Flexibility in Pilot Plant Operations H. 6.H. COOPER’ A N D W. C . MCINTIRE CALCO CHEMICAL DIVISION, AMERICAN C Y A N A M I D GO., 6 O U N D B R O O K , N. J.
A
BOUT six years ago, the Calco Chemical Division of the
American Cyanamid Co. took the initial step toward centralizing the pilot plant operations being carried on in the various manufacturing areas. The major goal in centralization was t o ease and hasten t h e passage of a product or process from the laboratory t o commercial plant operation. I n a centrally located pilot plant i t was expected t h a t maximum efficiency would be obtained with regard t o equipment, manpower, time, and cost. Duplication of facilities and equipment in several plant areas would be eliminated, fuller use of equipment by all groups would be ensured, and a wider range of equipment would be made available for all investigations. Pilot plants are usually designed t o meet the demands of a specific industry. At the Calco Chemical Division of the American Cyanamid Co. the Central Pilot Plant is used by an organization producing about 1000 different synthetic organic chemicalsmainly intermediates, dyes, pigments, textile resins, pharmaceuticals, and rubber chemicals. The majority of these chemical products are produced in batch-type reactors, followed by various methods of isolation from solution, after which they are dried, ground, blended, and packaged. Experience in making a large number of different products has indicated t h a t the principal functions of the Central Pilot Plant normally fall within one of the following classifications-preparation of test quantities of new products; development of new processes; improvement of old processes; study of process variables; study of engineering variables ; development of improved equipment; testing materials of construction; obtaining scale-up data for plant design purposes; or producing on a semiworks basis during a market development period. The Central Pilot Plant supplies equipment for investigations by the research, development, and engineering departments. T h e functions performed and the processes and operations most frequently encountered are listed in Table I.
Table I .
Pilot P l a n t Functions
I.
Preparations laboratory (5- to 10-pound batches, research) 11. Pilot plant equipment (60- t o 100-pound batches, development) 111. Unit operations equipment (chemical engineering) IV. Corrosion testing equipment (metallurgical engineering) Classification of Work Processes Operations Sulfonation Agitation Nitration Crystallization Halogenation Heat transfer Condensation Distillation Oxidation Extraction Reduction Filtering Amination Centrifuging Diazotbation Dryinn Grindl’ng Coupling Hydrogenation Fluidization Alkylation Classification
PLAN O F BUILDING
The Central Pilot Plant started operation in 1945 in a steel and concrete building having a floor area of about 12,000 square feet (11.5 X 108 feet) with a monitor-type roof over the center two bays and with a fixed balcony a t a height of 13 feet along the two outside bays. The building plan is shown in Figure 1. 1 Present address, Colgate-Palmolive-Peet Co., Research and Development Laboratories Jersey City, N. 3.
2814
T h e Central Pilot P l a n t of t h e Calco Chemical Division of t h e American Cyanamid Co. a t Bound Brook, N. J., is described. Emphasis i s placed on t h e use of flexibly installed equipment since t h i s provides for t h e quickest passage of a number of different products or processes f r o m t h e laboratory t o t h e plant. T h e features of building, equipment location, materials handling, reaction units, auxiliary equipment, and services t h a t contribute t o m a x i m u m flexibility are discussed.
Space for offices, laboratories, and shops is provided on the main floor under the balconies. The four center bays, with 34 feet of headroom in the middle, are used for pilot plant equipment. A portable elevator serves the tools and platforms up t o a level of 20 feet above the main floor. The outside balconies are reserved for idle equipment storage. This first building was outgrown in about six years’ time and operations have recently started in a secorld new building having a floor area of about 11,000 square feet (78 X 144 feet) with a center skylight and with a coucrete balcony at a height of 20 feet along the two outside Days, as shown in Figure 2. Operation of the first building had indicated a considerable number of improvements t h a t would add t o the flexibility of the over-all pilot plant operations and, wherever possible, these were incorporated in t h e latter. I n the new building the upper floor is of steel-concrete construction with a waterproof membrane and is designed for a 300pound-per-square-foot floor loading, since this floor serves for the major raw materials handling. It is served by a n enclosed elevator. With the upper floor at the 20-foot level, it is possible to have three levels of processing equipment with adequate headroom a t each Ievel. The intermediate floors and operating platforms are installed wherever needed and are supported from the ground floor, leaving as much free area as possible between and around units. Most drowning tanks and secondary reactors are located at the 10-foot level under the main reaction vessels. I n the open area below the top floor i t is possible t o make temporary installations of auxiliary tanks and special isolation equipment-e.g., different types of filters and centrifuges-as required by the particular process. I n the new building removable corrugated Transite sheeting is used for all siding not taken up by windows. Natural lighting is provided by windows t o the extent of approximately 80% of the side-wall area. This type of construction permits ready access t o the outside when or if i t is desirable to set up equipment outdoors along the sides of the building. Typical of the latter are situations where hazards or difficult ventilation problems are involved. For this type of operation a concrete apron with sewer drainage is provided on one side of the building. Two main entrance doors lead into enclosed fireproof stairwells t h a t provide safety exits a t opposite ends of the building. Operating stairways to intermediate platforms are also installed whereever required. Ready access t o all operating units on the upper floor is provided by x runway extending around the open well a t the center
INDUSTRIAL AND ENGINEERING CHEMISTRY
VOl. 44, No. l a
Multiple-Use Plants
December 1952
INDUSTRIAL A N D ENGINEERING CHEMISTRY
2815
m STEAM
4
f CONDENSE
IO
7:R.C. TRAY
DRYER
m
Figure 3.
Typical Pilot P l a n t U n i t w i t h Services
of the building. The open well provides ventilation and light from the center skylight and also permits the installation of tall, continuous-type equipment wherever needed. The main floor beams at each vertical column are extended across the open well. These may later serve as support for platforms and equipment. MATERIALS HANDLING
The basic philosophy of materials handling has been t h a t wherever possible gravity flow is used. Raw materials are delivered a t an unloading platform and receiving area on the first floor, covering one full bay of the building. Drums, cartons, and bags of solids and smaller quantities of liquid materials t h a t can be handled in drums or carboys are transported to the upper floor by means of the elevator. Liquid ranT materials used in bulk quantities (acids, 50% caustic soda, etc.) are transported t o the building in 1000-gallon tanks by Dempster-Dumpster pickup trucks. These tanks are placed on an outside apron and are connected t o pumps for transporting their contents t o a weigh-station located in the third-floor operating area. An hydraulic-lift truck with portable weigh-tanks is employed on thetop floor for delivery of the solutions from the weigh-station to the reaction kettles. Nost of the reactors or processing vessels are charged directly from the top floor. Tanks and reactors on the intermediate or lower floors are usually charged through chutes, piping, or flexible hose leading down from the top floor. I n the typical case, reactions are started on the top floor and flow by gravity from one reactor or drowning vessel to another on the lower floors until the product is ready for isolation. 2816
Finished products, ready for removal from the building, normally end up on the first floor. The need for good housekeeping and for safety of operations is very important in pilot plant work. Reviews are regularly made by the safety department on all operating procedures. Refcrence is made t o t h e bulletins of the Alanufacturing Chemists Association on handling of hazardous chemicals and to thc Underwiters Laboratories classification of flammable solvent? before a new process is taken into the pilot plant. Flammablr solvents are stored outside with only the needed supply being taken into the building a t the time a kettle is charged. REACTION VESSELS AND T H E I R SERVICES
Jacketed or coil-heated kettles are employed for sulfonations, nitrations, condensations, chlorination, oxidationss, etc. These reactors are usually installed in permanent positions on a n upper floor level, with fixed service connections for power, water, air, vacuum, steam, etc. A typical flow diagram is shown in Figure 3, where feed tanks, condenser, receiver, vent lines, safety disk, temperature control, exhaust connections, and discharge outlet are shown. These reactors vary from 10 t o 300 gallons in size and are of steel, stainless steel, and enamel-lined steel, in order t o meet the various types of corrosive conditions that are usually encountered. I n general, enamel-lined kettles are most useful for halogenations or for reactions in dilute acid at a moderate temperature range (up to 200" C.), whereas the steel and stainless steel reactors are most useful for nitrations, sulfonations, etc., in concentrated acid conditions or for alkaline reactions
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 12
Multiple-Use Plants under a wide range of temperature conditions. Figure 4 showil the receiving tanks located beneath a 50-gallon reactor unit. Ten-gallon reaction kettles on the balcony and the receiving tanks for these kettles are shown in the upper and lower parts of Figure 5, respectively. Some kettles are heated with either hot water or steam and are cooled with circulating water or brine (0' C. or lower), others are heated with circulating oil up to about 225' C., and still others with electricity or with Dowtherm vapor or liquid to a temperature as high as 350' C. Explosionproof motors and starters are used throughout the building. Flame arresters are provided on the main vent openings above the roof and frangible safety disks are installed a t the kettles on secondary vent connections. Exhaust ducts with Flexaust hood connections are supplied for venting the charging ports t o the kettles. Recording controllers are supplied for the main reaction temperatures, but portable multipoint recorders are also used to provide additional measurements, such as those in and out of jackets and condensers. Flowmeters of varying sizes are R U ~ plied when needed t o indicate gas or liquid flow rates t o the kettles. I n cases where a process is better suited t o continuous operation, reactors are set up in series or continuous pipe-type reactors are provided. Feed tanks and proportioning pumps are provided for controlling feed rates of the reactants. Frequently, one or several of the reaction vessels in the batch units may be used as feed tanks or product discharge tanks. In general, it has been found that there is no universal continuous reactor and t h a t it is not possible to obtain the same degree of flexibility with continuous operation as with batch operation. Equipment, instrumentation, and controls for continuous operations must be considered with special reference t o the particular product being made.
Figure 4.
Receiving Tanks and Filter for 50-Gallon Units
FIXED AUXILIARY EQUIPMENT
Drowning tanks of wood, Haveg, lead-lined steel, or stainless steel are provided in a fixed position under the larger reaction kettles. These tanks are usually about five t o ten times the capacity of t h e reaction vessels. Filter presses range in size from 12 t o 30 inches and are made of wood, cast iron, or stainless steel. Most of the larger presses are located in fixed positions on the top floor, the philosophy being, as mentioned earlier, t h a t processes run downhill through the kettles and tanks by gravity flow to the bottom floor level. The slurry of finished product is then pumped back up again t o the press a t the top floor level, with any bleed being recycled t o the holding tank below. I n similar fashion, the drying, grinding, and blending operations start again a t the top and run by gravity to the packaging station on the first floor. Drying is done on enamel trays in forced convection hot-air dryers. These dryers are designed with air intake through filters and unit
F i g u r e % Reaction Kettles and Auxiliary Equipm e n t (Upper) and Portable Tanks and Filter P r e s s ( L o w e r ) f o r 10Gallon Units
December 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY
2817
earlier operations. This includes small kettles, tanks, condensers, motors, agitators, drives, instruments, and special fittings. These are stored on the balcony of the older pilot plant building, where about 3500 square feet of floor area are available. Explosionproof electrical receptacles for both 110 and 220 volts are placed a t numerous locations throughout the building. Portable small motors (up to 2 horsepower) are fitted with explosionproof plugs and Super-service cord connections. This permits ready movement and hookup of portable tools from one location to another, I n the Central Pilot Plant, equipment is provided for unit operational studies on distillation, extraction, agitation, grinding, filtering, centrifuging, etc., with several different types of units being available for each operation. Typical units to be found are: a 3-inch adiabatic stainless steel column with removable screen plates or conventional packing, equipped for batch and continuous distillation; a 2-inch liquid-liquid extraction column; a 1 X 1 foot rotary vacuum filter; a 6 X 8 inch stainless steel double-drum dryer; a horizontal rotary hot-air dryer; a tablemodel spray dryer; 12- and 18-inch stainless steel basket-type centrifuges; a unit for agitation studies, etc. Chemical engineers make studies in this equipment to obtain scale-up data for plantsized installations. MECHANICAL SERVICES
Figure 6.
Portable Ceramic Suction Filter
Several of the 12- and 18-inch filter presses are mounted on casters so t h a t they can be used in different locations. I n some instances a pump and motor are mounted directly on the portable press base; Figure 6 shows a view of a portable ceramic suction filter. Flexible connections are frequently used between tanks, pumps, and presses. I n general, hose of rubber, neoprene, saran, or stainless steel is used. The filter press cloths used are cotton for most services, but frequently Vinyon or Orlon are used for strong acids and Vinyon or nylon for strong alkalies. A portable lift truck is used to move and elevate equipment and raw materials. This has contributed appreciably toward flexibility of operation. Another factor leading toqrard greater flexibility is the available stock of idle equipment, both new and that dismantled from
One of the real keys to flexibility in pilot plant operation is having adequate mechanical shops and staff available for quick changes of equipment and piping. The Central Pilot Plant has its own shop equipped with a lathe, drill press, grinder, pipe threading and cutting tools, and a storeroom containing various types of parts and fittings. The regular mechanical staff includes pipe fitters, mechanics, m-elders, electricians, and instrument mechanics. For other crafts, which are used somewhat less frequently, reliance is placed upon the Central Maintenance and Construction Department. CONCLUSION
Many factors contribute toward flexibility in pilot plant operations. These range from the building on through the reaction units themselves to the mechanical services t h a t are required, each contributing a very important portion t o the over-all flexibility. RECEIVED for review April 10, 1952.
ACCEPTEDSeptember 17, 1952.
Fifty-Gallon Reaction Kettle
2818
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 12'
