Types of Fuel Processing Reactors

There are three basic types of fuel processing reactors, namely fixed catalyst beds, monoliths and plate heat-exchangers, which are explained in Chapter 6. 

The application of plate heat-exchanger reactors carries advantages for all types of fuel processing reactors, namely for the reformer, the water-gas shift reactor and the... 

In such cases, radiant heat transfer is used from the combustion of fuel in a fired heater ox furnace. Sometimes the function is to purely provide heat sometimes the fired heater is also a reactor and provides heat of reaction. The special case of steam generation in a fired heater (a steam boiler) will be dealt with in Chapter 23. Fired heater designs vary according to the function, heating duty, type of fuel and the method of introducing combustion air. However, process furnaces have a number of features in common. A simple design is illustrated in Figure 15.19. The chamber where combustion takes place, the radiant section... 

To enhance the heating value of the gas product, a cyclic steam-air process was developed in 1873. This process produced water gas, composed chiefly of carbon monoxide and hydrogen, which had a higher heat value (12,000-13,000 kJ/m3) compared with the producer gas. Furthermore, by adding oil to the reactor, the heating value was enhanced (to 19,000-20,500kJ/m3). This type of fuel gas, carbureted water gas, became the standard for gas distributed to residences and industry in the U.S. until the 1940s. 

In part of a sulfuric acid plant, a stream of pure SO2 at 2 bar and 600 K flowing at a rate of 100 mol/s is mixed with a pure oxygen stream at 293 K, 1 bar, and a flow rate of 50 mol/s and reacted to form SO3. The stream exiting that part of the plant is in chemical equilibrium at 1 bar and 293 K. Joe Udel is interested in improving the energy efficiency of this part of the process and suggests that instead a new type of work-producing reactor (i.e., a fuel cell) be installed that would accept the two pure streams, and work would be extracted. What is the maximum rate at which work could be obtained from this process if such a reactor could be developed ... 

A number of studies have verified the beneficial potential of Pd-based membrane reactors for hydrogen production by investigating critical parameters such as pressure, temperature, catalyst, gas composition and reactor design on the overall performance, as will be discussed below. As the thermodynamics, kinetics and by-product formation vary with the type of fuel/feedstock applied, both the Pd-based membrane and operating conditions need to be tailored in order to guarantee a cost-effective process and sufficient membrane stability. 

Up to now, reprocessed uranium has only been used for the fabrication of a limited number of test fuel assemblies. For this type of fuel, the uranium fraction from the spent fuel reprocessing process is again subjected to an isotope enrichment procedure to obtain a content which is sufficiently high for reactor operation (3.8% in the example shown in Tables 3.1 and 3.2.). Besides the naturally occurring isotopes and this material contains mainly gener-... 

The fuel processing reactors contain different types of flow internals in order to maximize contact surfaces or increase flow turbulence. These internals, made of metal or ceramic, have either an ordered chaimel structure or a chaotic character. Fully resolving the small-scale porous structures is extremely time consuming and computationally intensive. These structures are therefore simplified and represented as porous bodies. A porous structure is not modeled in FLUENT as a solid body penetrated by a fluid, but is only taken into account in terms of its flow interactions and a heat balance averaged over the control volume. Taking the porosity y into account, the Navier-Stokes equations can be written as... 

In steam cracking processes, the amount of coke produced and deposited on the heated pipeline walls depends on the type of fuel employed, operation conditions and the metallurgic nature of pipelines. In addition, coke is also produced in heat exchangers (where temperatures ean be between 400 and 700°C)." Coke deposits with a thickness of some millimeters/centimeters make heat transfer difficult, so the temperature in the reactor must be increased which in turn leads to higher coke formation. Moreover, coke accumulation favors a pressure drop which results in reduced production of olefins. Over time, production must be frequently stopped to remove coke (decoking) from the reaction system. Decoking is carried out with a mixture of water and air to burn the coke. This process is undesirable as it results in a drop in the production of olefins, is expensive to maintain and reduces the longevity of the pipelines. 

Unlike radioisotope generators, nuclear reactors utilize the much more intense process of nuclear chain reaction. Since this process is controlled in the reactor, the energy output could be regulated depending on the system s requirements. It actually could produce twice its nominal power, if necessai"y. Nuclear reactors can pro dde greater electrical output than radioisotope generators using the same types of thermal converters. This output is comparable to that of fuel cells and solar arrays, while nuclear reactors are more durable and compact. 

Selectivity to desired products including light hydrocarbons, gasoline, or diesel fuel depends upon the catalyst employed, the reactor temperature, and the type of process employed. Products of the F-T synthesis are suitable for further chemical processing because of their predominantly straight chain structure and the position of the double bond at the end of the chain. By-products formed on a lesser scale include alcohols, ketones, acids, esters, and aromatics. 

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