US1917467A - Drying of young grass, fodder, and the like - Google Patents

Description

y 1933- 0. SODERLUND 1,917,467

DRYING OF YOUNG GRASS. FODDER, AND Till LIKE Filed Oct. 27, 1930 2 Sheets-Sheet l F] I I l I bl b 5: Fly

3: L 1933. Q. soDERLmND WW DRYZNG OF YOUNG GRASS "-ODDEH, END THE LIKE FiEed 0 W. 27, 1930 2 he tsheet 2 Patented July 11, 1933 .OLOZE SGDER-LUND, .OF .CLAPHAM PARK, LONDON ENGLAN D, AssrGNoR, TO meme- CHEMICAL LABORATORIES, LIMITED, or Lennon, ENGLAND DRYING or roun enass-nonnnn, AND Ti-IE LIKE Application filed October 27, 19ao,serie1ne; 491,572, and in Great Britain November 1, 1929.

This invention relates to the drying by direct contact with hot gases of subdivided materials whichcan becarriedby a rapidly fiovving elastic gaseous fluid stream in a conduit.

To obtain high thermal efficiency when drying with hot gases it is important :to utilize gases of the highest obtainable temperature and by extraction of heatforthedrying process to cool these gases down to as lowa temperature as possible while employing sim- :ple apparatus of small dimensions so as :to minimize radiation losses.

Gases of the highest temperature ordinaidly-obtainable from furnacesor other combustion appliances when brought into-direct contact with material to be dried are very liable to cause injury by overheating particles which have already beendried and this is difficult to avoid' bccause the conditions vary from place to place throughout the mass of material which is suspended in the gases and homogeneous mingling 0f the material andthegases is diflicu'lt. Furthermore, when of part of the material.

I costly.

employing high temperature gases for the drying of materials which are combustible,

fire danger-will occur unless great care to" exclude any supporter of-combustion is exer- "cised orthegases are very :rapidlyand evenly coeled down to comparatively low temperatures. v

It is known that it is diflicultto satisfactorily dry young grass, fodder and similar materials. Various methedsfhave been suggested for drying these materials with hot gases but ithas always been found -to'be very difficult if not impossible to obtain uniform drying and toavoid destructive overheating These difficulties -'limit the suggested methods to materials which are not so sensitive as young grass to -destructionby overheating or long exposure to higher temperatures. The drying time employedis frequently in the neighbourhood of 15 to 30 minutes or even lon'ger and-'the'necese sary apparatus is often cumbersome and An object of *the present invention is to 'overcon1e difiiculties such as the foregoing and -to provide for the utilization of higher temperatures than .are now ordinarily emthe moving stream.

ployed for drying material suspended a h gaseous ,imedium. V 7

Another ob ect of the invention is to .providc a method of drying materialswvhich are divided material in an evenly distributed con- 0 dition .and in thin layersand predetermined quantityed-irectly into fluegases of high temperature while such gases are in sufiiciently rapid motionto carry forward with them'the PATENT cornice I by sensitive to destruction, such as young grass, 3155 injected material through a tortuous conduithaving sinuous Walls continually changing .t-hediroction of flow .to retain homogeneous mingling and having nopockets or the like in which the solid matter canbe deposited from I The invention further consists in proceeding in accordance with the preceding paragraph-by exposing young fresh-cut grass, fodder or like mat-erialsto the action of a-gaseous medium having a temperature of up to800 C. to 1000 0. for exceedinglyshorttime intervals which may be in the neighbourhood of one second or less. I

The invention further consists in drying such materials as last referred to by bringing them "in intimate and controllable contact with hot gases by suspending and carrying the materials in the hot gases in such a manner as to create continuous turbulence and- 7 subsequently separating the ;,gases from the material.

' 'The invention further consists 'in drying young grass, fodder andfother similar materials by feeding them in thin layers intoand blowing them with gases of high temperature at high speed through passages suitably shaped so that the relative position of the 7 material to be dried and the hot gasesxis continually beingchanged,

The invention further consists in employing for the above-described drying processes' rectangularor oblonggshaped passages which aredisposed in a tortuous path by male ing-their sides corrugated.

"to v j which is evenly distributed by the rollers When carrying the invention into effect in a one way, given as example only, I distribute fresh-cut grass in a thin layer and pass it by means of gasses of a temperature of say 800 C. from a furnace and travelling at an aver-. age speed of from 10 to 15 meters per second through a passage consisting of two thin metal plates, fixed in a frame, so as toform a tortuous passage for the gases and material. A fan is employed to carry the gases and material through the apparatus and from the apparatus to a cyclone or other separation device; a

The hot gases required for the operation of the invention can be obtained from any suitable source.

The invention may also be applied to the drying of peat, lignite or any other material which is suitable, the passage or conduit employedbeing of long and narrow cross sec tion with sinuous walls. The conduit is conveniently formed of two corrugated sheets placed near to one another; the closing end plates need not be sinuous. The conduit is preferably disposed vertically and provides a suitable length of path to effect the drying required. The lower end of the conduit is provided on one side with a feeding device which may comprise apair of rollers extending across the width of the conduit and delivering from between them in suitably predetermined quantity the subdivided material along the whole width of the conduit onto an inclined plate terminating at the inner surface of the conduit. Onthe opposite side and just below the. plate is a long narrow slit communicating with a combustion chamber,

e. g. a coke or powder fuel or gas furnace or other source of supply of a hot gaseous medium incapable of supporting combustion. The lower end of the conduit opens into a closed receptacle or trap into which any powder not carried upwards by the gaseous streamcan freely fall. 7 v

The outlet'end of the sinuous conduit may be coupled to a cyclone or other separating device and an eXhauster, which latter is capable of giving therequired velocity of flow of products of combustion through the sinuous conduit, while the cyclone separates the gases frointhe material.

In some cases the sinuous conduit may be turned'back down to the inlet level and then upwards again forming a suitable number of zigzag passages where it is not convenient to provide sufficient path for moisture abstraction in one single direction. The whole of the apparatus may be suitably insulated.

Alternatively, a fan may be arranged to deliver air for combustion to the furnace so as to maintain a pressure above that of the atmosphere throughout-the apparatus, the

. conduit forming a plenum system, avoiding air leaks.

In working, the grass 'moisture-laden w powder or other material to' be dried in predetermined quantity and in thin layers is delivered directly into the stream of hot gases at a temperature of about 800? C. to 1000 (1., flowing into the conduit and is carried therethrough depositing in a practically drycondition in the cyclone. a v

It is found that drying of lignite or peat powder can be practically accomplished without any risk of fire notwithstanding the very high temperatures used and that it takes place I very rapidly so that a large output for the size of apparatus as well as high'thermal efficiency can be obtained.

, In some cases a plurality of sinuous passages may be utilized'in parallel, care being taken to ensure uniform distribution of the flow through them.

The invention provides a simple method and small apparatus for utilizing gases of'- high temperatures and rapidly cooling the gases bythe abstraction'of heat to effect evaporation down to the neighbourhood of the saturation temperature of the gases.

In theapparatus shown in Figures 1 and' 2, a is a furnace from which gases at a temperature of from 800 C. to 1000 C. issue at the outlet a. and b is an elongated conduit of attenuated or long and narrow cross section having sinuous-walls b and aplurality of return bends b to create continuous turbulence and homogeneousmingling of the material and the gases, 0 is a feeding device comprising a pair of rollers whose length corresponds with the width of the conduit' and by which the material to be'dried in predetermined quantities is injected into the hot gases in an evenly distributed thin layer which passes; down the inclined plateo and is carried up by the gaseous stream. 0

An exhauster d imparts the required high velocity to the gases for carrying the materialthrough the conduit and discharges into the cyclone e from which the dried product isobtained ate and the spent gasesescape at e at a temperatureof say 100 G. to 150 C. As shown at FigureB a furnace or heater a is of more upright form and the outlet at is at the upper end. v I i v The feeding connection c entersthe bend in such a manner that the material at entry is moving in the same direction as the hot gas is travelling and the material is disposed as an even layer by being fed by the Chute m on. to a moving belt or n y carried by rollers n) and of the same widt as the conduit 6.

The conveyor deposits the even layer of grass, or other material to be dried within the hood 0 of the connection 0 at the lower end of which the layer is'met and carried forward evenly by the hot gas which at this region may preferably be given a higher velocity by suitably forming the conduit.

The presence of the layer of material prevents the entrance of any undesirable quantity of air at the hood '0 and if shortage of material at any region should allow more air to enter this air will tend to reduce the temperature locally at the region where the ma-v terial is deficient and will, therefore, prevent overheating thereof.

A device for feeding in the material in the same direction as the hot gas is travelling may be fitted at any substantially horizontally or downwardly directed region of the conduit, such region being introduced at any position as desirable for the purpose and the dimension of the conduit normal to the width being reduced as may be required to give the proper velocity to the hot gases to evenly carry forward the layer of material.

All the apparatus of the driers .is enclosed i in an insulating 7c, is and the spent gases may It is to be understood that the construe-- sinuous walls and semi-circular return'bends f extending without break from the region where said material is fed into said medium and means for moving said medium along said conduit to carry said-material without 1 deposit and subject it to reciprocating turbulence by contact With said walls.

In testimony whereof I have signed my name to this specification.

OLOF soDERLUND.

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