PILOT PLANTS
Pilot Plants in the Petroleum IndustryA Panel Discussion Summary of the Panel Discussion on Pilot Plants Presented before the Division of Petroleum Chemistry, 123rd Meeting, American Chemical Society
LEO J. BLATZ, Standard
Oil Development Co.
I
N A series of three groups of articles the papers comprising a panel discussion on pilot plants in the petroleum refining industry have been recently presented (1). At the conclusion of this discussion held at the 123rd National Meeting of the AMERICAN CHEMICAL SOCIETY, a summary was given, including questions and answers from the floor. Reader comments on the entire panel as published were also invited. This article is a combination of this summary and reader comments, affording a final “recap” of this subject. Pilot Plant Studies Must Be Needed
*
a
As an over-all impression of the panel, i t was apparent t h a t greatest interest lies in determining ( a ) when pilot plant work should be done and ( b ) what the scale should be. Because differences in cost of pilot plants employing alternate designs and types of equipment and instrumentation are relatively small compared to over-all cost of operation, these construction differences should be secondary considerations. Nevertheless, major savings in operating costs can frequently be achieved if, by improved design, the size of the operating crew can be reduced. From the “when” standpoint, the general premise brought out was that pilot plant work should be conducted only when preliminary bench-scale studies have defined a n area of knowledge t h a t requires investigation in a pilot plant. Studies where pilot plant work has been initiated solely as an expedient in attempting t o conduct broad research on a very pressing problem have frequently proved fruitless, particularly when viewed in terms of the large investment which has been made for only a meager return. An early guide t o the scale of pilot plant operations can often be obtained from the answer to the question “What is needed from the study-engineering data or a reaction product?” A small pilot plant size may criticallv limit the sample volume. The upper limit in size is correspondingly based on the degree of engineering scale-up considered reasonable. I n some cases a particular part of a new process may be investigated in a full scale mockup. This approach is frequently encountered by those ernpioying the utilized concept of industrial research discussed by Maerlier and Schall in the first article of this series (la). Unitized
VS.
Integrated Approach Still a Question
Corollary to the question of size of the pilot plant is the degree of completeness of the operation carried out in the pilot plant. This involves such auxiliaries as feed preparation facilities and product recovery equipment. There are generally two reasons for conducting an integrated plant-type operation. The feed stock employed may be so expensive that it is necessary t o segqegate and recycle unconverted feed from the standpoint of minimizing cost for the pilot plant operation. More important, if recycle is t o be employed on the envisioned full-scale operation and
minor amounts of materials may be present which will poison the reaction desired, it may be necessary t o conduct very complete pilot plant operations t o study the build-up of these poisons in recycle streams. This approach may be particularly necessary in studies of catalytic operations where minor amounts of poisons may have a very major effect on catalyst activity or selectivity. l e a k Detection and Feed Stock Standardization Are Problems
Methods of determining leaks in pilot plants offer a widespread and very annoying problem. A generally applicable technique brought out in the discussion is the addition of helium to the process flow and the use of a simplified mass spectrometer to search for helium leakage from the equipment. A very real advantage of this leak detection method is the opportunity for carrying out leak testing while actual process operations are in progress, since the amount of helium t h a t must be added is quite small and its effect on the reactions generally insignificant. I n attempting t o compare petroleum industry pilot plant studies with Lhose of other industries, a rather interesting comparison was drawn with studies in the food industry. Although most people dealing with research in the petroleum industry feel t h a t standardizing feed stocks is a very difficult problem, they fail t o realize how fortunate they are compared to those working in industries involving perishable foodstuffs. I n addition, pilot plant studies in food processing frequently are forced t o a rather large scale by the size of the individual units. Thus, if the item under study is something like potatoes or tomatoes, a very large sample becomes necessary t o ensure that it is truly representative This is, of course, governed by the extreme variability among these units of biological material. For example, fruits growing on different plants or even on different portions of the same plant vary considerably in their quality, and the added complexities of weather, degree of maturity, variations in soil and deterioration upon storage further aggravate these individual unit differences. The effect of too small a scale in the pilot plant in the food indust r y thus makds itself felt in a lack of precision in quality measurements on the product when two lots of raw material are processed under identical conditions. T h e variation may be so great t h a t differences in quality resulting from changes in process variables are entirely obscured by the inherent variations in the lots of materials chosen for test. Fortunately, most of the studies in petroleum refining do not involve problems of this type, and thus the scale of operation is dictated by the information needed and not by the necessity for obtaining a representative sample. literature Cited
(1) a. IND. ENG.CHEM.,45, 1619 (1953). b. Ibid., p. 1836. . c. Ibid., p. 2133.
Reprints of the Symposium on Pilot Plants, appearing in the August, September, October, and December 1953 issues, may be purchased for 75 cents each from the Reprint Department, American Chemical Society, 1155 Sixteenth St., N.W., Washington 6, D. C.
December 1953
INDUSTRIAL AND ENGINEERING CHEMISTRY
2607
