CN211800726U - Supercritical CO in production of silicon-based aerogel2Dry solvent recovery device - Google Patents

Abstract

The utility model discloses a supercritical CO in silica-based aerogel production₂In the dry solvent recovery device, a first-stage condenser is additionally arranged at a gas phase outlet of a separation kettle, and a solvent dissolved in gas phase carbon dioxide is pre-condensed and separated out, is converged with a liquid phase at the bottom of the separation kettle and jointly enters a downstream for recovering the solvent; simultaneously separating liquid phase downstream of the kettle and designing multiple stagesThe flash tank is used for reducing pressure step by step, and the carbon dioxide gas flashed out is respectively compressed and recovered by compressors of different grades; and a rectifying unit is additionally arranged after the last stage of flash evaporation compression, most of high-purity solvent is recovered, the quality requirement of the raw material is met, the solvent can be directly recycled as the raw material, and only a few parts are discharged along with the high boiling point of the rectified heavy component. The device is through carrying out condensation separation solvent with the separation cauldron gaseous phase, and separation cauldron liquid phase solvent carries out multistage flash distillation compression, and the rectification at last has realized the high purity of solvent, high quality, and high yield is retrieved, also makes compressor throughput more reasonable accurate simultaneously, reaches the energy consumption and practices thrift, reduces production investment cost's purpose. And reduces the discharge of waste water and realizes environmental protection.

Description

Supercritical CO in production of silicon-based aerogel2Dry solvent recovery device

Technical Field

The utility model relates to a supercritical CO₂And (4) a dried solvent recovery device.

Background

In the preparation of silicon-based aerogel, the general flow of the currently known supercritical drying process is shown in fig. 1: liquid carbon dioxide is stored in an intermediate storage tank 1 (4-7 MPa), is pressurized by a pressurizing pump 2 to reach the process required pressure (8-30 MPa), is heated to the required temperature (31-80 ℃) by a heater 3 to reach the supercritical state, is introduced into an aerogel supercritical extraction kettle 4, and aerogel felts fully soaked by a solvent are placed in the kettle in advance. Supercritical carbon dioxide fully contacts with the aerogel felt to replace and fully occupy all gaps of the aerogel, then supercritical carbon dioxide fluid with a solvent dissolved flows out of the extraction kettle, the pressure of the supercritical carbon dioxide fluid is reduced to 4-7 MPa through a first pressure reducing valve 5, the carbon dioxide is separated from a supercritical state and is converted into a gas state, and the solvent which is still in a liquid state enters a separation kettle 6 in a form of a mixture. The solvent rapidly desorbs from the gaseous carbon dioxide due to its rapid decrease in solubility in the gaseous carbon dioxide and is stripped off, and finally discharged from the bottom of the separation tank 6. And after the gaseous carbon dioxide is detached from the solvent and rises, the gaseous carbon dioxide escapes from the top of the separation kettle 6, is condensed to 10-25 ℃ by the secondary condenser 7, is converted into liquid carbon dioxide again and enters the intermediate storage tank 1, and the primary circulation is completed. The solvent liquid discharged from the bottom of the separation kettle 6 is decompressed to 1.5-4 MPa by a second pressure reducing valve 21 and then enters a flash tank 19, the carbon dioxide gas flashed out is compressed to 4-7 MPa by a compressor 20 and then converges into the gas discharged from the top of the separation kettle, and the gas is condensed into a liquid phase by a secondary condenser 7 and then enters a carbon dioxide intermediate storage tank 1. The waste solvent discharged from the bottom of flash tank can be converted into fresh solvent according to a certain proportion.

In the production process of the silicon-based aerogel, carbon dioxide and a solvent cannot be completely separated when gas-liquid equilibrium is achieved in a separation kettle, a certain amount of carbon dioxide is bound to be carried in the solvent discharged from the bottom of the separation kettle, and a certain amount of solvent is bound to be carried in carbon dioxide gas escaping from the top of the separation kettle. If the solvent carried in the top carbon dioxide gas cannot be removed in time, accumulation can be formed in the carbon dioxide drying system after multiple cycles, so that the drying time is prolonged, more solvent residues exist in the obtained aerogel, and the property of the product aerogel felt is unstable. Meanwhile, in the separation process, the solvent returns to the drying system along with the carbon dioxide, so that the solvent loss is increased after multiple cycles, and the fresh solvent needs to be supplemented periodically during the preparation of the aerogel, so that the input of the raw material cost is increased. And similarly, the solvent discharged from the separation kettle also carries a certain amount of carbon dioxide, and the solvent escapes from the top of the flash tank after being decompressed again and returns to the system after being recompressed. The problems with this process are: if the flash pressure is lower, although the separation of the carbon dioxide and the solvent is more thorough, the operation of recompressing and pressurizing a large amount of carbon dioxide gas from high pressure to low pressure and then returning the carbon dioxide gas to the high pressure can cause overlarge treatment capacity of the compressor, not only waste energy, but also increase the production and manufacturing difficulty of equipment, improve the equipment investment and increase the cost. And if the flash pressure is higher, the amount of carbon dioxide remaining in the solvent is increased, the carbon dioxide is discharged along with the waste solvent, and the carbon dioxide is accumulated in multiple batches of operation, so that a large amount of carbon dioxide raw material loss is caused, and the production raw material cost is increased.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a supercritical CO in silica-based aerogel production₂The dry solvent recovery device greatly reduces the energy consumption and the equipment manufacturing and processing difficulty, simultaneously greatly reduces the raw material consumption, saves the cost, reduces the wastewater discharge amount, and is more environment-friendly.

The technical scheme of the utility model is that: production of silicon-based aerogelMedium supercritical CO₂Dry solvent recovery unit, characterized by: a first-stage condenser is additionally arranged at a gas phase outlet of the separation kettle, a solvent dissolved in gas phase carbon dioxide is pre-condensed and separated out, and is converged with a liquid phase at the bottom of the separation kettle and jointly enters a downstream for recovering the solvent; meanwhile, a multi-stage flash tank is designed at the downstream of the liquid phase of the separation kettle, the pressure is reduced step by step, and the carbon dioxide gas flashed off is respectively compressed and recovered by compressors of different stages; and a rectifying unit is additionally arranged after the last stage of flash evaporation compression, most of high-purity solvent is recovered, and only a few of high-purity solvent is discharged along with the high boiling of the rectified heavy components.

The utility model discloses the technical scheme who adopts mainly has three big innovation points: firstly, a first-stage condenser is additionally arranged at a gas phase outlet of a separation kettle, a solvent dissolved in gas phase carbon dioxide is pre-condensed and separated out, and is converged with a liquid phase at the bottom of the separation kettle and jointly enters a downstream for recovering the solvent; secondly, a multi-stage flash tank is designed at the downstream of the liquid phase of the separation kettle, so that the pressure is reduced step by step and the solvent is recovered, and the energy consumption and the equipment manufacturing and processing difficulty are greatly reduced; and a rectification operation unit is additionally arranged after the last stage of flash evaporation recovery operation of the device, most of high-purity solvent is recovered, only a few parts of high-boiling discharge along with the rectification heavy components is realized, the raw material consumption is greatly reduced, the cost is saved, the wastewater discharge amount is reduced, and the device is more environment-friendly.

Drawings

FIG. 1 is a diagram of supercritical CO in the production of conventional silicon-based aerogels₂Schematic diagram of the drying apparatus.

FIG. 2 shows the supercritical CO in the production of silica-based aerogel₂Schematic diagram of the drying and recycling device.

The reference numbers illustrate: the device comprises an intermediate storage tank 1, a booster pump 2, a heater 3, a supercritical extraction kettle 4, a first pressure reducing valve 5, a separation kettle 6, a second-stage condenser 7, a first-stage pressure reducing valve 8, a second-stage pressure reducing valve 9, a third-stage pressure reducing valve 10, a first-stage flash tank 11, a second-stage flash tank 12, a third-stage flash tank 13, a rectifying tower 14, a first-stage compressor 15, a second-stage compressor 16, a third-stage compressor 17, a first-stage condenser 18, a flash tank 19, a compressor 20 and a.

Detailed Description

The utility model discloses a concrete implementation embodies in the tripartite: firstly, a first-stage condenser 18 is additionally arranged at a gas phase outlet of the separation kettle, so that the solvent is fully condensed and is recovered by flash distillation and rectification at the downstream. And secondly, multistage flash compression is arranged at the downstream of the liquid phase of the separation kettle, and the flash pressure is reasonably selected and controlled to fully separate the solvent and the carbon dioxide. And thirdly, adding a rectifying unit to separate the solvent from the heavy components and recycling the solvent to obtain the high-purity solvent.

The temperature of a first-stage condenser additionally arranged at a gas phase outlet of the separation kettle is selected after calculation and comparison for multiple times, more solvents can be condensed at the current temperature, more carbon dioxide cannot be condensed together with the solvents, and 24-40 ℃ is recommended. At the temperature, a large amount of solvent carried in a carbon dioxide gas phase is firstly condensed, the condensed solvent and a separation kettle liquid phase are converged and then subjected to downstream flash evaporation, the solvent is recovered, meanwhile, the solvent is stripped out through a primary condenser 18, purified gas-phase carbon dioxide is further obtained, the purified gas-phase carbon dioxide is condensed into a liquid phase through a secondary condenser 7 and then returns to an intermediate storage tank 1 for storage, the temperature of the secondary condenser 7 is set by comprehensively considering the critical temperature of the carbon dioxide and the stable pressure of the system, and 5-23 ℃ is recommended to be selected. The purity of the carbon dioxide returned to the system is improved, the duration and the efficiency of the drying process are ensured, more solvents are stripped and decomposed from the gaseous carbon dioxide, the recovery of more solvents is realized, the consumption of raw materials is reduced, and the production cost is also reduced.

The supercritical carbon dioxide fluid in which a large amount of solvent is dissolved, which is discharged from the drying kettle, is decompressed, the supercritical carbon dioxide is converted into a gaseous state, and the solvent enters the separation kettle 6 in the form of a gas-liquid mixture. After the gas-liquid equilibrium is reached in the separation vessel, the solvent with a portion of the carbon dioxide dissolved therein is discharged from the bottom of the separation vessel 6 in the form of a liquid phase. The original process technology is that a flash tank 19 is arranged at the bottom of a separation kettle 6, and the gas phase flashed off is compressed and recovered by a compressor 20. The liquid phase is directly discharged out of the system. When the flash evaporation pressure is set to be high, the gas-liquid phase separation effect is very little, a large amount of carbon dioxide gas is discharged along with the solvent, and the entrainment amount of the solvent in the flash evaporated carbon dioxide gas is high, so that the dual raw material waste of the carbon dioxide and the solvent is caused. When the flash pressure is low, a large amount of carbon dioxide gas can be separated by flash evaporation, but for the gas phase, a large amount of gas is instantly decompressed to low pressure from high pressure once, and is repeatedly compressed to high pressure at once, so that the huge gas amount needs to be processed by the pressure reducing valve and the compressor, and the equipment model selection and the cost are passively raised. In addition, the high-pressure gas flash evaporation needs to consume a large amount of heat energy, so that the phenomenon of freezing and blocking of the pipeline can be caused, and then in order to compress a large amount of gas, the compressor 20 needs to provide a large amount of heat energy to do work greatly, so that unnecessary energy is wasted repeatedly.

This technical scheme has tertiary flash tank in the design of 6 low reaches of separation cauldron: first-level flash tank 11, second grade flash tank 12 and tertiary flash tank 13 reduce pressure step by step, and the carbon dioxide gas that flashes off is through different grade compressors: the first-stage compressor 15, the second-stage compressor 16 and the third-stage compressor 17 are compressed and recovered respectively. Not only reduces the equipment model selection manufacturing difficulty, but also distributes the treatment gas quantity of the compressor step by step and reasonably splits the compression ratio due to the adoption of the step compression, so that the energy consumption in the solvent recovery process is greatly reduced, and the energy utilization rate is greatly improved. In addition, the staged flash evaporation compression process adopted by the technical scheme enables the flash evaporation pressure of the last stage to be reasonably selected and set, so that the high-efficiency separation of the carbon dioxide gas and the solvent is realized, and the problems of complex equipment manufacture, increased investment, large energy consumption waste and the like caused by overlarge compression ratio of the compressor and excessive gas treatment amount due to too low flash evaporation pressure are thoroughly avoided.

Generally, the solvent discharged finally in production is large in impurity amount due to the fact that the solvent contains high-boiling-point substances such as gel, excessive reactants and the like, and therefore the proportion of replacing the fresh solvent is often greatly reduced. According to the technical scheme, a rectification unit is additionally arranged after three-stage flash compression, the rectification tower 14 is used for efficiently rectifying and purifying the recovered solvent, the high-purity solvent is recovered, the raw material quality requirement is met, and the high-purity solvent can be directly recycled as the raw material. If the operation is carried out in place, the outsourcing amount of the solvent is greatly reduced, the investment cost is reduced, and the income is increased.

According to the technical scheme, the first-stage condenser 18 is additionally arranged, the solvent carried in the carbon dioxide is fully condensed and recovered before the carbon dioxide returns to the intermediate storage tank 1, so that the solvent enters a downstream flash separation unit and is finally recovered through rectification. Secondly, this technical scheme utilizes multistage flash distillation decompression, and multiple fractionation solvent and carbon dioxide have realized the high-efficient recovery of solvent, simultaneously, compress step by step to each grade of recovery gaseous phase after reducing pressure step by step again, and furthest has practiced thrift the compressor power consumption. The innovative point ensures the separation effect of the solvent and the carbon dioxide, and simultaneously reduces the investment of compressor equipment and creates more benefits by comprehensively and reasonably utilizing energy. Finally, the technical scheme ensures the quality and yield of solvent recovery in supercritical drying production by additionally arranging a rectification unit and stripping and rectifying the solvent from the rectification unit by utilizing the difference of relative volatility of the solvent and the high-boiling-point substances. Greatly reduces the raw material investment, saves the cost and creates the income.

Claims (1)

1. Supercritical CO in production of silicon-based aerogel₂Dry solvent recovery unit, characterized by: a first-stage condenser is additionally arranged at a gas phase outlet of the separation kettle, a solvent dissolved in gas phase carbon dioxide is pre-condensed and separated out, and is converged with a liquid phase at the bottom of the separation kettle and jointly enters a downstream for recovering the solvent; meanwhile, a multi-stage flash tank is designed at the downstream of the liquid phase of the separation kettle, the pressure is reduced step by step, and the carbon dioxide gas flashed off is respectively compressed and recovered by compressors of different stages; and a rectifying unit is additionally arranged after the last stage of flash evaporation compression, most of high-purity solvent is recovered, and only a small part is discharged along with the high boiling of the rectified heavy components.

Images