阅读说明：本技术 一种废弃油脂的处理系统和处理方法 (Waste grease treatment system and treatment method ) 是由 钟民强 邓金华 鲁昊 陈梦楠 李进文 郭耿 刘震 于 2021-07-21 设计创作，主要内容包括：本发明公开一种废弃油脂的处理系统和处理方法,属于生物柴油技术领域。该系统,包括依次连通的废弃油脂罐、第一换热器、预处理塔、一级酯化反应釜和二级酯化反应釜；预处理塔包括塔筒和第一分布器；还包括甲醇酸罐、甲醇酸泵第一循环泵；第一循环泵与第一换热器的出料端连通,第一循环泵与第一分布器的进料端连通,第一循环泵与塔筒的底部出料口连通,甲醇酸泵与甲醇酸罐连通；还包括硫酸罐、硫酸罐分别与一级酯化反应釜和二级酯化反应釜连通。本发明还包括一种废弃油脂的处理方法,包括初级酯化反应、一级酯化反应和二级酯化反应。该系统实现了大幅度降低了硫酸的加入量的同时还可将酯化油的酸价降至1.11KOH/(mg/g)。(The invention discloses a treatment system and a treatment method for waste grease, and belongs to the technical field of biodiesel. The system comprises a waste grease tank, a first heat exchanger, a pretreatment tower, a primary esterification reaction kettle and a secondary esterification reaction kettle which are sequentially communicated; the pretreatment tower comprises a tower barrel and a first distributor; the system also comprises a methanolic acid tank and a methanolic acid pump first circulating pump; the first circulating pump is communicated with the discharge end of the first heat exchanger, the first circulating pump is communicated with the feed end of the first distributor, the first circulating pump is communicated with the discharge port at the bottom of the tower, and the methanolic acid pump is communicated with the methanolic acid tank; and the device also comprises a sulfuric acid tank and a second-stage esterification reaction kettle which are respectively communicated with the first-stage esterification reaction kettle and the second-stage esterification reaction kettle. The invention also discloses a method for treating the waste grease, which comprises a primary esterification reaction, a primary esterification reaction and a secondary esterification reaction. The system can greatly reduce the addition of sulfuric acid and simultaneously reduce the acid value of the esterified oil to 1.11 KOH/(mg/g).)

1. A waste grease treatment system is characterized by comprising a waste grease tank, a first heat exchanger, a pretreatment tower, a primary esterification reaction kettle and a secondary esterification reaction kettle which are sequentially communicated;

the pretreatment tower comprises a tower barrel and a first distributor, and the first distributor is arranged in the tower barrel;

the catalytic esterification system also comprises a methanolic acid tank, a methanolic acid pump and a first circulating pump; the first circulating pump is communicated with the discharge end of the first heat exchanger, the first circulating pump is communicated with the feed end of the first distributor, the first circulating pump is communicated with the bottom discharge hole of the tower drum, and the bottom discharge hole of the tower drum is positioned below the first distributor;

the feed end of the methanolic acid pump is communicated with the methanolic acid tank, and the discharge end of the methanolic acid pump is communicated with the pretreatment tower; the pretreatment tower is used for realizing the primary reaction of methanolic acid and waste grease;

the catalytic esterification system further comprises a sulfuric acid tank, and the discharge end of the sulfuric acid tank is communicated with the first-stage esterification reaction kettle and the second-stage esterification reaction kettle respectively.

2. The waste grease treatment system according to claim 1, further comprising a second circulation pump, wherein the top discharge port of the tower is communicated with the second circulation pump, the second circulation pump is communicated with the first-stage esterification reaction kettle, and the second circulation pump is used for realizing loop circulation esterification reaction in the first-stage esterification reaction kettle.

3. The waste grease treatment system according to claim 2, wherein the primary esterification reaction kettle comprises a first kettle body, a first grid plate and a second grid plate; the first grid plate and the second grid plate are arranged in the first kettle body, the first grid plate is arranged below the second grid plate, a side wall feeding port of the first kettle body is arranged between the first grid plate and the second grid plate, a side wall feeding port of the first kettle body is communicated with the second circulating pump, a side wall discharging port of the first kettle body is arranged below the first grid plate, and a side wall discharging port of the first kettle body is communicated with the second circulating pump.

4. The waste grease treatment system according to claim 2, further comprising a second heat exchanger, wherein the feed end of the second heat exchanger is communicated with the second circulating pump, and the discharge end of the second heat exchanger is communicated with the first kettle body.

5. The waste grease disposal system according to claim 1, wherein the secondary esterification reaction tank comprises a second tank body; a third grid plate and a fourth grid plate are sequentially arranged in the second kettle body from bottom to top; the third circulating pump is communicated with a side wall feeding hole between the third grid plate and the fourth grid plate, the third circulating pump is communicated with a side wall discharging hole below the fourth grid plate, and the third circulating pump is used for realizing loop circulating esterification reaction in the second-stage esterification reaction kettle.

6. The waste grease processing system according to claim 5, wherein the secondary esterification reaction kettle further comprises a second distributor which is positioned below the third grid plate, and the catalytic esterification system further comprises a methanol tank which is communicated with the feeding end of the second distributor.

7. The waste grease treatment system according to claim 5, further comprising a third heat exchanger, wherein the feed end of the third heat exchanger is communicated with the third circulating pump, and the discharge end of the third heat exchanger is communicated with the second kettle body.

8. The waste grease treatment system according to claim 3, wherein the primary esterification reaction kettle further comprises a third distributor, the third distributor is arranged in the first kettle body and above the second grid plate, and a top overflow port of the secondary esterification reaction kettle is communicated with a feed end of the third distributor.

9. The waste grease treatment system according to claim 1, wherein a fourth distributor is further arranged in the tower, the fourth distributor is located above the first distributor, and the bottom of the primary esterification reaction kettle is communicated with the feed end of the fourth distributor.

10. A method for treating waste grease is characterized by comprising the following steps:

preheating the waste oil to 65-75 ℃, and then mixing the waste oil with methanolic acid in a pretreatment tower for primary esterification reaction to obtain primary esterified oil;

carrying out primary esterification reaction on the primary esterified oil and sulfuric acid in a primary esterification reaction kettle at the temperature of 60-65 ℃ to obtain light-phase esterified oil and heavy-phase methanolic acid;

then conveying the heavy-phase methanolic acid to a pretreatment tower for primary esterification, carrying out secondary esterification on the light-phase esterified oil and sulfuric acid in a secondary esterification reaction kettle at the temperature of 60-65 ℃ to obtain the heavy-phase esterified oil and the light-phase methanolic acid, and conveying the light-phase methanolic acid to a primary esterification reaction kettle for primary esterification.

Technical Field

The invention relates to the technical field of biodiesel, in particular to a treatment system and a treatment method for waste grease.

Background

The vegetable oil and fat refining produces a large amount of soapstock which needs to be acidified and reduced into acidified oil by sulfuric acid and then comprehensively utilized. The biodiesel process by the low-temperature sulfuric acid catalytic esterification method at 60 ℃ can generate waste sulfuric acid water (the concentration of sulfuric acid is about 30 percent). The waste acid water can only be neutralized by calcium oxide generally, and after calcium sulfate is removed by filtration, the waste water enters a sewage treatment station, so that a large amount of sulfuric acid is lost; it can be seen that the prior art needs to introduce a large amount of sulfuric acid for the acid value reduction treatment of the waste oil and fat, and the waste of the sulfuric acid exists, and in addition, the acid value is difficult to be reduced to 3 KOH/(mg/g). The following.

Disclosure of Invention

The invention aims to overcome the technical defects and provide a waste oil treatment system and a waste oil treatment method, which solve the technical problems that in the prior art, a large amount of sulfuric acid is consumed for the acid value reduction treatment of waste oil, and the acid value is difficult to reduce to below 3 KOH/(mg/g).

In order to achieve the technical purpose, the technical scheme of the invention provides a waste grease treatment system which comprises a waste grease tank, a first heat exchanger, a pretreatment tower, a primary esterification reaction kettle and a secondary esterification reaction kettle which are sequentially communicated;

the pretreatment tower comprises a tower barrel and a first distributor, and the first distributor is arranged in the tower barrel;

the catalytic esterification system also comprises a methanolic acid tank, a methanolic acid pump and a first circulating pump; the first circulating pump is communicated with the discharge end of the first heat exchanger, the first circulating pump is communicated with the feed end of the first distributor, the first circulating pump is communicated with the bottom discharge hole of the tower drum, and the bottom discharge hole of the tower drum is positioned below the first distributor;

the feed end of the methanolic acid pump is communicated with the methanolic acid tank, and the discharge end of the methanolic acid pump is communicated with the pretreatment tower; the pretreatment tower is used for realizing the primary reaction of methanolic acid and waste grease;

the catalytic esterification system further comprises a sulfuric acid tank, and the discharge end of the sulfuric acid tank is communicated with the first-stage esterification reaction kettle and the second-stage esterification reaction kettle respectively.

And the top discharge hole of the tower is communicated with the second circulating pump, the second circulating pump is communicated with the first-stage esterification reaction kettle, and the second circulating pump is used for realizing loop circulating esterification reaction in the first-stage esterification reaction kettle.

Further, the primary esterification reaction kettle comprises a first kettle body, a first grid plate and a second grid plate; the first grid plate and the second grid plate are arranged in the first kettle body, the first grid plate is arranged below the second grid plate, a side wall feeding port of the first kettle body is arranged between the first grid plate and the second grid plate, a side wall feeding port of the first kettle body is communicated with the second circulating pump, a side wall discharging port of the first kettle body is arranged below the first grid plate, and a side wall discharging port of the first kettle body is communicated with the second circulating pump.

And the feeding end of the second heat exchanger is communicated with the second circulating pump, and the discharging end of the second heat exchanger is communicated with the first kettle body.

Further, the secondary esterification reaction kettle comprises a second kettle body; a third grid plate and a fourth grid plate are sequentially arranged in the second kettle body from bottom to top; the third circulating pump is communicated with a side wall feeding hole between the third grid plate and the fourth grid plate, the third circulating pump is communicated with a side wall discharging hole below the fourth grid plate, and the third circulating pump is used for realizing loop circulating esterification reaction in the second-stage esterification reaction kettle.

Further, the second-stage esterification reaction kettle further comprises a second distributor, the second distributor is located below the third grid plate, the catalytic esterification system further comprises a methanol tank, and the methanol tank is communicated with a feeding end of the second distributor.

The third heat exchanger is communicated, the feed end of the third heat exchanger is communicated with the third circulating pump, and the discharge end of the third heat exchanger is communicated with the second kettle body.

Further, the first-stage esterification reaction kettle further comprises a third distributor, the third distributor is arranged in the first kettle body and located above the second grid plate, and a top overflow port of the second-stage esterification reaction kettle is communicated with a feed end of the third distributor.

Further, a fourth distributor is further arranged in the tower barrel and located above the first distributor, and the bottom of the first-stage esterification reaction kettle is communicated with the feed end of the fourth distributor.

In addition, the invention also provides a method for treating the waste grease, which comprises the following steps:

preheating the waste oil to 65-75 ℃, and then mixing the waste oil with methanolic acid in a pretreatment tower for primary esterification reaction to obtain primary esterified oil;

carrying out primary esterification reaction on the primary esterified oil and sulfuric acid in a primary esterification reaction kettle at the temperature of 60-65 ℃ to obtain light-phase esterified oil and heavy-phase methanolic acid;

then conveying the heavy-phase methanolic acid to a pretreatment tower for primary esterification, carrying out secondary esterification on the light-phase esterified oil and sulfuric acid in a secondary esterification reaction kettle at the temperature of 60-65 ℃ to obtain the heavy-phase esterified oil and the light-phase methanolic acid, and conveying the light-phase methanolic acid to a primary esterification reaction kettle for primary esterification.

Compared with the prior art, the invention has the beneficial effects that: the temperature of the waste oil in the waste oil tank entering the pretreatment tower is controlled by the first heat exchanger, methanol acid is simultaneously input into the pretreatment tower, the raw material is subjected to a circulating loop esterification reaction under the action of the first circulating pump, the initial reduction of the acid value and the sedimentation removal of impurities in the raw material are realized, then an esterified oil mixture is subjected to twice acid value reduction with sulfuric acid in a sulfuric acid tank in a first-stage esterification reaction kettle and a second-stage esterification reaction kettle in sequence, the use amount of the sulfuric acid is controllable, the addition amount of the sulfuric acid is greatly reduced, meanwhile, esterified oil with a lower acid value is obtained, the addition amount of the sulfuric acid is reduced to 2.6%, and the acid value of the esterified oil can be reduced to 1.11 KOH/(mg/g).

Drawings

FIG. 1 is a schematic view of the structure of a catalytic esterification system for waste fats and oils according to example 1 of the present invention.

FIG. 2 is a schematic view of the pretreatment column in example 1 of the present invention.

FIG. 3 is a schematic view of the structure of a first-stage esterification reaction tank in example 1 of the present invention.

FIG. 4 is a schematic diagram showing the structure of a secondary esterification reaction tank in example 1 of the present invention.

Description of reference numerals: 1. a waste grease tank; 2. a first heat exchanger; 3. a pretreatment tower; 31. a tower drum; 32. a first distributor; 33. a fourth distributor; 4. a first-stage esterification reaction kettle; 41. a first kettle body; 42. a first grid plate; 43. a second grid plate; 44. a third distributor; 5. a second-stage esterification reaction kettle; 51. a second kettle body; 52. a third grid plate; 53. a fourth grid plate; 54. a second distributor; 6. a methanolic acid tank; 7. a first circulation pump; 8. a sulfuric acid tank; 9. a second circulation pump; 10. a second heat exchanger; 11. a third circulation pump; 12. a third heat exchanger; 13. an esterification oil pump; 14. an esterification oil tank; 15. a plate condenser; 16. a first metering pump; 17. a methanolic acid pump; 18. a second metering pump; 19. a third metering pump; 20. a fourth metering pump; 21. a methanol tank; 22. a fifth metering pump; 23. and a sixth metering pump.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

With reference to fig. 1-4, the present embodiment provides a catalytic esterification system for waste grease, which includes a waste grease tank 1, a first heat exchanger 2, a pretreatment tower 3, a first-stage esterification reaction kettle 4, and a second-stage esterification reaction kettle 5, which are sequentially communicated through a pipeline;

the pretreatment tower 3 comprises a tower 31 and a first distributor 32, wherein the first distributor 32 is arranged in the tower 31;

the catalytic esterification system further comprises a methanolic acid tank 6 and a methanolic acid pump 17, wherein a first circulating pump 7 is arranged in the first circulating pump 7, the first circulating pump 7 is communicated with the discharge end of the first heat exchanger 2, the first circulating pump 7 is communicated with the feed end of the first distributor 32, the first circulating pump 7 is communicated with the bottom discharge hole of the tower drum 31, and the bottom discharge hole of the tower drum 31 is positioned below the first distributor 32;

the feed end of the methanolic acid pump 17 is communicated with the methanolic acid tank 6, and the discharge end of the methanolic acid pump 17 is communicated with the pretreatment tower 3; the pretreatment tower 3 is used for realizing the primary reaction of the methanolic acid and the waste grease;

the catalytic esterification system also comprises a sulfuric acid tank 8, wherein the discharge ends of the sulfuric acid tank 8 are respectively communicated with the first-stage esterification reaction kettle 4 and the second-stage esterification reaction kettle 5.

Waste methanolic acid is introduced into a pretreatment tower 3 through a methanolic acid pump 17 by a methanolic acid tank 6, waste oil is preheated to about 70 ℃ by a first heat exchanger 2 by a waste oil tank 1 and enters a first distributor 32 to carry out loop circulation reaction under the action of a first circulating pump 7, the waste oil and the methanolic acid are subjected to preliminary reaction in the pretreatment tower 3 to realize preliminary deacidification, impurities are removed in the pretreatment tower 3, then the esterified oil mixture after the reaction is introduced into a primary esterification reaction kettle 4, sulfuric acid is introduced into the primary esterification reaction kettle 4 from a sulfuric acid tank 8 according to the amount of the sulfuric acid required by the esterification reaction, the sulfuric acid and the oil are subjected to primary esterification reaction to realize sedimentation and layering in the primary esterification reaction kettle 4, light-phase oil is positioned at the upper part, a reaction zone is positioned at the middle part, heavy-phase methanolic acid is positioned at the lower part to realize deacidification again, the light-phase oil positioned at the upper part flows out from an overflow outlet of the primary esterification reaction kettle 4 and enters a secondary esterification reaction kettle 5, and (2) introducing a certain amount of sulfuric acid into the secondary esterification reaction kettle 5 according to the requirement to continuously perform esterification reaction to realize secondary deacidification, sedimentation and layering, wherein the heavy-phase oil is positioned at the lower part, the reaction zone is positioned at the middle part, the light-phase methanolic acid is positioned at the upper part, and the acid value of the final oil can be reduced to below 1.5KOH/(mg/g) after three times of deacidification, and in addition, the sulfuric acid is introduced through two times of esterification reaction according to the reaction requirement, so that the use amount of the sulfuric acid is greatly reduced and is less than 3%.

On the basis of above-mentioned embodiment, this embodiment still includes second circulating pump 9, and the top discharge gate and the second circulating pump 9 intercommunication of tower section of thick bamboo 31, second circulating pump 9 and one-level esterification reaction cauldron 4 intercommunication, second circulating pump 9 are used for realizing the loop circulation esterification reaction in the circulation one-level esterification reaction cauldron 4. The second circulation pump 9 introduces the grease mixture in the tower 31 into the first-stage esterification reaction kettle 4, and circulates the materials in the first-stage esterification reaction kettle 4 to perform esterification reaction, so as to promote the reaction to be rapidly performed.

On the basis of the above embodiment, the primary esterification reaction kettle 4 of the present embodiment comprises a first kettle body 41, a first grid plate 42 and a second grid plate 43; first grid plate 42 and second grid plate 43 locate first cauldron body 41 in, first grid plate 42 is located the below of second grid plate 43, and first grid plate 42 and second grid plate 43 are located to the lateral wall feed inlet of first cauldron body 41 between, and the lateral wall feed inlet of first cauldron body 41 communicates with second circulating pump 9, and the below of first grid plate 42 is located to the lateral wall discharge gate of first cauldron body 41, and the lateral wall discharge gate of first cauldron body 41 communicates with second circulating pump 9. The mixture of the esterified oil is subjected to a first-stage esterification reaction in the middle area between the first grid plate 42 and the second grid plate 43, so that the acid reduction of the esterified oil is further realized, then the heavy-phase methanolic acid overflows to the upper part of the second grid plate 43 through the second grid plate 43, the esterified oil subjected to the acid reduction sinks to the lower part of the first grid plate 42 through the first grid plate 42, and the second circulating pump 9 promotes the circulation of the first-stage esterification reaction to improve the efficiency of the acid value reduction.

On the basis of the above embodiment, this embodiment further includes a second heat exchanger 10, the feed end of the second heat exchanger 10 is communicated with the second circulation pump 9, and the discharge end of the second heat exchanger 10 is communicated with the first kettle body 41. Part of the reactants in the first kettle body 41 are led into or out of the second heat exchanger 10 through the second circulating pump 9 and the second heat exchanger 10, so that the temperature in the first kettle body 41 is adjusted to be 60-65 ℃, and is preferably 62 ℃.

On the basis of the above embodiment, the second-stage esterification reaction kettle 5 of the present embodiment includes a second kettle body 51; third grid plate 52 and fourth grid plate 53 are arranged in second kettle 51 from bottom to top in proper order, and third circulating pump 11 is still included, third circulating pump 11 with be located the lateral wall feed inlet intercommunication between third grid plate 52 and fourth grid plate 53, third circulating pump 11 with be located the lateral wall discharge gate intercommunication of the below of fourth grid plate 53, third circulating pump 11 is used for realizing loop circulation esterification in second grade esterification reaction cauldron 5, second grade esterification reaction takes place between third grid plate 52 and fourth grid plate 53, the heavy phase esterification oil that generates subsides to the below of third grid plate 52 through third grid plate 52, light phase methanolic acid floats to the top of fourth grid plate 53 through fourth grid plate 53, realizes the separation of subsiding of esterification oil and methanolic acid.

On the basis of the above embodiment, the second-stage esterification reaction kettle 5 of the present embodiment further comprises a second distributor 54, the second distributor 54 is located below the third grating 52, the catalytic esterification system further comprises a methanol tank 21, and the methanol tank 21 is communicated with the feed end of the second distributor 54. The methanol tank 21 introduces methanol into the second distributor 54 to wash the heavy-phase esterified oil, and then floats upwards to the upper part of the fourth grid plate 53 to wash the heavy-phase esterified oil and separate and recover methanolic acid.

On the basis of the above embodiment, this embodiment further includes a third heat exchanger 12, the feed end of the third heat exchanger 12 is communicated with the third circulating pump 11, and the discharge end of the third heat exchanger 12 is communicated with the second kettle 51. The third circulating pump 11 introduces part of the reactants in the second kettle 51 into the third heat exchanger 12 for heating, and further adjusts the temperature in the second kettle 51 to 60-65 ℃, preferably 62 ℃.

On the basis of the above embodiment, the first-stage esterification reaction kettle 4 of this embodiment further includes a third distributor 44, the third distributor 44 is disposed in the first kettle body 41 and above the second grid plate 43, and the overflow outlet of the second-stage esterification reaction kettle 5 is communicated with the feed end of the third distributor 44. The floating light-phase methanolic acid after the second-stage esterification reaction in the second-stage esterification reaction kettle 5 flows out from the overflow outlet and enters the first-stage esterification reaction kettle 4 through the third distributor 44.

On the basis of the above embodiments, the tower 31 of this embodiment is further provided with a fourth distributor 33, the fourth distributor 33 is located above the first distributor 32, and the bottom of the first-stage esterification reaction kettle 4 is communicated with the feed end of the fourth distributor 33. Heavy-phase methanolic acid generated by the first-stage esterification reaction in the first esterification reaction kettle flows out from the bottom of the first-stage esterification reaction kettle 4, enters the tower drum 31 through the fourth distributor 33, and continuously participates in the primary esterification reaction in the tower drum 31.

On the basis of the above embodiment, the present embodiment further includes an esterification oil pump 13 and an esterification oil tank 14, where the esterification oil pump 13 is respectively communicated with the bottom of the secondary esterification reaction kettle 5 and the esterification oil tank 14, and the esterification oil pump 13 is used for conveying the esterified oil generated by the sedimentation of the secondary esterification reaction kettle 5 into the esterification oil tank 14.

On the basis of the above embodiments, the present embodiment further includes a plate condenser 15, where the plate condenser 15 is connected to the whole system for controlling the reaction temperature of the whole system, and the apparatus is a general apparatus in the art, and the detailed description of the operation principle is omitted here.

On the basis of the above embodiments, the first heat exchanger 2, the second heat exchanger 10, and the third heat exchanger 12 in the present embodiment are glass-lined tube heat exchangers.

On the basis of the above embodiment, the present embodiment further includes a first metering pump 16, the first metering pump 16 is respectively communicated with the waste grease tank 1 and the first heat exchanger 2, and the waste grease in the waste grease tank 1 is metered by the first metering pump 16 and transported to the first heat exchanger 2 to be heated to 65-75 ℃.

On the basis of the above embodiment, the material of the pretreatment tower 3 in this embodiment is 904L.

On the basis of the above embodiment, the present embodiment further includes a second metering pump 18, and the second metering pump 18 is respectively communicated with the sulfuric acid tank 8 and the first-stage esterification reaction kettle 4.

On the basis of the above embodiment, the present embodiment further comprises a third metering pump 19, and the third metering pump 19 is respectively communicated with the sulfuric acid tank 8 and the secondary esterification reaction kettle 5.

On the basis of the above embodiment, the present embodiment further includes a fourth metering pump 20, the fourth metering pump 20 is respectively communicated with the methanol tank 21 and the second distributor 54, and the fourth metering pump 20 is configured to introduce the methanol in the methanol tank 21 into the second distributor 54.

On the basis of the above embodiment, the present embodiment further includes a fifth metering pump 22, the fifth metering pump 22 is respectively communicated with the top overflow port of the second kettle 51 and the third distributor 44, and the fifth metering pump 22 is used for conveying the light phase methanolic acid in the second kettle 51 to the third distributor 44 and participating in the esterification reaction in the first kettle 41.

On the basis of the above embodiment, the present embodiment further includes a sixth metering pump 23, and the sixth metering pump 23 is respectively communicated with the bottom of the first-stage esterification reaction kettle 4 and the fourth distributor 33. The sixth metering pump 23 is used for conveying the heavy-phase methanolic acid in the first-stage esterification reaction kettle 4 to the fourth distributor 33.

The embodiment also comprises a method for treating the waste grease, which comprises the following steps:

preheating the waste oil to 65-75 ℃, and then mixing the waste oil with methanolic acid in a pretreatment tower 3 for primary esterification reaction to obtain primary esterified oil;

carrying out primary esterification reaction on the primary esterified oil and sulfuric acid in a primary esterification reaction kettle 4 at the temperature of 60-65 ℃ to obtain light-phase esterified oil and heavy-phase methanolic acid;

then, the heavy-phase methanolic acid is conveyed to a pretreatment tower 3 for primary esterification, the light-phase esterified oil and sulfuric acid are subjected to secondary esterification in a secondary esterification reaction kettle 5 at the temperature of 60-65 ℃ to obtain the heavy-phase esterified oil and the light-phase methanolic acid, and the light-phase methanolic acid is conveyed to a primary esterification reaction kettle 4 for primary esterification.

The treatment process of the waste oil and fat in the present embodiment is as follows:

the high acid value waste grease is metered by a metering pump, is heated to about 70 ℃ by temperature control through a first heat exchanger 2, is mixed with waste methanolic acid of a waste methanolic acid circulating pump, enters a pretreatment tower 3, the upper part of the pretreatment tower 3 is provided with a fourth distributor 33 for introducing the waste methanolic acid after primary esterification, the lower part is provided with a first distributor 32 which is beneficial to esterification of waste methanolic acid grease mixed liquid and separation of impurities, the grease treated by methanolic acid in the pretreatment tower 3 enters an inlet of a second circulating pump 9 through an overflow port at the top, catalyst sulfuric acid is metered by a precise second metering pump 18 (the addition amount of the sulfuric acid is generally 1.5-2.5 percent) and then is sent to an inlet of the second circulating pump 9, heavy phase acid-alcohol esterification reaction is carried out under the action of the second circulating pump 9, a first-stage esterification reaction kettle 4 consists of three parts, the lower part is a heavy phase methanolic acid separation zone, the middle part is a loop circulation esterification reaction zone, the upper part is an esterified oil light phase settling separation area, the lower part is separated from the middle part, the upper part is separated from the middle part by a grid plate, and the standing settling separation of the lower part and the upper part is not influenced by fluid shock waves of loop reaction in the middle part. The loop esterification reaction is controlled by constant temperature, and the fluid at the upper opening of the middle part passes through the second heat exchanger 10 to control the reaction temperature of 62 ℃. The lower heavy phase methanolic acid in the first-stage esterification reaction kettle 4 is introduced into a fourth distributor 33 of the pretreatment tower 3. The first stage esterification oil (acid value is generally controlled at about 25 KOH/(mg/g)) generated by the first esterification reaction kettle enters an inlet of a third circulating pump 11 through an overflow port, catalyst sulfuric acid is metered by a precision metering pump (the dosage of the sulfuric acid is generally 0.4-0.8 percent) and then is sent to the inlet of the third circulating pump 11, light-phase acid-alcohol esterification reaction is carried out under the action of the third circulating pump 11, the second stage esterification reaction kettle 5 consists of three parts, the lower part is a heavy-phase esterification oil separation zone, the middle part is a loop circulation esterification reaction zone, the upper part is a methanol acid light-phase settlement separation zone, the lower part is isolated from the middle part by a grid plate, and fluid shock waves of the loop reaction in the middle part do not influence the standing settlement separation zone of the lower part and the upper part. The loop esterification reaction is controlled by constant temperature, and the fluid at the upper opening of the middle part passes through the third heat exchanger 12 to control the reaction temperature at 62 ℃. The lower two-stage heavy phase esterified oil (the acid value is generally controlled below 1.5 KOH/(mg/g)) is fed into a fourth distributor 33 through methanol metered by a fourth metering pump 20 to wash the esterified oil (the dosage of the methanol is generally 15-25%), and then the esterified oil is metered by an esterification oil pump 13 and fed into an esterification oil tank 14. The second-stage esterification light-phase methanolic acid in the second kettle body 51 enters a pump through an overflow port and is fed into the third distributor 44 after being metered.

In the treatment process of the treatment system provided by the embodiment, the time of the pretreatment reaction is generally 0.5-1.5 hours; the dosage of the sulfuric acid introduced into the first-stage esterification reaction kettle 4 is 1.5-2.5%, the time of the first-stage esterification reaction is usually 1-3 hours, and the acid value after the first-stage esterification reaction is controlled to be 20-30 KOH/(mg/g); the dosage of the sulfuric acid introduced into the second-stage esterification reaction kettle 5 is 0.4-0.8%, the time of the second-stage esterification reaction is usually 1-3 hours, and the acid value of the second-stage esterification reaction is generally controlled to be 0.5-2 KOH/(mg/g).

And (4) related tests:

the processing system provided by the embodiment is used for processing waste grease with different acid values, the heating temperature of the first heater is 70 ℃, the time of the pretreatment reaction is 0.5 hour, the time of the first-stage esterification reaction is 2 hours and 62 ℃, the time of the second-stage esterification reaction is 2 hours and 62 ℃, and the usage amounts of sulfuric acid and methanol and the acid value change results are shown in table 1. It should be noted that the amount of methanol in table 1 includes the amount of methanol in methanolic acid, the amount of sulfuric acid includes the amount of sulfuric acid in methanolic acid, and the amount of sulfuric acid is supplemented to the amount in the following table according to the amount of sulfuric acid in first-stage esterification reaction kettle 4 and second-stage esterification reaction kettle 5. In addition, the methanolic acid is waste methanolic acid and mainly comprises methanol, water, sulfuric acid, pigment and water-soluble impurities.

TABLE 1 results of treating waste oils and fats by using the treating system of example 1

As can be seen from Table 1, the acid value of the waste oil and fat treated by the treatment system of this example was greatly reduced, and finally, it was as low as 1.11 KOH/(mg/g).

And (3) comparison test:

in addition, the invention also processes the above waste grease by prolonging the reaction time to 4 hours through the first esterification reaction, the reaction amount and condition are the same as the above test each component amount, but there is no second esterification reaction and related equipment, in addition, the sulfuric acid and methanol in the second esterification reaction are also added into the first esterification reaction kettle 4 correspondingly, for example, the amount of the sulfuric acid added in the first esterification reaction is 2% in the above test, the amount of the sulfuric acid added in the second esterification reaction is 0.6%, then the adding amount of the sulfuric acid in the first esterification reaction is 2.6% in the comparative test, the result is as shown in table 2.

TABLE 2 treatment results of waste oils and fats by primary esterification reaction only

As can be seen from Table 2, the acid value of the esterified oil of the waste oil treated by the primary esterification reaction and the related equipment is as high as 8.66KOH/(mg/g), which is significantly higher than that of the esterified oil treated by the treatment system of this embodiment.

The above-described embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.