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EP-4549539-B1 - CHEMICAL PRETREATMENT PROCESS FOR WASTE FAT, OIL AND GREASE

EP4549539B1EP 4549539 B1EP4549539 B1EP 4549539B1EP-4549539-B1

Inventors

  • JIANG, Lilong
  • HUANG, KUAN
  • CAO, Yanning
  • MA, Yongde
  • CAI, Zhenping

Dates

Publication Date
20260506
Application Date
20240329

Claims (9)

  1. A chemical pretreatment process for waste fat, oil and/or grease (FOG) comprising: S1, mixing a fresh methanol from a main pipeline from a boundary and a recycled ionic liquid from a catalyst recovery evaporation system to obtain a mixture, and then introducing the mixture into a catalyst preparation tank (V101); adding a fresh ionic liquid catalyst to the catalyst preparation tank (V101) and then stirring and dissolving to obtain a catalyst solution, and feeding out the catalyst solution through a catalyst conveying pump (P101A/B); mixing a recycled methanol from a methanol recovery tower (T101) with the waste FOG from the main pipeline from the boundary, followed by mixing with the catalyst solution, and then conveying to a static mixer (X101) through a pipeline and conducting mixing fully to obtain a mixed system; introducing the mixed system into a 1# esterification reactor (R101) and subjecting methanol and the waste FOG to esterification reaction under action of an ionic liquid catalyst at a preset reaction temperature and pressure to generate a fatty acid methyl ester and water; and introducing unreacted methanol, unreacted waste FOG and a crude product generated in the 1# esterification reactor (R101) into a 2# esterification reactor (R102) and continuing the esterification reaction to further generate the fatty acid methyl ester and water; S2, introducing a crude product obtained after the esterification reaction in the 2# esterification reactor (R102) to a filter (F101A/B) through a 2# external circulation pump (P103A/B); removing a solid impurity precipitated in the filter (F101A/B), and collecting the solid impurity into a solid-waste treatment and storage tank; introducing a filtered crude product into a chromatograph device (V102) and conducting oil-water two-phase separation to obtain an oil phase and an aqueous phase, wherein the oil phase mainly comprises a fatty acid methyl ester, methanol, water, and some unreacted waste FOG, and the aqueous phase mainly comprises methanol, an ionic liquid, and water generated by reactions; S3, introducing the oil phase product obtained by the oil-water separation in the chromatograph device (V102) into a crude product separation and evaporation system, and conducting flash evaporation to separate out methanol and a crude product by boiling point differences among water, methanol, and the fatty acid methyl ester; introducing a gas phase product obtained by the crude product separation and evaporation system, i.e., methanol and water into a subsequent methanol recovery system, and introducing the crude product containing the fatty acid methyl ester and partially unreacted waste FOG into a product storage tank through a crude product conveying pump (P104A/B); S4, introducing the aqueous phase product obtained by the oil-water separation in the chromatograph device (V102) into the catalyst recovery evaporation system, and conducting flash evaporation to separate out the ionic liquid, methanol, and water by boiling point differences among the ionic liquid, methanol, and water; introducing a gas phase product obtained by the catalyst recovery evaporation system, i.e., methanol and water into the subsequent methanol recovery system, returning most of the recovered ionic liquid catalyst to the catalyst preparation tank (V101), and introducing a deactivated ionic liquid into a waste catalyst recovery storage tank; and S5, cooling the methanol and water from the crude product separation and evaporation system and the catalyst recovery evaporation system into a liquid through a methanol condenser (E105), and introducing the liquid into a methanol storage tank (V105); pressurizing the liquid by a methanol feed pump (P105A/B), and then introducing the liquid into the methanol recovery tower (T101) and conducting distillation separation to obtain high-purity gas phase methanol at a tower top and wastewater at a tower bottom; cooling the high-purity gas phase methanol by a tower top cooler (E107) to obtain a methanol product, refluxing a part of the methanol product and conveying back a part of the methanol product to the 1# reactor (R101) by a reflux pump (P107A/B); and conveying the wastewater obtained at the tower bottom to a waste liquid recovery storage tank through a waste liquid discharge pump (P106A/B).
  2. The chemical pretreatment process for the waste FOG according to claim 1, wherein the crude product separation and evaporation system in step S3 comprises a 1# evaporator (E103) and a 1# gas-liquid separator (V103) disposed in series, and the catalyst recovery evaporation system in steps S1 and S4 comprises a 2# evaporator (E104) and a 2# gas-liquid separator (V104) disposed in series.
  3. The chemical pretreatment process for the waste FOG according to any preceding claim, wherein the ionic liquid catalyst in step S1 is a Bronsted acid protic ionic liquid prepared from a linear or heterocyclic tertiary amine compound and sulfuric acid, benzenesulfonic acid, or p-toluenesulfonic acid by one-step neutralization reaction.
  4. The chemical pretreatment process for the waste FOG according to any preceding claim, wherein in step S1, a mass ratio of reaction raw materials to the catalyst is in a range of waste FOG: methanol: catalyst of 1:(0.4 to 1.6):(0.05 to 0.50), the 1# esterification reactor (R101) and the 2# esterification reactor (R102) have an operating temperature of 60°C to 90°C, a reaction pressure of 0.1 MPa to 0.5 MPa, and a material residence time in both esterification reactors of 3 h to 5 h.
  5. The chemical pretreatment process for the waste FOG according to any preceding claim, wherein the chromatograph device (V102) in step S2 has an operating temperature of 40°C to 80°C, and an operating pressure of 0.1 MPa to 0.5 MPa.
  6. The chemical pretreatment process for the waste FOG according to any preceding claim, wherein in step S3, the crude product separation and evaporation system has an operating temperature of 105°C to 165°C, an operating pressure of 0.1 MPa to 0.5 Mpa; a low-pressure steam of a heating medium in the 1# evaporator (E103) has a temperature of 140°C to 180°C, and a pressure of 0.3 MPa to 0.8 Mpa; and a heated steam condensate is supplied to a previous esterification reaction section for providing heat; and in step S4, the catalyst recovery evaporation system has an operating temperature of 100°C to 160°C, and an operating pressure of 0.1 MPa to 0.5 MPa; a low-pressure steam of a heating medium in the 2# evaporator (E104) has a temperature of 140°C to 180°C, and a pressure of 0.3 MPa to 0.8 MPa; and a heated steam condensate is supplied to the previous esterification reaction section for providing heat.
  7. The chemical pretreatment process for the waste FOG according to any preceding claim, wherein in step S5, the methanol recovery tower (T101) has an operating pressure of 0.1 MPa to 0.5 MPa, an operating temperature at the tower top of 40°C to 80°C, an operating temperature at the tower bottom of 80°C to 120°C, and an operating reflux ratio of 1.0 to 5.0; a low-pressure steam of a heating medium at the tower bottom has a temperature of 100°C to 140°C, and a pressure of 0.1 MPa to 0.3 MPa; and a heated steam condensate is supplied to the previous esterification reaction section for providing heat.
  8. The chemical pretreatment process for the waste FOG according to any preceding claim, wherein the both esterification reactors in step S1 are stirred tank reactors internally provided with an inner coil heater and an external circulation heat exchanger (E101/E102) for heating, and a heating medium is a steam condensate from a subsequent working section; when the reaction is out of control and overtemperature occurs, a recycled water is added to reduce a temperature of the reaction through the external circulation heat exchanger (E101/E102), and a reaction pressure is controlled by supplementing a low-pressure nitrogen.
  9. The chemical pretreatment process for the waste FOG according to any preceding claim, wherein in order to prevent clogging from affecting normal operation, the filter connecting with the chromatograph device (V102) in step S2 is provided with two filter devices disposed in parallel, namely a first filter (F101A) and a second filter (F101B), one is put into normal use and the other is regularly back-flushed.

Description

TECHNICAL FIELD The present disclosure relates to the technical field of renewable energy, and in particular to a chemical pretreatment process for waste fat, oil and/or grease (FOG). BACKGROUND The vigorous development of biodiesel production projects not only meets the need to develop clean energy in China, but also fits the current national goal of "peak carbon dioxide emissions and carbon neutrality". According to industry test data, every 1 ton of biodiesel used throughout the cycle can achieve 2.0 tons to 2.5 tons of carbon emission reductions. As certified by the Dutch Double Counting of the European Union that is the largest consumer of biomass energy in the world, compared with biodiesel produced from vegetable oils such as palm oil, soybean oil, and rapeseed oil as raw materials, biodiesel produced from waste FOG such as swill-cooked dirty oil, hogwash oil, and acidified oil as raw materials has higher carbon emission reduction properties and should be vigorously promoted and used. The waste FOG is a kind of by-product of the edible oil processing industry with wide and stable sources. Compared with animal fats and vegetable oils and microbial oils, the waste FOG is relatively cheap, and thus it has obvious cost advantages as raw materials for preparing second-generation biodiesel through hydrodeoxygenation. However, the waste FOG has high fatty acid content and high acid value, and a hydrodeoxygenation reaction is carried out under high-temperature conditions and generates a large amount of water, which seriously affects the stability of the hydrogenation catalyst and causes the catalyst bed layer to be easily pulverized and deactivated. In addition, the waste FOG also contains a large number of impurities such as metals, phospholipids, and unsaponifiable substances. The deposition of such impurities on a surface of the hydrogenation catalyst also affects the stability of the hydrogenation catalyst. Therefore, when the waste FOG is used as raw materials to prepare second-generation biodiesel, the device needs to be frequently shut down to replace the catalyst, thus preventing stable run for a long period and resulting in high operating cost. In the existing technology for preparing the second-generation biodiesel by using the hydrodeoxygenation method, the waste FOG is generally pretreated by using conventional physical methods such as water method, acid washing, alkali washing, and adsorption, which can remove some impurities, but has a relatively low overall efficiency, and the conventional physical pretreatment methods cannot fundamentally address the problem of high acid value of the waste FOG. Other methods for preparing biodiesel from waste oils are described in WO2014/123711 or US2005/204612. SUMMARY In view of the deficiencies of the prior art, the present disclosure provides a chemical pretreatment process for waste FOG, which makes it possible to greatly reduce an acid value of the waste FOG, transform the waste FOG into a liquid with good fluidity, and significantly remove impurities such as metals, phospholipids, and unsaponifiable substances in the waste FOG. The waste FOG subjected to the chemical pretreatment process has a low loss rate (the yield is 98% or more). When such waste FOG is applied into a hydrodeoxygenation reaction section, it can greatly prolong the service life of the subsequent hydrogenation catalyst, significantly extend the operating time of the hydrodeoxygenation reaction section, immensely reduce catalyst consumption and operating costs, and improve device operation efficiency and production efficiency. The invention is defined by the claims. The present disclosure provides the following technical solutions. The chemical pretreatment process for waste FOG includes three working sections: first, subjecting the waste FOG to esterification reaction to prepare a fatty acid methyl ester; second, subjecting a crude product obtained from the esterification reaction and a catalyst to liquid-liquid phase separation through a chromatograph device to obtain a crude product solution in a form of oil phase and a catalyst solution in a form of aqueous phase, respectively separating the aqueous phase and the oil phase through evaporation systems to obtain a crude product, catalyst and methanol and water, storing temporarily the crude product in a storage tank, and recycling the catalyst back to the reactor; and finally, refining the methanol aqueous solution through a distillation tower to obtain high-purity methanol, which is returned to the reactor for recycling, and introducing a resulting wastewater to a storage tank. Specifically, the chemical pretreatment process for waste FOG includes steps of: S1, mixing a fresh methanol from a main pipeline from a boundary and a recycled ionic liquid from a catalyst recovery evaporation system to obtain a mixture, and then introducing the mixture into a catalyst preparation tank V101; adding a fresh ionic liquid catalyst to the catal