Poisoning batch reactor

The main advantages of a batch reactor are as follows. It is simple and allows rapid measurements. Many experiments can be performed in a short period of time. It is convenient when using pure, expensive, corrosive, or high boiling temperature chemicals. Its use is recommended if the catalyst is sensitive to traces of poisons since there is no accumulation effect. In principle, by varying the stirring conditions it is possible to investigate the influence of heat and mass transfer processes. 

Catalyst Poisoning ia. a Constant Volume Batch Reactor... 

Example CDUl-3 Decay in a Straight-Through Reactor Example CD 10-4 Catalyst Poisoning in a Batch Reactor Liviiig Example Problems... 

The possible reason for the deactivation of the Pd surface could be poisoning by S, Cl and P which are present in the feed, blockage, and coke formation. XPS results unequivocally demonstrated the presence of Cl in the spent catalyst. For the first order kinetics in a batch reactor the following equation holds... 

Alkaloid-free Pt/a-alumina showed high activity for pyruvate hydrogenation, 100% conversion being initially achieved (Figure 1). This is a notable result, because reaction in the liquid phase in a stirred batch reactor is normally slow, the rate reduces with time in a manner indicating a self-poisoned reaction, and 100% conversion is seldom achieved. 

Rorvik et al. studied unsupported Nafion for isobutane/1-butene alkylation in a stirred liquid phase batch reactor [12]. The production of trimethylpentanes (the most desirable alkylate product) was shown to cease within 30 minutes of operation. More recently, silica-supported Nafion was used to catalyze the same reaction [13]. Once again, rapid deactivation with respect to trimethylpentane formation was observed. It was hypothesized that the strongest acid sites—the most active for alkylation—are also the first to be poisoned. 

It was found during studies of ammonia synthesis on iron that the incorporation of a condenser downstream of the sample valve in the external circulation loop of the HPLP apparatus (Fig. 7), enabled the system to be run as a flow rather than a batch reactor. This is true for any reaction system where the reactants are more volatile than the products, since the condenser temperature can be adjusted to trap the products almost exclusively, allowing a nearly pure stream of reactants to impinge on the catalyst. In the case of ammonia synthesis, (where, next to the product, nitrogen at a partial pressure of 5 atm was the most condensable species) a slurry of isopentane (— 159.9 °C) was found to be the ideal condenser medium. During a study of rhenium-catalyzed ammonia synthesis the isopentane condenser was switched in periodically to reduce the ammonia partial pressure to below that at which it appeared to poison the catalyst. In this way, the rhenium was able to produce ammonia in excess of the amount usually leading to poisoning. 

Acidic contaminants are poisonous to the alcoholysis catalysts and must be avoided. If the oil has a high acid number, or there are high acidity residues left in the reactor from the previous batch, such as sublimed phthaUc anhydride condensed under the dome of the reactor, the reaction can be severely retarded. A longer batch time or additional amount of catalyst is then required. Both are undesirable. 

Provide for addition of diluent, poison, or inhibitor directly to reactor. Provide for automatic or manual actuation of bottom discharge valve to drop batch into a dump tank with diluent, poison or inhibitor, or to an emergency containment area. 

When the medium becomes acid, at 45-48 °C reactor 1 receives a calculated amount of poisonous methanol from batch box 6 at such speed that the temperature in the reactor does not exceed 50°C. Then, at 67-75 °C the released methylacetate is sent from reactor 1 through cooler 7 into neutraliser 8 with an agitator. 

We also note that the process of decay in catalytic cracking has been amply demonstrated(l)(2)(3) to be a function of the time of exposure of the catalyst to the reactants i.e. of the time on stream. Such time-dependent behaviour indicates that the kinetics of the process of catalyst decay are the same as those to be expected in a batch reaction. On reflection, it is obvious that the situation of the catalyst charge in a steady-state reactor is in fact that of a batch of reactant (the catalyst) undergoing a chemical process (catalyst decay) as a function of the time on stream i.e. the time it spends at reaction conditions - at reaction temperature and in the presence of an atmosphere of feed, products and potential poisons. 

To point to the importance of using improved methods of fuel and poison management, we shall discuss qualitatively the multiple drawbacks of the simplest method, which is batch irradiation of fuel initially uniform in composition, with spatially uniform distribution of boron control poison and with complete replacement of fuel at the end of its operating life. An example of this would be a PWR charged with fuel of uniform enrichment containing 4 percent and 96 percent and controlled by adjusting the concentration of boric acid dissolved in the water coolant to keep the reactor just critical at the desired power level. When this reactor starts operation, the compositions of fuel and poison are uniform throughout the core, and the flux and power density distribution are very nonuniform. 

This figure illustrates immediately one of the disadvantages of batch fuel management. The power density, which is proportional to the product of the neutron flux and the fissile material concentration, is just as nonuniform as the neutron flux. If the local power density must be kept below some safe upper limit, to keep from overheating the fuel or cladding, only the fuel at the center of the reactor can be allowed to reach this power density, and fuel at all other points wiU be operating at much lower output. In a typical uniformly fueled and poisoned water-moderated reactor, the ratio of peak to average power density is over 3, so that the reactor puts out only one-third as much heat as it could if the power density were uniform. 

Long-term (>1000 h) tests were performed in a separate reactor equipped with a sohd-state on-line hydrogen sensor and infrared carbon monoxide and carbon dioxide detectors. Batch sampling was performed at the exit stream. This system allowed us to determine the durabihty of the autothermal reforming catalyst and to determine if there are any long-term problems (poisoning, coking) caused by the fuel components. 

Because of such effects, spent uranium fuel elements from PWR, BWR, HWR, GCR and FBR differ in composition both from each other and between fuel batches from the same reactor. Furthermore, the composition differs betwe pins in the same fuel elemrat and for each pin also along its Iragth, especially when initial burnable poison concentration and enrichm t is graded along pins. The differraice is not so large that very different fuel... 

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