CN107236597B - Biodiesel transesterification real-time dynamic separation continuous reaction system and application thereof - Google Patents
Biodiesel transesterification real-time dynamic separation continuous reaction system and application thereof Download PDFInfo
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- CN107236597B CN107236597B CN201710533439.4A CN201710533439A CN107236597B CN 107236597 B CN107236597 B CN 107236597B CN 201710533439 A CN201710533439 A CN 201710533439A CN 107236597 B CN107236597 B CN 107236597B
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- 238000006243 chemical reaction Methods 0.000 title claims abstract description 92
- 239000003225 biodiesel Substances 0.000 title claims abstract description 73
- 238000000926 separation method Methods 0.000 title claims abstract description 56
- 238000005809 transesterification reaction Methods 0.000 title claims abstract description 33
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims abstract description 212
- 235000011187 glycerol Nutrition 0.000 claims abstract description 90
- 239000000463 material Substances 0.000 claims abstract description 20
- 239000007788 liquid Substances 0.000 claims abstract description 19
- 238000003756 stirring Methods 0.000 claims abstract description 16
- 239000000376 reactant Substances 0.000 claims abstract description 14
- 239000002994 raw material Substances 0.000 claims abstract description 8
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 78
- 239000003921 oil Substances 0.000 claims description 32
- 238000000034 method Methods 0.000 claims description 16
- 239000003054 catalyst Substances 0.000 claims description 15
- 230000008569 process Effects 0.000 claims description 14
- 239000002253 acid Substances 0.000 claims description 9
- 238000005886 esterification reaction Methods 0.000 claims description 9
- 238000005070 sampling Methods 0.000 claims description 9
- 239000003513 alkali Substances 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- 230000009471 action Effects 0.000 claims description 4
- 230000009467 reduction Effects 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 238000007599 discharging Methods 0.000 claims description 2
- 238000010438 heat treatment Methods 0.000 claims 1
- 238000004062 sedimentation Methods 0.000 claims 1
- 230000002441 reversible effect Effects 0.000 abstract description 11
- 230000001737 promoting effect Effects 0.000 abstract description 3
- 238000010977 unit operation Methods 0.000 abstract description 3
- 235000019198 oils Nutrition 0.000 description 23
- 239000000047 product Substances 0.000 description 15
- 239000004519 grease Substances 0.000 description 8
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 6
- 238000010924 continuous production Methods 0.000 description 5
- 240000000432 Pistacia chinensis Species 0.000 description 4
- 235000014123 Pistacia chinensis Nutrition 0.000 description 4
- 235000019484 Rapeseed oil Nutrition 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 230000032050 esterification Effects 0.000 description 4
- 235000012424 soybean oil Nutrition 0.000 description 4
- 239000003549 soybean oil Substances 0.000 description 4
- 230000008901 benefit Effects 0.000 description 3
- 239000006227 byproduct Substances 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 238000013459 approach Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000003915 air pollution Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000005388 borosilicate glass Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 238000011112 process operation Methods 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- 238000012800 visualization Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
- C11C—FATTY ACIDS FROM FATS, OILS OR WAXES; CANDLES; FATS, OILS OR FATTY ACIDS BY CHEMICAL MODIFICATION OF FATS, OILS, OR FATTY ACIDS OBTAINED THEREFROM
- C11C3/00—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom
- C11C3/04—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom by esterification of fats or fatty oils
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D21/00—Separation of suspended solid particles from liquids by sedimentation
- B01D21/02—Settling tanks with single outlets for the separated liquid
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
- B01F27/80—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a substantially vertical axis
- B01F27/90—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a substantially vertical axis with paddles or arms
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/0053—Details of the reactor
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L1/00—Liquid carbonaceous fuels
- C10L1/02—Liquid carbonaceous fuels essentially based on components consisting of carbon, hydrogen, and oxygen only
-
- C—CHEMISTRY; METALLURGY
- C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
- C11C—FATTY ACIDS FROM FATS, OILS OR WAXES; CANDLES; FATS, OILS OR FATTY ACIDS BY CHEMICAL MODIFICATION OF FATS, OILS, OR FATTY ACIDS OBTAINED THEREFROM
- C11C3/00—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom
- C11C3/04—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom by esterification of fats or fatty oils
- C11C3/10—Ester interchange
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/10—Biofuels, e.g. bio-diesel
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Organic Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
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- Wood Science & Technology (AREA)
- Liquid Carbonaceous Fuels (AREA)
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Abstract
The invention discloses a biodiesel transesterification real-time dynamic separation continuous reaction system, which comprises a plug flow reactor and a raw material conveying pipeline communicated with the plug flow reactor, wherein one side of the plug flow reactor is provided with a mixed liquid inlet, the raw material conveying pipeline comprises a material pump and a stirring and mixing kettle, one end of the material pump is communicated with the stirring and mixing kettle, the other end of the material pump is communicated with the plug flow reactor through the mixed liquid inlet, the plug flow reactor is a tubular reactor consisting of a plurality of pipelines, and one end of an even layer pipeline of the plug flow reactor is provided with a glycerine real-time dynamic separation device for separating glycerine from reactants. The invention integrates the biodiesel reaction and separation device into the same unit operation, so that the generation and separation of products are simultaneously carried out, and the equilibrium state of the reversible reaction is broken due to the real-time dynamic discharge of glycerol, thereby promoting the reversible reaction to be carried out towards the direction of biodiesel generation. This increases both the conversion rate of biodiesel and the conversion rate of biodiesel.
Description
Technical field:
the invention belongs to the technical field of biodiesel preparation, and particularly relates to a biodiesel transesterification real-time dynamic separation continuous reaction system and application thereof.
The background technology is as follows:
biodiesel is a clean renewable energy source and is a good quality petroleum diesel substitute. The great development of biodiesel has important strategic significance for sustainable development of economy, propulsion of energy substitution, environmental pressure relief and urban air pollution control.
At present, batch reaction technology is mainly adopted in industry, and the batch reaction technology has low production efficiency, high energy consumption, unstable product quality and poor scale benefit. The continuous production has the advantages of energy conservation, low cost and high production scale benefit, and is a trend of biodiesel industrial production at present.
Patent CN2015155701. X discloses a biodiesel continuous transesterification process, wherein methanol, an alkali catalyst, low acid value or waste grease after esterification are pumped into a continuous transesterification reactor, and materials coming out of the continuous transesterification reactor continuously enter a separator to separate glycerol and methanol, and the like, so that continuous production is realized. According to the biodiesel continuous esterification process disclosed in CN201510056722.3, firstly, waste grease, a catalyst and methanol are continuously injected into a continuous esterification reactor through a metering pump to carry out continuous esterification reaction, and discharged materials enter a continuous separator to separate the catalyst and transesterification materials with transesterification reaction, so that continuous esterification production of biodiesel produced by the waste grease is realized. The continuous production equipment of biodiesel disclosed in CN201220538026.8 comprises a mixer, a heater, a pipeline reactor, an esterification reaction tower, a glycerin separator and the like.
By searching for a continuous production device and a system for comparing the prior biodiesel, we can find that the method for preparing biodiesel by the continuous production device mainly comprises two processes of reaction and separation, and the two processes are usually completed by adopting different devices in different working sections, namely: the reaction is carried out in various forms of reactors, and the separation of the products is carried out in a separation device. That is to say: in the continuous biodiesel production process, biodiesel and glycerin are separated after the reaction is over and is close to equilibrium. The real-time dynamic separation of glycerol during the transesterification reaction was not performed simultaneously.
The invention comprises the following steps:
the invention aims to overcome the defects of the prior art and provide a biodiesel transesterification real-time dynamic separation continuous reaction system and application thereof.
The invention aims to provide a biodiesel transesterification real-time dynamic separation continuous reaction system which comprises a plug flow reactor and a raw material conveying pipeline communicated with the plug flow reactor, wherein one side of the plug flow reactor is provided with a mixed liquid inlet, the raw material conveying pipeline comprises a material pump and a stirring and mixing kettle for uniformly stirring raw materials, one end of the material pump is communicated with the stirring and mixing kettle, the other end of the material pump is communicated with the plug flow reactor through the mixed liquid inlet, the plug flow reactor is a tubular reactor consisting of a plurality of pipelines, one end of an even-layer pipeline of the plug flow reactor is provided with a glycerine real-time dynamic separation device for separating glycerine from reactants, the other end of the even-layer pipeline of the plug flow reactor is provided with a sampling point, the glycerine real-time dynamic separation device comprises an outer cylinder, an inner cylinder is sleeved in the outer cylinder, an annular channel is formed between the outer cylinder and the inner cylinder, the top of the inner cylinder is provided with a reactant feeding port, the reactant is connected to the middle position of the inner wall of the inner cylinder through a liquid distributor, the reactant is separated from the glycerine through the annular channel, the bottom of the inner cylinder is connected with the bottom of the next layer of pipeline, and the glycerine outlet is arranged.
The preparation process of the biodiesel is a reversible reaction process, so that if the glycerol is dynamically separated in real time in the reaction process, the byproduct glycerol in the reaction system is at a lower concentration level, the reaction is always in an unbalanced state, the positive reaction rate is always kept higher, the reverse reaction rate is inhibited due to the low concentration of the byproduct glycerol, and the reaction is accelerated, so that the conversion rate of the biodiesel is greatly improved.
The real-time dynamic separation device for the glycerol provided by the continuous reaction system for the real-time dynamic separation of the biodiesel transesterification realizes the real-time dynamic separation of the glycerol from the reaction system, so that the dynamic balance of the transesterification reaction process is broken, the reaction is facilitated to be carried out in the forward and reverse directions, the reaction efficiency is improved, and the conversion rate of the biodiesel is greatly improved.
Preferably, the height ratio of the outer cylinder to the inner cylinder is 8:7, and the diameter ratio of the outer cylinder to the inner cylinder is 5:4. In the invention, the bottom of the outer cylinder is connected with the glycerin outlet with the automatic control electric ball valve, and the glycerin outlet is provided with the automatic control ball valve, so that the amount of glycerin can be controlled in real time without the need of an operator to manually adjust the amount of glycerin. The outer cylinder can be made of high borosilicate glass to achieve the effect of visualization.
Preferably, the diameter ratio of the plug flow reactor pipeline to the outer cylinder is 1:5, and the length ratio is 10:1.
Preferably, the plug flow reactor tube has a length to diameter ratio of greater than 50.
Preferably, the sampling point and the glycerin outlet are controlled in an interlocking way. And the opening and closing sizes of the valves of the outlets of the glycerin real-time dynamic separation device are automatically regulated and controlled according to the conversion rate data measured by the corresponding sampling points of each layer, so as to ensure the separation balance.
Preferably, the plug flow reactor is placed in a constant temperature water bath. The plug flow reactor is placed in a constant temperature water bath, so that the reaction temperature can be ensured, and the esterification reaction can be smoothly carried out.
Preferably, the mixed liquor inlet and the glycerine real-time dynamic separation device are arranged on the same side of the plug flow reactor.
The invention further aims to provide an application of the biodiesel transesterification real-time dynamic separation continuous reaction system in esterification reaction.
Preferably, the raw oil is subjected to acid reduction pretreatment to ensure that the acid value of the raw oil is less than 2mgKOH/g, then the pretreated raw oil is preheated, the preheated raw oil and methanol are injected into a mixing and stirring reactor according to a certain proportion, a certain amount of alkaline catalyst is added, after the mixture is stirred uniformly, the mixture is pumped into a plug flow reactor by a material pump, the plug flow reactor is heated and the temperature is controlled at the transesterification reaction temperature, the methanol and the raw oil are subjected to gradual transesterification reaction in the propelling process in the plug flow reactor under the action of the liquid alkaline catalyst to generate biodiesel and glycerin, and the glycerin is settled in real time after flowing through a first glycerin real-time dynamic separation device and is discharged from a glycerin outlet; unreacted raw oil, methanol, biodiesel and alkali liquor flow through a first glycerol real-time dynamic separation device, then enter a next layer of plug flow reactor tube array, continue to carry out a pushing reaction, flow through a second group of glycerol real-time dynamic separation device, then settle glycerol in real time, and discharge the glycerol from a glycerol outlet; and the like until the reaction reaches equilibrium, and the biodiesel product obtained through the full reaction is discharged from a gas biodiesel outlet of the plug flow reactor.
In the invention, the raw oil is selected from more than one of rapeseed oil, soybean oil or pistacia chinensis bunge oil. The alkaline catalyst is KOH or NaOH.
Preferably, the mass ratio of the alkaline catalyst to the raw oil is 0.1-0.3:1, the molar ratio of the methanol to the raw oil is 6:1, and the reaction temperature is 65-67 ℃.
The beneficial effects of the invention are as follows:
1. in the real-time dynamic continuous reaction system provided by the invention, during biodiesel production, the materials uniformly mixed by the stirring and mixing kettle enter the plug flow reactor, and along with the progress of the reaction, the glycerol is dynamically separated and discharged by the real-time dynamic separation device; the unreacted grease continues to react with alkali and methanol solution in the plug flow reactor, and the glycerin is separated and discharged by a real-time separating device, and the like until the reaction is completed thoroughly.
2. The invention integrates the biodiesel reaction and separation device into the same unit operation, so that the generation and separation of products are simultaneously carried out, and the equilibrium state of the reversible reaction is broken due to the real-time dynamic discharge of glycerol, thereby promoting the reversible reaction to be carried out towards the direction of biodiesel generation. This increases both the conversion rate of biodiesel and the conversion rate of biodiesel.
Description of the drawings:
FIG. 1 is a schematic flow chart of the real-time dynamic separation continuous reaction of biodiesel transesterification of the invention;
FIG. 2 is a schematic top view of the plug flow reactor of examples 1 to 4;
FIG. 3 is a schematic diagram showing the structure of a plug flow reactor in examples 1 to 4;
FIG. 4 is a schematic cross-sectional view of the structure of FIG. 2 in the direction A;
FIG. 5 is a schematic cross-sectional view of the structure of FIG. 2 in the direction B;
reference numerals illustrate: 1. stirring and mixing the mixture in a kettle; 2. a material pump; 3. a plug flow reactor; 31. a mixed liquid inlet; 32. sampling points; 33. a crude biodiesel outlet; 4. a glycerin real-time dynamic separation device; 41. an outer cylinder; 42. an inner cylinder; 43. an annular channel; 44. reactant feed ports; 45. a liquid distributor; 46. and a glycerin outlet.
The specific embodiment is as follows:
the following examples are further illustrative of the invention and are not intended to be limiting thereof.
The equipment and materials mentioned in this invention are commercially available, unless otherwise specified. The plug flow reactor of fig. 1 is shown in top view. The number of plug flow reactor tubes or the number of layers may be determined according to the particular reaction.
As shown in fig. 1 to 5, the biodiesel transesterification real-time dynamic separation continuous reaction system comprises a stirring mixing kettle 1, a material pump 2 and a plug flow reactor 3 which are sequentially communicated, wherein one end of an even-layer pipeline of the plug flow reactor 3 is provided with a glycerine real-time dynamic separation device 4 for separating glycerine in reactants, and the other end of the even-layer pipeline is provided with a sampling point 32.
The plug flow reactor 3 is a tubular reactor with the length-diameter ratio larger than 50, the upper part of one side of the plug flow reactor 3 is provided with a mixed liquid inlet 31, and the bottom end is provided with a crude biodiesel outlet 33. The plug flow reactor 3 is placed in a constant temperature hot water bath.
The glycerin real-time dynamic separation device 4 is provided with an outer cylinder 41, an inner cylinder 42 is sleeved in the outer cylinder 41, and the height ratio of the outer cylinder 41 to the inner cylinder 42 is 8:7; the diameter ratio of the outer cylinder 41 to the inner cylinder 42 is 5:4, an annular channel 43 is formed between the outer cylinder 41 and the inner cylinder 42, a reactant feed port 44 with a motor ball valve is arranged at the top of the outer cylinder 41, and the reactant feed port is connected to the middle position of the inner wall of the outer cylinder 41 through a liquid distributor 45. The bottom of the outer cylinder 41 is connected with a glycerin outlet 46 with an automatically controlled electric ball valve. The outer cylinder 41 may be made of glass to achieve a visual effect.
The even layer pipelines of the plug flow reactor 3 are connected with a glycerin real-time dynamic separation device 4. The diameter ratio of the plug flow reactor 3 tube to the outer cylinder 41 is 1:5 and the length ratio is 10:1. The bottom of the outer cylinder 41 is connected with a glycerin outlet 46 with an automatic control electric ball valve, which can form interlocking with the sampling point 32, namely: the conversion rate data measured by the corresponding sampling points of each layer automatically regulates and controls the opening and closing of the valve of each glycerol outlet of the glycerol real-time dynamic separation device 4 so as to ensure the separation balance.
The biodiesel transesterification real-time dynamic separation continuous reaction system of the invention has the following working processes: the raw oil is subjected to acid reduction pretreatment to ensure that the acid value is less than 2mgKOH/g, the pretreated raw oil is preheated to 65-67 ℃, is injected into a stirring and mixing kettle 1 with methanol according to a certain proportion, is added with a certain amount of alkaline catalyst, is uniformly stirred, is fed into a plug flow reactor 3 by a material pump 2, is heated and is controlled to be at a transesterification reaction temperature by the plug flow reactor 3, anhydrous methanol and the raw oil are subjected to gradual transesterification reaction in the propelling process of the plug flow reactor 3 under the action of the liquid alkaline catalyst to generate biodiesel and glycerin, and the glycerin is settled in real time and discharged from a glycerin outlet after flowing through a first group of glycerin real-time dynamic separation devices; unreacted grease, methanol, biodiesel and alkali liquor flow through a first group of glycerin real-time dynamic separation devices, then enter a next layer of plug flow reactor tube array, continue to carry out a pushing reaction, flow through a second group of glycerin real-time dynamic separation devices, then settle glycerin in real time, and discharge the glycerin from a glycerin outlet; and the like until the reaction reaches equilibrium, and the biodiesel product obtained through the full reaction is discharged from the outlet of the plug flow reactor. In the process of preparing biodiesel by transesterification, the glycerol generated by the reaction is dynamically separated in real time, so that the byproduct glycerol in a reaction system is in a low concentration, the equilibrium state of the reversible reaction of the biodiesel is broken, the reversible reaction is promoted to proceed in the direction of generating the biodiesel, the reaction can be accelerated, the reaction is thorough, and the conversion rate of the biodiesel can be greatly improved.
The following examples illustrate the production of biodiesel with an annual yield of 3 ten thousand tons (mass flow per hour calculated as grease + methanol=4920kg):
an important process parameter of a plug flow reactor is the residence time, which is too short for the reaction to be completed; when the residence time is too long, methanol and glycerol can be layered in a pipeline in the transesterification reaction process, so that the mixing of the reaction solution is influenced, and the smooth progress of the reaction is influenced. The prior experiments of the inventor show that: at 17min residence time, the reaction efficiency of the reactants reached a maximum, indicating that: at this proper residence time, the flow in the tube remains turbulent, and the reactants are in a better mixing state and the reaction rate is better, so the residence time is 17min.
If the mass flow per hour is calculated as grease + methanol = 4920kg, using a pipe with a diameter of DN50 as a plug flow reactor pipe, then: the material flow rate was 0.77 m/s. The length of the plug flow reactor pipeline is as follows: 60 seconds x 17min x 0.77 m/s = 785.4m. If the plug flow single pipe is set to 3.5m, at least 785.4/3.5 m/root=224, and 223 elbows are provided. There are about 11 layers in each layer row of 20, 5 glycerin real-time dynamic separation devices are needed (the diameter ratio of the outer cylinder is 5×DN50=0.25m, the length ratio of the outer cylinder is 3.5 m/10=0.35 m), the height ratio of the outer cylinder to the inner cylinder is 8:7, and the diameter ratio is 5:4. The following specific process operations were performed under this plug flow reactor condition:
example 1:
the working process of the biodiesel transesterification real-time dynamic separation continuous reaction system is as follows:
(1) Mixing absolute methanol and KOH, adding the mixture into a stirring and mixing kettle, and fully mixing, wherein the molar ratio of the absolute methanol to the rapeseed oil is 6:1, and the mass ratio of the KOH to the rapeseed oil is 0.1;
(2) Feeding the above mixture into a tubular plug flow reactor at 67 ℃ through a feed pump at a flow rate of 0.77 m/s;
(3) Gradually performing transesterification reaction on anhydrous methanol and rapeseed oil under the action of KOH in the propelling process in a tubular plug flow reactor to generate biodiesel and glycerin, and settling the glycerin in real time and discharging from a glycerin outlet after the biodiesel and glycerin flow through a glycerin real-time dynamic separation device; unreacted grease, methanol, biodiesel and alkali liquor flow through a glycerine real-time dynamic separation device, then enter a next layer of plug flow reactor tube array, continue to carry out pushing reaction, flow through a second group of glycerine separator, then settle the glycerine in real time, and discharge the glycerine from a glycerine outlet; and so on until the reaction is finished, the biodiesel product obtained through the full reaction is discharged from the outlet of the plug flow reactor.
(4) The biodiesel is further subjected to static separation, neutralized by sulfuric acid (the addition amount is 0.1% of the mass of the biodiesel), filtered to remove impurities, and the excessive methanol is distilled off to obtain the biodiesel product.
The product conversion was determined to be about 98.3%.
Example 2:
the same as in example 1, except that:
the reaction temperature in the plug flow reactor is 65 ℃, naOH is adopted as the liquid alkaline catalyst, the raw oil is soybean oil, the weight ratio of NaOH to soybean oil is 0.3, and the molar ratio of anhydrous methanol to soybean oil is 6:1.
The product conversion was determined to be about 99.5% under these conditions.
Example 3:
the same as in example 1, except that:
the reaction temperature in the plug flow reactor is 65 ℃, KOH is adopted as the liquid alkaline catalyst, the raw oil is pistacia chinensis bunge oil, the weight ratio of KOH to pistacia chinensis bunge oil is 0.2, and the molar ratio of anhydrous methanol to pistacia chinensis bunge oil is 6:1.
The product conversion was determined to be about 99.3% under these conditions.
Example 4:
the same as in example 1, except that:
the reaction temperature in the plug flow reactor is 65 ℃, KOH is adopted as the liquid alkaline catalyst, raw oil is swill-cooked dirty oil subjected to acid reduction pretreatment, the acid value of the raw oil is less than 2mgKOH/g, the mass ratio of KOH to swill-cooked dirty oil is 0.2, and the molar ratio of anhydrous methanol to swill-cooked dirty oil is 6:1.
The product conversion was determined to be about 97.6% under this condition.
Comparative example 1:
the same as in example 1, except that: the biodiesel transesterification reaction is carried out in a plug flow reactor to approach the equilibrium, and then the biodiesel and the glycerin are separated, and the product conversion rate is 87% under the conditions of the same pipeline length, the same flow rate and the same residence time.
Comparative example 2:
the same as in example 1, except that: after transesterification reaction is carried out by adopting a kettle reactor to approach equilibrium, biodiesel and glycerin are separated, and the conversion rate of the product is 93% and the required reaction time is 45min.
By comparing comparative example 1 and comparative example 2 with examples 1 to 4, the product conversion rate of the biodiesel transesterification real-time dynamic separation continuous reaction system provided by the invention is far higher than that of the existing continuous biodiesel device for separating biodiesel from glycerol after the reaction is over and is close to equilibrium, and the reaction rate is higher and the time is shorter.
Therefore, the invention integrates the biodiesel reaction and separation device into the same unit operation, so that the generation and separation of products are simultaneously carried out, and the equilibrium state of the reversible reaction is broken due to the real-time dynamic discharge of the glycerol, thereby promoting the reversible reaction to be carried out towards the direction of generating the biodiesel. This increases both the conversion rate of biodiesel and the conversion rate of biodiesel.
The above description of the biodiesel transesterification real-time dynamic separation continuous reaction system and the application thereof provided by the invention is only used for helping to understand the technical scheme and the core idea of the invention, and it should be noted that, for those skilled in the art, several improvements and modifications can be made to the invention without departing from the principle of the invention, and the improvements and modifications also fall within the protection scope of the claims of the invention.
Claims (5)
1. The application of the biodiesel transesterification real-time dynamic separation continuous reaction system in the esterification reaction is characterized in that: the system comprises a piston flow reactor and a raw material conveying pipeline communicated with the piston flow reactor, wherein a mixed liquid inlet is formed in one side of the piston flow reactor, the raw material conveying pipeline comprises a material pump and a stirring mixing kettle for uniformly stirring raw materials, one end of the material pump is communicated with the stirring mixing kettle, the other end of the material pump is communicated with the piston flow reactor through the mixed liquid inlet, the piston flow reactor is a tubular reactor consisting of a plurality of pipelines, a real-time dynamic glycerol separation device for separating glycerol in a reactant is arranged at one end of an even-layer pipeline of the piston flow reactor, a sampling point is arranged at the other end of the even-layer pipeline, the real-time dynamic glycerol separation device comprises an outer cylinder, an inner cylinder is sleeved in the outer cylinder, an annular channel is formed between the outer cylinder and the inner cylinder, a reactant feeding hole is formed at the top of the inner cylinder, the inner cylinder is connected to the middle position of the inner wall through a liquid distributor, the reactant is separated from the glycerol through the annular channel, the bottom of the inner cylinder is connected with the pipeline of the next layer, and a glycerol outlet is formed at the bottom of the outer cylinder; the height ratio of the outer cylinder to the inner cylinder is 8:7, and the diameter ratio of the outer cylinder to the inner cylinder is 5:4; the diameter ratio of the plug flow reactor pipeline to the outer cylinder is 1:5, and the length ratio is 10:1; the length-to-diameter ratio of the plug flow reactor pipeline is greater than 50;
the application comprises the following steps: the method comprises the steps of (1) carrying out acid reduction pretreatment on raw oil to ensure that the acid value of the raw oil is less than 2mgKOH/g, preheating the pretreated raw oil, injecting the preheated raw oil and methanol into a mixing and stirring reactor according to a certain proportion, adding a certain amount of alkaline catalyst, stirring uniformly, feeding the raw oil into a plug flow reactor at a flow rate of 0.77 m/s by a material pump, heating the plug flow reactor, controlling the temperature at a transesterification reaction temperature, keeping the residence time of the mixture in the plug flow reactor for 17min, gradually carrying out transesterification reaction on the methanol and the raw oil in the propelling process of the plug flow reactor under the action of the liquid alkaline catalyst to generate biodiesel and glycerin, carrying out real-time sedimentation on the glycerin after flowing through a first glycerin real-time dynamic separation device, and discharging the glycerin from a glycerin outlet; unreacted raw oil, methanol, biodiesel and alkali liquor flow through a first glycerol real-time dynamic separation device, then enter a next layer of plug flow reactor tube array, continue to carry out a pushing reaction, flow through a second glycerol real-time dynamic separation device, then settle glycerol in real time, and discharge the glycerol from a glycerol outlet; and the like until the reaction reaches equilibrium, and the biodiesel product obtained through the full reaction is discharged from a gas biodiesel outlet of the plug flow reactor.
2. The use according to claim 1, characterized in that: the sampling point and the glycerin outlet are controlled in an interlocking way.
3. The use according to claim 1, characterized in that: the plug flow reactor is placed in a constant temperature water bath.
4. The use according to claim 1, characterized in that: the mixed liquid inlet and the glycerine real-time dynamic separation device are arranged on the same side of the plug flow reactor.
5. The use according to claim 1, characterized in that: the mass ratio of the alkaline catalyst to the raw oil is 0.1-0.3:1, the mol ratio of the methanol to the raw oil is 6:1, and the reaction temperature is 65-67 ℃.
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