LNG (Liquefied Natural Gas) cold energy power generation, seawater desalination and ice making coupling system

Abstract

The LNG cold energy power generation, seawater desalination and ice making coupling system comprises a seawater cooler, a seawater heater, a seawater flash evaporator, a first refrigerant vaporizer, an LNG vaporizer, a steam turbine generator, an expansion and compression all-in-one machine, a second refrigerant heat exchanger, a seawater ice maker, an inclined plate ice-water separator and a rotary drum ice crystal washer. A low-grade heat source of an LNG receiving station is used for heating seawater for flash evaporation desalination, water vapor is condensed to produce fresh water, and a first refrigerant is heated and evaporated; the expansion and compression all-in-one machine is driven by pressure energy generated after LNG is vaporized and expanded to conduct mechanical compression work on the first refrigerant, and the operation efficiency of the first refrigerant driving steam turbine generator is improved. The vaporized low-temperature natural gas is reheated through a second refrigerant, and the work efficiency of the natural gas driven expansion and compression all-in-one machine is improved; and the second refrigerant extracts the LNG cold energy for seawater ice making, and ice slurry can be used for marine product preservation, industrial cooling, cold storage air conditioners, low-temperature refrigeration houses and fresh water supply after being separated and purified.

Description

Technical Field

[0001] The present invention relates to the technical field of cold energy utilization of liquefied natural gas (LNG), and specifically to an LNG cold energy power generation, seawater desalination and ice making coupling system. Background Art

[0002] Natural gas has played an important role in aspects such as the transformation of the domestic energy structure, alleviating regional energy shortages, and treating atmospheric environmental pollution due to its many advantages such as high efficiency, high quality, and cleanness. In recent years, the consumption of liquefied natural gas (LNG) in China has shown a rapid growth trend. To meet the domestic LNG storage and transportation needs, a number of large LNG receiving stations have been built in coastal areas of China. LNG receiving stations usually use seawater as a heat source to heat and vaporize LNG to normal temperature, and then transport it to users through the natural gas pipeline network. A large amount of high-grade cold energy (about 827 kJ / kg, -162 °C) will be released during the vaporization of LNG. Theoretically, the cold energy of each ton of LNG at normal pressure is equivalent to 230 kWh of electric energy. However, at present, most of the cold energy released during the vaporization of LNG is directly discharged with seawater, which not only causes a great waste of energy, but also affects the surrounding marine environment. Therefore, it is urgent to develop LNG cold energy utilization technology.

[0003] The cold energy of LNG includes the latent heat of vaporization of LNG and the sensible heat of natural gas reheating from the storage temperature to the ambient temperature, and its temperature range is from -162 °C to 10 °C. Due to the characteristics of high energy density and wide temperature distribution range of LNG cold energy, any single utilization method cannot fully utilize the "quality" and "quantity" of LNG cold energy. To truly achieve the efficient utilization of LNG cold energy, this technology should develop towards the direction of integration and cascade in the future. Among various LNG cold energy utilization methods, the LNG cold energy power generation process is simple, the equipment investment is less, and the power generation is not restricted by market regionality, without product sales pressure, and the generated electricity can be supplied to surrounding users locally. It is one of the most potential technologies for commercial LNG cold energy utilization. However, compared with other power generation technologies, the conversion efficiency of LNG cold energy power generation generally does not exceed 30%, the LNG cold energy is not fully utilized, and the cold energy power generation cost remains high. Therefore, on the basis of improving the LNG cold energy power generation efficiency, combined with other local cold-using scenarios, it is necessary to develop the value of medium and high temperature cold energy of LNG, and through technology integration and system coupling, effectively improve the comprehensive utilization efficiency of LNG cold energy. Summary of the Invention

[0004] The object of the present invention is to overcome the deficiencies of the prior art and provide an LNG cold energy power generation, seawater desalination and ice making coupling system.

[0005] The technical solution of the present invention is outlined as follows:

[0006] An LNG cold energy power generation, seawater desalination and ice making coupling system, comprising a seawater cooler 1, a seawater heater 2, a seawater flash evaporator 3, a first refrigerant vaporizer 4, an LNG vaporizer 5, a steam turbine generator 6, an expansion and compression integrated machine 7, a second refrigerant heat exchanger 8, a seawater ice maker 9, an inclined plate ice water separator 10 and a rotary drum ice crystal washer 11; the expansion and compression integrated machine 7 includes an expander 7-2 and a compressor 7-1; a seawater spray head 3-1 is arranged at the upper part inside the seawater flash evaporator 3, and a vapor-liquid separator 3-2 is arranged at the top of the seawater flash evaporator 3; the steam turbine generator 6 includes a steam turbine 6-1 and a generator 6-2;

[0007] The seawater inlet pipe is respectively connected to the shell-side inlet at the bottom of the seawater cooler 1 and the shell-side inlet at the bottom of the seawater heater 2; the shell-side outlet at the top of the seawater cooler 1 is connected to the seawater outlet pipe and is connected to the tube-side inlet of the seawater ice maker 9 through a pipeline; the tube-side inlet of the seawater cooler 1 is connected to the outlet of the expander 7-2 through a pipeline, and the tube-side outlet of the seawater cooler 1 is connected to the natural gas pipeline network through a pipeline;

[0008] The hot water pipe connecting the LNG receiving station or the surrounding area is connected to the tube-side inlet of the seawater heater 2, and the hot water outlet pipe is connected to the tube-side outlet of the seawater heater 2; the shell-side outlet at the top of the seawater heater 2 is connected to the seawater spray head 3-1 of the seawater flash evaporator 3 through a pipeline; the top outlet of the seawater flash evaporator 3 is connected to the shell-side inlet of the first refrigerant vaporizer 4 through a pipeline; a flash-concentrated brine discharge pipe is arranged at the bottom of the seawater flash evaporator 3; the tube-side outlet of the first refrigerant vaporizer 4 is connected to the inlet of the compressor 7-1 through a pipeline;

[0009] The shell-side outlet at the bottom of the first refrigerant vaporizer 4 is connected to a steam-water separation tank 4-1 through a pipeline; the steam-water separation tank is provided with a fresh water outlet and a non-condensable gas outlet; the fresh water outlet is connected with a fresh water pipe; the non-condensable gas outlet is connected to a vacuum pump 3-3 through a pipeline and then connected to a non-condensable gas outlet pipe;

[0010] The outlet of the compressor 7-1 is connected to the inlet of the steam turbine 6-1 through a pipeline; the steam turbine 6-1 drives the generator 6-2 to generate electricity through a transmission shaft, converting mechanical energy into electrical energy;

[0011] The outlet of the steam turbine 6-1 is connected to the shell-side inlet at the top of the LNG vaporizer 5 through a pipeline; the shell-side outlet at the bottom of the LNG vaporizer 5 is connected to a first refrigerant storage tank 5-1 through a pipeline and then connected to the tube-side inlet of the first refrigerant vaporizer 4;

[0012] The tube-side outlet of the LNG vaporizer 5 is connected to the tube-side inlet of the second refrigerant heat exchanger 8 through a pipeline; the tube-side outlet of the second refrigerant heat exchanger 8 is connected to the inlet of the expander 7-2 through a pipeline;

[0013] The LNG feed pipe is connected to the tube-side inlet of the LNG vaporizer 5;

[0014] The shell-side outlet at the top of the second refrigerant heat exchanger 8 is connected to the shell-side inlet at the top of the seawater ice maker 9 through a pipeline; the shell-side outlet at the bottom of the seawater ice maker 9 is connected to the second refrigerant storage tank 9-1 through a pipeline and then to the shell-side inlet at the bottom of the second refrigerant heat exchanger 8;

[0015] The tube-side outlet of the seawater ice maker 9 is connected to the inlet of the inclined plate ice-water separator 10 through a pipeline; an inclined orifice plate 10-1 is arranged in the middle of the ice-water separator 10; a frozen brine discharge pipe is arranged at the bottom of the ice-water separator 10;

[0016] The outlet of the inclined plate ice-water separator 10 is connected to the inlet of the rotary drum ice crystal washer 11 through a pipeline;

[0017] A washing water spray head 11-1 is arranged at the top of the rotary drum ice crystal washer 11; a conductivity meter 11-2 is arranged at the bottom of the rotary drum ice crystal washer 11; a make-up fresh water pipe is connected to the washing water spray head 11-1; the water outlet pipe arranged at the bottom of the rotary drum ice crystal washer 11 is divided into two branches, one is a washing water discharge pipe, and the other is connected to the washing water spray head 11-1; the rotary drum ice crystal washer 11 is connected to an ice crystal output pipe.

[0018] Preferably, the vacuum pump 3-3 is a liquid ring vacuum pump, a jet vacuum pump or a Roots vacuum pump.

[0019] The seawater ice maker 9 is a fluidized bed type ice maker, a mechanical scraping type ice maker or a plate type ice maker.

[0020] The advantages and positive effects of the present invention are:

[0021] (1) The present invention organically integrates LNG cold energy power generation, seawater flash evaporation desalination and seawater freezing ice making. While mainly improving the power generation efficiency of the system, combined with other local cold-using scenarios, it develops and utilizes the value of medium and high temperature cold energy in LNG, increasing the by-product income of fresh water and ice. According to the principle of "temperature equivalence and cascade utilization", the high-efficiency and reasonable utilization of LNG cold energy is realized, and the industrial chain of LNG cold energy utilization is expanded.

[0022] (2) The present invention integrates the LNG direct expansion type and the intermediate medium Rankine cycle type power generation technologies by using an expansion-compression integrated machine. The expansion-compression integrated machine uses the pressure energy after the vaporization and expansion of LNG to perform mechanical compression work on the first refrigerant in the Rankine cycle process, thereby fully utilizing the temperature and pressure Effectively improve the power generation efficiency of LNG cold energy. Compared with the power generation mode of single LNG cold energy, this coupling method not only improves the comprehensive utilization rate of LNG cold energy, but also can perform secondary heating and pressurization on the vaporized first refrigerant, improving the operating conditions of the steam turbine generator.

[0023] (3) The present invention uses low-grade heat sources in LNG receiving stations or their surroundings to heat seawater, and realizes seawater desalination through spray flashing. Then, the steam is used for heat exchange with the first refrigerant through phase change, enabling the system to obtain fresh water benefits while increasing the evaporation temperature of the first refrigerant and the thermodynamic cycle efficiency. In addition, this method also overcomes the problem that the traditional LNG vaporizer cannot operate or has insufficient vaporization capacity due to the too low seawater temperature in winter in northern regions, ensuring the safe and stable operation of the LNG vaporizer.

[0024] (4) The present invention reheats the vaporized low-temperature natural gas using the second refrigerant, which can improve the work capacity of natural gas in the expander. At the same time, the second refrigerant is used to further extract the cold energy of natural gas to realize seawater ice making. The second refrigerant transfers cold energy using its sensible heat, and the heat transfer temperature difference with seawater can be precisely controlled by adjusting the circulation flow rate of the second refrigerant, thereby controlling the growth rate of ice crystals. Combined with the dynamic seawater ice making technology, continuous production of seawater ice slurry can be achieved. The obtained pure ice crystals can be widely used in many fields such as seafood preservation, industrial cooling, concrete cooling, cold storage air conditioning, biomedicine, low-temperature cold storage, and fresh water replenishment, realizing the indirect utilization of LNG cold energy and facilitating the industrial development of LNG cold energy. Brief Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the process flow of the system of the present invention. Detailed Embodiments

[0026] The present invention will be further described below in conjunction with specific embodiments.

[0027] Embodiment 1

[0028] A coupled system for LNG cold energy power generation, seawater desalination and ice making (see Figure 1 ), including a seawater cooler 1, a seawater heater 2, a seawater flash evaporator 3, a first refrigerant vaporizer 4, an LNG vaporizer 5, a steam turbine generator 6, an expansion and compression integrated machine 7, a second refrigerant heat exchanger 8, a seawater ice maker 9, an inclined plate ice-water separator 10 and a rotary drum ice crystal washer 11; the expansion and compression integrated machine 7 includes an expander 7-2 and a compressor 7-1; a seawater spray head 3-1 is arranged in the upper part inside the seawater flash evaporator 3, and a vapor-liquid separator 3-2 is arranged at the top of the seawater flash evaporator 3; the steam turbine generator 6 includes a steam turbine 6-1 and a generator 6-2;

[0029] The seawater inlet pipe is respectively connected to the shell-side inlet at the bottom of the seawater cooler 1 and the shell-side inlet at the bottom of the seawater heater 2; the shell-side outlet at the top of the seawater cooler 1 is connected to the seawater outlet pipe and is connected to the tube-side inlet of the seawater ice maker 9 through a pipeline; the tube-side inlet of the seawater cooler 1 is connected to the outlet of the expander 7-2 through a pipeline, and the tube-side outlet of the seawater cooler 1 is connected to the natural gas pipeline network through a pipeline;

[0030] Connect the hot water pipe connecting the LNG receiving station or the surrounding area to the tube-side inlet of the seawater heater 2, and the hot water outlet pipe is connected to the tube-side outlet of the seawater heater 2; the shell-side outlet at the top of the seawater heater 2 is connected to the seawater nozzle 3-1 of the seawater flash evaporator 3 through a pipeline; the top outlet of the seawater flash evaporator 3 is connected to the shell-side inlet of the first refrigerant vaporizer 4 through a pipeline; a flash-concentrated brine discharge pipe is provided at the bottom of the seawater flash evaporator 3; the tube-side outlet of the first refrigerant vaporizer 4 is connected to the inlet of the compressor 7-1 through a pipeline;

[0031] The shell-side outlet at the bottom of the first refrigerant vaporizer 4 is connected to the steam-water separation tank 4-1 through a pipeline; the steam-water separation tank is provided with a fresh water outlet and a non-condensable gas outlet; the fresh water outlet is connected with a fresh water pipe; the non-condensable gas outlet is connected to the liquid ring vacuum pump (a liquid ring vacuum pump is selected in this embodiment, and a jet vacuum pump or a roots vacuum pump can also be selected) 3-3 through a pipeline and then connected to the non-condensable gas outlet pipe;

[0032] The outlet of the compressor 7-1 is connected to the inlet of the steam turbine 6-1 through a pipeline; the steam turbine 6-1 drives the generator 6-2 to generate electricity through a transmission shaft, converting mechanical energy into electrical energy;

[0033] The outlet of the steam turbine 6-1 is connected to the shell-side inlet at the top of the LNG vaporizer 5 through a pipeline; the shell-side outlet at the bottom of the LNG vaporizer 5 is connected to the first refrigerant storage tank 5-1 through a pipeline and then connected to the tube-side inlet of the first refrigerant vaporizer 4;

[0034] The tube-side outlet of the LNG vaporizer 5 is connected to the tube-side inlet of the second refrigerant heat exchanger 8 through a pipeline; the tube-side outlet of the second refrigerant heat exchanger 8 is connected to the inlet of the expander 7-2 through a pipeline;

[0035] The LNG feed pipe is connected to the tube-side inlet of the LNG vaporizer 5;

[0036] The shell-side outlet at the top of the second refrigerant heat exchanger 8 is connected to the shell-side inlet at the top of the seawater ice maker (a fluidized bed ice maker is selected in this embodiment, and a mechanical scraping ice maker or a plate type ice maker can also be selected) 9 through a pipeline; the shell-side outlet at the bottom of the seawater ice maker 9 is connected to the second refrigerant storage tank 9-1 through a pipeline and then connected to the shell-side inlet at the bottom of the second refrigerant heat exchanger 8;

[0037] The tube side outlet of the seawater ice maker 9 is connected to the inlet of the inclined plate ice-water separator 10 through a pipeline; an inclined orifice plate 10-1 is arranged in the middle of the ice-water separator 10; a discharged pipe for concentrated brine after freezing is arranged at the bottom of the ice-water separator 10;

[0038] The outlet of the inclined plate ice-water separator 10 is connected to the inlet of the rotary drum ice crystal washer 11 through a pipeline;

[0039] A washing water spray head 11-1 is arranged at the top of the rotary drum ice crystal washer 11; a conductivity meter 11-2 is arranged at the bottom of the rotary drum ice crystal washer 11; a fresh water supply pipe is connected to the washing water spray head 11-1; the water outlet pipe arranged at the bottom of the rotary drum ice crystal washer 11 is branched into two, one is a washing water discharge pipe, and the other is connected to the washing water spray head 11-1; the rotary drum ice crystal washer 11 is connected to an ice crystal output pipe.

[0040] Embodiment 2

[0041] Use of a coupled system for LNG cold energy power generation, seawater desalination and ice making:

[0042] A coupled system for LNG cold energy power generation, seawater desalination and ice making (Embodiment 1) includes a seawater cooler 1, a seawater heater 2, a seawater flash evaporator 3, a first refrigerant vaporizer 4, an LNG vaporizer 5, a steam turbine generator 6, an expansion and compression integrated machine 7, a second refrigerant heat exchanger 8, a seawater ice maker 9, an inclined plate ice-water separator 10 and a rotary drum ice crystal washer 11; the expansion and compression integrated machine 7 includes an expander 7-2 and a compressor 7-1; a seawater spray head 3-1 is arranged in the upper part inside the seawater flash evaporator 3, and a vapor-liquid separator 3-2 is arranged at the top of the seawater flash evaporator 3; the steam turbine generator 6 includes a steam turbine 6-1 and a generator 6-2;

[0043] Raw seawater (flow rate 769.8 t / h, temperature 25 °C, pressure 0.15 MPa) enters the shell side inlet at the bottom of the seawater cooler 1 and the shell side inlet at the bottom of the seawater heater 2 along the seawater inlet pipe respectively: among them, seawater with a flow rate of 192.9 t / h enters the shell side of the seawater cooler 1, and seawater with a flow rate of 576.9 t / h enters the shell side of the seawater heater 2; the shell side outlet at the top of the seawater cooler 1 is connected to the seawater outlet pipe: among them, 83.7 t / h of cooled seawater is discharged from the system, and 109.2 t / h of cooled seawater enters the tube side inlet of the seawater ice maker 9 as frozen raw seawater through a pipeline; the tube side inlet of the seawater cooler 1 is connected to the outlet of the expander 7-2 through a pipeline, and the tube side outlet of the seawater cooler 1 is connected to the natural gas pipeline network;

[0044] In the seawater cooler 1, gaseous NG (temperature -10°C, pressure 10 MPa.a) enters the tube side of the seawater cooler 1. NG exchanges heat with seawater. After the temperature of NG rises from -10°C to 1°C, it enters the natural gas transmission pipeline network. The temperature of the cooled seawater drops from 25°C to 20°C. The outer diameter of the heat transfer tubes of the seawater cooler 1 is 15 mm, the wall thickness is 1.5 mm, and the material is stainless steel SS316L.

[0045] Hot water (temperature 80°C, pressure 0.15 MPa, flow rate 959 t / h) from the LNG receiving terminal or its vicinity enters the inlet of the tube side of the seawater heater 2 along the hot water pipeline. The hot water outlet pipe is connected to the outlet of the tube side of the seawater heater 2. Seawater exchanges heat with the hot water. The temperature of the hot water drops from 80°C to 40°C, and the temperature of the seawater rises from 25°C to 70°C. Inside the seawater heater 2, the outer diameter of the heat transfer tubes is 25 mm, the wall thickness is 1 mm, and the material is stainless steel SS316L.

[0046] The shell side outlet at the top of the seawater heater 2 is connected to the seawater spray head 3-1 of the seawater flash evaporator 3 through a pipeline. The top outlet of the seawater flash evaporator 3 is connected to the inlet of the shell side of the first refrigerant vaporizer 4 through a pipeline. A flash-concentrated brine discharge pipe is provided at the bottom of the seawater flash evaporator 3. The outlet of the tube side of the first refrigerant vaporizer 4 is connected to the inlet of the compressor 7-1 through a pipeline.

[0047] In the seawater flash evaporator 3, the vapor-liquid separator 3-2 is in the form of wire mesh, made of SS316L, with a thickness of 50 mm and a porosity of 50%. The seawater spray head 3-1 is in the form of a solid cone, made of SS316L, with a spray pressure of 0.15 MPa and a spray angle of 120°. The heated seawater is sprayed through the seawater spray head 3-1 to form liquid droplets with an average particle size of 0.5 mm. The liquid droplets flash in the cavity of the seawater flash evaporator 3 with a vacuum pressure of 9.6 kPa.a to generate water vapor (temperature 45°C, flow rate 22.3 t / h). The water vapor removes the entrained seawater droplets after passing through the vapor-liquid separator 3-2. The flash-concentrated brine (temperature 45°C, flow rate 554.6 t / h) is discharged from the system after the pressure rises to 0.15 MPa.

[0048] Select refrigerant R410A as the first refrigerant; in the first refrigerant vaporizer 4, R410A (flow rate 177.6 t / h) enters the tube side of the first refrigerant vaporizer 4, and the steam after gas-liquid separation enters the shell side of the first refrigerant vaporizer 4. The steam exchanges heat with R410A, and the steam condenses to release heat and becomes liquid fresh water; the shell side outlet at the bottom of the first refrigerant vaporizer 4 is connected to the steam-water separation tank 4-1 through a pipeline; the steam-water separation tank is provided with a fresh water outlet and a non-condensable gas outlet; the generated fresh water (flow rate 22.3 t / h, temperature 30 °C) is transported to users along the fresh water pipeline after the pressure is increased to 0.15 MPa; after the non-condensable gas outlet is connected to the vacuum pump 3-3 through a pipeline and then to the non-condensable gas outlet pipe; the non-condensable gas released by seawater flashing is discharged from the system through the pipeline under the suction of the vacuum pump 3-3;

[0049] The outer diameter of the heat transfer tubes in the first refrigerant vaporizer 4 is 15 mm, the wall thickness is 1 mm, and the material is stainless steel SS304; the steam-water separation tank 4-1 is a cylinder with a volume of 5 m 3 , the material is SS304, and the pressure in the cavity is 9.6 kPa.a; the vacuum pump (liquid ring vacuum pump) 3-3 maintains the pressure in the steam-water separation tank 4-1, the first refrigerant vaporizer 4 and the seawater flash evaporator 3 at 9.6 kPa.a;

[0050] In the first refrigerant vaporizer 4, the liquid R410A at a temperature of -7 °C is heated and vaporized into gaseous R410A (temperature 25 °C, pressure 1.6 MPa.a) and enters the compressor 7-1 along the pipeline; the compressor 7-1 performs compression work on R410A, and the temperature of R410A rises from 25 °C to 33 °C, and the pressure rises from 1.6 MPa.a to 2.0 MPa.a; the outlet of the compressor 7-1 is connected to the inlet of the steam turbine 6-1 through a pipeline; the steam turbine 6-1 drives the generator 6-2 to generate electricity through a transmission shaft, converting mechanical energy into electrical energy, and the power generation power is 4.5 MW;

[0051] The outlet of the steam turbine 6-1 is connected to the inlet of the shell side at the top of the LNG vaporizer 5 through a pipeline; in the LNG vaporizer 5, the gaseous R410A is condensed into liquid R410A (temperature -7 °C, pressure 0.6 MPa.a) after exchanging heat with LNG; the LNG vaporizer 5 is an intermediate fluid type vaporizer, the outer diameter of the heat transfer tubes is 15 mm, the wall thickness is 1.5 mm, and the material is stainless steel SS304; the shell side outlet at the bottom of the LNG vaporizer 5 is connected to the first refrigerant storage tank 5-1 through a pipeline; the first refrigerant storage tank 5-1 is a cylinder with a volume of 30 m 3 , the material is SS304, and the pressure in the cavity is 0.6 MPa.a; after the pressure of the liquid R410A is increased to 1.6 MPa.a, it enters the tube side inlet of the first refrigerant vaporizer 4;

[0052] The tube-side outlet of the LNG vaporizer 5 is connected to the tube-side inlet of the second refrigerant heat exchanger 8 through a pipeline; the tube-side outlet of the second refrigerant heat exchanger 8 is connected to the inlet of the expander 7-2 through a pipeline; the LNG feed pipe is connected to the tube-side inlet of the LNG vaporizer 5; in the LNG vaporizer 5, LNG (temperature -150°C, pressure 10 MPa.a, flow rate 100 t / h) exchanges heat with R410A, and the LNG is heated and vaporized and expanded into NG (temperature -50°C, pressure 10.5 MPa.a);

[0053] The methanol solution with a methanol mass concentration of 50% is used as the second refrigerant; the low-temperature NG enters the tube side of the second refrigerant heat exchanger 8 along the pipeline. After the NG exchanges heat with the methanol solution, the temperature rises from -50°C to -10°C, and the pressure rises from 10.5 MPa.a to 10.7 MPa.a; the NG after pressure increase enters the expander 7-2 to release internal energy and do work, and the pressure of the NG drops to 10 MPa.a; the expander 7-2 drives the compressor 7-1 to do work on R410A through a transmission shaft; the expanded NG enters the seawater cooler 1 along the pipeline. After the NG exchanges heat with the cooling seawater, the temperature rises to 1°C, and finally it is transported to users through the natural gas pipeline network;

[0054] The methanol solution (pressure 0.15 MPa, flow rate 293.2 t / h) enters the shell-side inlet at the top of the seawater ice maker 9 through a pipeline from the shell-side outlet at the top of the second refrigerant heat exchanger 8; in the second refrigerant heat exchanger 8, the temperature of the methanol solution drops from 15°C to -5°C; in the seawater ice maker (fluidized bed ice maker) 9, the temperature of the methanol solution rises from -5°C to 15°C; the methanol solution enters the second refrigerant storage tank 9-1 through a pipeline from the shell-side outlet at the bottom of the seawater ice maker 9, and after the pressure rises to 0.15 MPa, it enters the shell-side inlet at the bottom of the second refrigerant heat exchanger 8 along the pipeline; the outer diameter of the heat transfer tube in the second refrigerant heat exchanger 8 is 25 mm, the wall thickness is 1.5 mm, and the material is stainless steel SS316L; the second refrigerant storage tank 9-1 is a cylinder with a volume of 50 m 3 and the material is SS304;

[0055] Part of the cooling seawater (flow rate 109.2 t / h, temperature 20°C, pressure 0.13 MPa) enters the tube side of the seawater ice maker 9 as the frozen raw material seawater; scraping particles are filled in the heat transfer tubes of the seawater ice maker 9, the bed void fraction is 60%, the outer diameter of the heat transfer tube is 50 mm, the wall thickness is 2.5 mm, and the material is stainless steel SS316L; the scraping particles are cylinders with a diameter of 4 mm and a length of 4 mm, and the material is stainless steel SS316L; after the frozen raw material seawater exchanges heat with the methanol solution, the temperature of the frozen raw material seawater drops from 20°C to the freezing point (-1.9°C) and becomes seawater ice slurry with an ice crystal mass concentration of 30%;

[0056] Seawater ice slurry (flow rate 109.2 t / h) enters the inlet of the inclined plate ice-water separator 10 through a pipeline from the tube-side outlet of the seawater ice maker 9; the inclined plate ice-water separator 10 is a cuboid with a length of 5 m, a width of 3 m, and a height of 3 m, and the material is SS316L; a 15° inclined orifice plate 10-1 is arranged in the middle of the ice-water separator 10; the thickness of the orifice plate 10-1 is 4 mm and the aperture is 1.5 mm; during the process of the seawater ice slurry sliding downward along the orifice plate 10-1 under the action of gravity, the concentrated brine converges at the bottom of the inclined plate ice-water separator 10 through the orifice plate 10-1, and the concentrated brine (flow rate 76.5 t / h) is boosted to 0.15 MPa and then discharged from the system through the concentrated brine discharge pipe; the separated ice crystals (flow rate 32.7 t / h) enter the inlet of the rotary drum ice crystal washer 11 through a pipeline from the outlet of the inclined plate ice-water separator 10 under the action of gravity;

[0057] A washing water spray head 11-1 is arranged at the top of the rotary drum ice crystal washer 11; a conductivity meter 11-2 is arranged at the bottom of the rotary drum ice crystal washer 11; the makeup fresh water pipe is connected to the washing water spray head 11-1; the water outlet pipe arranged at the bottom of the rotary drum ice crystal washer 11 is divided into two branches, one is the washing water discharge pipe, and the other is connected to the washing water spray head 11-1; the rotary drum ice crystal washer 11 is connected to the ice crystal output pipe;

[0058] The rotary drum ice crystal washer 11 is a cylinder with an outer diameter of 3 m and a length of 5 m, and the material is SS316L; the rotary drum at the center of the rotary drum ice crystal washer 11 maintains a rotation speed of 40 r / min; when the ice crystals rotate with the rotary drum to the position of the washing water spray head 11-1, 15 t / h of washing water is sprayed onto the outer wall of the rotary drum through the washing water spray head 11-1, and the washing water contacts the ice crystals through the holes in the drum wall; the washing water spray head 11-1 is of a solid cone type, the material is SS316L, the spraying pressure is 0.2 MPa, and the spraying angle is 120°;

[0059] The washing water takes out the salt entrained inside the ice crystals and is discharged to the outside of the rotary drum under the action of centrifugal force, and converges at the bottom of the rotary drum ice crystal washer 11; the washed ice crystals are sent to the user along the pipeline under the action of gravity; the pressure of the washing water rises to 0.2 MPa and then re-enters the washing water spray head 11-1 to realize the recycling of the washing water; the conductivity meter 11-2 measures the salinity of the washing water online, and when the conductivity of the washing water exceeds 8000 μs / cm, the washing water with high salt content is discharged from the system, and at the same time, fresh water is supplemented as the washing water.

Claims

1. An LNG cold energy power generation, seawater desalination and ice making coupling system, comprising a seawater cooler (1), a seawater heater (2), a seawater flash evaporator (3), a first refrigerant vaporizer (4), an LNG vaporizer (5), a steam turbine generator (6), an expansion and compression integrated machine (7), a second refrigerant heat exchanger (8), a seawater ice maker (9), an inclined plate ice-water separator (10) and a rotary drum ice crystal washer (11); The expansion and compression integrated machine (7) comprises an expander (7-2) and a compressor (7-1); a seawater spray head (3-1) is arranged at the upper part inside the seawater flash evaporator (3), and a vapor-liquid separator (3-2) is arranged at the top of the seawater flash evaporator (3); the steam turbine generator (6) comprises a steam turbine (6-1) and a generator (6-2), and is characterized in that: The seawater inlet pipe is respectively connected with the shell-side inlet at the bottom of the seawater cooler (1) and the shell-side inlet at the bottom of the seawater heater (2); the shell-side outlet at the top of the seawater cooler (1) is connected with the seawater outlet pipe and is connected with the tube-side inlet of the seawater ice maker (9) through a pipeline; the tube-side inlet of the seawater cooler (1) is connected with the outlet of the expander (7-2) through a pipeline, and the tube-side outlet of the seawater cooler (1) is connected with the natural gas pipeline network through a pipeline; The hot water pipe connecting the LNG receiving station or the periphery is connected with the tube-side inlet of the seawater heater (2), and the hot water outlet pipe is connected with the tube-side outlet of the seawater heater (2); the shell-side outlet at the top of the seawater heater (2) is connected with the seawater spray head (3-1) of the seawater flash evaporator (3) through a pipeline; the top outlet of the seawater flash evaporator (3) is connected with the shell-side inlet of the first refrigerant vaporizer (4) through a pipeline; a flash-concentrated brine discharge pipe is arranged at the bottom of the seawater flash evaporator (3); the tube-side outlet of the first refrigerant vaporizer (4) is connected with the inlet of the compressor (7-1) through a pipeline; The shell-side outlet at the bottom of the first refrigerant vaporizer (4) is connected with a steam-water separation tank (4-1) through a pipeline; the steam-water separation tank is provided with a fresh water outlet and a non-condensable gas outlet; the fresh water outlet is connected with a fresh water pipe; the non-condensable gas outlet is connected with a vacuum pump (3-3) through a pipeline and then connected with a non-condensable gas outlet pipe; The outlet of the compressor (7-1) is connected with the inlet of the steam turbine (6-1) through a pipeline; the steam turbine (6-1) drives the generator (6-2) to generate electricity through a transmission shaft, converting mechanical energy into electrical energy; The outlet of the steam turbine (6-1) is connected with the shell-side inlet at the top of the LNG vaporizer (5) through a pipeline; the shell-side outlet at the bottom of the LNG vaporizer (5) is connected with a first refrigerant storage tank (5-1) through a pipeline and then connected with the tube-side inlet of the first refrigerant vaporizer (4); The tube-side outlet of the LNG vaporizer (5) is connected with the tube-side inlet of the second refrigerant heat exchanger (8) through a pipeline; the tube-side outlet of the second refrigerant heat exchanger (8) is connected with the inlet of the expander (7-2) through a pipeline; The LNG feed pipe is connected with the tube-side inlet of the LNG vaporizer (5); The shell-side outlet at the top of the second refrigerant heat exchanger (8) is connected to the shell-side inlet at the top of the seawater ice maker (9) through a pipeline; the shell-side outlet at the bottom of the seawater ice maker (9) is connected to the second refrigerant storage tank (9-1) through a pipeline and then connected to the shell-side inlet at the bottom of the second refrigerant heat exchanger (8); The tube-side outlet of the seawater ice maker (9) is connected to the inlet of the inclined plate ice-water separator (10) through a pipeline; an inclined orifice plate (10-1) is arranged in the middle of the ice-water separator (10); a discharge pipe for the concentrated brine after freezing is arranged at the bottom of the ice-water separator (10); The outlet of the inclined plate ice-water separator (10) is connected to the inlet of the rotary drum ice crystal washer (11) through a pipeline; A washing water spray head (11-1) is arranged at the top of the rotary drum ice crystal washer (11); a conductivity meter (11-2) is arranged at the bottom of the rotary drum ice crystal washer (11); a make-up fresh water pipe is connected to the washing water spray head (11-1); the water outlet pipe arranged at the bottom of the rotary drum ice crystal washer (11) is divided into two branches, one is a washing water discharge pipe, and the other is connected to the washing water spray head (11-1); the rotary drum ice crystal washer (11) is connected to an ice crystal output pipe.

2. The system according to claim 1, wherein The vacuum pump (3-3) is a liquid ring vacuum pump, a jet vacuum pump or a Roots vacuum pump.

3. The system according to claim 1, wherein The seawater ice maker (9) is a fluidized bed type ice maker, a mechanical scraping type ice maker or a plate type ice maker.

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