Design method of low-energy-consumption MVR waste liquid treatment evaporator structure

Abstract

The invention discloses a design method of a low-energy-consumption MVR waste liquid treatment evaporator structure, and relates to the technical field of solvent distillation recovery, and the design method comprises the following steps: matching and designing a heat exchange structure of an MVR system, and establishing an initial model of the heat exchange structure; taking the sum of the equipment investment cost and the operation cost as the total cost of the heat exchange structure, and outputting the total cost as a target function of the heat exchange structure model; utilizing a genetic algorithm to realize a structure optimization process of the initial model of the heat exchange structure; establishing a design model of a distillation host, and calculating to obtain structural parameters of the distillation host matched with the MVR system based on the process parameters in the heat exchange structure optimization model; a roots type compressor is adopted to compress steam generated by the distillation main machine; the discharged secondary steam potential is recycled by adopting a mechanical steam recompression technology; and summarizing and integrating the MVR waste liquid treatment evaporator structure. By forming a closed-loop circulation system of heat energy, energy consumption is greatly reduced, and efficient utilization of heat energy is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of solvent distillation recovery, and in particular to a design method for a low-energy consumption MVR waste liquid treatment evaporator structure. Background Art

[0002] MVR is the abbreviation of mechanical vapor recompression. MVR is an energy-saving technology that reuses the energy of the secondary steam generated by itself, thereby reducing the demand for external energy. As early as the 1960s, this technology has been used in the fields of chemical industry, food, papermaking, medicine, seawater desalination and sewage treatment. The working process of the evaporator is to compress the low-temperature steam through the compressor, increase the temperature and pressure, increase the thermal enthalpy, and then enter the heat exchanger for condensation to fully utilize the latent heat of the steam. Except for starting the car, no steam is required during the entire evaporation process.

[0003] A large amount of high-concentration salt-containing wastewater is generated in the production processes of printing and dyeing, chemicals, papermaking, medicine and pesticides. Some of the inorganic salts contained in the wastewater are also worth recycling, and direct discharge will lead to water environmental pollution and waste of resources. Conventional multi-effect evaporation can treat and recycle this type of wastewater, but there are problems such as high energy consumption, many supporting equipment, and high operating costs. Therefore, it is of certain practical significance to study a waste liquid treatment method with low energy consumption, low operating costs and compact structure. Summary of the invention

[0004] In order to solve the above technical problems, a design method for a low-energy consumption MVR waste liquid treatment evaporator structure is provided. This technical solution solves the problems raised in the above background technology.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A design method for a low energy consumption MVR waste liquid treatment evaporator structure, comprising:

[0007] Using the heat transfer effectiveness-heat transfer unit number theory of the heat exchanger, calculate the relevant structural parameters of the heat exchange structure, match and design the heat exchange structure of the MVR system, and establish the initial model of the heat exchange structure;

[0008] The sum of equipment investment cost and operation cost is taken as the total cost of the heat exchange structure, and output as the objective function of the heat exchange structure model;

[0009] Based on the objective function of the heat exchange structure model, the genetic algorithm is used to realize the structural optimization process of the initial model of the heat exchange structure, and the heat exchange structure optimization model is obtained;

[0010] According to the separator design principle, the design model of the distillation host is established, and based on the process parameters in the heat exchange structure optimization model, the structural parameters of the distillation host that matches the MVR system are calculated to construct the distillation host structure model;

[0011] A Roots compressor is used to compress the steam generated by the distillation main engine, and the structure of the Roots compressor is analyzed;

[0012] Mechanical vapor recompression technology is used to recycle the potential of discharged secondary steam and use it as heating steam to provide heat source for the MVR system;

[0013] Summarize and integrate the MVR waste liquid treatment evaporator structure and draw the overall process integration diagram of the MVR system.

[0014] Preferably, the heat exchanger heat transfer effectiveness-heat transfer unit number theory is used to calculate the structural parameters related to the heat exchange structure, match and design the heat exchange structure of the MVR system, and establish the initial model of the heat exchange structure, which specifically includes:

[0015] The steam in the heat exchange structure consists of two parts: steam cooling and condensation. The heat exchange structure is set as a cooling sensible heat section and a condensation latent heat section;

[0016] Based on the heat transfer effectiveness-heat transfer unit number theory, the heat transfer effectiveness of the two heat exchange structures is calculated respectively;

[0017] Calculate the number of heat transfer units in the heat exchange structure;

[0018] Obtaining an empirical value range of the total heat transfer coefficient, and presetting the total heat transfer coefficient of the heat exchange structure based on the empirical value range;

[0019] Use the heat exchange area formula to calculate the initial heat exchange area;

[0020] Preset the inner diameter of the pipe of the heat exchange structure;

[0021] Determine the flow area of ​​the pipe;

[0022] Calculate the number of heat exchange tubes and the length of each heat exchange tube respectively;

[0023] The heat transfer effectiveness-heat transfer unit number theory is:

[0024]

[0025] Where ε is the heat transfer efficiency, t si is the hot end inlet temperature, t ti is the cold end inlet temperature, △t s is the temperature difference between the hot end inlet and outlet, △t t is the temperature difference between the cold end inlet and outlet;

[0026] The number of heat transfer units is:

[0027]

[0028] Where, N is the number of heat transfer units, and f is the relationship function between heat transfer effectiveness and the number of heat transfer units in the preset non-mixing countercurrent heat exchange structure.

[0029] The heat exchange area formula is:

[0030]

[0031] Where k is the overall heat transfer coefficient, A is the initial heat transfer area, and W min is the minimum heat capacity of the waste liquid; the flow area of ​​the tube pass is:

[0032]

[0033] In the formula, S is the tube flow area, F is the steam flow rate, v is the tube flow velocity, and ρ is the steam density; the number of heat exchange tubes is:

[0034]

[0035] In the formula, n is the number of heat exchange tubes, and r is the preset inner diameter of the heat exchange tube;

[0036] The length of each heat exchange tube is:

[0037]

[0038] Where L is the length of each heat exchange tube.

[0039] Preferably, the sum of the equipment investment cost and the operating cost is used as the total cost of the heat exchange structure, and output as the objective function of the heat exchange structure model specifically includes:

[0040] The total cost of the heat exchange structure includes equipment investment cost and operation cost;

[0041] The equipment investment cost is the investment cost of the heat exchange area;

[0042] Operation cost is the energy cost consumed by the pump to overcome the pressure drop;

[0043] Obtain the heat exchange area parameters of the material selected for the heat exchange structure, that is, the heat exchange area parameters of stainless steel;

[0044] Based on the heat exchange area parameters of stainless steel, the investment cost of the equipment is calculated using the investment cost formula;

[0045] Calculate operating costs using energy cost formula;

[0046] The sum of the output equipment investment cost and the operating cost is the objective function of the heat exchange structure model;

[0047] The investment cost formula is:

[0048]

[0049] In the formula, C 1 is the equipment investment cost, a 1 、a 2 、a 3 are the first, second and third heat transfer area parameters of stainless steel respectively;

[0050] The energy cost formula is:

[0051]

[0052] In the formula, C 2 is the operating cost, η is the efficiency of the pump, △P t , △P s are the pressure losses on the tube side and shell side, respectively.

[0053] Preferably, the objective function based on the heat exchange structure model uses a genetic algorithm to implement the structural optimization process of the initial model of the heat exchange structure, and the heat exchange structure optimization model is obtained, which specifically includes:

[0054] S101: randomly generate a heat exchange structure model and a heat exchange structure initial model summary as an initial population;

[0055] S102: Evaluate all individuals in the population according to the objective function of the heat exchange structure model to obtain the fitness value of each individual;

[0056] S103: Select excellent individuals as parents according to fitness values;

[0057] S104: performing a non-equivalent exchange operation between the parent individuals, exchanging the position and content of the heat exchange structure model parameters, and generating new offspring individuals;

[0058] S105: Perform random mutation operation on offspring individuals and introduce new parameter values ​​as genetic genes;

[0059] S106: Replace the non-excellent individuals in the population with the newly generated offspring individuals;

[0060] S107: Determine whether the preset maximum number of iterations has been reached. If so, terminate the iteration and output the current population as a heat exchange structure optimization model. If not, return to step S102.

[0061] Preferably, the design model of the distillation host is established based on the separator design principle, and the structural parameters of the distillation host that match the MVR system are calculated based on the process parameters in the heat exchange structure optimization model. The construction of the distillation host structural model specifically includes:

[0062] The main distillation unit consists of a cylinder, a feed pipe, a heat exchange pipe, a concentrate outlet, a defoamer and a steam outlet;

[0063] Obtain distillation parameters, waste liquid density and vapor density;

[0064] Use the critical speed formula to calculate the maximum speed at which steam is allowed to pass;

[0065] Calculate the diameter of the distillation main cylinder based on the maximum velocity at which steam is allowed to pass;

[0066] The height of the distillation main engine cylinder is set to be twice the diameter of the distillation main engine cylinder;

[0067] Set the diameter of each interface to the inner diameter of the heat exchange tube;

[0068] Use wire mesh demister to eliminate droplets entrained in steam;

[0069] The critical speed formula is:

[0070]

[0071] In the formula, v max is the maximum velocity of steam allowed to pass, m is the distillation parameter, ρ 1 , 2 are the waste liquid density and steam density respectively;

[0072] The diameter of the distillation main engine cylinder is:

[0073]

[0074] Where D is the diameter of the distillation main engine cylinder, and F' is the steam flow rate inside the distillation main engine.

[0075] Preferably, the method of using a Roots compressor to compress the steam generated by the distillation main engine and analyzing the structure of the Roots compressor specifically includes:

[0076] A Roots compressor is a positive displacement compressor with two rotors whose axes are parallel to each other;

[0077] The rotor is composed of a shaft and an impeller, and there are gaps of preset distances between the impellers, and between the impellers and the casing and the baffle;

[0078] The two rotors are driven by a pair of mutually meshing synchronous gears and rotate in opposite directions at the same angular speed;

[0079] The compressor air inlet and outlet are not directly connected, and the size of the basic volume of the closed space surrounded by the impeller, the casing and the baffle remains unchanged during the rotation process;

[0080] When the elementary volume is connected to the exhaust port, the high-pressure gas flows back to the elementary volume to equalize the pressure, thereby achieving compression of the steam generated by the distillation main unit.

[0081] Preferably, the method of recycling the discharged secondary steam potential by using mechanical steam recompression technology as heating steam to provide a heat source for the MVR system specifically includes:

[0082] In the distillation main unit, a collector is used to collect the secondary steam generated by the concentrated liquid being heated and evaporated;

[0083] The collected secondary steam is input into a Roots compressor for compression. During the compression process, the pressure and temperature of the steam increase.

[0084] The compressed steam is sent back to the heat exchange structure to provide heat source for the MVR system.

[0085] Preferably, the said summarizing and integrating the MVR waste liquid treatment evaporator structure and drawing the overall process integration diagram of the MVR system specifically includes:

[0086] The waste liquid is input into the feed port of the MVR waste liquid treatment evaporator;

[0087] Waste liquid is input into the distillation main unit;

[0088] The waste liquid is heat exchanged through the heat exchange structure;

[0089] The distillation main engine outputs steam and concentrated liquid;

[0090] The steam is input into a Roots compressor for compression to obtain distilled water;

[0091] The secondary steam generated by the concentrated liquid evaporation is collected and input into the Roots compressor for compression, and the compressed steam is sent back to the heat exchange structure.

[0092] Compared with the prior art, the present invention has the following beneficial effects:

[0093] During the evaporation process, the heat released by the secondary steam generated by the evaporation of the concentrated liquid is recovered and input into the heat exchange structure. This efficient heat recovery and utilization technology not only improves the energy utilization efficiency, but also reduces the production cost. It adopts a modular design with a compact structure, small footprint, and easy installation and transportation. At the same time, its integrated design combines various components closely together to improve the overall performance and stability of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0094] Figure 1It is a flow chart of the design method of the low energy consumption MVR waste liquid treatment evaporator structure of the present invention;

[0095] Figure 2 A flow chart of the method for establishing an initial model of a heat exchange structure of the present invention;

[0096] Figure 3 The present invention is a flow chart of a method for taking the sum of equipment investment cost and operation cost as the total cost of the heat exchange structure and outputting it as an objective function of the heat exchange structure model;

[0097] Figure 4 A flow chart of a method for realizing a structural optimization process of an initial model of a heat exchange structure using a genetic algorithm according to the present invention;

[0098] Figure 5 A flow chart of the method for constructing a distillation host structure model of the present invention;

[0099] Figure 6 A flow chart of a method for analyzing the structure of a Roots compressor according to the present invention;

[0100] Figure 7 This is a flow chart of the method for recovering and utilizing the potential of discharged secondary steam using mechanical steam recompression technology of the present invention;

[0101] Figure 8 It is an integrated diagram of the overall process of the MVR system of the present invention. DETAILED DESCRIPTION

[0102] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art may think of other obvious variations.

[0103] Reference Figure 1 As shown, a design method for a low energy consumption MVR waste liquid treatment evaporator structure includes:

[0104] Using the heat transfer effectiveness-heat transfer unit number theory of the heat exchanger, calculate the relevant structural parameters of the heat exchange structure, match and design the heat exchange structure of the MVR system, and establish the initial model of the heat exchange structure;

[0105] The sum of equipment investment cost and operation cost is taken as the total cost of the heat exchange structure, and output as the objective function of the heat exchange structure model;

[0106] Based on the objective function of the heat exchange structure model, the genetic algorithm is used to realize the structural optimization process of the initial model of the heat exchange structure, and the heat exchange structure optimization model is obtained;

[0107] According to the separator design principle, the design model of the distillation host is established, and based on the process parameters in the heat exchange structure optimization model, the structural parameters of the distillation host that matches the MVR system are calculated to construct the distillation host structure model;

[0108] A Roots compressor is used to compress the steam generated by the distillation main engine, and the structure of the Roots compressor is analyzed;

[0109] Mechanical vapor recompression technology is used to recycle the potential of discharged secondary steam and use it as heating steam to provide heat source for the MVR system;

[0110] Summarize and integrate the MVR waste liquid treatment evaporator structure and draw the overall process integration diagram of the MVR system.

[0111] Reference Figure 2 As shown in the figure, the heat transfer effectiveness-heat transfer unit number theory of the heat exchanger is used to calculate the structural parameters related to the heat exchange structure, match the heat exchange structure of the MVR system, and establish the initial model of the heat exchange structure, which includes:

[0112] The steam in the heat exchange structure consists of two parts: steam cooling and condensation. The heat exchange structure is set as a cooling sensible heat section and a condensation latent heat section;

[0113] Based on the heat transfer effectiveness-heat transfer unit number theory, the heat transfer effectiveness of the two heat exchange structures is calculated respectively;

[0114] Calculate the number of heat transfer units in the heat exchange structure;

[0115] Obtaining an empirical value range of the total heat transfer coefficient, and presetting the total heat transfer coefficient of the heat exchange structure based on the empirical value range;

[0116] Use the heat exchange area formula to calculate the initial heat exchange area;

[0117] Preset the inner diameter of the pipe of the heat exchange structure;

[0118] Determine the flow area of ​​the pipe;

[0119] Calculate the number of heat exchange tubes and the length of each heat exchange tube respectively;

[0120] The heat transfer effectiveness-heat transfer unit number theory is:

[0121]

[0122] Where ε is the heat transfer efficiency, t si is the hot end inlet temperature, t ti is the cold end inlet temperature, △t s is the temperature difference between the hot end inlet and outlet, △t t is the temperature difference between the cold end inlet and outlet;

[0123] The number of heat transfer units is:

[0124]

[0125] Where, N is the number of heat transfer units, and f is the relationship function between heat transfer effectiveness and the number of heat transfer units in the preset non-mixing countercurrent heat exchange structure.

[0126] The heat exchange area formula is:

[0127]

[0128] Where k is the overall heat transfer coefficient, A is the initial heat transfer area, and W min is the minimum heat capacity of the waste liquid; the flow area of ​​the tube pass is:

[0129]

[0130] In the formula, S is the tube flow area, F is the steam flow rate, v is the tube flow velocity, and ρ is the steam density; the number of heat exchange tubes is:

[0131]

[0132] In the formula, n is the number of heat exchange tubes, and r is the preset inner diameter of the heat exchange tube;

[0133] The length of each heat exchange tube is:

[0134]

[0135] Where L is the length of each heat exchange tube.

[0136] The number of heat transfer units (NTU) is a parameter that reflects the difficulty of the heat exchange process between cold and hot fluids. It is also a parameter that measures the heat transfer capacity of the heat exchange structure. When using the heat transfer unit number method to calculate the heat exchange process, the concept of heat transfer efficiency must also be introduced. The heat transfer efficiency in the heat exchange structure refers to the ratio of the actual heat transfer of the two fluids to the theoretically possible maximum heat transfer.

[0137] Reference Figure 3 As shown in the figure, the sum of equipment investment cost and operation cost is taken as the total cost of the heat exchange structure, and the output is the objective function of the heat exchange structure model, which specifically includes:

[0138] The total cost of the heat exchange structure includes equipment investment cost and operation cost;

[0139] The equipment investment cost is the investment cost of the heat exchange area;

[0140] Operation cost is the energy cost consumed by the pump to overcome the pressure drop;

[0141] Obtain the heat exchange area parameters of the material selected for the heat exchange structure, that is, the heat exchange area parameters of stainless steel;

[0142] Based on the heat exchange area parameters of stainless steel, the investment cost of the equipment is calculated using the investment cost formula;

[0143] Calculate operating costs using energy cost formula;

[0144] The sum of the output equipment investment cost and the operating cost is the objective function of the heat exchange structure model;

[0145] The investment cost formula is:

[0146]

[0147] In the formula, C 1 is the equipment investment cost, a 1 、a 2 、a 3 are the first, second and third heat transfer area parameters of stainless steel respectively;

[0148] The energy cost formula is:

[0149]

[0150] In the formula, C 2 is the operating cost, η is the efficiency of the pump, △P t , △P s are the pressure losses on the tube side and shell side, respectively.

[0151] The material selected for the heat exchange structure in this article is stainless steel, and the corresponding values ​​of the first, second and third heat exchange area parameters are 8500, 409 and 0.85 respectively.

[0152] Reference Figure 4 As shown in the figure, based on the objective function of the heat exchange structure model, the genetic algorithm is used to realize the structural optimization process of the initial model of the heat exchange structure, and the heat exchange structure optimization model obtained specifically includes:

[0153] S101: randomly generate a heat exchange structure model and a heat exchange structure initial model summary as an initial population;

[0154] S102: Evaluate all individuals in the population according to the objective function of the heat exchange structure model to obtain the fitness value of each individual;

[0155] S103: Select excellent individuals as parents according to fitness values;

[0156] S104: performing a non-equivalent exchange operation between the parent individuals, exchanging the position and content of the heat exchange structure model parameters, and generating new offspring individuals;

[0157] S105: Perform random mutation operation on offspring individuals and introduce new parameter values ​​as genetic genes;

[0158] S106: Replace the non-excellent individuals in the population with the newly generated offspring individuals;

[0159] S107: Determine whether the preset maximum number of iterations has been reached. If so, terminate the iteration and output the current population as a heat exchange structure optimization model. If not, return to step S102.

[0160] Genetic algorithm is an adaptive global optimization probability search algorithm formed by simulating the inheritance and evolution process of organisms in the natural environment. This method starts from any initial population and produces a group of individuals that are more adaptable to the environment through random selection, crossover and mutation operations, so that the group evolves to better and better areas in the search space. In this way, it continues to multiply and evolve from generation to generation, and finally converges to a group of individuals that are most adaptable to the environment to obtain the optimal solution to the problem.

[0161] Reference Figure 5 As shown in the figure, according to the separator design principle, the design model of the distillation host is established, and based on the process parameters in the heat exchange structure optimization model, the structural parameters of the distillation host matching the MVR system are calculated. The construction of the distillation host structural model specifically includes:

[0162] The main distillation unit consists of a cylinder, a feed pipe, a heat exchange pipe, a concentrate outlet, a defoamer and a steam outlet;

[0163] Obtain distillation parameters, waste liquid density and vapor density;

[0164] Use the critical speed formula to calculate the maximum speed at which steam is allowed to pass;

[0165] Calculate the diameter of the distillation main cylinder based on the maximum velocity at which steam is allowed to pass;

[0166] The height of the distillation main engine cylinder is set to be twice the diameter of the distillation main engine cylinder;

[0167] Set the diameter of each interface to the inner diameter of the heat exchange tube;

[0168] Use wire mesh demister to eliminate droplets entrained in steam;

[0169] The critical speed formula is:

[0170]

[0171] In the formula, v max is the maximum velocity of steam allowed to pass, m is the distillation parameter, ρ 1 , 2 are the waste liquid density and steam density respectively;

[0172] The diameter of the distillation main engine cylinder is:

[0173]

[0174] Where D is the diameter of the distillation main engine cylinder, and F' is the steam flow rate inside the distillation main engine.

[0175] The water vapor generated by the distillation main unit will inevitably carry a small amount of liquid during the rising process. These droplets will be sucked into the compressor along with the steam and will cause damage to the high-speed running parts. Therefore, it is necessary to eliminate the entrained droplets before the steam enters the compressor. This process is generally completed by a demister installed in the barrel of the distillation main unit.

[0176] Reference Figure 6 As shown, a Roots compressor is used to compress the steam generated by the distillation main engine, and the structure of the Roots compressor is analyzed, including:

[0177] A Roots compressor is a positive displacement compressor with two rotors whose axes are parallel to each other;

[0178] The rotor is composed of a shaft and an impeller, and there are gaps of preset distances between the impellers, and between the impellers and the casing and the baffle;

[0179] The two rotors are driven by a pair of mutually meshing synchronous gears and rotate in opposite directions at the same angular speed;

[0180] The compressor air inlet and outlet are not directly connected, and the size of the basic volume of the closed space surrounded by the impeller, the casing and the baffle remains unchanged during the rotation process;

[0181] When the elementary volume is connected to the exhaust port, the high-pressure gas flows back to the elementary volume to equalize the pressure, thereby achieving compression of the steam generated by the distillation main unit.

[0182] Roots compressor is a positive displacement compressor. It is a rotary compressor that uses two blade-shaped rotors to make relative motion in the cylinder to compress and transport gas. This type of compressor has a simple structure and is easy to manufacture. It is widely used in aquaculture oxygenation, sewage treatment aeration, cement transportation, and is more suitable for gas transportation and pressurization systems in low-pressure situations. It can also be used as a vacuum pump.

[0183] Reference Figure 7 As shown in the figure, the mechanical vapor recompression technology is used to recycle the potential of the discharged secondary steam and use it as heating steam to provide a heat source for the MVR system. Specifically, it includes:

[0184] In the distillation main unit, a collector is used to collect the secondary steam generated by the concentrated liquid being heated and evaporated;

[0185] The collected secondary steam is input into a Roots compressor for compression. During the compression process, the pressure and temperature of the steam increase.

[0186] The compressed steam is sent back to the heat exchange structure to provide heat source for the MVR system.

[0187] During the evaporation process, the heat released by the secondary steam generated by the evaporation of the concentrated liquid is recovered and input into the heat exchange structure. This efficient heat recovery and utilization technology not only improves energy utilization efficiency, but also reduces production costs.

[0188] Reference Figure 8 As shown in the figure, the MVR waste liquid treatment evaporator structure is summarized and integrated, and the overall process integration diagram of the MVR system is drawn, which specifically includes:

[0189] The waste liquid is input into the feed port of the MVR waste liquid treatment evaporator;

[0190] Waste liquid is input into the distillation main unit;

[0191] The waste liquid is heat exchanged through the heat exchange structure;

[0192] The distillation main engine outputs steam and concentrated liquid;

[0193] The steam is input into a Roots compressor for compression to obtain distilled water;

[0194] The secondary steam generated by the concentrated liquid evaporation is collected and input into the Roots compressor for compression, and the compressed steam is sent back to the heat exchange structure.

[0195] System process integration design is one of the important tasks of the overall system design. Establishing the overall process integration diagram of the MVR system makes the overall system integration and coordination work more flexible, adjustable and visual, improves the design quality and reduces the design cost.

[0196] Furthermore, the present solution also proposes a computer-readable storage medium on which a computer-readable program is stored. When the computer-readable program is called, the above-mentioned design method of the low-energy consumption MVR waste liquid treatment evaporator structure is executed.

[0197] It is understandable that the storage medium may be a magnetic medium, such as a floppy disk, a hard disk, or a magnetic tape; an optical medium, such as a DVD; or a semiconductor medium, such as a solid state drive (SSD).

[0198] In summary, the advantages of the present invention are: during the evaporation process, the heat released by the secondary steam generated by the evaporation of the concentrated liquid is recovered, and the heat can be input into the heat exchange structure. This efficient heat recovery and utilization technology not only improves the energy utilization efficiency, but also reduces the production cost; it adopts a modular design, has a compact structure, occupies a small area, and is easy to install and transport. At the same time, its integrated design combines the various components closely together, improving the overall performance and stability of the equipment.

[0199] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A design method for a low energy consumption MVR waste liquid treatment evaporator structure, characterized in that: include: Using the heat transfer effectiveness-heat transfer unit number theory of the heat exchanger, calculate the relevant structural parameters of the heat exchange structure, match and design the heat exchange structure of the MVR system, and establish the initial model of the heat exchange structure; The sum of equipment investment cost and operation cost is taken as the total cost of the heat exchange structure, and output as the objective function of the heat exchange structure model; Based on the objective function of the heat exchange structure model, the genetic algorithm is used to realize the structural optimization process of the initial model of the heat exchange structure, and the heat exchange structure optimization model is obtained; According to the separator design principle, the design model of the distillation host is established, and based on the process parameters in the heat exchange structure optimization model, the structural parameters of the distillation host that matches the MVR system are calculated to construct the distillation host structure model; A Roots compressor is used to compress the steam generated by the distillation main engine, and the structure of the Roots compressor is analyzed; Mechanical vapor recompression technology is used to recycle the potential of discharged secondary steam and use it as heating steam to provide heat source for the MVR system; Summarize and integrate the MVR waste liquid treatment evaporator structure and draw the overall process integration diagram of the MVR system.

2. The design method of a low-energy consumption MVR waste liquid treatment evaporator structure according to claim 1 is characterized in that: The heat exchanger heat transfer effectiveness-heat transfer unit number theory is used to calculate the relevant structural parameters of the heat exchange structure, match and design the heat exchange structure of the MVR system, and establish the initial model of the heat exchange structure, which specifically includes: The steam in the heat exchange structure consists of two parts: steam cooling and condensation. The heat exchange structure is set as a cooling sensible heat section and a condensation latent heat section; Based on the heat transfer effectiveness-heat transfer unit number theory, the heat transfer effectiveness of the two heat exchange structures is calculated respectively; Calculate the number of heat transfer units in the heat exchange structure; Obtaining an empirical value range of the total heat transfer coefficient, and presetting the total heat transfer coefficient of the heat exchange structure based on the empirical value range; Use the heat exchange area formula to calculate the initial heat exchange area; Preset the inner diameter of the pipe of the heat exchange structure; Determine the flow area of ​​the pipe; Calculate the number of heat exchange tubes and the length of each heat exchange tube respectively; The heat transfer effectiveness-heat transfer unit number theory is: Where ε is the heat transfer efficiency, t si is the hot end inlet temperature, t ti is the cold end inlet temperature, △t s is the temperature difference between the hot end inlet and outlet, △t t is the temperature difference between the cold end inlet and outlet; The number of heat transfer units is: Where, N is the number of heat transfer units, and f is the relationship function between heat transfer effectiveness and the number of heat transfer units in the preset non-mixing countercurrent heat exchange structure. The heat exchange area formula is: Where k is the overall heat transfer coefficient, A is the initial heat transfer area, and W min is the minimum heat capacity of the waste liquid; The tube flow area is: In the formula, S is the flow area of ​​the tube, F is the steam flow rate, v is the flow velocity of the tube, and ρ is the steam density; The number of heat exchange tubes is: In the formula, n is the number of heat exchange tubes, and r is the preset inner diameter of the heat exchange tube; The length of each heat exchange tube is: Where L is the length of each heat exchange tube.

3. The design method of a low energy consumption MVR waste liquid treatment evaporator structure according to claim 2 is characterized in that: The sum of the equipment investment cost and the operation cost is taken as the total cost of the heat exchange structure, and the output is the objective function of the heat exchange structure model, which specifically includes: The total cost of the heat exchange structure includes equipment investment cost and operation cost; The equipment investment cost is the investment cost of the heat exchange area; Operation cost is the energy cost consumed by the pump to overcome the pressure drop; Obtain the heat exchange area parameters of the material selected for the heat exchange structure, that is, the heat exchange area parameters of stainless steel; Based on the heat exchange area parameters of stainless steel, the investment cost of the equipment is calculated using the investment cost formula; Calculate operating costs using energy cost formulas; The sum of the output equipment investment cost and the operating cost is the objective function of the heat exchange structure model; The investment cost formula is: In the formula, C1 is the equipment investment cost, a1, a2, and a3 are the first, second, and third heat exchange area parameters of stainless steel respectively; The energy cost formula is: Where C2 is the operating cost, η is the efficiency of the pump, △P t , △P s are the pressure losses on the tube side and shell side, respectively.

4. The design method of a low-energy consumption MVR waste liquid treatment evaporator structure according to claim 3 is characterized in that: The objective function based on the heat exchange structure model, using genetic algorithm to realize the structural optimization process of the initial model of the heat exchange structure, and obtaining the heat exchange structure optimization model specifically includes: S101: randomly generate a heat exchange structure model and a heat exchange structure initial model summary as an initial population; S102: Evaluate all individuals in the population according to the objective function of the heat exchange structure model to obtain the fitness value of each individual; S103: Select excellent individuals as parents according to fitness values; S104: performing a non-equivalent exchange operation between the parent individuals, exchanging the position and content of the heat exchange structure model parameters, and generating new offspring individuals; S105: Perform random mutation operation on offspring individuals and introduce new parameter values ​​as genetic genes; S106: Replace the non-excellent individuals in the population with the newly generated offspring individuals; S107: Determine whether the preset maximum number of iterations has been reached. If so, terminate the iteration and output the current population as a heat exchange structure optimization model. If not, return to step S102.

5. The design method of a low energy consumption MVR waste liquid treatment evaporator structure according to claim 4 is characterized in that: According to the separator design principle, a design model of the distillation host is established, and based on the process parameters in the heat exchange structure optimization model, the structural parameters of the distillation host matching the MVR system are calculated. The construction of the distillation host structural model specifically includes: The main distillation unit consists of a cylinder, a feed pipe, a heat exchange pipe, a concentrate outlet, a defoamer and a steam outlet; Obtain distillation parameters, waste liquid density and vapor density; Use the critical speed formula to calculate the maximum speed at which steam is allowed to pass; Calculate the diameter of the distillation main cylinder based on the maximum velocity at which steam is allowed to pass; The height of the distillation main engine cylinder is set to be twice the diameter of the distillation main engine cylinder; Set the diameter of each interface to the inner diameter of the heat exchange tube; Use wire mesh demister to eliminate droplets entrained in steam; The critical speed formula is: In the formula, v max is the maximum speed at which steam is allowed to pass, m is the distillation parameter, ρ1 and ρ2 are the waste liquid density and steam density respectively; The diameter of the distillation main engine cylinder is: Where D is the diameter of the distillation main engine cylinder, and F' is the steam flow rate inside the distillation main engine.

6. The design method of a low energy consumption MVR waste liquid treatment evaporator structure according to claim 5 is characterized in that: The method of using a Roots compressor to compress the steam generated by the distillation main engine and analyzing the structure of the Roots compressor specifically includes: A Roots compressor is a positive displacement compressor with two rotors whose axes are parallel to each other; The rotor is composed of a shaft and an impeller, and there are gaps of preset distances between the impellers, and between the impellers and the casing and the baffle; The two rotors are driven by a pair of mutually meshing synchronous gears and rotate in opposite directions at the same angular speed; The compressor air inlet and outlet are not directly connected, and the size of the basic volume of the closed space surrounded by the impeller, the casing and the baffle remains unchanged during the rotation process; When the elementary volume is connected to the exhaust port, the high-pressure gas flows back to the elementary volume to equalize the pressure, thereby achieving compression of the steam generated by the distillation main unit.

7. The design method of a low energy consumption MVR waste liquid treatment evaporator structure according to claim 6 is characterized in that: The mechanical vapor recompression technology is used to recover and utilize the potential of the discharged secondary steam as heating steam to provide a heat source for the MVR system, which specifically includes: In the distillation main unit, a collector is used to collect the secondary steam generated by the concentrated liquid being heated and evaporated; The collected secondary steam is input into a Roots compressor for compression. During the compression process, the pressure and temperature of the steam increase. The compressed steam is sent back to the heat exchange structure to provide heat source for the MVR system.

8. The design method of a low energy consumption MVR waste liquid treatment evaporator structure according to claim 7 is characterized in that: The above-mentioned summarizing and integrating the MVR waste liquid treatment evaporator structure and drawing the overall process integration diagram of the MVR system specifically includes: The waste liquid is input into the feed port of the MVR waste liquid treatment evaporator; Waste liquid is input into the distillation main unit; The waste liquid is heat exchanged through the heat exchange structure; The distillation main engine outputs steam and concentrated liquid; The steam is input into a Roots compressor for compression to obtain distilled water; The secondary steam generated by the concentrated liquid evaporation is collected and input into the Roots compressor for compression, and the compressed steam is sent back to the heat exchange structure.

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