Reformer, isothermal

Thus in Fig. 5.22 the first outgassing at 25°C will have removed physisorbed water only, so that curve (1) is the isotherm of physical adsorption on the fully hydroxylated material. The 300°C outgassing, on the other hand, will have removed all the ligand water and the majority of the hydroxyl groups when isotherm (4) is determined, therefore, the Ti ions will chemisorb ligand water at low relative pressure, but the number of hydroxyl groups reformed will be very small. 

Thixotropy is a phenomenon that occurs frequently in dispersed systems. It is defined as a reversible, time-dependent decrease in viscosity at a constant shear rate. Generally, a dispersion that shows an isothermal gel-sol-gel transformation is a thixotropic material. The mechanism of thixotropy is the breakdown and reforming of the gel structure. 

The main unit is the catalytic primaiy process reactor for gross production, based on the ATR of biodiesel. After the primary step, secondary units for both the CO clean-up process and the simultaneous increase of the concentration are employed the content from the reformated gas can be increased through the water-gas shift (WGS) reaction by converting the CO with steam to CO and H. The high thermal shift (HTS) reactor is operating at 575-625 K followed by a low thermal shift (LTS) reactor operating at 475-535 K (Ruettinger et al., 2003). A preferential oxidation (PROX) step is required to completely remove the CO by oxidation to COj on a noble metal catalyst. The PROX reaction is assumed to take place in an isothermal bed reactor at 425 K after the last shift step (Rosso et al., 2004). 

Tanaka et al. reported that gasoline POX over Rh, Pt, and Pt-Rh is promoted by alkali (Li) and alkaline earth metals (Ba, Ca, K) supported on magnesium aluminate spinel. The catalysts were tested isothermally at 800°C at an air to fuel ratio of 5.1 and GHSV 50,000 h Li, Mg and MgLi promoters were added to Pt supported on MgAl204 spinel. All catalysts produced similar H2 and CO reformate concentrations of 23 and 25 vol%, respectively. There was a discernable difference in the carbon deposition. The unpromoted Pt catalyst showed carbon levels of 0.02 wt% carbon, where the alkali and alkaline earth promoted Pt catalysts had carbon levels of 0.01 wt%. 

Reaction rates for the start-of-cycle reforming system are described by pseudo-monomolecular rates of change of the 13 kinetic lumps. That is, the rates of change of the lumps are represented by first-order mass action kinetics with the same adsorption isotherm applicable to each reaction step. Following the same format as Eq. (4), steady-state material balances for the hydrocarbon lumps are derived for a plug-flow, fixed bed catalytic reformer. A nondissociation, Langmuir-Hinshelwood adsorption model is employed. Steady-state material balances written over a differential fractional catalyst volume dv are the following ... 

C5 - yield. Here r( is the selectivity time when the C5 - yield at v = 1 (the reactor outlet) is equal to the experimental value of C5 -. It is determined from Eq. (12), as discussed earlier. Integration of Eq. (15) requires that the selectivity kinetics be previously determined. For isothermal reforming reactions, combining Eq. (15) with Eq. (6) gives... 

To effectively determine the start-of-cycle reforming kinetics, a set of experimental isothermal data which covers a wide range of feed compositions and process conditions is needed. From these data, selectivity kinetics can be determined from Eq. (12). With the selectivity kinetics known, Eqs. (17) and (18a)-(18c) are used to determine the activity parameters. It is important to emphasize that the original definition of pseudomonomolecular kinetics allowed the transformation of a highly nonlinear problem [Eq. (5)] into two linear problems [Eqs. (12) and (15)]. Not only are the linear problems easier to solve, the results are more accurate since confounding between kinetic parameters is reduced. 

An isothermal, plug flow, fixed bed reforming pilot plant (shown in Fig. 14) was used to generate the kinetic data. The reactor was U shaped and contained roughly 70 ml of catalyst. Five sample taps were spaced along the reactor length to determine compositions over a wide range of catalyst contact times. The reactor assembly was immersed in a fluidized sand bath to maintain isothermal conditions. 

The reforming process model is designed to predict the performance of many reactor configurations. The model can be run in four modes, combining adiabatic or isothermal reactors with recycle or single-pass (no recycle)... 

The accuracy of KINPTR over a wide spectrum of conditions and feedstocks will be demonstrated in this section. KINPTR predictions will be compared to a variety of R16H start-of-cycle and aging data from pilot plant and commercial reformers. Pilot plant data were obtained in both adiabatic and isothermal reactors. These predictions required complete reforming... 

Fig. 27. Isothermal reforming composition profiles, at 782 K, 2620 kPa, C6- 461 K Arab Light.

The conversion of cyclohexanes to aromatics is a highly endothermic reaction (AH 50 kcal./mole) and occurs very readily over platinum-alumina catalyst at temperatures above about 350°C. At temperatures in the range 450-500°C., common in catalytic reforming, it is extremely difficult to avoid diffusional limitations and to maintain isothermal conditions. The importance of pore diffusion effects in the dehydrogenation of cyclohexane to benzene at temperatures above about 372°C. has been shown by Barnett et al. (B2). However, at temperatures below 372°C. these investigators concluded that pore diffusion did not limit the rate when using in, catalyst pellets. 

A short 1 m isothermal steam reformer tube was used for this test. The reformer (3) was run under the same operating conditions as reformer (2), but with a relatively large catalyst pellet of characteristic length 0.007619 to. For Plant (3) the exit methane conversion X, the CO2 yield X, and the equilibrium values Xe and Xe for methane and carbon dioxide, respectively, are as follows. 

Recuperation BASF "isothermal" process conventional primary steam reforming Degussa BMA process... 

Copper and aluminum are alternative metals for low-temperature processes such as alcohol reforming [22, 85] and gas purification. The higher heat conductivity of these metals (401 and 236 W m-1 K-1), respectively, compared with stainless steel (ca. 15 W nf1 KT1) makes them attractive, in case isothermal conditions are required, which may well be the case for evaporators or reactors with heat-exchanging capabilities. On the other hand, the efficiency of small-scale counter-flow heat... 

Assaf, E.M., Jesus, C.D.F. and Assaf, J.M. (1998) Mathematical modelling of methane steam reforming in a membrane reactor An isothermic model. Brazilian Journal of Chemical Engineering, 15 (2), 160-166. 

The interaction of these two processes can be described by a simple isothermal model, which is based on balances of mass and charge. The model describes the extent of the reforming and oxidation reactions along the anode channel. The essential simulation results can easily be displayed in a conversion diagram which is a phase diagram of the two dynamic state variables, namely the extents of two reactions. 

Experimental unit used for these studies is a conventional automatic catalyatic reformer pilot plant having facilities to regulate process conditions with computer interfacing. Reactor is operated at desired temperature approaching isothermal conditions. 70 ml of I PR-2001 was tested under operating conditions similar to that of the commercial plant in cycle I [2,3,4] Subsequently, it was subjected to accelerated ageing at 10 bar, 500°C, 1.9 WHSV and H2 to... 

Description Hydrocarbon feed is preheated and desulfurized (1). Process steam, generated from process condensate in the isothermal shift reactor (5) is added to give a steam ratio of about 2.7 reformer feed is further preheated (2). Reformer (3) operates with an exit temperature of850°C. 

Reformed gas is cooled to the shift inlet temperature of 250°C by generating steam (4). The CO shift reaction is carried out in a single stage in the isothermal shift reactor (5), internally cooled by a spiral wound tube bundle. To generate MP steam in the reactor, de-aerated and reheated process condensate is recycled. 

The synthesis loop consists of a recycle compressor, feed/effluent exchanger, methanol reactor, final cooler and crude methanol separator. Krupp Uhde s methanol reactor is an isothermal tubular reactor with a copper catalyst contained in vertical tubes and boiling water on the shell side. The heat of methanol reaction is removed by partial evaporation of the boiler feedwater, thus generating 1—1.4 tons of MP steam per ton of methanol. Advantages of this reactor type are low byproduct formation due to almost isothermal reaction conditions, high heat of reaction recovery, and easy temperature control by regulating steam pressure. Tb avoid inert buildup in the loop, a purge is withdrawn from the recycle gas and is used as fuel for the reformer. 

Heated fuel and water are reformed and isothermally oxidised at the MCFC anode. The unused fuel and depleted air from the anode are burnt with added air in a catalytic oxidiser, the output of which heats the cathode and supplies it with oxygen. The cathode exhaust heats the incoming fuel and water in a heat exchanger. The latter exhausts to desired users, for example steam generation or thermal process. 

In the same way, the result of competition amongst the three surviving PEFC, SOFC and MCFC fuel cell types is not predictable. For example, the SOFC has the nascent ability to oxidise natural gas directly, and the MCFC is fuel omnivorous as a result of its mature 600 °C isothermal anode reform capability. Those latter attributes are in contrast to the confinement of the PFFC to hydrogen of minimal CO content, from hydrocarbons processed in an inefficient combustion-driven reformer (inefficient relative to anode reform). The Ballard PFFC has, however, achieved high power density with good, but not unlimited, manoeuvrability. 

The fuel cells and reformer are in isothermal enclosure, at To, coupled to die environment. 

In other texts, the fuel chemical exergy is thought of as a value independent of temperature and pressure, like combustion enthalpy. Instead it has, above, a maximum at FgTg. The major difference in calculation routes is that the author uses equilibrium conditions dictated by the equilibrium constant within the isothermal enclosure of the fuel cell, or Faradaic reformer, whereas other writers put reactants in, and take products out, at standard conditions. 

The analyses here differ from those of Gardiner (1996), Kotas (1995) and Moran and Shapiro (1993) because of the use of the fugacity calculations from the JANAF tables (Chase etal., 1998), and, more importantly, because the contents of the isothermal enclosure of the fuel cell are at concentrations determined by the equilibrium constant (high vacuum of reactants, high concentration of products). The introduction of a Faradaic reformer is new. 

In Figure A.4 water and methane, each proceeding from store, while being driven by circulators via perm-selective membranes, are reacted isothermally in a notional and conceptually quite new isothermal reformer resembling a fuel cell bounded by perm-selective membranes. The circulators are isothermal concentration cells with Nernst potential differences. 

The plant in Figure A.4 can be dealt with in exactly the same way. The reformer and the two fuel cells would be elevated to IT/SOFC conditions, as in Figure A.6. All surplus fuel, heavy hydrocarbons and unoxidised fuel from the three plant sections, together with three hot exhausts, would be swallowed by a gas turbine combustion chamber as above. That would yield a controllable plant, subject to availability of semi-permeable membranes and of isothermal concentration cells, appropriate to IT/SOFC temperatures and gas turbine pressure. 

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