SU1477801A1 - Method of recovering chemicals from lye of hot refining of sulfite pulp - Google Patents

Abstract

The invention relates to the technology of regeneration of chemicals from liquors from the hot refining of sulphite pulp and improves the efficiency of the process by increasing the degree of sodium regeneration and reducing the content of dry and extractive substances in the products of regeneration while reducing energy costs. The liquor from hot refining is fed to an electrodialysis apparatus, the cathode of which is made of titanium, and the anode is made of ruthenium oxide. Between the two ion-selective chambers of the dialysis chamber an anion exchanger is placed - a product of treatment with a 25% aqueous solution of ammonia crushed to 3-5 mm of spruce bark. The exchange capacity of the anion exchanger used is from 3 to 7 mEq / g. Electrodialysis is carried out for 0.5-1.0 h at a current density of 10-60 mA / cm ² . 1 tab.

Description

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The invention relates to methods for the regeneration of chemicals from the liquor from the hot refining of sulphite pulp and is intended for use in pulp and paper production in the production of refined sulphite pulp for chemical processing.

The aim of the invention is to increase the efficiency of the process by increasing the degree of sodium regeneration and reducing the content of dry and extractive substances in the regeneration products while reducing energy costs.

According to the proposed method, the electrodialysis of the liquor is carried out in the presence of an anion exchanger with an exchange capacity of 3-7 mg eq / g, and the product of the treatment of crushed spruce bark with an aqueous solution of ammonia is used as the anion exchanger. The anion exchanger used is obtained by treating spruce bark crushed to a size of 3-5 mm at 120-160 ° C for 1-5 hours. In this case, a concentrated 25% aqueous ammonia solution is used.

This treatment provides anion exchange resin with a full exchange capacity of 3-7 mg-eq / g. Getting an

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Onita with exchange capacity above 7 mg. eq / g is difficult because it is associated with the use of high pressures and temperatures, long treatment. Obtaining a product with an exchange capacity of below 3 mg-ecl / g does not provide sufficient sorption capacity. The natural fir bark has weak anion-exchange properties. Treatment with an aqueous solution of ammonia under the specified conditions increases the exchange capacity of the bark due to the formation of additional NH groups. When liquor passes through such a weakly basic anion exchanger, sorption of organic substances dissolved in a retarok, having carboxyl, hydroxyl groups, groups of esters, occurs, which is typical of aromatic compounds of lignin, dissolved hemicellulose, resin and fatty acids. Removing such products reduces the amount of precipitate that falls out with a decrease in pH, reduces clogging of equipment, increases the degree of sodium regeneration, and reduces power consumption. Spent bark is burned or used as a fertilizer, as a product with a high nitrogen content.

The method is carried out as follows.

Lye from hot refining is fed to a 200 ml laboratory electrodialyzer. The cathode material is titanium, the anode is ruthenium oxide. The effective membrane surface is 32.8 cm2. The electrodialysis process is carried out in the presence of an anion exchanger. The anion exchanger is placed in the dialysis chamber of a 3-chamber electrodialysis between two ion-selective membranes MK-40 and MA-40. The amount of anion exchange resin is determined by its exchange capacity. With an exchange capacity of 3-7 mg.eq./g, the amount of anion exchanger is 7-5 g of absolutely dry matter, respectively. The current density is 10-60 mA / cm2, the duration of the process is 0.5-1 h.

Example 1. Lye from hot refining with a dry matter content of 18.2 g / l, extractive substances 2.2 g / l, and permanganate oxide capacity 14500 mg 02 / l is subjected to an electrodialysis process in the presence of anion exchange resin

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electrodialysis chamber between two ion-selective membranes MK-40 and MA-40. The anion exchanger is obtained by treating with a 25% aqueous solution of ammonia crushed spruce to a size of 3–5 mm, the exchange capacity of the obtained anion exchanger is 7 mg.eq./g. Electrodialysis is carried out for 1 h at a current density of 10 mA / cm2.

PRI me R 2 (by a known method). Electrodialysis is carried out without an anion exchanger at a current density of 10 mA / cm2 for 1 hour.

Example Electrodialysis is carried out using anion exchanger with an exchange capacity of 7 mg eq / g for 0.5 h at a current density of 60 mA / cm2.

Example 4: Electrodialysis is carried out with an anion exchanger having an exchange capacity of 3 mg.eq./g at a current density of 60 mA / cm2 for 0.5 h.

PRI me R 5 (by a known method). Electrodialysis is carried out at a current density of 60 mA / cm2 for 0.5 h without anion exchange resin.

II p and mep 6. Electrodialysis is carried out in the presence of an anion exchanger with an exchange capacity of 7 mg eq / g at a current density of 30 mA / cm2 for 0.5 h.

Example. Electrodialysis is carried out with an anion exchange resin having an exchange capacity of 3 mg. eq / g, at a current density of 30 mA / cm2 for 0.5 h.

Primerb (by a known method). Electrodialysis is carried out without anion exchange resin at a current density of 30 mA / cm2 for .0.5 hours.

The results are shown in the table.

As follows from the above data, electrodialysis in the presence of an anion exchanger provides for obtaining cleaner regenerated products, which is characterized by a decrease in the content of dry and extractive substances, an increase in the degree of sodium regeneration is also observed. Electrodialysis with the use of anion exchanger provides for obtaining regeneration products with a low content of dry and extractive substances, increases the degree of sodium regeneration due to the removal of liquids from the liquor while reducing the pH of the solution during electrodialysis, forming deposits on the membranes of equipment and making it difficult to conduct electrodialysis, and also provides

reduction of energy costs for the regeneration of chemicals by reducing the amount of precipitation.

Claims (1)

Invention Formula The method of regeneration of chemicals from liquor from hot refining of sulphite pulp by electrodialysis of liquor at a current density of 10-60 mA / cm2 for 0.5-1.0 hours, characterized in that, for the purpose of increasing 7780I6 Efficiency of the process by increasing the degree of sodium regeneration and reducing the content of dry and extra-active substances in the regeneration products while reducing energy costs, the electrodialysis of the liquor is carried out in the presence of an anion exchanger with an exchange capacity of 3-10 7 mg.eq./g as the latter, use the product of processing crushed fir bark with an aqueous solution of ammonia.