Method for preparing biological diesel oil from waste animals and plants grease

Abstract

The improved continuous esterification process of waste animal and vegetable oil and grease with low carbon alcohol to prepare biodiesel oil features that liquid low carbon alcohol is introduced into the liquid comprising liquid waste animal and vegetable oil and grease in 95-99.9 wt% and acid catalyst in 0.1-5 wt% to produce esterification reaction at normal pressure and the temperature from vaporizing temperature to 95 deg.c while the vapor mixture comprising the resultant, water vapor and low carbon alcohol vapor is discharged from the top of the reactor and separated in a fractionating tower to obtain product, separated water and liquid low carbon alcohol for reuse. The process has high reaction speed, high reaction conversion rate and other advantages, and the product has acid value capable of being controlled below 2 mgKOH / g.

Description

technical field [0001] The invention relates to a method for preparing biodiesel, in particular to a method for preparing biodiesel by continuous esterification of low-carbon alcohols using waste animal and vegetable oils as raw materials. Background technique [0002] Biodiesel is a fatty acid ester (mixed fatty acid low-carbon alcohol ester) obtained by transesterifying animal and vegetable oils and low-carbon alcohols (such as methanol, ethanol, butanol, etc.) under the action of an alkali catalyst. It has the advantages of regeneration, easy biodegradation, non-toxicity, low sulfur content and small emission of harmful substances in the exhaust gas, and is an environmentally friendly fuel. [0003] Using waste animal and vegetable oils (acidified oil, gutter oil, hog oil, clay oil, etc.) as raw materials to prepare biodiesel can reduce costs and find a good disposal method for these waste oils. However, since the main components of waste oil include oil and fatty acid, ...

AI Technical Summary

Problems solved by technology

The disadvantage of this one-time addition of reflux reaction is that the generated moisture (reaction water, self-contained water) is always in the reactor, and the reaction between low-carbon alcohol and fatty acid in the raw material is a reversible process, and the presence of moisture in the reaction system will make the fatty acid The esterification reaction with low-carbon alcohols is difficult to completely react, which in turn affects the rate of the esterification reaction and the equilibrium conversion rate. Esterification produces a high acid value, which affects the subsequent second step of the base-catalyzed reaction. For example, soap is easily produced during the base-catalyzed transesterification reaction. class by-products

Although this method can take out the moisture produced by the reaction through methanol vapor and be separated, the disadvantage is that the esterification reaction is operated under pressure, and the methanol vapor phase in the reactor is easy to leak, which increases unsafe factors; secondly, methanol is released from the reactor. The upper part is added, because the temperature in the reactor is higher than the vaporization temperature of methanol, most of the methanol has actually been vaporized after entering the reactor, so that only part of the methanol vapor is sucked into the reaction system in the form of bubbles by stirring to form a gas-liquid reaction with the oil (liquid phase). Two-phase reaction, due to the mass transfer resistance between the gas and liquid phases, the reaction mainly occurs at the gas-liquid phase interface, resulting in a decrease in the effect of the esterification reaction; moreover, the vaporization of methanol entering the reactor also suppresses the water contained in the reactor. Methanol vapor is discharged quickly, resulting in poor water take-out effect, which also reduces the rate of esterification reaction to a certain extent, and affects the subsequent second step of base-catalyzed reaction

But shortcoming is the same as above-mentioned CN1995288, and methyl alcohol also enters in the reaction system with gaseous form, and the methanol of vapor phase and liquid phase grease form gas-liquid two-phase, because catalyst is solid acid catalyst, actual reaction system is gas-liquid-solid three-phase reaction, Due to the mass transfer resistance between the gas-liquid-solid three-phase, it will also reduce the rate of the esterification reaction, resulting in a decrease in the effect of the esterification reaction; secondly, the reaction temperature is relatively high, the energy consumption is relatively large, and a methanol vaporizer and corresponding controls need to be added The system and equipment are inconvenient to operate, resulting in difficulty in process control

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