US2263903A - Apparatus for the extraction of cellulosic fibers from vegetable material - Google Patents

Description

Nov. 25, 1941. u PQMILIQ APPARATUS FOR-THE EXTRACTION 0F CELLULQSIC FIBERS FROM VEGETABLE MATERIAL Filed July 16, 1937 5 Sheets-Sheet 1 I NVE N TOR UMBEETO POMILIO B mww HTTQRNEYS APPARATUS FOR THE EXTRACTION OF. CELLULOSIC FIBERS FROM VEGETABLE MATERIAL Filed July 16, 1937 5 Sheets-Sheet 2 Nov. 25, 1941. u. POMILIO 2,263,903

I N V E N TO R U BER-r0 PaM/uo ATTaENEYS Nov. 25, 1941. u. POMILIO 2,263,903

APPARATUS FOR THE EXTRACTION OF CELLULOSIC FIBERS FROM VEGETABLE MATERIAL v Filed July 16, 1957 T 5 Sheets-Sheet 3 I NVE NTOR UMBERTO Pom NOV. 25, 1941. u POMILIQ 2,263,903

APPARATUS FOR THE EXTRACTION OF CELLULOSIC FIBERS FROM VEGETABLE MATERIAL Filed July 16, 1937 5 Sheets-Sheet 4 "Nam-oz umgggro POM/L10 8 v Md-W Nov. 25, .1941. u. POMILIO 2,

APPARATUS FOR THE EXTRACTION OF CELLULOSIC I FIBERS FROM VEGETABLE MATERIAL Filed July 16, 1937 5 Sheets-Shgt 5 I 1 Ii v 0 INVcNro'R f UAfIdERTo FBI-114.1:

AQQM firmer/5Y5 Patented Nov. 25, 1941 APPARATUS FoR THE EXTRACTION F CELLULOSIC FIBERS FROM VEGETABLE MATERIAL 1 Umberto Pomilio, Rome, Italy, assignor to Pomilio 2,263,903 I C E Corporation Limited, London, England Application July 16, 1937, Serial No. 153,993 In Great Britain August 15, 1936 3 Claims.

The invention is for improvements in or relating to apparatus for the extraction of cellulosic fibers from vegetable material and particularly from vegetable material such as the stalks of the velocity at which the reactions take place and the rate at which the heat evolved is dissipated through the mass of the material and through the walls of the reaction vessels. The velocity at which the reaction takes place in the alkali wheat. barley, oats, rice and other cereals, and 5 treatment is dependent on the amount of alkali of flax, maize, cotton, hemp, and from material emcriiltoryedtfor aflgiverihweiglliitlof materialtreated such as sisal, phormium tenax, bagasse, different an e s reng 0 e a a 1 so u ion.

grasses such as esparto, tow-residues and A feature of the invention consists in emp yresidues from the manufacture of textile matein e a i in q ah eS only j s fll t t rials. One of the objects of the invention is to react with and/or dissolve the encrustmg subproduce cellulosic fibers suitable for the manustances referrvlelii to abo there s ot be facture of high-grade and other forms of paper an xcess of a a and cardboard and the like The c ll l io A further feature of the invention consists in fibers which are present in the materials set out employing a alkali lu 6 a Caustic soda above are for the most patrtdembtelllided in ligneous i gilg 213111 1237 8? zgf r g-tivwlgigpilfiigss S8; or woo y mater encrus e wi waxes, resins, 1 n is e ectic, mucic nd albuminous matter d mi the reacting substances are selected to be one eral compounds (e. g. silica compounds). It is p y Weight o e able te ial to f0ur to already known how to extract the cellulosic fibers SIX pa s of the so utio :I'he reaction 1s carried by dissolving out the above mentioned substances 2 out 1n an open vessel without p e su e for a by eating the li mate t t i i S21E21 if?Th2;Jiitflfitfifififlitt E; 312 and chlorine. The a all removes a su s an ia part of the encrusting b t while t solution, the extent of the mitial dlsmtegratlon chlorine reacts with the ligneous of woody matof t material a i th r tu y va y t-er. The concentration of the alkali solution 25 fIOm usually t been g i is 21SZ Zxfiifiitii is iiffiit 3552352??? amounting 0 107 or hig er, and sim ar y, where chlorine has been used, it has been em- 3 3 21 9 5 l g ig fi g i ployed in an undiluted state. Paper manufac- 6 1g 6 m 9 6 5a 6 me tured from the resulting fibers has tended to be 30 g g a e g y ge harsh and crackly. 0

It has now been f d that inter alia the fibers, in addition to being adversely affected by temperature under which the alkali reaction of gg t ggg fig i gfi z gg igig i wgl g the above treatment is carried out afiects the 1 of e fiber strength thirtieth a tars: that high temperature COIldltlglgS tend to damage takes place and the at Whicr the heat s the fiber, for example the fi r is increasingy damaged with the increase of temperature over fz i gi gfig gt giif g fg ig and ggg g ggg 22 E221 i figggifi: and mgh 40 An important feature of the present invention According to this invention a proce'ss for the consists in effecting the chlorination treatment of the vegetable material bycausing chlorine gas extraction of cellulosrc fibers fromvegetable madiluted with air to be conducted through the terial comprises treatmg mammal m terial Preferably the chlorine gas and reacting vessel with an alkali solution under cond1t1ons mass both moist with water The function for complete reaction with substantially all the t t t f th t ted teri 31 to of the air is twofold. It reduces the velocity at an g ter de which the reaction takes place and thus the rate vesse w was e W wa a at which heat'is evolved, and it also forms a vewaten ng the matenal' treatmg.the w hicle for conducting away the heat. Furtherntatenal another open Wlth c lorme gas more, due to the moisture the resulting hydrodfluted Wlth under condltlons for complete chloric acid is of such a dilution as to be less reacmm i substantially? the lignemls F- harmful to the cellulosic fibers than if the chloterr e e the mammal m the last 551d rine is dry. The proportion of air used with the Vessel 1m1 ned1ate 1Y upon compktlfm of the chlorine is dependent on the nature of the vegetion and lmmelfismg the matePal m a colfi Water table material being treated and it may vary bath, transferrlhg the matfina1 t a Sald h from .5 to 1. part by volume of air to one part to another vessel and treating it with an alkali by volume of chlorine, while the moisture solution for dissolving the previously reacted subt t of the chlorine may be up to its Saturation Y stances. Since the react1ons are exothermi e point and the moisture content of the mass may tempe atur s built p are d p nt t a n be two to five times the dry weight of the mass itself.

The rate at which the chlorine-air mixture is passed through the vegetable material also varies with the nature of the material being treated,

since certain materials can be treated at higher temperatures than others without adversely affecting the cellulosic fibers. For example, wheat straw may be treated up to a temperature of 55 C. while hemp straw may be treated up to 65 C. The rate at which chlorine may be passed through the material per pound of the material per hour varies from of a pound to V of a pound. The length of the chlorination treatment may vary from half an hour to three hours.

The process according to this invention in-.

volves reactions which are controlled as to concentration of solutions, maximum temperature rise and time of treatment, which reactions are carried out successively in separate reaction chambers. in reducing to a minimum the time when the fibres are in contact with the hydrochloric acid resulting from the chlorination, for example, the mass is immersed in cold water as soon as the chlorination is complete.

A further aspect of the invention consists in that the vegetable material is subjected to a further treatment with alkali after the chlorination treatment. As already indicated, the first alkali treatment is carried out under conditions which remove a substantial part of the encrusting substances and do not attack the: ligneous matter. Thus, in a 881156111118 first reaction is a partial reaction. The chlorine treatment reacts with the ligneous matter-and forms chloro-ligriine compounds. These compounds may not be entirely removed by the immersion in water and the function of the second alkali treatment is to dissolve out these chloro-lignine compounds. The strength of the alkali solution employed for this latter treatment may be as low as .l%. The quantity of solution employed is from 5 to 20 parts by weight of solution to 1 part by weight of vegetable material. As a rough guide the quantity of alkali required in the last alkali treatment is less than half that employed in the first treatment. The temperature at which the reaction takes place may be up to 100 C., and the length of time of the treatment may be as low as a few minutes.

The plant employed may embody an apparatus for mixing solid divided material, such as the aforesaid chopped vegetable material, with a reacting liquor, such as the alkali, which appa ratus comprises a hopper or thelike arranged above an elongated mixing chamber having a bottom wall sloping in the direction of the length of the chamber. a conveyor in said chamber arranged to traverse the material from the deep end to an outlet at the shallow end, means for introducing the reacting liquor at a controlled rate to said chamber. By these means the material can be-arranged to pick upor absorb the desired quantity of liquor during its passage through the mixing chamber. The mixing chamber may be. provided with two outlets, one at each end thereof, and with an inverted V-shaped bottom wall and said hopper may be disposed above the apex of the Vj-shaped bottom wallso that the conveyor is arranged to traverse the material outwardly from said apex to'said out lets. An inverted V-shaped deflector may be disposed above the centre of the conveyor and said hopper and means may be provided for ad A feature of the invention consists.

aaeaeos to one side or other of the said V-shaped deilector.

The plant may also embody an apparatus for extracting compacted masses of interlaced fibers from the bottom of treating towers or the like, which apparatus comprises a number of parallel or horizontal shafts spaced apart and having radially extending arms and means for driving adjacent shafts in. opposite directions. Means may be provided for varying the distance apart of said shafts.

In an apparatus for the extraction of cellulosic fibers from vegetable material by successive alkali and chlorine treatment, means are provided for converting the material to a fioccular state after the removal of the liquor in the alkali treatment and a blower connected with a suitable conduit is provided for conveying by cold air the floccular material in a divided state to the top of the chlorine tower. A receiving chamber may be arranged over the top of the chlorine tower which is provided with a deflecting wall on to which the floccular material is directed by said conduit and is thereby caused to fall into said tower.

The following is a description of one form of apparatus for carrying out the process described above, reference being made-t0 the accompanying drawings in which:

Figures 1a and lb taken together represent a side elevation of the plant showing diagrammatically the general arrangement.

Figure'2 is a vertica'lsection on the line 22 of Figure la showing the alkali towers'in elevation.

Figure 3 is a section through a tower on the line 3-4 of Figure 1.

Figure 4 is an enlarged view of one of the mixing devices of Figure 2.'

iustably directing the material leaving the hopper Figure 5 is an enlarged view ofthe mechanism for tilting the hopper nozzle as shown in Figure 4.

Figure 6 is a side elevation of the device shown in Figure 5. 4

Figure 7 is a plan view of the extractor for the reaction towers.

Figure 8 is an elevation of the arrangement shown in Figure '7.

Figure 9 is a cross section on the line 8-9 of Figure 8.

. Assuming stalks orstraw of plants, such as are referred to at the commencement of the specification, are to be treated, these are cut into lengths of a few inches and are loaded into hoppers l0 arranged at the top of the apparatus. The apparatus about to be described is designed for producing about 15 tons of cellulose per day. Each hopper is arranged to deliver the material to an apparatus II which mixes the stalks with an alkali solution in, the required proportions and delivers the" mixture to the upper ends of a pair of vertically-arranged reaction towers l2. Each mixing apparatus thus serves two towers, and comprises a long horizontally-disposed chamber "open at the top, the lower wall ll of which is inclined downwardly from each end to the centre to form a V. A screweconveyor .15 is horizontally-disposed along-the length of the chamber and has two sets of helical blades arranged end to end, which blades vare oppositely pitched to one another, and are driven by a motor 22. Disposed above the chamber and at the centre of the screwconveyor is a V-shaped deflector I6. The hopper is arranged to deliver the material on to the deflector through a flexible nozzle I! which may be swung from one side to the other of the V-shaped aaeaoos deflector thereby adiusting the relative quantitles of the material being fed to the two towers. The movement of the nozzle may be effected by a hand wheel ll to a worm shaft I! in engagement with a rack 2| secured to the ironic. The wormshaft is mounted in a bracket 2| secured to the chamber l5. Caustic soda solution is supplied to the chambers through a conduit 23 and a suitable device for maintaining a constant level of the solution in the V-shaped recess in the bottom of the chamber but which level does not reach the blades of the conveyor. As already indicated," the strength of the solution may be from 1 to 2%. Each end of the chamber is open and the screw-conveyor forces the material mixed with the alkali out through said open ends from which mixture drops into the open end of the reaction tower l2. s

The reaction towers may be about 34 feet high and in cross-section are flattened oval-shaped (as will be seen from Figure 3), the smaller dimension being about inches and the larger dimension 8 feet. The conveyor I 3 is so arranged as to eflect a mixture of straw and solution in proportions of one of straw to four of the solution. Steam is introduced through the walls of the tower by a number of pipes 24 in a zone substantially above the horizontal centre line, e. g. onequarter of the length from the top. The steam generating plant 25 and main delivery pipe 2 are shown to the left of Figure l. The mass of material gradually descends under gravity and becomes compacted as it descends, and at the bottom forms a seal which prevents too rapid an escape-of the liquid. The time of descent may vary from one to four hours according to the nature of the material and the strength of the caustic solution. During this time the alkali is almost completely used up'to form spent liquor of a dark colour. The tower is provided with inspection windows 9 and sockets 8 for thermometers at different heights.

When the mixture arrives at the bottom of the tower it is in the form of compacted interlaced fibers whence it is removed by an extractor ll, the speed of extraction beingadjustable; thus, the time of treatment may be varied.

. 42 to an opener 43 having spiked rollers or combs where it is converted into a floccular state. It is then raised by air blowers 44 through suitable conduits 4| to a receiving chamber 4! arranged I above the upper end of a set of chlorinating towers 41. The upper ends or the chiorinating tow-- ers are open and the conduits 45 are directed on to a deflecting plate 4. in the collecting chamber 46 whereby the floccular material-is caused to fall into the towers. This treatment results in the floccular material having a dryness factor of from about 25 to 40, i. e. 75% to 60% water and 25% to 40% bone dry material.

These towers may also be about 30 feet in height although those shown in thedrawings are shorter.'-' They are of a flattened oval shape in cross-section, the general dimensions being the same as those of the alkali towers. Chlorine is introduced into the fibrous mass at a zone about 10 feet from the top of each tower. As already indicated the top of each tower is open but the 10 foot column of fibrous material above the zone is sufllcient'completeiy to absorb the chlorine AswillbeseenfromFigure7to9theextractor'- comprises'two parallel shafts 2! each of which can-is a ,number of star-shaped members II. The two shafts are rotated through gearing 80 in opposite directions so that the arms of the stars draw the material downward and flrst move towards one another and then away from one another. The mounting for shafts 28 and the ing device is formed in two parts 33, 34 arranged. end to end along the length of its conveyor and the part at the outlet end 34 receives a supply of wash water through a pipe 38 which wash liquor is delivered by an outlet pipe I to a tank 31. The

washed and partly-treated fibers are delivered by the conveyor through an outlet conduit ll to a screw-press 39 where the remainder of the spent liquor is squeezed out of them and delivered to a tank 4| through a pipe 4|. The consolidated mass is then passed through a conduit and prevent leakage, and the sealing action is enhanced'by the fact that the material is descending". The "chlorine is' introduced into the zone by pipes 48 which extend from a header pipe II through the walls of the tower and'stop flush with the inside face, and also by means of a set of pipes il which extend downwardly from a header pipe. From practical considerations the width between the side walls of the tower cannot be made much less than I! inches and since chlorine cannot readily penetrate the librous material to that extent, the additional vertical delivery pipes are provided. -'Ihus, a comparativ'ely small penetration is required without the necessity of applying substantial pressure to the chlorine. Chlorine with the required degree of moisture may-be prepared in an electrolytic plant 53 from which it passes through a delivery conduit 54 to a blower l5 driven by a motor 56.

The inlet or suction side of the blower communicates with the atmosphere through a valve 51 and alrpipe ll. 13y adjusting the valve 5! a desired vquantity of air may be mixed with the chlorine.

tion windows 9 and sockets for thermometers are provided.

The material is then delivered by the extractor into a tank I having rotating stirrers ll therein through which tank cold water is circulated. The material passes thence along a trough 62 to a rotating conical sieve 82, the axis of which is horizontal and the angle of inclination of the walls of which is such as to feed the material from the smaller end of the'sleve to the larger end. The diluted hydrochloric acid percolates out through the sieve walls into a'tank 64 and the fibrous material thus partially freed of acid is passed through screw-presses 65 where it is consolidated. The fibrous material is then passed through a mixing vat I containing a weak solution of caustic soda, e. g. a soda solution of 2% concentration or less. The material is treated in this vat for a fraction of an hour and this results in the removal of the chloro-lignine compounds and/or other non-cellulose soluble matter. Also, any remaining hydrochloric acid or chlorine combines with the caustic soda. Thereafter the fibers are passed through the usual washing and sorting apparatus where knots are removed.

As already indicated the towers both for the alkali and chlorine treatments are provided with thermometers so that the predetermined temperatures of the reactions may be maintained, for example, by controlling the rate of extraction of the material from the bottom of the towers. Furthermore, means are provided for periodically testing the air and moisture content of the chlorine mixture.

The starting material may be considered to contain roughly 50% cellulose constituent and 50% non-cellulose constituent. Each of the first two treatments, 1. e. the first alkali treatment and the chlorine treatment, result each in the removal of about 30% non-cellulose constituent,

' whereas the final alkali. treatment results in the removal of 40% of the non-cellulose constituent. The attenuated nature of the treatment in a number of steps and the comparatively slow velocity of the reaction and the comparatively low temperatures under which the reactions are carried out result in a high yield of fibrous cellulose of good quality and suitable for the manufacture of a high grade of paper owing to its strength, softness and pliability.

The stalks of plants, such as are mentioned at the commencement of the specification, contain about 8% ligninby weight of the material and about 42% of waxes, resins, pectic, mucic and albuminous matter, etc. The amount of alkali required for reaction with these latter substances is about half their weight. The chlorine gas reacts with all the lignin and with certain other non-cellulosic materials. It is important that the first alkali treatment should remove only about 30% of the non-cellulosic encrustants, since their presence in the material duringthe chlorination treatment insures the formation of chloro-lignins which are readily removed by the final alkali treatment. Since only 30% of the encrustants are to be removed by the first alkali treatment, i. e. an amount equal to 15% by weight of the material, and since the encrustants require about half their weight in alkali for the reaction, the weight of alkali required is about 7 by weight of the raw material or roughly the weight of the raw material.

There remains in the material after the chlorination treatment chloro-lignin and certain other chlor-organic compounds, together with some remaining encrustants. The chloro-compounds, however, require very little alkali for their dissolution and the total amount of alkali required in the last step is less than half that of the first alkali treatment.

It will be appreciated that many modifications may be made to details of the above process and apparatus without departing from the scope of this invention.

I claim:

1. An apparatus for extraction of cellulosic fibers from vegetable material comprising a mixing chamber having a bottom wall sloping in the direction of the length of the chamber, means for introducing the vegetable material into said chamber, a conveyor in said chamber arranged to traverse the material from the deep end to an outlet at the shallow end, means for introducing an alkali solution at a controlled rate to said chamber, means for directing the mixture from said outlet to the top of a vertical reaction tower open at the top, means for introducing steam into the upper part of the tower, means for extracting at a controlled rate the treated material from the bottom of the tower, means for removing the liquor from the treated material, a second vertical reaction tower open at the top, means for introducing the treated material into the top of the second tower, means for introducing at a controlled rate chlorine diluted with air into the upper part of the second tower, means for extracting the chlorinated material at a controlled rate from the bottom of said tower and for introducing it into a cold water bath, a vessel containing a weak alkali solution, and means for transferring material from the water plant to said vessel.

2. An apparatus for the extraction of cel-,

vegetable material to the central zone of said chamber, a conveyor in said chamber arranged to traverse material from the centre outwards to an outlet opening at each end of the chamber, means for introducing an alkali solution at a controlled rate to said chamber and means for directing the mixture from each outlet to a separate vertical reaction tower open at the top, means for introducing steam into the upper part of each tower, means for extracting at a controlled rate the treated material from the bottom of each tower, means for removing the liquor from the treated material, another vertical reaction tower open at the top, means for introducing the material to the top of the later tower, means for introducing at a controlled ,rate chlorine diluted with air into the upper part of said latter tower, means for extracting the chlorinated material at a controlled rate from the bottom of said tower and for introducing it into a cold water bath, a vessel containing a weak alkali solution, and means for transferring material from the water plant to said vessel.

3. An apparatus for the extraction of cellulosic fibers from vegetable material, comprising a vertical reaction tower open' at the top, means for introducing into the top of the tower the vegetable material mixed with alkali solu-" tion; means for introducing steam into the upper part of the tower, means for extracting at a controlled rate thetreated material from the bottom of the tower, means for removing the liquor from the treated material, a second vertical reaction tower open at the top, means for introducing the treated material into the top of the second tower, means for introducing at a controlled rate chlorine diluted with air into the upper part of the second tower, means for extracting the chlorinated material at a controlled

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