Method for purifying biodiesel by-product crude glycerine

Abstract

The invention discloses a method for purifying biodiesel by-product crude glycerine. The method comprises the following steps: preparing a ferric sulfate-tannin extract acidic mixed solution with the mass ratio concentration of 10%, and adjusting the pH value to be less than 2; putting the crude glycerin into a first-stage stirring kettle, conducting stirring, adding water, conducting heating to 80 DEG C, adjusting the pH value to 3.5-3.6, adding the prepared acidic mixed solution according to the proportion of 0.1%, uniformly conducting stirring, adjusting the pH value to 3.4, and controlling the temperature to be 80 DEG C; pumping the uniformly stirred crude glycerin into a primary heat-preservation precipitation tank for heat-preservation precipitation for 4 hours, discharging supernatant liquid into an alkalization stirring tank, adding liquid alkali for neutralization, pumping the crude glycerin into a temporary storage tank for storage until the pH value is 11.5, and precipitating oil residues to the bottom of the tank; discharging the oil residue to a secondary stirring kettle, adding acid and water, conducting stirring until the pH value is 3.0-3.4, adjusting the pH value to be less than 2, uniformly conducting stirring at 80 DEG C, feeding the stirred material into a secondary heat-preservation settling tank, quickly separating grease and impurities, and pumping middle-layer clear liquid containing a large amount of ferric sulfate and tannin extract into the primary stirring kettle for recycling; and enabling precipitated impurities to pass through an anti-corrosion centrifugal machine, sending centrifugate to a second-stage stirring kettle for recycling, discharging centrifugal residues out of a receiving tank, and discharging upper-layer floating oil after falling to the bottom.

Description

technical field

[0001] The invention relates to the technical field of glycerol production of organic chemical products, in particular to a method for purifying crude glycerin, a by-product of biodiesel. Background technique

[0002] The main raw material for the production of biodiesel is discarded animal and vegetable oils, and the glycerin content of the by-product crude glycerin is about 65%. The crude glycerin generally has problems such as poor quality, low purity, and many impurities. The impurities contained in crude glycerol include organic salts, inorganic salts, soaps, pigments, glycerides, catalysts and some other organic polymers in animal and plant tissues, etc. These impurities affect the pretreatment separation and purification of crude glycerin. At present, crude glycerin, a by-product of biodiesel, is generally treated by adding acid to remove oil and impurities, and some use membrane treatment to separate and purify crude glycerol. The main disadvantages o...

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