December, 1931
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Merging of Process Steps' Clarence W. Vogt VOGT PROCESS, LOUISVILLE,Ks.
Apparatus for rapidly heat-treating (chilling, freezstability and uniformity, and EFORE the recent uning, or heating) materials i n which the material is many others, perplexing as p l e a s a n t n e s s in the forced through a confined layer, which is subjected to well as interesting. s e c u r i t i e s markets, concurrent exposure to the effect of the cooling (or m a n y of t h e b e s t financial Application to Ice-Cream heating) medium; effective application t o and rem i n d s were occupied with Freezing moval from such exposure; and applications of the m e r g i n g corporations (fish apparatus to the primary freezing of ice cream and t o The t w o-step process, and coffee companies were the crystallizing of edible oils are described. which is being replaced by joined in one group, cleansing It is shown that with such products operations, the merged process, as far as powders and butter substiwhich have heretofore been carried out o n succeeding ice cream is concerned, was tutes in another, etc.), and batches, and/or progressively, have been merged or the so-called batch freezer, during that period less emcombined so that the operations are performed o n the which consisted of a cylinphasis was being placed, in material concurrently, with, i n some cases, unusually der of net v o l u m e t r i c dismany instances. on the imbeneficial results. placement of 10 to 30 gallons, mediate o b t e n s i o n of t h e the external surface of which benefits of a complementary nature (where any existed) in the contemplated or accomplished was subjected to a refrigerant bath, the interior of the cylinder merger than on the prospective combined earnings of the new being fitted with agitating and whipping mechanism. The legally related, but oftentimes otherwise unrelated and wholly operating cycle of the apparatus is briefly as follows: uncomplementary entities. Filling of the cylinder with the mix to be frozen. With the broad changes which have occurred in the securiFreezing of the mix by the application of a refrigerant to the ties markets, more attention, thought, and effort are being outside surface of the cylinder, at the same time stirring the given to the fundamental economics and to capturing what- contents during the freezing operation. This operation usually ever concomitant benefits were or may be brought into the requires from 3 to 10 minutes, depending on the temperature picture, after giving effect to the new combinations. Other of the refrigerant, the effectiveness of the stirring mechanism, and the size of the cylinder (the larger the net volumetric conthings being equal, the mergers which will prove to have been tents of the cylinder, the longer the time required). wise and beneficial are those which effect real and measurable Shutting off the refrigerant supply in order to incorporate the economic improvements through elimination of duplication desired amount of air or overrun. This also requires some 3 or overlapping of efforts, as well as improved more effective to 10 minutes. Discharging the batch, which flows from the freezer under developments in research, production, and marketing. atmospheric pressure by the force of gravity, assisted somewhat It is often more difficult to discover suitable mergers in by the so-called unloading blades carried by the agitating mechaprocessing steps, the merging or changing of which will be of nism. unquestionable benefit, but once in a while one such is disIn contrast, the apparatus carrying out, the merged-process covered. This article describes, in part, a merged process steps (shown in Figure 1)includes one or more tubes surrounded which has recently been introduced to industry. Boiled down to its absolute essentials, it consists of con- by a refrigerant, the interior of the tubes being fitted with novel current agitation and heat transfer effecting a change of state agitating and whipping members leaving a relatively thin of material being passed through a confined layer or space. layer of material under treatment. This is shown diagramI t s primary application is in the ice-cream industry, and its matically in Figure 2. The apparatus (Figure 2), of the introduction has resulted in leading owners and operators of equivalent hourly capacity of the former type apparatus, has a ice-cream plants over the country using it as the high pvint or material displacement equivalent to only 2 per cent of that key point in advertising the new product thus produced, such required to be present in the former type; this means, in other advertising already having mounted to several hundred words, that the material is treated by the apparatus carrying out the merged process in 2 per cent of the time required by the thousand dollars in the last twelve months. The products to which i t has been next successfully applied batch-type apparatus using the same temperature of refrigerare lard and lard substitutes. The application to a substan- ant. Were this the sole difference between the merged process tial number of other commodities is in the work-in-process and the multistep or batch process, it would be sufficient to cause the merger statisticians to have decided that the merger stage, while still others are awaiting their turn. was in the interest of economy. It is oftentimes the case, where the selection of units to be The material or mix is fed to the apparatus under sufficient merged has been most propitious and successful, that the effect of the merger in net results is not merely the algebraic sum of pressure to cause its advancement and discharge. As the material is obviously being changed rapidly from a liquid the net results of the units merged. Some outstanding cases towards a solid, this change of state should be quite complete have shown that the net results far exceed those forecast by in order to take full advantage of the process. In other words, superimposition of balance-sheet totals. This same phenome- the discharged material should be as near to that consistency non is true in connection with the merger herein described. As will be seen from the context, the net results obtained are a t which it is to be consumed as is practicable. I n order to not merely those which might be expected from simplified produce the desired swell or overrun, the air or other gas is procedure but go far beyond, and the measure of the net results also fed to the apparatus under a correspondingly high presthus brought about brings up intangible considerations, such sure. Because of the relative thinness of the layer the unias new standards of quality, the value of a product of increased formity of treatment of the layer throughout its thickness is much more pronounced than in the case of the large diameter * Received July 21, 1931. and many-times thicker layer employed in the batch e q u i p
B
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INUUSI‘ILIAL AiVU ENG1NEERING CHEMISTRY
ment, and it is thus possible to cuiriplete the entire incorporation of air at the same time and actually by t.he same mechanism, so that the product leaving this chamber and passing to the container is in a much more complete and uniform state than is possible with the atmospheric, batch, or steptype apparatus. I n food products, such as ice cream, which cannot be comfortably gulped down, but which reach the tongue of the consumer in small portions, the absence of any sharp water crystals is of first importance from a quality consideration.
Figure I-Merger-Process Unit In Operation in Ice-Crcarn Plant
The unit operates under full automa+ control, and t h e product i s discharged contlnuuurly.
Since the public is becoming niure and more conscious of the fact that quick-freeding produces sinall crystals, the product made by this merger process is thus not only produced more economically but in less than 2 per cent of blie time required by the former step or atmospheric process. Therefore, the merger, in addition to accomplishing an increase in economy, owing to being carried out in much faster tiine, also makes possible the processing of a product possessing smoother and more desirable qualities. I n addition to these points, even though a t first thought it might seem paradoxical, the merged process is carried out with a saving in refrigeration. The reason for this is apparent when it is explained that material which is being treated inn small layer in one-fiftieth of the time is subjected to a great deaf less useless beating and stirring; and, when it is recognized that beating and stirring set up friction and produce heat it is realized that the less urinecessary heat is added the less is the total amount of heat required to he removed, as the latter is the arithmetical sum of the heat present in the product, when admitted to the apparatus and removed therein, and the hent added by friction, such as beating, cutting, and stirring. Another pertinent fact is that a process which receives and discharges a product continuously makes possible the simplification of plant routine and plant equipment beyond that possible with intermitt,cntor step processes. Another test which should be applied to the desirability of the merged-process steps is whether or not there is available suitable control for the process. The question of control is 8.a important to the engineer evaluating a technical process BB it is to financial speeialists in considering corporate set-ups and
Yol. 23, No. 12
contro~of merged units. The allswer is tirat complete and satisfactory automatic controls are developed and applied to the merged process, whereas the step or batch process has not been supplied with such controls. Application to Edible Oils and Fats Lard and lard substitutes have had the benefit of continuous treatment, that is, continuous supply and continuous delivery equipment, for many years. Nowever, the product had been prepared by the step method. Material had been chilled in a very thin film which was applied to the outside of a large refrigerated roll, and, after being chilled, the material was passed through the step of whipping in of air in order to cause the desirable whitening, this additional whipping taking place in a trough or “picker box” equipped with whipping blades. I n these products it is not necessary to whip in as much air as is the case with ice cream, as only a small percentage-5 to 15 per cent-k needed to cause the necessary whiteness. Therefore, the test as to whether or not the merging of these steps would be advantageous hinged on whether or not whipping or heat treating could be accomplished in any other apparatus in a more economical, uniform, or satisfactory method. The spreading of the material in a very thin film permitted the chilling through the critical zone in about 4 seconds. Therefore, if the crystnls in the merged products were to be as minute, this chilling would have to be accomplished in the same time. It was found that the material could be spread in a somewhat thicker layer in the merged process because of the presence of concurrent agitation, which was not present, of course, on the roll. And yet, with the same temperature of refrigerant a8 was used in connection with the roll, this chilling took place in the merged type of apparatus in from 1.5 to 2 seconds, with the ndditional advantage that the gas or air required for whitening the product was incorporated simultaneously with the chilling and before the product had been crystallized. Obviously, i t is much easier to whip air in material before it has become hard. One of the principal drawbacks of the roll snd picker box type of apparatus is the fact that i t is not practicable to operate this type of apparatus closed to the atmosphere, as it is
Fi8ure %--Apparatusfor Merged-Procaaa S t e p
essentially an open-type construction. I n contrast to this, the merged process operates as a closed process in which no atmospheric contamination or atmospheric moisture can be entrapped to produce the undesirable condition of rancidity. There is obviously less refrigeration loss from a closed p r o m , which can be protected by insulation, &s compared to the open-type apparatus. Therefore, from the standpoint of economy of refrigeration, the merged process again has the advantage
December, 1931
INDUSTRIAL A N D ENGINEEIZING CHEMISTRY
Since the closed process makes possible the use of a much thicker film of material, this permits the very cunsiderablc reduction in size of the apparatus. The actual effective refrigerative surface required per pound of product produced by the merged process as compared to that required by the roll and picker box type of apparatus is as 10:lMl. So here again, on the question of space, the merged process has the advant.age, being many times more compact. The relative control ability of the two processes may be answered by the statement that full automatic controls are available and have already been applied to the merged process,
1357
whereas the exposed roll and picker box apparatus has not heen supplied with such control, if any has been worked out during its 25 years of use. The question remains as to the extent of the profitable application of this process. Results of preliminarytestsandstudies show that the application of this method of heat treatment and heat transfer, with its confined layer, its effective agitation, and its continuous motion in a controlled direction and under controlled conditions, indicates, and in fact insures, very worthwhile results in the ancient but indispensable art of heat transfer as applied in the process industries.
Scorch Retarders and Scorch-Retarding Materials' H. R. Thies GOODYBAR
'nne A N D
RVSBBR
co..AKRON. o m
The effect of several softeners upon retardation of It was used in the masterCLASS of m a t e r i a l s , known as scorch rescorch is shown. This effect is also obtained by using batch m e t h o d . Scorch-reLarders, h a s heen small amounts of some organic materials which might tarding materials were added be classified as scorch retarders. The effect of some of t o t h i s c o m p o u n d in t h e availa& for Some time and these materials upon the temperature coefficient of amounts of 0.25, 0.50, 0.75, has heen the subject of inscorch is found to be ofdifferent value at different temand 1.0 part per 100 parts vestigation in various lahoraof rubber; with softeners or perature increments below t h a t of t h e curing temperatories for a c o n s i d e r a b l y ture. and it seems that t h e temperature coefficient of activators, 1.0, 2.0, 3.0, and longer time. The ideal ma4.0 parts were used. terial of this typeisone which scorching decreases as t h e temperature is raised. In selecting a definite decan he added to a rubber compound and render it decidedly less scorchy at milling and cal- gree of scorch for all comparisons, solubility and swelling endering temperatures, yet not interfere with the curing rate of tests were made as shown in Figure 1. Here are shown the compound at its curing temperature. Such a material the turbid suspensions of rubber compound in gasoline, and, slrould have no effectupon color, should not be detrimental to in corresponding order, the same treated-rubber pellets which the aging properties of rubher compounds, and should he prac- have been soaked in gasoline for 2 hours. It is evident tically odorless when used in rubber; and its activity should be that the rubber sample which has been heated for a length such that it is necessary to use only a small amount of the of time sufficient to give a 105-mm. height of obscuring column (when immersed in gasoline 16 minutes and shaken 1 retarder. Practical experience has taught that certain softeners are of minute) just begins to swell after 2 hours; this indicates benefit when scorching trouhle is encountered in the factory, setup, whereas the smooth dissolving 8s in the case of pellets hut the usual conception is that such ingredients soften the heated for a shorter time does not. The time necessary to oompound; the fact that these materials possess a definite reach this definite degree of scorch is taken as the so-called inscorch-retarding effect has not been so widely taught. The use Time hented (niin.) Soaked in xasoline 5 10 15 20 30 2 hours of a scorch retarder seems to he a comparatively new practice, (1, 8, 6), but, ae will be shown later, the industry has been using compounds which function as such for years. The effect that these materials have seems to indicate that the temperature coefficient at some temperature under that of the practical cure is altered by the scorch-retarding componnd. If the same degree of cure is to be maintained in the same time in the presence of a scorch-retarding material as in its absence, and if a t lower temperatures the material does hold off premature vulcanization, this change in temperature coefficient should he observable. I n order to ascertain whether or not this condition is true, and in order to demonstrate the hehavior of these retarding materials at various temperatures, the work reported herein was undertaken. Method of Determining Scorch The solubility method of determining scorch (6) was employed upon a compound of simple constituents. Thc com35 40 45 10SCIear 6 IO 15 20 2.5 Hdiilit of column irnm.1 Time heated (min.) pound consisted of the followingingredients:
A
Pa,,*
Flame I S o l U b l U t r and Swelllne Testa 00 Rubber
100
10 10 3
1
_____
."_
1*A
t Rccdved September IO. 1931. Prepented before the Division of Rubber ChemirtrV at the 82nd Meeting of the American Chemical Society. BuUdo. N. Y.,August 31 to September 4, 1931.
dex number, and i t is felt that it represents a sharp duplicable end point. Particular stress is laid upon the fact that all oomparisons in this work are made using this degree of scorch. I n selecting a temperature range for study of scorching, four ternP'?ratures Were chosen and were Obtained by boiling the following liquids in the special container:
