Production system and production method for preparing biodiesel by high-acid-value grease enzyme method

Abstract

The invention discloses a production system and a production method for preparing biodiesel by using a high-acid-value grease enzyme method, and belongs to the technical field of resource recycling. Comprising a reaction and preliminary separation section and a glycerin concentration section, the reaction and preliminary separation section comprises at least three stages of enzyme reactors which are sequentially connected in series, and the enzyme reactors are used for carrying out multi-stage continuous esterification reaction on high-acid-value oil and methanol under the catalysis of biological enzyme; each stage of enzyme reactor is provided with an external circulation cooling loop which comprises an enzyme reaction circulating pump and an enzyme reaction cooler; the outlet of the last-stage enzyme reactor is connected to a glycerol settling tank and is used for settling and separating the reaction mixture, the light phase of the glycerol settling tank is mixed oil and enters a mixed oil tank, and the heavy phase of the glycerol settling tank is dilute glycerol and enters a glycerol concentration section. According to the invention, the synthesis process of the biodiesel is simplified, the conversion rate of fatty acid methyl ester is improved, the investment cost of the biodiesel is reduced, the operation risk and the corrosion to equipment are reduced, and the energy consumption and the production cost are reduced.

Description

Technical Field

[0001] This invention relates to biodiesel, and more particularly to a production system for producing biodiesel from high-acid-value oils using an enzymatic process. This invention also relates to a production method for producing biodiesel from high-acid-value oils using an enzymatic process, belonging to the field of resource recycling technology. Background Technology

[0002] Biodiesel refers to fatty acid methyl esters formed by the conversion of vegetable oils (such as rapeseed oil, soybean oil, peanut oil, corn oil, cottonseed oil, etc.), animal oils (such as fish oil, lard, tallow, mutton tallow, etc.), and high-acid-value oils (such as palm fatty acid distillates, acidified palm oil, acidified soybean oil, etc.) with methanol. Biodiesel is a typical "green energy" source, characterized by good environmental performance, good engine starting performance, good fuel performance, and a wide range of renewable raw material sources. Vigorously developing biodiesel is of significant strategic importance for sustainable economic development, promoting energy substitution, reducing environmental pressure, and controlling urban air pollution.

[0003] Currently, high-acid-value oils are a crucial raw material for biodiesel production, enabling the reuse of waste oil. Compared to high-quality animal and vegetable oils, the process for producing hydrogen biodiesel from high-acid-value oils is very complex and requires significant investment. It typically involves three steps: first, reducing the acidity of the high-acid-value oil to below 3%; second, using chemical alkali refining or physical deacidification to reduce the fatty acid content from 3% to below 0.2%; and third, using an alkaline catalyst to catalyze the synthesis of biodiesel from neutral oils.

[0004] There are currently two main methods for reducing the acid value of high-acid-value oils. The first method uses strong acid-catalyzed esterification. Strong acids are typically concentrated sulfuric acid or p-toluenesulfonic acid, both highly corrosive chemicals, requiring ceramic or super duplex stainless steel reactors. The reaction temperature is controlled at 105-115℃ to continuously remove water generated during esterification. However, because methanol has a lower boiling point than water, a large amount of methanol vaporizes during the reaction and enters the condenser along with the water. Therefore, acid-catalyzed esterification carries risks such as high corrosivity, high operational hazards, and high energy consumption. The second method for reducing the acid value of high-acid-value oils is glycerol esterification. This process avoids the use of catalysts, but the reaction temperature is high, typically controlled at 200-220℃. This process requires industrial glycerol with a purity of over 95%, resulting in high production costs. Furthermore, similar to esterification, the water generated during the reaction needs to be continuously evaporated and removed. During this process, a large amount of glycerol also vaporizes under vacuum, leading to high energy consumption.

[0005] In recent years, patents related to the enzymatic production of biodiesel have also been published. Chinese invention patent application CN113846128A discloses a process flow for the enzymatic production of biodiesel from high-acid-value oils, specifically including crude oil metering, liquid enzyme reaction, three-phase separation, and crude methanol purification. This technical solution has certain limitations. For example, directly recycling the methanol produced during the purification of crude methyl ester into the liquid enzyme reaction fails to remove the water generated during esterification, leading to an increasing amount of water in the system, ultimately preventing the reaction from proceeding and resulting in a product that does not meet biodiesel standards. Furthermore, there is no recovery device for the methanol separated during the purification of crude glycerol, resulting in high methanol consumption. More importantly, this method can only guarantee an acid value below 10 after the reaction, requiring the use of large amounts of alkali solution for neutralization of these fatty acids in subsequent alkali refining, resulting in a biodiesel yield of only about 90%.

[0006] Chinese invention patent application CN115287310A discloses a "process for producing biodiesel from high-acid-value oils using an enzymatic method," which includes the following steps: methanol gas and crude oil are fully reacted in a solid-enzyme reactor to obtain a methyl ester mixture; if the methyl ester in the mixture passes the test, it is pumped by a methyl ester discharge pump to a methyl ester precipitation zone for further purification to produce biodiesel; if it fails the test, it is returned to the crude oil metering tank for re-reaction. This technical solution has certain limitations, such as: the solid-enzyme reaction uses a fixed-bed reactor, resulting in high initial investment costs; the process has higher requirements for raw materials, and high impurity content in the raw materials can easily lead to enzyme blockage and inactivation throughout the reactor; the process requires a Roots blower to compress methanol gas, which is flammable and explosive, posing a high operational risk; furthermore, the biodiesel yield is only about 90%, requiring subsequent biodiesel distillation to obtain qualified biodiesel. Summary of the Invention

[0007] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, and such simplifications or omissions should not be construed as limiting the scope of the invention.

[0008] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0009] The primary objective of this invention is to overcome the problems existing in the prior art and provide a production system and method for producing biodiesel from high-acid-value oils using an enzymatic process. This simplifies the biodiesel synthesis process, improves the conversion rate of fatty acid methyl esters, reduces biodiesel investment costs, reduces operational hazards and equipment corrosion, and lowers energy consumption and production costs.

[0010] To address the above technical problems, the present invention provides a production system for biodiesel production from high-acid-value oils using an enzymatic process, comprising a reaction and preliminary separation section and a glycerol concentration section. The reaction and preliminary separation section includes at least three enzyme reactors connected in series for a multi-stage continuous esterification reaction of high-acid-value oils with methanol under the catalysis of bio-enzymes. Each enzyme reactor is equipped with an external circulation cooling loop, including an enzyme reaction circulation pump and an enzyme reaction cooler. The outlet of the final enzyme reactor is connected to a glycerol settling tank for settling and separating the reaction mixture. The light phase of the glycerol settling tank, consisting of mixed oil, enters the mixed oil tank, while the heavy phase, consisting of dilute glycerol, enters the glycerol concentration section.

[0011] Furthermore, the reaction and preliminary separation section includes a four-stage enzyme reactor. The bottom circulation outlet of each enzyme reactor and the outlet of the methanol supply pipe are connected to the hot-side inlet of the enzyme reactor cooler via a circulating pump of the same stage. The hot-side outlet of the enzyme reactor cooler is connected to the circulating spray pipe in the middle of the enzyme reactor. The outlet of the enzyme solution supply pipe is connected to the inlet of the circulating spray pipe in the middle of each enzyme reactor. The outlet of the high acid value oil inlet pipe is connected to the inlet of the first-stage enzyme reactor circulating pump. The bottom outlet of the first-stage enzyme reactor is connected to the upper feed inlet of the second-stage enzyme reactor. The bottom outlet of the second-stage enzyme reactor is connected to the upper feed inlet of the third-stage enzyme reactor. The bottom outlet of the third-stage enzyme reactor is connected to the upper feed inlet of the fourth-stage enzyme reactor.

[0012] Furthermore, the inner cavity of the glycerol settling tank is provided with an overflow partition plate extending from the bottom upward to divide the inner cavity space into a light phase side and a heavy phase side, and the inlet of the glycerol settling tank is located above the heavy phase side.

[0013] Furthermore, the glycerol concentration section includes a glycerol evaporator and a glycerol dryer. A dilute glycerol pump sends the dilute glycerol separated from the heavy phase in the glycerol settling tank to the tube side of the glycerol evaporator for circulating heating and evaporation, and then into the glycerol dryer for further evaporation and separation. The glycerol dryer is equipped with a bottom circulation loop, through which the bottom material is sent to the glycerol evaporator for heating and then returned to the glycerol dryer to concentrate the dilute glycerol into crude glycerol, which is then sent out by the crude glycerol pump through the crude glycerol outlet pipe. The gas phase enters the final condenser.

[0014] Furthermore, it also includes a methyl ester neutralization and desoaping section, which includes a mixed oil heater, an alkali-oil mixer, a neutralization reactor, and a desoaping centrifuge. The mixed oil extraction pump sends the mixed oil from the mixed oil tank into the tube side of the mixed oil heater for heating, and then into the alkali-oil mixer. On the other hand, the outlet of the liquid alkali tank is connected to a liquid alkali pump. The concentrated alkali solution pumped by the liquid alkali pump is mixed and diluted with hot water from the hot water supply pipe in a static mixer, and then also enters the alkali-oil mixer. After the mixed oil and the diluted alkali solution are mixed in the alkali-oil mixer, they enter the neutralization reactor for reaction, and then are transported by the desoaping pump to the desoaping centrifuge for centrifugal separation. The separated light phase is the desoaped fatty acid methyl ester, and the heavy phase is the soap residue, which enters the soap residue tank.

[0015] Furthermore, it also includes a soap residue processing section, which includes a circulating jet desolventizer. The inlet pipe of the soap residue conveying pump is connected to the bottom outlet of the soap residue tank, and the outlet pipe of the soap residue conveying pump is connected to the soap residue inlet of the upper nozzle in the inner cavity of the circulating jet desolventizer. The power port of the nozzle is connected to a steam pipe. Under the action of steam, the soap residue is dispersed into snowflakes at the nozzle outlet, and the methanol inside the soap residue is exposed to the gas phase space and vaporized, and discharged from the top of the circulating jet desolventizer. The inlet of the circulating jet pump is connected to the bottom circulating outlet of the circulating jet desolventizer, and the outlet of the circulating jet pump is connected to the lower nozzle in the inner cavity of the circulating jet desolventizer for material circulation spraying. The bottom soap residue discharge outlet of the circulating jet desolventizer is connected to the soap residue outlet pipe via a soap residue extraction pump.

[0016] Furthermore, the soap residue processing section also includes a gas-liquid separator and a soap residue desolventizing condenser. The top gas phase outlet of the circulating jet desolventizing condenser is connected to the gas-liquid separator, the gas phase outlet of the gas-liquid separator is connected to the shell-side inlet of the soap residue desolventizing condenser, its condensate outlet is connected to the methanol-water tank, and the shell-side non-condensable gas outlet of the soap residue desolventizing condenser is connected to the final condenser.

[0017] Furthermore, it also includes a methyl ester washing and drying section, which includes a water mixer, a washing reactor, a washing centrifuge, a methyl ester heater, and a methyl ester drying tower. The light phase outlet, acid pump outlet, and hot water supply pipe outlet of the desoaping centrifuge are all connected to the inlet of the water mixer. The outlet of the water mixer is connected to the upper inlet of the washing reactor. The bottom outlet of the washing reactor is connected to the inlet of the washing centrifuge via a washing pump. The heavy phase outlet of the washing centrifuge is connected to the inlet of the oil-water separator. The light phase outlet of the washing centrifuge is connected to the tube-side inlet of the methyl ester heater. The tube-side outlet of the methyl ester heater is connected to the upper spray nozzle of the methyl ester drying tower.

[0018] Furthermore, the heavy phase outlet of the washing centrifuge is connected to the oil-water separation tank, the oil phase outlet of the oil-water separation tank is connected back to the upper feed inlet of the primary enzyme reactor through a recovery oil pump, and its aqueous phase outlet is connected to the liquid alkali tank and the circulating jet desolventizer through a recovery water pump.

[0019] Furthermore, the bottom outlet of the methyl ester drying tower is connected to the inlet of the methyl ester extraction pump, the outlet of the methyl ester extraction pump is connected to the hot side inlet of the methyl ester cooler, the cold side of the methyl ester cooler is connected to a circulating cooling water pipe, and the hot side outlet of the methyl ester cooler is connected to the methyl ester outlet pipe.

[0020] Furthermore, the vacuum system of the methyl ester drying tower includes a primary steam jet pump and a secondary steam jet pump connected in series. The suction port of the primary steam jet pump is connected to the top of the methyl ester drying tower, and its outlet is connected to the tube-side inlet of the vacuum condenser. The suction port of the secondary steam jet pump is connected to the tube-side outlet of the vacuum condenser, and the outlet of the secondary steam jet pump is connected to the shell side of the final condenser. The tube-side condensate drain of the vacuum condenser is connected to the methanol-water tank through a liquid seal pipe.

[0021] Furthermore, it also includes a methanol recovery and distillation section, which includes a final condenser and a methanol absorption tower. The methanol gas phase generated in each stage of the system enters the shell side of the final condenser for condensation. The tube side of the final condenser is connected to a circulating cooling water pipe. The shell side outlet of the final condenser is connected to the lower inlet of the methanol absorption tower. The middle part of the methanol absorption tower is filled with packing material. The upper spray pipe is connected to a soft water supply pipe. The top of the methanol absorption tower is connected to a gas phase outlet pipe. The bottom outlet of the methanol absorption tower is connected to the inlet of the methanol water tank.

[0022] Furthermore, the bottom outlet of the methanol-water tank is connected in sequence to the cold side of the methanol-water heat exchanger and the methanol-water heater via a methanol-water pump. The cold side outlet of the methanol-water heater is connected to the middle inlet of the methanol distillation column. The wastewater from the bottom of the methanol distillation column is pumped to the hot side of the methanol-water heat exchanger via a bottom pump. After heat recovery, it is sent to the circulating jet desolventizer for reuse. The hot side of the methanol-water heater is connected to a steam pipe.

[0023] Furthermore, the methanol distillation column is equipped with a forced circulation loop at the bottom of the column. The wastewater outlet at the bottom of the methanol distillation column is also connected to the tube-side inlet of the reboiler through a bottom circulation pump, which transports the bottom material to the tube side of the reboiler for heating and then returns it to the bottom of the column. The shell side of the reboiler is connected to a steam pipe.

[0024] Furthermore, the top outlet of the methanol distillation column is connected to the shell-side inlet of the top condenser, the tube side of the top condenser is connected to circulating cooling water, the shell-side exhaust port of the top condenser is connected to the shell side of the final condenser, the shell-side condensate outlet of the top condenser is connected to the inlet of the methanol receiving tank, the bottom outlet of the methanol receiving tank is connected to the inlet of the methanol pump, and the outlet of the methanol pump is connected to the methanol supply pipe and the top reflux port of the methanol distillation column through regulating valves.

[0025] Another objective of this invention is to overcome the problems existing in the prior art and provide a production method for biodiesel from high acid value oils using an enzymatic process. This method simplifies the biodiesel synthesis process, improves the conversion rate of fatty acid methyl esters, reduces biodiesel investment costs, reduces operational hazards and equipment corrosion, and lowers energy consumption and production costs.

[0026] To solve the above technical problems, the present invention provides a method for producing biodiesel from high-acid-value oils using an enzymatic process, employing the aforementioned production system and comprising the following steps:

[0027] S1: High acid value oil, methanol, and biological enzyme solution are fed into a multi-stage tandem enzyme reactor in the reaction and preliminary separation section, where continuous esterification and transesterification reactions are carried out at 35-40℃ to obtain a reaction mixture.

[0028] S2: Separate the reaction mixture obtained in step S1 by sedimentation to obtain a light phase fatty acid methyl ester mixed oil and a heavy phase dilute glycerol;

[0029] S3: The dilute glycerol obtained in step S2 is evaporated and concentrated to obtain crude glycerol;

[0030] S4: After heating the mixed oil obtained in step S2, it is mixed with alkali solution for neutralization reaction, and then centrifuged to obtain desoaped fatty acid methyl ester and soap residue.

[0031] S5: The soap residue obtained in step S4 is subjected to steam desolventizing to remove the methanol contained therein;

[0032] S6: The desoaped fatty acid methyl ester obtained in step S4 is acid-washed and water-washed, then heated and vacuum-dried to obtain a biodiesel product that meets the standards.

[0033] S7: Collect the methanol vapor generated in each step of the system, and recover the methanol after condensation, absorption and distillation and reuse it in the reaction of step S1.

[0034] Furthermore, in step S1, the amount of the added bio-enzyme solution is 0.12%-0.15% of the weight of the high acid value oil, and the enzyme solution is mainly added to the first-stage reactor; the multi-stage tandem enzyme reactor is four-stage, and the material temperature in each stage reactor is controlled at 40℃, so that the final conversion rate reaches more than 98%.

[0035] Furthermore, in step S4, the mixed oil is heated to 60°C and then mixed and neutralized with a 10% concentration of liquid alkali; in step S6, the desoaped fatty acid methyl ester is heated to 120°C and then fed into a methyl ester drying tower, where it is dried under vacuum conditions with an absolute pressure of less than 60 mbar, so that the methanol residue in the fatty acid methyl ester is reduced to less than 50 ppm and the moisture content is reduced to less than 100 ppm.

[0036] Furthermore, in step S5, the soap residue is desolventized using steam at 90°C to reduce the methanol residue in the soap residue to below 100 ppm; in step S7, the wastewater discharged from the bottom of the methanol distillation column is recycled after heat recovery and reused in the soap residue desolventization process of step S5 or the liquid alkali dilution process of step S4 to achieve zero wastewater discharge.

[0037] Compared with the prior art, the advantages or beneficial effects of the present invention include at least the following:

[0038] 1. Using bio-enzymes as catalysts, the esterification reaction of fatty acids and methanol is efficiently catalyzed, avoiding the use of strong acids as catalysts, which greatly reduces the danger of operation and the corrosiveness to equipment. Strong acid catalysis requires the use of super duplex steel as the main material, while the bio-enzyme method only requires carbon steel or 304 stainless steel as the main material, extending the service life of the reactor from 1-2 years to 10-15 years.

[0039] 2. The process reaction conditions of this invention are 35-40℃, which is much lower than the 105-115℃ of concentrated sulfuric acid catalytic esterification and the 200-220℃ of glycerol esterification. Furthermore, there is almost no methanol vaporization during the reaction, and no water generated during the reaction needs to be removed. This invention makes biodiesel production more environmentally friendly. Low-temperature catalysis significantly reduces steam consumption and production costs. For every ton of feedstock processed, steam savings exceed 100 kg. For a biodiesel plant with a daily capacity of 1000 tons, this translates to a daily steam saving of 100 tons. At a steam price of 250 yuan per ton and 300 operating days per year, this amounts to a daily saving of 25,000 yuan and an annual saving of 7.5 million yuan.

[0040] 3. The one-step reaction directly converts fatty acids and triglycerides into fatty acid methyl esters under the action of biological enzymes. It can completely replace the current two-step (strong acid catalytic pre-esterification + strong base catalytic transesterification) or three-step chemical method, greatly simplifying the production process and reducing investment costs. For biodiesel plants with the same output, the equipment investment cost is reduced by more than 50%.

[0041] 4. The reaction is carried out under mild conditions through a four-stage continuous esterification reaction. Each stage employs a pump-driven forced circulation and stirring, enhancing mixing efficiency and increasing the specific surface area of ​​the enzyme solution and high-acid-value oil, thereby increasing the raw material conversion rate from 95% to 98%. Furthermore, an external heat exchanger automatic temperature control system precisely controls the reaction temperature, ensuring reaction stability. Compared to patents CN113846128A and CN115287310A, the biodiesel yield is increased from 90% to 96.5%. A 1000-ton-per-day biodiesel plant can obtain an additional 6.5 tons of biodiesel daily. Based on a biodiesel price of 10,000 yuan per ton and an annual processing time of 300 days, this translates to an additional 19.5 million yuan in profit annually.

[0042] 5. Bio-enzymes and high-acid-value oils enter the reactor at different locations. The high-temperature materials are cooled by a heat exchanger before being mixed with the bio-enzymes, avoiding the deactivation of the enzymes by the high-temperature high-acid-value oils. In addition, the efficient reactor design reduces enzyme consumption from 2-3 kg per ton of material to 1.2-1.5 kg per ton of material. For a 1,000-ton-per-day biodiesel plant, based on an average saving of 0.8 kg of enzyme consumption per ton of raw material processed, an enzyme price of 100 yuan per kg, and an annual processing time of 300 days, the annual production cost savings would be 24 million yuan.

[0043] 6. After the reaction is completed, the mixture is separated by sedimentation. The heavy phase glycerol is concentrated by forced circulation evaporation to obtain crude glycerol with a purity greater than 88% (w / w). This crude glycerol does not contain any salt and can be used as a high-quality raw material for medical glycerol.

[0044] 7. The mixed oil alkali refining process neutralizes the small amount of fatty acids contained in fatty acid methyl esters after the reaction. The mixed oil does not require solvent removal, which reduces equipment investment and steam consumption. Furthermore, the mixed oil alkali refining process helps to improve the separation of soap and fatty acid methyl esters, reduces the content of fatty acid methyl esters in soap, and increases the yield of fatty acid methyl esters. In addition, the mixed oil alkali refining process can control the soap content in fatty acid methyl esters to be below 200 ppm, thus improving the quality of biodiesel.

[0045] 8. The fatty acid methyl esters after alkali refining are washed with water. By controlling the amount of washing acid added, the soap content in the fatty acid methyl esters can be precisely controlled, which can achieve a soap content of less than 2 ppm in biodiesel, which is better than the EU EN14214 standard and greatly enhances the product competitiveness of biodiesel.

[0046] 9. A circulating jet desolventizer is used to remove methanol from the soap residue. The removal efficiency is high, and the residual solvent in the soap residue after desolventizing can be controlled below 100 ppm, which improves the safety of soap residue storage and reduces methanol consumption.

[0047] 10. The existing fatty acid methyl ester drying process has been optimized. The two-stage steam jet pump creates a vacuum of less than 60 mbar. The drying tower uses high-efficiency structured packing, which can control the methanol residue in fatty acid methyl ester to less than 50 ppm, which is far superior to the European standard.

[0048] 11. The efficient methanol distillation process ensures the concentration of methanol and the low residue of methanol in wastewater; the distillation column adopts efficient structured packing, which greatly improves the separation efficiency; the bottom reboiler adopts a forced circulation heat exchanger, which greatly reduces equipment scaling; the top adopts a fully automated reflux design to accurately control the methanol concentration to above 90%.

[0049] 12. All non-condensable gases are collected in the final condenser for condensation and recovery. After the final condenser, water absorption is connected in series. The water absorption tower uses regular packing to minimize the methanol content in the non-condensable gases, reduce environmental pollution, and reduce methanol consumption.

[0050] 13. Wastewater generated during the washing process and wastewater discharged from the methanol distillation tower are reused for the preparation of liquid alkali and the desolvation of soap residue, achieving zero wastewater discharge. Attached Figure Description

[0051] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The drawings are provided for reference and illustration only and are not intended to limit the present invention.

[0052] in:

[0053] Figure 1 This is a flowchart of the production system for producing biodiesel from high-acid-value oils using the enzymatic method of the present invention;

[0054] Figure labels: R1. Primary enzyme reactor; R2. Secondary enzyme reactor; R3. Tertiary enzyme reactor; R4. Quaternary enzyme reactor; R5. Neutralization reactor; R6. Washing reactor;

[0055] C1. Methyl ester drying tower; C2. Methanol distillation tower; C3. Methanol absorption tower;

[0056] E1. Primary enzyme reaction cooler; E2. Secondary enzyme reaction cooler; E3. Tertiary enzyme reaction cooler; E4. Quaternary enzyme reaction cooler; E5. Glycerol evaporator; E6. Mixed oil heater; E7. Methyl ester heater; E8. Methyl ester cooler; E9. Soap residue desolventizing condenser; E10. Methanol-water heat exchanger; E11. Methanol-water heater; E12. Reboiler; E13. Top condenser; E14. Final condenser; E15. Vacuum condenser;

[0057] T1. Glycerin settling tank; T2. Glycerin dryer; T3. Mixed oil tank; T4. Liquid alkali tank; T5. Acid tank; T6. Soap residue tank; T7. Circulating jet desolventizer; T8. Oil-water separator; T9. Methanol-water tank; T10. Methanol receiving tank; T11. Gas-liquid separator;

[0058] P1. Primary enzyme reaction circulating pump; P2. Secondary enzyme reaction circulating pump; P3. Tertiary enzyme reaction circulating pump; P4. Quaternary enzyme reaction circulating pump; P5. Dilute glycerol pump; P6. Glycerol circulating pump; P7. Crude glycerol pump; P8. Light phase extraction pump; P9. Mixed oil extraction pump; P10. Desoaping pump; P11. Liquid alkali pump; P12. Acid pump; P13. Water washing pump; P14. Methyl ester extraction pump; P15. Soap residue transfer pump; P16. Circulating jet pump; P17. Soap residue extraction pump; P18. Recycled oil pump; P19. Recycled water pump; P20. Methanol-water pump; P21. Bottom circulation pump; P22. Bottom extraction pump; P23. Methanol pump;

[0059] V1. First-stage steam jet pump; V2. Second-stage steam jet pump;

[0060] M1. Static mixer; M2. Alkali-oil mixer; M3. Water mixer;

[0061] S1. Desoaping centrifuge; S2. Washing centrifuge;

[0062] G1. High acid value oil inlet pipe; G2. Methanol supply pipe; G3. Enzyme solution supply pipe; G4. Circulating cooling water inlet pipe; G5. Circulating cooling water outlet pipe; G6. Steam pipe; G7. Condensate outlet pipe; G8. Crude glycerol outlet pipe; G9. Soap residue outlet pipe; G10. Methyl ester outlet pipe; G11. Vapor phase outlet pipe; G12. Soft water supply pipe; G13. Hot water supply pipe. Detailed Implementation

[0063] In the following description of the present invention, the terms "upper", "lower", "front", "rear", "left", "right", "inner", "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 present invention and simplifying the description, and do not mean that the device must have a specific orientation.

[0064] To make the technical means, creative features, achieved objectives, and effects of this invention easier to understand, the invention is further described below with reference to specific illustrations. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0066] like Figure 1 As shown, the production system for producing biodiesel from high-acid-value oils using the enzymatic process of the present invention includes:

[0067] 1. Reaction and Preliminary Separation Section

[0068] High-acid-value oil enters the primary enzyme reactor R1 through the high-acid-value oil inlet pipe G1. The methanol required for the reaction is supplied to the primary enzyme reactor R1, secondary enzyme reactor R2, tertiary enzyme reactor R3, and quaternary enzyme reactor R4 through the methanol supply pipe G2. The enzyme solution is mainly added to the primary enzyme reactor R1 through the enzyme solution supply pipe G3.

[0069] Each reactor is equipped with an external circulation cooling loop:

[0070] The material in the primary enzyme reactor R1 is transported by the primary enzyme reaction circulation pump P1, cooled by the tube side of the primary enzyme reaction cooler E1, and then returned to the primary enzyme reactor R1.

[0071] The material in the secondary enzyme reactor R2 is transported by the secondary enzyme reaction circulation pump P2, cooled by the tube side of the secondary enzyme reaction cooler E2, and then returned to the secondary enzyme reactor R2.

[0072] The material in the tertiary enzyme reactor R3 is transported by the tertiary enzyme reaction circulation pump P3, cooled by the tube side of the tertiary enzyme reaction cooler E3, and then returned to the tertiary enzyme reactor R3.

[0073] The material in the fourth-stage enzyme reactor R4 is transported by the fourth-stage enzyme reaction circulation pump P4, cooled by the tube side of the fourth-stage enzyme reaction cooler E4, and then returned to the fourth-stage enzyme reactor R4.

[0074] The shell-side cold side of each of the above-mentioned coolers (primary enzyme reaction cooler E1, secondary enzyme reaction cooler E2, tertiary enzyme reaction cooler E3, and quaternary enzyme reaction cooler E4) is connected in parallel to the circulating cooling water inlet pipe G4 and the circulating cooling water outlet pipe G5.

[0075] The reactants overflow sequentially from the primary enzyme reactor R1 to the secondary enzyme reactor R2, then to the tertiary enzyme reactor R3, and finally exit from the bottom of the quaternary enzyme reactor R4. The reactants are then transported by the quaternary enzyme reaction circulation pump P4 to the glycerol side of the glycerol settling tank T1 for sedimentation separation. After separation, the lighter phase (mainly fatty acid methyl esters) with lower density overflows from the top of the baffle to the lighter phase side of the glycerol settling tank T1, and is subsequently transported by the light phase extraction pump P8 to the mixing oil tank T3.

[0076] 2. Glycerin Concentration Section

[0077] The dilute glycerol in the lower layer of the glycerol settling tank T1 is pumped by dilute glycerol pump P5 to the tube side of the glycerol evaporator E5. Steam is supplied to the shell side of the glycerol evaporator E5 via steam pipe G6 for heating. The heated dilute glycerol then enters the glycerol dryer T2 for devolatilization. Glycerol at the bottom of the glycerol dryer T2 is drawn out by the glycerol circulation pump P6, sent back to the tube side of the glycerol evaporator E5 for heating, and then returned to the glycerol dryer T2, forming a cycle of concentration. The crude glycerol that reaches the required concentration is finally discharged from the system by the crude glycerol pump P7 through the crude glycerol outlet pipe G8.

[0078] 3. Methyl ester neutralization and deshaoling section

[0079] The mixed oil in the mixing tank T3 is pumped by the mixed oil extraction pump P9 to the tube side of the mixed oil heater E6, where steam from the steam pipe G6 heats it in the shell side. The heated mixed oil then enters the alkali-oil mixer M2.

[0080] On the other hand, liquid alkali from liquid alkali tank T4 is pumped by liquid alkali pump P11 and mixed and diluted with hot water from hot water supply pipe G13 in static mixer M1 before entering alkali-oil mixer M2. The oil-alkali mixture enters neutralization reactor R5 for reaction, and is then pumped by desoaping pump P10 to desoaping centrifuge S1 for liquid-solid separation. The separated light phase (desoaped fatty acid methyl esters) enters the subsequent water washing process, while the heavy phase (soap residue) enters soap residue tank T6.

[0081] 4. Soap foot processing section

[0082] Soap residue in soap residue tank T6 is pumped to circulating jet desolventizer T7 by soap residue transfer pump P15, while direct steam from steam pipe G6 is also introduced into circulating jet desolventizer T7. The gas phase at the top of circulating jet desolventizer T7 enters gas-liquid separator T11; the separated droplets return to circulating jet desolventizer T7, while the gas enters the shell side of soap residue desolventizer condenser E9 for condensation. Material at the bottom of circulating jet desolventizer T7 is drawn out by circulating jet pump P16 for circulating spraying to enhance desolventizing. Soap residue after methanol removal is discharged by soap residue extraction pump P17 through soap residue outlet pipe G9.

[0083] 5. Methyl ester washing and drying section

[0084] Desoaped fatty acid methyl esters from the desoaping centrifuge S1 are mixed with citric acid solution from acid tank T5 (transported via acid pump P12) and hot water from hot water supply pipe G13 in water mixer M3. The mixed material then enters the washing reactor R6 and is subsequently pumped by washing pump P13 to the washing centrifuge S2 for oil-water separation. The separated light phase (washed fatty acid methyl esters) enters the tube side of the methyl ester heater E7, where it is heated by steam from steam pipe G6 in the shell side. The heated fatty acid methyl esters then enter the top of the methyl ester drying tower C1 for vacuum drying.

[0085] The separated heavy phase (aqueous phase) enters the oil-water separator T8 for static oil separation. The separated recovered oil is sent back to the primary enzyme reactor R1 by the recovered oil pump P18. The separated recovered water is sent to the liquid alkali tank T4 and the circulating jet desolventizer T7 for reuse by the recovered water pump P19.

[0086] The dried fatty acid methyl ester at the bottom of methyl ester drying tower C1 is extracted by methyl ester extraction pump P14 and sent to the hot side of methyl ester cooler E8 for cooling. The qualified product after cooling is discharged through methyl ester outlet pipe G10. The vacuum in methyl ester drying tower C1 is generated and maintained by primary steam jet pump V1 and secondary steam jet pump V2. The mixed gas from the outlet of primary steam jet pump V1 enters the tube side of vacuum condenser E15, while cooling water from circulating cooling water inlet pipe G4 flows through its shell side. The non-condensable gas discharged from the tube side outlet of vacuum condenser E15, together with the outlet gas from secondary steam jet pump V2, enters the subsequent condensation system.

[0087] 6. Methanol Recovery and Distillation Section

[0088] Methanol gaseous phases generated throughout the system (originating from the tops of primary enzyme reactors R1, R2, R3, and R4, the top of glycerol dryer T2, and the non-condensable gas from the shell-side outlet of soap residue desolvation condenser E9) are collected in the shell side of the final condenser E14 for condensation. The uncondensed tail gas enters the bottom of methanol absorption tower C3, where soft water from soft water supply pipe G12 is sprayed and absorbed at the top of the tower. The absorbed, compliant tail gas is discharged through the gas phase outlet pipe G11.

[0089] All condensate (including the condensate from the final condenser E14 and the methanol-water from the bottom of the methanol absorber C3) is collected in the methanol-water tank T9. This methanol-water is pumped by the methanol-water pump P20, first entering the cold side of the methanol-water heat exchanger E10 for preheating, then entering the cold side of the methanol-water heater E11 for further heating, and finally entering the middle of the methanol distillation column C2.

[0090] The material at the bottom of methanol distillation column C2 is pumped to the tube side of reboiler E12 by bottom circulation pump P21. Steam from steam pipe G6 provides heat in the shell side of reboiler E12, and the heated material returns to the bottom of methanol distillation column C2. Wastewater generated at the bottom is extracted by bottom extraction pump P22, flows through the hot side of methanol-water heat exchanger E10 to recover heat, and then is sent to circulating jet desolvator T7 for reuse as process water. The vapor phase at the top of methanol distillation column C2 enters the shell side of top condenser E13 for condensation, and the condensate flows into methanol receiving tank T10. When the methanol concentration in methanol receiving tank T10 reaches the standard, it is pumped by methanol pump P23 back to primary enzyme reactor R1, secondary enzyme reactor R2, tertiary enzyme reactor R3, and quaternary enzyme reactor R4 for recycling.

[0091] 7. Utilities and Auxiliary Systems

[0092] Steam system: Steam pipe G6 provides heat source for the shell side of glycerol evaporator E5, mixed oil heater E6, methyl ester heater E7, methanol water heater E11, reboiler E12 and circulating jet desolventizer T7. The condensate generated by each device is discharged through condensate outlet pipe G7.

[0093] Cooling water system: The circulating cooling water inlet pipe G4 and the circulating cooling water outlet pipe G5 provide cooling medium for the cold side of equipment such as the primary enzyme reaction cooler E1, the secondary enzyme reaction cooler E2, the tertiary enzyme reaction cooler E3, the quaternary enzyme reaction cooler E4, the methyl ester cooler E8, the tower top condenser E13, the final condenser E14, and the vacuum condenser E15.

[0094] The production process of biodiesel from high-acid-value oils using enzymatic methods according to this invention is as follows:

[0095] High-acid-value oil from the high-acid-value oil inlet pipe G1 enters the primary enzyme reactor R1, and the flow rate of the high-acid-value oil is automatically controlled by a pneumatic regulating valve. Methanol from the methanol supply pipe G2 can enter each stage of the enzyme reactor, and the flow rate into each stage of the enzyme reactor can be automatically controlled by a pneumatic regulating valve. When the liquid level in the primary enzyme reactor R1 reaches 10% (height percentage, the same below), the primary enzyme reaction circulation pump P1 is started to begin circulating mixing and cooling via the primary enzyme reaction cooler E1. The regulating valve on the circulating cooling water inlet pipe G4 is adjusted, and the circulating cooling water enters the cold side inlet of the primary enzyme reaction cooler E1. After flowing out of the cold side outlet, it flows out through the circulating cooling water outlet pipe G5, controlling the medium outlet temperature of the primary enzyme reaction cooler E1 to be 40℃.

[0096] Enzyme solution from enzyme supply pipe G3 can enter each stage of the enzyme reactor, and the flow rate into each stage can be automatically controlled by a pneumatic regulating valve. The enzyme solution enters the first-stage enzyme reactor R1 from the first stage, with an optimal enzyme addition rate of 0.12-0.15%. No further enzyme is added to the second-stage, third-stage, and fourth-stage enzyme reactors R2 and R3, meaning that 1.2-1.5 kg of enzyme solution is consumed per ton of high-acid-value oil processed. Under the catalytic action of the enzyme solution, two chemical reactions occur in each stage of the reactor under a slight positive pressure. The first is esterification, where fatty acids in the high-acid-value oil esterify with methanol to produce fatty acid methyl esters and water. The second is transesterification, where triglycerides in the high-acid-value oil transesterify with methanol to produce fatty acid methyl esters and glycerol.

[0097] When the liquid level in the primary enzyme reactor R1 reaches the overflow height, the primary mixture enters the secondary enzyme reactor R2. When the liquid level in the secondary enzyme reactor R2 reaches 10%, the secondary enzyme reaction circulation pump P2 is started to begin circulation mixing and cooling via the secondary enzyme reaction cooler E2. The regulating valve on the circulating cooling water inlet pipe G4 is adjusted to control the medium outlet temperature of the secondary enzyme reaction cooler E2 to 40℃. Following this procedure, the tertiary enzyme reaction circulation pump P3 of the tertiary enzyme reactor R3 and the quaternary enzyme reaction circulation pump P4 of the quaternary enzyme reactor R4 are started sequentially, and the medium outlet temperatures of the tertiary enzyme reaction coolers E3 and E4 are controlled to 40℃. The conversion rates of the outlet mixtures from the primary enzyme reactor R1, secondary enzyme reactor R2, tertiary enzyme reactor R3, and quaternary enzyme reactor R4 are 60%, 80%, 95%, and 98%, respectively.

[0098] Methanol discharged from the top of the primary enzyme reactor R1, secondary enzyme reactor R2, tertiary enzyme reactor R3, and quaternary enzyme reactor R4 all enter the shell side of the final condenser E14 for condensation.

[0099] When the liquid level in the four-stage enzyme reactor R4 reaches 80%, the outlet regulating valve of the four-stage enzyme reaction circulation pump P4 is opened, and the four-stage mixture is continuously transported into the glycerol side of the glycerol settling tank T1 for settling and separation. Glycerol, which has a higher density, settles downwards, while the lighter phase, fatty acid methyl ester, floats upwards due to its lower density and overflows from the top of the partition to the lighter phase side.

[0100] A sensor for detecting the glycerol level is installed on the glycerol side of the glycerol settling tank T1. When the glycerol level reaches 50%, it is pumped into the tube side of the glycerol evaporator E5 by the dilute glycerol pump P5. Water vapor from the steam pipe G6 enters the shell side of the glycerol evaporator E5 and exchanges heat with the dilute glycerol in the tube side. The condensate discharged from the shell side is discharged back to the boiler room through the condensate outlet pipe G7. After being heated, the glycerol discharged from the tube side of the glycerol evaporator E5 enters the glycerol dryer T2 for volatilization. The water vapor discharged from the top of the glycerol dryer T2 enters the shell side of the final condenser E14 for condensation.

[0101] When the liquid level in the glycerin dryer T2 reaches 20%, start the glycerin circulation pump P6. The glycerin discharged from the bottom of the glycerin dryer T2 will circulate back into the glycerin dryer T2 through the tube side of the glycerin evaporator E5. Adjust the steam regulating valve on the steam pipe G6 to control the outlet temperature of the glycerin dryer T2 to 125℃.

[0102] When the liquid level in glycerin dryer T2 reaches 50%, the crude glycerin pump P7 is started. By adjusting the start-up regulating valve on the crude glycerin outlet pipe G8, the liquid level and temperature in glycerin dryer T2 are maintained. The crude glycerin discharged this time has a concentration of over 88%. Because no acid or alkali is added during the production process, the crude glycerin discharged here does not contain any salt and can be used as a high-quality raw material for medical glycerin.

[0103] When the light phase level in the glycerol settling tank T1 reaches 50%, the light phase extraction pump P8 is started, and fatty acid methyl esters are continuously transported into the mixing tank T3.

[0104] When the liquid level in the mixing oil tank T3 reaches 50%, start the mixing oil extraction pump P9 to send the mixed oil into the tube side of the mixing oil heater E6. The water vapor from the steam pipe G6 enters the shell side of the mixing oil heater E6 and exchanges heat with the mixed oil in the tube side. The condensate discharged from the shell side is discharged through the condensate outlet pipe G7. Adjust the steam regulating valve on the steam pipe G6 to control the tube side outlet temperature of the mixing oil heater E6 to 60℃.

[0105] Add liquid alkali to the liquid alkali tank T4 until the liquid level reaches 80%. Start the liquid alkali pump P11 and control the flow rate of the liquid alkali to the set value via the frequency converter. The liquid alkali and hot water from the hot water supply pipe G13 enter the static mixer M1 for mixing. Adjust the pneumatic regulating valve on the hot water supply pipe G13 to control the hot water flow rate and keep the concentration of liquid alkali entering the static mixer M1 at around 10%.

[0106] The mixed oil flowing out of the E6 tube of the mixed oil heater, together with the liquid alkali mixed in the static mixer M1, enters the alkali-oil mixer M2, ensuring thorough mixing of the mixed oil and liquid alkali. The mixture then enters the neutralization reactor R5 for a neutralization reaction, neutralizing the untreated free fatty acids in the feed oil. When the liquid level in the neutralization reactor R5 reaches 40%, the desoaping pump P10 is activated, and the liquid level in the neutralization reactor R5 is automatically controlled by a frequency converter configured in the desoaping pump P10. The principle of the neutralization reactor is that the liquid alkali reacts with the fatty acids in the mixed oil in an acid-base neutralization reaction, producing sodium fatty acid (soap) and water. After the reaction, the mixture is evenly sent by the desoaping pump P10 to the desoaping centrifuge S1. The desoaping centrifuge S1 is a disc centrifuge with a speed of over 5500 rpm, where fatty acid methyl esters and soap residue are separated based on their different specific gravities. The heavier soap sludge is separated from the heavy phase port of the desoap centrifuge S1 and enters the soap sludge tank T6; the soap content in the light phase of the desoap centrifuge S1 is less than 200 ppm.

[0107] When the soap stock tank T6 reaches 50% level, the soap stock transfer pump P15 is started. The frequency converter configured in the soap stock transfer pump P15 automatically controls the liquid level in the soap stock tank T6. The soap stock is evenly transported to the circulating jet desolventizer T7. Water vapor from the steam pipe G6 also enters the circulating jet desolventizer T7. The regulating valve on the steam pipe G6 is opened. Under the action of the steam, the soap stock is dispersed into a snowflake pattern at the internal nozzle outlet. The methanol inside the soap stock is exposed to the gas phase space and vaporizes. The vaporized methanol enters the gas-liquid separator T11 through the top gas phase pipe. The liquid droplets separated by the gas-liquid separator T11 are discharged from the bottom of the gas-liquid separator T11 and flow back to the circulating jet desolventizer T7 by gravity. The separated gas phase is discharged from the top of the gas-liquid separator T11 and enters the shell side of the soapstock desolventizing condenser E9. The methanol condensate enters the methanol-water tank T9. The non-condensable gas discharged from the shell side outlet of the soapstock desolventizing condenser E9 enters the shell side of the final condenser E14 for condensation.

[0108] When the liquid level in the circulating jet desolventizer T7 reaches 10%, the circulating jet pump P16 at its bottom is started, and the soap residue is drawn back to the middle of the circulating jet desolventizer T7 for circulating spray desolventizing. The internal temperature of the circulating jet desolventizer T7 is controlled at about 90℃ by adjusting the regulating valve on the steam pipe G6.

[0109] When the liquid level of the circulating jet desolventizer T7 reaches 20%, the soap residue extraction pump P17 at its bottom is started, and soap residue with a solubility of less than 100 ppm is evenly transported from the soap residue outlet pipe G9 to the outer tank area.

[0110] Add 36% citric acid to acid tank T5 until the liquid level reaches 80%. Start acid pump P12 and control the flow rate of citric acid to the set value via frequency converter, sending the citric acid into the inlet of water mixer M3. Hot water from hot water supply pipe G13 also enters the inlet of water mixer M3. Adjust the pneumatic regulating valve on hot water supply pipe G13 to control the water washing flow rate to the set value. Fatty acid methyl esters discharged from the light phase outlet of desoap centrifuge S1 are mixed with citric acid and hot water and then enter water mixer M3 for mixing. After being mixed evenly, they enter water washing reactor R6. The mechanism of the water washing reaction is that a small amount of unseparated soap from fatty acid methyl esters undergoes an acid-base neutralization reaction with citric acid to produce fatty acids and water, improving the quality of biodiesel (fatty acid methyl esters) and reducing the soap content in biodiesel to below 2 ppm.

[0111] When the liquid level in the washing reactor R6 reaches 40%, the washing pump P13 is started, and the material is evenly conveyed to the washing centrifuge S2. The washing centrifuge S2 is a disc centrifuge with a rotation speed of over 5500 rpm. Based on the different specific gravities of fatty acid methyl esters and water, they are separated. The heavy phase separated by the washing centrifuge S2 enters the oil-water separator T8 for further separation. The oil phase separated by the oil-water separator T8 is transported to the primary enzyme reactor R1 for recovery via the oil recovery pump P18. The water separated by the oil-water separator T8 is transported to the liquid alkali tank T4 and the circulating jet desolventizer T7 for recovery via the water recovery pump P19, preventing wastewater discharge from the workshop.

[0112] The light phase fatty acid methyl ester separated by the water washing centrifuge S2 enters the tube side of the methyl ester heater E7. The water vapor from the steam pipe G6 enters the shell side of the methyl ester heater E7 and exchanges heat with the fatty acid methyl ester in the tube side. The condensate discharged from the shell side is discharged through the condensate outlet pipe G7. The regulating valve on the steam pipe G6 is adjusted to control the tube side outlet temperature of the methyl ester heater E7 to 120°C. The fatty acid methyl ester heated to 120°C enters the distribution plate at the top of the methyl ester drying tower C1 and is evenly distributed into the packing below for devolatilization.

[0113] Moisture and methanol in fatty acid methyl esters are continuously removed by the suction of the first-stage steam jet pump V1. After mixing with the motive steam from the first-stage steam jet pump, the mixture enters the tube side of the vacuum condenser E15. Circulating cooling water from the inlet pipe G4 enters the shell side of the vacuum condenser E15, and after heat exchange, it is discharged from the outlet pipe G5. The non-condensable gas discharged from the tube side outlet of the vacuum condenser E15 enters the suction port of the second-stage steam jet pump V2. The mixed gas from the outlet of the second-stage steam jet pump V2 enters the shell side of the final condenser E14. The second-stage steam jet pump V2 maintains the system vacuum at below 60 mbar absolute pressure. The water content at the inlet of the methyl ester drying tower C1 is 5000 ppm, and the water content at the outlet is below 100 ppm, far exceeding EU standards. The condensate discharged from the bottom of the tube side of the vacuum condenser E15 is collected in the methanol-water tank T9.

[0114] When the liquid level in fatty acid methyl ester drying tower C1 reaches 40%, the fatty acid methyl ester extraction pump P14 is started, and the fatty acid methyl ester is continuously sent to the hot side of the fatty acid methyl ester cooler E8. The regulating valve on the circulating cooling water inlet pipe G4 is adjusted, and the circulating cooling water enters the cold side inlet of the fatty acid methyl ester cooler E8. After flowing out of the cold side outlet, it flows out through the circulating cooling water outlet pipe G5, controlling the hot side outlet temperature of the fatty acid methyl ester cooler E8, i.e., the medium outlet temperature, to 50℃. The cooled fatty acid methyl ester exhibits all indicators superior to the EU standard EN14214. It enters the external storage tank through the fatty acid methyl ester outlet pipe G10. The indicators are shown in the table below.

[0115]

[0116]

[0117] In this invention, all methanol vapor phase is collected in the shell side of the final condenser E14. Circulating cooling water from the inlet pipe G4 enters the final condenser E14 through the lower tube side inlet and exits through the upper tube side outlet via the circulating cooling water outlet pipe G5. The non-condensable gas discharged from the shell side outlet of the final condenser E14 enters the methanol absorption tower C3 for absorption. The methanol absorption tower C3 is a packed tower. Soft water enters the top of the methanol absorption tower C3 through the soft water supply pipe G12. The flow rate of the soft water is automatically regulated by a pneumatic valve. The qualified vapor phase after collection is discharged through the top of the methanol absorption tower C3 and the vapor phase outlet pipe G11.

[0118] The condensate discharged from the shell side of the final condenser E14 and the methanol-water mixture discharged from the bottom of the methanol absorber C3 flow into the methanol-water tank T9. When the liquid level in the methanol-water tank T9 reaches 30%, the methanol-water pump P20 is started, and the methanol-water is delivered to the cold side of the methanol-water heat exchanger E10, then to the cold side of the methanol-water heater E11, where it is heated to 76°C before entering the middle section of the methanol distillation column C2. Based on the difference in relative volatility between methanol and water, the methanol distillation column C2 concentrates water, which has lower relative volatility, at the bottom of the column, and methanol, which has higher relative volatility, at the top of the column, thus achieving separation between the two.

[0119] When the bottom liquid level of methanol distillation column C2 reaches 20%, the bottom circulation pump P21 is started to pump water into the tube side of reboiler E12. Water vapor from steam pipe G6 enters the shell side of reboiler E12 and exchanges heat with the methanol-water in the tube side. The condensate discharged from the shell side is discharged through condensate outlet pipe G7. The outlet temperature of the tube side of reboiler E12 is controlled at 105℃ by the regulating valve on steam pipe G6 and returns to the bottom of methanol distillation column C2 for circulation.

[0120] When the bottom liquid level of methanol distillation column C2 reaches 50% and the temperature reaches 105℃, the bottom pump P22 is started, and the wastewater is transported into the hot side of methanol-water heat exchanger E10. After preheating the methanol-water on the cold side, it enters the circulating jet desolventizer T7 for circulating desolventizing.

[0121] The vapor phase from the top of methanol distillation column C2 enters the shell side of the overhead condenser E13, and the condensate from the top of the column enters the methanol receiving tank T10. When the liquid level in the methanol receiving tank T10 reaches 40%, the methanol pump P23 is started. Initially, all methanol is refluxed back to the methanol distillation column C2. When the methanol concentration is higher than 90%, the outlet regulating valve begins to pump the methanol into the primary enzyme reactor R1, secondary enzyme reactor R2, tertiary enzyme reactor R3, and quaternary enzyme reactor R4 for recycling.

[0122] The above description is merely a preferred embodiment of the present invention, showing and describing the basic principles, main features, and advantages of the present invention. It is not intended to limit the scope of patent protection of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. In addition to the above embodiments, the present invention may have other implementations without departing from the spirit and scope of the invention. Various changes and modifications to the present invention are possible, and all technical solutions formed by equivalent substitutions or equivalent transformations fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents. Technical features not described in the present invention can be implemented by or using existing technology, and will not be elaborated here.

Claims

1. A production system for producing biodiesel from high-acid-value oils using an enzymatic process, characterized in that, It includes a reaction and preliminary separation section and a glycerol concentration section. The reaction and preliminary separation section includes at least three enzyme reactors connected in series for multi-stage continuous esterification reaction of high acid value oil with methanol under the catalysis of biological enzymes. Each enzyme reactor is equipped with an external circulation cooling loop, including an enzyme reaction circulation pump and an enzyme reaction cooler. The outlet of the final-stage enzyme reactor is connected to a glycerol settling tank (T1) for settling and separating the reaction mixture. The light phase of the glycerol settling tank (T1) is mixed oil, which enters the mixed oil tank (T3), and the heavy phase is dilute glycerol, which enters the glycerol concentration section.

2. The production system for biodiesel from high-acid-value oils using enzymatic methods according to claim 1, characterized in that, The reaction and preliminary separation section includes a four-stage enzyme reactor. The bottom circulation outlet of each enzyme reactor and the outlet of the methanol supply pipe (G2) are connected to the hot side inlet of the enzyme reactor cooler through the same-stage enzyme reaction circulation pump. The hot side outlet of the enzyme reactor cooler is connected to the circulation spray pipe in the middle of the enzyme reactor. The outlet of the enzyme solution supply pipe (G3) is connected to the inlet of the circulation spray pipe in the middle of each enzyme reactor. The outlet of the high acid value oil inlet pipe (G1) is connected to the inlet of the primary enzyme reaction circulation pump (P1). The bottom outlet of the primary enzyme reactor (R1) is connected to the upper feed inlet of the secondary enzyme reactor (R2). The bottom outlet of the secondary enzyme reactor (R2) is connected to the upper feed inlet of the tertiary enzyme reactor (R3). The bottom outlet of the tertiary enzyme reactor (R3) is connected to the upper feed inlet of the quaternary enzyme reactor (R4).

3. The production system for biodiesel from high-acid-value oils using enzymatic methods according to claim 1, characterized in that, The glycerol settling tank (T1) has an overflow partition plate extending from the bottom upwards to divide the inner cavity into a light phase side and a heavy phase side. The inlet of the glycerol settling tank (T1) is located above the heavy phase side.

4. The production system for biodiesel from high-acid-value oils using enzymatic methods according to claim 1, characterized in that, The glycerol concentration section includes a glycerol evaporator (E5) and a glycerol dryer (T2). A dilute glycerol pump (P5) sends the dilute glycerol separated from the heavy phase in the glycerol settling tank (T1) to the tube side of the glycerol evaporator (E5) for circulating heating and evaporation, and then into the glycerol dryer (T2) for further evaporation and separation. The glycerol dryer (T2) is equipped with a bottom circulation loop. The bottom material is sent to the glycerol evaporator (E5) for heating by a glycerol circulation pump (P6) and then returned to the glycerol dryer (T2) to concentrate the dilute glycerol into crude glycerol, which is then sent out by the crude glycerol pump (P7) through the crude glycerol outlet pipe (G8). The gas phase enters the final condenser (E14).

5. The production system for biodiesel from high-acid-value oils using enzymatic methods according to claim 1, characterized in that, It also includes a methyl ester neutralization and desoaping section, which includes a mixed oil heater (E6), an alkali oil mixer (M2), a neutralization reactor (R5), and a desoaping centrifuge (S1). The mixed oil extraction pump (P9) sends the mixed oil in the mixed oil tank (T3) into the tube side of the mixed oil heater (E6) for heating, and then into the alkali oil mixer (M2). On the other hand, the outlet of the liquid alkali tank (T4) is connected to a liquid alkali pump (P11). The concentrated alkali solution delivered by the liquid alkali pump (P11) is mixed and diluted with the hot water from the hot water supply pipe (G13) in the static mixer (M1) and then enters the alkali-oil mixer (M2). After being mixed with dilute alkali solution in an alkali-oil mixer (M2), the mixture enters a neutralization reactor (R5) for reaction. Subsequently, it is transported by a desoaping pump (P10) to a desoaping centrifuge (S1) for centrifugal separation. The separated light phase is the desoaped fatty acid methyl ester, and the heavy phase is the soap residue, which enters the soap residue tank (T6).

6. The production system for biodiesel from high-acid-value oils using enzymatic methods according to claim 1, characterized in that, The system also includes a soap residue processing section, which comprises a circulating jet desolventizer (T7). The inlet pipe of a soap residue transfer pump (P15) is connected to the bottom outlet of a soap residue tank (T6), and the outlet pipe of the pump (P15) is connected to the soap residue inlet of an upper nozzle within the circulating jet desolventizer (T7). The power port of the nozzle is connected to a steam pipe (G6). Under the action of steam, the soap residue is dispersed into a snowflake-like pattern at the nozzle outlet, and the methanol inside the soap residue is... Exposed to the gas phase space and vaporized, it is discharged from the top of the circulating jet desolventizer (T7); the inlet of the circulating jet pump (P16) is connected to the bottom circulating outlet of the circulating jet desolventizer (T7), and the outlet of the circulating jet pump (P16) is connected to the lower nozzle in the inner cavity of the circulating jet desolventizer (T7) for material circulation spraying; the bottom soap foot discharge outlet of the circulating jet desolventizer (T7) is connected to the soap foot outlet pipe (G9) via the soap foot extraction pump (P17).

7. The production system for biodiesel from high-acid-value oils using enzymatic methods according to claim 1, characterized in that, The soap residue processing section also includes a gas-liquid separator (T11) and a soap residue desolventizing condenser (E9). The top gas phase outlet of the circulating jet desolventizer (T7) is connected to the gas-liquid separator (T11), the gas phase outlet of the gas-liquid separator (T11) is connected to the shell-side inlet of the soap residue desolventizing condenser (E9), its condensate outlet is connected to the methanol-water tank (T9), and the shell-side non-condensable gas outlet of the soap residue desolventizing condenser (E9) is connected to the final condenser (E14).

8. The production system for producing biodiesel from high-acid-value oils using enzymatic methods according to claim 5, characterized in that, It also includes a methyl ester washing and drying section, which includes a water mixer (M3), a washing reactor (R6), a washing centrifuge (S2), a methyl ester heater (E7), and a methyl ester drying tower (C1). The light phase outlet, acid pump (P12) outlet, and hot water supply pipe (G13) outlet of the desoaping centrifuge (S1) are all connected to the inlet of the water mixer (M3). The outlet of the water mixer (M3) is connected to the upper inlet of the washing reactor (R6). The bottom outlet of the washing reactor (R6) is connected to the inlet of the washing centrifuge (S2) through the washing pump (P13). The heavy phase outlet of the washing centrifuge (S2) is connected to the inlet of the oil-water separator (T8). The light phase outlet of the washing centrifuge (S2) is connected to the tube-side inlet of the methyl ester heater (E7). The tube-side outlet of the methyl ester heater (E7) is connected to the upper spray port of the methyl ester drying tower (C1).

9. The production system for biodiesel from high-acid-value oils using enzymatic methods according to claim 8, characterized in that, The heavy phase outlet of the washing centrifuge (S2) is connected to the oil-water separator (T8). The oil phase outlet of the oil-water separator (T8) is connected back to the upper feed inlet of the primary enzyme reactor (R1) via a recovery oil pump (P18). Its aqueous phase outlet is connected to the liquid alkali tank (T4) and the circulating jet desolventizer (T7) via a recovery water pump (P19).

10. The production system for biodiesel from high-acid-value oils using enzymatic methods according to claim 8, characterized in that, The bottom outlet of the methyl ester drying tower (C1) is connected to the inlet of the methyl ester extraction pump (P14), the outlet of the methyl ester extraction pump (P14) is connected to the hot side inlet of the methyl ester cooler (E8), the cold side of the methyl ester cooler (E8) is connected to the circulating cooling water pipe, and the hot side outlet of the methyl ester cooler (E8) is connected to the methyl ester outlet pipe (G10).

11. The production system for biodiesel from high-acid-value oils using enzymatic methods according to claim 8, characterized in that, The vacuum system of the methyl ester drying tower (C1) includes a primary steam jet pump (V1) and a secondary steam jet pump (V2) connected in series. The suction port of the primary steam jet pump (V1) is connected to the top of the methyl ester drying tower (C1), and its outlet is connected to the tube-side inlet of the vacuum condenser (E15). The suction port of the secondary steam jet pump (V2) is connected to the tube-side outlet of the vacuum condenser (E15), and the outlet of the secondary steam jet pump (V2) is connected to the shell side of the final condenser (E14). The tube-side condensate drain of the vacuum condenser (E15) is connected to the methanol-water tank (T9) through a liquid seal pipe.

12. The production system for biodiesel from high-acid-value oils using enzymatic methods according to claim 1, characterized in that, It also includes a methanol recovery and distillation section, which includes a final condenser (E14) and a methanol absorption tower (C3). The methanol vapor generated in each stage of the system enters the shell side of the final condenser (E14) for condensation. The tube side of the final condenser (E14) is connected to the circulating cooling water pipe. The shell side outlet of the final condenser (E14) is connected to the lower inlet of the methanol absorption tower (C3). The methanol absorption tower (C3) is filled with packing in the middle. The upper spray pipe is connected to the soft water supply pipe (G12). The top of the methanol absorption tower (C3) is connected to the vapor phase outlet pipe (G11). The bottom outlet of the methanol absorption tower (C3) is connected to the inlet of the methanol water tank (T9).

13. The production system for producing biodiesel from high-acid-value oils using enzymatic methods according to claim 12, characterized in that, The bottom outlet of the methanol water tank (T9) is connected in sequence to the cold side of the methanol water heat exchanger (E10) and the methanol water heater (E11) via the methanol water pump (P20). The cold side outlet of the methanol water heater (E11) is connected to the middle inlet of the methanol distillation column (C2). The wastewater from the bottom of the methanol distillation column (C2) is sent to the hot side of the methanol water heat exchanger (E10) via the bottom extraction pump (P22) to recover heat and then sent to the circulating jet desolventizer (T7) for reuse. The hot side of the methanol water heater (E11) is connected to the steam pipe (G6).

14. The production system for biodiesel from high-acid-value oils using enzymatic methods according to claim 13, characterized in that, The methanol distillation column (C2) is equipped with a forced circulation loop at the bottom. The wastewater outlet at the bottom of the methanol distillation column (C2) is also connected to the tube side inlet of the reboiler (E12) through a bottom circulation pump (P21). The bottom material is transported to the tube side of the reboiler (E12) for heating and then returned to the bottom. The shell side of the reboiler (E12) is connected to a steam pipe (G6).

15. The production system for biodiesel from high-acid-value oils using enzymatic methods according to claim 13, characterized in that, The top outlet of the methanol distillation column (C2) is connected to the shell-side inlet of the top condenser (E13). The tube side of the top condenser (E13) is connected to circulating cooling water. The shell-side exhaust port of the top condenser (E13) is connected to the shell side of the final condenser (E14). The shell-side condensate outlet of the top condenser (E13) is connected to the inlet of the methanol receiving tank (T10). The bottom outlet of the methanol receiving tank (T10) is connected to the inlet of the methanol pump (P23). The outlet of the methanol pump (P23) is connected to the methanol supply pipe (G2) and the top reflux port of the methanol distillation column (C2) through regulating valves.

16. A method for producing biodiesel from high-acid-value oils using an enzymatic process, employing the production system as described in any one of claims 1 to 15, characterized in that, Includes the following steps: S1: High acid value oil, methanol, and biological enzyme solution are fed into a multi-stage tandem enzyme reactor in the reaction and preliminary separation section, where continuous esterification and transesterification reactions are carried out at 35-40℃ to obtain a reaction mixture. S2: Separate the reaction mixture obtained in step S1 by sedimentation to obtain a light phase fatty acid methyl ester mixed oil and a heavy phase dilute glycerol; S3: The dilute glycerol obtained in step S2 is evaporated and concentrated to obtain crude glycerol; S4: After heating the mixed oil obtained in step S2, it is mixed with alkali solution for neutralization reaction, and then centrifuged to obtain desoaped fatty acid methyl ester and soap residue. S5: The soap residue obtained in step S4 is subjected to steam desolventizing to remove the methanol contained therein; S6: The desoaped fatty acid methyl ester obtained in step S4 is acid-washed and water-washed, then heated and vacuum-dried to obtain a biodiesel product that meets the standards. S7: Collect the methanol vapor generated in each step of the system, and recover the methanol after condensation, absorption and distillation and reuse it in the reaction of step S1.

17. The method for producing biodiesel from high-acid-value oils using enzymatic methods according to claim 16, characterized in that, In step S1, the amount of the added bio-enzyme solution is 0.12%-0.15% of the weight of the high acid value oil, and the enzyme solution is mainly added to the first-stage reactor (R1); the multi-stage tandem enzyme reactor is four-stage, and the material temperature in each stage reactor is controlled at 40℃, with the final conversion rate reaching over 98%.

18. The method for producing biodiesel from high-acid-value oils using enzymatic methods according to claim 16, characterized in that, In step S4, the mixed oil is heated to 60°C and then mixed and neutralized with 10% liquid alkali. In step S6, the desoaped fatty acid methyl ester is heated to 120°C and then fed into the methyl ester drying tower (C1) for drying under vacuum conditions with an absolute pressure of less than 60 mbar, so that the methanol residue in the fatty acid methyl ester is reduced to less than 50 ppm and the moisture content is reduced to less than 100 ppm.

19. The method for producing biodiesel from high-acid-value oils using enzymatic methods according to claim 16, characterized in that, In step S5, the soap residue is desolventized using steam at 90°C to reduce the methanol residue in the soap residue to below 100 ppm. In step S7, the wastewater discharged from the bottom of the methanol distillation column (C2) is recycled after heat recovery and reused in the soap residue desolventization process of step S5 or the liquid alkali dilution process of step S4 to achieve zero wastewater discharge.

Images