Coal absorbed

The natural ventilation in coal storage piles is generally adequate to remove sensible heat as fast as it is liberated in the oxidation process. However, in situations where the ventilation is adequate to maintain oxidation but not adequate to dissipate the heat produced, the coal absorbs the heat causing a rise in the internal temperature. A chain reaction follows in that the oxidation rate increases with increasing temperature which, if allowed to proceed unchecked in a storage pile, the ignition temperature of the coal will eventually be reached and the pile will begin to smolder. 

Higher-boiling fractions supply the creosotes, absorbing oils, anthracene, coal tar fuels, road tar, etc. 

In this process, any sulfur present in the coal exits the gasifier as hydrogen sulfide which is removed by various processes such as a Hohnes-Stretford unit where the sulfide is absorbed and regenerated. The resulting sulfur is filtered out as a cake (39 wt %) which is sold as a valuable feedstock (see Coal CONVERSION PROCESSES, GASIFICATION SULFURREMOVAL AND RECOVERY). 

Other Uses. The quantity of coal used for purposes other than combustion or processing is quite small (2,6). Coal, especially anthracite, has estabHshed markets for use as purifying and filtering agents in either the natural form or converted to activated carbon (see Carbon). The latter can be prepared from bituminous coal or coke, and is used in sewage treatment, water purification, respirator absorbers, solvent recovery, and in the food industry. Some of these markets are quite profitable and new uses are continually being sought for this material. 

In ECS s 1986 repowefing project Babcock and Wilcox (B W) constmcted a bubbling-bed section to ECS s existing 125 MWe pulverized-coal furnace to produce 31.3 t/h of lime, usiag cmshed coal as the source of heat to calciae limestone ia the fluidized bed. A portion of the lime is drawn from the bed as bottom ash and a portion is collected as fly ash. Both portions are transferred to a cement (qv) plant adjacent to the boiler. The hot flue gas from the EBC flows iato the existing main pulverized-coal furnace, ia which a B W LIMB system was also iastaHed to absorb sulfur dioxide dufing those times when the EBC is not operating. 

The cooled syngas from any of the TCGP modes is then routed to a water scmbber to remove particulates. The gas is cooled further and is passed through an absorber that removes nearly all the sulfur, mainly H2S, in the gas. Valuable elemental sulfur is produced from the H2S stream. Normally 97—99% of the sulfur entering the TCGP in the coal is recovered as salable elemental sulfur (12). 

The volatile matter is the portion of coal which, when the coal is heated in the absence of air under prescribed conditions, is liberated as gases and vapors. Volatile matter does not exist by itself in coal, except for a httle absorbed methane, but res lilts from thermal decomposition of the coal substance. 

Fuel Characteristics Fuel choice has a major impact on boiler design and sizing. Because of the heat transfer resistance offered by ash deposits in the furnace chamber in a coal-fired boiler, the mean absorbed heat flux is lower than in gas- or oil-fired boilers, so a greater surface area must be provided. Figure 27-42 shows a size comparison between a coal-fired and an oil-fired boiler for the same duty. 

Pure Commercial Benzene, obtained from coal-tai naphtha, should distil w lthin one degiee (80—Si ), and solidify completely when cooled to 0°. Other tests are as follow s shaken with concentrated sulphuric acid for a few minutes, the acid should not darken, and a drop of bromine water should not be immediately decolourised. A single distillation over a few small pieces of sodium, which absorb any traces of water, is usually a sufficient purification. If the benzene impart a brown or black colour to the sulphuric acid, it must be repeatedly shaken with about 20 per cent, of the acid until the lattev becomes only slightly yellow on standing. This is done in a stoppered separating funnel, and after shaking fora few minutes the mixture is allow ed to settle, and the low er layer of acid diawn off. The benzene is then shaken tw o 01 three times with water to free it from acid, carefully separated from the aqueous layer, and left in contact with fused calcium chloride until the liquid becomes clear. It is then decanted, frozen in ice, and any liquid (carbon bisulphide, paraffins) carefully drained off, and die benzene finally distilled over sodium. 

Projects in the CCT program demonstrated innovative applications for both wet and dry or seniidry FGD systems. The wet FGD systems, which use limestone as an absorber, have met or exceeded the 90 percent SO, removal efficiency required to meet air quality standards when burning high-sulfur coal. The di"y or semidry systems use lime and recycled fly ash as a sorbent to achieve the required removal. 

It is often claimed that a coal-tar-base coating absorbs less water than an asphalt coating and there is evidence in practice to support this claim, but some asphalt enamels in practice have been as good as the best coal-tar enamels. 

The hexamine cobalt (II) complex is used as a coordinative catalyst, which can coordinate NO to form a nitrosyl ammine cobalt complex, and O2 to form a u -peroxo binuclear bridge complex with an oxidability equal to hydrogen peroxide, thus catalyze oxidation of NO by O2 in ammoniac aqueous solution. Experimental results under typical coal combusted flue gas treatment conditions on a laboratory packed absorber- regenerator setup show a NO removal of more than 85% can be maitained constant. 

On the other hand, when the reaction temperature was increased fijrther to 400°C, the reactivity of the absorbent significantly dropped. It was previously reported that for absorbent prepared from coal fly ash, when the absorbent was dried at temperature above 400°C, the reactivity of the absorbent dropped due to the decomposition of the active materials in the absorbent [8]. Since the effect of drying the absorbent above 400°C is similar to exposing the absorbent to reaction temperature above 400°C, therefore it can be concluded that the active materials in absorbent prepared from oil palm ash also decompose at reaction temperature above 400°C resulting in lower reactivity. Apart from that, another possible explanation for the drop in the reactivity of the absorbent at 400°C could be due to the sintering of the absorbent that decreases the surface area of the absorbent. 

Located on the outskirts of big cities, coal gas factories produced enormous amounts of pollutants, particularly ammonia-rich water and coal tar. Some of the coal tar was used to make pitch to waterproof ships, roofs, and rope. Some was turned into creosote for preserving wooden railway ties, used by the millions during the railroad boom of the 1840s. But Europe did not have enough roofs, ships, and railroads to absorb all the coal tar that was being produced, so most of it was dumped, often into rivers. Hofmann was eager to learn more about its composition and find uses for it. 

Certain types of adsorption media have been shown to preferentially adsorb certain contaminants. For example, research has shown that, in some cases, coconut shell-based GAC removes MTBE better than typical coal-based GAC. In addition, synthetic resins have been developed to preferentially adsorb some oxygenates, such as TBA, that are less absorbable by GAC. Often, adsorption processes also take advantage of the biodegradability of MTBE and other oxygenates by promoting bacterial growth on the adsorption. 

Elliot, M. A. et al., Kept. Invest. No. 4169, Washington, US Bin. Mines, 1948 Tests of sensitivity to initiation by heat, impact, shock or ignition sources were made on mixtures of a variety of absorbent materials containing a stoicheiometric amount of 40-70% perchloric acid. Wood meal with 70% acid ignited at 155°C and a mixture of coal and 60% acid which did not ignite below 200° C ignited at 90° C when metallic iron was added. Many of the mixtures were more sensitive and dangerous than common explosives. 

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