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INI) USTRIAL AND EXCINEBEING CHEMISTRY ___-
Vol 23, No. 7
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Solid Carbon Dioxide from By-product Fermentation Gas’ C. L. Jones DnvIca Consonaiiov
OP
AYLKICA,92 Vnlivbaarrr ¶ v u , Nriv Y D l t l N Y
IDESPliEAD interest has been shown by engineers and chemists generally in the methods and equipment used in the manufacture of solid carbon dioxide (best knovn by the trademark “Dry-Ice”) on a large scale. With this interest in mind this discussion of a. recently built large plant operated by the principal producer of this material has been written. This plant, which is modern in every particular, draws its raw niatorial from the gases produced in the fermentation of starches to form solvents aiid is located in Peoria, Ill.
fied, enormous torinages of primary aiid secondary carbon dioxide are available from many other industrial operations to supply them with raw material. The principal problem to be met in designing this plant, was its adjustment t o the character of the market to make tonnages available for brief summer peak demands without excessive storage costs and to achieve sufficiently low costs of production for the support of freight shipment costs to considerable distances. It is hoped that the last-named requirement of large shipping radius will be only temporary, but to date the developed market for solid carbon dioxide is not sufficient to support sizable plants without such shipment, and further market expansion by many hundreds of per cent must be aehieved to change this situation materially. The solution adopted for both these problems at Peoria is inherent in the nature of the source. Since t.he gas has been wasting for severs1 years, i t is apparent that its value at the point of wastage from Commercial Solvents’ operations is arbitrary in the extreme, and, briefly stated as a matter of economic principle, is whatever amount the development of a market may create for it. The design of the solid carbo11 dioxide plant has been built around this central fact, as Uill he apparent.
Flbure 14ompressor Room
Source of Carbon Dioxide
The Conmiercial Solvents operation has already been described (8) and need not he reviewed here. The waste gases from this process, containing approximately 60 per cent carbon dioxide and 40 per cent hydrogen, are stripped of solvents in an adsorption purifier, and scrubbed with water under pressure to remove carbon dioxide, the unabsorbed eases naasine to a nressure-svnthesis nlant for the nroduction i f meihanoc The carbon dioxide gas removed bv water scrubbina is disengaged by releasing scrubber water-into a tank a t low pressure, aud it is this gas which serves as raw material for the manufacture of solid carbon dioxide. In composition it consists of 96 to 97 per cent carbon dioxide, traces of residual odorous compounds, and the remainder hydrogen. At full solvent production rate this gas is equivalent to 150 tons of pure carbon dioxide per day. When this figure is compared with the maximum 30-ton market so far developed in tributary territory, the doubling of effective daily summer supply by existing season storage, and the previous existence of 35 tons of other solid carbon dioxide producing capacity owned hy the same producer in this region, i t is evident that new operations in this district for some little time to come will have to be dictated by considerations other than shortage of supply. Needless to state, when such operations are justi1
Received May 7. 1931.
Figure 2-Odor
Removal by Reich System
Payment for gas used in the production of solid carbon dioxide is based upon weights of solid shipped, no value or cost accruing against carbon dioxide lost by unavoidable compressor leakage or by evaporation in bulk season storage. The cost of solid manufactured in winter for summer consumption is hence burdened only with capital charges on season storage, handling costs, and actual energy loss, bearing
no added cost for e v a p o r a t i o n loss. When savings in c a p i t a l charges on production equipment are considered, the stored product may be regarded as a little cheaper than p r o d u c t manufactured in similar plants without storage. Assurance of supply largely without regard to continuity of parentplant operation is of course a collateral advantage. Plant Capacity
Odor-removal equipment is illustrated in Figure 2 and employs the Reich system, licensed under Vnited States Patent 1,519,932. The principal features of this system, employing dichromate solutions and sulfuric acid as reagents, have been described elsewhere ( 1 , $). It will be sufficient here to state that previous purification of the raw gas by Commercial Solvents Corporation in its solcents-recovery plant greatly reduces the necessary consumption of chemicals and affords an added f a c t o r of safety in maintaining quality of the finished product. Hydrogen is removed by purging from the top of a refrigerated fractionating column. Purged gases commonly r u n approximately 50 per cent carbon dioxide and 50 per cent hydrogen, and are returned to Commercial SOL vents Corporation for the manufacture of methanol.
In consideration of this especially favorable s i t u a t i o n , the plant c a p a c i t y was fixed at 55 tons, and season storage or regene r a t o r c a p a c i t y a t 4000 t o n s (8,000,000pounds). Withdrawals from storage are necessary only on approximately 70 days annually; hence it will be apparent that capacity will care for some 300 per cent expansion over the 1930 peak demand, without addiFigure +-Solid Carbon Uiolide Presses tions to the .nlant..and without requiring even 50 per cent of capacity production from ComRefrigeration mercial Solvents. Power is purchased from the local power company. LowCompressors cost water is airailatrle for condensing purposes from wells at The same considerations give assured ~ u p l ~ almost ly without regard to shutdowns of short duration, and hence made it
Fleure 4-Band
Saws for Cutting Solid Carbon Dioxide
possible to reduce leakage and operatiiig cost by the use of only one main raw-gas cornpressor and one mompressor, without spares. Both are Worthington duplex compressors, synchronous motor-driven, and are illustrated in E'igure 1. Expectations of continuous performance of these compressors have been exceeded, and to date total outages have been only 91 hours out of 3483 scheduled production hours. As a result, the necessity of large storage from the standpoint of assuring continuity of shipments has not yet been apparent. Removal of Impurities
Owing t.o the exceptionally desirable charilctcr of the raw gas, rernoval uf impurities has not proved eitlier ditGcult. or
expensive
a favorable temperature of 5.6' F. The refrigeration cycle employed for deiivering cold liquid carbon dioxide to presses and the solid-forming practice are capable of wide variation and cannot be described in detail a t this time on account of possible patent complications. It will perhaps be sufficiently informative to state that the DryIce Corporation of America operates, a t its various plantfi, several designs of particular piping layouts and specific schemes of solid formation, each having certain advantages under specified conditions. Piping layout was accordingly designed manifolded and cross-connected a t every possible point, so that a wide choice of hook-ups is available to the plant operator by inerely resetting valves without altering
Yol. 23, No. 7
I.VDUSTRIAL AMD ENGINEERING CHEMIXTRY
800
connections. This flexibility of operation can be and is utilized to meet changing conditions. Variations in power cost due to altering minutiae of practice in liquid cooling are not important factors in the total cost of solid carbon dioxide delivered so long as proved principles of sound refrigerating engineering are not violated. Operating advantage and kilowatt-hours purchased per ton manufactured must eventually govern development of the art even though a t variance with the thermodynamic ideal based on studies in which perfect regulation and complete freedom from leakage losses are assumed. Presses
Similar considerations governed the selection of press eauiDment. Presses are four in number, vertical, with caststkeichambers tested to 375 pounds per square inch pressure. They turn out O‘ X ‘ O X loinches, which are sawed to 10-inch cubes to meet the demands of the current trade, which in appears to prefer this size* A press line is Figure 3. Conveyor and saw is shown in Figure 4. Here again has been the principle Of and it is believed that any known type of solid may be made or any known type Of practice without presses* Patent complications forbid description, but it may be stated that maximum capacity Of 2500 pounds Of Dry-1ce per press per hour has been attained when solid is formed by the solidification practice now employed.
on account of the regeneration or, more properly, preservation of crystalline structure of the stored product when a product of controlled quality is stored under proper conditions. The regenerator (Figure 5) has attracted some interest as the coldest structure of such large size in the world. It is approximately 40 feet in diameter by 80 feet high, and when filled loses considerably less than 0.1 per cent by weight of its contents daily through evaporation. Its design has naturally involved interesting problems of insulation, ventilation, structural design to minimize effects of thermal contraction, and mechanical handling under rather unfavorable conditions for lubrication and maintenance, etc. Patents have been solicited on many phases of this development. Marketing and Distribution
will no doubt Further advances in manufacturing take place. It should be stated, however, that in the past entirely too much emphasis has been placed on methods of manufacturing solid carbon dioxide cheaply, and not enough on the development of markets adequate to support units of economical size without sacrificing much or all of the saving by ~ow-cost manufacture in the expense of shipping the product considerable distances in search of a market, Sound marketing and distribution methods have been even more important than manufacturing processes in the liquefied carbon dioxide industry since its inception than fiftyyears ago, and nothing has yet appeared to indicate that this will not be equally true of the younger, solid carbon dioxide industry for some years to come,
Storage
Literature Cited
Finished cubes are bagged by hand (Figure 4), and either loaded into special cars for shipment or hoisted into topopening season storage structure or “regenerator,” so called
Chem. M e l . sa, 677 (1925) (1) (2) Reich, Ibrd., 58, 138 (1931). (3)Woodruff, IND.END. CHBMI. is, 1147 (1927).
Activated Bleaching Clays’ 0. Burghardt BADSALZELMEN, BEZIRK(MAQDEBURQ), GERMANY
LEACHING earth or clay is a decolorizing and clarification agent that is #much used in the oil industries for the bleaching of vegetable, animal, and mineral oils, fats, and waxes. There are two types of bleaching earths-the natural or fuller’s earth and the highly active, chemically processed earth. The former, which are obtained from selected raw material and have naturally a certain bleaching power, require only simple treatment in their preparation, such as drying of the raw earth and milling to the desired fineness. Only with material containing sand or stone is it necessary to introduce, before drying, the step of water-washing to settle out the impurities from the clayey substances, The second type, or chemically activated clays of high bleaching power, are produced by a process involving treatment with sulfuric acid or, preferably, hydrochloric acid. Such chemically treated material has an efficacy considerably greater than that of the natural bleaching earths. For this reason less bleaching agent is required for a desired degree of decolorizing and less oil is lost in the process, since a certain percentage of oil is retained in the earth after filtering. In order to operate most economically and reduce this oil loss
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Received January 14, 1931. Translated by Robert Calvert.
to a minimum, one uses advantageously the most highly activated earth possible. Such highly activated, chemically processed clays are produced principally in Germany, but because of their desirable properties they are being introduced rapidly into other lands where they are being used in increasing amounts. The industry is well developed in Germany for two reasons: First, it was here that the process of increasing the bleaching power through the use of mineral acids was discovered; second, there occurs in South Germany, in Bavaria, an earth especially suitable for this process, the so-called “Isartone.” Raw Material for Activation Treatment
This particular clay varies from green, yellow, to gray in color and occurs in layers of variable thickness. The clay stratum proper is generally quite clean and seldom contaminated by sand or limestone. The layers are of variable quality. They lie a t different depths, under 2 to 20 meters of overburden. A typical analysis follows: Moisture Ignition loss SiOz FeaOa
% 12.1 11.4 53.9 3.8
% 16.3 0.9 0.8
AlaOs CaO
%:lies
and remainder
0.8
