Premixed reactants

At first glance, the exclusion of premixed reactants and density variations might seem to be too drastic. (Especially if one equates turbulent reacting flows with combustion. 1)... 

Any reactants capable of forming combustion products are composed of a mixture of oxidizer and fuel components, and the flame is produced by the reaction of the mixture. Two types of flames can be formed when the mixture bums a premixed flame or a diffusion flame.[i-2] A premixed flame is formed by the combustion of the two components when they are premixed prior to burning in the combustion zone. The intermingled oxidizer and fuel component molecules in the premixed reactants then react homogeneously. The temperature and the concentration of the products increase uniformly in the combustion zone. 

A 15-fold glass tube parallel packed-bed reactor was introduced [67, 68], which is similar to conventional catalyst testing equipment (Figure 3.39). The premixed reactant gas is supplied by a 16-port valve either to the bypass or to one of the 15 reactors. By a second 16-port valve, the product gas stream of a selected reactor can be channeled to the quadrupole mass spectrometer. The full automation of the screening set-up allows the investigation of 15 catalysts per day [67]. 

In the case of reaction and diffusion or premixed reactants in a CSTR (figure 13) (1- 3d)/3d % tR/tD. T -s is an interesting rule of thumb for rapid estimation of the extent of segregation. 

An experimental apparatus that under certain conditions approximates closely a well-stirred reactor is a spherical chamber into which premixed reactants are injected centrally through a perforated tube and out of which the reaction products flow through a number of ports located at various positions in the outer shell. The mixing is driven by the fuel-injection jets that are formed at the tube perforations, and the apparatus has been called the jet-stirred reactor. The average residence time of an element of gas in the reactor is... 

A novel application of a symmetric porous membrane as a catalyst carrier but not as a permselective barrier is to use the membrane itself as the reaction zone for precise control of the stoichiometric ratio [Sloot et al., 1990]. In this case, the reactants are fed to the different sides of the membrane which is impregnated with a catalyst for a heterogeneous reaction. The products diffuse out of the membrane to its both sides. If the reaction rate is faster than the diffusion rate of the reactant in the membrane, a small reaction zone or theoretically a reaction plane will exist in the membrane. An interesting and important consequence of this type of membrane reactor is that within the reaction zone the molar fluxes of the reactants arc always in stoichiometric ratio and the presence of one reactant in the opposing side of the membrane is avoided. The reaction zone can be maintained inside the membrane as long as the membrane is symmeuic and not ultrathin. Therefore, membrane reactors of this fashion are particularly suited for those processes which require strict stoichiometric feed rates of premixed reactants. A symmetric porous a-alumina membrane of 4.5 mm thick was successfully tested to demonstrate the concept [Sloot et al., 1990]. 

The experiments were performed in a 102-millimeter diameter axisymmetric dump combustor shown in Fig. 16.1a. The inlet diameter is 41 mm. Ethylene was injected at 24.5 inlet diameters upstream of the dump plane to simulate the prevaporized, premixed reactants entering a ramjet combustor. The cylindrical combustor is 610 mm long and is capped by a 38-millimeter diameter exhaust... 

Temperature history of heat recirculating combustion of premixed reactants in one-dimensional adiabatic system. 

A tube which feeds the burner in premixed reactants it is for this reason that this type of flame is called a premixed flame and possesses very different characteristics to diffusion flames. 

Contents P. A. Libby, F.A, Williams Fundamental Aspects. - A, M. Mellor, C, R, Ferguson Practical Problems in Turbulent Reacting Hows. - R. WBilger Turbulent Hows with Nonpremixed Reactants. -KN.C Bray Turbulent Hows with Premixed Reactants. - E, E. O Brien The Probability Density Function (pdQ Approach to Reacting Turbulent Hows. - PA,Libby, FA. Williams Perspective and Research Topics. 

For stoichiometric amounts of premixed reactants in a CSTR, an empirical correlation is found... 

Ever since Toor and co-workers (Vassilatos and Toor, 1965 Toor, 1969 Mao and Toor, 1971 Li and Toor, 1986) defined methods for relating reaction conversion for non-premixed reactants to their degree of mixing, workers in the field of mixed chemical reactors have attempted to build upon and refine their analysis. 

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