CN115672204A

CN115672204A - System and method for producing biodiesel in large scale by using low-acid-value waste cooking oil

Info

Publication number: CN115672204A
Application number: CN202110859834.8A
Authority: CN
Inventors: 叶彬; 徐兴; 石树勋; 叶正强
Original assignee: Sichuan Jinshang Environmental Protection Technology Co ltd
Current assignee: Sichuan Jinshang Environmental Protection Technology Co ltd
Priority date: 2021-07-28
Filing date: 2021-07-28
Publication date: 2023-02-03

Abstract

The invention discloses a system and a method for producing biodiesel on a large scale by using low-acid-value waste cooking oil, which solve the technical problems of high soap content of glycerol, difficult separation, poor quality, large investment of a separation system and low total yield of biodiesel in the process of producing the biodiesel by using the existing low-acid-value waste cooking oil. The biodiesel system comprises a pretreatment system and a solid acid catalytic system. The production method comprises the steps of hydrolyzing the low-acid-value waste cooking oil through a pretreatment system to obtain hydrolyzed fatty acid, then enabling the hydrolyzed fatty acid to enter a solid acid catalysis system, and efficiently generating high-purity biodiesel through the catalysis of the solid acid on methanol. The invention integrates grease hydrolysis and solid acid catalysis into a continuous biodiesel production system, and has the advantages of low production cost, short process route, reduced methanol loss and thorough glycerol separation.

Description

System and method for producing biodiesel in large scale by using low-acid-value waste cooking oil

Technical Field

The invention belongs to the technical field of waste animal and vegetable oil processing, and particularly relates to a system and a method for producing biodiesel on a large scale by using low-acid-value waste cooking oil.

Background

The biodiesel refers to fatty acid methyl ester or ethyl ester formed by ester conversion of waste animal and vegetable oil or microbial oil such as vegetable oil and animal oil with methanol or ethanol. The biodiesel is a green energy source, and compared with petroleum diesel, the biodiesel has the characteristics of good environmental protection performance, good engine starting performance, good fuel performance, wide raw material source, renewability and the like. At present, the oil consumption in China is up to 1700 ten thousand tons, more than 250 ten thousand tons of waste edible oil are produced every year, and the waste edible oil is converted into biodiesel by using the technology. Compared with mineral diesel oil, the biodiesel oil has the characteristic of environmental protection, the discharge amount of toxic organic matters in the tail gas of the diesel oil vehicle is only 1/10, the discharge amount of particulate matters is 20 percent, and CO is contained ₂ And CO emissions were only 10%. The low-acid value catering waste oil has high triglyceride content, and compared with the traditional biodiesel production method, the method has the advantages of high soap content of glycerol, difficult separation, poor quality, large investment of a separation system and low total yield of biodiesel.

Therefore, designing a system and a method for mass production of biodiesel from low-acid-value waste cooking oil to at least solve some of the above technical problems becomes a technical problem to be solved urgently by those skilled in the art

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the system and the method for producing biodiesel on a large scale by using the low-acid-value waste cooking oil solve the technical problems of high soap content, difficult separation, poor quality, large investment of a separation system and low total yield of biodiesel produced by using the existing low-acid-value waste cooking oil.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a system for producing biodiesel on a large scale by using low-acid-value waste cooking oil comprises a pretreatment system and a solid acid catalysis system, wherein the pretreatment system is used for carrying out enzyme hydrolysis treatment on the low-acid-value waste cooking oil to obtain hydrolyzed fatty acid, and the solid acid catalysis system is connected from the pretreatment system and is used for catalyzing the hydrolyzed fatty acid to generate fatty acid methyl ester through solid acid;

the pretreatment system comprises a grease cache tank, a hydrolase cache tank, a pure water cache tank, an enzyme hydrolysis tank, a spray dryer, a three-phase separator, a residue pool, a grease tank, a membrane separator, a clear phase collection tank and a thick phase collection tank, wherein the enzyme hydrolysis tank is respectively connected from the grease cache tank, the hydrolase cache tank and the pure water cache tank and used for grease hydrolysis reaction, the spray dryer is respectively connected from the enzyme hydrolysis tank and used for drying product fatty acid, the three-phase separator is used for separating reaction mixture, the residue pool is respectively connected from the three-phase separator and used for collecting reaction residues, the grease tank is used for collecting unreacted grease, the membrane separator is used for oil-water separation, and the clear phase collection tank is respectively connected from the membrane separator and used for collecting water enzyme liquid and the thick phase collection tank is used for collecting glycerol; the spray dryer comprises a primary spray dryer connected from the enzymatic hydrolysis tank and a secondary spray dryer connected from the primary spray dryer.

Further, the solid acid catalysis system comprises a first static mixer which is respectively connected from the secondary spray dryer and the liquid methanol buffer tank and used for mixing and reacting the fatty acid and the methanol, a first reaction tower which is connected from the first static mixer, a liquid pressure booster which is connected from the first reaction tower and used for regulating the pressure of the primary reaction product, a second raw material steam heater which is connected from the liquid pressure booster and used for heating the primary reaction product, a second static mixer which is respectively connected from the liquid methanol buffer tank and the second raw material steam heater and used for mixing the primary reaction product and the methanol, and a second reaction tower which is connected from the second static mixer; the first reaction tower is connected with a methanol recovery section, and the second reaction tower is connected with a liquid methanol cache tank;

a high-purity fatty acid conveying pipe is arranged between the first static mixer and the second-stage spray dryer, and a first raw material steam heater for heating the high-purity fatty acid is arranged on the high-purity fatty acid conveying pipe; a first liquid methanol delivery pipe is arranged between the first static mixer and the liquid methanol cache tank, and a first methanol steam heater for preheating methanol is arranged on the first liquid methanol delivery pipe; and a second liquid methanol conveying pipe is arranged between the second static mixer and the liquid methanol buffer tank, and a second methanol steam heater for preheating methanol is arranged on the second liquid methanol conveying pipe.

Further, the enzyme hydrolysis tank comprises an enzyme hydrolysis tank body and a circulating mechanism which is arranged on the enzyme hydrolysis tank body and used for circulating hydrolysis; the circulating mechanism comprises a main circulating liquid outlet channel connected from the bottom of the enzyme hydrolysis tank body, a first sub-circulating pipeline and a second sub-circulating pipeline, wherein the first sub-circulating pipeline is connected to the top of the enzyme hydrolysis tank body, the second sub-circulating pipeline is connected to the middle of the enzyme hydrolysis tank body, a first liquid outlet valve is arranged on the main circulating liquid outlet channel, a first circulating pump is arranged on the first sub-circulating pipeline, and a second circulating pump is arranged on the second sub-circulating pipeline.

Furthermore, a first circulating liquid inlet pipe, a second circulating liquid inlet pipe and a third circulating liquid inlet pipe which are distributed in a shape like a Chinese character 'ji' are arranged at the top of the enzymatic hydrolysis tank body, and a first sub-circulating pipeline is respectively connected with the first circulating liquid inlet pipe, the second circulating liquid inlet pipe and the third circulating liquid inlet pipe; a first liquid inlet valve, a second liquid inlet valve and a third liquid inlet valve are respectively arranged on the first circulating liquid inlet pipe, the second circulating liquid inlet pipe and the third circulating liquid inlet pipe;

a fourth circulating liquid inlet pipe, a fifth circulating liquid inlet pipe and a sixth circulating liquid inlet pipe are arranged in the middle of the enzyme hydrolysis tank body, a second sub-circulating pipeline is respectively connected with the fourth circulating liquid inlet pipe, the fifth circulating liquid inlet pipe and the sixth circulating liquid inlet pipe, the fourth circulating liquid inlet pipe, the fifth circulating liquid inlet pipe and the sixth circulating liquid inlet pipe are all distributed in a tangent mode with the cylindrical shell of the enzyme hydrolysis tank body, and a fourth liquid inlet valve, a fifth liquid inlet valve and a sixth liquid inlet valve are respectively arranged on the fourth circulating liquid inlet pipe, the fifth circulating liquid inlet pipe and the sixth circulating liquid inlet pipe;

a circulating branch liquid channel is connected between the enzyme hydrolysis tank body and the second branch circulating pipeline, a first circulating liquid outlet pipe, a second circulating liquid outlet pipe and a third circulating liquid outlet pipe are arranged on the lower portion of the enzyme hydrolysis tank body, one end of the circulating branch liquid channel is respectively connected with the first circulating liquid outlet pipe, the second circulating liquid outlet pipe and the third circulating liquid outlet pipe, the other end of the circulating branch liquid channel is connected onto the second branch circulating pipeline, an access point of the circulating branch liquid channel and the second branch circulating pipeline is located between the second circulating pump and the circulating main liquid outlet channel, the first circulating liquid outlet pipe, the second circulating liquid outlet pipe and the third circulating liquid outlet pipe are both distributed in a tangent mode with the cylindrical shell of the enzyme hydrolysis tank body, and a second liquid outlet valve, a third liquid outlet valve and a fourth liquid outlet valve are respectively arranged on the first circulating liquid outlet pipe, the second circulating liquid outlet pipe and the third circulating liquid outlet pipe.

Further, a grease inlet is formed in the top of the enzymatic hydrolysis tank body, and a first input valve is arranged at the grease inlet; a grease conveying pipe is arranged between the grease inlet and the grease cache tank, and a first conveying pump and a first output valve are respectively arranged on the grease conveying pipe;

a hydrolase liquid inlet is formed in the top of the enzymatic hydrolysis tank body, and a second input valve is arranged at the hydrolase liquid inlet; a hydrolase conveying pipe is arranged between the hydrolase liquid inlet and the hydrolase cache tank, and the hydrolase conveying pipe is respectively provided with a second conveying pump and a second output valve; a pure water conveying pipe is arranged between the hydrolase liquid inlet and the pure water cache tank, and the pure water conveying pipe is respectively provided with a third conveying pump and a third output valve;

a propeller stirrer for mixing mixed grease and hydrolytic enzyme liquid is arranged in the enzymatic hydrolysis tank body, a sight glass for the condition of internal materials is arranged on the enzymatic hydrolysis tank body, the enzymatic hydrolysis tank body is of a double-layer structure, and heating coils for heating the internal materials are uniformly distributed in an interlayer of the enzymatic hydrolysis tank body; the bottom of the enzymatic hydrolysis tank body is respectively connected with a primary spray dryer through a fatty acid conveying pipe and a three-phase separator through a reactant conveying pipe; and a fourth delivery pump and a steam heater are respectively arranged on the fatty acid delivery pipe, and a fifth delivery pump is arranged on the reactant delivery pipe.

The top of the first-stage spray dryer is connected with the vacuum pump through a first exhaust pipe, the top of the second-stage spray dryer is connected with the vacuum pump through a second exhaust pipe, a first exhaust valve is arranged on the first exhaust pipe, and a second exhaust valve is arranged on the second exhaust pipe;

the primary spray dryer and the secondary spray dryer are identical in structure, arc-shaped baffles are arranged at the inner tops of the primary spray dryer and the secondary spray dryer, and liquid level meters are arranged on the outer walls of the primary spray dryer and the secondary spray dryer; and a first-stage drying conveying pipe is connected between the bottom of the first-stage spray dryer and the top of the second-stage spray dryer, a sixth conveying pump is arranged on the first-stage drying conveying pipe, and a seventh conveying pump is arranged on the high-purity fatty acid conveying pipe.

Furthermore, the first reaction tower and the second reaction tower have the same structure and respectively comprise a reaction tower body for reacting the mixed materials, a separating body which is communicated with the reaction tower body and is of an integrated structure and used for separating out slag water, and a drain pipe connected out of the separating body, wherein the reaction tower body is provided with a liquid discharge area and a reaction area which are communicated with each other from bottom to top;

the separator is the back taper structure, and the back taper top surface links to each other with the reaction zone, and the back taper bottom surface links to each other with the drain pipe, is equipped with the type of falling U pipeline section on the drain pipe, and the type of falling U pipeline section top flushes with the separator top surface mutually, and the drain pipe delivery port is connected with methyl alcohol purification workshop section.

Further, a solid acid catalyst and a stirrer for stirring the materials in the reaction zone are arranged in the reaction zone, and the stirrer is a submersible plug flow stirrer;

the bottom of the reaction zone is respectively provided with a catalyst filling hole for filling and discharging a solid acid catalyst and a feed inlet for inputting a mixed material, and the feed inlet is connected with the first static mixer or the second static mixer through a feed pipe;

the bottom of the reaction zone is provided with a feeding distribution disc which is communicated with the feeding hole and is used for uniform feeding, and feeding distribution holes are uniformly distributed on the feeding distribution disc;

the two ends of the reaction zone are respectively provided with a first filter screen and a second filter screen for preventing the solid acid catalyst from flowing out, the first filter screen and the second filter screen have the same structure, the diameter of the first filter screen is consistent with the inner diameter of the reaction zone, and the diameter of the filter hole is smaller than the diameter of the solid acid catalyst.

Furthermore, a discharge hole for discharging the product is formed in the side wall of the liquid discharge area, the discharge hole of the first reaction tower is connected with the liquid supercharger, and the discharge hole of the second reaction tower is connected with the product collection section;

the top of the liquid discharge area is respectively provided with a pressure regulating valve for regulating the pressure of an internal medium, a safety valve for protecting the safety of a system and a methanol liquid outlet for recycling methanol, the methanol liquid outlet of the first reaction tower is connected to a methanol recycling section, and the methanol liquid outlet of the second reaction tower is connected to a liquid methanol cache tank.

A production method of a system for producing biodiesel in large scale by using low-acid-value waste cooking oil comprises the following steps:

step A: after the low-acid-value waste cooking oil in the grease cache tank, the hydrolase in the hydrolase cache tank and the pure water in the pure water cache tank enter the enzyme hydrolysis tank to be uniformly mixed, grease hydrolysis reaction is carried out to generate product fatty acid, byproduct glycerol and other mixtures, and the volume ratio of grease to water in the reaction condition is 6:4, the mass of the hydrolase is 5 percent of the weight of the grease, the hydrolysis pressure is normal pressure, the hydrolysis temperature is 55 ℃, and the hydrolysis time is 48 hours; conveying and separating byproduct glycerol and other mixtures into a three-phase separator through a reactant conveying pipe, and separating out residues, residual oil and a water-enzyme-glycerol mixed solution, wherein the residues are collected into a residue pool, and the oil is collected into an oil tank; the water-enzyme-glycerol mixed solution enters a membrane separator, and is separated and filtered again to obtain byproduct glycerol and water-enzyme mixed solution, wherein the byproduct glycerol is collected into a phase collection tank, and the water-enzyme mixed solution is collected into a clear phase collection tank;

and B: conveying the product fatty acid in the step A into a primary spray dryer through a fatty acid conveying pipe for primary spray drying, pressurizing to 0.4MPa by a fourth conveying pump in the conveying process, preheating to 120 ℃ by a steam heater, and performing primary spray drying to obtain a primary fatty acid dried product, wherein the drying pressure in the primary spray drying is-0.088 MPa, and the drying temperature is 120 ℃;

and C: b, allowing the fatty acid primary dried product in the step B to enter a secondary spray dryer for secondary spray drying to obtain high-purity fatty acid, wherein the drying pressure is-0.088 MPa, and the drying temperature is 120 ℃;

step D: c, heating the high-purity fatty acid in the step C to 110-120 ℃ by using a first raw material steam heater, and then fully mixing the high-purity fatty acid with liquid methanol heated to 55 ℃ by using a first methanol steam heater in a first static mixer to obtain a raw material mixture;

step E: the raw material mixture in the step F enters a first reaction tower for a first catalytic reaction to obtain a primary reaction product, wherein the catalytic conditions are normal pressure and 110 ℃, and the solid isThe acid catalyst is sulfuric acid/titanium dioxide SO ₄ ^2- /TiO ₂ A catalyst;

step F: adjusting the primary reaction product in the step G to micro-positive pressure by a liquid supercharger, heating the primary reaction product to 110-120 ℃ by a second raw material steam heater, and fully mixing the primary reaction product with liquid methanol heated to 55 ℃ by a second methanol steam heater in a second static mixer to obtain a second mixture;

step G: the second mixture in the step H enters a second reaction tower for a second catalytic reaction to obtain the high-purity biodiesel, wherein the catalytic conditions are normal pressure and 110 ℃, and the solid acid catalyst is sulfuric acid/titanium dioxide SO ₄ ^2- /TiO ₂ A catalyst.

Compared with the prior art, the invention has the following beneficial effects:

the invention has simple structure, scientific and reasonable design and convenient use, and solves the technical problems of high soap content, difficult separation, poor quality, large investment of a separation system and low total yield of the biodiesel in the prior production of the biodiesel by the low-acid-value waste cooking oil. The invention integrates the low acid value waste cooking oil hydrolysis and solid acid catalysis into a continuous biodiesel production system, cancels an independent ester exchange system and a glycerin separation system, has low production cost and short process route, and reduces the overall investment by more than 40 percent; in addition, by adopting a pretreatment system capable of circulating hydrolysis and synchronous glycerin separation and a continuous solid acid catalytic system capable of separating methanol and water on line, the methanol loss is reduced, the glycerin separation is thorough, the grease utilization rate is high, and the total yield of the biodiesel can be increased by 3-5%.

The invention comprises a pretreatment system and a solid acid catalytic system connected from the pretreatment system, wherein the waste gas oil completes the generation and drying of fatty acid and the separation and recovery of byproduct glycerol in the pretreatment system, the high-purity fatty acid generated and treated by the pretreatment system enters the solid acid catalytic system to catalyze and generate biodiesel, and the pretreatment system for oil hydrolysis and the solid acid catalytic system are integrated into a continuous large-scale industrial production system, so that the production continuity and the industrial flow are greatly enhanced, and the investment area and the investment cost are reduced.

The pretreatment system comprises a grease cache tank, a hydrolase cache tank, a pure water cache tank, an enzyme hydrolysis tank, a spray dryer, a three-phase separator, a residue pool, a membrane separator, a clear phase collecting tank and a concentrated phase collecting tank, wherein grease in the grease cache tank, hydrolase in the hydrolase cache tank and pure water in the pure water cache tank simultaneously enter the enzyme hydrolysis tank for hydrolysis reaction according to a certain proportion, and after the reaction is finished, main product fatty acid enters the spray dryer for spray drying twice to obtain high-purity fatty acid, and then directly enters a subsequent solid acid catalytic system; and (3) separating the byproduct mixture in a three-phase separator while drying the fatty acid to obtain a mixture of residue, grease, hydrolase and glycerol, separating the mixture by a membrane separator to obtain clear-phase water enzyme liquid and concentrated-phase glycerol, wherein the glycerol can be used for producing propylene glycol, and the income of enterprises is increased.

The solid acid catalytic system comprises a first static mixer, a first reaction tower, a liquid supercharger, a second raw material steam heater, a second static mixer and a second reaction tower, wherein high-purity fatty acid hydrolyzed and dried by a pretreatment system is heated by the first raw material steam heater, then is fully mixed with methanol heated by the first methanol steam heater in the first static mixer, and reacts in the first reaction tower; and adjusting the primary reaction product after the first reaction to micro-positive pressure by a liquid supercharger, heating by a second raw material steam heater, fully mixing the primary reaction product with methanol heated by a second methanol steam heater in a second static mixer, and reacting in a second reaction tower to obtain a secondary reaction product, namely the biodiesel with high purity and high yield. The solid acid catalytic system adopts the series connection of the double reaction towers to realize the full reaction of the fatty acid, effectively improves the reaction efficiency and greatly increases the yield of the biodiesel.

Drawings

FIG. 1 is a schematic view of the structure of the present invention.

FIG. 2 is an enlarged view of the pretreatment system.

FIG. 3 is a schematic view of an enzymatic hydrolysis tank.

FIG. 4 is a top view of the enzymatic hydrolysis tank.

FIG. 5 is a cross-sectional view of an enzymatic hydrolysis tank.

Fig. 6 is an enlarged view of the solid acid catalytic system.

FIG. 7 is a schematic structural diagram of the first reaction tower or the second reaction tower.

Fig. 8 is a schematic view of a feed distribution tray configuration.

Wherein, the names corresponding to the reference numbers are:

1-a grease buffer tank, 2-a hydrolase buffer tank, 3-a pure water buffer tank, 4-a enzyme hydrolysis tank, 5-a three-phase separator, 6-a residue pool, 7-a grease tank, 8-a membrane separator, 9-a clear phase collecting tank, 10-a concentrated phase collecting tank, 11-a first-level spray dryer, 12-a second-level spray dryer, 13-a liquid methanol buffer tank, 14-a first static mixer, 15-a first reaction tower, 16-a liquid supercharger, 17-a second raw material steam heater, 18-a second static mixer, 19-a second reaction tower, 20-a high-purity fatty acid conveying pipe, 21-a first raw material steam heater, 22-a first liquid methanol conveying pipe, 23-a first methanol steam heater, 24-a second liquid methanol delivery pipe, 25-a second methanol steam heater, 26-a grease delivery pipe, 27-a first delivery pump, 28-a first output valve, 29-a hydrolase delivery pipe, 30-a second delivery pump, 31-a second output valve, 32-a pure water delivery pipe, 33-a third delivery pump, 34-a third output valve, 35-a fatty acid delivery pipe, 36-a reactant delivery pipe, 37-a fourth delivery pump, 38-a steam heater, 39-a fifth delivery pump, 40-a vacuum pump, 41-an enzyme hydrolysis tank body, 42-a main circulation liquid outlet channel, 43-a first branch circulation channel, 44-a second branch circulation channel, 45-a first liquid outlet valve, 46-a first circulation liquid inlet pipe, 47-a second circulation liquid inlet pipe, 48-third circulating liquid inlet pipe, 49-first circulating pump, 50-first gas outlet pipe, 51-second gas outlet pipe, 52-first gas outlet valve, 53-second gas outlet valve, 54-arc baffle, 55-liquid level meter, 56-primary drying delivery pipe, 57-sixth delivery pump, 58-seventh delivery pump, 59-reaction tower body, 60-separation body, 61-water outlet pipe, 62-liquid outlet area, 63-reaction area, 64-solid acid catalyst, 65-stirrer, 66-catalyst filling hole, 67-feed inlet, 68-feed inlet pipe, 69-feed distribution disc, 70-feed distribution hole, 71-first filter screen, 72-second filter screen, 73-discharge outlet, 74-pressure regulating valve, 75-safety valve, 76-methanol liquid outlet, 410-second circulating pump, 411-first liquid inlet valve, 412-second liquid inlet valve, 413-third liquid inlet valve, 414-fourth circulating pipe, 415-fifth circulating pipe, 416-sixth circulating pipe, 417-fourth circulating valve, 418-fifth circulating valve, 418-third liquid inlet valve, 418-second liquid outlet valve, 420-second liquid inlet pipe, 420-second liquid outlet valve, 420-fourth circulating pump, 410-fourth circulating pump, 427, 410-third liquid inlet pipe, 420-fourth circulating pump, 410-fourth circulating pump, fourth circulating pipe, 420-fourth circulating pipe, 410-fourth circulating pump, 410-fourth circulating pipe, 410, 433-heating coil.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the device or element referred to must have a particular orientation or be constructed and operated in a particular orientation, and thus, they should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected; of course, mechanical connection and electrical connection are also possible; alternatively, they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood according to specific situations by those of ordinary skill in the art.

As shown in figures 1-8, the system and the method for producing biodiesel on a large scale by using low-acid-value waste cooking oil provided by the invention have the advantages of simple structure, scientific and reasonable design and convenience in use, and solve the technical problems of high glycerin soap content, difficulty in separation, poor quality, large investment of a separation system and low total yield of biodiesel produced by using the existing low-acid-value waste cooking oil. The invention integrates the hydrolysis of the low-acid value waste cooking oil and the catalysis of the solid acid into a continuous biodiesel production system, cancels an independent ester exchange system and a glycerin separation system, and has low production cost, short process route and overall investment reduction of more than 40 percent; in addition, by adopting a pretreatment system capable of circulating hydrolysis and synchronous glycerol separation and a continuous solid acid catalytic system capable of separating methanol and water on line, the methanol loss is reduced, the glycerol separation is thorough, the grease utilization rate is high, and the total yield of the biodiesel can be increased by 3-5%.

The invention comprises a pretreatment system for enzymatic hydrolysis of low-acid-value waste cooking oil and a solid acid catalytic system connected from the pretreatment system and used for catalyzing fatty acid, wherein the waste gas oil completes generation and drying of fatty acid and separation and recovery of byproduct glycerol in the pretreatment system, the high-purity fatty acid generated and treated by the pretreatment system enters the solid acid catalytic system to be catalyzed and generated into biodiesel, and the pretreatment system for hydrolysis of the oil and the solid acid catalytic system are integrated into a continuous large-scale industrial production system, so that the production continuity and industrial flow are greatly enhanced, and the investment area and the investment cost are reduced.

The pretreatment system comprises a grease cache tank 1, a hydrolase cache tank 2, a pure water cache tank 3, an enzyme hydrolysis tank 4 for grease hydrolysis reaction respectively connected from the grease cache tank 1, the hydrolase cache tank 2 and the pure water cache tank 3, a spray dryer for drying product fatty acid and a three-phase separator 5 for separating reaction mixture respectively connected from the enzyme hydrolysis tank 4, a residue pool 6 for collecting reaction residues, a grease tank 7 for collecting unreacted grease and a membrane separator 8 for oil-water separation respectively connected from the three-phase separator 5, and a clear phase collection tank 9 for collecting water and enzyme liquid and a concentrated phase collection tank 10 for collecting glycerol respectively connected from the membrane separator 8; the spray dryer includes a primary spray dryer 11 connected from the enzymatic hydrolysis tank 4, and a secondary spray dryer 12 connected from the primary spray dryer 11. The grease in the grease cache tank 1, the hydrolase in the hydrolase cache tank 2 and the pure water in the pure water cache tank 3 simultaneously enter the enzymatic hydrolysis tank 4 according to a certain proportion for hydrolysis reaction, and the main product fatty acid after the reaction is finished enters a spray dryer for twice spray drying to obtain high-purity fatty acid, and then directly enters the subsequent production working condition; and (3) while the fatty acid is dried, the byproduct mixture enters a three-phase separator 5 for separation to obtain a mixture of residues, grease, hydrolase and glycerol, and the mixture is separated by a membrane separator 8 to obtain clear-phase water enzyme liquid and concentrated-phase glycerol, wherein the glycerol can be used for producing propylene glycol, so that the enterprise income is increased.

The enzyme hydrolysis tank 4 comprises an enzyme hydrolysis tank body 41 and a circulating mechanism which is arranged on the enzyme hydrolysis tank body 41 and is used for circulating hydrolysis; the circulating mechanism comprises a main circulating liquid outlet channel 42, a first sub-circulating pipeline 43 and a second sub-circulating pipeline 44. Wherein the main liquid outlet channel 42 of circulation connects out from the bottom of the enzymatic hydrolysis tank 41, the first branch circulation pipeline 43 connects out from the main liquid outlet channel 42 of circulation and inserts to the top of the enzymatic hydrolysis tank 41, the second branch circulation pipeline 44 connects out from the main liquid outlet channel 42 of circulation and inserts to the middle part of the enzymatic hydrolysis tank 41, the first branch circulation pipeline 43 and the second branch circulation pipeline 44 can make the materials in the enzymatic hydrolysis tank circulate and mix in the vertical direction, the contact and mixing reaction of grease and hydrolytic enzyme liquid is increased, and the efficiency of industrial large-scale hydrolysis reaction is greatly improved. And a first liquid outlet valve 45 is arranged on the circulating main liquid outlet channel 42, and the first liquid outlet valve 45 can control the material at the bottom of the enzyme hydrolysis tank body 41 to flow out and respectively lead to a first sub-circulating pipeline 43 and a second sub-circulating pipeline 44, so that different circulations are realized in sequence.

According to the invention, a first sub-circulating pipeline 43 is connected out of a main circulating liquid outlet 42, a first circulating pump 49 is arranged on the first sub-circulating pipeline 43, and the first circulating pump 49 can pump bottom materials into the top of an enzyme hydrolysis tank 41. The top of the enzyme hydrolysis tank body 41 is provided with a first circulating liquid inlet pipe 46, a second circulating liquid inlet pipe 47 and a third circulating liquid inlet pipe 48 which are distributed in a finished product shape, the first sub-circulating pipeline 43 is respectively connected with the first circulating liquid inlet pipe 46, the second circulating liquid inlet pipe 47 and the third circulating liquid inlet pipe 48, the pressure of circulating liquid is relieved by the first circulating liquid inlet pipe 46, the second circulating liquid inlet pipe 47 and the third circulating liquid inlet pipe 48, and meanwhile, the uniformity of the circulating liquid can be effectively improved by the distribution in a shape of a Chinese character 'pin'. The first circulating liquid inlet pipe 46, the second circulating liquid inlet pipe 47 and the third circulating liquid inlet pipe 48 are respectively provided with a first liquid inlet valve 411, a second liquid inlet valve 412 and a third liquid inlet valve 413, so that the opening and closing of different liquid inlet valves can be reasonably adjusted according to the circulating flow, and the most reasonable circulating hydrolysis is realized.

According to the invention, the second sub-circulation pipeline 44 is connected out of the main circulation liquid outlet channel 42, the second sub-circulation pipeline 44 is provided with the second circulation pump 410, and the second circulation pump 410 can pump the bottom material into the middle part of the enzyme hydrolysis tank 41. The middle part of the enzyme hydrolysis tank body 41 is provided with a fourth circulating liquid inlet pipe 414, a fifth circulating liquid inlet pipe 415 and a sixth circulating liquid inlet pipe 416, the second sub-circulating pipeline 44 is respectively connected with the fourth circulating liquid inlet pipe 414, the fifth circulating liquid inlet pipe 415 and the sixth circulating liquid inlet pipe 416, and the fourth circulating liquid inlet pipe 414, the fifth circulating liquid inlet pipe 415 and the sixth circulating liquid inlet pipe 416 are all in tangential distribution with the cylindrical shell of the enzyme hydrolysis tank body 41, and the tangential distribution ensures the uniform stability of material entering. The fourth circulating liquid inlet pipe 414, the fifth circulating liquid inlet pipe 415 and the sixth circulating liquid inlet pipe 416 are respectively provided with a fourth liquid inlet valve 417, a fifth liquid inlet valve 418 and a sixth liquid inlet valve 419, and the circulating opening and closing can be controlled by different liquid inlet valves, so that the circulating liquid inlet pipe adapts to the circulation of different liquid flows on one hand, and the uniformity of liquid inlet is ensured on the other hand.

A circulating branch liquid channel 420 is connected between an enzyme hydrolysis tank body 41 and a second branch circulating pipeline 44, a first circulating liquid outlet pipe 421, a second circulating liquid outlet pipe 422 and a third circulating liquid outlet pipe 423 are arranged at the lower part of the enzyme hydrolysis tank body 41, one end of the circulating branch liquid channel 420 is respectively connected with the first circulating liquid outlet pipe 421, the second circulating liquid outlet pipe 422 and the third circulating liquid outlet pipe 423, the other end of the circulating branch liquid channel is connected onto the second branch circulating pipeline 44, materials at the lower part of the enzyme hydrolysis tank body 41 respectively enter the circulating branch liquid channel 420 through the first circulating liquid outlet pipe 421, the second circulating liquid outlet pipe 422 and the third circulating liquid outlet pipe 423, and then are pumped into the middle part of the enzyme hydrolysis tank body 41 through the second branch circulating pipeline 44 and the second circulating pump 410 to realize circulating hydrolysis in the horizontal direction. The first circulation liquid outlet pipe 421, the second circulation liquid outlet pipe 422 and the third circulation liquid outlet pipe 423 are all distributed in a tangent manner with the cylindrical shell of the enzyme hydrolysis tank body 41, and the tangent distribution ensures the uniform stability of the material liquid outlet. And a second liquid outlet valve 424, a third liquid outlet valve 425 and a fourth liquid outlet valve 426 are respectively arranged on the first circulation liquid outlet pipe 421, the second circulation liquid outlet pipe 422 and the third circulation liquid outlet pipe 423, and each valve can be opened and closed according to the actual hydrolysis amount to sequentially realize the most reasonable horizontal circulation hydrolysis.

The top of the hydrolysis tank body 41 is provided with a grease inlet 427, the grease inlet 427 is provided with a first input valve 428, a grease conveying pipe 13 is arranged between the grease inlet 427 and the grease cache tank 1, and the grease conveying pipe 13 is respectively provided with a first conveying pump 14 and a first output valve 15. A hydrolase liquid inlet 429 is formed in the top of the enzyme hydrolysis tank 41, a second input valve 430 is arranged on the hydrolase liquid inlet 429, a hydrolase conveying pipe 21 is arranged between the hydrolase liquid inlet 429 and the hydrolase cache tank 2, and the hydrolase conveying pipe 21 is respectively provided with a second conveying pump 22 and a second output valve 23; a pure water delivery pipe 31 is provided between the hydrolase liquid inlet 429 and the pure water buffer tank 3, and the pure water delivery pipe 31 is provided with a third delivery pump 32 and a third output valve 33, respectively. Because the grease, the water and the hydrolase are not compatible, the grease, the water and the hydrolase are required to be conveyed into the enzyme hydrolysis tank 41 by different buffer tanks before reaction, wherein the volume ratio of the grease to the water is 6:4, the mass of the hydrolytic enzyme is 5 percent of the weight of the grease.

The top of the enzyme hydrolysis tank 41 is provided with a propeller stirrer 431, the enzyme hydrolysis tank 41 is provided with a sight glass 432, and the mixed liquid of the grease, the water and the hydrolytic enzyme is continuously stirred, mixed and reacted under the action of the propeller stirrer 431. The size and number of the blades of the propeller type stirrer 431 are set according to the size of the enzymatic hydrolysis tank 41 and the volume of the hydrolysis mixture. The sight glass 432 is installed on the enzymatic hydrolysis tank 41 by welding, bolting or clamping, and is used for detecting the reaction state of the internal materials and the liquid level height in the enzymatic hydrolysis tank 41, so as to facilitate the monitoring of the hydrolysis reaction. The enzymatic hydrolysis tank body 41 is of a double-layer structure, heating coils 433 used for heating internal materials are uniformly distributed in an interlayer of the enzymatic hydrolysis tank body, 70 ℃ hot water flows dynamically from bottom to top in the heating coils 433, appropriate hydrolysis temperature is provided for internal hydrolysis mixed liquid, and the heating coils 433 are in circulating connection with a boiler system. The hydrolysis reaction conditions in the enzymatic hydrolysis tank 41 are hydrolysis pressure and normal pressure, hydrolysis temperature of 55 ℃ and hydrolysis time of 48 hours.

The grease is continuously subjected to back-and-forth circulating hydrolysis in each circulating pipeline of an enzyme hydrolysis tank 41 to obtain a main product fatty acid and a byproduct mixture, wherein the main product fatty acid is conveyed into a spray dryer of a drying section of a pretreatment system through a fatty acid conveying pipe 35, the byproduct mixture is conveyed into a three-phase separator 8 of a byproduct separation section through a reactant conveying pipe 36, and therefore, the main product drying and the byproduct recovery are simultaneously carried out. The byproduct mixture is separated in a three-phase separator 8 to obtain residue, a small amount of grease which does not participate in the reaction and is left, and water-enzyme-glycerol mixed liquor, the residue is collected in a residue pool 6, the grease is collected in a grease tank 7, the water-enzyme-glycerol mixed liquor is separated and filtered by a membrane separator 8 to obtain water-enzyme mixed liquor and glycerol, the water-enzyme mixed liquor is collected in a clear phase collection tank 9, and the glycerol is collected in a concentrated phase collection tank 10 for further concentration and purification. The glycerol serving as a byproduct of grease hydrolysis can be used for producing propylene glycol, the added value of the propylene glycol is high, and great profit can be brought to enterprises.

The main product fatty acid in the pretreatment system of the invention enters a spray dryer for drying and curing, before spray drying, the fatty acid needs to be preheated by a steam heater 38 on a fatty acid conveying pipe 35, and simultaneously, the fatty acid is pressurized to 0.4MPa by a fourth conveying pump 37 on the fatty acid conveying pipe 35. The pressurized and preheated fatty acid is then spray dried twice, sequentially by a first spray drying and a second spray drying, to fully remove the water in the fatty acid, the pressure in the first spray dryer 11 and the second spray dryer 12 is-0.088 MPa, and the temperature is 120 ℃. Fatty acid sequentially enters the primary spray dryer 11 through the fatty acid conveying pipe 35 for primary drying, then is conveyed into the secondary spray dryer 12 through the primary drying conveying pipe 56 for secondary drying to obtain powdery or granular high-purity fatty acid, and finally is conveyed to the solid acid catalytic system through the high-purity fatty acid conveying pipe 20 for catalytic reaction.

The pretreatment system further comprises a vacuum pump 40, the top of the primary spray dryer 11 is connected with the vacuum pump 40 through a first exhaust pipe 50, the top of the secondary spray dryer 12 is connected with the vacuum pump 40 through a second exhaust pipe 51, a first exhaust valve 52 is arranged on the first exhaust pipe 50, and a second exhaust valve 53 is arranged on the second exhaust pipe 51. The first-stage spray dryer 11 and the second-stage spray dryer 12 have the same structure, and after the fatty acid is atomized in the drying chamber of the spray dryer and then contacts with hot air in the drying chamber, the moisture in the fatty acid is quickly vaporized and is exhausted through the exhaust pipe under the action of the vacuum pump 40. Meanwhile, the arc-shaped baffles 54 arranged at the tops of the first-stage spray dryer 11 and the second-stage spray dryer 12 can prevent the fatty acid from being discharged from the tops; the level gauge 55 that the outer wall of one-level spray dryer 11 and second grade spray dryer 12 all was equipped with is convenient for observe the drying condition of inside fatty acid.

The solid acid catalytic system comprises a first static mixer 14 which is respectively connected from a secondary spray dryer 12 and a liquid methanol cache tank 13 and used for mixing and reacting fatty acid and methanol, a first reaction tower 15 which is connected from the first static mixer 14, a liquid pressure booster 16 which is connected from the first reaction tower 15 and used for regulating the pressure of a primary reaction product, a second raw material steam heater 17 which is connected from the liquid pressure booster 16 and used for heating the primary reaction product, a second static mixer 18 which is respectively connected from the liquid methanol cache tank 13 and the second raw material steam heater 17 and used for mixing the primary reaction product and the methanol, and a second reaction tower 19 which is connected from the second static mixer 18;

a high-purity fatty acid delivery pipe 20 is arranged between the first static mixer 14 and the second-stage spray dryer 12, and a first raw material steam heater 21 for heating the high-purity fatty acid is arranged on the high-purity fatty acid delivery pipe 20; a first liquid methanol delivery pipe 22 is arranged between the first static mixer 14 and the liquid methanol cache tank 13, and a first methanol steam heater 23 for preheating methanol is arranged on the first liquid methanol delivery pipe 22; a second liquid methanol delivery pipe 24 is arranged between the second static mixer 18 and the liquid methanol buffer tank 13, and a second methanol steam heater 25 for preheating methanol is arranged on the second liquid methanol delivery pipe 24.

High-purity fatty acid is produced and conveyed to the working condition system by the pretreatment system, the high-purity fatty acid and methanol are mixed twice and catalytic reaction twice is completed, the high-purity fatty acid is heated by a first raw material steam heater 21 and then fully mixed with the methanol heated by a first methanol steam heater 23 in a first static mixer 14, and the high-purity fatty acid and the methanol react in a first reaction tower 15; the primary reaction product after the first reaction is adjusted to a micro positive pressure by a liquid pressurizer 16, heated by a second raw material steam heater 17, fully mixed with methanol heated by a second methanol steam heater 24 in a second static mixer 18, and reacted in a second reaction tower 19 to obtain a secondary reaction product, namely the biodiesel with high purity and high yield.

The solid acid catalytic system adopts a structure of connecting two reaction towers in series, so that two catalytic reactions of fatty acid are carried out, the full reaction of grease is realized, the reaction efficiency is effectively improved, and the yield of biodiesel is greatly increased.

The first reaction tower 15 and the second reaction tower 19 have the same structure and respectively comprise a reaction tower body 59 for reacting mixed materials, a separating body 60 which is connected with the reaction tower body 59 and is used for separating slag water, and a drain pipe 61 connected from the separating body 60, wherein the mixed materials are fully mixed and then input into the reaction tower body 59, and the mixed materials generate the biodiesel under the catalysis of a solid acid catalyst 64 arranged in the reaction tower body 59. The structure can simultaneously realize the synchronous separation of the production of the biodiesel and the slag water, the biodiesel production is carried out in the reaction tower body 59, the slag water sinks into the separating body 60, the methanol-slag water mixture is separated out through the drain pipe 61, the biodiesel production and the separation of the methanol-slag water mixture can be synchronously and continuously finished, the impurities in the biodiesel are greatly reduced, the subsequent steps of biodiesel refining and purifying are reduced, meanwhile, the methanol-slag water mixture obtained by the separation enters a methanol purification working section, and the high-purity methanol can be quickly extracted and obtained.

In addition, the methanol in the first reaction tower 15 and the methanol in the second reaction tower 19 can be discharged through the methanol liquid outlet 76, wherein the methanol in the first reaction tower 15 flows to the methanol recovery section from the methanol liquid outlet 76, and participates in the subsequent operation after purification, while the methanol in the second reaction tower 19 has higher purity, and is directly recovered to the liquid methanol cache tank 13 from the methanol liquid outlet 76 for recycling of the pretreatment system and the catalytic system. The structure can realize the on-line continuous separation and continuous recycling of the methanol, greatly improve the production efficiency and reduce the production cost.

The reaction tower body 59 is divided into a liquid discharge area 62 and a reaction area 63 which are communicated with each other from bottom to top, a solid acid catalyst 64 and a stirrer 65 for stirring materials in the solid acid catalyst are arranged in the reaction area 63, the stirrer 63 is arranged on the side wall of the reaction area 63, and the stirrer 65 is a submersible plug flow type stirrer which can provide stirring and mixing force for the materials in the reaction area, so that the reaction materials are contacted more fully and reacted more completely. The solid acid catalyst 64 is in a solid form and is uniformly distributed in the reaction zone 63, so that the contact area of the solid acid catalyst and the reaction mixture can be greatly increased, and the reaction efficiency is improved; the solid acid catalyst 64 can be filled and discharged through a catalyst filling hole 66 formed in the bottom of the reaction zone 63, and the catalyst filling hole 66 is provided with a filling valve for opening and closing, so that on one hand, the operation of workers is facilitated, and on the other hand, the sealing reaction of the reaction tower body 59 is ensured.

The separating body 60 of the invention is in an inverted cone structure, the top surface of the inverted cone is connected with the reaction zone 63, the bottom surface of the inverted cone is connected with the drain pipe 61, the inlet volume flow is larger than the outlet overflow volume flow, and the structure improves the separation efficiency. The drain pipe 61 connected with the water outlet of the separating body 60 is provided with an inverted U-shaped pipe section, the top of the inverted U-shaped pipe section is flush with the top surface of the separating body 60, and the design avoids the materials in the reaction tower body 59 from flowing back to the drain pipe 61. The water outlet of the water discharge pipe 61 is connected with the methanol purification working section, further purification can be carried out, and the obtained pure methanol can be rapidly recycled.

The two ends of the reaction zone 63 of the present invention are respectively provided with a first filter screen 71 and a second filter screen 72 for preventing the solid acid catalyst 64 from flowing out, the first filter screen 71 and the second filter screen 72 have the same structure, the diameter of the first filter screen 71 is consistent with the inner diameter of the reaction zone 63, and the diameter of the filter hole is smaller than the diameter of the solid acid catalyst 64. The first and

second sieves

71 and 72 can respectively intercept the solid acid catalyst 64 flowing into the liquid discharge region 62 and the separating body 60, so as to reduce the loss of the solid acid catalyst 64, and have more efficient productivity compared with the conventional biodiesel reaction tower.

The bottom of the reaction zone 63 of the present invention is provided with a feed inlet 67 for feeding a mixture of high purity fatty acid and methanol, respectively, the feed inlet 67 is connected to an external feed pipe 68, and the external feed pipe 68 is connected to the first static mixer 14 or the second static mixer 18 of the previous working condition. The bottom of the reaction area 63 is provided with a feeding distribution disc 69 communicated with the feeding port 67 and used for uniform feeding, the feeding distribution disc 69 is uniformly provided with feeding distribution holes 70, the mixture of the high-purity fatty acid and the methanol enters the feeding distribution disc 69 communicated with the feeding port 68 through the feeding pipe 68, and uniform distribution is realized in the reaction area 63 through the feeding distribution holes 70. The side wall of the liquid discharge area 62 is provided with a discharge port 73 for discharging the products, the discharge port 73 is connected with the product collection section, and the products are collected in the product collection section and enter the subsequent biodiesel refining and purification.

The top of the liquid discharge area 62 of the present invention is respectively provided with a pressure regulating valve 74 for regulating the pressure of the internal medium and a safety valve 75 for protecting the safety of the system. The reaction pressure of the medium in the reaction tower body 59 is normal pressure, and the pressure regulating valve 74 can stably control the interior to be at the reaction normal pressure, so that the normal reaction is ensured. If the pressure of the internal medium exceeds the specified safety value, the safety valve 75 is opened to discharge a part of gas or fluid in the system into the atmosphere, so that the pressure of the system does not exceed the specified safety value, and the system is ensured not to have an accident due to overhigh pressure. The safety valve 75 is an automatic valve and must be used after pressure testing.

The three-phase separator 5, the membrane separator 8, the spray dryer, the transfer pumps, the vacuum pump 16, the liquid level meter 55, the valves, the propeller stirrer 431, the view mirror 432, the heating coil 433, the steam heaters, the static mixer, the liquid booster 16, the submersible propeller stirrer, the pressure regulating valve 74 and the safety valve 75 used in the present invention are all known electrical devices and can be purchased and used directly on the market, and the structure, the circuit and the control principle thereof are known technologies, so the structure, the circuit and the control principle of the three-phase separator 5, the membrane separator 8, the spray dryer, the transfer pumps, the vacuum pump 16, the liquid level meter 55, the valves, the propeller stirrer 431, the view mirror 432, the heating coil 433, the steam heaters, the static mixer, the liquid booster 16, the submersible propeller stirrer, the pressure regulating valve 74 and the safety valve 75 are not described herein again.

The invention relates to a production method of a system for producing biodiesel on a large scale by using low-acid-value waste cooking oil, which comprises the following steps of:

step A: after the low-acid-value waste cooking oil in the grease cache tank, the hydrolase in the hydrolase cache tank and the pure water in the pure water cache tank enter the enzyme hydrolysis tank to be uniformly mixed, grease hydrolysis reaction is carried out to generate product fatty acid, byproduct glycerol and other mixtures, and the volume ratio of grease to water in the reaction condition is 6:4, the mass of the hydrolase is 5 percent of the weight of the grease, the hydrolysis pressure is normal pressure, the hydrolysis temperature is 55 ℃, and the hydrolysis time is 48 hours;

and B: conveying and separating the fatty acid product in the step A through a fatty acid conveying pipe, pressurizing to 0.4MPa by a fourth conveying pump, preheating by a steam heater, and entering a primary spray dryer for primary spray drying to obtain a primary fatty acid dried product, wherein the drying pressure is-0.088 MPa, and the drying temperature is 120 ℃;

and C: b, feeding the fatty acid primary dried product in the step B into a secondary spray dryer for secondary spray drying to obtain high-purity fatty acid, wherein the drying pressure is-0.088 MPa, and the drying temperature is 120 ℃;

step D: conveying and separating the byproduct glycerol and other mixtures in the step A into a three-phase separator through a reactant conveying pipe, separating out residues, residual oil and a water-enzyme-glycerol mixed solution, wherein the residues are collected into a residue pool, and the oil is collected into an oil tank;

step E: d, enabling the water-enzyme-glycerol mixed solution in the step D to enter a membrane separator, and separating and filtering again to obtain a byproduct glycerol and a water-enzyme mixed solution, wherein the byproduct glycerol is collected into a phase collection tank, and the water-enzyme mixed solution is collected into a clear phase collection tank;

step F: c, heating the high-purity fatty acid in the step C to 110-120 ℃ by using a first raw material steam heater, and then fully mixing the high-purity fatty acid with liquid methanol heated to 55 ℃ by using a first methanol steam heater in a first static mixer to obtain a raw material mixture;

g: the raw material mixture in the step F enters a first reaction tower for a first catalytic reaction to obtain a primary reaction product, namely the biodiesel with low purity, wherein the catalytic conditions are normal pressure and 110 ℃, and the solid acid catalyst is sulfuric acid/titanium dioxide SO ₄ ^2- /TiO ₂ A catalyst;

step H: regulating the primary reaction product in the step G to micro positive pressure by a liquid supercharger, heating to 110-120 ℃ by a second raw material steam heater, and fully mixing with liquid methanol heated to 55 ℃ by a second methanol steam heater in a second static mixer to obtain a second mixture;

step I: the second mixture in the step H enters a second reaction tower for a second catalytic reaction to obtain a second-stage reaction product, namely the biodiesel with extremely high purity, under the catalytic conditions of normal pressure and 110 ℃, and the solid acid catalyst is sulfuric acid/titanium dioxide SO ₄ ^2- /TiO ₂ A catalyst.

Finally, it should be noted that: the above embodiments are only preferred embodiments of the present invention to illustrate the technical solutions of the present invention, but not to limit the technical solutions, and certainly not to limit the scope of the present invention; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention; that is, the technical problems to be solved by the present invention are still consistent with the present invention, and all the modifications or changes made without substantial meaning in the spirit and scope of the present invention should be included in the protection scope of the present invention; in addition, the technical scheme of the invention is directly or indirectly applied to other related technical fields, and the technical scheme is included in the patent protection scope of the invention.

Claims

1. A system for producing biodiesel on a large scale by using low-acid-value waste cooking oil is characterized by comprising a pretreatment system for carrying out enzyme hydrolysis treatment on the low-acid-value waste cooking oil to obtain hydrolyzed fatty acid and a solid acid catalysis system which is connected from the pretreatment system and is used for generating fatty acid methyl ester by carrying out solid acid catalysis on the hydrolyzed fatty acid;

the pretreatment system comprises a grease cache tank (1), a hydrolase cache tank (2), a pure water cache tank (3), an enzyme hydrolysis tank (4) for grease hydrolysis reaction, which is respectively connected from the grease cache tank (1), the hydrolase cache tank (2) and the pure water cache tank (3), a spray dryer for drying product fatty acid, and a three-phase separator (5) for separating reaction mixture, which are respectively connected from the enzyme hydrolysis tank (4), a residue pool (6) for collecting reaction residues, a grease tank (7) for collecting unreacted grease, and a membrane separator (8) for separating oil from water, which are respectively connected from the three-phase separator (5), and a clear phase collection tank (9) for collecting water enzyme liquid and a concentrated phase collection tank (10) for collecting glycerol, which are respectively connected from the membrane separator (8); the spray dryer comprises a primary spray dryer (11) connected with the enzyme hydrolysis tank (4), and a secondary spray dryer (12) connected with the primary spray dryer (11).

2. The system for mass production of biodiesel from low-acid-value waste cooking oil as claimed in claim 1, wherein the solid acid catalysis system comprises a first static mixer (14) for mixing and reacting fatty acid and methanol, which is respectively connected from the secondary spray dryer (12) and the liquid methanol buffer tank (13), a first reaction tower (15) connected from the first static mixer (14), a liquid pressurizer (16) for regulating pressure of the primary reaction product, which is connected from the first reaction tower (15), a second raw material steam heater (17) for heating the primary reaction product, which is connected from the liquid pressurizer (16), a second static mixer (18) for mixing the primary reaction product and methanol, which is respectively connected from the liquid methanol buffer tank (13) and the second raw material steam heater (17), and a second reaction tower (19) connected from the second static mixer (18); the first reaction tower (15) is connected with a methanol recovery section, and the second reaction tower (19) is connected with a liquid methanol cache tank (13);

a high-purity fatty acid conveying pipe (20) is arranged between the first static mixer (14) and the second-stage spray dryer (12), and a first raw material steam heater (21) for heating the high-purity fatty acid is arranged on the high-purity fatty acid conveying pipe (20); a first liquid methanol delivery pipe (22) is arranged between the first static mixer (14) and the liquid methanol cache tank (13), and a first methanol steam heater (23) for preheating methanol is arranged on the first liquid methanol delivery pipe (22); a second liquid methanol delivery pipe (24) is arranged between the second static mixer (18) and the liquid methanol buffer tank (13), and a second methanol steam heater (25) for preheating methanol is arranged on the second liquid methanol delivery pipe (24).

3. The system for mass production of biodiesel from low-acid-value waste cooking oil according to claim 1, wherein the enzymatic hydrolysis tank (4) comprises an enzymatic hydrolysis tank body (41) and a circulating mechanism arranged on the enzymatic hydrolysis tank body (41) and used for circulating hydrolysis; circulation mechanism includes the main drain pipe of circulation (42) that connects out from the enzyme hydrolysis jar body (41) bottom, and branch circulating line (44) of first branch circulating line (43) and second that connect out from the main drain pipe of circulation (42) respectively, first branch circulating line (43) insert to the enzyme hydrolysis jar body (41) top, the second divides circulating line (44) to insert to the enzyme hydrolysis jar body (41) middle part, be equipped with first liquid valve (45) on the main drain pipe of circulation (42), be equipped with first circulating pump (49) on first branch circulating line (43), be equipped with second circulating pump (410) on the branch circulating line of second (44).

4. A system for mass production of biodiesel from low-acid-value waste cooking oil according to claim 3, wherein the top of the enzyme hydrolysis tank body (41) is provided with a first circulating liquid inlet pipe (46), a second circulating liquid inlet pipe (47) and a third circulating liquid inlet pipe (48) which are distributed in a shape like a Chinese character 'ji', and the first sub-circulating pipeline (43) is respectively connected with the first circulating liquid inlet pipe (46), the second circulating liquid inlet pipe (47) and the third circulating liquid inlet pipe (48); a first liquid inlet valve (411), a second liquid inlet valve (412) and a third liquid inlet valve (413) are respectively arranged on the first circulating liquid inlet pipe (46), the second circulating liquid inlet pipe (47) and the third circulating liquid inlet pipe (48);

a fourth circulating liquid inlet pipe (414), a fifth circulating liquid inlet pipe (415) and a sixth circulating liquid inlet pipe (416) are arranged in the middle of the enzyme hydrolysis tank body (41), a second sub-circulating pipeline (44) is respectively connected with the fourth circulating liquid inlet pipe (414), the fifth circulating liquid inlet pipe (415) and the sixth circulating liquid inlet pipe (416), the fourth circulating liquid inlet pipe (414), the fifth circulating liquid inlet pipe (415) and the sixth circulating liquid inlet pipe (416) are all distributed in a tangent mode with the cylindrical shell of the enzyme hydrolysis tank body (41), and a fourth liquid inlet valve (417), a fifth liquid inlet valve (418) and a sixth liquid inlet valve (419) are respectively arranged on the fourth circulating liquid inlet pipe (414), the fifth circulating liquid inlet pipe (415) and the sixth circulating liquid inlet pipe (416);

a circulating liquid outlet channel (420) is connected between the enzyme hydrolysis tank body (41) and the second sub-circulating pipeline (44), a first circulating liquid outlet pipe (421), a second circulating liquid outlet pipe (422) and a third circulating liquid outlet pipe (423) are arranged on the lower portion of the enzyme hydrolysis tank body (41), one end of the circulating liquid outlet channel (420) is respectively connected with the first circulating liquid outlet pipe (421), the second circulating liquid outlet pipe (422) and the third circulating liquid outlet pipe (423), the other end of the circulating liquid outlet channel is connected onto the second sub-circulating pipeline (44), the circulating liquid outlet channel (420) and an access point of the second sub-circulating pipeline (44) are positioned between the second circulating pump (410) and the circulating main liquid outlet channel (42), the first circulating liquid outlet pipe (421), the second circulating liquid outlet pipe (422) and the third circulating liquid outlet pipe (423) are respectively tangent to a cylindrical shell of the enzyme hydrolysis tank body (41), and a second circulating liquid outlet valve (424), a third liquid outlet valve (425) and a fourth liquid outlet valve (426) are respectively arranged on the first circulating liquid outlet pipe (421), the second circulating liquid outlet pipe (422) and the third circulating liquid outlet pipe (423).

5. A system for mass production of biodiesel from low-acid-value waste cooking oil as claimed in claim 3, wherein the top of the enzymatic hydrolysis tank (41) is provided with a grease inlet (427), and the grease inlet (427) is provided with a first input valve (428); a grease conveying pipe (26) is arranged between the grease inlet (427) and the grease cache tank (1), and a first conveying pump (27) and a first output valve (28) are respectively arranged on the grease conveying pipe (13);

a hydrolytic enzyme liquid inlet (429) is arranged at the top of the enzyme hydrolysis tank body (41), and a second input valve (430) is arranged at the hydrolytic enzyme liquid inlet (429); a hydrolase conveying pipe (29) is arranged between the hydrolase liquid inlet (429) and the hydrolase cache tank (2), and the hydrolase conveying pipe (21) is respectively provided with a second conveying pump (30) and a second output valve (31); a pure water delivery pipe (32) is arranged between the hydrolase liquid inlet (429) and the pure water cache tank (3), and the pure water delivery pipe (32) is respectively provided with a third delivery pump (33) and a third output valve (34);

a propeller type stirrer (431) for mixing oil and hydrolytic enzyme liquid is arranged in the enzyme hydrolysis tank body (41), a viewing mirror (432) for the condition of internal materials is arranged on the enzyme hydrolysis tank body (41), the enzyme hydrolysis tank body (41) is of a double-layer structure, and heating coils (433) for heating the internal materials are uniformly distributed in an interlayer of the enzyme hydrolysis tank body; the bottom of the enzyme hydrolysis tank body (41) is respectively connected with the primary spray dryer (11) through a fatty acid conveying pipe (35) and connected with the three-phase separator (8) through a reactant conveying pipe (36); a fourth delivery pump (37) and a steam heater (38) are respectively arranged on the fatty acid delivery pipe (35), and a fifth delivery pump (39) is arranged on the reactant delivery pipe (36).

6. The system for large-scale production of biodiesel by using low-acid-value waste cooking oil as claimed in claim 3, wherein the pretreatment system further comprises a vacuum pump (40), the top of the primary spray dryer (11) is connected with the vacuum pump (40) through a first exhaust pipe (50), the top of the secondary spray dryer (12) is connected with the vacuum pump (40) through a second exhaust pipe (51), a first exhaust valve (52) is arranged on the first exhaust pipe (50), and a second exhaust valve (53) is arranged on the second exhaust pipe (51);

the primary spray dryer (11) and the secondary spray dryer (12) have the same structure, arc-shaped baffles (54) are arranged at the inner tops of the primary spray dryer and the secondary spray dryer, and liquid level meters (55) are arranged on the outer walls of the primary spray dryer and the secondary spray dryer; a primary drying delivery pipe (56) is connected between the bottom of the primary spray dryer (11) and the top of the secondary spray dryer (12), a sixth delivery pump (57) is arranged on the primary drying delivery pipe (56), and a seventh delivery pump (58) is arranged on the high-purity fatty acid delivery pipe (20).

7. The system for producing biodiesel in large scale by using low-acid-value waste cooking oil as claimed in claim 2, wherein the first reaction tower (15) and the second reaction tower (19) have the same structure, and both comprise a reaction tower body (59) for reacting mixed materials, a separating body (60) which is communicated with the reaction tower body (59) and is of an integrated structure and used for separating out slag water, and a drain pipe (61) connected from the separating body (60), wherein the reaction tower body (59) is provided with a liquid discharge area (62) and a reaction area (63) which are communicated with each other from bottom to top;

the separation body (60) is the back taper structure, and the back taper top surface links to each other with reaction zone (63), and the back taper bottom surface links to each other with drain pipe (61), is equipped with the type of falling U pipeline section on drain pipe (61), and the type of falling U pipeline section top flushes with separation body (60) top surface mutually, and drain pipe (61) delivery port is connected with the methanol purification workshop section.

8. The system for mass production of biodiesel by using low-acid-value waste cooking oil as claimed in claim 7, wherein a solid acid catalyst (64) and a stirrer (65) for stirring materials in the reaction zone (63) are arranged in the reaction zone, and the stirrer (65) is a submersible plug-flow stirrer;

the bottom of the reaction zone (63) is respectively provided with a catalyst filling hole (66) for filling and discharging a solid acid catalyst (64) and a feeding hole (67) for inputting a mixed material, and the feeding hole (67) is connected with the first static mixer (3) or the second static mixer (8) through a feeding pipe (68);

the bottom of the reaction zone (63) is provided with a feeding distribution disc (69) which is communicated with the feeding port (67) and is used for uniform feeding, and feeding distribution holes (70) are uniformly distributed on the feeding distribution disc (69);

and a first filter screen (71) and a second filter screen (72) for preventing the solid acid catalyst (64) from flowing out are respectively arranged at two ends of the reaction zone (63), the first filter screen (71) and the second filter screen (72) have the same structure, the diameter of the first filter screen is consistent with the inner diameter of the reaction zone (63), and the diameter of the filter holes of the first filter screen is smaller than that of the solid acid catalyst (64).

9. The system for producing biodiesel in large scale by using low-acid-value waste cooking oil as claimed in claim 7, wherein a discharge port (73) for discharging products is formed in the side wall of the liquid discharge area (62), the discharge port (73) of the first reaction tower (15) is connected with the liquid supercharger (16), and the discharge port (73) of the second reaction tower (19) is connected with a product collection section;

the top of the liquid discharge area (62) is respectively provided with a pressure regulating valve (74) for regulating the pressure of an internal medium, a safety valve (75) for protecting the safety of a system and a methanol liquid outlet (76) for recycling methanol, the methanol liquid outlet (76) of the first reaction tower (15) is connected to a methanol recycling section, and the methanol liquid outlet (76) of the second reaction tower (19) is connected to a liquid methanol cache tank (13).

10. The production method of the system for producing biodiesel on a large scale by using low-acid-value waste cooking oil according to any one of claims 1 to 9, is characterized by comprising the following steps of:

step C: b, allowing the fatty acid primary dried product in the step B to enter a secondary spray dryer for secondary spray drying to obtain high-purity fatty acid, wherein the drying pressure is-0.088 MPa, and the drying temperature is 120 ℃;

step D: c, heating the high-purity fatty acid to 110-120 ℃ by a first raw material steam heater, and then fully mixing the high-purity fatty acid with liquid methanol heated to 55 ℃ by a first methanol steam heater in a first static mixer to obtain a raw material mixture;

and E, step E: the raw material mixture in the step F enters a first reaction tower to carry out a first catalytic reaction to obtain a primary reaction product, wherein the catalytic conditions are normal pressure and 110 ℃, and a solid acid catalyst is sulfuric acid/titanium dioxide SO ₄ ^2- /TiO ₂ A catalyst;

step F: regulating the primary reaction product in the step G to micro positive pressure by a liquid supercharger, heating to 110-120 ℃ by a second raw material steam heater, and fully mixing with liquid methanol heated to 55 ℃ by a second methanol steam heater in a second static mixer to obtain a second mixture;

g: the second mixture in the step H enters a second reaction tower for a second catalytic reaction to obtain the high-purity biodiesel, wherein the catalytic conditions are normal pressure and 110 ℃, and the solid acid catalyst is sulfuric acid/titanium dioxide SO ₄ ^2- /TiO ₂ A catalyst.