Coal slurry

D. Blankmeister and Th. Triebert, Dewatering Fltrafme Coal Slurries by Means of Pressure Filtration, Aufbereitungstechnik Nr. 1/1986, pp. 1—5. 

Dry soHds, such as as-rnined ore, emshed ore, and dried concentrates, are transported using tmeks, rail cars, ore passes, conveyor belts (see Conveying), or slurry pipelines (qv) as dictated by the logistics, distances involved, and capacity. Within the mill, conveyor belts are more common, but for fine particles, tailings, and coal, slurry transportation is more typical. 

Coal Slurry Pipelines. The only operating U.S. coal slurry pipeline is the 439-km Black Mesa Pipeline that has provided the 1500-MW Mohave power plant of Southern California Edison with coal from the Kayenta Mine in northern Arizona since 1970. It is a 457-mm dia system that aimuaHy deHvers - 4.5 x 10 t of coal, the plant s only fuel source, as a 48.5—50% slurry. Remote control of slurry and pipeline operations is achieved with a SCADA computer system. In 1992 coal deHvery cost from mine to power plant was calculated to be 0.010/tkm ( 0.015/t-mi) (28). 

The former Soviet Union constmcted a 262-km, 508-mm dia experimental coal slurry line between the Belovo open-pit coal mine in Siberia s Kuznets basin to an electric power plant at Novosibirsk, using technology developed by Snamprogetti. Testing began in late 1989 and tentative plans call for constmction of two much larger slurry pipelines, each 3000-km long, with capacity to move a total of 33 x 10 t/yr to industrialized areas near the Ural Mountains (27,33). 

Fig. 16. Flow sheet for oil agglomeration of fine-coal slurries (96).

Still another process, called BI-GAS, was developed by Bituminous Coal Research in a 73 t/d pilot plant in Homer City, Peimsylvania. In this entrained-bed process, pulverized coal slurry was dried and blown into the second stage of the gasifier to contact 1205°C gases at ca 6.9 MPa (1000 psi) for a few seconds residence time. Unreacted char is separated and recycled to the first stage to react with oxygen and steam at ca 1650°C to produce hot gas and molten slag that is tapped. 

L. E. Burgess and co-workers, 5th International Symposium on Coal Slurry Combustion and Technology, Tampa, Ela., 1983, pp. 255—268. 

Coal feed form Dry coal Coal slurry Dry coal Dry coal Dry coal Dry coal... 

Direct-Liquefaction Kinetics All direct-liquefac tion processes consist of three basic steps (1) coal slurrying in a vehicle solvent, (2) coal dissolution under high pressure and temperature, and (3) transfer of hydrogen to the dissolved coal. However, the specific reac tion pathways and associated kinetics are not known in detail. Overall reaction schemes and semiempirical relationships have been generated by the individual process developers, but apphcations are process specific and limited to the range of the specific data bases. More extensive research into liquefaction kinetics has been conducted on the laboratory scale, and these results are discussed below. 

Alcorn and Sullivan (1992) faced some specific and difficult problems in connection with coal slurry hydrogenation experiments. Solving these with the falling basket reactor, they also solved the general problem of batch reactors, that is, a good definition of initial conditions. The essence of their... 

Coal Slurries - Two component treatments prove to be effective on a commercial scale for coal slurry flocculation. The use of encapsulated floccuiant suspended in a counter charged floccuiant provides the robusmess of traditional dual component systems, but with additional performance advantages, which include reduction in filter cake moisture content and an increased throughput rate. Figure 5 illustrates the typical filter cake moisture content obtained by a conventional treatment system compared to the encapsulated treatment system using coal tailings as the substrate. 

Severe Severely corrosive, severely abrasive or severely plugging (e.g., wet hydrogen chloride, coal slurry, heavies, uninhibited monomer). 

Coal slurry pipelines have been widely discussed, but few slurry pipelines have been built. In addition to the Black Mesa operation in Arizona, a 38-mile (61-km) pipeline was built by the Soviet Union, and a 108-mile (173-km) pipeline in Ohio was mothballed in 1963 after six years of operation. It is arguable to what extent the limited use of slurry pipelines is due to economics or to political opposition from rail car-... 

Carbon steels Coal/water. Coal slurry transportation. 

Environments are either gases or liquids, and inhibition of the former is discussed in Section 17.1. In some situations it would appear that corrosion is due to the presence of a solid phase, e.g. when a metal is in contact with concrete, coal slurries, etc. but in fact the corrosive agent is the liquid phase that is always present. Inhibition of liquid systems is largely concerned with water and aqueous solutions, but this is not always so since inhibitors may be added to other liquids to prevent or reduce their corrosive effects — although even in these situations corrosion is often due to the presence of small quantities of an aggressive aqueous phase, e.g. in lubricating oils and hydraulic fluids (see Section 2.11). 

In the hydraulic transport of solids through steel pipelines, inhibitors of the sodium-zinc-phosphate glass type have been shown" to be effective. In the case of coal slurries the polyphosphate type was rejected because the de-oxygenating action of the coal lowered the inhibitor effectiveness. Hexavalent chromium compounds at 20 p.p.m. were more effective". ... 

Run No. Total Time of Coal Slurry Feed, hrs Total Coal Feed, tons Methanation Section Operating Time, hrs... 

SH Gehrke, LH Lyu, K Bamthouse. Dewatering fine coal slurries by gel extraction. Sep Sci Tech 33 1467-1485, 1998. 

In thermal processes the formation of asphaltols always precedes other reactions such as major heteroatom rejection and distillate formation. In fact, in the SRC process bituminous coals are actually dissolved by the time the coal slurry exits the preheater (4,11). This has recently been demonstrated at the SRC process development unit (PDU) in Wilsonville, Alabama (11) (see Figure 2). 

The experimental apparatus consisted of a 1-liter, stirred autoclave (AC1), used to preheat the solvent-coal slurry, connected to a 2-liter, stirred autoclave (AC2), equipped with an internal heating coil to bring the solvent-coal slurry rapidly to a constant reaction temperature, and a third autoclave (AC3), equipped with a cooling coil to act as a quench vessel (Figure 1). This allowed direct determination of the material lost in... 

In the solvent-refined coal pilot plant at Wilsonville, Alabama, the coal slurry is heated to reaction temperature in 3-4 minutes residence time in the preheater. The slurry is then held in the dissolver for an additional 40 minutes before it is filtered to obtain specification solvent-refined coal. By bypassing the dissolver and going directly to the filters, samples of short-contact time (SCT) SRC were produced from Illinois 6 (Monterey) and West Kentucky coals. 

You must determine the horsepower required to pump a coal slurry through an 18 in. diameter pipeline, 300 mi long, at a rate of 5 million tons/yr. The slurry can be described by the Bingham plastic model, with a yield stress of 75 dyn/cm2, a limiting viscosity of 40 cP, and a density of 1.4 g/cm3. For non-Newtonian fluids, the flow is not sensitive to the wall roughness. 

A pipeline has been proposed to transport a coal slurry 1200 mi from Wyoming to Texas, at a rate of 50 million tons/yr, through a 36 in. diameter pipeline. The coal slurry has the properties of a Bingham plastic, with a yield stress of 150dyn/cm2, a limiting viscosity of 40 cP, and an SG of 1.5. You must conduct a lab experiment in which the measured pressure gradient can be used to determine the total pressure drop in the pipeline. 

A coal slurry that is characterized as a power law fluid has a flow index of 0.4 and an apparent viscosity of 200 cP at a shear rate of 1 s-1. If the coal has a specific gravity of 2.5 and the slurry is 50% coal by weight in water, what pump horsepower will be required to transport 25 million tons of coal per year through a 36 in. ID, 1000 mi long pipeline Assume that the entrance and exit... 

A coal slurry is found to behave as a power law fluid, with a flow index of 0.3, a specific gravity of 1.5. and an apparent viscosity of 70 cP at a shear rate of 100 s 1. What volumetric flow rate of this fluid would be required to reach turbulent flow in a 1/2 in. ID smooth pipe that is 15 ft long What is the pressure drop in the pipe (in psi) under these conditions ... 

A coal slurry is to be transported by pipeline. It has been determined that the slurry may be described by the power law model, with a flow index of 0.4, an apparent viscosity of 50 cP at a shear rate of 100 s-1, and a density of 90 lbm/ft3. What horsepower would be required to pump the slurry at a rate of 900 gpm through an 8 in. sch 40 pipe that is 50 mi long ... 

A coal slurry pipeline is to be built to transport 45 million tons/yr of coal slurry a distance of 1500 mi. The slurry can be approximately described as Newtonian, with a viscosity of 35 cP and SG of 1.25. The pipeline is to be built from ANSI 600 commercial steel pipe, the pumps are 50% efficient, energy costs are 0.06/... 

You must chose a centrifugal pump to pump a coal slurry. You have determined that the pump must deliver 200 gpm at a pressure of at least 35 psi. Given the pump characteristic curves in Appendix H, tell which pump you would specify (give pump size, speed, and impeller diameter) and why What is the efficiency of this pump at its operating point, what horsepower motor would be required to drive the pump, and what is the required NPSH of the pump The specific gravity of the slurry is 1.35. 

A slurry pump operating at 1 atm must be selected to transport a coal slurry from an open storage tank to a rotary drum filter, at a rate of 250 gpm. The slurry is 40% solids by volume and has an SG of 1.2. The level in the filter is 10 ft above that in the tank, and the line contains 400 ft of 3 in. sch 40 pipe, two gate valves, and six 90° elbows. A lab test shows that the slurry can be described as a Bingham plastic with v = 50 cP and t0 = 80dyn/cm2. 

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