US1814027A - System for cooking fibrous material - Google Patents

Description

July 14, 1931. T. DUNBAR SYSTEM FOR COOKING FIBROUS MATERIAL n Filed Aug. l, 1929 MHLHXH Enum 83% mkGU @h3 m @D gmnntoz T LDzmbar;

Patented duly 14, l93i UNITED stares THOMAS LEONIIDS DUNBAR, 0F WATERTOW, NEW YORK SYSTEM FOB COOKING FIBROUS MATERIAL Application led August 1, 1929. Serial No. 382,801.

This invention relates to improvements in the cooking or digestion of fibrous material'. In digesting brous material, it has been customary to place wood chips or the like in a digester, cover the same with acid liquor, and then introduce steam steadily from Athe beginning to the end of the cook. I have discovered that aA large proportion of the steam `may be saved, improved pulp may be prepared,- and/great economy may be realized, if the cookin 1s carried out in a certain way.

The gist o my invention resides in the introduction of steam intermittently during the greater portion of the cooking period, and the cutting off of the steam entirely during the latter portion of the cooking period. By such procedure, I have discovered that even though the feeding of the steam to the digester is stopped a few hours before the end of the cooking period, that the temperature in the digester will rise as much as 8 C., and this I attribute, either to an exothermic reaction, or to a progressive heat penetration from the center to the outer portion of the mass in the digester. v

The invention will now be described in detail in connection with the accompanying drawing, which shows a diagrammatic view of an apparatus with which my method may be practiced.

In the drawing, 1 designates an accumulator to contain pre-conditioned and preheated acid liquor under super-atmospheric pressure. Such liquor may be forced `by means of a pump 2, through a valved conduit 3, into adigester 4. Only one digester is shown in the drawing, but the present invention may be used in connection with any number of digesters, and each digester will be provided with the usual steam inlet pipe 5, a valved side relief branch 6, and a top relief 7. It is customary with such digesters, to use a thermometer 8, a pressure chart 9, a steam flow chart 10, and a recording thermometer 11.

Heretofore, chips or the like, placed in the digester, were saturatedwith either cold or pre-heated acid liquor, and steam was introduced into the digester from the start to the 50 finish of the operation. During the cooking period, gases, vapors and the like, were relieved from the digester. In such operation,

the pressure chart and the steam flow chart showed gradual curves from the start to the finish of the operation. v v

In accordance with my improved method, after a digester has been filled with chips or the like, hot acid from the accumulator 1 is pumped into the digester, and after` the di- -gester is filled with chips and hot acid, I normally run the pump 2 for a few minutes. This causes the liquor to penetrate the chips or the like, and puts a pressure in the digester without the addition of any steam. As soon as the digester has been brought up to a pressure from l0 to 65 pounds in this way, I begin to admit steam slowly into the bottom of. the digester, through the pipe 5, as has been customary in the past, but 1n accordance with my system, very little steam can be admitted at this time, due to the fact that a relatively high pressure already exists in the digester, and the latter is filled with chips. As soon as the steam is turned on, the side relief 6 is opened, so that the usual liquors are forced out of the digester, due to the pressure existing therein.

During the time steam is being admitted, and as soon as dry gases can be obtained from the top relief 7, the valve of the side relief 6 is shut off and from that time on the top relief is used.

As heretofore mentioned, I admit the steam in a different way from that used heretofore. For example, I admit steam for a certain period of time (say one-half hour), and then Y A 1 shut it off for a subsequent period of time (say twenty minutes). At the end of this period steam is again admitted for a certain time, then shut off, and so on. By admitting steam in this way, so as to produce the stepped chart l0, I actually accomplish a more uniform penetration of the chips with acid. In the usual method, of cooking, the steam is admitted constantly, so that the curve on the steam flow chart is gradual, instead of stepped, asin my system. Furthermore, in the usual method of cooking, the pressure advances in a uniform' manner, and the penetration of the chips and the distribution of the heat units throughout the mass of chips and liquor lags considerably behind, What would be expected at any given point, but by stepping up the steam fiow andpressure asl do, I find that in the intervals, `while the steam is shut off, the heat units have a chance to become more uniformly distributed, lthereby producing a better pulp and obtaining a higher yield.

In my method, I continue the step by step HOW of the steam until a temperature of about 124or 132 C. has been reached, and I then shut .off the steam entirely, and finish up the cookwithoutadmitting any more steam, and in this Way, I also save considerable on the steam, and 'produce a better pulp.

i As an eXample,I have discovered that on an eleven hour cook, I can complete the cooking process in exactly the same time as heretofore When steam was admitted until the cook Was finished; I also find that after the steam is shut off, that the recording thermometer used With the digester, showsthat the temperature continues to raise approximately 8 C. This maybe due to an exothermic reaction on it, or be caused by progressive heat penetration from the center to the outer portion of the mass.

The showing ofthe pressure chart 9, and steam flow chart 10 inl the accompanying drawing-is not -intended to be strictly accurate, but is merely to indicate what happens due to the step by step fiowof the steam, until the temperature reaches approximately 12,40 or 132 C., and then the shutting ofi" of said steam some hours before the end of the cooking period.

From the foregoing it is believed that the operation and advantages of the invention may be clearly understood, and it is manifest that changes may be made in the details vdisclosed, Without departing from the spirit of the invention, as expressed in the claims.

vWhat I claim and desire to secure by Letters Patent is A l. In the digestion of fibrous material with acid liquor, initially subjecting the fibrous material in a digester tohot acid liquor under pressure, and afterwards intermittently admitting steam to the digester and thus causing -.the pressure therein to build up step by step.

' In the digestion of fibrous material With acid liquor in a digester, initially subjectingthe fibrous material in the digester to hot acid liquor under pressure, afterwards introducing steam into the digester for a period of time` shutting ofiI the steam for a subsequent period of time. and subsequently again admitting' steam to the digester' for another period of time. all during the same cooking period.

3. In the diga-'fw of fibrous material `with acid liquor iu a digester, initially subjecting the fibrous material in a digester to hot acid liquor under pressure, and afterwards intermittently admitting steam into the digester during a single cooking period.

4. In thedigester of fibrous material, placing'such material in a digester chamber, substantially filling ythe chamber with hot acid liquor, then introducing steam intermittently into the acid liquor in the digester chamber. 5. In the digestion of fibrous material, placing said material in a digester chamber, forcing hot acid liquor into the digester chamber until the pressure therein is at least ten pounds above atmospheric, then intermittently introducing steam into the digester.

6. In'the digestion of fibrous material, plac` ing said material ina closed digester chamber, pumping hot acid liquor into the chamber until the pressure therein is at least ten pounds above atmospheric, and then intermittently introducing steam into the digester.

7.' In the digestion of fibrous material, placing said material in a closed digester chamber, forcing hot acid liquor into the chamber until a super-atmospheric pressure exists therein, intermittently introducing steam into the digester, and permitting gases and vapors, to discharge from the chamber While the fibrous material is undergoing cooking.

8. In the digestion of fibrous material With acid liquor in a closed digester chamber, introducing steam into the digester, shutting off the steam from the digester after the digester has4 reached a certain temperaturel and at least affew hours before the end of the cooking period, and permitting the temperature in the digester to rise after the steam has been shut ofi' and before the end of the cooking period.

9. In the digestion of fibrous material With acid liquor in a closed digester, feeding steam into the digester, shutting off the fioW of steam to the digester, and permitting the temperature in the digester to rise after the steam has been shut off and before the end of the cooking period.

10. In the digestion of fibrous material with acid liquor' in a closed digester, introducing steam into the digester and shutting off the flow of steam after the temperature has` reached a predetermined degree, and permitting the temperature in the digester to rise approximately 8 C. above said predetermined degree after the steam has been shut ofland before the end of the cooking period.

ll. In the digestion of fibrous material with acid liquor in a closed chamber, heating the interior of said chamber to a predetermined degree, and discontinuing the introduction of heat units into the chamber while permitting the temperature to rise therein several degrees above that which exists at the timeivhen the introductionof the heat units was discontinued.

l2.v In the digestion el fibrous material, confining such material with acid liquor in a closed chamber, introducing heat units into said chamber until the temperature therein has reached about 124 C., discontinuing the introduction of heat units into the chamber, and permitting the temperature to rise in the chamber about 8 C., after the introduction of .heat units has been discontinued.

13. In the digestion of brous materia confining a mass of such material and a pool 10 of acid liquor in a closed digester, introducing steam into the digester until the temperature therein has reached at least 124 C., then shutting olf the fioW of steam to the digester, and permitting the temperature Within the digester to rise about 8 C., after the steam flow has been shut off.

14. In the digestion of fibrous material, confining a mass of such material and a pool of acid liquor Within a digester, intermittent- 20. ly introducing steam into the digester until the temperature therein reaches at least 124 C., then shutting off" the flow of the steam to the digester, permitting the temperature in the digester to rise several degrees after the flow of steam has been shut off, and

then allowing the temperature to fall until the end of the cooking period.

l 15. In the digestion of fibrous material, confining a mass of such material in a digester, forcing hot acid liquor into the digester and in contact with the fibrous maferial until the pressure in the digester is at least ten-pounds above atmospheric, ythen intermittently introducing steam into the digester until the temperature therein reaches at least 120 C., then shutting off the flow of steam to the digester, permitting the temperature in the. digester to rise after the steam iow has been shut ofi', and then allow- 40 ing the temperature in the digester to fall to the end of the cooking period.

16. In the digestion of fibrous material, confining a mass of such material and a pool of hotpacid liquor in a closed digester, pumpling hot acid liquor into the digester and in contact with the fibrous material until the pressure in the digester is above 10 lpounds atmospheric pressure, then discontinuing the pumping of the acid liquor and introducing steam intermittently into the digester until the temperature therein has reached at least 124 C., then shutting off the How of steam to the diglestenand permitting the temperature in t e digester to rise after the steam has been shutoff and before the end of the cooking period.

In testimony whereof, I have signed this specification.

THOMAS LEONIDAS DUNBAR.

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