US1643566A - Process for bleaching and the like purposes - Google Patents

Description

PROCESS FOR BLEACHING AND THE LIKE PURPOSES Filed 001:. 16, 1925 2 Sheets-Sheet 1 Iwlef pass 16:

0112222 passage supply ZanKS 5 LL 2 26621 756 6077c em raior" 2a iq zaazz'zer' fewer" CiZzzZe 27 11" dza-mber Nozzle Tower C72 wi 3| Flql Patented Sept. 27, 1927.

UNITED" STATES PATENT OFFICE.

CARL BUBCE THOBNE, H AWKESBUBY, ONTARIO,,CA'HADA.

' PROCESS IORIBLBAOHING AND THE LIKE PURPOSES.

Application am October 18, 162 sum in. 68,873.

and the objects of the invention are to insure.

a regular and uniform supply of pulp to the bleaching apparatus, to re uce the period of time required for bleaching; to produce a pulp of better uality by the use of a new method of bleac ing partly. at hlghdensl'ty and partly at low density; to eliminate mechanical agitation of the pulp as much as possible; to produce a pulp of hlgher physical strength, of greater purlty chemlcally, of better color and superior in its cellulose properties; and generally to provide an efiicient, economical and faster bleaching method, and it consists essentially of the various steps performed in or about the order set forth in detail-hereinafter and set forth in the claims which follow the explanation of the invention.

In the drawings, Figure 1 is a dlagrammatic view showing the system of feeding the high density pulp bleaching agent and water ina continuous and uniform manner to the bleaching tower.

Figure 2 is a dia ammatic' view showing one arrangement or bleaching partly at hi h densityand partly at low denslty.

igure 3 is a dia rammatic view showing the new system of feeding comb ned with a system for bleaching partly at hlgh density and partly at low density.

Like numeralsof reference indicate corres onding parts in the Various figures.

n this method of bleaching it is not essential to' include allthe parts illustrated, as under certain conditions all of the bleaching may bedone at high density, instead of being 40 done partly at high density and partly at low density, and under other conditions the systemof .feeding may be simplified, for much .-'depends on the requirements of the trade and also "upon the local conditions where the process' is being used. This and the accom- 'aiiying application Serial No. 61,075, filed fctober 7, 1926 are made to clarify copend- 1 ing-application filed'under Serial Numbers 387 and 755,691, on December 6, 1924,

Q; December 13, 1924, respectively and are {intimately associated therewith.

- The supply of pul flows from the mill through the passage 10 to a concentrator 11 where suflicient water is taken from the pulp to bring it up to the desired density. From the concentrator the pulp flows through the outlet passage 12 to the equalizer tower 13, the bottom of which tower is of the hopper type, and inclined to a central outlet 15 around which the scraper arm 16 continually travels. The arm 16 is fixedly mounted on a shaft 17 extending centrally and vertically through the tower 13 and is suitably driven at a uniform speed. The arm 16 rotating at a uniform speed kee s a continuous stream of high density pulp, owing to the opening 15 along the chute'18 to themixer 19. The capacity of the equalizing tower 13 is such that it will produce a very uniform andeven flow at its ofpening .15 irrespective of whether the flow o pulp preceding the equalizing tower is uniform or not.

The chute 18 leads the ulp from the outlet 15 continuously towar s the mixer outlet 25. During its passage through the mixer, waterand bleaching agent are addedthrou h the pipes 20 and 21 respectively, from t 0 supply tanks 22" and 23, which tanks are fitted with the required flow boxes, so that exact quantities of water and bleaching agent can be continuously added.

The pulp, bleaching a ent and water are mixed by the rotating pa dles 24 and the resultant mixture discharges through the o ning 25 along the chute 26 to the bleac ing tower 27 through the inlet 28 at the upper end. This bleaching tower has three arms mounted on the central shaft 17, one a levelling arm 29, near the top of the tower for the purpose of levelling and spreading the mass out evenly as it enters the tower, another situated below the middle of this tower, this is a perforated arm 30, forming an air nozzle communicating with the interior of the shaft 17 which is hollow in this tower, this shaft in turn being connected to a compressed air supply. The third arm in this tower is a scraper arm at the bottom similar to the one in the equalizing tower, described above.

The tower 27 is of similar shape to the tower 13' and has the hopper bottom 31 and central outlet 32, and the scraper arm 33 maintains a continuous even flow of pulp mixture into the chute 34 leading to the washer 35, where the bleaching agent is washed out of the pulp and if it is desired toend the bleaching here, then the pulp proceeds to a thickener and from thence to a stock chest.

The method thus described points out a quick process of bleaching at high density, whereby the feed is regulated and automatically equalized, but it is not always desirable to complete the bleaching at high density, and in Figure 2 it is shown that following the high density bleaching performed in the tower 42 of the pulp received from the mixer 43, the resulting product is washed in the receptacle 35 and emptied into a suitable mixer 40 for a fresh mixing of the bleaching agent and. water and then passed on toa low density vat 41, many forms of which may be used, therefore it is not necessary to maintain an equal density throughout or keep to the hi h density, as for some manufactures low ensity bleaching can readily be introduced in conjunction with the high density when and where wanted. The process of bleaching in two stages, that is by partl bleaching at a high density and then comp eting the bleaching at a low density has proved to be most beneficial to the final-product and as a method of bleaching has never been known before, so far as I am aware. Also the mixing of the pulp and bleaching agent in a separate apparatus prior to the bleaching at high density is also novel, thou h in my copending application Serial Number 754,387, filed December 6th, 1924, it is described in connection with a high density bleaching system which also mentions bleaching by stages but each time at a high density.

There are, of course, a number of high density bleaching systems, any of which ma be used in connection with this rocess an also a great number of low ensity systems, and. naturally it is entirely a matter of choice as to the most desirable system, though so far as the high density system is concerned, it is preferable to use the particular process described herein and already mentioned in the earlier applicationv in order to obtain the best results.

In the high density bleaching1 system described above, the pulp is bleac d at a density of from 15 to 20% or more, while in the low density system the density may be from 10 to 5% oreven lower. The final product produced by the above system of bleaching is a pulp of higher ph sical strength, of greater purity chemical 1y, of better color, and superior in its cel ulose properties, also this better quality product is produced with considerable saving of cost in time, power and bleaching agent.

It is to be understood that while this process is intended mostly for the purpose of bleaching pulp for paper making, artificial silk and other manufactures, it may be used in many other arts, with advantage and economy, and the fact that while one use only is described herein, it will in no way confine the invention to any particular purpose or industry.

What I claim is 1. In a process of the character described, cons sting in concentrating the pulp for feeding purposes, then directing the feed into an enclosed passage and discharging it at the same rate, and thereby maintaining a column afiording constantly even pressure, then mixing the discharged pulp in passage with bleaching agent and water and dis" charging it to'the bleaching area and continuously delivering the bleached pulp at the same rate as the original feed.

2. In a process of the character described, consistmg in feeding the pulp at a regulated rate and pressure, then mixing the bleaching agent and water with the passing pulp and fixing the density, then partially bleaching the prepared pulp, then again mixing the partlally bleached pulp with bleaching agent and water and fixing a density varying from the aforesaid density and finally bleaching at the latter density.

3. In a process of the character described, conslsting in maintaining an even pressure at the feed discharge to the mixer, then fix ng the density for bleaching and introducing the bleaching agent, then slowly passing the pulp through the bleaching areaand comcidently expelling the decomposition gases by air under pressure, then mixing with bleaching agent and water and reducing the density and finally bleaching under ordinary low density conditions.

4. In a process of the character described consisting in building up two. columns of pulp continuously discharging at the lower end and fed by falling pulp .at the upper end to compensate for the discharge, introducing the mixing ingredients for the bleaching between said columns and be 0nd the discharge of the lower column, was ing and thickening prior to the second mixing and finally bleaching at low density.

5. In a process of the character described, the accumulation of pulp in a succeeding vessels partially fille the maintenance of a steady falling of the several accumulations, the passing of the pulp in an indirect passage from vessel to vessel and mixing t e bleaching agent with the pulp entering the second vessel, the feeding of air in the second accumulation in a direction contrary to the fall and mechanically dis tributing said air and passing the pulp on and finally finishing.

6. 1n a process of the character described, consisting in concehtrating the pulp at a high density and delivering in a falling mass, accumulating the falling mass below the fall and forming a non-turbulent mass constantly discharging at the rate of the fall, agitating the discharge and directing it (plurality of lni) under a regulated feed of bleaching agent and water, passing this on to a second nonturbulent mass constantly added to and discharging, and feeding compressed a1r through the bleaching mass in a direction contrary to its fall.

7. The herein described process of bleach ing pulp, consisting in feeding the pulp to the bleaching zone, mixing the pulp with the bleaching agent and water and bleaching, repeatin the aforesaid steps and varying the density of the pulp relatively in respect to said repetitions.

8. The herein described process of bleaching pulp, consisting in feeding the pulp, regularly to the bleaching zone, mixing the pulp with the bleaching agent and water, bleaching at a density of pulp of to subsequently mixing again with the bleaching agent and water and bleaching at a density of, pulp of-10% to 5%.

9. The herein described process of bleach-' ing pulp, consisting in pouring out a stream of dense pulp and forming a column thereof, mixin a bleaching agent and water with the pulp alling from said column, discharging the pulp mixture to the bleaching zone and. forming another column, in which the bleaching occurs, and aerating during the operation'of the bleaching agent.

10. The herein described process of bleaching pulp, consisting in concentrating the pulp, continuously discharging and forming a stream-of falling pulp, introducing a bleaching agent and water intermediately of the height of the stream without interrupting its'flow, bleaching the pulp in passage following the mixing of the bleaching agent and dischargin the continuously flowing stream and was ing.

11. The herein described process of bleaching pulp consisting in concentrating the pulp, discharging the pulp in a falling mass, accumulating the falling pulp, regulating the fall below the accumulation, agitating the pulp falling from said accumulation and coincidently mixing therewith a bleaching agent and water, continuously discharging the mixture, then bleaching the falling pulp and distributing air therein and maintaining the mixture in a non-turbulent condition during the bleaching and aerating and then washing.

Signed at Montreal, Can. this 26th day of September, 1925.

CARL BUSCH THORNE.

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