US1793264A - Method of cooking sulphite cellulose - Google Patents

Description

Patented Feb. 17,1931

y UNITED STATES PATENT OFFICE SERGEI-I. TSCHUWIKOWSKY AND GRIGORY I. LIACHOVETZKY, F MOSCOW, UNION 0F 1 SOCIALIST SOVIET REPUBLICS METHOD OF cooxmo sULPHIrE OELLULOSE .Applicationled November 8, 1929, Serial No. 405,670, and-in Union of Socialist Soviet Republics August A very loW percentage only of the sulphite cellulose factories uses the -heatof the liquor for preheating the Water or the cooking acid. A loW percentage of the factories obtains the thickening of the liquor during the process of obtaining alcohol, tanning extract, resin and so on. In the first mentioned process a portion of the heat of the liquor is utilized, but the valuable products present are not utilized. In the second mentioned process a by-product is obtained during the thickening of the liquor, but the heat of the Waste liquor leaving the cookers is not perfectly utilized during the process of evaporating. The thickening of the sulphite liquor is usually carried out under vacuum at loW temperatures which, as is well known, enhances the viscosity, impairs the circulation, causes the separation of the products adapted to form crusts and reduces the heat conductivity. These circumstances cause technical diiiiculties and augment the costs in such a manner that very often the thickening of the liquor is renounced. As the liquor coming from the cookers contains about 25% of the heat consumed' in cooking, the reduction of the heat used for cooking the cellulose is materially dependent on th-e method employed for utilizing the liquor running oil'. It therefore follows that from the standpoint of heat economy the methods of evaporating and of cookingthe cellulose are not to be separated, as this is usually the case up to now, but must be combined. If the cellulose is directly cooked by steam leaving a steam engine or delivered by a boiler, a device for pre-l paring the feed Water forthe boiler is now required'the capacity of which is a little greater than the steam consumption necessary ffr cooking the cellulose. On account of a great quantity of additional Water required, the main-and utilizing 'costs are increased, the properties of the feed water (particularly if chemically purified) are impaired, the operation of the steam boilers is influenced and additional losses of heat are Y caused in the feed Water of the boilers.

All these draw-backs and disadvantages are obviated by the use of the method according to the present invention for cooking cellulose.

The invention is concerned with a method for cooking cellulose according to which the cooking of the cellulose is carried out by the vapor produced during the evaporation of the sulphite liquor. The cooking and the thickening of the liquor produced during the cooking form a continuous process.

As both these processes are to be carried out simultaneously and must not be separated from each other, a common cycle of heat circulation is obtained under these conditions.

The evaporating device, thereby, utilizes the heat contained in the liquor delivered by the cookers, Whereas'the heat of the vapor produced by the thickening of the liquor is utilized by the cookers for cooking the oellulose.

The evaporating devices must connected to the cooking vessels. As according to the new process the thickening of the liquor is carried out under high temperatures,

cause vapors of high temperatures are required for the cooking of cellulose, the viscosity of the liquor is reduced, the circula tion is improved and far better utilizing conbe directly ditions areobtained compared with the pres-y ent conditions. The amount of the liquor available for exploitation andthe amount of vapor produced de end on the process of cooking and on the liind of cellulose treated. Theheat of thesecondary steam must, of course, be utilized perfectly to obtain an economic process. The calculation shows that, under the usual fluctuations of the liquor output, the main portion of the secondary steamv is used for the cooking of the cellulose and only a small portion of the steam may be distributed among the other cellulose producing consumers. In this manner, the number of the additional consumers, the amount ofthe available secondary steam and the general diagram of operation are determined in each casein connection with the liquor output, the amplitude and the kind ofthe plant. The same is true with regard to the condensate of 'the secondary steam and the heat of same. By the nevv method the volatile products contained in the secondary steam may be obtained by fractional distillation without consuming any additional heat. The losses of condensate are in this cooking process limited in the same manner as in an indirect cooking process, because the consumed steam coming from the boilers is returned to the boiler invention is shown diagrammatically by way of example.

From the cookers 1 (or fromV devices for chemical treatment) the sulphite liquor flows directly by way of the piping 2 into one of the closed and isolated vessels 3. This piping 2 as well as all other pipings mentioned below are, in a known manner, provided with valves or other suitable devices necessary for carryino' out the new process. By means of a suitable pump 5 the liquor is pumped through the pipings 4and 4 to the preheater 6 and the evaporator 7. The latter and the preheater may be of any suitable construction,.provided.that there is no possibility of a mixing of the liquor with the heating steam and its condensate. According to the conditions the evaporator 7 may be of a multiple effect andconsist of several units.

The evaporator 7 is heated by the exhaust steam'of the steam engine, by steam taken from this engine or delivered directly by the steam boiler. The heating steam asses through the tube 8 into the evaporator In the evaporator 7 the secondary steam is produced the pressure and temperature of which are suitable for the cooking of the cellulose. The secondary steam passes through the piping 9 and by way of the steam pipe 10 reaches the Acookers 1 so as to heat them. Together with the above mentioned abundance of the secondary steam, the steam delivered bythe steam pipe may also be led to the other consumers, i. e. (1) by way of the pipe 11 to the preheater 6 for the liquor, (2) by way of the steam pipe 12 to the evaporator 13 of the fresh water for the purpose of producing low pressure steam and (3) by way of the pipe 14 to other devices, for example to drying drums for finally drying the liquor for the purpose of a higher preheating ofthe cooking acid and so on.

The condensate of the secondary steam passes from the evaporator 13 and from the preheater 6 by way of pipings 15 to the preheater 16 for the fresh water. The fresh preheater 13.

pure condensate of After leaving the preheater 16, the cooled condensate of the secondary steam passes, by way of the piping 19, into the working plant. Before this steam is used, the volatile products may be separated by subjecting this steam to a fractional distillation.

From the evaporator 13 for the fresh water the low pressure steam passes through the steam pipe v20 into a drying chamber, a heating` system and other devices of the plant and may be used as an additional distillate for the boiler feeding. u

The condensate of the heatin steam which is led by the steam pipe 8 to t 1e evaporator 7 is passed by the tube 21 to the storage tank 22. This tank 22 may be provided with an automatically operating device 26 by which the purity of the condensate is controlled.

The pure condensate passes from the'storage tank 22, by way of the piping 23, into the boiler house and serves as feed water for the boiler. In case of contamination the condensate leaves the storage tank 22 by way of the pipe 24 and is used in the plant as hot water. Before t-he condensate leaves the tank 22 through the pipe 24, the heat of the condensate may be utilized as low pressure steam which is led away from the tank 22 by the pipe 25. This steam may be used in all cases in which an absolute purity is not re uired.

The thickened liquor is led by t e tube 28 into the tank 27. What we claim is: l 1. In a method of cooking sulphite cellu-v lose leading the liquor leaving the cookers into an evaporator, heating said evaporator by fresh steam to evaporate said liquor and returning the vapors produced to the cookers.

2. In a method of cooking sulphite cellulose, leading'the liquor leaving the cookers into an evaporator, heating said evaporator by fresh steam to evaporate said liquor and utilizing the vapors produced for any suitable purpose.

, 3. In a method of cooking sulphite cellulose, leading the liquor leavin the cookers into an evaporator, heating said evaporator by fresh steam to evaporate said liquor, separating all volatile products contained in the liquor coming from said `cookers by a fractional distillation and returning the vapors produced to the cookers.

4. In a method of cooking sulphite cellulose, leading the liquor leaving the cookers into an'evaporator, heating said evaporator by fresh steam to evaporate Isaid liquor, separating all volatile products contained in the liquor coming from` said cookers by a fractional distillation and utilizing the vapors produced for any suitable purpose.

In testimony whereof we have aHixed our signatures.

SERGEI I. TSCHUWIKOWSKY. GRIGORY I. LIACHOVETZKY.

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