recovering energy from easily vaporizable high-pressure liquid using a hydraulic turbine, characterized in that: The following steps are involved: S1. Heat exchange and cooling of the high-pressure fluid product mainly in liquid phase obtained through high-temperature and high-pressure chemical reaction; S2, passing the cooled high-pressure fluid obtained in step S1 through a hydraulic turbine to obtain a low-pressure fluid, and converting the pressure energy into mechanical energy; S3, passing the low-pressure fluid obtained in step S2 into a flash evaporation device for pressure-reducing flash evaporation to obtain a first gas phase and a first liquid phase; Or the low-pressure fluid does not separate the gas and liquid phases, and the low-pressure fluid is separated into n liquid phase material streams (n≥1); S4, exchanging heat with the first liquid phase obtained in step S3 to further obtain a second gas phase and a second liquid phase, and passing the first gas phase obtained in step S3, the second gas phase obtained in step S4, and the second liquid phase into a subsequent separation device for separation; Alternatively, the n liquid-phase material streams obtained in step S3 are respectively passed into n heat exchangers for heat exchange and temperature increase, and n groups of Nn-th gas phases and Nn-th liquid phases are correspondingly obtained, and then all the Nn-th gas phases and Nn-th liquid phases of the n groups are passed into subsequent separation equipment for separation; Alternatively, the first gas phase and the first liquid phase obtained in step S3 are directly introduced into a subsequent separation device for separation.

2. A method for recovering energy from easily vaporizable high-pressure liquid using a hydraulic turbine according to claim 1, characterized in that: In step S1, the high-pressure fluid product mainly composed of liquid phase has at least one component as liquid phase, and the liquid phase content is greater than 50wt%.

3. A method for recovering energy from easily vaporizable high-pressure liquid using a hydraulic turbine according to claim 1, characterized in that: In step S1, heat exchange and cooling is the energy exchange between the first hot fluid and the first cold fluid. The first hot fluid is the high-pressure fluid product mainly in liquid phase described in step S1, and the first cold fluid is a fluid with a lower temperature than the high-pressure fluid product in step S1.

4. A method for recovering energy from easily vaporizable high-pressure liquid using a hydraulic turbine according to claim 3, characterized in that: The first cold fluid is the first liquid phase of step S3 and / or other fluids having a lower temperature than the high-pressure fluid product in step S1.

5. The method for recovering energy from easily vaporizable high-pressure liquid using a hydraulic turbine according to claim 1, characterized in that: In step S2, the mechanical energy is used to generate electricity and / or as a power source for other rotating equipment.

6. A method for recovering energy from easily vaporizable high-pressure liquid using a hydraulic turbine according to claim 1, characterized in that: In step S3, the low-pressure fluid is rapidly evaporated and / or boiled by reducing the pressure to obtain a first gas phase and a first liquid phase, and the pressure drop value is greater than 0.

7. A method for recovering energy from easily vaporizable high-pressure liquid using a hydraulic turbine according to claim 1, characterized in that: In step S4, heat exchange and heating is the energy exchange between the second cold fluid and the first hot fluid, or the energy exchange between the second cold fluid and other fluids with a temperature higher than the first liquid phase in step S3. The first hot fluid is the high-pressure fluid product mainly in liquid phase described in step S1, and the second cold fluid is the first liquid phase in step S3.

8. The method for recovering energy from easily vaporizable high-pressure liquid using a hydraulic turbine according to claim 1, characterized in that: In step S4, the subsequent separation equipment is a plate and / or packed tower, or n-effect evaporation for achieving the same separation purpose, n≥2.

9. A method for recovering energy from easily vaporizable high-pressure liquid using a hydraulic turbine according to claim 1, characterized in that: In the step S2, the high-pressure fluid is always kept in a state of liquid phase>70wt% when the pressure is reduced by the hydraulic turbine.

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