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If, however, hydrogen is the desired end-product, the coal gas (primarily the CO product) undergoes the water gas shift reaction where more hydrogen is produced by additional reaction with water vapor: CO + H 2 O → CO 2 + H 2. Although other technologies for coal gasification currently exist, all employ, in general, the same chemical processes.
In the Gutzeit test, AsH 3 is generated by reduction of aqueous arsenic compounds, typically arsenites, with Zn in the presence of H 2 SO 4. The evolved gaseous AsH 3 is then exposed to AgNO 3 either as powder or as a solution. With solid AgNO 3, AsH 3 reacts to produce yellow Ag 4 AsNO 3, whereas AsH 3 reacts with a solution of AgNO 3 to give ...
Photomicrograph made with a scanning electron microscope and back-scatter detector: cross section of fly ash particles. Fly ash, flue ash, coal ash, or pulverised fuel ash (in the UK)—plurale tantum: coal combustion residuals (CCRs)—is a coal combustion product that is composed of the particulates that are driven out of coal-fired boilers together with the flue gases.
A coal-fired power plant with ash ponds. Coal ash, also known as coal combustion residuals (CCRs), is the mineral residue that remains from burning coal. Exposure to coal ash and to the toxic substances it contains may pose a health risk to workers in coal-fired power plants and residents living near coal ash disposal sites.
The gasification process occurs as the char reacts with steam and carbon dioxide to produce carbon monoxide and hydrogen, via the reactions C + H 2 O → H 2 + CO and C + CO 2 → 2CO. In addition, the reversible gas phase water-gas shift reaction reaches equilibrium very fast at the temperatures in a gasifier.
Using the coal gas waste as feedstock, researchers developed new processes and synthesized natural organic compounds such as Vitamin C and aspirin. The German economy relied on coal gas during the Second World War as petroleum shortages forced Nazi Germany to develop the Fischer–Tropsch synthesis to produce synthetic fuel for aircraft and tanks.
Underground coal gasification converts coal to gas while still in the coal seam (in-situ). Gas is produced and extracted through wells drilled into the unmined coal seam. Injection wells are used to supply the oxidants (air, oxygen) and steam to ignite and fuel the underground combustion process. Separate production wells are used to bring the ...
The combustion of coal releases diverse chemicals into the air. The main products are water and carbon dioxide, just like the combustion of petroleum. Also released are sulfur dioxide and nitrogen oxides, as well as some mercury. The residue remaining after combustion, coal ash often contains arsenic, mercury