Kinetics of continuous hydrogen reduction of copper from a sulfate solution
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pumped feed at a preset pressure to the top of the reactor. Hydrogen was introduced from a gas cylinder through a DP cell, F-l, at the lower end of the reactor by means of a sparger. Thus, the upward flowing hydrogen contacted the downward flowing solution. Nitrogen was used for pre-startup and post-run purging of the reactor. Reactor System R-1 is a modified plug-flow, tubular reactor made of titanium, 31 mm I D and 152 mm long. Swagelok fittings were used for all high pressure connections. Heaters consisting of resistance wire wrapped around the reactor and sandwiched between the reactor and the outer insulation provided the thermal energy required to maintain the operating conditions of the reactor. Nine thermocouples at predetermined intervals were provided along the length of the reactor to measure the skin temperature. The temperature of the reactor was controlled by variacs on the electrical resistance heaters. The hydrogen sparger provided adequate agitation and surface area required for reduction in the reactor. Reactor pressure inside the reactor was controlled by valving on the high pressure, gas-liquid separator. Product Separation System The reaction products from the reactor were then cooled by a water jacket attached to the bottom of the reactor and were collected in the liquid-solid separator, S-1. The depleted solution, after passing through a bag filter in the separator, was removed at a constant rate; the solid product was collected in the filter bag. Gaseous products, mostly hydrogen, were passed through a demister in the upper portion of the high pressure gas-liquid separator, S-2, and were then depressurized through valve, PCV-1. The pressure control system for the high pressure gas-liquid separator served as the pressure control for the entire system. The
ISSN 0360-2141/81/0911-0565500.75/0 9 1981 AMERICAN SOCIETY FOR METALS AND VOLUME 12B, SEPTEMBER 1981--565 THE METALLURGICAL SOCIETY OF AIME
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Fig. l--Schematic diagram of CHR process.
DRAIN
,GAS/LIQUID
"~-REACTOR FEEDTANK
P-I CIRCULATI PUMP NG ~ HIGH ~ PRESSURE PUMP
-1 ~K._ F
L
~SEPARaTOR. S2
............
--,
LIQUID/SOLID SEPARATOR, S1
N2 I
depressurized gases were then measured at near atmospheric conditions in a wet test meter, F-2, and were then vented to the atmosphere.
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Residence Time
9 II min 80 9 15rain 9 20 m J
RESULTS Experments were made over the temperature range, 120 to 230 ~ and residence times between 10 and 30 minutes, for feed solutions having initial pH values from 1.4 to 4.4, at a pressure of either 3536 or 2850 kPa, and for a feed concentration of 12 g (Cu + +)/1. (The pH of a solution of copper sulfate in water ordinarily falls in the range of 3.6 to 4.4. By adding sulfuric acid the pH of the feed solution could be lowered to the desired value. Also, in a few of the runs the feed concentration was changed from 12 g (Cu + +)/1 to 22 in order to validate that concentration had a negligible effect). To prevent precipitation of the basic copper sulfate at elevated temperatur
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