ENGINEERING, DESIGN, A N D PROCESS DEVELOPMENT scrubbers, and coordinated all phases of the work. The efficiency with which the final change-over operation was carried out is reflected in the fact that train No. 1 was out of production only 29 days, train No. 2 only 26 days, and both trains were out of production simultaneously less than one day. After a short period of preliminary operation, during which flows and temperatures were adjusted and the operators obtained the “feel” of the new plant, operating rates were stepped-up t o those anticipated in design and a test run was carried out to demonstrate adequacy of the performance. Operating rates have remained at satisfactory levels for the three years subsequent t o the plant conversion. A4daily peak production capacity of over 277 tons of ammonia has been reached, and the peak monthly average has been approximately 271 tons per day. Annual production has averaged 252 tons per day. Anticipated savings in the operating and maintenance labor have been realized. The performance of all units in the plant has justified the decisions that n-ere made st various stages of the project.
Acknowledgment The author wishes to acknowledge the contribution of the staff of TVA’s Office of Chemical Engineering t o the work covered in this paper. E. J. O’Brien and J. L. Snyder were responsible for operational phases of the work. IF. H. Haynie, A. V. Slack, and L. B. Hein conducted design studies, and H. Y. Allgood waq responsible for plant tests carried out in connection with the work
Literature Cited (1) Curtis, H. A., “Flxed Sitrogen,” The Chemical Catalog Co., h e . ,
New York, 1932. (2) Miller, A. IM., and Junkins, J. N.,C h e m dl- M e t . Eng., 50, KO. 11 119 (1943). (3) Hein, L. B., Chem. Eng. P T O ~ T 48, . . No. 8, 412 (1952). (4) Slack, A. V., Allgood, H. Y . ,and Llaune, Harold E., Ibad.. 49, No. 8, 393 (I 953). RECEIVED for review May 24, 1954.
ACCEPTEDSeptember 3 lq5.4
Process Research in Plant and Expansion FENTON
H. SWEZEY
E. 1. du Pont d e Nemours & Co., Inc., Waynesboro, Va.
Plans to expand manufacturing facilities should include a detailed study o f the manufacturing process; this should begin well before the expansion i s planned. This research should indicate how plant capacity can b e increased without duplicating existing equipment. Increased output of present equipment follows decreased reaction times, increased solution concentrations, and combined process steps. After achieving maximum output from existing equipment, the possibilities o f adding low cost supplementary equipment are determined. Thus, process research can show where a reaction can be divided and the reacting materials transferred from the starting equipment to an inexpensive vessel for reaction completion. Savings can be realized b y taking advantage o f special process features and adapting techniques and equipment from other industries. Alternative processes offer possibilities and in t h e event that they do not fit present plant conditions, useful information about the existing process may result from their investigation.
P
LAKT adaptation and expansion present real opportunities for adding to presentfacilities at attractive investment figures,
as well as for achieving lower operating cost, increasing flexibility, developing new process features, and improving product properties. Skillful process research, defined for our industry as a specialized combination of chemistry, engineering, intuition, inventiveness, and experience, has a key role in arriving at these desirable objectives. Process research starts with equipment speed-ups, step simplification, and changes from batch to continuous processes, and progresses to the development of llew procedures and the application of unique of old and new knowledge. The continued expansions of the chenlical industrj. haxre repeatedly t h a t larger output w-ill be needed from the present on at a later date. I n order to avoid the method of adding only additional equipment to duplicate present facilities, process research studies directed at adaptation should be initiated. 1. Make a n intensive study of all features of the present process t o establish t h e chemical principles and t o find variation effects: Much additional information remains to be developed
2486
besides the current process data. One fertile line of investigation is t o determine exactly what takes place and what the chemical composition is a t the various time intervals throughout the cycles and reactions used. 2. Set up a pilot plant program t o determine t h e effect of operating the equipment a t increased rates. This will define to be overcome. the 3. Initiate a chemical equipment and engineering survey to locate opportunities for simplification and combination, as well as unique new arrangements. These studies will provide the groundl\-ork and data for showink what can be done. As soon as the possibility of expansion becomes quite definite, a process study group ehould be set up which includes chemical engineers, process men, and specialists, the number depending on the magnitude of the problem. I n v i e r O f the time required, it is essential to initiate this part of the program as far as possible before the expansion date is set. -% year before the decision has been reached to proceed is often insufficient. This group will have the responsibility for selecting the main lines of attack, visualizing t h e possibilities for conductillg them, and then effecting the necessary program. New and unusual techniques will be sought, and the help of experts along
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 46, No. 12
PLANT ADAPTATION specialized lines will be obtained. A master sheet in which the various proposed attacks will be outlined is desirable and will be used to make comparisons and t o follow up the decisions reached. A n over-all picture of status and progress is thus made available. Four specific types of investigation for this group are discussed.
Increased Output from Present Equipment The well-known fact that the output from present equipment can often be increased in truly great proportions by process reEearch is the initial challenge and point of attack (6). Changing the gears or valves to increase throughput rates frequently brings the process above the efficient technological level of current experience. The resulting inferior yield figures and unacceptable product quality require keen process research t o determine how to operate successfully at the higher output levels. Some possibilities are: 1. The data developed in the pilot plant stage of the initial program ran be used as a starting place t o determine t h e optimum higher rate process setup. Systematic variations in time, temperature, place, and method of reagent addition are some of the tests to run t o locate the conditions for turning out maximum output. 2. Decreased reaction time can supplement the increased throughput attack. 3. T h e use of increased solution concentrations is another means. A11 these approaches will require the latest type control instruments. The help of specialists in unconventional places is invaluable. 4. Combine process steps t o increase output and make extra equipment available. Some examples are: The use of larger batch sizes in the same equipment was followed by a change in catalyst t h a t doubled output. Improved purity of ingredients was the next step; the net result was a fourfold increme in production. The change in catalyst resulted from a clearer understanding of the reaction mechanism, follo-ived by a research project that worked out the chemistry of the process. A bottleneck in the washing of precipitated polymer to an acid-free state led to a study of this operation. A change in the physical form of the polymer, increased temperature of wash liquid, and alternate wash and drain steps combined to give a threefold capacity increase. Different means of attack should be sought in achieving increased output for present equipment. Take the example of the use of an organic solvent t h a t requires a complicated and costly set of equipment for its recovery. The first objective would be to increase the rates of operation of the recovery equipment in order to raise the throughput. Other process changes to consider are: 1. Increase the solvent concentration coming to recovery 2 . Reduce the amount of solvent used in the process 3. Introduce a simple pretreating step which will radically reduce solvent requirements 4. Use t h e solvent directly as it comes from the process so that recovery is not necessary
If trouble in product quality or process continuity results from a change made to increase output, these difficulties should be resolved. Additional changes, refinements, or discoveries will show how to overcome the trouble and capitalize on the potential large gains made initially.
l o w Cost Additions to Present Plant After the maximum output has been obtained from the present equipment, opportunities should be seized for markedly increasing production by the addition of low cost equipment to supplement t h a t now in use. The output of different units may be significantly increased and then equipment added a t a key point. December 1954
The addition of one simple piece of equipment can frequently increase output of an entire train of units. A 1 0 0 ~ oincrease in the output of a high boiling ester made by the absorption of process gas in a liquid reactant in the presence of a catalyst was achieved by installing an additional inexpensive vessel. This permitted the reaction to be completed in the second tank after the initial combination had occurred in the original absorber. T h e expensive equipment was then used only for a fraction of the time originally required. The process research in this instance determined the point where the reaction could be divided and then decided which part should be done in the added equipment.
Special Process Features and N e w Viewpoints The need for increased production presents opportunities for specialized combinations of process skill. Significant departures from present practice are helpful (4). Visualizing new lines of approach t h a t result in ingenious methods provides the cornerstones for low cost expansions. Places where a large number of steps are involved particularly lend themselves t o process developments. An example based on four process steps is as follows: 1. Batch operation was changed t o continuous operation 2. A new novel disintegration method was used 3. The chemical reaction was carried out on a moving belt instead of manually 4. A new type of pellet-making equipment from another industry was adapted t o the current problem
The use of ion exchange resins in helping t o develop improved processes illustrates the application of new viewpoints to process developments; these have been described extensively. An illustration of good process thinking occurred where a catalyst was changed not t o achieve yield increases of present product but to change the type of reaction so t h a t the process produced a second material for sale while maintaining full production of the original chemical. A different attack came up where strict specifications had been established for the manufacture of a polymer of a definite molecular weight. A process was required that delivered the specific molecular weight, but this was costly from a production standpoint. The process feature here was not to seek better methods for producing the desired polymer, but t o develop means for using the polymer t h a t could be made economically. The important role of the catalyst cannot be overemphasized. Thus a product as well-known as DDT has been reported recently to have been made by a new process where marked gains were achieved by the substitution of fluosulfonic acid for sulfuric acid ( 1 ). Special skills enable the adaptation of process procedures from one industry to another; a familiar case is the method of manufacturing continuous steel sheets t h a t was taken from the paper industry, and then in turn adapted t o spin viscoEe rayon. Another aspect of adaptation is searching the technology of other industries to locate a piece of equipment which can be readily changed t o some special need. Continuous deaeration in a thin film, reactions on moving belts, and adaptations of special pumps t o chemical processes are examples of new viewpoints. The fusing of chemical, mechanical, and engineering skills with process experience provides a group attack. Skilled mechanical improvements will tremendously simplify a process and enable high output levels t o be reached. The role of clear thinking in expansion was illustrated in connection with a proposed plant increase b y adding low cost equipment for the fractiomtion of a vinyl monomer of improved quality. Two viewpoints were soon in evidence. The first was t h a t chemical treatment would be needed (judged by recent data) t o obtain the 99.9% purity product of suitable polymerization activity. However, this chemical step would require addi-
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
2487
ENGINEERING. DESIGN. AND PROCESS DEVELOPMENT tional equipment and labor cost. The decision to proceed with properly engineered distillat,ion equipment was based on the folloviing facts overlooked by the chemical advocates: 1. Present equipment was doing an inadequate distillation job, because it was not large enough. 2 . Present equipment was not designed t o distil in the nianner uzed. 3. Present arrangeinent did not permit the use of the proper controls. 4. Distillation had produced niat,erial of the proper activity and purity.
Development of Alternative Processes The development of unique and different processes to rnake the same product is an intriguing and fruitful field. Continuous processes speed up batch methods but gcnerally follow established process principles. This t,opic refers t,o the development of cntirely different process schemes. While such radical c h a n g e may not appear to fit in plant adaptation developments, research on a completely different process nil1 shed light on the procedure
now in use. The story of developing a new method for piioiol manufacture is filled with ideas for new process procedures ( 2 ) . d n aiticle discuqsing process alternatives for making urea illuqtrates this thought; many otheis can be found (3).
Summary 1-arious types of process research at'tacks are available and should be used t o 5olve expansion problems. The investigation mupt go beyond routine methods, and skillful selection from the various choices must be made. The full cooperat>ionof reseai'ch, process, engineering, and operating people is required for sucress.
Literature Cited (1) C k e m . Eng., 59, 247 (February 1952).
( 2 ) Cranford, R. 11..Chem. Eng. S e w s , 25, 235 (1947) (3) l b o s e b o o m , A , Chem. Eng., 58, 111 (March 1951). (4) Sittig, AI., Ihid., 57, 106 (December 1950). ( 5 ) Bwezey, F. EI., Ib.i'd., 54, 121 (June 1947).
RECEIVED for review lluril 30, 1954.
ACCEPTED September 10, 1954.
Economic Evaluation of Plant R. D. NEWTON AND C. W. WElL Chas. Pfizer & Co., Inc., Brooklyn, N. Y. Before a new capital venture in plant expansion is undertaken, its economic future should be carefully evaluated. A systematic appraisal presented graphically will often indicate trends and results which might otherwise be overlooked. Over the desired range of market volume the variation of sales price, manufacturing cost, profit, and capital investment should be determined. Choice of optimum plant capacity is thus possible. For the plant size selected, the effect of sales price and output changes may be ascertained in a similar manner.
0"'"ii
the production level selected for expanding an existent plant is based on a soinem-hat arbitrarily selected highcr sales volume at the current, sales price returning a satisfactory profit. Little consideration is given to the variance of economic conditions over the entire range of expanded volume. Unfortunat,ely there is no magic formula which may be employed for determining the proper level to which an expansion should be carried. However, the importance of correct,ly deciding this value fully justifies an orderly presentation of the facts indicating the economic course of events over the expanded output,. A graphical presentation not only reveals these continuing changes but also allows extrapolat,ion of some of the dat,a. Capacit,y determinations should be based on maximum profit,ability, which is the maximum excess of income over expenditure for the investment in question. To do this the variation of sales price, investment, and cost must be calculated over the entire range of contemplated operation. The proper combination of these three independent functions 1%-illt.hus reveal the point of optimum profitability.
Sales Proper sizing of a plant expansion demands first of all a study of the variation of unit sales price as a function of annual sales volume. T o accomplish this, the company's share of the total market a t various sales prices must be ascertained. Such a determination is a very difficult, question to answer in direct quantitative terms, since the factors involved are in most cases not controllable by the producer. Fortunately in t,he expansion of an 2488
existent product line, a great deal more information is availablc than exists for entirely new ventures. Thus some of the complicating fact,ors are reinovpd or a t least reduced. An historic price pattern and current, market volunie by consumer groups are a.vai1able. The producer is aware of his product's acceptance, use, a n d potential. The test of competition has indicat'ed the producer's share of the total market. I n the expansion of a product line, a price should prevail tliat provides a satisfactory return in line with company policy. Competition, substitutes, and usefulness-over which the producer can exercise relatively little direct control-can have n notable effect on pricing in a free economy. Even though t,he product may possess a n-ide potent,ial market, competitors' countcrineasures to price reductions and sales volume increasc must be contemplated and the effect noted. I s t,he demand for a product is stimulat.ed, increased productive capacity and new process t>echniquesjoin to reduce costs and combined with increased aompetit,ion, lower prices result,. I n t,urn, new markets and uses are attracted. iz market study reveals that a curve may be developed s 1 i o ~ ing the variation of unit sales price as a function of sales volunie for an existent product,. Such a curve, which can and does have many different forms, is illustrated in Figure 1.
investment The cost of capital investment must be determined over tlic range of attainable sales volume. Large process plants achieve high capacity through the use of large singular units as ne11 BE
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 46, No. 12
