Reactor adsorber

Guilleminot, J.J., Meunier, F. and Paklc2a, J., Heat and mass transfer in a non-isothermal fixed bed solid adsorbent reactor a uniform-pressure non-uniform temperature case. International Journal of Heat and Mass Transfer, 1987, 30(8), 1595 1606. 

At the cold start of the engine the catalyst is not able to oxidize carbon monoxide and hydrocarbons present in the exhaust. Therefore, zeolites are added into y-Al203-based catalytic washcoat for HC adsorption at low temperatures, resulting in an integrated adsorber-reactor system (Jirat et al., 2001 Kryl et al., 2005). For optimum operation of such a system, the consecutive HC desorption induced by increasing temperature should not occur earlier than the catalyst light-off. 

H. Adsorber Reactor for Transient Studies at Millisecond Rates... 

Stolk and Syverson (1978) described an absorber-reactor that is capable of carrying out transient studies at millisecond rates. They presented a high-temperature, high-speed constant volume adsorber reactor that is capable of measuring adsorption rate in the presence of a chemical reaction. The reactor provides rapid gas-solid contact in a constant-volume cell with transient rates for temperature and pressure measurements in the millisecond region. Using... 

Adsorber reactors to measure adsorption at reaction conditions have also been reported by Winfield (1953), Macarus and Syverson (1966), Edwards (1961), Keller (1962), and Haering and Syverson (1974). 

If needed, gas effluent could be sent to a mercury absorber purge gas reactor where mercury is adsorbed on the trapping mass before release of the gas at battery limits. Liquid effluent is sent to the mercury adsorber reactor where free mercury is adsorbed and the resulting treated product is routed to the downstream unit... 

Figure 6.12 shows the most commonly proposed fluidised bed design where two fluidised beds are used with a first as the adsorber/reactor for carrying out the SERF process and a second fluidised bed for regenerating the spent sorbent [36]. 

The description in the literature of early gas desulphurization processes that utilize zeolites does not mention duly the formation of COS during the removal of H2S, if CO2 is present in the feed gas, except in a few cases, e.g., ref. [20,28,65]. Since modern desulphurization plants work in accordance with the same principles and utilize identical zeolite types, the COS formation reaction may have strong implications for the currently employed processes for desulphurization of gases by means of those sorbents. Therefore, it is necessary to investigate (i) the COS formation as dependence on the zeolite type, the type and content of cations in the sorbent, the concentration and contact time of reactants with the sorbent, the temperature and the conditions of co-adsorption (ii) the mechanism of that reaction on the sorbent with specific emphasis on its sorption and catalytic properties and (iii) to develop a mathematical model to simulate dynamic processes that proceed in adsorbers/reactors of technical dimension. This investigation should lead to novel formulations of modified zeolite sorbents and to alternatives with regard to operating conditions of sorption plants with the purpose of either minimization or maximization of the formation of COS. 

The role of adsorption in heterogeneous catalysis is not easily evaluated because of the simultaneous occurrence of adsorption and reaction and the difficulty of measuring surface concentrations of reacting species on the catalyst at these conditions. Exploratory research directed toward devising a method for studying adsorption in gas-solid systems by means of a batch adsorber-reactor has been underway in this laboratory for several years. 

Adsorption measurements at reaction conditions have been coupled with fixed bed kinetic data to arrive at simple kinetic models with one or two adjustable parameters (2 and 6). In recent work ( ) the adsorber-reactor has been used as a batch reactor for obtaining kinetic data up to high conversions in addition to its use as an adsorber. 

The design and experimental results for some typical applications of a high temperature, high speed constant volume adsorber-reactor have been presented. Preliminary experiments indicate that adsorption studies can provide a better insight into transport mechanisms and the role of adsorption in heterogeneous catalysis thereby assisting the development of improved kinetic models for these complex reactions. 

To prevent such release, off gases are treated in Charcoal Delay Systems, which delay the release of xenon and krypton, and other radioactive gases, such as iodine and methyl iodide, until sufficient time has elapsed for the short-Hved radioactivity to decay. The delay time is increased by increasing the mass of adsorbent and by lowering the temperature and humidity for a boiling water reactor (BWR), a typical system containing 211 of activated carbon operated at 255 K, at 500 K dewpoint, and 101 kPa (15 psia) would provide about 42 days holdup for xenon and 1.8 days holdup for krypton (88). Humidity reduction is typically provided by a combination of a cooler-condenser and a molecular sieve adsorbent bed. 

The process options reflect the broad range of compositions and gas volumes that must be processed. Both batch processes and continuous processes are used. Batch processes are used when the daily production of sulfur is small and of the order of 10 kg. When the daily sulfur production is higher, of the order of 45 kg, continuous processes are usually more economical. Using batch processes, regeneration of the absorbant or adsorbant is carried out in the primary reactor. Using continuous processes, absorption of the acid gases occurs in one vessel and acid gas recovery and solvent regeneration occur in a separate reactor. 

After the SO converter has stabilized, the 6—7% SO gas stream can be further diluted with dry air, I, to provide the SO reaction gas at a prescribed concentration, ca 4 vol % for LAB sulfonation and ca 2.5% for alcohol ethoxylate sulfation. The molten sulfur is accurately measured and controlled by mass flow meters. The organic feedstock is also accurately controlled by mass flow meters and a variable speed-driven gear pump. The high velocity SO reaction gas and organic feedstock are introduced into the top of the sulfonation reactor,, in cocurrent downward flow where the reaction product and gas are separated in a cyclone separator, K, then pumped to a cooler, L, and circulated back into a quench cooling reservoir at the base of the reactor, unique to Chemithon concentric reactor systems. The gas stream from the cyclone separator, M, is sent to an electrostatic precipitator (ESP), N, which removes entrained acidic organics, and then sent to the packed tower, H, where SO2 and any SO traces are adsorbed in a dilute NaOH solution and finally vented, O. Even a 99% conversion of SO2 to SO contributes ca 500 ppm SO2 to the effluent gas. 

Only recently has a mechanism been proposed for the copper-cataly2ed reaction that is completely satisfactory (58). It had been known for many years that a small amount of carbon dioxide in the feed to the reactor is necessary for optimum yield, but most workers in the field beHeved that the main reaction in the formation of methanol was the hydrogenation of carbon monoxide. Now, convincing evidence has been assembled to indicate that methanol is actually formed with >99% selectivity by the reaction of dissociated, adsorbed hydrogen and carbon dioxide on the metallic copper surface in two steps ... 

The H2S comes out with the reactor products, goes through the product-recovery system of the FCCU, and eventually goes to a Claus plant for sulfur recovery. The metal oxide adsorbent recirculates with the spent cracking catalyst back to the regenerator for the next SO adsorption cycle. 

Membrane reactors, where the enzyme is adsorbed or kept in solution on one side of an ultrafHtration membrane, provides a form of immobilized enzyme and the possibiHty of product separation. 

The effect of increasing pressure is to move the average hydrocarbon content towards the heavier species, but increasing temperature seems to favour the production of lighter species. The final proportions are also determined by the state of the catalyst, and the physical anangement of tire reactor. The formation of the oxygenated compounds could also involve reactions between the H2O content of tire gas in the form of adsorbed OH radicals and hydrocarbon radicals since the production of these molecules is also well beyond the thermodynamic expectation. 

To open the reactor for inspecting or changing the catalyst, extreme caution must be used. A used catalyst is completely reduced and has some methanol and other combustibles adsorbed on the surface. The used catalyst can heat up when exposed to air and even ignite. A catalyst overheated this way is not useful for further studies and a burned-down laboratory is not useful at all. 

The previous volume measurement was done by methane because this does not react and does not even adsorb on the catalyst. If it did, the additional adsorbed quantity would make the volume look larger. This is the basis for measurement of chemisorption. In this experiment pure methane flow is replaced (at t = 0) with methane that contains C = Co hydrogen. The hydrogen content of the reactor volume—and with it the discharge hydrogen concentration— increases over time. At time t - t2 the hydrogen concentration is C = C2. The calculation used before will apply here, but the total calculated volume now includes the chemisorbed quantity. 

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