Energy-saving and consumption-reducing system and method for soda distillation

Abstract

The application provides an energy-saving and consumption-reducing system and method for soda distillation, which comprises at least two flash evaporators, and the outlet of each flash evaporator in the multiple flash evaporators except the last flash evaporator is communicated with the inlet of the next flash evaporator, wherein the inlet of the first flash evaporator in the multiple flash evaporators is used for being communicated with the waste liquid outlet of the mother liquor distillation tower to receive distillation waste liquid; the last flash evaporator has a gas phase outlet and a liquid phase outlet, the gas phase outlet is communicated with a distillation system through a steam vacuum pump to reduce the pressure and temperature in the last flash evaporator through the steam vacuum pump; the liquid phase outlet is communicated with a waste liquid recovery system through a waste liquid conveying pipeline, and the distillation waste liquid flows through the waste liquid conveying pipeline to the waste liquid recovery system through the liquid phase outlet of the last flash evaporator. Through the system provided by the application, the problems of easy scabbing and large heat loss of the waste liquid conveying pipeline are solved.

Description

TECHNICAL FIELD

[0001] The application relates to the field of energy saving and environmental protection, in particular to an energy saving and consumption reducing system and method for soda distillation. BACKGROUND

[0002] With the rapid development of science and technology and the improvement of soda industrial technology, soda has an important position in chemical raw materials, and is widely used in the fields of building material industry, daily chemical industry, papermaking industry, glass industry, metallurgical industry, food industry and the like. The ammonia soda method is one of the mainstream soda production methods for large-scale production of soda in China. In the production of soda by the ammonia soda method, a mother liquor distillation operation process is usually required, ammonia, carbon dioxide and water in the mother liquor are distilled out through a distillation tower to realize the recycling of raw materials, and distillation waste liquid is discharged from the bottom of the tower.

[0003] However, the temperature of the distillation waste liquid discharged from the distillation tower is high, and in the process of discharging the high-temperature distillation waste liquid, on the one hand, calcium sulfate in the distillation waste liquid is prone to scabbing in the pipeline conveying process, causing blockage of the pipeline, and on the other hand, the degree of heat loss of the high-temperature waste liquid is large, causing energy waste and failing to realize effective energy saving and consumption reduction. SUMMARY

[0004] In view of the above problems, one of the purposes of the application is to provide an energy saving and consumption reducing system for soda distillation to solve the problems of easy scabbing of the waste liquid conveying pipeline and large heat loss; and the second purpose of the application is to provide an energy saving and consumption reducing method for soda distillation to realize effective reduction of the temperature of the distillation waste liquid and heat recovery and utilization.

[0005] The first aspect of the application provides an energy saving and consumption reducing system for soda distillation, which adopts the technical scheme of:

[0006] An energy saving and consumption reducing system for soda distillation, comprising at least two stages of flash evaporators, the outlet of each flash evaporator in the multiple stages of flash evaporators except the last stage of flash evaporators being communicated with the inlet of the next stage of flash evaporators, wherein the inlet of the first stage of flash evaporators in the multiple stages of flash evaporators is used for being communicated with the waste liquid outlet of the mother liquor distillation tower to receive distillation waste liquid; and wherein,

[0007] The last stage of flash evaporators has a gas phase outlet and a liquid phase outlet, the gas phase outlet being communicated with a distillation system through a steam vacuum pump to reduce the pressure and temperature in the last stage of flash evaporators through the steam vacuum pump;

[0008] The liquid phase outlet is communicated with a waste liquid recovery system through a waste liquid conveying pipeline, and the distillation waste liquid flows through the waste liquid conveying pipeline to the waste liquid recovery system through the liquid phase outlet of the last stage of flash evaporators; and wherein,

[0009] The steam vacuum pump controls the pressure of the flash steam in the last-stage flash evaporator to be no less than -50 kPa and no greater than -60 kPa, and the temperature of the distillation waste liquid to be no higher than 80°C.

[0010] As one preferred embodiment, the distillation system is provided with two gas phase inlets, one of which is connected to the steam vacuum pump, and the other of which is connected to a steam generator, which is configured to generate external steam.

[0011] As one of the preferred embodiments, the gas phase inlet connected to the steam generator is located at the bottom of the distillation system, and the gas phase inlet connected to the steam vacuum pump is located at the bottom of the second layer of the distillation system.

[0012] As one preferred embodiment, the multi-stage flash evaporator is a two-stage flash evaporator, and the flow rate of the distillation waste liquid is 270 m³ / s. 3 / h, the inner diameter of the last stage flash generator is 5000mm and the height is 8250mm.

[0013] As one of the preferred options, a waste liquid pump is installed on the waste liquid conveying pipeline.

[0014] A second aspect of the present invention also provides an energy-saving and consumption-reducing method for soda ash distillation, which employs the energy-saving and consumption-reducing system for soda ash distillation provided in the first aspect of the present invention, comprising:

[0015] The first-stage flash evaporator receives the distillation waste liquid discharged from the mother liquor distillation column, performs first-stage flash evaporation to form first-stage flash vapor and first-stage distillation waste liquid, and then transports the first-stage flash vapor and the first-stage distillation waste liquid to the next-stage flash evaporator.

[0016] The last-stage flash evaporator receives the corresponding-stage flash vapor and corresponding-stage distillation waste liquid output from the previous-stage flash evaporator. The vacuum level in the last-stage flash evaporator is controlled by a steam vacuum pump to perform the last-stage flash, forming flash vapor and distillation waste liquid.

[0017] Specifically, the vacuum level in the last-stage flash evaporator is controlled so that the pressure of the flash vapor in the last-stage flash evaporator is not less than -50 kPa and not greater than -60 kPa, and the temperature of the distillation waste liquid is not higher than 80°C.

[0018] The flash vapor is delivered to the distillation system via the gas phase outlet of the last-stage flash evaporator, while the distillation waste liquid is discharged to the waste liquid recovery system via the waste liquid delivery pipeline through its liquid phase outlet.

[0019] As one of the preferred solutions, the method includes:

[0020] The target component is recovered by distillation using a distillation system that receives the flash steam output from the last-stage flash evaporator and simultaneously receives external steam output from the steam generator.

[0021] As one preferred embodiment, the method of receiving flash steam output from the last-stage flash evaporator using a distillation system, while simultaneously receiving external steam output from the steam generator, includes:

[0022] The external steam generated by the steam generator enters the bottom of the distillation system, while the flash steam generated in the last stage flash evaporator enters the second-level bottom of the distillation system.

[0023] As one preferred embodiment, the step of discharging the distillation waste liquid into the waste liquid recovery system via a waste liquid conveying pipeline through its own liquid phase outlet includes:

[0024] The distillation waste liquid is pumped into the waste liquid conveying pipeline using a waste liquid pump, and then discharged into the waste liquid recycling system.

[0025] As one preferred embodiment, the distillation system receiving the flash vapor output from the last-stage flash evaporator and simultaneously receiving external steam output from the steam generator for distillation recovery of the target component includes:

[0026] The mother liquor in the distillation system is heated by the flash steam and the external steam, causing the ammonia, carbon dioxide and water vapor in the mother liquor to volatilize, while the less volatile components are deposited, thus separating the components with different volatility and recycling them separately.

[0027] Compared with the prior art, this application has the following advantages:

[0028] This invention proposes an energy-saving and consumption-reducing system for soda ash distillation, comprising at least two stages of flash evaporators. The outlet of each stage of the flash evaporators (excluding the last stage) is connected to the inlet of the next stage. The inlet of the first stage flash evaporator is connected to the waste liquid outlet of the mother liquor distillation column to receive distillation waste liquid.

[0029] The final-stage flash evaporator has a gas phase outlet and a liquid phase outlet. The gas phase outlet is connected to the distillation system via a steam vacuum pump to reduce the pressure and temperature within the final-stage flash evaporator. The liquid phase outlet is connected to a waste liquid recovery system via a waste liquid delivery pipeline. The distillation waste liquid flows from the liquid phase outlet of the final-stage flash evaporator through the waste liquid delivery pipeline to the waste liquid recovery system. The steam vacuum pump controls the pressure of the flash vapor within the final-stage flash evaporator to be no less than -50 kPa and no greater than -60 kPa, and the temperature of the distillation waste liquid to be no higher than 80°C.

[0030] By adopting the technical solution of this application, the pressure and temperature inside the flash evaporator are controlled by a steam vacuum pump, providing a sufficiently adjustable vacuum level. This adjustable vacuum level enables more accurate temperature control. Increasing the vacuum level effectively reduces the pressure and temperature inside the flash evaporator. On one hand, the temperature of the distillation waste liquid inside the flash evaporator is significantly reduced. At lower temperatures, the solubility of calcium sulfate increases, slowing the deposition rate and reducing scaling, thus maintaining normal product production. On the other hand, under low pressure, part of the distillation waste liquid evaporates to form flash steam. This flash steam carries away some of the heat from the distillation waste liquid, serving as a power source for the distillation system. This not only recovers the heat from the distillation waste liquid but also further reduces its temperature and volume, decreasing the amount of waste liquid to be treated, saving energy, and reducing additional energy consumption. This solves the problem of scaling in waste liquid transport pipelines while simultaneously reducing the energy consumption of the equipment.

[0031] The energy-saving and consumption-reducing method for soda ash distillation provided in this embodiment of the invention has the same advantages over the prior art as the energy-saving and consumption-reducing system for soda ash distillation described above, and will not be repeated here. Attached Figure Description

[0032] To more clearly illustrate the technical solution of this application, the drawings used in the description of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a process flow diagram of an energy-saving and consumption-reducing system for soda ash distillation according to an embodiment of this application;

[0034] Figure 2 This is a flowchart of the steps of an embodiment of the energy-saving and consumption-reducing method for soda ash distillation described in this application.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1. Final stage flash evaporator; 2. Steam vacuum pump; 3. Waste liquid pump; 4. Waste liquid delivery pipeline; 5. Distillation system. Detailed Implementation

[0037] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] The background of this invention mentions that the temperature of the distillation waste liquid discharged from the distillation tower is relatively high. During the discharge of this high-temperature waste liquid, on the one hand, the calcium sulfate in the waste liquid easily forms scale during pipeline transportation, causing blockages; on the other hand, the high-temperature waste liquid has a large heat loss, resulting in energy waste and failing to achieve effective energy conservation and consumption reduction. It is understood that the distillation waste liquid contains a large amount of heat energy, which cannot be utilized by direct discharge, thus leading to energy waste. Recovering this heat energy and utilizing it in processes requiring heating not only saves energy but also reduces additional energy consumption, thereby helping to improve the energy efficiency and environmental performance of various industries.

[0039] In related technologies, some alkali production enterprises have implemented measures to address the high-temperature distillation waste liquid, aiming to achieve energy conservation, emission reduction, and environmental protection. Existing energy recovery systems for distillation waste liquid involve flashing the waste liquid from the distillation tower in soda ash production in a first flash evaporator. The waste liquid then enters a second flash evaporator for further flashing to lower its temperature. The flash vapor and steam from the second flash evaporator are introduced into the condensate distillation tower via a steam jet pump, serving as the steam source for the condensate distillation tower. In this system, the pressure of the flash vapor in the second flash evaporator needs to be controlled by the negative pressure of the distillation tower to further cool the waste liquid.

[0040] Because the temperature of the distillation waste liquid in the second flash evaporator is limited by the pressure of the flash vapor inside the second flash evaporator, and the operating conditions of controlling the pressure of the flash vapor by the negative pressure of the distillation column cannot provide a higher vacuum degree for the flash vapor inside the second flash evaporator, the temperature of the distillation waste liquid cannot be further reduced. After research, it was found that the lowest temperature of the distillation waste liquid discharged from the first flash evaporator in this process system is 98°C, the pressure of the flash vapor discharged from the second flash evaporator is -30 kPa, and the temperature of the distillation waste liquid discharged from the second flash evaporator is 92°C.

[0041] It is known that even if the vapor emitted by the waste liquid is recovered before the waste liquid is discharged in the existing technology, the waste liquid is still at a high temperature. The calcium sulfate in the distillation waste liquid has a lower solubility at higher temperatures within the temperature range of 50℃-100℃, and the scaling phenomenon in the waste liquid conveying pipeline 4 is still very prominent.

[0042] It should be noted that the presence of scaling narrows the pipes, restricting the smooth flow of waste liquid and causing a series of adverse phenomena such as blockage, clogging, or liquid backflow during production, affecting production efficiency and normal operation. Scaling also roughens the inner surface of the pipe, increasing the frictional resistance when waste liquid flows through the pipe, resulting in additional pressure loss and increasing the energy consumption of equipment such as waste liquid pump 3, thus affecting energy efficiency. Scaling adheres to the inner wall of the pipe and is difficult to remove and maintain. If the scaling layer grows too thick or is difficult to remove, production needs to be stopped or special cleaning measures need to be taken, which may even lead to safety risks such as production stoppage and equipment failure, increasing maintenance and production costs and time.

[0043] At the same time, the distillation waste liquid still carries away most of the heat, resulting in energy waste and failing to fundamentally solve the problem of energy conservation and consumption reduction.

[0044] Reference Figure 1 As shown, Figure 1 An exemplary energy-saving and consumption-reducing system for soda ash distillation according to some embodiments of this disclosure is shown, comprising at least two flash evaporators. The outlet of each flash evaporator (excluding the last flash evaporator 1) is connected to the inlet of the next flash evaporator. The inlet of the first flash evaporator is connected to the waste liquid outlet of the mother liquor distillation column to receive distillation waste liquid. The last flash evaporator 1 has a gas phase outlet and a liquid phase outlet. The gas phase outlet is connected to the distillation system 5 via a steam vacuum pump 2 to reduce the pressure and temperature within the last flash evaporator 1. The liquid phase outlet is connected to a waste liquid recovery system via a waste liquid conveying pipe 4. The distillation waste liquid flows from the liquid phase outlet of the last flash evaporator 1 through the waste liquid conveying pipe 4 to the waste liquid recovery system.

[0045] The steam vacuum pump 2 controls the pressure of the flash steam in the last-stage flash evaporator 1 to be no less than -50 kPa and no greater than -60 kPa, and the temperature of the distillation waste liquid to be no higher than 80°C.

[0046] Specifically, a multi-stage flash evaporator can be understood as multiple flash evaporators with the same function but located in different positions within the system. The names of the first-stage flash evaporator to the last-stage flash evaporator 1 are based on the flow sequence of the distillation waste liquid. That is, the first flash evaporator is the one that first comes into contact with the distillation waste liquid, the previous-stage flash evaporator comes into contact with the distillation waste liquid earlier than the next-stage flash evaporator, and the last-stage flash evaporator 1 is the one that last comes into contact with the distillation waste liquid and is used to directly discharge the distillation waste liquid.

[0047] A flash evaporator can be defined as a container that allows the volatile components in a substance to evaporate by controlling pressure. In this embodiment of the invention, the flash evaporator is applied to the ammonia-soda process for soda ash production. It can be installed upstream of the distillation system 5 to input the flash vapor formed within the flash evaporator into the distillation system 5, or it can be installed downstream of the mother liquor distillation tower for energy recovery before the distillation waste liquid is discharged. Each stage of the flash evaporator has its inlet for receiving distillation waste liquid. Through depressurization, the volatile components in the distillation waste liquid expand and evaporate under negative pressure, forming flash vapor.

[0048] It should be noted that in this embodiment, the mother liquor distillation tower is a distillation tower used to recover ammonia and carbon dioxide in the ammonia-soda process for producing soda ash. The distillation waste liquid discharged from the mother liquor distillation tower can refer to the mixed waste liquid after the mother liquor containing ammonia, which is filtered for heavy soda, has been distilled in the distillation tower (after recovering ammonia and carbon dioxide). It usually contains impurities such as calcium chloride, sodium chloride, calcium carbonate, calcium sulfate, magnesium hydroxide, calcium oxide, and acid-insoluble substances.

[0049] The flash vapor generated after each stage of the flash evaporator can be understood as part of the distillation waste liquid, specifically the saturated vapor formed by the evaporation of water from the distillation waste liquid. It should be noted that the distillation waste liquid may also carry small amounts of ammonia or other volatile components, which, together with water, expand and evaporate as volatile components to form flash vapor.

[0050] It is understandable that the composition of the distillation waste liquid in each stage of the flash evaporator is almost the same, but the state is different. That is to say, after flashing through multiple stages of flash evaporators, the temperature of the distillation waste liquid in the next stage flash evaporator is lower than that in the previous stage flash evaporator, while the content of flash vapor is higher than that in the previous stage flash evaporator. Specifically, the distillation waste liquid in the first stage flash evaporator comes from the waste liquid outlet of the mother liquor distillation column. The initial temperature of this distillation waste liquid is about 103°C. After flashing through the first stage flash evaporator, the temperature of the distillation waste liquid discharged from the outlet of the first stage flash evaporator can drop to about 98°C.

[0051] More specifically, except for the last-stage flash evaporator 1, the outlet of each stage flash evaporator is connected to the inlet of the previous stage flash evaporator, and the outlet of the last-stage flash evaporator 1 is connected to the distillation system 5 and the waste liquid recovery system via a gas phase outlet and a liquid phase outlet, respectively. The gas phase outlet can be defined as the outlet that outputs flash vapor, and the liquid phase outlet can be defined as the outlet that outputs distillation waste liquid.

[0052] In some embodiments, the flash vapor can be used as motive steam to be transported from the gas phase outlet to the distillation system 5. The distillation system 5 can be understood as a distillation system 5 for distilled liquor, a mother liquor distillation system 5, or other equipment requiring a heat source, thereby utilizing the heat from the distillation waste liquid for recovery and utilization, achieving energy saving and consumption reduction. The mother liquor distillation system 5 can be understood as the mother liquor distillation tower in this embodiment, which realizes the distillation treatment process of returning the flash vapor from the distillation waste liquid to the mother liquor distillation tower for filtering the ammonia-containing mother liquor after heavy alkali treatment. In some embodiments, the distillation waste liquid discharged from the mother liquor distillation tower enters the first-stage flash evaporator, or is also discharged to the waste liquid recovery system.

[0053] In some embodiments, the distillation waste liquid can be discharged from the liquid phase outlet to a waste liquid recovery system, which can be understood as a recovery device corresponding to the components in the distillation waste liquid, to recover calcium chloride and / or sodium chloride, etc., respectively.

[0054] The vapor phase outlet is connected to the distillation system 5 via a steam vacuum pump 2. The steam vacuum pump 2 can be understood as a device that lowers the boiling point of a gas or liquid by controlling the vacuum level, causing a phase change at a lower temperature. Connecting the steam vacuum pump 2 to the flash evaporator allows control of the vacuum level, which in turn controls the temperature and pressure within the flash evaporator. These temperatures and pressures directly determine the formation of flash vapor and the temperature of the distillation waste liquid. Generally, the higher the vacuum level, the lower the pressure within the flash evaporator, and the lower the temperature of the distillation waste liquid.

[0055] Preferably, this embodiment of the invention uses a two-stage flash evaporator. That is, the last flash evaporator 1 is the second-stage flash evaporator. The first-stage flash evaporator performs primary flash evaporation, where the distillation waste liquid expands under reduced pressure to form primary flash vapor. This step can be achieved by adjusting the pressure reducing valve. The primary flash vapor and the unflashed distillation waste liquid enter the second-stage flash evaporator for secondary flash evaporation, forming secondary flash vapor. The vacuum level inside the second-stage flash evaporator is precisely adjusted by the steam vacuum pump 2. If the temperature of the waste liquid is controlled to be less than 80°C, the vacuum level of the flash evaporator is controlled between -50 kPa and -60 kPa.

[0056] In this embodiment, the model and maximum vacuum degree of the steam vacuum pump 2 can be selected according to the discharge volume of the distillation waste liquid. With a two-stage flash evaporator system, the discharge volume of the distillation waste liquid is 270m³. 3 The distillation waste liquid entering the second-stage flash evaporator at a temperature of 98℃ can be controlled at a pumping speed of 12000 m / h using steam vacuum pump 2. 3 / h, the discharge rate of flash steam is 10180m³ / h. 3 / h, 1m 3 The flash vapor emission of the distillation waste liquid is approximately 37.7 m³. 3 The temperature of the distillation waste liquid discharged from the liquid phase outlet of the second-stage flash evaporator drops to 80°C, per 1m3 The distillation waste liquid can recover 22.6 kg of steam, and 10 m³ of steam is generated for every 1 ton of soda ash produced. 3 The waste liquid can save approximately 23 kg of standard coal.

[0057] Compared to existing technologies that use negative pressure in the distillation column to control the pressure of flash vapor in the second flash evaporator to further cool the waste liquid, the discharge temperature of the distilled waste liquid is around 98°C, which is relatively high. This invention, however, uses a steam vacuum pump 2 to control the pressure and temperature within the flash evaporator. This provides a sufficiently adjustable vacuum level within the flash evaporator, avoiding the drawback of using negative pressure in the distillation system 5 to adjust the pressure within the flash evaporator, which fails to further reduce the temperature of the distilled waste liquid. The adjustable vacuum level enables more accurate temperature control, effectively reducing the pressure and temperature within the flash evaporator. This ensures that the pressure of the flash vapor in the final flash evaporator 1 is controlled between -50 kPa and -60 kPa, and the temperature of the distilled waste liquid does not exceed 80°C.

[0058] At this temperature, as the distillation waste liquid is discharged to the waste liquid recovery system through waste liquid conveying pipe 4, the solubility of calcium sulfate increases, which solves the scaling phenomenon of calcium sulfate in the distillation waste liquid during pipeline transportation and solves a series of adverse effects caused by scaling.

[0059] At the same time, the frictional resistance of the distilled waste liquid at a lower temperature decreases when it flows through the pipeline, avoiding additional pressure loss. The waste liquid pump 3 installed on the waste liquid conveying pipeline 4 will not increase the energy consumption of the waste liquid pump 3 and other equipment while pumping the waste liquid.

[0060] Furthermore, it further reduces the heat loss of distillation waste liquid, achieving more effective energy saving and consumption reduction while solving the problem of scaling in waste liquid conveying pipeline 4.

[0061] As a specific explanation of this embodiment, in a two-stage flash evaporator system, the discharge rate of distillation waste liquid is 270m³. 3 / h, the size of the second-stage flash evaporator can be φ5000×8250. The second-stage flash evaporator with this size can avoid the entrainment of foam in the flash vapor.

[0062] In a further technical solution, the distillation system 5 is provided with two gas phase inlets. One gas phase inlet is connected to the steam vacuum pump 2, and the other gas phase inlet is connected to a steam generator configured to produce external steam. In this embodiment, the steam entering the distillation system 5 can be divided into recovered flash steam and external steam. The external steam still enters from the bottom of the distillation system 5. The flash steam output from the second-stage flash evaporator is introduced to the bottom of the second-stage column via the steam vacuum pump 2 as supplementary steam for the condensate distillation column. The two steam streams enter the distillation system 5 through different pipelines to achieve independent control of the flash steam and the external steam, allowing for flexible adjustment of their flow rates and temperatures according to actual production needs to meet the requirements of different process conditions.

[0063] In some embodiments, the external steam can be high-temperature, high-pressure steam supplied from an external source. The steam generating device can be a coal-fired, gas-fired boiler, or other high-temperature, high-pressure steam equipment. The external steam provides a large amount of heat, working in conjunction with the flash steam to provide sufficient heat to meet the needs of the entire distillation process. The introduction of flash steam reduces the amount of additional external steam required, thereby reducing energy consumption.

[0064] It should be explained that the mother liquor distillation tower, flash evaporator, steam vacuum pump 2, waste liquid pump 3, distillation system 5, and waste liquid conveying pipeline 4 in the system of the present invention are all devices with known functions. For clarity and brevity, some descriptions of known functions and structures have been omitted in the description of the corresponding devices. For other details not covered, please refer to existing devices configured with the functions described in the present invention.

[0065] Reference Figure 2 As shown, Figure 2 The flowchart illustrates the steps of an energy-saving and consumption-reducing method for soda ash distillation according to the present invention. Another aspect of the present invention is to propose an energy-saving and consumption-reducing method for soda ash distillation, which employs the energy-saving and consumption-reducing system for soda ash distillation provided in the embodiments of the present invention. The method includes the following steps:

[0066] S101. The first-stage flash evaporator receives the distillation waste liquid discharged from the mother liquor distillation tower, performs first-stage flash evaporation to form first-stage flash vapor and first-stage distillation waste liquid, and then transports the first-stage flash vapor and the first-stage distillation waste liquid to the next-stage flash evaporator.

[0067] S102. The last-stage flash evaporator 1 receives the corresponding-stage flash vapor and corresponding-stage distillation waste liquid output from the previous-stage flash evaporator. The vacuum degree in the last-stage flash evaporator 1 is controlled by the steam vacuum pump 2 to perform the last-stage flash evaporation, forming flash vapor and distillation waste liquid.

[0068] Control the vacuum level in the last stage flash evaporator 1 so that the pressure of the flash vapor in the last stage flash evaporator 1 is not less than -50 kPa and not greater than -60 kPa, and the temperature of the distillation waste liquid is not higher than 80°C.

[0069] S103. The flash vapor is transported to the distillation system 5 through the gas phase outlet of the last-stage flash evaporator 1, while the distillation waste liquid is discharged to the waste liquid recovery system through the waste liquid transport pipeline 4 via its liquid phase outlet.

[0070] Furthermore,

[0071] The method further includes the following steps:

[0072] S104. The distillation system 5 receives the flash steam output from the last-stage flash evaporator 1, and simultaneously receives external steam output from the steam generator, to perform distillation and recover the target component.

[0073] Furthermore, step S104 includes:

[0074] S105. The external steam generated by the steam generator enters the bottom of the distillation system 5, while the flash steam generated in the last stage flash evaporator 1 enters the second-level bottom of the distillation system 5.

[0075] Furthermore,

[0076] Step S103 includes:

[0077] S106. The waste liquid is pumped into the waste liquid conveying pipeline 4 using the waste liquid pump 3, and then discharged into the waste liquid recovery system.

[0078] Furthermore, step S104 or step S105 includes:

[0079] S107. The mother liquor in the distillation system 5 is heated by the flash steam and the external steam, causing the ammonia, carbon dioxide and water vapor in the mother liquor to volatilize, and the non-volatile components to settle, thus separating the components with different volatility and recycling them respectively.

[0080] It should be noted that in step S107, the distillation process of a mother liquor distillation tower can be referenced to recover ammonia, carbon dioxide, and water vapor from the mother liquor entering the distillation tower. The working process of the mother liquor distillation tower utilizes the differences in volatility of the components in the mother liquor, employing multiple partial vaporization and condensation processes to continuously separate light and heavy components. Flash steam and external steam enter the lower part of the distillation tower as heat sources. The heat source flows upward and contacts the downward-flowing mother liquor. After the mother liquor is heated by steam, the volatile ammonia, carbon dioxide, and water in the mother liquor rise, while the less volatile components (the impurities in the distillation waste liquid mentioned above) settle downward. The ammonia, carbon dioxide, and water vapor exiting from the top of the distillation tower are condensed by a cooler at the top and stored for later recovery.

[0081] The recovered ammonia can be processed in an ammonia absorption tower, the recovered carbon dioxide in a carbonization tower, and the recovered water vapor in a refined salt processing step. Non-volatile components are discharged as distillation waste liquid to a waste liquid recovery system. When distillation system 5 is a distillation system for distilled liquids, the non-volatile components are discharged as distillation waste distillate to the waste liquid recovery system.

[0082] The method provided by the present invention will be illustrated below with specific examples.

[0083] Example 1:

[0084] S11. The first-stage flash evaporator receives the distillation waste liquid discharged from the mother liquor distillation tower, performs first-stage flash evaporation to form first-stage flash vapor and first-stage distillation waste liquid, and then transports the first-stage flash vapor and the first-stage distillation waste liquid to the second-stage flash evaporator.

[0085] S12. The second-stage flash evaporator receives the first-stage flash vapor and first-stage distillation waste liquid output from the first-stage flash evaporator. The vacuum degree in the second-stage flash evaporator is controlled to be -50Kpa by the steam vacuum pump 2 to perform the final flash evaporation, forming flash vapor and distillation waste liquid.

[0086] S13. The flash vapor is transported to the distillation system 5 through the gas phase outlet of the second-stage flash evaporator, and the distillation waste liquid is discharged to the waste liquid recovery system through the waste liquid transport pipeline 4 through its liquid phase outlet.

[0087] The temperature of the distillation waste liquid in Example 1 was measured and found to be 80°C.

[0088] Example 2:

[0089] S21. The first-stage flash evaporator receives the distillation waste liquid discharged from the mother liquor distillation tower, performs first-stage flash evaporation to form first-stage flash vapor and first-stage distillation waste liquid, and then transports the first-stage flash vapor and the first-stage distillation waste liquid to the second-stage flash evaporator.

[0090] S22. The second-stage flash evaporator receives the first-stage flash vapor and first-stage distillation waste liquid output from the first-stage flash evaporator. The vacuum degree in the second-stage flash evaporator is controlled to be -53Kpa by the steam vacuum pump 2 to perform the final flash evaporation, forming flash vapor and distillation waste liquid.

[0091] S23. The flash vapor is transported to the distillation system 5 through the gas phase outlet of the second-stage flash evaporator, and the distillation waste liquid is discharged to the waste liquid recovery system through the waste liquid conveying pipeline 4 through its liquid phase outlet.

[0092] The temperature of the distillation waste liquid in Example 2 was measured and found to be 78°C.

[0093] Example 3:

[0094] S31. The first-stage flash evaporator receives the distillation waste liquid discharged from the mother liquor distillation tower, performs first-stage flash evaporation to form first-stage flash vapor and first-stage distillation waste liquid, and then transports the first-stage flash vapor and the first-stage distillation waste liquid to the second-stage flash evaporator.

[0095] S32. The second-stage flash evaporator receives the first-stage flash vapor and first-stage distillation waste liquid output from the first-stage flash evaporator. The vacuum degree in the second-stage flash evaporator is controlled to be -56Kpa by the steam vacuum pump 2 to perform the final flash evaporation, forming flash vapor and distillation waste liquid.

[0096] S33. The flash vapor is transported to the distillation system 5 through the gas phase outlet of the second-stage flash evaporator, and the distillation waste liquid is discharged to the waste liquid recovery system through the waste liquid transport pipeline 4 through its liquid phase outlet.

[0097] The temperature of the distillation waste liquid in Example 3 was measured and found to be 77°C.

[0098] Example 4:

[0099] S41. The first-stage flash evaporator receives the distillation waste liquid discharged from the mother liquor distillation tower, performs first-stage flash evaporation to form first-stage flash vapor and first-stage distillation waste liquid, and then transports the first-stage flash vapor and the first-stage distillation waste liquid to the second-stage flash evaporator.

[0100] S42. The second-stage flash evaporator receives the first-stage flash vapor and the first-stage distillation waste liquid output from the first-stage flash evaporator. The vacuum degree in the second-stage flash evaporator is controlled to be -58Kpa by the steam vacuum pump 2 to perform the final flash evaporation, forming flash vapor and distillation waste liquid.

[0101] S43. The flash vapor is transported to the distillation system 5 through the gas phase outlet of the second-stage flash evaporator, and the distillation waste liquid is discharged to the waste liquid recovery system through the waste liquid transport pipeline 4 through its liquid phase outlet.

[0102] The temperature of the distillation waste liquid in Example 4 was measured and found to be 76.5℃.

[0103] Example 5:

[0104] S51. The first-stage flash evaporator receives the distillation waste liquid discharged from the mother liquor distillation tower, performs first-stage flash evaporation to form first-stage flash vapor and first-stage distillation waste liquid, and then transports the first-stage flash vapor and the first-stage distillation waste liquid to the second-stage flash evaporator.

[0105] S52. The second-stage flash evaporator receives the first-stage flash vapor and the first-stage distillation waste liquid output from the first-stage flash evaporator. The vacuum degree in the second-stage flash evaporator is controlled to be -60Kpa by the steam vacuum pump 2 to perform the final flash evaporation, forming flash vapor and distillation waste liquid.

[0106] S53. The flash vapor is transported to the distillation system 5 through the gas phase outlet of the second-stage flash evaporator, and the distillation waste liquid is discharged to the waste liquid recovery system through the waste liquid conveying pipeline 4 through its liquid phase outlet.

[0107] The temperature of the distillation waste liquid in Example 5 was measured and found to be 75°C.

[0108] Comparative Example 1:

[0109] Unlike Example 1, the maximum vacuum level inside the second-stage flash evaporator is adjusted to -30 kPa using the negative pressure of the distillation column connected to the second flash evaporator, and the steps are the same as in Example 1.

[0110] The temperature of the distillation waste liquid in Comparative Example 1 was measured to be 92℃.

[0111] In summary, the energy-saving and consumption-reducing system for soda ash distillation provided by this invention can control the vacuum degree of the flash evaporator between -50KPa and -60KPa, and can reduce the temperature of the distillation waste liquid to below 80°C. After running the method provided in Example 5 for one year, a cut was made in the waste liquid conveying pipe 4, and no scaling was observed.

[0112] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0113] It should also be noted that, in this document, the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations, nor should they be construed as indicating or implying relative importance. Moreover, the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device.

[0114] The above provides a detailed description of an energy-saving and consumption-reducing system and method for soda ash distillation provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand this application, and the content of this specification should not be construed as a limitation of this application. Furthermore, those skilled in the art will recognize that, based on this application, there will be various modifications in specific implementation methods and application scope. It is neither necessary nor possible to exhaustively list all implementation methods here, but obvious variations or modifications derived therefrom are still within the protection scope of this application.

Claims

1. An energy-saving and consumption-reducing system for soda ash distillation, characterized in that, The system includes at least two stages of flash evaporators. The outlet of each stage of the flash evaporator (excluding the last stage) is connected to the inlet of the next stage. The inlet of the first stage of the flash evaporator is connected to the waste liquid outlet of the mother liquor distillation column to receive distillation waste liquid. The last-stage flash evaporator has a gas phase outlet and a liquid phase outlet. The gas phase outlet is connected to the distillation system via a steam vacuum pump to reduce the pressure and temperature inside the last-stage flash evaporator. The distillation system has two gas phase inlets, one of which is connected to the steam vacuum pump, and the other is connected to a steam generator configured to generate external steam. The gas phase inlet connected to the steam generator is located at the bottom of the distillation system, and the gas phase inlet connected to the steam vacuum pump is located at the bottom of the second-stage distillation system. The liquid phase outlet is connected to the waste liquid recovery system via a waste liquid conveying pipeline. The distillation waste liquid flows from the liquid phase outlet of the last-stage flash evaporator through the waste liquid conveying pipeline to the waste liquid recovery system. The steam vacuum pump controls the pressure of the flash steam in the last-stage flash evaporator to be no less than -50 kPa and no greater than -60 kPa, and the temperature of the distillation waste liquid to be no higher than 80°C.

2. The energy-saving and consumption-reducing system for soda ash distillation according to claim 1, characterized in that, The multi-stage flash evaporator is a two-stage flash evaporator, and the flow rate of the distillation waste liquid is 270 m³ / s. 3 / h, the inner diameter of the last stage flash generator is 5000mm and the height is 8250mm.

3. The energy-saving and consumption-reducing system for soda ash distillation according to claim 1, characterized in that, A waste liquid pump is installed on the waste liquid conveying pipeline.

4. An energy-saving and consumption-reducing method for soda ash distillation, characterized in that, The system for soda ash distillation as described in any one of claims 1 to 3 is used, comprising: The first-stage flash evaporator receives the distillation waste liquid discharged from the mother liquor distillation column, performs first-stage flash evaporation to form first-stage flash vapor and first-stage distillation waste liquid, and then transports the first-stage flash vapor and the first-stage distillation waste liquid to the next-stage flash evaporator. The last-stage flash evaporator receives the corresponding-stage flash vapor and corresponding-stage distillation waste liquid output from the previous-stage flash evaporator. The vacuum level in the last-stage flash evaporator is controlled by a steam vacuum pump to perform the last-stage flash, forming flash vapor and distillation waste liquid. Specifically, the vacuum level in the last-stage flash evaporator is controlled so that the pressure of the flash vapor in the last-stage flash evaporator is not less than -50 kPa and not greater than -60 kPa, and the temperature of the distillation waste liquid is not higher than 80°C. The flash vapor is delivered to the distillation system via the gas phase outlet of the last-stage flash evaporator, while the distillation waste liquid is discharged to the waste liquid recovery system via the waste liquid delivery pipeline through its liquid phase outlet. The distillation system receives the flash vapor output from the last-stage flash evaporator and simultaneously receives external steam output from the steam generator to distill and recover the target component. This includes: the external steam generated by the steam generator enters the bottom of the distillation system, while the flash vapor generated in the last-stage flash evaporator enters the bottom of the second-stage distillation system.

5. The energy-saving and consumption-reducing method for soda ash distillation according to claim 4, characterized in that, The step of discharging the distillation waste liquid into the waste liquid recovery system via its own liquid phase outlet through a waste liquid conveying pipeline includes: The distillation waste liquid is pumped into the waste liquid conveying pipeline using a waste liquid pump, and then discharged into the waste liquid recycling system.

6. The energy-saving and consumption-reducing method for soda ash distillation according to claim 4, characterized in that, The process of using a distillation system to receive the flash vapor output from the last-stage flash evaporator and simultaneously receive external steam output from the steam generator for distillation and recovery of the target component includes: The mother liquor in the distillation system is heated by the flash steam and the external steam, causing the ammonia, carbon dioxide and water vapor in the mother liquor to volatilize, while the less volatile components are deposited, thus separating the components with different volatility and recycling them separately.

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