Ryszard Miller

Superadiabatic Lean Catalytic Combustion in a High-Pressure Reactor

The isobaric lean catalytic combustion in a high-pressure recuperative reactor in view of gas turbine technologies is examined. A new type of the T/P bifurcation diagram is revealed and elucidated. It is found that the reactor thermally stabilizes at higher pressures. The elevated P to 0.5 MPa extends bifurcation isola for mfin, i.e. each fold is improved by approximately 15%. The thermal and concentration hysteresis bifurcation diagrams are also improved, i.e. the ignition temperature was decreased from 490 to 475 K and the extinction concentration from 177 to 157 ppmv, respectively. The pressure drops are alleviated by the factor of P/P0 slightly corrected for the gas thermal expansion effect. It is also revealed, that the intra-phase mass transfer resistances are reduced at elevated pressures. The fuel conversion pressure dependences are provided for some types of high-pressure reactors.

Thermal-catalytic oxidation of waste gases

Abstract Thermal-catalytic oxidation, consisting of combined thermal and catalytic processes, is proposed as a new method to neutralize waste gases. A comparison between the proposed two-step thermal-catalytic and catalytic neutralization processes is done at temperatures ranging from 350 to 750 K. The efficiency of the neutralization of waste gases that is obtained by using the thermal-catalytic method is higher, compared with the efficiency of waste gas neutralization by using the catalytic method. The observed difference ranges from 20 to 10%, as was found for model waste gas containing ethyl acetate, and from 10 to 5%, as was determined in the case of a toluene imitating toxic component of waste gases. In addition, the mechanism of the thermal-catalytic process is studied. The first step of this process, thermal oxidation, is shown to influence the subsequent one, catalytic oxidation.

Design of Dynamics of a Recuperative Catalytic Combustor: Enhancement in Operation and Control

The current contribution is aimed to describe and design the dynamics of the recuperative catalytic combustor. The step responses of the combustible concentration, fuel flow rate, fuel temperature and three manipulated variables are determined for the non-controlled combustor. The time delays, time constants and gains are determined for the temperatures measured in two points in the catalytic zone and its dependencies on the process and geometrical parameters are discussed. The frequency response analysis conducted shows that in the combustor with a higher time constant medium term input disturbances are effectively attenuated. In order to handle long term impulses of lean or rich fuels, the control strategy dedicated to the current combustor is proposed. It is verified in the example in which the frequently used control algorithm is applied to simulate the process control. The results show that the improvement is attained in combustor transient operation and control.

The Influence of Flame-Generated Free Radicals on the Thermal Oxidation of Waste Gases

Studies of the thermal oxidation of waste gases were carried out in two variants. During the first, the destruction of waste gases was facilitated by hydrogen flame-generated radicals. During the other variant, this flame was not used, but the same temperature was maintained as in the first one. The waste gases used were mixtures of toluene with air and methane with air of 200 and 400 ppm concentrations, respectively. The experiments were performed in a flow reactor within the temperature range of 800 to 1330 K. The efficiency of oxidation of methane and toluene obtained during the first variant was considerably higher than that obtained in the second one. This was due to the promotional effect of the hydrogen flame.