Reactors adiabatic catalytic

The hydrocarbon gas feedstock and Hquid sulfur are separately preheated in an externally fired tubular heater. When the gas reaches 480—650°C, it joins the vaporized sulfur. A special venturi nozzle can be used for mixing the two streams (81). The mixed stream flows through a radiantly-heated pipe cod, where some reaction takes place, before entering an adiabatic catalytic reactor. In the adiabatic reactor, the reaction goes to over 90% completion at a temperature of 580—635°C and a pressure of approximately 250—500 kPa (2.5—5.0 atm). Heater tubes are constmcted from high alloy stainless steel and reportedly must be replaced every 2—3 years (79,82—84). Furnaces are generally fired with natural gas or refinery gas, and heat transfer to the tube coil occurs primarily by radiation with no direct contact of the flames on the tubes. Design of the furnace is critical to achieve uniform heat around the tubes to avoid rapid corrosion at "hot spots."... 

Nickel catalysts were used in most of the methanation catalytic studies they have a rather wide range of operating temperatures, approximately 260°-538°C. Operation of the catalytic reactors at 482°-538°C will ultimately result in carbon deposition and rapid deactivation of the catalysts (10). Reactions below 260°C will usually result in formation of nickel carbonyl and also in rapid deactivation of the catalysts. The best operating range for most fixed-bed nickel catalysts is 288°-482 °C. Several schemes have been proposed to limit the maximum temperature in adiabatic catalytic reactors to 482°C, and IGT has developed a cold-gas recycle process that utilizes a series of fixed-bed adiabatic catalytic reactors to maintain this temperature control. 

It is the purpose of this chapter to discuss presently known methods for predicting the performance of nonisothermal continuous catalytic reactors, and to point out some of the problems that remain to be solved before a complete description of such reactors can be worked out. Most attention will be given to packed catalytic reactors of the heat-exchanger type, in which a major requirement is that enough heat be transferred to control the temperature within permissible limits. This choice is justified by the observation that adiabatic catalytic reactors can be treated almost as special cases of packed tubular reactors. There will be no discussion of reactors in which velocities are high enough to make kinetic energy important, or in which the flow pattern is determined critically by acceleration effects. 

The Lurgi LPM process involves the same basic steps as the ICI processes. The two processes differ mainly in their reactor designs and the way in which the produced heat is removed as shown in Figure 12.18. The ICI design consists of a number of adiabatic catalytic beds, and cold gas is used to cool the reactant gases between the beds. The highest temperature is reached in the first catalyst bed. The Lurgi... 

R. Christoph and M. Baems, Modelling of an adiabatic, catalytic fixed bed reactor with catalyst deactivation and pore-diffiisional effects for the methanation of CO, Ber.Bunsnges.Phys. Chem., 90(1986)981. 

The conventional MTBE synthesis consists of a reaction of isobutene and methanol over an acidic sulfonated cation-exchange catalyst. This reaction is highly selective, equilibrium-limited, and exothermic in nature. Several types of industrial reactors such as tubular reactors, adiabatic reactors with recycle, and catalytic distillation configurations have been utilized to cany out the MTBE synthesis reaction. The factors considered in the optimal design of a MTBE unit include the following items [52]. 

Figure 3.33 shows a schematic of the CDTech MTBE/ETBE/TAME process. This is essentially the same as the CDTech MTBE process presented earlier. The process is unique in the sense of using a boiling point reactor and catalytic distillation (CD) [61]. The C4 feed and methanol is fed to the boiling point reactor (1). This is a fixed-bed downflow adiabatic reactor, in which the liquid is heated to its boiling point by the heat of reaction and... 

The overall reactor model comprises, as the heart of it, the single catalyst pellet model which is formulated in an overall framework that includes the changes in the bulk fluid phase. The equations for the catalyst pellet coupled with the equations for the bulk fluid phase represent what we may call in certain cases, the overall reactor model or in a more restricted sense, the catalyst bed module. This catalyst bed module may represent the overall reactor model in certain cases such as the single adiabatic catalytic packed bed reactor. In other cases, this module may represent only the essential part of the overall reactor model such as in non-adiabatic and multi-bed reactors. 

In the following sections, we will analyse the dynamic behaviour of a gas-fed, adiabatic, catalytic-bed reactor, of the sort commonly used for methanol and ammonia production. Figure 20.4 gives a schematic representation of an element from such a... 

Use of Rate Equations in Reactor Design. The method of using the rate equations for catalytic reactions to calculate the reactor size and amount of catalyst needed for a specified conversion and feed rate is very similar to the method used for noncatalytic reactions. The calculations may be divided into three types, namely, those for isothermal reactors, adiabatic reactors, and nonisothermal nonadiabatic reactors. In all three cases where the feed rate F and the desired conversion x are specified, the weight of catalyst needed can be calculated from the expression... 

Figure 11.3-1 Multibed adiabatic reactor for catalytic reforming (from Smith [5]).

Figure 13.12 The principle of USO temperature and conversion profiles in an adiabatic catalytic reactor before the first reversal of flow direction (redrawn from Matros et al., 1984).

Figure 3 shows the steady-state radial temperature profiles for the two adiabatic catalytic beds operating at conditions of the optimal point. The corresponding axial temperature profiles in the interbed heat exchanger are also included in Fig. 3, for the tube side (Tt) and shell side (Tsh). The simulation results have been compared with industrial data corresponding to a large scale ammonia converter. The deviations at the reactor outlet were less than 0.2% (relative error) in composition and 14 °C in temperature (Toutz)-... 

For an adiabatic unit operation, such as an adiabatic catalytic reactor where transferred heat, Q, and shaft work, W, both are zero, the enthalpy change is thus zero, since the basis for the entiialpy is the heat of formation. A heat loss may be taken into consideration. 

Figure 4.10.22 (a, b) Evolution of temperature in an adiabatic batch reactor during catalytic decomposition of H2O2, ATj = 58 K To = 302 K data from Baerns eto/. (2006). 

The oil feed is mixed with hydrogen-rich gas and then preheated to the proper reactor inlet temperature. The combined fe (oil+hydrogen) enters the top of the fixed bed reactor, called a trickle-bed reactor. Generally the catalyst bed is divided into several beds, which are separated by quenching zones where cold hydrogen-rich streams are injected in order to control the temperature inside the reactor. ITie catalytic beds are adiabatic and therefore temperature increases along each bed since the reactions are exothermic. 

The reactor combinations for the two reactors in series consist of two fixed-beds for the Arco process an expanded bed followed by a catalytic distillation reactor for lEP a fixed-bed followed by a catalytic distillation reactor for CDTECH and two fixed-beds for Phillips. The Huls process uses an adiabatic reactor for the second reactor. 

The scheme of commercial methane synthesis includes a multistage reaction system and recycle of product gas. Adiabatic reactors connected with waste heat boilers are used to remove the heat in the form of high pressure steam. In designing the pilot plants, major emphasis was placed on the design of the catalytic reactor system. Thermodynamic parameters (composition of feed gas, temperature, temperature rise, pressure, etc.) as well as hydrodynamic parameters (bed depth, linear velocity, catalyst pellet size, etc.) are identical to those in a commercial methana-tion plant. This permits direct upscaling of test results to commercial size reactors because radial gradients are not present in an adiabatic shift reactor. 

If kinetic processes on catalytic surfaces in S02 oxidation are assumed to be at steady state, temperature and concentration fields in a radially symmetrical, adiabatic catalyst bed are described by the equations collected in Table IX for the reactor space 0 and time I > 0 (Matros, 1989 ... 

Trickle Hydrodesulfurization A process for removing sulfur-, nitrogen-, and heavy-metal-compounds from petroleum distillates before catalytic cracking. The preheated feed is hydrogenated, without a catalyst, in an adiabatic reactor at 315 to 430°C. Developed by Shell Development Company. As of 1978, 91 units had been installed. 

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