José M. Toledo

Total oxidation of some chlorinated hydrocarbons with commercial chromia based catalysts

Abstract Catalytic total oxidation of some chlorinated hydrocarbons (Cl-VOCs) is studied here with four chromia-based commercial catalysts. Catalysts used are: ARI Econ Abator from Wheelabrator, PRO*CLEAN*110 and PRO*HHC*Base from Sud-Chemie AG and R-3-20 from BASF AG. Two different reactors, at two different scales, have been used: a small glass-made reactor for pure and targeted Cl-VOCs, and a metallic reactor at pilot scale located in a slip flow after a fluidized bed incinerator of waste containing PVC. Pure Cl-VOCs used have been ethyl chloride, dichloromethane, trichloroethane and chlorobenzene. Conversions and product distributions are given here at different temperatures, space-velocities and concentrations at inlet. These results, once compared with the ones simultaneously got for other types of catalysts (Pt and V2O5 based) will serve to rank the commercial catalysts used here according to their activity and selectivity. The chromia-based catalysts tested here have proved to be quite active but they also lose some chromium from the catalyst, by attack of the nascent Cl2, having thus a short life when the Cl-content in the flue gas is relatively high.

Biomass gasification with pure steam in fluidised bed : 12 variables that affect the effectiveness of the biomass gasifier

Biomass gasification in fluidised bed with pure steam has already generated a 60 vol.%, dry basis, H2 rich gas that was increased to 70?80 vol.% H2 by using a CO2 sorbent in the gasifier bed. A tar content as low as 0.25 g/Nm? has also been reported when an active catalyst is used in the gasifier bed. Biomass gasification in fluidised bed with pure steam, therefore, has some potential interest for the production of a very rich in H2 clean gas. This work shows in detail 12 operational variables that have already demonstrated a clear influence on the product distribution from the gasifier. Among all the products originating from the gasifier, this study concentrates on the hydrogen and tar contents in the raw gasification gas.

On the selection of the catalyst among the commercial platinum-based ones for total oxidation of some chlorinated hydrocarbons

Abstract Catalytic total oxidation of some selected chlorinated hydrocarbons is studied with several Pt-based catalysts. Chlorinated hydrocarbons used have been ethyl chloride, trichloroethylene and dichloromethane, alone or mixed with some hydrocarbons, such as toluene. Eighteen different catalysts have been tested from eight different manufacturers (Degussa AG, Sud-Chemie AG, Kataleuna GmbH, Chimet, Johnson Matthey, Prototech Co., …) and from three research institutions (Universities of Leiden (NL) and Wroclaw (PL) and Spanish CSIC-ICP). Catalysts both in the form of spheres (particulates) and of monoliths are used. Selection of the best catalyst(s) is made based on their activity, selectivity and life. Apparent energies of activation for these reactions on these catalysts, using an empirical first-order reaction rate, are given. There are interesting or noticeable differences in activity and selectivity among the tested Pt-based catalysts. In overall they are not so active as the chromia and vanadia-based catalysts but they have an high life, reason why they can be recommended for this application.

Incineration of doped sludges in fluidized bed. Fate and partitioning of six targeted heavy metals. I. Pilot plant used and results

Incineration of sewage sludge doped with several heavy metals was studied at small pilot plant scale in a bubbling fluidized bed of 15cm i.d. and 5.2m height. Some ceramic and metallic filters were tested at a relatively high temperature (600-700 degrees C) to check their usefulness for partitioning of heavy metals in the flue gas. The work was focused on the fate of six selected heavy metals (Cr, Cd, Ni, Zn, Cu, Pb). In this process, there were four exit flows or discharges for these metals: bottom ash, coarse fly ash, cake filter or fine fly ash and flue exit gas. The distribution or partitioning of each heavy metal (HM) among these four exit flows was studied. Only cadmium and sometimes lead showed any difference between the different HMs considered. All other HMs seems to have the same fate, distribution or partitioning. Such distribution is governed or ruled by the fluid dynamics in the incinerator, cyclone and ceramic filter. Most of the HMs do not have enough residence time in this incinerator type to diffuse out of the ash particle and so remain in the particle. The amount of each HM in each exit flow in this process is governed by fluid dynamics and kinetics and not at all by thermodynamics.

Performance of CaO and MgO for the hot gas clean up in gasification of a chlorine-containing (RDF) feedstock

Calcined limestone (CaO) and calcined dolomite (CaO.MgO) were tested at bench scale to study their usefulness in cleaning hot raw gas from a fluidized bed gasifier of a synthetic or simulated refuse-derived fuel (RDF) with a high (3 wt%) content in chlorine. In the gas cleaning reactor two main reactions occurred simultaneously: the elimination of HCl and the elimination of tar by steam reforming. The elimination of HCl formed CaCl2 and MgCl2 with melting points below the high (above 800 degrees C) temperatures required for the simultaneous tar elimination reaction. So, the CaO-based particles progressively melted and the catalytic gas cleaning reactor became a compact, agglomerated or glued, cake. Therefore, the life and usefulness of the CaO-based solids used was very low. Nevertheless, and to further avoid these problems, some positive guidelines for future research are proposed here.