Contact time autoclaves

An example of the data, broken down into the 13 product groups, calculated tom the distillation and GC analysis of the hydrocracked liquids from CoMo-catalysed experiments is shown in Table II. It can be seen that the distribution of each of the contacts is similar, reflecting no dependence on repeat contact, even in the case of the first contaa which used tosh catalyst. This situation was generally observed for the other catalysts used and a summary of the r ts for the four catalysts is shown in Table III. The results for ZnW could be interpreted as a gradual decrease in conversion to material bpt <260 C or <275°C. However, this interpretation would depend highly on the reliability of the result for the fifth contact, the two runs of which were carried out on the same autoclave rather than one on each autoclave. The discussion further in the text does indicate that, at shorter contact times, conversions can be dependent upon the autoclave used, and the low value for this fifth contact probably results tom this dependence rather than a dependence on contact Hence it was concluded that, for all the catalysts, conversions to the various bpt materials were independent of repeat contact. 

The reactor was stirred at 1600 RFM, Intimately mixing the acid and hydrocarbon phases. Contact times (half the reactor volume divided by the hydrocarbon feed rate) ranged from 0.3 to 3.0 minutes. The temperature Inside the reactor was controlled by passing water or antifreeze solution from a controlled temperature reservoir through the jacket of the autoclave. The reaction temperature was monitored by a sheathed thermocouple Inserted Into the autoclave just below the stirrer. A stream of acid-hydrocarbon emulsion passed continuously from the autoclave to the settler. The acid catalyst settled to the bottom and returned to the reactor by gravity flow. The hydrocarbon product passed out the top of the settler through a pressure control valve which maintained the reactor at 200 pslg. 

Nasr-El-Din et al. (2002) have also investigated the corrosion inhibition of some aldehyde-based sulfide-snppression chemicals on steel conpons in a corrosion autoclave in acidic media. Formaldehyde was mentioned in the research, bnt other aldehyde-based chemicals were only tagged Aldehyde A, Aldehyde and so forth. Combinations of some of these aldehyde-based chemicals were also investigated. They condncted the tests at 0.5 mol% H2S with varying concentrations of sulfide scavengers at ambient, 150°F, and 275°F conditions of temperatures and at pressures of 3000 and 5000 psi. All the corrosion tests were completed at 4 h contact time. They concluded that all the chemicals are effective to some extent in controlling H2S and in corrosion inhibition. 

Decontamination of wastes by autoclaving can be somewhat tricky, since the efficacy of this technique relies on the penetration of steam into every portion of the load (242), and the contact time (the time that the steam contacts all portions of the load) and the autoclave set time (the time set on the autoclave timer) are rarely equal. In fact, for large loads, it has been demonstrated that complete steam contact times can lag autoclave set times by a factor of four or more (254), resulting in incomplete sterility or decontamination. In all cases, the manufacturer s recommendations for the operation of the steam autoclave should be followed. 

In a continuous reactor, particularly of the trickle bed type, intimate contact between the coal liquid and the catalyst will be maintained throughout the pass of the liquid feed. In an autoclave, particularly of the stirred design, the contact between the liquid and the catalyst will not be as intimate. The action of the stirrer will produce a centrifugal force which will tend to throw the liquid away from the catalyst surface. Consequently, it can be visualised that less strongly adsoibed molecules will spend a shorter time at the catalyst surface so that reaction rates and mechanisms could be very different from those observed in continuous reactor studies. In addition, steady state conditions can be readily investigated in a continuous reactor, whereas for a single contact in an autoclave, steady state conditions may not have been established and changes in catalyst activity will become more relevant. 

For these investigations the metallic samples were fixed in cylindrical autoclaves and installed in an insulated block which was thermostated by electric heating. The autoclaves were kept in a continuous motion throughout the experiment. Thereby a steady contact of the material samples with the gas as well as the liquid phase of the reaction fluid could be maintained. After an operation time of two or three weeks at constant temperature the autoclaves were opened, the samples were weighed, visually examined and a part of them analyzed. The residual samples were put back in the autoclaves for further treatment. 

Plasticised PVC was surface modified by nucleophilic substitution of the chlorine atoms of PVC by sulphide ions in aqueous media in the presence of a phase-transfer catalyst. The modified PVC was sterilised by steam autoclaving and gamma irradiation and subjected to plasticiser extraction. Surfaces were evaluated by contact angle measurements, SEM, cell culture studies, haemolysis assay and whole-blood clotting time measurements. Mechanical properties were examined. 31 refs. 

Catalysts such as zinc oxide or Twitchell reagent (alkylaryl sulfonic acids) may be used which increase the rate of reaction but not the extent of hydrolysis. Operations may be carried out batchwise at atmospheric pressure and 212°F. with the Twitchell catalyst, or in autoclaves at high pressures up to 450°F. with or without catalyst. Complete miscibility with water may occur at temperatures about 550 to 650 F., depending upon the fat. Continuous countercurrent contact of the water and oil at temperatures below complete miscibility increases the percentage splitting possible, to an extent depending merely upon the time of contacting. 

In the system shown in Fig. 2.3, blended oils and fats feedstocks are continuously and accurately metered into a pressurized, heated vessel, commonly referred to as an autoclave, along with the appropriate amount of caustic, water, and salt. The concentrations of these ingredients are adjusted to yield a mixture of neat soap and a lye phase. At the temperatures ( 120°C) and pressiues ( 200 kPa), the saponification reaction proceeds quickly (<30 min). A recirculation system ensures a residual level of soap in the autoclave to improve contact between the oil and water phases and provides additional mixing. After a relatively short resident time in the autoclave, the neat soap and lye phase reaction blend is pumped into a cooling mixer where the saponification reaction is completed and the reaction product... 

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