A SMALL-SCALE RECYCLE PUMP Small-scale experiments often requz~ethat special systems components be devised.
J . F. S H U L T Z
Commercially
available equ$ment must be inodzjed or otherwise adapted f o r a particular use. In this modification, new and useful pieces of equipment aye devised that can be further adapted for use in
systems small-scale pump was developed for recirculating gas in small reactor systems at pressures up to 500 p.s.i.g. The term "pump" here refers to the entire apparatus. I t is made up of a small atmospheric rotary pump, an electric motor, and necessary electrical connections. Since the system was to operate under pressure, the pump was housed in a pressure vessel. All of the component parts are commercially available. The apparatus has been used only in a system to study the kinetics of a catalytic reaction, the hydrogenation of carbon monoxide to methane on a nickel catalyst at 300 p.s.i.g. There are plans for using the apparatus to study the kinetics of the Fischer-Tropsch reaction, hydrogenation of carbon monoxide to hydrocarbons higher in molecular weight than methane. A heating coil was added to the original design to keep these materials in the vapor state. Performance charts are not available except for the gases currently under study. A capillary-type flowmeter in the recycle portion of the entire system is calibrated in cubic feet per hour at various pressures before starting operation. Normally the pump is operated under constant speed. Inflow is measured on the flowmeter and controlled by a needle valve. Present limit of calibration for the pump is 400 p.s.i.g.,
AUTHOR J . F. Shultz i s Chemist-in-Chargt, Catalyst Section, Pittsburgh Coal Research Center, U . S.Bureau of Mines. T h e pump was designed by the Bureau's Engineering Design staff. Stanley 1Yazaruk is credited with developing the ideas and preparing the diagrammatic sketches. 34
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
maximum rating of the entire research system. Performance charts are available but anyone using such a system would have to make their own calibrations. The material of construction is carbon steel for the pump, except the heating coil which is aluminum. Choice of other materials could be made depending on the corrosiveness of the system being studied. The pump has been used continuously for six months without operating difficulties or maintenance. I n some experiments, total gas flow has been as high as 24 standard cubic feet per hour. System pressure has been maintained at 50, 100, 200, and 300 p.s.i.g. The diagrammatic sketch opposite shows the details of the pump and motor assembly. The pump is of rotary vane design and normally operates at atmospheric pressure. At 3450 r.p.m. its capacity is rated by the manufacturer at 0.35 cubic foot per minute at 10 pounds differential pressure. Because the pump bearings require no lubrication, long periods of operation without maintenance are possible. The motor is hp., 3350 r.p.m. constant speed. I t operates on continuous duty on 110 volts, 60 cycle current. For operation at pressures up to 500 p.s.i,g., the pump and motor are enclosed in a pressure vessel. The vessel closure seal is made by an O-ring, UNS No. 341. The vessel is a 4-inch diameter, Schedule 80 pipe, 12 inches long. During operation, gas enters the pressure vessel and flows over the motor, cooling it. The gas enters the pump through a heated coil. This coil prevents any normally solid hydrocarbons from condensing in the pump, Insulated, pressure-sealed electrical leads for both motor and the heater pass through the head of the pressure vessel. The rate at which gas flows through the pump is controlled by an external needle valve. This valve is operated to starve the pump. Temperature of the motor is maintained between 50" and 60' C . and the pump at 100" C. as measured on a thermocouple. Differential pressure across the pump while operating is only about 2 pounds. Working drawings of the assembly are available from the Bureau of Mines, 4800 Forbes St., Pittsburgh 13. Pa.
