Search

CN-121974425-A - Method and equipment for treating high-salt and high-concentration waste liquid by low-temperature evaporator

CN121974425ACN 121974425 ACN121974425 ACN 121974425ACN-121974425-A

Abstract

The invention relates to the technical field of waste liquid treatment, and discloses a method and equipment for treating high-salt and high-concentration waste liquid by a low-temperature evaporator. The method comprises the steps of detecting feed flow and feed salt concentration of feed waste liquid, calculating a predicted value of secondary steam yield, calculating a target rotation speed of a compressor of a centrifugal steam compressor according to the predicted value of the secondary steam yield, calculating a vacuum degree target value of a vacuum evaporator according to the feed salt concentration, adjusting a real-time first operation rotation speed of the centrifugal steam compressor until the target rotation speed of the compressor is reached, synchronously adjusting the real-time first operation vacuum degree of the vacuum evaporator until the target vacuum degree value is reached, supersaturating and crystallizing concentrated solution discharged by the vacuum evaporator to obtain crystal slurry, and carrying out solid-liquid separation on the crystal slurry to obtain solid salt products and mother liquor. The invention solves the technical problems of heat transfer efficiency reduction and operation instability of the existing MVR evaporation system under a variable load working condition, and further realizes stable resource treatment of high-salt waste liquid.

Inventors

  • LIU SHULI
  • LUO YING
  • LUO SHIKUAN

Assignees

  • 深圳易普乐环保科技有限公司

Dates

Publication Date
20260505
Application Date
20260407

Claims (10)

  1. 1. A method for treating high-salt and high-concentration waste liquid by a low-temperature evaporator, which is characterized by comprising the following steps: detecting the feeding flow rate and the feeding salt concentration of the feeding waste liquid and calculating a secondary steam yield predicted value; Calculating a target rotation speed of a compressor of the centrifugal steam compressor according to the predicted value of the secondary steam yield, and calculating a vacuum degree target value of a vacuum evaporator according to the concentration of the feed salt; Adjusting the real-time first operation rotating speed of the centrifugal steam compressor until reaching the target rotating speed of the compressor, and synchronously adjusting the real-time first operation vacuum degree of the vacuum evaporator until reaching the target vacuum degree value; And supersaturating and crystallizing the concentrated solution discharged from the vacuum evaporator to obtain crystal slurry, and carrying out solid-liquid separation on the crystal slurry to obtain a solid salt product and a mother solution.
  2. 2. The method of treating high salt and high concentration waste liquid by a cryogenic evaporator according to claim 1, wherein detecting the feed flow rate and feed salt concentration of the feed waste liquid and calculating the secondary steam yield predictive value comprises: detecting the feeding flow rate and the feeding salt concentration of the feeding waste liquid; adding the waste liquid density reference value and the result of multiplying the concentration of the feed salt by the density proportionality coefficient to obtain the waste liquid density; dividing the difference between the feed salt concentration and a target concentrated salt concentration by the target concentrated salt concentration based on the feed flow, the waste liquid density and the feed salt concentration, and multiplying the product of the feed flow and the waste liquid density to obtain an evaporation water amount; And multiplying the evaporation water quantity by a preset flash evaporation loss correction coefficient to obtain a secondary steam yield predicted value.
  3. 3. The method for treating high-salt and high-concentration waste liquid by using a low-temperature evaporator according to claim 1, wherein calculating a compressor target rotation speed of a centrifugal vapor compressor according to the secondary vapor yield predicted value and calculating a vacuum degree target value of a vacuum evaporator according to the feed salt concentration comprises: Taking the reference steam treatment capacity of the centrifugal steam compressor under the rated working condition as a set reference steam capacity, differencing the predicted value of the secondary steam yield with the set reference steam capacity to obtain a steam yield difference value, and multiplying the steam yield difference value by a preset rotating speed regulating coefficient to obtain a rotating speed regulating capacity; Superposing the rotation speed regulating quantity and a corresponding set reference rotation speed under a rated working condition to obtain a target rotation speed of the compressor; and calculating a boiling point rise value according to the concentration of the feed salt, and calculating a vacuum degree target value of the vacuum evaporator based on the boiling point rise value and a preset heat transfer temperature difference.
  4. 4. A method of treating high salt and high concentration waste liquid in a cryogenic evaporator according to claim 3, characterized in that calculating a boiling point elevation value from the feed salt concentration and calculating a vacuum target value for a vacuum evaporator based on the boiling point elevation value and a preset heat transfer temperature difference, comprising: substituting the feed salt concentration into a boiling point elevation relation function, and summing the product of a salt concentration primary term coefficient and the feed salt concentration and the product of a salt concentration secondary term coefficient and the square of the feed salt concentration to obtain a boiling point elevation value; And subtracting the sum of the boiling point rise value and a preset heat transfer temperature difference from the compressed steam temperature to obtain a pure water target saturated temperature, and calculating a vacuum degree target value of the vacuum evaporator based on the pure water target saturated temperature.
  5. 5. The method for treating high-salt and high-concentration waste liquid by a low-temperature evaporator according to claim 4, wherein the step of subtracting the sum of the boiling point increase value and a preset heat transfer temperature difference from the compressed steam temperature to obtain a pure water target saturation temperature and calculating a vacuum degree target value of a vacuum evaporator based on the pure water target saturation temperature comprises: subtracting the sum of the boiling point rise value and a preset heat transfer temperature difference from the compressed steam temperature to obtain a pure water target saturation temperature, substituting An Tuoyin the pure water target saturation temperature into a An Tuoyin equation for forward solving to obtain an initial pressure value; And reversely substituting An Tuo the initial pressure value into An Tuo to reversely calculate the pure water saturation temperature according to an equation, so as to reversely calculate the obtained pure water saturation temperature and the pure water target saturation temperature to obtain a temperature deviation value, correcting the pressure value according to the deviation direction if the temperature deviation value exceeds a convergence threshold value, then solving the pressure value in the forward direction again, and circulating until the temperature deviation value is converged within the convergence threshold value to obtain a vacuum degree target value.
  6. 6. The method of treating high salt and high concentration waste liquid by a cryogenic evaporator according to claim 1, wherein adjusting the real-time first operating speed of the centrifugal vapor compressor until the target compressor speed is reached, and synchronously adjusting the real-time first operating vacuum of the vacuum evaporator until the target vacuum level is reached, comprises: calculating a target output frequency of a frequency converter according to the target rotating speed of the compressor and the pole pair number, and adjusting the motor frequency of the centrifugal steam compressor in an S-curve acceleration mode until the difference between the real-time first running rotating speed fed back by the encoder and the target rotating speed of the compressor is converged within a rotating speed tolerance; Collecting real-time first operation vacuum degree of the vacuum evaporator by a vacuum degree sensor, and obtaining a vacuum degree deviation value by making a difference between the vacuum degree and the vacuum degree target value, superposing the product of the vacuum degree deviation value and a valve opening adjustment coefficient with a reference opening, and adjusting the opening of a vacuum pump inlet of the electric adjusting valve until the difference between the first operation vacuum degree and the vacuum degree target value is converged within a pressure tolerance.
  7. 7. The method for treating high-salt and high-concentration waste liquid by using a low-temperature evaporator according to claim 6, wherein the method for treating high-salt and high-concentration waste liquid by using the low-temperature evaporator further comprises: Collecting the temperature, pressure and actual flow of secondary steam at the outlet of the vacuum evaporator and the liquid phase temperature in the evaporator; Dividing the difference between the secondary steam temperature and the liquid phase temperature in the evaporator by a preset heat transfer temperature difference to obtain a heat transfer efficiency index value, performing difference between the heat transfer efficiency index value and target heat transfer efficiency to obtain a heat transfer efficiency deviation value, and adding the product of the heat transfer efficiency deviation value and a rotation speed compensation coefficient to the first operation rotation speed to obtain a second operation rotation speed; dividing the difference between the actual flow of the secondary steam and the predicted value of the secondary steam yield by the predicted value of the secondary steam yield to obtain a steam yield deviation value, and adding the product of the steam yield deviation value and a vacuum degree adjusting coefficient to the first operation vacuum degree to obtain a second operation vacuum degree.
  8. 8. The method for treating a high-salt and high-concentration waste liquid by a low-temperature evaporator according to claim 7, wherein dividing a difference between the secondary steam temperature and the liquid phase temperature in the evaporator by a preset heat transfer temperature difference to obtain a heat transfer efficiency index value, wherein a difference between the heat transfer efficiency index value and a target heat transfer efficiency is obtained to obtain a heat transfer efficiency deviation value, wherein a product of the heat transfer efficiency deviation value and a rotation speed compensation coefficient is added to the first operation rotation speed to obtain a second operation rotation speed, comprising: dividing the difference between the secondary steam temperature and the liquid phase temperature in the evaporator by a preset heat transfer temperature difference to obtain a heat transfer efficiency index value, and obtaining a heat transfer efficiency deviation value by making the heat transfer efficiency index value and the target heat transfer efficiency difference; and multiplying the product of the ratio of the heat transfer efficiency deviation value to the target heat transfer efficiency and the ratio of the preset heat transfer temperature difference to the reference heat transfer temperature difference by a rotation speed compensation reference coefficient to obtain a rotation speed compensation quantity, and adding the rotation speed compensation quantity to the first operation rotation speed to obtain a second operation rotation speed.
  9. 9. The method for treating high-salt and high-concentration waste liquid by using a low-temperature evaporator according to claim 1, wherein the method for supersaturating and crystallizing the concentrated solution discharged from the vacuum evaporator to obtain crystal slurry, and performing solid-liquid separation on the crystal slurry to obtain a solid salt product and a mother solution comprises the following steps: Inputting concentrated solution discharged from the vacuum evaporator into a DTB type forced circulation crystallizer, when a TDS detection value of the concentrated solution reaches a crystallization trigger threshold value, driving the concentrated solution to forcibly circulate along a guide cylinder by a circulating pump according to a set circulation flow rate, and performing supersaturation crystallization on the concentrated solution to obtain crystal slurry; And inputting the crystal slurry into a horizontal spiral unloading centrifugal separator, and carrying out solid-liquid separation on the crystal slurry at a preset rotating speed and a preset separation factor to obtain a solid salt product and a mother solution.
  10. 10. An apparatus for treating high-salt and high-concentration waste liquid by a low-temperature evaporator, characterized by comprising the steps of: the detection module is used for detecting the feeding flow rate and the feeding salt concentration of the feeding waste liquid and calculating a secondary steam yield predicted value; The calculation module is used for calculating the target rotation speed of the centrifugal steam compressor according to the predicted value of the secondary steam yield and calculating the target vacuum degree value of the vacuum evaporator according to the concentration of the feed salt; The adjusting module is used for adjusting the real-time first operation rotating speed of the centrifugal steam compressor until reaching the target rotating speed of the compressor, and synchronously adjusting the real-time first operation vacuum degree of the vacuum evaporator until reaching the target vacuum degree; and the crystallization module is used for supersaturating and crystallizing the concentrated solution discharged by the vacuum evaporator to obtain crystal slurry, and carrying out solid-liquid separation on the crystal slurry to obtain a solid salt product and a mother solution.

Description

Method and equipment for treating high-salt and high-concentration waste liquid by low-temperature evaporator Technical Field The invention relates to the technical field of waste liquid treatment, in particular to a method and equipment for treating high-salt and high-concentration waste liquid by a low-temperature evaporator. Background The evaporation treatment of high-salt/high-concentration waste liquid is a key link of zero emission of industrial waste water, and the Mechanical Vapor Recompression (MVR) technology is widely applied due to the energy efficiency advantage. However, the conventional MVR evaporation system generally adopts an operation mode of a fixed compression ratio and a fixed vacuum degree, and once the system control parameters are set under the design working condition, the system control parameters are not adjusted any more, so that when the feed flow or the salt concentration fluctuates, the processing capacity of the vapor compressor is seriously mismatched with the actual secondary vapor yield, the heat transfer efficiency is greatly reduced, and the energy consumption of the system is obviously increased. In the prior art, the operating pressure of the vacuum evaporator is usually set based on the saturated vapor pressure of pure water, the boiling point rising effect of the high-salt waste liquid is not compensated, the actual heat transfer temperature difference deviates from a design value, the evaporation intensity is unstable, the concentration multiplying power is difficult to ensure, further the dynamic coupling optimization according to the real-time working condition is impossible, the system operation stability is poor under the wide load fluctuation working condition, the fluctuation of the feeding quality of a crystallization section is large, the solid-liquid separation effect is unstable, and the overall efficiency of the high-salt waste liquid recycling treatment is restricted. Disclosure of Invention The invention mainly aims to provide a method and equipment for treating high-salt and high-concentration waste liquid by a low-temperature evaporator, which solve the technical problems of heat transfer efficiency reduction and operation instability of the traditional MVR evaporation system under a variable load working condition by carrying out double-parameter self-adaptive cooperative regulation and control on the rotating speed of a centrifugal vapor compressor and the vacuum degree of a vacuum evaporator, thereby realizing stable recycling treatment of the high-salt waste liquid and improving the robustness and energy efficiency level of a process. In order to achieve the above object, the present invention provides a method for treating high-salt and high-concentration waste liquid by a low-temperature evaporator, comprising the following steps: detecting the feeding flow rate and the feeding salt concentration of the feeding waste liquid and calculating a secondary steam yield predicted value; Calculating a target rotation speed of a compressor of the centrifugal steam compressor according to the predicted value of the secondary steam yield, and calculating a vacuum degree target value of a vacuum evaporator according to the concentration of the feed salt; Adjusting the real-time first operation rotating speed of the centrifugal steam compressor until reaching the target rotating speed of the compressor, and synchronously adjusting the real-time first operation vacuum degree of the vacuum evaporator until reaching the target vacuum degree value; And supersaturating and crystallizing the concentrated solution discharged from the vacuum evaporator to obtain crystal slurry, and carrying out solid-liquid separation on the crystal slurry to obtain a solid salt product and a mother solution. Optionally, in a first implementation form of the first aspect of the invention, detecting a feed flow rate and a feed salt concentration of the feed waste stream and calculating the secondary steam production forecast comprises: detecting the feeding flow rate and the feeding salt concentration of the feeding waste liquid; adding the waste liquid density reference value and the result of multiplying the concentration of the feed salt by the density proportionality coefficient to obtain the waste liquid density; dividing the difference between the feed salt concentration and a target concentrated salt concentration by the target concentrated salt concentration based on the feed flow, the waste liquid density and the feed salt concentration, and multiplying the product of the feed flow and the waste liquid density to obtain an evaporation water amount; And multiplying the evaporation water quantity by a preset flash evaporation loss correction coefficient to obtain a secondary steam yield predicted value. Optionally, in a second implementation manner of the first aspect of the present invention, calculating a target rotation speed of a compressor of the centrifugal steam compr