Патент USA US2115835код для вставки
May 3, 1938. 2,1 15,835 D. J. YOUNG SULPHATE PULP PROCESS Filed Sept. 15, 1937 mx/ m:.PQutahlnbio 3u» QN d„oWn.qìvldî tKxHwShm," a M/w Mw, www . . i. M, _. MM Patented May 3, 1938 y J UNITED STATES PATENT OFFICE I - 2,115,835 SULPHATE PULP PROCESS Daniel J. Young, Tacoma, Wash.,> assignor to Young-.Whitwell Gas Tacoma, Wash. Process Company, ’ Application September 15, 1937, Serial No. 163,973 3` Claims. (Cl. 92--9) The invention relates to improvements in the process of treating wood and like cellulosic mate- would be a distinct asset to the community pro vided the obectionable odors resulting therefrom rial for the formation of pulp, and more partic- could be eliminated. ularly to the elimination of objectionable odors 5 which are especially characteristic of the manu- facture of pulp by the sulphate procesjs. It is. known that the‘ gases resulting from sulphate pulp manufacture contain certain non-conden- - The primary object of the present inventio is to withdraw the objectionable gases directly Ul from the digester before they have become diluted with air and to preferably burn them or other wise dispose of them in a manner which is not sible components having an extremely nauseating 10 odor and consisting largely of combustible mercaptans and the like.’ In the ordinary method of manufacture of sulphate pulp the cellulosic materials to be treated- objectionable. 'I'he ordinary equipment may be maintained practically without change, it-being 10only necessary to add a condenser communicat ing with the top of the digester through a valve connection, the condenser being equipped with (usually Wood chips) together with the usual 15 chemicals are placed in the digester and steam is a gas offtake leading to a gas holder or the like to which the non-condensed vapors are conveyed 15 ~ admitted at or near the bottom of the digester until the pressure within the digester reaches about 125 to 135 pounds with the consequent tem- perature within the digester from 350° to 400° F. and from which they may be withdrawn for burning or other unobjectionable disposal. The invention will be more readily understood by reference to the accompanying drawing in 20 This condition may be maintained for a period of about one and one-half hours and is known as the “cook”. When the pulp has been suiiiciently cooked the steam is turned orf, the bottom of the digester is opened and the pulp is discharged' into which there is illustrated somewhat diagram 20 matically a sulphate pulp digester of conven tional type equipped with the improved connec tions whereby the malodorous gases may be with drawn and disposed of without pollution of the 25 a closed. tank generally known as the blow pit, atmosphere. in which tank the liquor containing the chemicals and the pulp are held and the excess steam and gases resulting from the cook are carried away and condensed, the non-condensible gases 30 being then usually discharged at the base of the Referring to the drawing the reference nu- “ meral I0 denotes a digester of any desired type being approximately 10 feet in diameter and 60 feet high although obviously- not limited to these proportions. The digester is i'llled with wood 30 boiler stack, coming out of the top of the stack with the gases from the boiler. As the process is nowv carried outy a large amount of air is taken in with the gases and 35 steam so that the gas as admitted to the bottom of the stack is practically> all air though containing the mercaptans. These mercaptan gases being combustible, many eiïorts have been made to burn them at this time but due to the extent 40 of dilution with air such attempts have proved unsuccessful. ~ o The total amount of mercaptans produced during the process is relatively small, that produced in a digester approximately ten feet in 45 diameter and sixty feet high, which was studied in connection with the present invention, being about 100 to 150 cubic feet each time the digester _ is blown, a blow taking place about once an hour. However, when these gases are allowed to pass 50 unburned into the atmosphere the objectionable odor may be observed for a. distance of many . ' n chips and chemicals to a level II at approx imately two-thirds the height of the digester’. The steam inlet I2 may be provided near'the bottom of the digester and a removable lcap I3 is shown at the top to permit charging of the digester and also for the preliminary discharge of air prior to the digestion proper. The digester is provided with a bottom I4 through which the digested materials may be discharged into a blow pit I5 of conventional form. The blow pit is 40 shown as provided with an offtake I6 for gas and steam leading to a condenser I1 provided with a liquid outlet I8 and a gas outlet I9. Ordinarily the gases passing from the outlet I9’are so diluted with air that it is impossible to burn the mer- 45 captans contained therein. ' According to my invention an outlet pipe 20 for gas and steam is provided at the top of the di gester, such outlet being preferably provided with a. valve 2|. The pine 20 is preferably of 50 relatively small diameter so as not to interfere miles. The nuisance is so great that in many with the pressure which is maintained within the communities sulphate plants are not permitted digester. The pipe 20 leads to a condenser 22 to operate simply on account of the odor al- _ which may be of the surface type or of the type 55 though from a business standpoint such a plant commonly used in gas plants and referred> to 5'5 Z 2,115,835 as the scrubber. The condenser is equipped with a liquid outlet pipe 23 and- with an ofitake pipe. ' 24 for non-condensible gases. These gases in clude the mercaptans in sumcient quantity for combustion. 'I'he pipe 24 communicates with a gas holder 25 which may be of conventional type and which is shown as equipped with an offtake 26 controlled by a valve 21. 'I'he oiïtake 26 may lead to a suitable burner Where the mer 10 captans or other malodorous gases are disposed of instead of being discharged directly into the atmosphere. According to my method after the digester has been charged steam is admitted at the bottom 15 of the digester and the cap I3 is left open for a short time until the air has been swept out of the digester by the steam. The cap I3 is then closed thereby maintaining the digester air-tight. Further steam under pressure is admitted to the 20 digester and continues to ilow in sufiicient amount to maintain the pressure in the digester from 125 to 135 pounds more or less. As this steam ilows upward through the pulp and liquor it will force the steam and gases which are above the 25 liquor out through the pipe 20 into the con denser 22 where the steam and other condensible portions will be separated from the non-con densible gases, which are being conducted to the gas holder from which they may be periodically withdrawn for burning. According to this meth od no air will be present with the gases and they can be satisfactorily burned. During the cooking process the valve 2| may be opened either intermittently or constantly. If desired two or more digesters may be used in battery, the steam and gases from one digester passing into a sec ond one thus more eillciently utilizing the heat` of the steam. After the digesting process is completedr‘the 40 pulp and liquor from which the malodorous gases have been substantially completely driven will be discharged into the blow pit in the usual man ner and any gases remaining n therein will be passed to the condenser I1. Since the mercap tans have been eliminated during the digesting period there is no objection to passage-of the non-condensible gases through the outlet I9 di rectly to the atmosphere, since such gases-are substantially wholly air. 60 The invention has been described in detail with reference to a particular form of apparatus but it will be understood that many diiîerent coni binations of operation may be employed without departing from the spirit of the invention which 55 consists brieiLv in withdrawing the gas and suill cient steam to carry the gas, from _the digester during the digesting operation, condensing the steam from the gas and conducting the gas to a place where it may be burned, care being exer cised to prevent an excess of dilution byair, the gas being at all times kept in closed containers or pipes until it is burned. thereby preventing malodorous gases from escaping into the at mosphere. I claimz- ' 1. The improvement in the process of treating sulphate cellulosic pulp contained in a digester, for the purpose of avoiding contamination of the atmosphere with malodorous sulphur con taining gases; which comprises sweeping out sub stantially all of the air from the digester prior 10 to the commencement of the cooking process, then admitting to the digester steam under pres sure to perform the cooking operation, and dur ing the cooking stage withdrawing the resulting gases and vapors from the digester substantially free from air, separating the condensible from the non-condensible portions containing the mal odorous constituents without introduction of air, and burning said non-condensible portion. ‘ 2. A combined process for treating sulphate 20 cellulosic pulp contained in a digester and dis posing of the resulting malodorous sulphur con taininggases without contamination of the at mosphere; which comprises sweeping out sub stantially all the air from the digester prior to 25 lthe cooking process. then cooking the pulp and during the cooking process and prior to dis charging the pulp _from the digester, withdraw ing the gases and vapors resulting from the cook ing operation substantially free from air, sep 30 arating the condensible portions from the non condensible portions containing the malodorous constituents without introduction of air, and burning said- non-condensible portion whereby the malodorous gases are destroyed. 3. A. combined process for treating sulphate cellulosic pulp contained in a digester, and for eliminating the resulting malodorous sulphur containing gases without contaminating the at mosphere; which comprises conducting the treat 40 ment of the pulp in the digester in two distinct stages, the ilrst of which comprises sweeping out substantially all of the air from the pulp prior to the commencement of the cooking process, and the second of which comprises cookingl the pulp 45 from which air has been driven off while avoid ing the admission of further air, and during the cooking process and prior to discharging the pulp from the digester, withdrawing the gases and vapors resulting from the cooking operation from 60 the top of the digester, separating the condensi ble from the non-condensible portions contain ing the malodorous constituents without intro duction of air, and burning the combustible con stituents or said non-condensible portion where 55 by the malodorous gases are destroyed; the pulp _ being discharged from the bottom o'f the di gester after the gases and vapors have been with drawn. DANIEL J. YOUNG.