The reduction of calcium sulfate to calcium sulfide with carbon monoxide was studied using various catalysts. Ferric oxide, stannous sulfate, and vanadium pentoxide were found to have a pronounced catalytic effect on the reduction reaction. The ferric oxide was the most active catalyst and resulted in about 97% reduction of the calcium sulfate in 45 min at 680°C when at the optimum concentration of about 9 wt %. The system at 660°C showed reproducible oscillations of SO4 content with time. In addition, calcium sulfide was found to autocatalytically favor its own rate of formation. A mechanism involving the formation of active carbon
any modification of the optimal working conditions; then, we have computed the maximal value of the economic criterion that could be reached by modification of the three remaining decision variables: preheater temperature output (t3), bypass Results are presented by means of curves; one can find in Vincent's thesis (1971) numerical values, along with results for other perturbations.Catalyst Activity Decay. The decay of the catalyst activity leads t o a modification of the mathematical expression for the reaction rate R(g,t). TT'hatever this modification, the work of optimization remains the same, our method not being based on the form of R. K e have chosen to simulate this decay by t h e simpler manner which consists of multiplying R by a coefficient a varying from 1 t o 0.5. Figure 3 shows that the economic criterion of the optimally designed sequence is very sensitive to catalyst decay; however, one ran maintain this criterion a t an acceptable level by modifying t3, and AS.Composition at Input. Reaction rate along the reactors depends on the composition of the feed mixture. Figure 4 shows the effect of a variation in the percentage of SOz.One can see that the adjustment of t3, Az, and A 3 is mostappreciable when the percentage of SO2 is decreasing (it has been supposed equal to 7.8 in this project).Total Flow Rate. T h e sequence of reactors has been optimized to produce 50 tons/day of sulfuric acid. Figure 5 shows the results obtained when the production varies from 25 to 75 tons 'day, with and without adjustment of t3, Al, and x3. ConclusionI n a preceding paper we showed that the optimal sequence of reactors was very sensitive to a small variation of preheating temperature (t3). In this paper, we have shown that this sequence is also very sensitive to other perturbations. Severtheless, our method, slightly modified, allows the engineer t o control the reactors to obtain the maximum of the economic criterion, in spite of these perturbations. The method can be implemented on a small process computer.The pure gas permeability coefficients of various polymeric materials to carbon monoxide and hydrogen were determined, and the most promising of these were tested as separation membranes using binary rnixtures of the gases. The effect of temperature, pressure, and feed composition on permeation rate and permeate compositions was determined. Polyimide, Dacron, Parylene C, and caprolactam films proved to be the most effective. Depending on permeator conditions, actual separation factors varying from 14 to about 70 and fluxes varying from 0.03 to 1.3 scfd/ft?were observed. The actual separation and flux were somewhat lower than would b e predicted on the basis of the pure gas studies, assuming Fick's law. All materials tested were selective for hydrogen. Mathematical models of the two limiting cases of ideal permeation stages-i.e., no-mix and perfect-mix stages-were formulated. These models used the experimental flux and permeate compositions which were determined as a function of feed composition for various temp...
Three commercially available films and a vinylidene fluoride film modified with sulfolene were tested for the separation of carbon dioxide from carbon dioxide, methane and water vapor mixtures. Flux and separation factor values were obtained over a temperature range from 23 to 90°C and a feed gas moisture content from 0.0 to 1.32%. A feed gas containing 60% carbon dioxide and 40% methane on a dry basis was used at an operating pressure of 2068 kPa. The commercially available films tested were cellulose acetate, polysulfone and polyethersulfone. All three films provided good separation. For example, the polysulfone film produced a permeate containing 96.0% carbon dioxide at room temperature and 0.12% water. Separation factor values for carbon dioxide ranged from 4.6 to 45.1. Flux values for the commercial films ranged from less than 10.E-05 to 1.9xl0E-03 cu cm(STP)/sq cm(sec). The sulfolene modified film also provided good separation. Separation factor values for carbon dioxide ranged from 9.6 to 33.6. Flux values ranged from 10.E-05 to 5.7xl0E-05 cu cm(STP)/sq cm(sec). Strong trends towards increasing flux and decreasing percentage of carbon dioxide in the permeate with increasing temperature were observed with all films. A trend towards decreasing percentage of carbon dioxide in the permeate with increasing water content was observed with cellulose acetate, polysulfone and polyethersulfone films. These films demonstrated a strong trend towards increasing flux with increasing water content at low levels of water content. As the feed stream approached saturation, gas flux tended to become constant or actually decrease. The sulfolene modified film tended towards constant or increasing percentage of carbon dioxide in the permeate with increasing water content. The flux tended to remain constant or decrease with increasing water content.
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