Sulfur Removal Process. An automated gas solubility measurement system was used to collect data on the solubility of hydrogen sulfide, carbon dioxide, propane, and n-butane in a variety of these solvents. The partial pressure of solute gas in these experiments was between 3 and 100 kPa. Correlations for Henry's law coefficients are given as a function of temperature. Gas solubility in the organic solvents decreases when small amounts of water (<6 wt %) are also present. Gas solubility in solvent-water mixtures at the conditions tested is shown to follow a simple mixing rule. An improved correlation is presented for previously published solubility data for sulfur dioxide, which includes the effect of composition as well as temperature on the Henry's law coefficient.

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Addition of metal chelates to the liquor in a wet stack gas scrubber to improve removal efficiency of both NO and S02 may provide a new environmental control technology without requiring major capital modification to existing power plants. Criteria for an effective metal chelate additive include large absorption capacity and rapid binding rate for NO and rapid regeneration of metal chelates from nitrosyl metal chelates by reaction with absorbed S02 in aqueous solutions. Data on the thermodynamics and kinetics of a number of the chemical reactions involved have been obtained. Laser Raman spectroscopy has been employed to identify, directly and unambiguously, some of the reaction intermediates and products. These results have been used to predict optimum scrubber design and performance for desulfurization and denitrification of flue gases.

Samples of calcined limestone particles having a diameter of about 1 mm were exposed to simulated coal gases containing between 500 and 18 000 ppm H2S for temperatures ranging from 560 to 1100 °C in a differential tube reactor. The formation of CaS was followed quantitatively as well as qualitatively to elucidate the reaction mechanism. Contrary to the limited conversion of CaCOs to CaS, it was found that the limestone particles could be completely converted to CaS by 1% H2S in about 1 h if the particles are precalcined or if the rate of calcination is higher than the rate of sulfidation. The reaction then takes place between CaO and H2S and follows a shrinking-core mechanism. The reaction kinetics is controlled by the diffusion of H2S through the pores of the CaS product layer formed around the lime particle (effective diffusivity between 2.8 x 10-6 and 5.1 x 10-6 m2/s). The kinetics of the sorption of H2S by CaO is relatively insensitive to the reaction temperature, and the reaction rate does not decrease significantly when the CaO is severely sintered for several hours at 1050 °C prior to sulfidation.

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H2S sorption by 18-35 mesh particles (average mass radius of 0.40 mm) of three different calcium-based sorbents (limestone, CaC03; dolomitic limestone, dolomite, MgC03-CaC03) was tested under simulated coal gas in a differential tube reactor.Two fundamentally different behaviors were observed. Above the calcination temperature of CaC03, complete conversion of CaC03 to C a s can be achieved with all three sorbents; the reaction rate increases as the magnesium-to-calcium ratio increases in the sorbent and the reaction rate is controlled by the diffusion of H2S through the Cas product layer and by the kinetics of the calcination of CaC03 to CaO. However, below the calcination temperature of CaC03 (about 900 "C under 1 bar of C o d , less than 20% of the CaC03 in limestone can be converted to C a s compared t o 100% in dolomite. For the dolomitic limestone, all the calcium atoms associated with the dolomite regions can be converted to C a s whereas only 20% of those associated with the limestone regions can be converted. Above 710 "C, the sulfidation rate of dolomite and dolomitic limestone is controlled by the diffusion of H2S through the product layer. Below 710 "C, the kinetics of calcination of MgC03 as well as the rate of the chemical reaction between CaC03 and H2S become the limiting steps in the overall reaction kinetics.

We investigated the performance of synthetic high purity monocrystalline diamond radiation detectors fabricated with TiW, Cr/Au and a novel metallization technique utilising diamond-like carbon tunnelling junction and Pt/Au as electrical contacts. The investigation was carried out under irradiation with 60Co gamma-rays, 90Sr electrons and 241Am alpha-particles. The experimental results with respect to I-V dark current levels, irradiation photocurrent, signal-to-noise ratio and time response have been compared and discussed. Results show an ohmic behaviour of the DLC/Pt/Au contact, a charge collection efficiency of 100% at an applied electric field of 0.377 V/ mum for all electrical contacts (under 90Sr electrons irradiation) at a correspondent dark current value of less than a picoAmpere. The single crystal CVD DLC/Pt/Au diamond radiation detector reported here shows spectroscopic energy resolution of 1.1% at an applied voltage of +450 volts (0.9 V/mum) under 5.5 MeV alpha particle irradiation. No dasiamemorypsila or dasiapumpingpsila effect was observed for the DLC/Pt/Au contact at positive bias; the signal was also stable (fluctuations below 0.5%) and reproducible under 60Co irradiation, with a signal-to-noise ratio > 10000:1 and a linearity in the dose rate response

The presence of the S02-radical ion in aqueous solutions of sodium dithionite has been previously reported. 1 Electron spin resonance (e.s.r.) measurements showed that the S02-concentration varied as the square root of the dithionite concentration, suggesting a monomerization reaction of the form fe» s2o4-2 2S02-(i) Ad This reaction has received significant polarographic study by Cermák2 and chronopotentiometric studies by Fischer8 and co-workers. Based on experimental observation in a 0.1 M solution of sodium hydroxide, Cermák reported a value of 6 X 10-8 mole72 l.-7' sec.-1 at 40°for the quantity km/ where km is