No abstract

This paper describes a laboratory-scale study on the use of recirculating cyclones as reaction chambers for dry scrubbing of gaseous HCl with solid slaked lime particles. This gas cleaning system combines a numerically optimized reverse flow gas cyclone (RS VHE geometry) with a straight-through cyclone concentrator, which simultaneously increases the capture of the solid particles and promotes their partial recirculation. A laboratory-scale study was undertaken to test this technology and to compare its performance to a modified Stairmand HE reverse flow cyclone without recirculation. The experimental conditions were: reaction temperature ≈326 K, gas flow rate ≈2.9 × 10 −4 N m 3 s −1 and relative humidity of the gas ≈8.5%. The experimental variables tested were the solids load (1.0-9.2 × 10 −7 kg s −1 ) and HCl concentration (0.4-2.8 × 10 −2 mol m −3 ) in the inlet gas.The experimentally obtained particulate removal efficiencies with the recirculating cyclones (≈98%) were higher than those obtained with the Stairmand HE cyclone (≈93%), with the additional advantage of having significantly lower pressure drop. As for the acid removal efficiencies (≈10-96%), no significant differences were found between the two systems tested under the same experimental conditions.The possibility of using optimized recirculating cyclones for gas cleaning in a dry scrubbing process is very promising, since this is a low cost technology, highly efficient both for the removal of acid gases and for the capture of solid particles, which has the advantage of not requiring a post-reaction de-duster.

No abstract

An integral packed-bed reactor was used to determine the kinetics of the water-gas shift (WGS) reaction over a CuO/ZnO/Al 2 O 3 catalyst, under operating conditions such that there was no film or intraparticle resistance. Experiments were carried out over a wide range of temperatures and space times using a typical reformate gas mixture (4.70% CO, 34.78% H 2 O, 28.70% H 2 , 10.16% CO 2 , balance N 2 ). In the first part of the work, three different mechanistic-rate equations and two empirical kinetic models are proposed to describe the WGS kinetic data throughout the entire range of temperatures. To improve the independence of the parameters in using the Arrhenius and van't Hoff equations, the temperature was centered. Good agreement was obtained between the Langmuir-Hinshelwood (LH) rate equations and the experimental results. Further, analysis using two different temperature ranges for parameter estimation revealed distinct rate-controlling mechanisms for each range. For temperatures of 180-200 °C, the associative (LH) mechanism was predominant, whereas the redox pathway showed the best fit to the experimental reaction rates in the range of 230-300 °C. Finally, an isothermal plug-flow reactor model was used to simulate the packed-bed tubular reactor for the WGS reaction using the composed kinetics. The reactor model was assessed against the experimental CO outlet concentration, and satisfactory agreement was found between the model predictions and the experimental results.

No abstract