LANTS LARGE SCALE SAMPLES LABORATORY A
versatile laboratory for preparing organic chemicals in batches of 10 to 500 pounds is the answer to one of the problems of developing new chemicals. Each laboratory technique practiced by the synthetic organic chemist has been scaled up without abandoning complete flexibility of application. Unit operations most commonly needed include grinding, milling, mixing, crystallization, distillation, extraction, filtration, and drying. Corrosionresistant equipment has been provided to carry out these steps under properly controlled conditions. A t the stage when a new chemical must be tested in drum quantities, this laboratory can provide the necessary larger samples on short notice. More than one chemical preparation a week has been the record of the past year. Availability of sufficient quantities of new chemicals for their thorough evaluation leads to a sounder economic appraisal of new chemical projects. On this basis, a better selection is usually possible among the more promising projects for larger scale pilot plant development. The large scale samples laboratory is thus an essential link between small and large scale process development work on new chemicals whose usefulness must be further established.
R. W. CAIRNS Hercules Powder Co., Wilmington, Del.
I
N MOST research and development projects, there are several major turning points where important managerial decisions must be reached. In new chemical development work, such points usually number a t least three or four, involving changes in scale of effort or physical magnitude. Thus, the first decision to scout a new field of chemistry may lead to further decisions to undertake or continue the development of promising leads, first in the laboratory, then in the pilot plant, and finally on a commercial scale. In general, the rate of expenditure of effort and funds mounts rapidly as each turning point is passed. Thus each successive decision to continue a project must be backed up by more reliable supporting information. An exploratory study may be initiated on little more than a hunch, but supporting technical results must be obtained before plans are approved for serious process development activity on a specific product.
Figure 1. Glass- and Nickel-Lined Reactors and Columns Showing Associated Piping
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Figure 2.
Grinding and Milling Equipment
Justification of a pilot plant developincnt calls for a thorough analysis of laboratory process data, disclosing important factors affecting costs and operability of the process. I t is quite important to have corresponding evidence on product acceptability and utility before funds are committed for pilot plant construction. In this respect, research management can easily find itself in a paradoxical position. Sizable quantities of a research product may be required for early field trials to gain evidence in support of equipment expenditures necessary to produce such samples. The author's laboratories have often been in the position of needing large samples for test purposes long before the plant design engineers would call for process data from the pilot plant,. Repeatedly, it would be necessary to restrict application research, thus endangering the soundness of future decisions. Alternatively, large samples could be accumulated through repetition of many laboratory runs. This procedure is laborious and costly. What was really needed was a scale-up in laboratory glasswarea magnification of such equipment bcyond the usual limits of safet,y and convenience. The techniques of an organic chemist in the laboratory are extremely flexible. In his hands, a few simple pieces of glassware can serve as a complete chemical plant, set up to carry out effectively almost any conceivable sequence of the unit operations of organic chemistry. The objective at Hercules was to extend this flexibility to a scale of operation normally thought of as pilot plant operations, and efforts in this direction have culminated in a ne\v adjunct to the Hercules Experiment Station, a two-yearold addition which is called the Large Scale Samples Laboratory. The equipment in this laboratory has been selected and arranged so that normal laboratory procedures can be reproduced on a large scale. The keynote of the laboratory is versatility. The various major items have been permanently installed, yet the arrangement is sufficiently flexible for a a-ide variety of reactions to be carried out with a minimum of changes. Some idea of this versatility can be obtained from the obswvation that operations may be carried out to prcpare product. batches ranging in size from 10 to 500 pounds at temperatures from -75" to 400" C. and at pressures of 2 mm. absolute to 100 pounds per square inch gage. Being large, the equipment is operated under supervision of chemical engineers (from the Pilot Plant Division), yet the processes are directly adapted from the procedures furnished hy the research chemist. Rather than merely present a catalog of t'he equipment which was finally selected to comprise this laboratory, it is more enlightening to compare its operation wit,h the corresponding activities of the organic chemist, in the laboratory. For example, the organic chemist's stock in trade is a three-necked flask suitnblj-
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equipped with devices for mechanical agitation, introduction of reagents, and withdrawal of products. Correspondingly, the heart of the large scale samples laboratory comprises two reaction vessels with associated feed tanks, condensers, and receivers. One set of equipment is glass-lined throughout, whereas the other is fabricated from nickel. Specifically, there is available a 100-gallon jacketed, glass-lined kettle with variable speed agitator and a &foot, 6-inch inside diameter jacketed, glass-lined column which can be packed with saddles or rings. Attached is a double-jacketed, glass-lined condenser with 30 feet of condensing area so piped that condensate can be wholly or partially returned or completely taken off, Tf the unit is used as a still, a 50-gallon glass-lined receiver is available. The kettle may be heated with water, steam, or Dowtherm vapor, and the condenser and receiver are attached to steam or 77-ater lines. If the pH of the reaction mixture is high, a similar setup in nickel is available. The pot is of 60-gallon capacity and is equipped with a variable speed turbine agitator. The column is 5 feet high and 4 inches in inside diameter; the condenser is conventional shell-and-tube type, and the receiver is of 30-gallon capacity.
Figure 3.
Portable Stainless Steel, 50-Gallon Tank and Stirrer
130th ot these reactors, ir-hich are shown in Figure 1, arc located on a mezzanine level in the center of the building. If the organic chemist must prepare his reagents in advancefor example, by subdivision-he usualll- has a mortar and pestle handy. As counterpart of this simple hand operation, a choice of several small mills can be made for grinding or milling a solid to a powder. These include a stainless steel, ~ater-jacketed hammer niill with a capacity of 50 to 100 pounds per hour, a small rotary cutter, a small jaw crusher, and an attrition mill, all of 10 to 20 pounds' hourly capacity. This equipment, ehonn in Figure 2, is segregated in a special room to prevent dust from contaminating the rest of the building. If the preparation and handling of solutions cannot be casily carried out in the reaction vcssel, auxiliary portable t,anlcP ivith
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scale of 600-pound capacity and a traveling-crane scale that may be set up where needed. One element that does not lend itself to simple scaling up in size is the chemist's Bunsen burner or ice bath. For sources of heat, steam is used up to a temperature of 170" C., and a Dowtherm unit capable of producing 136,000 B.t.u. per hour is used in the upper temperature range. The Dowtherm system is permanently piped to the reaction kettles. High points of the system are connected to a vacuum, and condensate return is by gravity through trenches in the floor of the building. Temperature control for the reaction kettles is maintained by means of automatic indicating controls. Thermocouples may be installed a t other critical points in the equipment, and temperatures are recorded on a six-point potentiometer a t the central control panel which is shown in Figure 4. To carry out operations a t temperatures below 20' C., a portable refrigerating unit has been constructed and may be attached as needed to any of the jacketed units. It consists of a trichloroethylene reservoir, a cooling chamber to Figure 4. Central Control Panel which dry ice is charged, and a circulating pump. Equipment for controlling vacuum system, temperature recording The organic chemist's frequent use of distilled system for reactor kettles, and electrical units water led to the installation of a two-bed ion exchange system capable of providing- 100 stirrers are available These include two 50-gallon stainless gallons of water per hour a t ion concentrations of 3 to 4 steel tanks, one of which is depicted in Figure 3, and two 30p.p.m. gallon glass-lined tanks, all on whenls; a self-priming pump for The reaction vessels previously described can be operated in material transfers; and two portable agitators. These comeconjunction with the associated condensers, either in total reflux spond to the research chemist's stock of beakers. The laboratory or airanged to withdraw the product by partial or total conscale balance for weighing reagents is replaced by a portable dial densation. When operated as stills, the vessels may be brought
Figure 5. Absorption-Extraction Unit Receiver at left and column left oenter
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Figure 6. Jacketed, Glass-Lined, Horizontal Plate Filter
down to low pressures through use of a three-stage steam ejector equipped with a barometric intercondenser; this system is capable of exhausting 5 pounds of air per hour a t 3 mm. pressure. The steam jet proper is located on the roof of the building, and the controls for steam, water, and vacuum are adjusted a t the central panel. Vacuum piping t o the various units is of .?-inch porcelain pipe. With suitable adjustmenh, the reaction kettles can thus be equipped either for solvent removal by evaporation or for taking off the product in the vapor st'ate. In case the product must be separated by an extraction step analogous to the organic chemist's separatory funnel procedure, a simple absorption-extraction unit was installed; the major item of this is a 10-foot high, 6-inch internal diameter glass-lined tower. It is packed with Raschig rings and fitted a t top and bottom with glass tees for visibility. Two jacketed glaes-lined vessels, one with agitator and one with feed tanks, are connected a t the ends of the column with a glass pump and rotameters. Two other glass-lined vessels serve as receivers. Associated with this extraction unit, there are also available porous Karbate plates and drilled Karbate nozzles. With their aid, the column can be used not only as a battery of separatory funnels (for liquidliquid contacting), but also as a gas-washing or scrubbing unit) (gas-liquid), or even as a Soxhlet extractor (solid-liquid). Much of this unit is shown in Figure 5 . I n most cases, the glass or nickel kettle may be used to carry out crystallization processes. Provisions are made for pumping the resultant slurry into one of three filtration units selected on the basis of corrosiveness, filterability, and volume of solids: First, an oversized, jacketed Buchner funnel, 2 feet in diamekr and glass-lined, is the type usually referred to as a horizontal plate filter (Figure 6); its temperature may be controlled by water or steam in the jacket. The plate is a perforated porcelain disk for either pressure or vacuum filtrations. The second unit is a stainless steel Sparkler filter, with a 4-square foot filtering area. It is mounted on a frame together v i t h a pump and may be brought to the location where it is needed. The third filter is a stainless steel centrifuge with a 12-inch basket; it has a variable drive and is mounted on a portable base. Precipitation and
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filtration of the final product may also be carried out in the reaction vessels and filtration equipment. The h a 1 operation of drying the product is usually carried out in a tray-dryer 'through which hot air is circulated. Occasional use is made of small vacuum dryers a t other locations a t the Experiment Station. This large scale samples laboratory is housed in a building with about 3000 square feet of floor space. Safety has been a major consideration in its construction. All electrical equipment is explosionproof and all vulnerable breakage points in the nonmetallic piping and pumps are shielded. A tram rail systcm facilitates the movement of heavy objects. The versatility of the equipment in the large scale samples laboratory poses a problem not usually encountered in the ordinary run of pilot plant operations, that of decontamination. Traces of materials from a previous sample-for example, a wall film in a lubricant, in a gasket, or in other crevices-might well contaminate a product or even inhibit a reaction. Accordingly, scrupulous care is exercised in cleaning all equipment after each run, and replaceable items such as gaskets and lubricants are renewed if deemed necessary by the chemist requesting work and the engineer in charge. This laboratory has been in constant use since its installation in 1949. As each preparation is of a different nature and since several batches may be required to complete an order, t'he operation of the laboratory follows a fluid pattern. Ordinarily, the research chemist submits his directions to the chemical engineer responsible for operation of the laboratory. After a critical inspection for possible danger points such as high heat of reaction, the engineer scales up the preparation. Regular pilot plant operators then carry out the latter's directions, often a i t h the research chemist observing, consulting, and working up the catch samples. Because of the size of the equipment in the laborat'org, it vas placed under the jurisdiction of t,he Pilot Plant Division, and it is from this division that the skilled technicians are drawn for the operation of the equipment. In addition, a technical man is ordinarily assigned to each preparation. To illustrate the use of the laboratory it is of interest that 61 preparat,ions were carried out during the past year. Of these, 39 were new, 83% of which were successful; 22 were repeats, 91% being successful. Estimated time spent in this work during this last pear has heen 2.5 man-years. Although these results are most sabisfying, a word of caution as t o the use of such a versatile setup is needed. Engineering design data on critical factors such as contacting of reagents, reaction rates, heat exchange, corrosion, and fluid flow characteristics are generally not available from such a laborat'ory. Rough estimates may be made, but it is usually- necessary to operate a specially designed pilot unit for each new product selected for large scale development. Sometimes, the availability of large samples of a new chemical leads to the assumption that process information is well in hand and that plant design is the next step. This is generally an unsafe assumption. Some types of processing ('bugs" may come to light in the large scale samples laboratory; however, it cannot fulfill the purposes of a tailor-made pilot plant, except t o supply quantities of new chemicals for testing and evaluation Lvork. ACKR'OWLEDGMENT
The engineering details of this laborat,ory were planned and its construction was supervised by Donald W. Meyers of the Pilot Plant Division, under the general guidance of K. C. Laughlin, manager of that division. Since all other division manager$ m r e consulted, the large scale samples laboratory incorporates the collcctive experience of thc entire Hcrculcs Experiment Station. RECEITED May 6,1951.
