CN115627197A

CN115627197A - Method and device for preparing fatty acid from waste oil

Info

Publication number: CN115627197A
Application number: CN202211345120.6A
Authority: CN
Inventors: 邱新金; 叶活动; 曾庆平; 李俊雄; 许权力
Original assignee: LONGYAN ZHUOYUE NEW ENERGY DEVELOPMENT CO LTD
Current assignee: LONGYAN ZHUOYUE NEW ENERGY DEVELOPMENT CO LTD
Priority date: 2022-10-31
Filing date: 2022-10-31
Publication date: 2023-01-20

Abstract

The invention discloses a method and a device for preparing fatty acid from waste grease, wherein three hydrolysis reactors are connected in series; feeding the waste oil and the process water after impurity removal according to the mass ratio of 1; waste grease and process water respectively enter a No. 3 hydrolysis reactor and a No. 1 hydrolysis reactor, the waste grease enters and goes out from the bottom and the process water enters and goes out from the top in each stage of reactor to form reverse contact reaction, crude fatty acid and sweet water are generated after the reaction, the crude fatty acid and the sweet water are respectively discharged from the upper part of the No. 1 hydrolysis reactor and the No. 3 hydrolysis reactor, the crude fatty acid and the sweet water are separated out again in respective layering tanks, and the crude fatty acid and the sweet water with lower water content are obtained after flash evaporation, so that good conditions are created for the next extraction process. The invention has the advantages of low production cost, convenient and efficient operation, wide application range and low equipment manufacturing and maintenance cost.

Description

Method and device for preparing fatty acid from waste oil

Technical Field

The invention relates to the technical field of a treatment method and a device for comprehensive utilization of waste oil, in particular to a method and a device for preparing fatty acid from waste oil.

Background

The waste oil is a general concept and is a general term for various inferior oils in life. Waste oils and fats can be classified into the following categories: the first is narrowly defined waste oil, namely oil obtained by simply processing and refining greasy floaters in a sewer or leftovers and leftovers (generally called swill) of hotels and restaurants; second, the inferior pork, pig viscera, pigskin process and produce the oil after refining; and thirdly, the oil used for frying the food is reused after the use frequency of the oil exceeds the specified requirement or the oil is reused after some new oil is added into the oil. The data show that: china annually produces two million tons of waste oil such as various acidified oil and waste oil in the catering industry. The main components of the waste oil are fatty acid and glyceride.

Fatty acid is an important oil chemical basic raw material. The downstream derivative produced by taking fatty acid as a raw material is widely applied to the fields of medicine, daily chemical industry, rubber and plastic processing and the like. There are two major routes to the industrial source of fatty acids: the first is natural oil hydrolysis and from papermaking waste liquid tall oil, and the second is from petrochemical raw materials to synthesize fatty acid. In recent years, on one hand, along with the attention of countries in the world on ecological environment and environmental protection, the protection and deforestation of natural forests lead to the annual decline of the yield of tall oil; on the other hand, the petroleum serving as a non-renewable resource is analyzed from long-term development trend, and the trend that the resource is in short supply, even exhausted and the price is gradually increased is an inevitable trend; the above two factors result in high price of raw materials for producing fatty acid.

The traditional fatty acid production process has the characteristics and the defects that:

hydrolyzing under normal pressure. Adding grease and a catalyst into a reaction kettle, heating in a mode of directly entering steam, reacting for 20-24 hours under the action of stirring, standing for layering, discharging bottom glycerol, supplementing the catalyst and a sulfuric acid aqueous solution again, and repeating the operation to ensure that the hydrolysis rate can reach 92-95%. The fatty acid has the production characteristics and the defects that the fatty acid belongs to intermittent operation, the operation is complicated, a catalytic assistant and a sulfuric acid aqueous solution are required to be added, the reaction needs to be stirred, the reaction needs to be stood for layering after the reaction is finished, the reaction time is long, the production efficiency is low, in addition, the raw material cost is high, the sulfuric acid corrosion resistance also needs to be considered for equipment materials, and the manufacturing cost is high.

High pressure hydrolysis. The grease is added into the reaction kettle, and the solubility of the grease in water is increased under the action of high temperature and high pressure, so that the reaction rate can be increased, and the hydrolysis rate is improved. The main technological parameters of the method are as follows: the operation temperature is 255-265 ℃, the operation pressure is 5.5-6.5 MPa, and the reaction time is 1-3 h. The high-pressure hydrolysis method has the advantages that the intermittent operation of normal-pressure hydrolysis is converted into continuous operation, the operation is convenient, the reaction time is short, no reaction catalyst is required to be added, the hydrolysis rate can reach 98%, but the raw material cost is high, the production cost is high due to the fact that 317 stainless steel materials are required for a reactor, the energy consumption is increased due to the fact that the reaction temperature is high (when the reaction temperature is higher than 260 ℃, side reaction is easy to occur to grease), the reaction raw materials are required (the high-pressure hydrolysis process is not suitable for grease containing more linolenic acid, conjugated double bonds, hydroxy acid and tetraene), and the applicability is influenced.

Disclosure of Invention

The invention aims to provide a method and a device for preparing fatty acid from waste oil, which have the advantages of low production cost, convenient and efficient operation, wide application range and low equipment manufacturing and maintenance cost.

In order to achieve the purpose, the method for preparing fatty acid from waste oil comprises the following operation steps:

(1) Removing impurities from waste oil mainly containing fatty acid and glyceride, heating by a waste oil feeding heater F2, and adding the waste oil from the side surface of the lower part of a No. 3 hydrolysis reactor C3 of a three-stage medium-pressure hydrolysis reactor connected in series by a waste oil feeding pump P4; meanwhile, according to the mass ratio of the waste oil and the process water after impurity removal being 1; then, respectively introducing high-pressure steam into the middle lower parts of the No. 1 hydrolysis reactor C1, the No. 2 hydrolysis reactor C2 and the No. 3 hydrolysis reactor C3 to heat the materials in the hydrolysis reactors; controlling the pressure in the reactor to be 3.5-4.0 MPa by two feeding pumps, and controlling the temperature in the reactor to be 230-250 ℃ by high-pressure steam;

(2) The waste grease and process water react in each stage of hydrolysis reactor to generate crude fatty acid and sweet water; the reaction pressure is 3.5MPa to 4.0MPa, the reaction temperature is 230 ℃ to 250 ℃, and the reaction time is 7 to 8 hours; the process water and the sweet water firstly enter the middle upper part of the No. 2 hydrolysis reactor C2 from the lower side surface of the No. 1 hydrolysis reactor C1 through the No. 1 magnetic conveying pump P2, and then enter the middle upper part of the No. 3 hydrolysis reactor C3 from the lower side surface of the No. 2 hydrolysis reactor C2 through the No. 2 magnetic conveying pump P3; the crude fatty acid automatically flows to the middle lower part of the No. 2 hydrolysis reactor C2 from the upper side surface of the No. 3 hydrolysis reactor C3, and then automatically flows to the middle lower part of the No. 1 hydrolysis reactor C1 from the upper side surface of the No. 2 hydrolysis reactor C2;

(3) Crude fatty acid flows out of the upper part of the No. 1 hydrolysis reactor C1 and enters a crude fatty acid layering tank V2, a large amount of crude fatty acid is positioned above a tank boundary level meter after layering, and a small amount of sweet water is positioned below the tank boundary level meter; sweet water flows into a sweet water layering tank V1 from the lower side surface of the No. 3 hydrolysis reactor C3, a small amount of crude fatty acid is positioned above a tank boundary level meter after layering, and a large amount of sweet water is positioned below the tank boundary level meter;

(4) Crude fatty acid on the boundary level meters of the crude fatty acid layering tank V2 and the sweet water layering tank V1 enter a crude fatty acid flash tank V4, and water can be reduced through flash evaporation so as to be beneficial to the next fatty acid extraction process; the sweet water under the level gauge in the tank automatically flows to a sweet water flash tank V3, and the moisture can be reduced after the flash evaporation, so that the next glycerol extraction process is facilitated.

The reaction formula of the glyceride and the process water for hydrolysis reaction to generate the fatty acid and the glycerol is as follows:

RCOOCH(RCOOCH2)2+3H2O＝＝＝3RCOOH+CHOH(CH2OH)2

the process water is deionized water obtained by desalting tap water; the sweet water is a discharged glycerol aqueous solution in which glycerol and water are mutually soluble in any proportion.

The device for preparing fatty acid from waste oil comprises a process water feed pump P1, a No. 1 magnetic transfer pump P2, a No. 2 magnetic transfer pump P3, a waste oil feed pump P4, a sweet water layering tank V1, a crude fatty acid layering tank V2, a sweet water flash tank V3, a crude fatty acid flash tank V4, a process water feed heater F1, a waste oil feed heater F2, a No. 1 hydrolysis reactor C1, a No. 2 hydrolysis reactor C2 and a No. 3 hydrolysis reactor C3; the inlet of the process water feeding heater F1 is connected with the outlet of a process water feeding pump P1, and the outlet of the process water feeding heater F1 is connected with one side of the middle upper part of the No. 1 hydrolysis reactor C1; an inlet of the waste grease feeding heater F2 is connected with an outlet of a waste grease feeding pump P4, and an outlet of the waste grease feeding heater F2 is connected with one side of the middle lower part of the No. 3 hydrolysis reactor C3; an inlet of the No. 1 magnetic conveying pump P2 is connected with the side surface of the lower part of the No. 1 hydrolysis reactor C1, an outlet of the No. 1 magnetic conveying pump P2 is connected with the middle upper part of the No. 2 hydrolysis reactor C2, and the middle lower part of the No. 1 hydrolysis reactor C1 is connected with the side surface of the upper part of the No. 2 hydrolysis reactor C2 through a pipeline; an inlet of the No. 2 magnetic conveying pump P3 is connected with the side surface of the lower part of the No. 2 hydrolysis reactor C2, an outlet of the No. 2 magnetic conveying pump P3 is connected with the middle upper part of the No. 3 hydrolysis reactor C3, and the middle lower part of the No. 2 hydrolysis reactor C2 is connected with the side surface of the upper part of the No. 3 hydrolysis reactor C3 through a pipeline; a side feed inlet of the sweet water layering tank V1 is connected with the lower side face of the hydrolysis reactor C3 through a pipeline, a side feed inlet of the crude fatty acid layering tank V2 is connected with the lower side face of the hydrolysis reactor C1 through a pipeline, a bottom outlet pipeline of the sweet water layering tank V1 and a bottom outlet pipeline of the crude fatty acid layering tank V2 are converged and then connected with a side inlet of the sweet water flash tank V3, and a bottom discharge outlet of the sweet water flash tank V3 is connected to a sweet water extraction process; the sweet water layering tank V1 and the crude fatty acid layering tank V2 are connected with the side inlet of the crude fatty acid flash tank V4 after being converged by a top outlet pipeline, and the bottom discharge port of the crude fatty acid flash tank V4 is connected to a fatty acid extraction process; the high-pressure steam pipeline is divided into three paths and is respectively connected into the reactors from the side surfaces of the middle lower parts of the No. 1 hydrolysis reactor C1, the No. 2 hydrolysis reactor C2 and the No. 3 hydrolysis reactor C3.

The three hydrolysis reactors connected in series are all in the following specifications: 1900mm internal diameter and 25000mm height to ensure a reaction time of more than 8h at full charge.

The sweet water layering tank V1 and the crude fatty acid layering tank V2 are both in the following specifications: the internal diameter is 1000mm, height 1500mm, set up 200mm mesh grid that height is 700mm in the jar.

The sweet water layering tank V1 and the crude fatty acid layering tank V2 are both provided with a boundary level meter to display the boundary level between the crude fatty acid and the sweet water.

The method and the device for preparing the fatty acid by the waste oil have the following technical characteristics and beneficial effects:

1. the traditional process takes pure natural grease or petrochemical raw materials as raw materials, so that the price is high, the cost is high, and the large-scale popularization and application are not facilitated; the invention uses the waste grease as the raw material, has wide application range and greatly low price of the raw material, ensures that the process is more suitable for industrial production, and has higher market competitiveness of the product price.

2. The raw materials are low in requirement, only simple impurity removal is needed, the hydrolysis can be directly carried out on grease without decoloring, deodorizing and other treatments, continuous production can be realized without adding a catalyst or biological enzyme catalysis in the reaction process, and the production operation is efficient.

3. On one hand, the waste grease is taken as the raw material, so that the illegal use of the waste grease flowing back to a dining table is avoided, the pollution of the waste grease to the environment is effectively reduced, and the requirement on the traditional raw material is reduced; on the other hand, the process belongs to a green clean renewable fatty acid production process.

4. Compared with the high-pressure hydrolysis in the prior art, the method has the advantages that the reaction temperature and pressure are obviously lower, and the energy consumption can be reduced.

5. The reactor is made of 316L materials, so that the manufacturing cost of the reactor is reduced.

6. A layering tank and a flash tank are respectively added at a crude fatty acid outlet and a sweet water discharge of the hydrolysis reactor, so that the load of the subsequent crude fatty acid and sweet water rectification process is reduced.

7. The scheme of connecting three hydrolysis reactors in series is adopted, oil and water are in reverse contact, the contact area of oil and water is increased, and the hydrolysis rate is improved.

Drawings

FIG. 1 is a schematic structural diagram of a device for preparing fatty acid from waste oil and fat in the invention.

Reference numerals: the device comprises a process water feeding pump P1, a magnetic transfer pump P2 No. 1, a magnetic transfer pump P3 No. 2, a waste grease feeding pump P4, a sweet water layering tank V1, a crude fatty acid layering tank V2, a sweet water flash tank V3, a crude fatty acid flash tank V4, a process water feeding heater F1, a waste grease feeding heater F2, a hydrolysis reactor C1 No. 1, a hydrolysis reactor C2 No. 2 and a hydrolysis reactor C3 No. 3.

Detailed Description

The method and apparatus for producing fatty acids from waste oils and fats according to the present invention will be described in further detail with reference to the accompanying drawings and embodiments.

As shown in fig. 1, the device for preparing fatty acid from waste oil of the present invention includes a process water feed pump P1, a magnetic transfer pump P2 No. 1, a magnetic transfer pump P3 No. 2, a waste oil feed pump P4, a sweet water stratification tank V1, a crude fatty acid stratification tank V2, a sweet water flash tank V3, a crude fatty acid flash tank V4, a process water feed heater F1, a waste oil feed heater F2, a hydrolysis reactor C1 No. 1, a hydrolysis reactor C2 No. 2, and a hydrolysis reactor C3 No. 3; the inlet of the process water feeding heater F1 is connected with the outlet of a process water feeding pump P1, and the outlet of the process water feeding heater F1 is connected with one side of the middle upper part of the No. 1 hydrolysis reactor C1; an inlet of the waste grease feeding heater F2 is connected with an outlet of a waste grease feeding pump P4, and an outlet of the waste grease feeding heater F2 is connected with one side of the middle lower part of the No. 3 hydrolysis reactor C3; the inlet of the No. 1 magnetic conveying pump P2 is connected with the side surface of the lower part of the No. 1 hydrolysis reactor C1, the outlet of the No. 1 magnetic conveying pump P2 is connected with the middle upper part of the No. 2 hydrolysis reactor C2, and the middle lower part of the No. 1 hydrolysis reactor C1 is connected with the side surface pipeline of the upper part of the No. 2 hydrolysis reactor C2; an inlet of the No. 2 magnetic conveying pump P3 is connected with the side surface of the lower part of the No. 2 hydrolysis reactor C2, an outlet of the No. 2 magnetic conveying pump P3 is connected with the middle upper part of the No. 3 hydrolysis reactor C3, and the middle lower part of the No. 2 hydrolysis reactor C2 is connected with the side surface of the upper part of the No. 3 hydrolysis reactor C3 through a pipeline; a side feed inlet of the sweet water layering tank V1 is connected with the lower side of the hydrolysis reactor C3 through a pipeline, a side feed inlet of the crude fatty acid layering tank V2 is connected with the lower side of the hydrolysis reactor C1 through a pipeline, a bottom outlet of the sweet water layering tank V1 and a bottom outlet of the crude fatty acid layering tank V2 are converged and then connected with a side inlet of the sweet water flash tank V3, and a bottom discharge outlet of the sweet water flash tank V3 is connected to a sweet water extraction process; the sweet water layering tank V1 and the crude fatty acid layering tank V2 are connected with the side inlet of the crude fatty acid flash tank V4 after being converged by a top outlet pipeline, and the bottom discharge port of the crude fatty acid flash tank V4 is connected to a fatty acid extraction process; the high-pressure steam pipeline is divided into three paths and is respectively connected into the reactors from the side surfaces of the middle lower parts of the No. 1 hydrolysis reactor C1, the No. 2 hydrolysis reactor C2 and the No. 3 hydrolysis reactor C3.

The three hydrolysis reactors connected in series have the following specifications: 1900mm of inner diameter and 25000mm of height so as to ensure that the reaction time is more than 8h when full load is fed; the specification of the sweet water layering tank V1 and the specification of the crude fatty acid layering tank V2 are as follows: the inner diameter is 1000mm, the height is 1500mm, and 200mm mesh grids with the height of 700mm are arranged in the tank; the sweet water stratification tank V1 and the crude fatty acid stratification tank V2 are each provided with a level gauge to show the level between the crude fatty acid and the sweet water.

The method for preparing fatty acid from waste oil comprises the following operation steps:

feeding the waste oil and process water after impurity removal according to the mass ratio of 1; the method comprises the following steps that three hydrolysis reactors, namely a hydrolysis reactor C1 No. 1, a hydrolysis reactor C2 No. 2 and a hydrolysis reactor C3 No. 3, are connected in series, waste oil and process water respectively enter a hydrolysis reactor C3 No. 3 and a hydrolysis reactor C1 No. 1, the waste oil and the waste water in each stage of reactor enter from top to bottom, the process water enters from top to bottom, reverse contact reaction is formed, crude fatty acid and sweet water are generated after reaction, the crude fatty acid and the sweet water are discharged from the upper portion of the hydrolysis reactor C1 No. 1 and the lower portion of the hydrolysis reactor C3 No. 3 respectively, the crude fatty acid and the sweet water are separated again after being layered in respective layering tanks, and the crude fatty acid and the sweet water with lower water content are obtained after flash evaporation through respective flash tanks, so that good conditions are created for the next extraction process.

Example 1

Pressurizing the purified grease to 3.0MPa at 10t/h, pressurizing the process water to 3.0MPa at 10t/h, heating the process water to 230 ℃, feeding the process water into a hydrolysis reactor, and directly introducing high-pressure steam into the hydrolysis reactor to maintain the reaction temperature; sampling and analyzing the crude fatty acid discharge of the No. 1 hydrolysis reactor C1 to obtain the hydrolysis rate of the hydrolyzed fatty acid of 95 percent and the water content of 1.2 percent; the crude fatty acid was sampled from the discharge of the crude fatty acid layering tank and analyzed, and the water content was 0.8%.

Example 2

Pressurizing the purified grease to 3.5MPa at 10t/h, pressurizing the process water to 3.5MPa at 10t/h, heating the process water to 235 ℃, feeding the process water into a hydrolysis reactor, and directly introducing high-pressure steam into the hydrolysis reactor to maintain the reaction temperature; sampling and analyzing the crude fatty acid discharge of the No. 1 hydrolysis reactor C1 to obtain the hydrolysis rate of the hydrolyzed fatty acid of 98 percent and the water content of 1.0 percent; the crude fatty acid was sampled from the discharge of the crude fatty acid stratification tank and analyzed for water content of 0.4%.

Example 3

Pressurizing the purified grease to 4.0MPa at 10t/h, pressurizing the process water to 4.0MPa at 10t/h, heating the process water to 240 ℃, feeding the heated process water into a hydrolysis reactor, and directly introducing high-pressure steam into the hydrolysis reactor to maintain the reaction temperature; sampling and analyzing the crude fatty acid discharge of the No. 1 hydrolysis reactor C1, wherein the hydrolysis rate of the hydrolyzed fatty acid is 98 percent, and the water content is 1.0 percent; the crude fatty acid was sampled from the discharge of the crude fatty acid layering tank and analyzed, and the water content was 0.3%.

Example 4

Pressurizing the purified grease to 4.5MPa at 10t/h, pressurizing the process water to 4.5MPa at 10t/h, heating the process water to 255 ℃, feeding the process water into a hydrolysis reactor, and directly introducing high-pressure steam into the hydrolysis reactor to maintain the reaction temperature; sampling and analyzing the discharge of the C1 crude fatty acid of the hydrolysis reactor No. 1 to obtain the hydrolysis rate of 98 percent and the water content of 1.3 percent, and sampling and analyzing the discharge of a crude fatty acid layering tank to obtain the water content of 0.5 percent.

The main specifications of the crude fatty acids obtained in the examples are given in the table below.

Item categories	Example 1	Example 2	Example 3	Example 4
					Percentage of hydrolysis%	95	98	98	98
The water content of the crude fatty acid before the layering tank is up to	1.2	1.0	1.0	1.3
					The water content of the crude fatty acid after the layering tank is up to	0.8	0.4	0.3	0.5
Combined effect	Is poor	Is preferably used	It is preferable that	In general terms

As can be seen, the hydrolysis rates and crude fatty acid water contents of the four examples are significantly better than the prior art atmospheric hydrolysis, comparable to the high pressure hydrolysis.

Comparing example 1, example 2, example 3 and example 4, it can be seen that the addition of the layering tank significantly reduces the water content in the crude fatty acid.

Comparing example 1 and example 2, it can be concluded that a suitable increase in reaction pressure and temperature helps to increase the rate of hydrolysis.

As can be seen from comparison of examples 3 and 4, the solubility of crude fatty acid in water increases with increasing reaction pressure and temperature, and it is not easy to separate oil from water.

Comparing example 2, example 3 and example 4, it can be seen that the heating temperature, i.e., the energy consumption, is the lowest for example 2 when the hydrolysis ratio is the same.

The best overall reaction result of example 3 is obtained by comparing example 1, example 2, example 3 and example 4.

Claims

1. A method for preparing fatty acid from waste oil is characterized by comprising the following steps: the operation steps are as follows:

(1) Removing impurities from waste oil mainly containing fatty acid and glyceride, heating by a waste oil feeding heater (F2), and adding the waste oil from the side surface of the lower part of a No. 3 hydrolysis reactor (C3) of a three-stage medium-pressure hydrolysis reactor connected in series by a waste oil feeding pump (P4); meanwhile, according to the mass ratio of the waste oil after impurity removal to the process water of 1; then, respectively introducing high-pressure steam into the middle lower parts of the No. 1 hydrolysis reactor (C1), the No. 2 hydrolysis reactor (C2) and the No. 3 hydrolysis reactor (C3) to heat materials in the hydrolysis reactors; controlling the pressure in the reactor to be 3.5-4.0 MPa by two feed pumps, and controlling the temperature in the reactor to be 230-250 ℃ by high-pressure steam;

(2) The waste oil and the process water react in each stage of hydrolysis reactor to generate crude fatty acid and sweet water; the reaction pressure is 3.5MPa to 4.0MPa, the reaction temperature is 230 ℃ to 250 ℃, and the reaction time is 7 to 8 hours; the process water and the sweet water firstly enter the middle upper part of the No. 2 hydrolysis reactor (C2) from the side surface of the lower part of the No. 1 hydrolysis reactor (C1) through the No. 1 magnetic conveying pump (P2), and then enter the middle upper part of the No. 3 hydrolysis reactor (C3) from the side surface of the lower part of the No. 2 hydrolysis reactor (C2) through the No. 2 magnetic conveying pump (P3); the crude fatty acid automatically flows to the middle lower part of the No. 2 hydrolysis reactor (C2) from the upper side surface of the No. 3 hydrolysis reactor (C3), and then automatically flows to the middle lower part of the No. 1 hydrolysis reactor (C1) from the upper side surface of the No. 2 hydrolysis reactor (C2);

(3) Crude fatty acid flows out of the upper part of the No. 1 hydrolysis reactor (C1) and enters a crude fatty acid layering tank (V2), a large amount of crude fatty acid is positioned above a tank boundary gauge after layering, and a small amount of sweet water is positioned below the tank boundary gauge; sweet water flows into a sweet water layering tank (V1) from the lower side surface of a No. 3 hydrolysis reactor (C3), a small amount of crude fatty acid after layering is positioned above a tank internal level meter, and a large amount of sweet water is positioned below the tank internal level meter;

(4) Crude fatty acid above the boundary level of the crude fatty acid layering tank (V2) and the sweet water layering tank (V1) enters a crude fatty acid flash tank (V4), and the moisture can be reduced by flash evaporation so as to be beneficial to the next fatty acid extraction process; the sweet water under the level gauge in the tank automatically flows to a sweet water flash tank (V3), and the moisture can be reduced after the flash evaporation, so that the next glycerol extraction process is facilitated.

2. An apparatus for realizing the method for preparing fatty acid from waste oil and fat as claimed in claim 1, which is characterized in that: the device comprises a process water feeding pump (P1), a magnetic conveying pump (P2) No. 1, a magnetic conveying pump (P3) No. 2, a waste oil feeding pump (P4), a sweet water layering tank (V1), a crude fatty acid layering tank (V2), a sweet water flash tank (V3), a crude fatty acid flash tank (V4), a process water feeding heater (F1), a waste oil feeding heater (F2), a hydrolysis reactor (C1) No. 1, a hydrolysis reactor (C2) No. 2 and a hydrolysis reactor (C3) No. 3; an inlet of the process water feeding heater (F1) is connected with an outlet of the process water feeding pump (P1), and an outlet of the process water feeding heater (F1) is connected with one side of the middle upper part of the No. 1 hydrolysis reactor (C1); an inlet of the waste grease feeding heater (F2) is connected with an outlet of a waste grease feeding pump (P4), and an outlet of the waste grease feeding heater (F2) is connected with one side of the middle lower part of the No. 3 hydrolysis reactor (C3); the inlet of the No. 1 magnetic conveying pump (P2) is connected with the side surface of the lower part of the No. 1 hydrolysis reactor (C1), the outlet of the No. 1 magnetic conveying pump is connected with the middle upper part of the No. 2 hydrolysis reactor (C2), and the middle lower part of the No. 1 hydrolysis reactor (C1) is connected with the side surface of the upper part of the No. 2 hydrolysis reactor (C2) through a pipeline; an inlet of the No. 2 magnetic conveying pump (P3) is connected with the side surface of the lower part of the No. 2 hydrolysis reactor (C2), an outlet of the No. 2 magnetic conveying pump is connected with the middle upper part of the No. 3 hydrolysis reactor (C3), and the middle lower part of the No. 2 hydrolysis reactor (C2) is connected with the side surface of the upper part of the No. 3 hydrolysis reactor (C3) through a pipeline; a side feed inlet of the sweet water layering tank (V1) is connected with the lower side of the hydrolysis reactor (C3) No. 3 through a pipeline, a side feed inlet of the crude fatty acid layering tank (V2) is connected with the lower side of the hydrolysis reactor (C1) No. 1 through a pipeline, a bottom outlet pipeline of the sweet water layering tank (V1) and a bottom outlet pipeline of the crude fatty acid layering tank (V2) are converged and then connected with a side inlet of the sweet water flash tank (V3), and a bottom discharge outlet of the sweet water flash tank (V3) is connected to a sweet water extraction process; the top outlet pipelines of the sweet water layering tank (V1) and the crude fatty acid layering tank (V2) are converged and then connected with the side inlet of the crude fatty acid flash tank (V4), and the bottom discharge port of the crude fatty acid flash tank (V4) is connected to a fatty acid extraction process; the high-pressure steam pipeline is divided into three paths and is respectively connected into the reactors from the side surfaces of the middle lower parts of the No. 1 hydrolysis reactor (C1), the No. 2 hydrolysis reactor (C2) and the No. 3 hydrolysis reactor (C3).

3. The apparatus for producing fatty acids from waste oils and fats according to claim 1, which is characterized in that: the specifications of the three hydrolysis reactors connected in series are as follows: an internal diameter of 1900mm and a height of 25000mm, to ensure a reaction time of more than 8h at full charge.

4. The apparatus for producing fatty acids from waste oils and fats according to claim 1, which is characterized in that: the sweet water layering tank (V1) and the crude fatty acid layering tank (V2) are both in specification: the internal diameter is 1000mm, height is 1500mm, and 200mm that the height is 700mm is set up in the jar 200mm.

5. The apparatus for producing fatty acids from waste oils and fats according to claim 1, which is the apparatus according to claim 2, wherein: the sweet water layering tank (V1) and the crude fatty acid layering tank (V2) are both provided with a boundary level meter to display the boundary level between the crude fatty acid and the sweet water.