Coal slurry wastes

Malone, R., R. Warner, J. L. Woods, and V. P. Evangelou. 1995. Transport of benzene and trichloroethylene through a landfill soil liner mixed with coal slurry. Waste Manag. Res. 12 417-428. 

The bulk of the fine coal that makes up coal slurry wastes is produced in the mine by the miner cutting heads. These fine particles are typically mixed with... 

Large volumes of coal waste slurry are disposed of in surface impoundments. As the slurry remains easily liquefied long after being impounded, it represents a serious hazard if the impoundment fails. An example of this occurred in Martin Coimty, KY, in 2000, when a breakthrough in a coal slurry impoundment released 245 million gallons of slurry into 75 mi of streams, and caused in excess of 37 million in damages. ... 

Unlike other coal slurry applications where the slurry must be kept fluid and pumpable, coal slurry in impoundments needs to be stabilized to prevent flow. Treatments of coal waste slurry, therefore, concentrate on promoting complete settling, strong interparticle interactions and high viscosities so that impoundment breaks will not release the material as a damaging flow. 

Coal Coal Slurries High Explosives Pesticides TNT Waste (Red and... 

Table 2.4 Viability of ITM based membrane process options in power production Oxidation Process Feed Coal, biomass, waste, slurry, etc. Natural gas, gasoline, syngas, etc.

Several investigations were carried out to remove toxic heavy metal ions from waste water by biosorption. Microbial cells loaded with heavy metals were recovered by flotation, e.g. Streptomyces griseus and S clavuUgerus loaded with Pb [108] and Streptomyces pilosus loaded with Cd [109]. In these flotation processes the microbial cells were dead therefore, they are not considered here. The removal of pyritic sulfur from coal slurries such as coal/water mixtures by Thiobacillus ferrooxidans and recovery of this iron-oxidizing bacterium by flotation is a special technique in the presence of high concentrations of solid particles (see e.g. [110]). The flotation of colloid gas aphrons was used for the recovery of yeast in continuous operation [ 111 ] for the recovery of micro algae, and in the presence of flocculants in batch operation [112]. These special techniques are not discussed here. 

Thereafter, the gas flows through a waste heat boiler to generate high-pressure steam in the same way as in the radiant cooler. A scrubber operating partly on recycled and partly on fresh water cools the gas down to ambient temperature and removes the remaining ash particles. Freshwater make-up is necessary as some of the scrubber effiuent has to be withdrawn to prevent a build-up of metal compounds from the coal in the scrubber loop. Most of the scrubber effiuent, partly gas condensate and partly fresh water, is used to prepare the coal slurry. 

It is the most common FGD process—the flue gas is treated with limestone slurry for the sulfur dioxide removal. Approximately 95% of the SOj from the flue gas can be eliminated. The method can be used for medium-to high-sulfur coals. A slurry waste or a saleable slurry by-product is obtained. 

The scope of the fine coal waste issue is dramatic. Today, some 5 -10 percent of the run-of-mine coal produced and sent to preparation plants is discharged as fine coal slurry and disposed of in impoundments. Since 70 percent of the coal mined in the Eastern and Midwestern US is processed in preparation plants, this represents a significant resource [9]. There are over 2,300 waste coal impoundments and settling ponds in the USA today, of which over 1,500 have been abandoned [10]. 

Finally, selective separation and dewatering of one suspended substance in a slurry containing different minerals or precipitates is possible by selectively adsorbing a magnetic material (usually hydrophobic) onto a soHd that is also naturally or chemically conditioned to a hydrophobic state. This process (Murex) was used on both sulfide ores and some oxides (145). More recently, hydrocarbon-based ferrofluids were tested and shown to selectively adsorb on coal from slurries of coal and mineral matter, allowing magnetic recovery (147). Copper and zinc sulfides were similarly recoverable as a dewatered product from waste-rock slurries (148). 

Immiscible wetting in mixers Sol-gel processes Pellet flocculation <0.3 Low Up to 10 ton/hr Wet processing based on flocculation properties of particulate feed Coal fines, soot and oil removal from water Metal dicarhide, silica hydrogels Waste sludges and slurries... 

The SBP slurry-phase bioremediation system can treat a wide range of organic contamination, especially wood-preserving wastes and solvents. A modified version can also treat polynuclear aromatic hydrocarbons (PAHs) such as creosote and coal tar pentachlorophenol (PCP) total petroleum hydrocarbons (TPH) and chlorinated aliphatics, such as trichloroethene (TCE). The technology can be combined with SBP s membrane filtration system to form a soil cleaning system to handle residuals and contaminated liquids. 

Coal liquefaction Fischer-Tropsch synthesis Synthesis of methanol Hydrogenation of oils Alkylation of methanol and benzene Polymerization of olefins Hydrogenation of coal oils, heavy oil fractions, and unsaturated fatty acids Adsorption of S02 in an aqueous slurry of magnesium oxide and calcium carbonate S02 or removal from tail gas Wet oxidation of waste sludge Catalytic desulfurization of petroleum fractions Wastewater treatment... 

In short process lines slurries are readily handled by centrifugal pumps with large clearances. When there is a distribution of sizes, the fine particles effectively form a homogeneous mixture of high density in which the settling velocities of larger particles are less than in clear liquid. Turbulence in the line also helps to keep particles in suspension. It is essential, however, to avoid dead spaces in which solids could accumulate and also to make provisions for periodic cleaning of the line. A coal-oil slurry used as fuel and add waste neutralization with lime slurry are two examples of process applications. 

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