US443922A

US443922A - Digester

Info

Publication number: US443922A
Authority: US
Publication date: 1890-12-30
Anticipated expiration: 1907-12-30

Description

`(No Model.)

S; SMITPL DIGI-3 STER.

No. 443,922. Patented Deo. so, 1890,.

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WTNESSs:

ma Ncnms Finns co., Primo-Limo., wAsmNcn'oN, D1 c.

, IAUNITED `STATES. ATENT .SIDNEY SMITH, OF CAMBRIDGE, MASSACHUSETTS.

DIGSTER.

` SPECIFICATION forming part of Letters Patent No. 443,922, dated December 30, 1890.

Application filed April 9, 1889. Serial No. 306,589. (No model.)

To all whom t may concern:

Be it known that I, SIDNEY SMITH, of Cambridge, in the county of Middlesex and State of Massachusetts, have invented certain new and useful Improvements in Digesters, of which the following is a specification.

This invention relates to steam-boilers composed of two shells, one inclosed within another of a larger size, so that heat may be applied to the space between the boilers for the purpose of acting on substances contained within the smaller inside boiler. The invention relates particularly to such boilers as are used for t-he preparation of pure vegetable fiber from wood and other substances from which pulp is produced for paper-manufacture and analogous uses.

My invention has for its object, first, the construction of the two said boilers in such a manner that the inner one is completely enveloped by the outer one, so as to leave a continuous connected space all around, access to the inner shellbeingpossible onlythrough that of the outer boiler, and, second, the improvement of such boilers so that the inner boiler can be readily separated from the outer whenever it is desirable to make a critical examination of both shells for defects arising from acid leaking through, or from any cause whatever, and can be repaired in the cheapest, best, and quickest manner. The continuous space between the two shells is especially important in paper-manufacture where the coating or lining of the inner shell, to protect the shell from the action of the acid liquor, is produced by exterior heat from such a space, which precipitates upon the inner shell a firm durable incrustation.

The process of the formation of the incrustation when a bisulphite liquor is employed is believed to be as follows: The sulphurous acid is expelled from the bisulphite liquor by heat, producing monosulphite of calcium and free sulphurous-acid gas, thus CaH2(SO3)2-l heat=OaSO3+H2O+SO2- The nionosnlphite of calcium adheres wherever it comes in contact with a metallic surface which is heated from the opposite side. The other product of decomposition, which is sulphurous-acid gas, either bubbles up through the solution collecting in the upper part of the digester or attacks the gums and other substances which till the cells of the cellulose of the wood chips. In order that Stich a precipitated lining shall be even and continuous, it is necessary that the surface of the inner shell shall be perfectly smooth, with no projecting rivet or bolt heads or other protuberances, for the lining tends to scale off from projecting boltheads, and is formed most perfectly where the surface to be coated is very smooth and regular. I provide for such an even surface by count-ersinking all rivet-heads in the inner boiler, and by joining the plates by dovetailing and iilling the small spaces left with lead or any material which is not attacked by the contents of the digester. Both the inner and outer boilers are provided with suitable man-holes for the introduction of stock, and also with all necessary connections, gages,

thermometers, duc., required for the purpose of accurately determining the condition of the inner contents. To facilitate the removal of the inner boiler, I provide the same with wheels at suitable intervals along its outer circumference. These wheels run upon and are guided by suitable rails placed longitudinally along the inner surface of the outside boiler.

The outer boiler is provided with a removable head, so that by means of the wheels and rails described above the inner boiler can be run out and completely separated from the outer boiler. The inner boiler can be4 again run back into position within the outer boiler and the head of the outer boiler screwed on, producing a true jacketed boiler, as described previously. To firmly secure the inner boiler in place within the outer boiler or shell, I

IOO

longitudinal section of aportion of the inner shell. Fig. 4 represents a longitudinal section of another portion of the inner shell.

The same letters of reference indicate the same parts in all the figures.

In the drawings, a represents the outer or inelosing` shell, and Z1 represents the inner shell or digester proper. 'lhe outer shell is provided with a detachable head c, and may be supported in any suitable Way. I have here shown trunnions d d on theheads of the outer shell fitted in bearings e c., so that the outer shell with the inner shell therein contained can be rotated. The pipe fthat admits steam to the space between the inner and outer shells passes through one of said trunnions.

g g represent 'the wheels which are applied to the inner shell, 'said wheels being arranged to run on tracks h h, attached to or formed on the inner surface of the outer shell and extending lengthwise of the latter.

i' il represent the screws, which are engaged with tapped sockets or nuts in or affixed to the outer shell, and bear at their inner ends on plates jj, which rest on the surface of the inner shell. Said screws when turned inwardly press the plates against the inner shell and cause said plates to act as clamps or brakes, preventing independent movement of the inner shell.

fifi represent lock-nuts on the screws t' i, said nuts being arranged to bear on the outer surface of the outer shell.

m m represent the coinciding man-holes, with Which the two shells a and b are respeotively provided.

n represents the pipe which conducts the acid liquor into the inner shell when the latter is empty or before it is charged, for the purpose of forming the protecting coat or incrustation. Said pipe is arranged so that the streams of liquor forced through its numerous perforations will strike all portions of the inner surface of the inner shell or digester. rlhe inner shell may be rotated, if desired, during the admission of` the acid liquor through the pipe n, or the pipe may be rotated to more thoroughly distribute the liquor over the surface of the inner shell. I find that by thus Washing the inner surface of the digester with the acid liquor before charging the digester the protecting coat or incrustation is formed more quickly and thoroughly than when it is deposited from the charge of liquor afterthe digester is filled or charged.

The inner shell is made of plates 2 2 (see Fig. 3) of iron or steel, and to insure a perfectly smooth inner surface I countersink the heads of the rivets 3 3, that secure said plates, thus making said heads flush with the inner surface of the digest-er. For the same purposeI prefer to doveta-il and slightly separate the adjacent ends of the plates 2 2 and secure the same by means of extern al plates or bands 4, which are connected by the rivets 3 to the plates 2. The dovetail space between the ends of the plates within the band at is filled with a packing 5 of lead or other suitable acmresisting material Which is held in place by the dovetail form of the ends of the plates, the inner surface of the lead packing being flush with the inner surface of the' digester.

It will be seen that by removing one of the heads of the outer shell and turning the screws e' outwardly the inner shell can'be readily removed for inspection and repairs. The steam-space between the outer and inner shells is conti1'1uous-or, in other Words, eX- tends over the entire surface of the inner shell, so that all parts of said surface are exposed to the action of the steam or other heating medium admitted to said space, as already described.

In connection with the pipe 1t for spraying or Washing the inner surface of the digester with the acid liquor I prefer to employ a rota-ry brush h2, arranged to move over the 1nner surface of the digester and act after the manner of a paint-brush in spreading and smoothly applying the semi-Iiuid or plastic material left on the inner surface of the digester by the partial evaporation of the aqueous portions of the acid liquor. Said brush is here shown as attached by arms bi3 b3 to the pipe n, and maybe revolved over the inn er surface of the digester by the rotation of said pipe. The brush may be supported and operated in any other suitable Way, or may be held stationary While the digester is rotated. It will be advisable to remove the brush as Well as the pipe n before charging the di gestel.

I claiml. The combination of a steam-tight inclosing-shell having a removable end or head, means for detachably securing said head to the body of the shell, and a removable herlnetioally-closed inner shell separated from the outer shell by a continuous space, as set forth.

2. The hermetically-closcd inner shell or digester having wheels, combined with the steam-tight outer shell supporting said Wheels and havinga detachably-secured end orhead to permit the removal of the inner shell, as set forth.

3. The combination of the hermeticallyf closed inner shell or digester having the Wheels and the steam-tight outer shell having longitudinal tracks on Which said wheels are adapted to run, and adetachabl y-secu red end or head, as set forth.

4. In a digester, the ksteam-tight inclosingshell having a removable end or head, longitudinal tracks, and a man-hole, combined with the hermetically-elosed removable inner shell having wheels adapted to run on said tracks and a manhole connecting with the man-hole of the outer shell, and clamping devices or brakes interposed between the inner and outer shells, whereby the inner shell may be locked Within the outer shell, as set forth.

5. The combination, substantially as here- TOO inhefore sefforth, of zi boiler or digesier, :i heet to the Surface of seid digesier, substanperforatecl pipe or pipes within the same nrtinlly as seiI forth.

rangedto directstrea-ms of aeicl liquoraga-inst In testimony whereof I have signed my the inner surface of JLhe cligester, and means naine to lthis specification, in the presence of I5 for externally heating the digester. two subscribing witnesses, this 2d day of 6. The combination, with i digester and a April, A. D. ISSS). pipe for spraying or Washing the inner surface thereof with acid liquor, of u brush whereby the deposit formed on the inner surface of said digester by the acid liquor may he uniformly spread, and means for applying l SIDNEY SMITH.

Witnesses:

C. F. BROWN, A. D. HARRISON.