1,721,175 research outputs found
Mercury removal from geothermal exhaust gas by sulfur-impregnated and virgin activated carbons
No full textSulfur-impregnated and virgin activated carbons have been used in a laboratory scaled fixed-bed reactor to investigate their capability of removing mercury vapours from a gas mixture containing H2S, O-2 and moisture that is representative of the exhaust gas emissions of the geothermal power plants of the Monte Amiata field in Italy. The observed deposition of sulfur from H2S oxidation on the carbonaceous matrix increases the mercury scavenging capacity of the commercial sulfur-impregnated activated carbon and makes virgin activated carbon capable of adsorbing mercury vapours by the formation of HgS contextually to the deposition of sulfur. achieving a mercury adsorption capacity comparable to the commercial sulfur-impregnated activated carbon. This result suggests that the extremely economic virgin activated carbon can be used in this specific application, provided that a suitable carbonaceous matrix is selected to achieve a sulfur deposition rate that can guarantee a high mercury adsorption capacity
Recovery of silica gel from blast furnace slag
No full textThis work concerns a process for the recovery of silica gel from blast furnace slag. It consists of a leaching of the slag with H2SO 4, separation of gypsum, precipitation of silica gel from the filtrate at pH 3.2, followed by the washing of the raw precipitate. The effect of the slag particle-size, the leaching time and the washing extent on the overall recovery yield and silica gel purity has been investigated
Deposition of sulfur from H2S on porous adsorbents and effect on their mercury adsorption capacity
No full textThe deposition of elemental sulfur on porous adsorbents (commercial pre-sulfurised activated carbons and alumina, an HY zeolite and a selenised adsorbent) has been observed when the adsorbents are exposed to a gaseous stream containing hydrogen sulfide and oxygen. The sulfur deposition from H2S is more marked for the activated carbons and the alumina, it is substantially decreased when zeolite is used, and is practically insignificant for the selenium-based adsorbent. For the pre-sulfurised activated carbons, further sulfur deposition is initially beneficial in terms of increasing their mercury chemisorbing capacity but, subsequently, the structural properties are affected and this results in a drastic reduction in adsorption capacity. Further sulfur deposition on the pre-sulfurised alumina seems immediately to compromise its capacity to chemisorb mercury. The selenium-based adsorbent shows problems with detachment of the fine mercuric selenide powder from the matrix. Sulfur deposition on the initially unsulfurised zeolite improves its mercury adsorption capability. The initially sulfur-free zeolite could be a promising adsorbent for the treatment of this specific type of gas stream. In fact, after a moderate level of sulfur deposition from oxidation of hydrogen sulfide, it can simultaneously chemisorb the mercury vapours by reaction with the sulfur itself while, unlike the activated carbons and alumina, maintaining its required structural properties for a relatively long period
Devolatilizzazione e combustione di singole particelle di una lignite italiana
No full textThe devolatilization and combustion of single particles of an Italian lignite has been observed for different particles diameters and air flow temperatures: a low volatile content bituminous Polish coal has been studied for comparison
Phisical and combustion characterization of pyrolytic oils derived from biomass material upgraded by catalytic hydrogenation
No full textPhysical and combustion properties of a pyrolytic bio-oil are determined both as-obtained and after catalytic hydrodeoxygenation. The tests demonstrate that the hydrogenation treatment improves the oil as regards combustibility, viscosity and acidity. Combustion properties of the oil have been characterized by evaporation and temperature programmed combustion profiles
Silica separation from reinjection brines having diferent composition at Monte Amiata geothermal power plant
No full textSilica separation from reinjection brines at Monte Amiata geothermal plant, Italy
No full textA process for the separation of silica from geothermal reinjection brines is reported, in which the phases of coagulation, sedimentation and filtration of silica are involved. The effectiveness of lime and calcium chloride as coagulating agents has been investigated and the separating operations have been set out. Attention has been focussed on Monte Amiata reinjection geothermal brines, whose scaling effect causes serious problems in the operation and maintenance of reinjection facilities. The study has been conducted using different amounts of added coagulants and at different temperatures, to determine optimal operating conditions. Though calcium chloride was revealed to be effective as a coagulant of the polymeric silica fraction, lime has also proved capable of removing monomeric dissolved silica at high dosages. Investigation on the behaviour of coagulated brine has revealed the feasibility of separating the coagulated silica by sedimentation and filtration
Recovery of nickel from Orimulsion fly ash by iminodiacetic acid chelating resin
No full textMacroporous resins containing imminodiacetic acid (IDA) groups (Lewatit TP-207, Purolite S-930 and Amberlite IRC-748) were studied under dynamic conditions for uptake of nickel ions from the sulphate solution at pH 4 deriving from preliminary acid leaching of Orimulsion fly ash and subsequent vanadium recovery and impurities removal stages. The effects of temperature and ionic medium on the Ni adsorption were investigated. The Lewatit TP-207 showed higher Ni uptake capacity in all operating conditions examined with an adsorption capacity of 1.32 mmol of Ni/g at 40 °C using the real process solution at pH 4. The extraction of Ni adsorbed on the resin was obtained using 10 wt.% H 2SO4; the resultant concentrated solution of nickel sulphate, containing about 13 g/L of nickel, can be suitable for elettrowinning, precipitation etc
Investigation on the porosity development by CO2 activation in heavy oil fly ashes
No full textThe porosity evolution in heavy oil fly ashes subjected to activation with CO2 has been examined. The work examined four different heavy oil fly ashes that, after preliminary acid leaching, have been pyrolyzed at 900 °C and then activated with CO2 at the same temperature for different times. A different evolution of porosity was observed according to the different reactivity of the samples during activation. The activated samples have been characterised as regards the surface area and the pore volume. The scanning electron microscope-energy dispersive spectrometer microanalysis has been used to interpret the experimental results
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