US551890A - Method of digesting wood pulp - Google Patents

Description

(No Model.)

M. L. GRIFFIN & P. 0. LARSEIL.

METHOD OF DIGESTING WOOD PULP.

No. 551,890. Patented Dec. 24, 1895.

r UNITED STATES PATENT OFFICE.

MARTIN L. GRIFFIN AND PETTER o'r'ro LARSEN, F LIEQIIANICSVILLE,

' NEW YoRK.

MET-HO D OF DIGESTING wooo PULP.

SPECIFICATION forming part of Letters Patent No. 551,890, dated December 24, 1895. Application filed N v m er 30, 1894. Serial No. 530,423. (In; specimens.)

steady and continuous increase in energy during the operation of cooking, insuring a continuous and steady rise in temperature of the whole mass, and utilizing the excess of gas and liquor during the first part of the operation before the cooking commences, and also utilizing the excess of gas, liquor, and steam during the'cooking operation by discharging the same into a succeeding charge of liquor in a tank containing partially-prepared liquor and thereafter supplying the digester with this prepared cooking liquor.

In carrying out this invention it is preferably employedin connection with the wellknown process of digesting wood by the sulphite process.

In the accompanying drawing is shown an apparatus to illustrate the manner of working this process, consisting of a digester, a

tank for containing the partially-prepared cooking liquor,- a blow-0E pipe connecting the digester with said tank, and so much of the well-known pipe connections as are necessary for setting forth this invention.

A is the digester constructed in the wellknown way for digesting wood pulp and provided with the opening B in its top through which the charge of wood is passed into the digester, and having the cover 0 adapted to be secured over the opening B.

In charging the digester it ,is preferably practically filledwith chips of wood and supplied with cooking liquor through any suitable pipe connection-'as, for example, the

pipe H shown as broken away and connected with a suitable supply-tank F.

I is a blow-01f valve for the discharge of the cooked mass. c

The cooking liquor is supplied so as to cover the chips of wood, leaving no appreciable space for condensation of steam.

The cooking liquor may, for example, be composed of about one and forty. one-hundredths to one and fifty one-hundredths per cent. of lime, magnesia or other, alkaline base; about one and seventy-five one-hundredths per cent. of combined sulphurous-acid gas, and about two and fifty one-hundredths per cent. to two and seventy-five one-hundredths per cent. of free sulphurous-acid gas.

In the commencement of the operation, steam is admitted to the digester through the pipe D from a suitable source. To facilitate the admission of the steam and provide for condensation a pipe E is employed of suitable acid-resisting material, which is constorage reservoir or tank F, containing a charge of partially-prepared cooking liquor having about one and fifty one-hundredths per cent. of baseand one and seventy one-hundredths per cent.'of combined and the same amount of free sulphurons-acid gas. This partially-prepared liquor is in this way supercharged with s'ulphurous-acid gas, which renders the liquor more efficient in the cooking, .producing a whiter and more uniformlycooked mass. The pipe E is provided with a valve G by means of which the flow of liq uor, gas, and steam through pipe E from the digester A to the tank F is regulated.

. As heretofore stated, in the commencement of the operation steam from a battery of boi iers is admitted to the digester through pipes I), the valve G is opened and a'continuous discharge of liquor andgas from digester A into tank F, containing the partly-prepared cooking liquor, takes place during the first part of the operation, until the temperature of the mass in the digester reaches abput 212 Fahrenheit, and after said temperature is reached and the cooking commences acontinuous discharge of liquor, gas and steam takes place from digester A into the tank F, containing the partially-prepared cooking liquor. Dur ing this operation, properly conducted, we are able to raise and maintain the proper pressure and degree of heat by so regulating the valve G that it will discharge only a volume of liquid equivalent to the amount of steam entering the digester through the valve D. For instance, suppose we admit steam to digester at eighty pounds pressure through a three-inch pipe and valve D, the area of whose orifice is seven square inches.- It would require an orifice at G whose area was foufand nine-tenths square inches to discharge the water of condensation under practically no head, while at the same time the temperature of the contents of the digester wouldbe continuously rising. ;As soon as a temperature of reached, when an orifice, as at G, whose area is;

only twenty-five one-thousandths of a square inch will be ample for the discharge of the condensation of the current of steam entering at full head through the orifice at D, and pro- .vided the same would be all condensed, which of course it would not.

Neither wouldit be necessary, but in fact undesirable, to admit a continuous current of steam ,of a constantquantity during the whole period of cooking.

The amount of liquor to be discharged will be equivalent to the amount of condensation of the steam, which will be about twenty per cent. of the quantity contained in the digester. It will be necessary to relieve the gas and liqnor in such quantities continuously. as to insure a continuous rise in the temperature of the mass.

As the bulk of the condensation takes place in raising the mass to 212 Fahrenheit before the liquor exerts any marked cooking action,

the liquor displaced by the con'densation'of steam is available for a subsequent cooking operation, and the excess of gas discharged simultaneously with the liquor into the tank D will increase the strength of the liquor contained in it from about three and forty onehundredths per cent. ofsulphurous-acid gas to about four and fiftyone-hundredths per cent., besides raising the temperature of the same to a considerable degree.

It has been the practice when the pressure in the digester is equal, or nearly so, to the pressure of the steam entering, and the temperature of the contents of the digester does 1 not correspond to the pressure, to relieve an afresh and quickly raising the temperature through an indefinite numberof degrees,until as follows:

The advantages of our improved process are First; At the beginning of the cooking operation we set the steam-valve for the steam entering the digester so as to insure a cont-1nuous and steady flow of live steam into the I mass to becooked.

Second. At the same time we open the valve G in the dischargepipe just enough to discharge a volume of liquor equal to that resulting from the condensation of the entering steam,.and thereby insure a continuous and steady rise in temperature of the entire mass.

Third. By our process we carry forward the entire operation of cooking the wood by a steady and continuous increment of energy, including the preparation of and adaptation of the liquor best suited for the mechanical part of the process set forth, thereby eliminating the contingencies and uncertainties attendant upon the present mode of reducing wood to fiber.

Fourth. We are also able'to reduce the labor properly adjusted no further labor or attention vbecomes necessary until near the close of theoperation, whereas with the present mode of procedure the constant attention of skilled 7 cocks is required.

Having now described our invention, what we claim is Q 1. The herein described method of digesting i wood by the sulphite process, which consists in admitting steam to the digester containing a charge of chips and cooking liquor, maintaining a continuous discharge of liquor and gas from the digester into a tank containing partly prepared cooking liquor, until the cooking begins, and then maintaining a continuous admission of steam into the digester and a continuous discharge of liquor, gas and steam wood, which consists in filling the. digester practically full of chips and cooking liquor.

covering the chips, admitting steam to the digester, maintaining a continuous discharge of liquor and gastrom the digester into atank containingpartlyprepared cookingliquor uno ls acid gas for the preparation of a fresh til' the cooking begins, regulating the discharge of cooking liquor. charge of steam entering the digester, and In witnesswhereof wehave hereuntosetour maintaining during the cooking a continuous hands this 14th day of November, 1894.

,5 admission of steam into the digester and a 7 continuous discharge of liquor, gas and steam MARTIN GRIFFIN into the tank of partly prepared cooking 1iq- PETTER. OTTO LARSEN' uor containing about one and one-half per Vlitnesses: I cent; of lime orother alkaline base, and three NEWTON T. BRYAN,

1o andfortyone-hundredthspercent.of sulphur- FRANK A. CURLEY.

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