Concentration and purification process based on pervaporation membrane

Abstract

The invention belongs to the technical field of concentration and purification, and discloses a concentration and purification process based on a pervaporation membrane, which comprises the following steps: S1, conveying raw materials; s2, heat exchange preheating; s3, carrying out secondary preheating; s4, pervaporation membrane separation; s5, collecting and outputting a concentrated solution; and S6, performing permeation side treatment. The process disclosed by the invention can accurately protect thermosensitive active ingredients, is efficient and energy-saving, saves the production cost, and is widely applicable to complex feed liquid, such as traditional Chinese medicinal materials: efficient dehydration / dealcoholization is performed while active ingredients (such as volatile oil) are retained; the to-be-concentrated solution is a concentrated product (such as lactic acid and antibiotics), and high-temperature denaturation is avoided; food and beverage: fruit juice is concentrated at low temperature to maintain flavor.

Description

Technical Field

[0001] The present invention belongs to the technical field of concentration and purification, and specifically relates to a concentration and purification process based on pervaporation membranes. Background Art

[0002] Concentration and purification technologies, as a key process flow, are widely used in multiple fields. Its basic principle is to separate and purify the useful components in a mixture through physical or chemical methods to achieve the purpose of concentration or purification. These technologies not only play an important role in traditional industries such as chemical engineering, pharmaceuticals, and food, but also show broad application prospects in emerging fields such as new energy and environmental protection.

[0003] Pain points of traditional concentration and purification processes:

[0004] Destruction of heat-sensitive components: Traditional evaporation concentration (such as multi-effect evaporation, MVR) requires high temperatures (above 100°C), resulting in the denaturation and inactivation of volatile components (such as essential oils, terpenoids), enzymes, and some proteins in traditional Chinese medicines.

[0005] High energy consumption and low efficiency: The evaporation process relies on a large amount of steam, and the energy consumption surges when dealing with high-viscosity liquids (for example, the energy consumption for concentrating polysaccharide medicinal liquids reaches 200 - 300 kWh / ton).

[0006] Difficulty in solvent recovery: The traditional recovery of ethanol in ethanol extracts requires multiple condensations in a distillation column, with high energy consumption and large fluctuations in purity (recovery rate ≤ 85%). Summary of the Invention

[0007] To overcome the above technical problems, the present invention provides a concentration and purification process based on pervaporation membranes.

[0008] The present invention adopts the following technical solutions:

[0009] The concentration and purification process based on pervaporation membranes includes the following steps:

[0010] S1. Raw material transportation

[0011] Use a raw material pump to pump the liquid to be concentrated from the storage tank to the pretreatment section to ensure continuous feeding, and use a filter screen to initially block suspended particles;

[0012] S2. Heat exchange preheating

[0013] Through a heat exchanger, use the heat of the condensate on the permeate side of the pervaporation membrane to preheat the liquid to be concentrated; the heat released by the condensation of the steam on the permeate side is recovered through the heat exchanger to preheat the liquid to be concentrated entering the membrane module and reduce energy consumption;

[0014] S3. Secondary preheating

[0015] Use a preheater to further preheat the liquid to be concentrated, reduce the viscosity of the liquid to be concentrated, and improve fluidity; circulate hot water in the water bath to the jacket of the preheater to maintain a stable heating temperature;

[0016] S4. Pervaporation membrane separation

[0017] Use a pervaporation membrane module, maintain a low pressure on the permeate side through a vacuum pump to promote the permeation of water / volatile substances through the membrane; during the separation process, water or the target component permeates through the membrane and enters the permeate side, and the concentrated liquid remains on the membrane feed side;

[0018] S5. Collection and output of concentrated liquid

[0019] The concentrated liquid flows into the finished product tank for temporary storage and is transported to the downstream process or packaging by the finished product pump;

[0020] S6. Treatment of the permeate side

[0021] Use a heat exchanger with a condensation function, and the steam on the permeate side condenses into a liquid (such as water) in the heat exchanger, and the condensate can be recycled or discharged.

[0022] Preferably, a vacuum pump or a carrier gas system needs to be configured on the permeate side to maintain a low pressure to promote separation.

[0023] Preferably, the preheating temperature range is 40 - 85°C:

[0024] Low-temperature mode: 40 - 50°C, suitable for heat-sensitive components, such as volatile substances in traditional Chinese medicine and some enzymes;

[0025] Medium-temperature mode: 50 - 70°C, for the concentration of conventional fermentation broth and polysaccharide-containing medicinal liquids;

[0026] High-temperature mode: 70 - 85°C, for high-viscosity medicinal liquids or scenarios requiring rapid dehydration;

[0027] Control method: Adjust the preheating temperature in stages through the water bath, and flexibly match the target temperature by combining secondary heating with the heat exchanger.

[0028] Preferably, before the high-solid-content medicinal liquid enters the membrane module, it is heated to above 70°C through the preheater to reduce the viscosity and reduce the risk of membrane blockage.

[0029] Preferably, for the medicinal liquid extracted with alcohol, a solvent-resistant pervaporation membrane is selected, and ethanol vapor is recovered through the heat exchanger.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] 1. Precise protection of heat-sensitive active ingredients

[0032] Low-temperature mode (40 - 50°C): The retention rate of volatile oils in traditional Chinese medicine is ≥95% (only 70 - 80% in traditional evaporation), and the loss rate of enzyme activity is <5%;

[0033] Stepwise temperature control design: The temperature is increased in stages through a water bath (such as 50°C → 65°C → 80°C) to avoid component degradation caused by sudden temperature changes;

[0034] 2. High efficiency, energy saving and cost advantages

[0035] Waste heat recovery: The condensate on the permeate side (60 - 80°C) preheats the feed liquid through a heat exchanger, reducing the energy consumption of the water bath by ≥60%;

[0036] Low vacuum energy consumption: A dry vacuum pump (ultimate vacuum ≤ 1 kPa) is 50 - 70% more energy - saving than a traditional steam jet pump;

[0037] Efficient ethanol recovery: Solvent - resistant membrane + two - stage condensation (recovery rate ≥ 90%), reducing the energy consumption by 40% compared with the distillation method;

[0038] 3. Wide adaptation to complex feed liquids

[0039] Treatment of high - viscosity liquids: Preheating at 70 - 85°C reduces the viscosity to ≤200 cP, and the membrane flux is maintained at 3.5 Kg / (m 2 ·h) (the flux of traditional membrane separation decays to less than 0.5 under the same viscosity);

[0040] Anti - clogging for high solid content: Pretreatment is carried out through a pretreatment device to meet the quality requirements for feeding into the equipment;

[0041] Solvent tolerance: When treating a 30% ethanol medicinal solution with a zeolite membrane, the membrane life is ≥12 months (only 3 - 6 months for ordinary organic membranes). Specific implementation mode

[0042] The embodiments of the present invention are described in detail below. Unless otherwise specified, the raw materials and equipment used can be purchased from the market or are commonly used in the art. The methods in the embodiments, unless otherwise specified, are conventional methods in the art. The embodiments described below are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0043] 1. Raw material transportation

[0044] Equipment: Raw material pump (corrosion - resistant material), storage tank, filter screen (mesh number selected according to the size of suspended particles)

[0045] Operation:

[0046] The liquid to be concentrated in the storage tank is continuously transported to the pretreatment section by the raw material pump, and the filter screen intercepts suspended particles ≥5 μm to ensure the cleanliness of the membrane module feed.

[0047] 2. Pre - heating and temperature control

[0048] Equipment: Preheater (jacketed type), water bath (multi-stage temperature control), plate heat exchanger

[0049] Temperature mode:

[0050] Low temperature mode (40 - 50°C): Suitable for heat-sensitive substances such as volatile components and enzymes in Chinese herbal medicines. Single-stage heating of the water bath.

[0051] Medium temperature mode (50 - 70°C): Conventional fermentation broth, polysaccharide-containing medicinal liquids. The water bath heats up in two stages (e.g., 50°C → 65°C).

[0052] High temperature mode (70 - 85°C): High-viscosity medicinal liquids (such as those containing colloids and polysaccharides). The heat exchanger + water bath are used for combined heating to the target temperature.

[0053] Heat recovery:

[0054] The condensate on the permeate side (60 - 80°C) exchanges heat with the feed liquid in a countercurrent manner through the heat exchanger, recovering ≥60% of the heat energy, preliminarily preheating the liquid to be concentrated, and complementing the subsequent water bath preheating.

[0055] 3. Membrane separation section

[0056] Core components:

[0057] Pervaporation membrane:

[0058] Conventional feed liquid: Inorganic pervaporation membrane is selected;

[0059] Alcohol extract: Solvent-resistant molecular sieve membrane (such as NaA zeolite membrane).

[0060] Vacuum system: Dry vacuum pump (ultimate vacuum degree ≤1 kPa) or carrier gas (nitrogen) purge to maintain a low-pressure environment on the permeate side.

[0061] Operating parameters:

[0062] Membrane surface flow rate: 0.5 - 2.0 m / s to prevent concentration polarization;

[0063] Transmembrane pressure difference: 0.1 - 0.5 MPa, adjusted according to the characteristics of the feed liquid;

[0064] Ethanol recovery rate: ≥90% (in the case of alcohol extract, the ethanol vapor on the permeate side is condensed and recycled).

[0065] 4. Concentrate treatment

[0066] Equipment: Product tank (with stirring to prevent precipitation), product pump (frequency conversion control)

[0067] Output control:

[0068] The solid content of the concentrated liquid is increased to 20 - 70% (depending on the initial concentration), and after being temporarily stored in the finished product tank, it is pumped to the downstream drying or filling process.

[0069] 5. Permeate side treatment

[0070] Condensation system:

[0071] Two-stage condenser (the first stage is cooled by circulating water to 30 - 40 °C, and the second stage is cryogenically cooled to 4 - 10 °C), ensuring that the steam condensation efficiency ≥ 95%.

[0072] Discharge / reuse:

[0073] Aqueous condensate: Discharge after meeting the COD standard or reuse as process water;

[0074] Organic phase (such as ethanol): Collect and send it to the solvent storage tank for reaction or recycling.

[0075] Optimization measures for special working conditions

[0076] High-solid-content feed liquid:

[0077] Preheat to ≥ 70 °C before entering the membrane to reduce the viscosity to ≤ 200 cP.

[0078] Anti-blocking design for ethanol extract:

[0079] Install a security filter (with a precision of 1 - 5 μm) before the membrane;

[0080] The ethanol vapor on the permeate side is pre-cooled to 60 °C by a heat exchanger and then cryogenically cooled to reduce the membrane thermal stress.

[0081] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to the above embodiments without departing from the principles and purposes of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A pervaporation membrane-based concentration and purification process, characterized in that, It includes the following steps: S1. Raw material transportation Use a raw material pump to pump the liquid to be concentrated from the storage tank to the pretreatment section to ensure continuous feeding, and use a pretreatment device to meet the index requirements for entering the pervaporation membrane; S2. Heat exchange preheating Through a heat exchanger, use the heat of the condensate on the permeate side of the pervaporation membrane to preheat the liquid to be concentrated; the heat released by the condensation of the steam on the permeate side is recovered through the heat exchanger to preheat the liquid to be concentrated entering the membrane module, reducing energy consumption; S3. Secondary preheating Use a preheater to further preheat the liquid to be concentrated, reduce the viscosity of the liquid to be concentrated, and improve fluidity; circulate hot water in the water bath to the jacket of the preheater to maintain a stable heating temperature; S4. Pervaporation membrane separation Use a pervaporation membrane module, and maintain a low pressure on the permeate side through a vacuum pump to promote the permeation of water / volatile substances through the membrane; during the separation process, water or the target component permeates through the membrane and enters the permeate side, while the concentrated liquid remains on the membrane feed side; S5. Collection and output of concentrated liquid The concentrated liquid flows into the finished product tank for temporary storage and is transported to downstream processes or packaging by a finished product pump; S6. Treatment of the permeate side Use a heat exchanger with a condensation function, and the steam on the permeate side condenses into a liquid (such as water) in the heat exchanger, and the condensate can be recycled or discharged.

2. The pervaporation membrane-based concentration and purification process according to claim 1, characterized in that, A vacuum pump or a carrier gas system needs to be configured on the permeate side to maintain a low pressure to promote separation.

3. The pervaporation membrane-based concentration and purification process according to claim 1, characterized in that, The preheating temperature range is 40 - 85°C: Low-temperature mode: 40 - 50°C, suitable for heat-sensitive components, such as volatile substances in traditional Chinese medicines and some enzymes; Medium-temperature mode: 50 - 70°C, for the concentration of conventional fermentation broths and polysaccharide-containing medicinal liquids; High-temperature mode: 70 - 85°C, for high-viscosity medicinal liquids or scenarios requiring rapid dehydration; Control method: Adjust the preheating temperature in stages through a water bath, and flexibly match the target temperature by combining secondary heating with a heat exchanger.

4. The pervaporation membrane-based concentration and purification process according to claim 1, characterized in that, Before the high-solid-content medicinal liquid enters the membrane module, it is heated to above 70°C through a preheater to reduce viscosity and reduce the risk of membrane blockage.

5. The pervaporation membrane-based concentration and purification process according to claim 1, characterized in that, For the ethanol-extracted medicinal liquid, select a solvent-resistant pervaporation membrane and recover ethanol vapor through a heat exchanger.