US1609832A - Process of pretreating wood chips in the production of soda cellulose - Google Patents

Description

Patented Dec. '1, 1926,

UNITED STATES PATENT 'OFFICE.

ERIK LUDVIG BI'NKAN. OF 153' UBS HOLH, SWEDEN.

PROCESS OF PBETBEATDS'G WOOD CHIPS IN THE PRODUCTION OFrSODA CELLULOSE- No Drawing. Application filed April 21, 1.20, Serial Roi 375,547, and in Sweden Augult 18, 1918.

. of the raw material .with steam, but it has not been possible to point out any particular advantages which will. compensate for the equally high concentration as according loss of time caused by the pre-treatment, except in the production of sulphite cellulose.

The conditions of the manufacture of celluv lose, particularly in the sulphate process, are therefore at the present time such that 1t 1s considered to be better the drier the wood 18,

' and that a better economy of heat is attained by the waste liquors being obtained in a more concentrated form. a

The present invention relates to a process of pre-treating the Wood chips or wood-like raw material,'such as bamboo in the production of soda cellulose which process has proved in practice to give aiiincreased yield of cellulose, and which re-treatment may simultaneously be carrie out in. such manner that the waste liquors obtained have an to the processes of producing cellulose hitherto practised. The process consists broadly in this that before the treatment with the chips are treated witha hot-diluted waste liquor from a previous boiling at a. temperature lower than 100 (3., so that the percentage of water of the chips is increased, for instance up to 40 to per cent. When the portion of the pre-treatment liquid which has not been absorbed by the chips, has been wholly or partly removed, the ordinary boiling liquid is admitted, when it is .to be observed that said liquid possesses such high concentration that the desired concentration of the boiling liquid is obtained when the liquids have become mixed with one another. As a result of this pre-treatment the chips become impregnated with a hot neutral liquid, owing whereto the action of the boiling liquidis accelerated but is simultaneously modified to a very high extent so that an essentially increased yield of cellulose is obtained. The yield of cellulose may be increasedby 10 to 25 per cent as compared with that obtained without the use of this pre-treatment. By this re-treatment more water is supplied to the c ips than according to the practice here- I it is desired shall be absorbe tofore followed, but the dilution of the boiling lye caused hereby may be compensated by using such great quantity of waste liquor, when preparing the boiling lye, that the percentage oforganic substances of the lye still mayrequire up to one hour m order'that V the desired result shall be attained. The desired effect of 'the pre-treatment. onl being obtamed if the liquid used is hot, t pretreatment may be applied with advantage also to so moist chips that they possess beforehand the percentage of water of approxto as the percentage of water of the chips will not be imately 50 per cent above referred materially increased by treating moist chips with hot liquids.

The chips may be pre-treated in this manner either before they are admitted into the boiler, or in the boiler. In the'latter case a saving of heat is gained, and the advanta e l is also attained that the quantity of-liquld absorbed by the 'chips'is easily measured measuring the difference between the' am- 'tity of-liquid supplied to the boiler an the quantity afterwards removed therefrom. It

is most advantageous to carry out the pretreatment in the boiler, as otherwise there will easily'be a loss of lye,

The practical application of the process 1s suite in aispecial receptac e fromw 'ch it may be rapidly tapped or pum ed into the holler. A greater uantity' of t e liquid than that 7 1y carried out in such manner that the pre-treatment li uor is ke tin hot state whlch may e absorbed by the chips ma bel let into the boiler, or only the (quantity w 'ch t The admiss1on of the liquid into the boiler may suitably *begin when the boiler has been RPPIOXIr' mately half filled with chips and may be performed so rapidly that all of the treatin liquid is supplied when the boiler is filled 'wlth chips. Afterwards. the liquid is re= tained in the boiler during the refiuired riod of time during which it sho d pref ably be kept in mot on so that the chips will become intimately mixed with the liquid. This may be effected either by rotating the boiler or by causin the liquid to circulate. Meanwhile, the liquid may also be heated directly or indirectly, if considered suitable. The treatment having been finished, theliquid which has not become absorbed by the chips, or which it is desired to remove from the boiler, is again drained oil or pumped off into the same receptacle and may again be used after compensating for the material retained in the boiler. As regards the suitable quantity of treating liquid it may be stated as an example that in a rotary boiler having a capacity of 30 cu. m., 10 to 15 cu. m. treating liquid is used.

For heating the p're-treatment liquid the steam generated when the contents of the boiler are blown over to the'difl'users, may suitably be used. The lye and fibres which are then possibly carried alon will stop in the pre-treatment liquid, so that no special arrangement for collecting the same is necessary, but the receptacle for the pre-treatment liquid may form the required collecting devlce.

The process of pre-treatment above described, when carried out in the proper manner, is exceedingly simple and does not materially increase the time of boiling, particularly when it is considered that the yield of cellulose becomes considerably increased. In addition, the cellulose obtained is of a higher quality than that which it is possible to obtain if the wood chips are boiled directly without pre-treatment. As regards the result attained the present process has therefore a quite different effect from that of the old treatment of the wood chips with steam.

I claim; 1. The process of pre-treating wood chips in the production of soda cellulose, which consists in impregnating thewood chi s before the treatment with the boiling iquidproper with hot diluted waste liquors at a temperature lower than 100 C. for the purpose of attaining a rapid but modified action of the boiling liquid when afterwards supplied to the material. 1

2. The process of pre-treating wood chips in the production of soda cellulose, which consists in impregnating the wood chips before the treatment with the boiling liquid proper with hot diluted waste liquors at a temperature between 80 C. and'90'C. for the purpose of attaining a.rapid but modified action of the boiling liquid when afterwards supplied to the material.

3. The process of producing soda cellulose,

which consists in impregnating wood chips with hot diluted waste liquors at a temperature lower than 100 C., and afterwards treating such impregnated wood chips with a caustic soda lye.

4. The process of producing soda cellulose, which consists in impregnating wood chips with hot diluted waste li uors at a temperature between80 C. an 90 0., and afterwards treating such impregnated wood chips with a caustic soda lye.

ERIK LUDVIG RINMAN.