CS252382B1 - Method of pressure hydrolysis with sodium hydroxide - Google Patents

Abstract

A method of pressure alkaline hydrolysis of waste of fully or partially finished leathers by treating the waste with an aqueous solution containing by weight 0.6 to 9.5% sodium hydroxide, 0.25 to 12.5% sodium silicates and/or up to 8% urea with stirring at a temperature of 75 to 155 °C, a pressure of 0.1 to 0.6 MPa for 0.5 to 8 hours.

Description

2S2382

BACKGROUND OF THE INVENTION The present invention relates to a process for the pressure hydrolysis of sodium hydroxide with waste of complete or partially finished leather. In the manufacture of ashes, footwear, leather haberdashery, waste is generated in the shaping and splitting of the tannery material, and in the extraction of parts from finished finished leather. a considerable amount of lean material, which is found in stacks. Partially, the leather waste is processed in the following manner. fibrous materials or hydrolysing the feed with pressure alkaline hydrolysis with lime. This procedure makes it possible to separate a substantial part of the chromium present as insoluble hydroxide. However, the advantages of this process are in the incomplete hydrolysis, which is the consequence of the low activity of the hydrolytic agent, so that even half of the waste waste will not dissolve even at elevated temperature and pressure. Other disadvantages are the relatively low concentration of proteins in the hydrolyzate, since the process takes place for a relatively long time and is considerably diluted with condensate upon direct steam heating.

The aforementioned disadvantages are largely prevented by the method of pressure hydrolysis of the present invention, which consists in disposing of the waste with an aqueous solution containing from 0.6 to 9.5% by weight of sodium hydroxide, 0.25 to 12.5% of silicate. sodium and / or up to 8% urea are stirred at a temperature of 75 to 155 ° C, a pressure of 0.1 to 0.6 MPa for 0.5 to 8 hours.

According to the invention, the hydrolytic process is intensified using a more soluble alkaline reagent which is more potent and can be further elevated by temperature and the addition of a hydrotrope. Such an agent is sodium hydroxide, which is well soluble in water and, unlike the hydroxyalcium lime, its solubility and thus its ascending temperature activity does not decrease, on the contrary, it increases. Therefore, the rate of hydrolysis in the presence of this agent is considerably higher, and can be even more enhanced by the addition of viscosity-reducing substances to the hydrolysis. Such substances are urea or alkaline silicates, which have the ability to interrupt hydrogen interactions in proteins. The use of an alkaline alkali silicate which is stable in the alkaline environment is only possible in the absence of calcium ions, otherwise precipitating calcium silicate precipitates. Sodium hydroxide has been used in the past for pre-hydrolysis of trisiluted waste, experimentally carried out at the Svit Otrokovice site in connection with production of Svitan KO, which was not implemented. In this case, the non-pressurized hydrolysis used and the amount of sodium hydroxide used far exceeded the upper limit of the dosage and sub-invention. The method of the present invention allows for a smaller amount of hydroxide to be used for hydrolysis about four times while shortening the hydrolysis time from about 16 hours to 2-3 hours.

The use of the method according to the invention for non-shavings is also easy to carry out and the conditions used have been a test of operation. Advantages of the process according to the invention are the elevated yield of protein hydrolyzate, in a significant reduction of non-hydrolyzed sludge, which is an unpleasant waste, in shortening the hydrolysis time and hence in energy consumption and in achieving a significant higher concentration of protein hydrolyzate which is ingested advantageous for reducing the energy required to thicken and dry the product. Example 1

A mixture of handling leather waste with the production of footwear and chromium-plated carcasses in a ratio of 2: 1 in the amount of 1200 kg is placed in a pressurized rotary vessel, 35 kg of flaked technical sodium hydroxide, 15 kg of water glass solution (sodium silicate) and 250 kg of water are added. kg of water. The mixture is heated with a direct steam furnace at a pressure of 0.4 MPa while moving for 2 hours, then the steam supply is stopped and moved for 1 hour to partially cool the contents. After, venting and venting, the contents are discharged through a basket to hold the collected portions and pumped for further processing. Example 2

The handling waste mixture is placed in a pressure vessel of 1200 kg, 500 kg of water and 25 kg of sodium hydroxide, technical and 25 kg of urea are added. purity. 300 kg of water are added and heated with steam at 0.35 MPa for two hours. Thereafter, the mixture is moved for about one hour to partial cooling, adding no more water and venting. The obtained hydrolyzate is decanted through a solids collection basket and further processed according to the desired use. Example 3

A 2: 1 mixture of the waste from the production of the waste and chromium leather was hydrolyzed with 20 kg of sodium hydroxide, technical, 100 kg of water glass (15%) and 20 kg of technical grade urea. Add 100 kg of water and heat the steam at 0.35 MPa for 2 hours with constant movement. Thereafter, the contents of the flask are cooled with 200 l of water, de-aerated, and poured over a basket to hold the solids. The resulting hydrolyzate solution is used for further processing.

Claims (1)

SUBJECT A method of pressure hydrolysis with sodium hydroxide waste of complete or partial finished leather, characterized in that the waste is treated with an aqueous solution containing by weight 0,6 to 9,5% of hydroxide OF THE INVENTION Sodium 0.25 to 12.5% sodium silicate and / or up to 8% urea with stirring at 75 to 155 ° C, pressure of 0.1 to 0.6 MPa for 0.5 to 8 hours.