Method for treating a bulk material with a fluid

PCT No. PCT/SE78/00092 Sec. 371 Date Aug. 10, 1979 Sec. 102(e) Date Aug. 10, 1979 PCT Filed Dec. 11, 1978 PCT Pub. No. WO79/00375 PCT Pub. Date June 28, 1979 A bulk material is treated in a drum rotating in a bulk of the bulk material to be treated. The drum (16, 68) is provided with feeding-in openings (28, 70) in the cylindrical face of the drum. The bulk material tumbles around in the drum and is conveyed towards a discharge part in one end of the drum by means of a worm conveyor in the drum rotating in opposite direction to the drum. A treatment fluid is introduced into the drum through apertures (11a, 85) in the shaft of the worm conveyor. After the fluid has treated the bulk material in the drum it is led away through the same openings (28, 70) as those through which the bulk material is continuously being fed into the drum. Further the fluid advances up into the bulk of bulk material which therethrough also is treated before the material is fed into the drum. The method and the apparatus is particularly intended for treating pulp wood chips, e.g. for presteaming chips and for washing chips. In the former case one or more drums are provided horizontally in a container for the chip material, closely above the bottom of the container. In the latter case the drum is provided slopingly for conveying the chip material up through the container at the same time as the chip material is being washed.

FIELD OF THE INVENTION 
The present invention relates to a method of treating a bulk material with 
a gaseous, vaporous, or liquid fluid. For example the invention relates to 
a method of presteaming or other treatments of chopped wood chips for 
cellulose production by means of a fluid in the form of water steam. The 
invention also relates to an apparatus for carrying out the method. 
Another example of how the invention may be applied is the treatment of 
chopped wood pulp chips in order to thaw snow and ice which frequently 
exist in northern countries in bulks of chips which are stacked outdoors 
and which often cause problems in the initial part of the chip treatment 
prior to digesting. Another example of the applicability of the invention 
is for drying grain or other particulate materials wherein the treatment 
fluid normally is hot air. Another area where the principles of the 
invention may be applied is for effecting chemical reactions between a 
fluid in the form of a reactive gas, vapour or liquid, and for example a 
mineral concentrate. A further example of the applicability of the 
invention is for washing solid particles or objects, wherein the fluid may 
be a liquid washing or solution agent. This application of the invention 
may be used i.a. for washing wood chips with water in order to remove 
gravel, sand and similar heavy contaminations. 
BACKGROUND ART 
The Swedish Pat. No. 221 188 discloses a method and an apparatus for 
cleaning chopped cellulose chip material from accompanying foreign 
particles. The apparatus comprises a dewatering device equipped with a 
worm conveyor which suitably is inclined and surrounded by a perforated 
wall. During the course of the chip being fed upwards in the worm conveyor 
finer impurities such as sand particles are separated. The separated 
particles pass through the perforated wall together with the water and are 
fed through a conduit to a sand trap. The perforations of the partition 
wall are adapted to the size of the impurities which shall be removed, 
which means that the size of the perforations is chosen such that the 
chips essentially cannot pass therethrough but substantially proceed 
upwards and are delivered to an outlet. Due to the fact that the chip 
material is fed in at one end and discharged at the other end without 
being able to pass through the perforated wall the bulk of chip material 
in the helicoidal passage-way through the worm conveyor will be 
comparatively compact. Nor does the worm to any significant extent tumble 
around the bulk of chips in the conveyor, and therefore the washing of the 
chips during the transportation of same through the conveyor will not be 
highly efficient. 
The Swedish Pat. No. 171 489 discloses an apparatus for drying malt or 
other lump material. The apparatus comprises a rotatable cylindric drum 
through which the material to be dried is brought to pass from one gable 
to the other. The rotating drum is surrounded by a fixed drum so that a 
sectioned annular space is formed between the drums. Air for drying the 
material in the inner drum is fed in and led away through the 
semi-circular channels in the annular space. Further there is provided a 
central worm in the inner drum for conveying the material. The apparatus 
has i.a. the limitation that the outer drum excludes the possibility of 
treating material also outside the rotating drum simultaneous with the 
treatment of material inside the drum. The apparatus also is based on the 
principle that the apertures in the perforated drum are so small that only 
the treatment fluid, in this case air, can pass through the apertures but 
not the material to be treated. The latter therefore cannot pass in or out 
through the cylindrical wall of the drum during the treatment which 
renders any homogenous feeding-in of new material along the perforated 
length of the drum impossible at the same time as finished material is 
discharged through the end of the drum. 
In certain respects similar but in still higher degree closed systems are 
shown in the Norwegian Pat. No. 27 159 and the Danish Pat. No. 15 876. 
Further there is disclosed in the Swedish Pat. No. 398 633 an apparatus for 
discharging vessels. The apparatus comprises a vertical fixed 
non-perforated drum with a central worm conveyor. The shaft of the worm 
conveyor is perforated so that compressed air or other fluid can be 
injected through the shaft into the helicoidal passage way of the conveyor 
which facilitates the transportation through the drum. But due to the fact 
that the drum is fixed it is nor by means of this apparatus as in the 
apparatus according to the Swedish Pat. No. 221 188 achieved any tumbling 
action, and as the apparatus moreover is totally encased, i.e. 
non-perforated, there is nor achieved any interaction with or affect upon 
the environment of the drum. 
DESCRIPTION OF THE INVENTION 
The above mentioned drawbacks and limitations of previous methods and 
apparatuses may be eliminated through the invention therein that the bulk 
material is treated in a drum surrounded by a bulk of the material to be 
treated, that the bulk material is fed in into the drum through openings 
in the cylindrical face of the drum, that said fluid is introduced into 
the helicoidal space between a worm conveyor for said bulk material inside 
the drum and the drum encasing the worm conveyor, said worm conveyor being 
rotated in a direction opposite to that of the drum making the treatment 
of the bulk material in the drum more efficient due to the obtained loose 
distribution of the bulk material in the drum and due to the fact that the 
bulk material tumbles around in the drums, and that at least a portion of 
the fluid is caused to leave the drum through the same openings in the 
cylindrical face of the drum as those through which the bulk material is 
being fed in. 
When the invention is utilized for presteaming pulp wood chips the worm 
conveyor with the surrounding hole-provided drum is mounted in a chip bin, 
suitably closely above the bottom of the chip bin in order to discharge 
the chip material from the bin in the lower portion of the bin. After the 
steam has been contacted with the bulk of chips which presently exists in 
the drum, the steam proceeds via the openings in the drum up into the bulk 
of chips in the bin so that also this bulk of chips successively is 
presteamed which is made possible through the fact that the drum is 
located in and is surrounded by the chip material in the chip bin. The 
chip material in other words will meet the steam as the steam successively 
is advancing downwards in the bin wherethrough the steam is very 
efficiently utilized. The good presteaming effect also is stimulated by 
the fact that the chip material in the bin is kept moving by the rotating 
hole-provided drum in the bottom section of the bin. Suitably also a 
corresponding worm conveyor with surrounding drum is provided in the upper 
part of the bin for feeding in chip material into the bin. In that case 
however, the principles of the invention are utilized only partially. 
Also in the case when it is aimed at using the invention e.g. for washing 
wood chips the worm conveyor is provided with the surrounding drum in the 
bulk of bulk material, suitably closely over the bottom of the vessel--the 
washing tub--which then is made sloping as the "tube-feeder". The washing 
water is suitably fed in counter-currentwise into the drum and therefrom 
into the washing tub, while the chip material is discharged up from the 
vessel through the drum. 
In order to introduce the treatment fluid in an efficient manner into the 
helicoidal passage of the worm it is suitable for that purpose to use the 
shaft of the worm conveyor which hence is perforated. The apertures in the 
shaft of the worm conveyor are suitably so small that pulp material to be 
treated essentially shall not be able to pass through while the number of 
perforations on the other hand is sufficient to obtain the desired flow of 
the fluid to be injected. This means that the apertures in the shaft of 
the worm conveyor have a size of a quite different order than the openings 
in the cylindrical face of the drum which openings shall be so large that 
the bulk material without difficulty may pass through. The principle thus 
is that the fluid is urged into the space between the shaft of the worm 
conveyor and the cylindrical face of the drum via the apertures in the 
shaft of the worm conveyor, that the fluid is caused to contact the bulk 
material in the drum, and that the fluid thereafter is caused to leave the 
drum through the openings in the cylindrical face of the drum, said fluid 
then meeting the pulp material which is continuously fed in through said 
openings. 
The advantages and principles of the invention will be apparent more in 
detail from the following description of two preferred embodiments.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to FIGS. 1 and 2 a container for chopped wood chips for cellulose 
production has been generally designated 1. The container 1 has two length 
sides 2 and two gables or short sides 3. The sides 2, 3 and roof 4 consist 
of sheets connected by vertical beams 5 and horizontal beams 6. The front 
side 2 has been partly cut up in FIG. 1 to demonstrate the bulk of wood 
pulp chips 7 in the container. The bottom portion has the shape of tub or 
trough 8, which extends past the two short sides 5 of the container. The 
extending portions have been designated 8' and 8". In a longitudinal 
opening in the roof sheet 4 there is provided a vaulted top structure 9. 
In the trough 8, just over the bottom, there are horizontally mounted two 
parallel worm conveyors 10. Each of these worm conveyors consists of a 
shaft 11 and a screw blade 12 attached thereto. The shafts are mounted in 
one end in bearings 13 and are driven by a joint hydraulic motor 15 via a 
chain gearing 14 which is not disclosed in detail in the drawings. 
Each worm conveyor 10 is surrounded by a concentric drum 16 extending along 
the whole length of the worm conveyor and projecting past its ends. That 
end of the drum 16 which is turned to the shaft bearing 13 is mounted on 
the shaft 11 by a bearing 17. The opposite end of the drum 16 is mounted 
on the shaft 11 by a support bearing 18, the supports being designed like 
propeller blades attached to the drum 16. The propeller blades of the 
support bearing 18 are by welding joined to a shaft portion 21 having the 
form of a sleeve mounted in a bearing 19 in a partition wall 20 and in a 
bearing 22 in an end wall 23. Between the walls 20 and 23 the sleeve 21 is 
provided with four openings distributed around the circumference of the 
sleeve. The chamber between the walls 20 and 23 has been designated 25. 
The sleeve 21 and hence the support bearing 18 and the drum 16 are 
provided to be rotated in the opposite direction to the shaft 11 by means 
of a hydraulic motor 26 via a chain gear 27. Both the drums 16 are 
analogously designed, i.e. provided with support bearings 18, sleeves 21 
etc and are driven by the joint hydraulic motor 26 via the chain gear 27. 
In each drum there are made a number of openings in the form of oval holes 
28 which are distributed over the whole length of the cylindrical face of 
drum between the support bearing 18 and a line parallel with the further 
(referring to the support bearing 18) short side 3 of the container 1, or 
possibly a little bit further. The holes 28 are also distributed around 
the periphery of the drum 16 so that in each section of the drums there is 
at least one hole 28. Suitably the holes 28 are distributed helically 
around the drums. Further the holes 28 are so big that the bulk material 
to be treated, i.e. the chip material 7, readily may pass through the 
holes. The size of the holes 28 in the cylindrical face of the drum 16 
thus is of a quite different order than the small apertures 11a in the 
shaft 11. 
In the further end of the extension 8' of the trough 8 each drum 16 is 
provided with six larger substantially rectangular openings 29 above a 
chip discharge conduit 30. Further, according to the invention, a conduit 
31 for feeding steam is connected to the chamber 25 in the extension 8" in 
the left hand part of trough, and a conduit 32 for drawing off of surplus 
steam is connected to the extension 8' in the right hand part of the 
trough. 
In the top structure 9 there is provided one single worm conveyor 35 having 
a shaft 36 and a screw blade 37 attached thereto. In the manner as has 
been described with reference to the equipment in the trough 8, the worm 
conveyor 35 in the top structure 9 is surrounded by a drum 38 having holes 
along its whole length between two partition walls 40 and 41. The former 
front partition wall 40 is provided in that end of the drum 38 which is 
turned to that end where the chips are fed in, while the latter, the rear 
partition wall 41 is provided at a distance from the further gable 42 of 
the top structure 9. Between the front partition wall 40 and the drum 9 
there is an annular gap through which gases can pass, while the rear 
partition wall 41 is tightly engaged to the surface of the drum 38. 
In the chip feeding-in end the top structure 9 has an extension 9' provided 
with a connection 43 for feeding chips to a chamber 52 defined by said 
extension. In the discharge end, in a discharge chamber 51 between the 
partition wall 41 and the gable 42, the drum 38 is provided with a number 
of larger chip discharge openings 44. The shaft 36 is mounted in end 
bearings 45 and 46, and is driven by an hydraulic motor 47. The drum 38 is 
mounted in an end bearing 48 and in a support bearing said type which has 
been previously described and which is provided with supports in the form 
of propeller blades. The drum 38 is driven in a direction opposite that of 
the worm conveyor 35 by means of an hydraulic motor 50. A connection for 
supplying steam into the chamber 51 in the chip charging end has been 
designated 53. 
The described apparatus operates in the following manner. Chip material is 
fed into the entry chamber 52 through the connection 43 from a stack which 
as a rule is located in the open. The motor 47 rotates the worm conveyor 
35 in such a direction that the chip material is fed through the support 
bearing 49 into the drum 38 and progressively towards the discharge 
openings 44. Through the discharge openings 44 the chip material falls 
down into the container 1. Part of it also falls down into container 1 
through the openings 39 in the cylindrical face of the drum 38 which is 
facilitated by the fact that the drum at the same time is rotated in the 
opposite direction to that of the worm conveyor 35. 
Steam is supplied to the chip discharge chamber 51 through the connection 
53. From the chamber 51 steam is pressed--sucked--in through the chip 
discharge openings 44 and progressively into the drum 38. Part of the 
steam goes out through the openings 39 and into the space between the drum 
and the casing which forms the roof and wall of the top structure 9 and 
therefrom through the gap between the partition wall 40 and the drum 38 
into the chip entry chamber 52. The main portion of the steam is, however, 
pressed--sucked--helically forwards between the inside of the drum 38 and 
the screw blade 37 and hence meets the chip material which is continuously 
fed into the drum. Part of the steam is condensed upon the chips and/or 
attributes in melting snow and ice which in winter time as a rule 
accompany the pulp wood chip material which is being fed in. Surplus steam 
pass through the support bearing 49 into the chip entry chamber 52 
wherefrom the steam is sucked out through conduit 54. 
The equipment in the bottom portion of the apparatus operates in the 
following manner. The bulk 7 of chip material is successively fed through 
the openings 28 in the cylindrical faces of the drums 16 into the two 
rotating drums 16 in which the chip material forms a loose body of chip 
material tumbling around in the drums at the same time as the chip 
material is forced towards the discharge openings by means of the worm 
conveyor 10. The drums 16 therefore can be said to be digging around in 
the bulk 7 of chip material which homogeneously is fed into the drums over 
substantially the entire bottom area of the container 1. At the same time 
the rotating drums 16 give rise to a certain movement in the entire bulk 
7. Steam is fed into the chamber 25 through the steam connection 31. From 
the chamber 25 steam is pressed--sucked--into each sleeve 21 through the 
openings 24 and from the sleeves 21 into the tubular shaft 11 and 
therefrom into the respective drum 16 through the apertures 11a. In the 
drums 16 the steam meets the loose body of chip material which is tumbling 
around and which then is efficiently presteamed by the steam. The 
efficient stirring and the loose body of chip material is then of 
essential importance for a good presteaming result. Surplus steam is led 
away through conduit 32 while the main part is utilized for presteaming 
wood chip material. This is performed in the first place in the drums 16 
where the steam is caused to contact the bulk of chip material which 
continuously is fed in through the openings 28 in the cylinrical faces of 
the drums but also in the container 1 through the fact that the main part 
of the steam successively will pass out through the openings 28 in the 
drums, where the steam will meet the chip material which is being fed in 
through the same openings, whereupon the steam will advance up through the 
bulk 7 of chip material. The presteaming action can be stimulated by 
suitably adapting the pressures in the conduits 31, 32 and 53, 54 to each 
other. As the chip material 7 is successively fed down in the container 1 
it will thus meet warmer and more " virgin" steam wherethrough the 
presteaming result is made more efficient and the steam will be utilized 
in a more optimal way. In order further to improve the efficiency of the 
treatment, more particularly to make the stirring of the bulk of chip 
material in the container and the "digging function" of the drum more 
efficient the drums 16 may be movable sideways and/or in the vertical 
direction in the container 1. 
Referring now to FIG. 3 a vessel or tub for washing of wood chips is 
generally designated 60. The bulk of wood chips intended to be washed is 
designated 61. The washing vessel 60 is filled with water up to a level 62 
which is determined by a spillway 84. The bottom 63 of the vessel is 
dished and is inclined upwards. Further the bottom 63 is perforated by 
holes 64 for the transfer of small stones, sand and other heavy pollutants 
to a bottom pocket 65. From the bottom pocket the heavy pollutants can be 
removed through a conduit 66. The perforated floor plate or strainer 63 
can be cleansed by back-washing with water through conduit 66. 
A cylindrical chip conveying tube 67 extends slopingly up from the vessel 
60. In the tube 67, just above the perforated bottom 63, there is provided 
a drum 68 with a worm conveyor 69. The drum 68 is provided with passage 
openings in the form of oval holes 70 in the region of the vessel 60 but 
preferably not in the region of the tube 67. The drum 68 is provided to be 
rotated by a motor 71 via a sleeve shaped shaft portion 72, while the worm 
conveyor 69 is provided to be rotated in the opposite direction by a motor 
73. Suitably the drum 68 is provided with external flanges, tappets, or 
other projecting members which may move chips in the bulk of chips 61 
forward at the rotation of the drum. Due to the rotation of the drum 68 
and the worm conveyor 69 chips are fed into the drum through the holes 70 
and are transported up from the vessel 60 through the tube 67 and out from 
the tube through discharge openings 74 in the upper end of the drum 68. A 
discharge conduit 75 for washed chips is provided below said discharge 
openings 74. More particularly said openings 74 are provided between a 
support bearing 76 of the type above described and an end bearing 77. 
The sleeve shaped shaft portion 72 extends through the end bearing 77 of 
the drum and is fastened by welding to the support bearing 76. Further the 
sleeve 72 extends through an intake chamber 78 for fresh washing water and 
through a partition wall 79. A connection conduit for fresh washing water 
to chamber 78 has been designated 80. In the region of the intake chamber 
78 the sleeve 72 is provided with a number of intake openings 81 for fresh 
washing water whch is fed into chamber 78 through conduit 80. From chamber 
78 the washing water is brought into the sleeve 72 through the openings 
81, and from the sleeve 72 it is thereafter brought into the drum 68 via a 
narrow space 82 between the sleeve 72 and the shaft 83 of the worm 
conveyor. Fresh washing water consequenty continuously meets the chips 
which continuously are transported upwards in the drum 68 from the washing 
vessel 60. Used washing water is drained off through the spillway 84 in 
the upper part of the tube 67, whereafter the water can be recirculated 
and reintaken into the chamber 78 through conduit 80, possibly after 
straining or other purification. The majority of heavy particles existing 
in the bulk of chips are removed already in the vessel 60 when the chips 
are agitated by the drum 68 and sink down to the bottom 63 and are 
collected in the pocket 65. Such heavy particles which, however, are 
introduced into the drum 68 are forced downwards through the drum by means 
of the washing water which is taken in in the upper part of the drum in 
the manner above described and are discharged from the drum together with 
the washing water through the openings 70 in the lower part of the drum. A 
very efficient washing takes place in the drum due to the fact that the 
quantity of chips in the drum is not compact but loose and is agitated, 
and to the fact that fresh washing water is continuously supplied 
countercurrentwise.