CS263542B1 - A method of integrating the milling process of a pulp - Google Patents

Abstract

The solution relates to the intensification of the pulp grinding process by using certain ammonium compounds applied to the fibrous pulp suspension before or during the grinding process. The application achieves a 10 to 50% reduction in grinding time or energy savings. Suitable ammonium compounds include ammonium hydroxide, ammonium nitrate, ammonium acetate, ammonium rhodanide or mixtures thereof.

Description

The invention discloses a method of intensifying the pulp milling process by chemical means, i.e. by using additives which allow the milling process to be accelerated, thus reducing the energy consumption of the milling process.

It is known that the grinding process is one of the most energy-intensive sections of paper production. There are efforts to reduce this energy intensity. Research can be divided into two directions. The first deals with the modification of the grinding equipment, so it is a mechanical matter. The second direction is one that seeks to recognize the internal structure of the pulp and release the internal bonds of the individual fibers and fibrils by the action of chemical compounds. In cooperation with the mechanical action of the grinding device, the grinding process can be significantly accelerated. There is a Japanese patent Kokai 71, 893/80 for a mixture of chemicals that accelerates grinding and improves paper strength. The composition comprises NaOH, NaHgPO4 or NagHPO4, sodium gluconate or citrate and a chelatone agent. The influence of dyes on the course of the milling process has been discussed by CENTOLA, G. and BORUSO, D. (Fundamentals of Papermaking Fibers. Kantley, TS Brit. Pap. Board Mak. Assoc. 1958, p.349). They found a positive effect of acid and direct dyes. LANÉ, JN, SLOAN, Y., ALLAN, GG (Up to 50 Refining Process by Additives - Particularly Congo Red. Ing. Symp. Fundamental Concepts in Refining ”, Sept. 16-18, 1980, Appleton) % acceleration of the grinding process by adding Congo red. Bulgarian authors are also concerned with the effect of additives on the grinding process. STOILKOV, O., NEDELCHEVA, E. (Tseluloza Khartiya 14, No. 6, 5-7, 1983) investigates the effect of polyelectrolytes on the milling process. They found positive effects of polyethyleneimine and polyacrylamide. PULTAVA GERASIM, N., DIMITROVA, S., NEDELCHEVA, N. (Tseluloza Khartiya 15, No.2, 22, 24, 36, 1984) found a positive effect of the P-103 antifoam (PEG ester type) on the grinding rate. Nedelcheva, E. DENCHEVA S. Valchev _t, V. ROZALINOV, D. (Cellulose Chem. Technol., 19, 409 ^ 414, 1985) disclose grinding acceleration due to the addition of the modified polvakrylonitrilu hydrolysis. NEDELCHEVA, £., IVANOVA, N.MLADENOVA, S. (Cellulose Chem. Technol. 20, 107-155, 19S6) further observed the effect of polyacrylamide, polyethyleneimine and polyamidamine. The grinding acceleration was about 30%.

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- 2 When using additives, it is necessary to consider their availability and assess the economic and ecological side. The disadvantages of these methods are the high prices of additives,

In the case of dyes, this is the coloring of the final product and waste water pollution.

These disadvantages can be overcome by the present invention, which describes the use of ammonium compounds, i.e., ammonium hydroxide, ammonium nitrate, ammonium rhodanide and ammonium acetate, or mixtures thereof, as accelerators of the milling process.

The ammonium hydroxide is dosed in the form of a solution into the pulp suspension so that the pH of the prepared stock is in the range of 7.5 to 10, but usually 8.5,

Ammonium nitrate is metered into the pulp at the beginning or during grinding in an amount of 0.1 to 5% by weight. to the weight of absolutely dry pulp, but normally 0,2% by weight,

Ammonium acetate is dosed at the beginning or during grinding into the pulp in an amount of 0.5 to 5% by weight, based on the weight of the absolutely dry pulp, usually 2% by weight,

Ammonium rhodanide is dosed at the beginning or during milling into the pulp in an amount of 0.5 to 5% by weight · on the weight of absolutely dry pulp, but usually 1% by weight

The advantage of this method of intensifying the grinding process is the availability of the materials used and their low cost.

The addition of ammonium hydroxide, ammonium nitrate, ammonium rhodanide and ammonium acetate acts throughout the fiber treatment range (SR). The action of these substances releases the internal structure of the pulp and hence accelerates the grinding process, which results in a proportional reduction in energy consumption.

Příkrlpd 1

A 20 L 2% bleached kraft pulp suspension was prepared. The suspension was transferred to a laboratory disk mill and a grinding experiment was performed. During grinding, the power input to the grinding apparatus was kept constant and the mechanical processing of the pulp was followed by the Schopper-Riegler (SR) method. The values are shown in the table.

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Example 2

A 20 L 2% bleached kraft pulp suspension was prepared with the addition of ammonium hydroxide at pH = S.

The milling experiment was carried out under the same conditions as in Example 1. The values obtained are shown in the table. The mechanical properties are comparable to Example 1.

Example 3

20 L of a 2% bleached kraft pulp suspension was prepared with the addition of 2 wt% ammonium acetate to the weight of the absolutely dry pulp. The grinding experiment was carried out under the same conditions as in Example 1. The values obtained are shown in the table. The mechanical properties are comparable to Example 1

Example 4

20 L of a 2% bleached kraft pulp suspension was prepared with the addition of 0.2 wt% ammonium nitrate to the weight of the absolutely dry pulp. The grinding experiment was carried out under the same conditions as in Example 1. The values obtained are shown in the table. The mechanical properties are comparable to Example 1.

Example 5

20 L of a 2% bleached kraft pulp suspension was prepared with the addition of 1 wt. of ammonium rhodanide to an absolute dry pulp weight, a milling experiment was performed under the same conditions as in Example 1. The values obtained are shown in the table. The mechanical properties are comparable to Example 1

Claims (1)

Process for intensifying the pulp milling process by chemical means, characterized in that ammonium compounds such as ammonium hydroxide are metered into the fibrous pulp suspension in such an amount that the pH of the prepared suspension is 7.5 to 10, but usually 8.5 % or ammonium nitrate in an amount of 0.1 to 5 wt. typically 0.2 wt. % by weight of absolutely dry pulp, or ammonium acetate in an amount of 0.5 to 5 wt.%, but usually 0.2 wt. % by weight of absolutely dry pulp, or ammonium rhodanide in an amount of 0.5 to 5 wt.%, but usually 1 wt. % by weight of absolutely dry pulp, or 0.5 to 5 wt. mixtures of these substances to the weight of absolutely dry pulp.