CZ47996A3 - Process of treating glycerol solutions by making use of membrane filtration - Google Patents

Abstract

Method of refining glycerine solutions from triacylglycerol splitting by a combination of filtration with at least one membrane capable of containing substances with molecular mass greater than 10,000 D, for example micro-filtration and ultra-filtration to a nano-filtration membrane, capable of containing substances with molecular mass greater than 0.001 microns, or substances with molecular mass greater than 200 D and/or a combination of ultra-filtration, nano-filtration and reverse osmosis. Filtration is performed at a pressure of 0.2-10.0 MPa. Prior to membrane filtration it is recommended to modify the pH of the initial product to a value of 7-12.

Description

State of the art

The starting materials used in the production of glycerol are variously diluted glycerol solutions resulting from the production of fatty acids by the breakdown of fats and oils, the so-called glycerin water, soap production - the so-called bottom lye, glycerol solutions resulting from the transesterification in the manufacture of epichlorohydrin, synthetic glycerin and others.

In addition to glycerol, these industrial solutions contain a variety of ballasts such as free fatty acids, soaps, esters, proteins, dyes, mucilages and other substances that need to be largely removed. This is done by various refining processes. The most widely used industrial method of ballast removal is physicochemical refining of glycerin solutions, which consists in decomposing the contained soaps with mineral acid, separating the released fatty acids by decanting or centrifuging, clarifying the solutions by adding flocculants such as aluminum or iron sulphate and basifying the solutions after filtration.

Other refining processes such as the use of various sorbents, such as activated carbon, aluminosilicates, etc., refining glycerin solutions using ion-exchangers and electrodialysis, or removing fatty acids by ultrafiltration are also described.

Concentration of refined glycerin solutions is generally carried out by evaporating the water under vacuum in various types of evaporators. The use of reverse osmosis for this purpose is also described.

Physico-chemical refining and other processes described have a number of drawbacks, such as a low degree of removal of ballasts or the removal of only some impurities, dilution of solutions with water during the refining process, introduction of other generally inorganic impurities with chemicals used in chemical refining. , production losses and relatively high energy and investment intensity. The use of ultrafiltration alone does not lead to the necessary refining effect, since only a small portion of the ballasts, mainly macroscopic impurities, is removed and further refining of the glycerin solution must follow. The use of reverse osmosis to thicken glycerine solutions is problematic due to the insufficient degree of ballast removal and the high dissolved salt content and is not widespread in industry.

SUMMARY OF THE INVENTION

These drawbacks are overcome by the method of the present invention, wherein the contained ballast materials are separated by passing glycerin solutions through a system of at least two different membrane filters at a pressure of 0.2 to 10.0 MPa, of which at least one filter is fitted with a nanofiltration membrane with particle retention capacity greater than 0.001 pm.

The process can be carried out in both batch and continuous fashion. The practical implementation of this process for the treatment of glycerin solutions may be variable, depending on the nature of the feedstock and the requirement for the final product. Therefore, filters with microfiltration membranes or reverse osmosis filters are included next to the nanofiltration membrane filter.

The filter system with microfiltration or ultrafiltration and nanofiltration membranes removes ballasts substantially more effectively and is therefore a more efficient refining process than the physico-chemical refining used and can be included as an additional step to this refining process. The use of said membrane filter system for the refining of glycerin solutions makes it possible subsequently to use reverse osmosis to partially thicken them. The advantage of this method of treating glycerin solutions is the removal of more ballasts, i.e., higher refining efficiency, without the addition of other inorganic salts to the solutions, less dilution, and purer solutions. As a result, the energy consumption of glycerine production is reduced, production losses are reduced, and product quality is increased.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

After physicochemical refining, the glycerine solution left in the soap production was processed into a system of two 0.14 m ² membrane filters, the first of which was fitted with 0.45 µm GRM microfiltration membranes and the second with NF 45 nanofiltration membranes. The feed solution was first processed on a microfiltration membrane at a pressure of 0.4 MPa and a temperature of 40 ° C. The microfiltrate was then processed by passing through a nanofiltration membrane at 40 psi and 40 ° C. The concentrates retained on the filters were dialysed with water. In total, 4 kg of bottom lye were processed with a content of 8.5% by weight. % glycerol, 7.0 wt. ash,

2.6 wt. non-volatile organic residue (NOZ) and paint 12 according to ČSN. A solution containing 7.8 wt. glycerol, 6.5 wt. % ash, 1.2 wt. NOZ and colors 2 according to ČSN. Performance in microfiltration was 25 l.rrf ² .h ^_1 and nanofiltration at the performance of 42 lm ² .h ^_1. The yield of glycerol was 93%.

Example 2

9 kg of unrefined glycerin waters from the non-catalytic cleavage of the rendered fats containing 12.3% by weight were processed on the apparatus and procedure described in Example 1. glycerol, 0.1% ash, 0.4% wt. NOZ and colors 11 according to ČSN, where the pH value was adjusted to 8 by addition of sodium hydroxide. The first filter was fitted with plate membranes for ultrafiltration GR 51 PP (manufacturer DOW) and the second membrane for nanofiltration NF 45 (manufacturer DOW). Ultrafiltration was performed at 60 ° C and 0.8 MPa, nanofiltration at 40 ° C and 4.0 MPa. A solution having a content of 11.6% by weight was obtained. glycerol, 0.1 wt. ash, 0.1% NOZ and colors 2 according to ČSN. The yield of glycerol was 96% by weight.

Example 3

On a membrane filter system consisting of an ultrafiltration device with a plate module with a membrane area of 2.25 m ² and fitted with a GR51PP type polysulfone membrane (manufactured by DOW), a nanofiltration device fitted with a spiral wound element with an NF 45 membrane of 5 m ² (DOW manufacturer) and from a reverse osmosis device fitted with a spiral wound element with a FT 30 membrane of 5 m ² (DOW manufacturer), glycerine water from non-catalytic cleavage of animal fats in a quantity of 500 kg containing 8.6% by weight . % glycerol, 0.6 wt. % ash, 0.6 wt. NOZ and paint 12, at a temperature of 62 ° C and a pressure of 0.8 MPa on the first filter, at a temperature of 40 ° C and a pressure of 2.2 MPa on the second filter and a temperature of 38 ° C and a pressure of 5.0 MPa on the third filter. On the first filter, a filtration rate of 34 lm ² .h ^-1 was achieved, on a second filter 40 lm ² .h ^-1 and on a third filter a filtration rate of 8 lm ² .h ^-1 . A refined and partially concentrated glycerin solution was obtained with a content of 14.6% by weight. glycerol, 0.7 wt.% ash, 0.2 wt. NOZ and colors 3 according to ČSN. The yield of glycerol was 95% by weight.

Example 4

On the apparatus and procedure of Example 3, a glycerine solution, which was produced in the manufacture of rapeseed fatty acid methyl esters containing 10.0 wt. glycerol, 1.6 wt. NOZ and paints 11. A refined and partially thickened glycerin solution containing 15.2 wt. % glycerol, 0.4 wt. The yield of glycerol was 92% by weight.

Claims (4)

PATENT CLAIMS Process for treating glycerin solutions by membrane filtration, characterized in that ballasts contained in glycerin solutions are removed at a pressure of 0.2 to 10.0 MPa by nanofiltration, in which particles larger than 0.001 µm are retained on the filter membrane, in combination with at least one more membrane filtration. 2. A process for the treatment of glycerin solutions by membrane filtration according to claim 1, characterized in that the refining of the glycerin solutions is carried out by a combination of microfiltration and / or ultrafiltration and nanofiltration. 3. The method of treating glycerin solutions by membrane filtration according to claim 1, characterized in that the refining and partial concentration is carried out by a combination of ultrafiltration, nanofiltration and reverse osmosis. 4. A process according to claim 1, characterized in that the pH of the feed glycerin solution is adjusted to a value of 7 to 12 prior to the membrane filtration.