DE689045C - eye in highly viscous or solid form - Google Patents

Description

The invention relates to a method for

Conversion of sulphite pulp waste liquor in highly viscous or solid form in order to convert it into a for further processing, e.g. B. to solid fuel, appropriate form to transfer.

In order to be able to utilize sulphite waste liquor, it is known that it has to be evaporated to a greater or lesser extent will. It has been shown that evaporation to higher concentrations (over 55% dry matter) causes difficulties because the concentrated caustic tends to a marked extent during the evaporation and also later during the Coking sticking and blowing bubbles.

The conversion of part of the dry material content of the sulphite waste liquor into solid form (production of so-called sulphite coal according to the Strehlenert process) is already known. In this process one works in such a way that the sulphite waste liquor is ^{heated to about 200 0} under pressure and simultaneous oxidation, with complete destruction of the lignosulphonic acid. In this process, only part of the dry matter content of the liquor is converted into solid form. So let it go. B. from a Latuge with ii, 6 ° / o Trockengutgehalt in the above Behandlung'in 35 minutes forming a precipitate, the waste liquor is 60.9 g per liter, ie just slightly be of the entire T-rockengutgehaltes more than 5o ° / ₀ converted into solid form (E. Hägglund, "Holzchemie", 1928, p. 116 below, p. 117 above).

It has also been proposed to produce a fuel in powder form from the waste liquor, namely by first evaporating them in conventional evaporators up to 50 to 60% dry content, after which the lye thus obtained is atomized and brought into contact with hot combustion gases so that most of the remaining water is removed and

the remainder is a powder that can be used as fuel.

According to other methods of utilizing the black liquor that occurs during the production of sodium cellulose, it is ^{evaporated after pressure heating at about 350 °} and 150 atm.

The Strehlenert process involves a decomposing treatment the sulphite waste liquor part of the dry matter content at higher pressure and higher temperature to separate the lye in solid form. According to the older patents will be ordinary unevaporated or slightly evaporated Treated waste liquor. It is stated in a patent that the lye is a Concentration is suspended by evaporation before decomposition, without further specification how far the evaporation takes place.

In contrast to this, in the method according to the invention, the whole of the liquor, which has been strongly evaporated beforehand, takes on a highly viscous or solid form, in that the liquor is heated under pressure to over 100 ° in an autoclave for a certain period of time. This cannot be achieved at the low caustic concentrations that are used in the known processes. One must liquor used which contains at least 4O ° / _0, preferably 50 to 6o ° / o dry material, if one wants to achieve that the whole liquor mass and not only a larger or smaller part of the dry material assumes a highly viscous or solid form.

The heat treatment under pressure causes an increase in vicosity without any detectable Amounts of water are lost. If the heating is carried out long enough, the lye can turn into a paste-like solution or even pass over solid form.

The method can be used for any waste liquor Origin, as in the usual calcium bisulfite process as well as in the ammonium bisulfite process (Croß - Engelstad and similar processes) can be used.

If you heat z. B. 55% i§fe ammonium bisulfite waste liquor in a pressurized bottle to about 1 io ° for 2 days, then it turns into a solid, elastic and black colored mass that does not contain water when treated has lost. The mass dries quickly and easily in the air to form a substance with a glass-like appearance Breakage that does not stick or that bubbles when heated and coked.

Tests have also shown that, ever

the higher the temperature used, the shorter the conversion time. In order to ensure that the lye goes into solid form, the concentration should be about 45% or preferably even higher. At a lower concentration, no solid is obtained without using very high temperatures at the same time, but the viscosity increases sharply. At concentrations of 50 to 55% dry material, the liquor can be converted into solid form by heating to various temperatures of over 10 °, z. B. about 110 ° and higher, up to 180 °. The same effect is achieved with heating to 155 ^° in 1 hour as with heating at no ⁰ in about 2 days. More or less dehydrated material from previous batches can also be added to the lye before treatment. This enables the duration of treatment to be shortened. A lye with 50% dry matter content, for example, became solid after heating to 10 ° in a little more than 2 days. With the addition of 25 parts of recycled material to 100 parts of alkali, the same alkali solidified in the course of about 20 hours in the same treatment.

If a sulphite liquor treated according to the present process is subjected to the Coking shows that coking, taken in practice, does not increase in volume takes place while the coking of an untreated waste liquor due to the strong Throwing bubbles and the resulting increase in volume is difficult to make.

In the treatment of pulp waste liquor from the ammonium bisulfite process (Croß-Engelstad process and related processes) it has proven to be expedient to use the more or less solid and preferably subjecting the dried product from the waste liquor to a coking process, by placing it in a retort with or without a supply of nitrogen, air or water vapor is heated.

In this way a solid fuel is obtained with less sulfur than in the starting material, at the same time, practically speaking, all the ammonia in the waste liquor and a large part of the sulphurous Acid regenerated and reused in the production of cooking liquor no can.

Implementation example

Pulp waste liquor from the cross-Engelstad method with 50 ° / o Trockengutgehalt was long first 1 hour at 155 ^{r 0} in an autoclave in the above-described w ay treated being passed into solid form. The solid mass was then air-dried overnight and comminuted to a suitable grain size. According to analysis, the mass contained 82 ⁰ Jq dry

good and 5.5 per cent sulfur, i.e. 6.7 per cent sulfur in the dry material.

Samples of the crushed mass were heated in a retort for 15 to 30 minutes or a little longer to various temperatures between 200 and 470 ⁰ , while a little nitrogen was passed through the mass from the bottom up to facilitate the abortion of the gases. in each experiment was instead nitrogen air, saturated with water vapor at 75 ⁰ -Uses. The exhaust gases were taken up in water which was analyzed. The coke left in the retort was also analyzed.

The experiments showed that at 600 could be regenerated in this manner at a half-hour heating in a Stickstoffatmösphäre at temperatures from 270 to 370 ⁰ about 50O / 0 of sulfurous acid and 95 to 99 ° / o of the ammonia, to 8oo ° even 70 to 83 ° / o of sulphurous acid and 9 to 99.7 ° / o of ammonia. If the experiments were carried out with the introduction of some air instead of nitrogen, with part of the mass being burned and generating heat for the degassing, it was found that after half an hour of heating to 270 to 370 ⁰ 70 to 75% of the sulphurous acid and 99 to 99.5% of the ammonia was regenerated.

Also evaporated when heated

constituents other than sulphurous acid and ammonia, so that the weight loss of the solid mass is greater than the sum of the weight of the sulphurous acid and ammonia driven off. The weight loss, which is greatest due to the combustion when air is introduced, increases relatively strongly with the temperature. In nitrogen atmosphere, the loss was thus at half-hour heating at 200 ° 19 ° / o ^un d increased with temperature up to about "40 ° / o at 370 ⁰ and up to more than 50 ° / ₀ 600 to 8oo °. When supplying air the weight loss increased from about 20 ° / o at 200 ° to about 70 ° / o at 370 ^0th

As a result of this weight loss, the coke remaining in the retort usually contained coke about 4 per cent. sulfur.

As can be seen from the above example, one can, according to the method, practical taken all the ammonia in the brown liquor and most of the sulphurous Regenerate acid.

It is expedient to work in such a way that the ammonium sulfite solution resulting from the expelled Ammonia and sulphurous acid forms, as an absorption liquid for sulphurous acid z. B. in a Säuireturm is used. If this has the desired sulfuric acid content (and Ammonia), it is ready to use as new cooking liquor.

Claims (2)

Claims: g 1. A process for converting sulfite cellulose waste liquor into highly viscous or solid form by evaporation and subsequent heating under high pressure to temperatures above ioo °, characterized in that the waste liquor is ^{evaporated to at least 40 0} J ₀ , preferably 50 to 60 ° / ₀ dry content and then heated to temperatures between 105 ° and 180 ° under pressure. 2. The method according to claim 1, characterized in that the waste liquor that the Pressure heating is to be exposed to more or less dehydrated material previous operations.