CN111265904A

CN111265904A - Method for continuously dealcoholizing biodiesel byproduct crude glycerol

Info

Publication number: CN111265904A
Application number: CN202010237810.4A
Authority: CN
Inventors: 叶活动; 罗丹明; 罗敏健
Original assignee: LONGYAN ZHUOYUE NEW ENERGY DEVELOPMENT CO LTD
Current assignee: LONGYAN ZHUOYUE NEW ENERGY DEVELOPMENT CO LTD
Priority date: 2020-03-30
Filing date: 2020-03-30
Publication date: 2020-06-12

Abstract

The invention discloses a method for continuously dealcoholizing biodiesel byproduct crude glycerol, which comprises the following steps: firstly, crude glycerol is respectively subjected to two-stage steam heating at 50-60 ℃ and 75-90 ℃ in a rising film heater and a falling film heater, and then is cooled and buffered under the condition that the vacuum degree is 0.01-0.03 MPa to complete one-time vacuum separation and recover most of methanol; then, after the mixture is heated to 130-140 ℃ at a higher temperature of heat conduction oil circulation, the mixture is cooled and buffered to finish secondary vacuum separation and recovery of methanol after the glycerin drops carried in the mixture are removed by the filler in the evaporator under the condition of 0.04-0.06 MPa of vacuum degree; finally, the crude glycerol is vaporized again in the flash evaporator, under the condition of high vacuum degree of 0.07 MPa-0.09 MPa provided by a multistage vacuum pump, cooling and buffering are carried out to complete three times of vacuum separation and recovery of methanol, and the dealcoholized crude glycerol is discharged from the bottom of the flash evaporator. The invention has high automation degree, convenient and efficient operation and good dealcoholization effect.

Description

Method for continuously dealcoholizing biodiesel byproduct crude glycerol

Technical Field

The invention relates to a method for producing biodiesel, in particular to a method for continuously dealcoholizing crude glycerol which is a byproduct of the biodiesel.

Background

At present, the production of biodiesel generally adopts waste oil as raw material, and the main components of the waste oil are free fatty acid and triglyceride; free fatty acid in the waste oil is converted into fatty acid methyl ester (biodiesel) and water through esterification reaction, and after the water generated by the esterification reaction is removed, the triglyceride is converted into the biodiesel and the glycerol through ester exchange reaction. In order to improve the conversion rate of the ester exchange reaction, excessive methanol is required to participate in the ester exchange reaction, precipitation separation is carried out after the reaction is finished, most of the excessive methanol is dissolved in glycerin generated by the reaction, a mixture consisting of the methanol, part of biodiesel and the like and the glycerin is generally called as crude glycerin in the industry, and the crude glycerin contains 20-50% of the methanol, 10-20% of the biodiesel and other impurities according to the mass ratio. In production, the methanol in the crude glycerol is firstly separated and recovered, and then the biodiesel is separated and recovered. In the prior art, a method for removing methanol from crude glycerol is an intermittent method, a distillation kettle or a distillation tower device is generally adopted, namely, crude glycerol containing methanol and the like is conveyed into the distillation kettle or the distillation tower, the methanol is removed through heating, then the material is discharged, then the material is fed again, and the steps are repeated. The method has the defects of long operation time, low efficiency and poor effect.

Disclosure of Invention

The invention aims to provide a method for continuously dealcoholizing biodiesel byproduct crude glycerol, which has high automation degree, convenient and efficient operation and good dealcoholization effect.

In order to realize the aim, the method for continuously dealcoholizing the byproduct crude glycerol of the biodiesel comprises the following operation steps:

two-stage steam heating of crude glycerol: heating the crude glycerol to be dealcoholized to 50-60 ℃ by steam of a climbing film heater, and then sending the crude glycerol to a No. 1 falling film heater for steam heating again to 75-90 ℃;

(II) separating most methanol in vacuum at one time and recovering: most of methanol in the crude glycerol is vaporized after being heated in a No. 1 falling film heater due to lower boiling point of the methanol, the vaporized methanol is led out from the middle part of the No. 1 falling film heater under the condition of 0.01 MPa-0.03 MPa of vacuum degree, and methanol liquid cooled by a cooler enters a No. 1 buffer tank for recycling;

(III) circularly reheating the heat transfer oil: the material without most of methanol is pumped from the bottom of the No. 1 falling film heater to the No. 2 falling film heater for reheating, as most of methanol in the material is removed, in order to improve the methanol removal effect in the material, heat conduction oil with higher temperature than steam is adopted for heating in the No. 2 falling film heater, the heated material and vaporized methanol enter from the side surface of the lower part of the evaporator, and the material at the bottom of the evaporator is pumped to the No. 2 falling film heater for circularly heating to 130-140 ℃, and then enters from the side surface of the lower part of the evaporator;

and (IV) carrying out secondary vacuum separation on methanol and recovering: under the condition that the vacuum degree is 0.04-0.06 MPa, vaporized methanol in materials in the evaporator is led out from the top of the evaporator after glycerin drops carried by the vaporized methanol are removed by filler in the evaporator, and the cooled methanol liquid enters a No. 2 buffer tank for recycling;

and (V) separating methanol in vacuum for three times and recovering: and (3) pumping the material at the bottom of the evaporator into a flash evaporator, vaporizing the low-content methanol in the material again in the flash evaporator, feeding the methanol liquid cooled by the cooler into a No. 3 buffer tank for recycling under the condition of high vacuum degree of 0.07-0.09 MPa provided by a multistage vacuum pump, and discharging the dealcoholized crude glycerol from the bottom of the flash evaporator.

The method for continuously dealcoholizing the byproduct crude glycerol of the biodiesel has the following technical characteristics:

in order to improve the dealcoholization effect and efficiency of crude glycerol, a dealcoholization method of three groups of series devices is adopted under the condition of certain vacuum degree: firstly heating by steam, removing most of methanol in a No. 1 falling film heater, then circulating materials by a No. 2 pump in a No. 2 falling film heater and heating by heat transfer oil to improve the temperature of the materials, further removing the methanol in the materials, and finally removing the methanol by flash evaporation in a flash evaporator under the condition of higher vacuum degree. In order to improve the efficiency of removing methanol from crude glycerol, each group of devices is provided with a vacuum pump (wherein the third group is a multi-stage vacuum pump), and the vacuum degree provided by the vacuum pump can reduce the boiling point of methanol, accelerate the extraction of methanol and improve the efficiency of dealcoholization. The first group of devices adopts low vacuum dealcoholization because the dealcoholization amount of methanol is large; the second group adopts medium vacuum dealcoholization because the content of methanol in the materials is less, and the vacuum degree is higher than that of the first group; and in the third group, because the content of methanol in the material is less, flash evaporation dealcoholization under higher vacuum degree is adopted, so that the methanol removal effect is further improved.

The method for continuously dealcoholizing the biodiesel byproduct crude glycerol has the following beneficial effects:

1. continuous feeding and discharging dealcoholization, improved automation control capability, stable production and convenient operation.

2. The dealcoholization method adopting three groups of series devices has good dealcoholization effect and high efficiency.

3. The methanol content in the dealcoholized crude glycerol is low, the recovery rate of the methanol is obviously improved, and the production cost is greatly reduced.

Drawings

FIG. 1 is a schematic structural diagram of a production process system of a continuous dealcoholization method of biodiesel byproduct crude glycerol.

Reference numerals: the system comprises rising film heaters 1, a # 1 falling film heater 2, an evaporator 3, a # 2 falling film heater 4, a flash evaporator 5, a # 1 cooler 6, a # 2 cooler 7, a # 3 cooler 8, a # 1 buffer tank 9, a # 2 buffer tank 10, a # 3 buffer tank 11, a # 1 pump 12, a # 2 pump 13, a # 3 pump 14, a # 1 pump 15, a # 2 vacuum pump 16 and a multistage vacuum pump 17.

Detailed Description

The continuous dealcoholization method of biodiesel byproduct crude glycerol according to the present invention will be described in detail with reference to the accompanying drawings and embodiments.

As shown in FIG. 1, the method for continuously dealcoholizing the biodiesel byproduct crude glycerol comprises the following operation steps:

two-stage steam heating of crude glycerol: heating crude glycerol to be dealcoholized to 50-60 ℃ by steam in a rising film heater 1, and then sending the crude glycerol to a No. 1 falling film heater 2 for steam heating again to 75-90 ℃;

(II) separating most methanol in vacuum at one time and recovering: most of methanol in the crude glycerol is vaporized after being heated in the No. 1 falling film heater 2 due to low boiling point of the methanol, the vaporized methanol is led out from the middle part of the No. 1 falling film heater 2 under the condition that the vacuum degree of the vacuum pump 15 is 0.01 MPa-0.03 MPa, and the methanol liquid cooled by the No. 1 cooler 6 enters the No. 1 buffer tank 9 for recycling;

(III) circularly reheating the heat transfer oil: most of the materials after methanol removal are pumped out from the bottom of the No. 1 falling film heater 2 by a No. 1 pump 12 and sent to the No. 2 falling film heater 4 for reheating, as most of the methanol in the materials is removed, in order to improve the methanol removal effect in the materials, heat conduction oil with higher temperature than steam is adopted in the No. 2 falling film heater 4 for heating, the heated materials and vaporized methanol enter from the side surface of the lower part of the evaporator 3, and the materials at the bottom of the evaporator 3 are sent to the No. 2 falling film heater 4 by a No. 2 pump 13 for circularly heating to 130-140 ℃, and then enter from the side surface of the lower part of the evaporator 3;

and (IV) carrying out secondary vacuum separation on methanol and recovering: under the condition that the vacuum degree provided by a No. 2 vacuum pump 16 is 0.04 MPa-0.06 MPa, vaporized methanol in the materials in the evaporator 3 is led out from the top of the evaporator 3 after the glycerol drops carried in the materials are removed by the filler in the evaporator 3, and the methanol liquid cooled by a No. 2 cooler 7 enters a No. 2 buffer tank 10 for recycling;

and (V) separating methanol in vacuum for three times and recovering: the material at the bottom of the evaporator 3 is sent to the flash evaporator 5 through a 3# pump 14, the methanol with low content in the material is vaporized again in the flash evaporator 5, the methanol liquid cooled by the 3# cooler 8 enters a 3# buffer tank 11 for recycling under the condition that a multistage vacuum pump 17 provides high vacuum degree of 0.07 MPa-0.09 MPa, and the dealcoholized crude glycerol is discharged from the bottom of the flash evaporator 5.

The results of five tests carried out by the above method, the comparison of the crude glycerol methanol content before and after dealcoholization are shown in the following table:

as can be seen from the table above, the methanol content of the crude glycerol can be reduced from 30.5-46.3% to 0.8-1.5% by adopting the method for continuously dealcoholizing the biodiesel byproduct crude glycerol, and the dealcoholization effect is obvious.

Claims

1. A method for continuously dealcoholizing biodiesel byproduct crude glycerol is characterized by comprising the following steps: the operation steps are as follows: