US2184314A - Desiccating method - Google Patents

Description

DEC- 26, D D PEEBLES v I DESICCATING METHOD Filed April 12, '1953 2 Sheets-Sheet 1 F I I5 l INVENTOR. 00 via 0 peeb/-s ATTORNEYS.

Patented Dec. 26, 1939 UNITED STATES "mane nts, to 'Golden .State' Company,

Ltd. a corporation of Delaware Application April 12, 1933, Serial No. 5,709

- Claims.

This invention relates generally to methods and apparatus for the manufacture of molasses or like material in divided solid condition. By molasses I have particular reference to the crude material of this name which is obtained as a byproduct in the manufacture of sugar.

It is an object of the invention to provide a method and apparatus of the above character which will make possible the manufacture of the desired divided solid and desiccated product at a relatively low cost, from both the standpoint of efilcien'cy of operation and the cost of installing the necessary equipment;

Further objects of the invention will appear from the following description in which the preferred embodiment of the invention has been set forth in detail in conjunction with the accompanying drawings:

Referring to the drawings:

Figure 1 is a diagrammatic view, illustrating apparatus incorporating the present invention, and which can be utilized in carrying out my method.

Figure 2 is a side elevational view, in cross section, illustrating a desiccator of the type which can'beutilized in my method.

Figure 3 is a cross-sectional view taken along the line 3-3 of Figure 2. v g

My method can be best explained after a description of the apparatus illustrated in the drawings. Referring first to Fig. l, the apparatus shown includes a desiccator IQ of the spray type. While a latitude is permissible with respect to the construction of this desiccator, the particular type of desiccator illustrated in detail in Fig. 2, and which will be presently explained, is desirable. With respect to Fig. 1, it will sufiice to point out that the desiccator I 0 includes a treatment chamber l l into which molasses can be introduced by way of pipe l2. In order to maintain a region of desiccation within chamber I I, I have indicated introduction of hot air into chamber H by way of two sets of conduits identified by letters a and b. vIn order that this air may be of the proper elevated temperature, I have indicated a heater l3 through which the air flowis passed before being distributed to the pipes a and b. Additional lines identified by letters 0, d and e have indicated for introducing relatively cool air into the desiccating chamber, as will. be presently explained. Removal of the desiccated material, together with aportion of the gas within chamber l I, has been indicated by way of conduit ll. Lines It also indicate introduction of additional cool air.

The molasses to bedesiccated, such as molasses obtained as a by-product-in the manufacture of cane sugar, can be stored in a suitable container as indicated at I1. In order to maintain the stored molasses at a sufficient temperature to 20 to heater 22.

i- PATENT oFFica insure proper fluidity, I have indicated a recirculation path formed by pump l8 and heater l9.

In order to cause a continued flow of molasses from vessel H to the pipe I2, I have shown a pump 20, the outflow side of which is connected to pipe l2, in series with heater 22. Heater 22 can, be supplied with steam or any other suitable heating medium which can be properly regulated to impart the desired amount of heat to a the molasses.

' The capacity of pump 20 sure conditions in pipe l2. Thus, a by-pass 2| has been shown about pump 2'), controlled, by throtpressure beyond a desired value in pipe I2 causes pressure'responsive device 2lb to efiect a compensating adjustment of throttling means 2m, to 5 decrease the rate of fiow of material from pump It is desirable to handle the: discharge from conduit ii in such a manner as to permit removal, thorough cooling, and sacking of the desic- I cated product. For this purpose conduit I4 has been shown connected to the inflow sideof a is preferably con-- trolled to maintain substantially constant presblower 23. The discharge side of blower 23 is shown connected to a suitable pneumatic separator 24, preferably of the cyclone type. This separator is provided with the usual air exhaust pipe 26 and a lower conduit 21 for the discharge of separated material. The discharge of desiccated material-from conduit 21 is caught up by an air current in conduit 28, induced by blower 29. Untreated air from the atmosphere may be induced to flowthru conduit 28, if the moisture content is relatively low. However. if the moistions, then the air should first be conditioned to reduce its relative humidity. Thistreatment gives the powder time to cool uniformly throughout each particle, and tends to prevent subsequent caking. The outflow side of blower 29 ture content of the atmosphere is relatively high,

which may occur under certain climatic -condi-.

has been shown connected to a second pneumatic separator 3| of the cyclone type. Air exhausted from the separator 3|, indicated by way of line 22, can be introduced back into the separator 24.

The separated desiccated material removed from the separator 3|, by way 'ofconduit 33, can be delivered directly into sacks.

Before explaining the mode of operation of the apparatus illustrated in Fig. 1, I shall describe the particular form of desiccator illustrated in-detailin Fig. 2. In this view the conduits corresponding to lines designated by letters etc e inclusive in Fig. 1, have been designated by numerals Ia to Sc inclusive. It will be noted that conduits 2b and 5e inclusive are arranged to discharge tangentially into the desiccating' chamber H, at difl'erent levels. Conduits la discharge into a supplemental chamber 36, which communicates thru the upper wall 31 of the main chamber II, at a point concentric with the verbe substantially cylindrical in horizontal cross section, and for good results should be of substantial height with respect to its diameter. Pipe l2 for introducing the molassw is provided with a nozzle 39 at its lower end, which affords what can be termed a spray orifice. The lower chamber wall 4| can beconically shaped as illustrated, with its lower central portion communieating with the discharge conduit H. In that region immediately above the lower wall 4|, a transverse baiiie 42 is provided, to serve both as a cool air inlet, and in order to minimize swirling movement of air within the lower portion of the chamber before this air together with the desiccated material is removed by way of conduit l4. Referring to Fig. 3 it will be noted that baflle 42 is in the form of a trough, with its lower wall in communication with conduits lSa, for introducing relatively cool air.

The number of conduits provided for the introduction of air into the main desiccating chamber II, at various levels, may of course vary. For example in practice I have used two conduits 217, two conduits 9c, four conduits ld, and four conduits ie. I have found it'desirable' to provide adjustable shutters 43 at the point of discharge of these conduits into the main desiccating chamber, to afford better control of the air introduced.

With respect to the mode of operation of the desiccator, apart from the remainder of the apparatus, it may be explained that in-practice since the conduits la, and also conduits 2b in the event they are employed, are caused to introduce hot gas, a region of desiccation will be established in the neighborhood surrounding the nozzle 39, and in the upper portion of the desiccating chamber H. In a typical case the temperature of the hot gas at the points of injection may be about 700 F. That portion of the hot gas introduced'by way of conduit 38, will be discharged downwardly and about nozzle 39, while any additional hot gas which may be introduced by way of conduit 21), causes swirling movement within the upper portion or the desiccating chamber. The parti: cles of molasses discharged by nozzle 39 are received within this region of desiccation, and the particles are caught up and carried in suspen-' slon by the gas currents. While it is desirable to have the particles of molasses or likematerial spread outwardly somewhat and move downwardly, the air flow into the treatment chamber should not impart swirling movement of such intensity as to cause the particles to be immediately thrown outwardly'to the side walls, nor should the air flow impart a downward velocity component of such intensity as to cause the particles to be discharged downwardly thru thechamber without proper treatment. The hot gas within the desiccating chamber progresses downwardly, together with the particles being desiccated while in the liquid phase, the temperature being reduced somewhat by evaporation of moisture from the molasses. At-or nearly level of conduits 3c, the temperature is further reduced by dilution with'the relatively cool gas. Further dilution and cooling occurs as the gas progresses to the lower levels .of conduits 4dand 5e, although the particles of desiccated material are maintained in suspension throughout their progression down thru the desiccating chamber, and are prevented from adhering to the side walls of the chamber by virtue of the sweeping action occasioned by the tangential introduction of gas thru the conduits to, tical chamber axis. The main chamber II can 4d and 5e, and because their surfaces, having been cooled, are hardened. In this connection it should be noted that the gas introduced by way of conduits 30, id and 5e, maintains the side walls of the chamber relatively cool, thus preventing burning even in the event these walls are contacted with molasses particles. As a result of the dilution and cooling effected by introducing cool air thru the conduits 3c, 4d and 5e, and by the progression of the desiccated particles downwardly thru the successive levels of these conduits, the desiccated particles are converted to the solid phase, assuming of course that the material being desiccated is molasses or like material. In other words with a desiccator such as illustrated in Fig. 2, assuming that molasses introduced by way of'nozzle 39 is caused to be atomized, the atomized particles are first desiccated while the particles are retained in the liquid phase, and then these desiccated particles are immediately caused to progress into a region where they are caused to be converted to the solid phase, by contact with relatively cool gas. Therefore the particles removed pneumatically through conduit l4 from the lower endof the chamber, are in the solid phase.

with respect to converting the desiccated particles of molasses to the solid phase, it should be pointed out that the humidity'of the gas within the treatment chamber ll, particularly in that region in which the particles are converted to the solid phase, should be sufliciently low as to avoid causing the solid particles to become sticky and adhere together. Thus if climatic conditions are such thatthe atmosphere is relatively humid, the cool atmosphere introduced by way of conduits 3c, 4d and 5e should be conditioned, to reduce its moisture content. It may be explained that the transition point between the solid and liquid phases of molasses occurs in the neighborhood of 158 F., at which temperature solid molasses begins to soften.

Referring again to Fig. 1, the objects to be gained by continuously heating the flow of molasses to the spray orifice associated with pipe I2 will now be explained. Molasses, because of its inherent viscosity, is a material which is diillcult to atomize. However, I have found that if suflicient heat is imparted to molasses flowing to an ordinary spray orifice, while the molasses is maintained under pressure, atomization will occur together with a' simultaneous liberation of water vapor at the point of discharge. Thus, with the apparatus of Fig. 1, a considerable pressure above atmospheric is maintained upon the discharge side of pump 20, and a predetermined amount of heat is transferred to the flow of molasses-by virtue of heater 22. The molasses leaving heater 22 and being'delivered to the desiccator should be at such an elevated temperature that the corresponding internal pressure of the molasses is substantially greater than atmospheric, but substantially less than the actual pressure maintained by pump 29. In actual practice I have secured good results by maintaining a pressure of about 150 lbs. gauge by means of pump 20, and by heating the molasses to a temperature 01 about 275 F. Under such conditions the molasses discharged from the spray orifice into the desiccator is effectively atomized. It may also be 2,184,314 explained in this. connection that heating oi." the molasses under certain conditions will cause an exothermic reaction, and thereby cause the building up of an extremely high internal pressure.

This is attributed to the fact that molasses is an organic material subject to spontaneous deterioration. l, dustrial and Engineering Chemistry, vol. 21, No. 6, pages 600 to 606.) Such an exothermic reaction is influenced chiefly by twofactors, one being the length of time that the molasses is retained at an elevated temperature before dischargefrom .the spray nozzle, and the second being the temperature to which the molasses is heated. I can operate my apparatus to advantage with such an exothermic reaction, provided, however, that the factors just outlined are so controlled that uncontrollable unduly high pressures do not result. In order that any such exothermic reaction may not make control diilicult,

I so construct heater 22 that it will afford a relatively low capacity for the storage of heated material, and so that the flow thru the heater occurs continuously and at a relatively rapid rate. For example, with a pump pressure of about 150 lbs. I have secured good results by utilizing a flow rate of two gallons per minute, witha heater having a volumetric capacity of three gallons, and with a molasses temperature on the outflow side of the heater of about 275 F. The material utilized in that instance was Hawaiian blackstrapmolasses having a specific gravity of about 435 Baum and containing about 31.4% by weight of sugar in the form of sucrose and about 16.2% invert sugar.

with reference to the above example, a steam pressure of about 31 lbs. gauge, corresponds to a, temperature of 275 F. which of itself would not efiect proper atomization. However, a substan-' tial amount of internal pressure is developed by an exothermic reaction, to make possible effective atomization. In this connection the more efiective atomization is promoted not only by the.

flashing of a part of the water content into steam at the time of spraying, but also by the release 01' carbon dioxide and other gases or vapors, acidic in character, which are generated incident to the exothermic reaction. I

The product made by my method and apparatus is a somewhat gritty powder By controlling conditions under which the molasses is heated prior to effecting its atomization, the character of the resulting product can be varied from one in which the organic ingredients have undergone substantially nochange, to a product in which certain changes in the organic constituents have occurred and which is relatively black in color. In general, the color tends to become darker with an increase in the period of heat treatment before atomization, as, for example, by

decreasing the rate '0! flow to the spray orifice; byincreasing the storage capacity of the molasses heater; or by increasing the storage capacity-oi the pipe line connecting the-heater with the orifice. With other factors substantially constant, the color of the. final product becomes darker with an increase in. the temperature to Y which the molasses is heated before atomization.

The extent to whichthe product is blackened is an index to the degree to which an exothermic reaction has taken place, and like thermic reaction is accompanied by degradation (See publication by C. A. Browne in In- I the exo vtion of sugar by rapidly the extent of the reaction. If-th'e product is to be used as an ingredient of stock feed, I prefer v not to cause any marked degree of blackening, so that the material will be palatable and of high nutritive value. However, a product inwhich a marked degree of carbonization has occurred, may be desirable for otherpurposes, particularly because the changes causing a darkening in color tend to minimize hygroscopicity.

It is evident from the above that my method and apparatus is characterized. by comparative simplicity and will make possible the manufacture of a marketable desiccated molasses at low cost.

I claim: a v

1. In a method of desiccating molasses, the steps of heating the molasses under'pressure to cause development of. an internal pressure substantially greater than the corresponding vapor pressure of water'at the temperature to which the molasses is heated, expanding the molasses in a gaseous medium at a temperature above the solidification point of the molasses, thereby effecting removal of moisture, and then cooling the molasses particles while suspended in a gaseous medium thereby converting the same to the solid phase.

'2. In a method of, effecting desiccation of molasses, causing acontinual flow of the molasses which degradation of its sugar content commences, and. causing the; molasses discharged from said orifice to be atomized by release of water vapor and by release of gases generated incident to partial degradation of its sugar content.

1. In a process of preparing a dry powdered material from molasses, the steps of causing a continual fiow of the molasses under pressure to 50 3 a discharge orifice, heating the molasses during its flow to an elevated temperature to initiate degradation of its sugar content, causing the molasses discharging from said orifice to be atomized with simultaneous release of water vapor and gases incident to partial degradation of sugar,

causing the atomized particles to contact a heated drying gas, and then cooling the particles to convert the same to the solid phase,

5. In a process of preparing a dry powdered on material from molasses, the-steps of causing a continual flow of the molasses under pressure to a discharge orifice, heating the molasses during its flow to an elevated temperature to initiate degradation otits' sugar content, causing the molasses discharging from said orifice to be atomized with simultaneous release of water vapor and gases incident to .partial degradationof sugar, causing the-atomized particles to contact a heated drying gas, and then arresting further degradacooling the particles.

DAVID D.

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