Coal slurries pipeline transport

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/... 

Coal Slurry Pipelines. The first patent covering the pumping of coal and water dates back to 1891. In 1914. the first commercial transport of coal in water was carried out in England, when a short 8-inch (20-centimeler) pipeline was used to cany coal from river barges to a power plant. Thereafter, several proposals were submitted for the long distance transport of coal from mine to market in the eastern United States, but failed to materialize for several reasons, not the least of which were technical problems. Intensive research into slurry transport was continued and, by 1957. technology and engineering had advanced In the point where the... 

Coal slurry pipelines have been constructed in severaJ countries, including a 38-mile (61-kilometer) 12-inch (30.4-centimeter) diameter pipeline m Russia, a 51 -mile (82-kilometer) pipeline in Poland, as well as Olliers in Prance and other locations in Europe. The feasibility of slurry transportation depends upon Ihc resolution of a number of variables, rhe most important of which from a hydraulic standpoint are (I) Size consist (2) velocity and (3) concemrauon. The selection of a proper size eonsisi (gradation) is important in order that homogeneous flow can he achieved at prudent operating velocities. For coal slurry, such a consist is on the order of 8 mesh by 0 (approximately 0.1-inch (2.5-millimeter) particle size to dust) Homogeneous flow (solids evenly distributed across the pipe diameter) is important if excessive wear in the bottom of the pipe is to be avoided and stable operation achieved. 

Another important factor in the availability of coal is an adequate supply of transportation facilities, particularly railroad hopper cars. There is little or no storage at the mines except for unit train shipments, so mines generally cannot operate without an adequate supply of coal cars, wluch determines the number of days of active mine operation. Because of the close a Bnity of coal and rail transportation, the deterrents to expanded coal productive capacity also affect the development of new transportation facilities. Of considerable importance in the future will be an increase in the number of unit trains, which help to reduce transportation costs and the potentials for more coal slurry pipelines and for mine-mouth generating plants for the extra-high-voltage transmission of coal-produced electricity. 

Coal slurry pipelines. Slurry is used for transporting the coal through pipelines, but the coal is dewatered at the end before utilization. The slurry is unstable, and the particles are kept in suspension by the turbulence of the flow as they travel through the pipeline. The particles rapidly settle out of suspension once the slurry stops moving. 

A coal slurry pipeline is a system for transporting solid coal particles in a liquid carrier. Long-distance coal slurry pipelines are an alternative to railroad transport, and their practicality and economics are largely dependent on land ownership, terrain, water availability and water contamination concerns, political considerations, and coal demand. An example of pipeline transport is the 440 km Black Mesa pipeline, which was completed in 1970 and is currently the only long-distance coal slurry pipeline operating in the United States. Slurry pipelines are also used over shorter distances to transport material within a processing facility. 

The way that coal is transported to where it will be used depends on the distance to be covered. Coal is generally transported by conveyor or truck over short distances. Trains and barges are used for longer distances within domestic markets, or alternatively coal can be mixed with water to form a coal slurry and transported through a pipeline. 

Another method to transport coal is through a slurry pipeline. This connects a mine with a power plant where the coal is used to generate electricity. Coal slurry pipelines use a slurry of water and pulverized coal. The ratio of coal to water is about 1 1. 

Coal slurry pipelines are potentially the least costly available means for transporting coal to any location, measured in economic terms. Whether this is true with reference to any particular pipeline can only be determined by detailed evaluation of the conditions of the route. The current coal transportation scenario does not offer any choices between slurry pipelines and railroad, which undoubtedly will necessarily minimize the cost of transporting coal. In this context, the present times warrant assessment of the potential economic, environmental, and social implications of coal slurry pipeline development and transportation of coal through it. 

Brtxrks, D. A. and C. H. Dtxlwell. 1985. The Economic and Technical Evaluation of Slurry Pipeline Transport Techniques in the International Economic Coal Trade. In 10th International Conference on Coal Technology, Lake Tahtre, Nevada. Washington, D.C. Coal and Slurry Technology Association. 

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. 

The usual means of transporting coal are railroad, barge, tmck, conveyer belt from mine to plant, and slurry pipelines (2,4) (see Transportation). In 1988 769 X 10 t of coal was transported to United States destinations of this, 57.5% was shipped by railroad, 16.0% by barge, 12.3% by tmck, and 14.2% by conveyer, slurry pipeline, and other methods (2). Electric utihties consumed 85.83% of the coal transported in the United States in 1988 (2). 

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". ... 

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 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 ... 

The coal reserves are very large, but the mobility of coal is difficult (by truck, train, or shiploads) as compared to oil and gas (by pipelines). In order to transfer coal in pipelines, one has to make coal slurries. Coal is finely divided, and after that, it is dispersed in water or oil such that a suitable slurry for pipeline transfer can be suitably achieved. Something similar is already being developed in the shale oil industry (in Canada). Coal can thus be transported through pipelines after being dispersed in conjunction with water, oil, etc. This industrial development is based on many aspects related to the surface properties of coal. 

Coal-water slurry transport has been most thoroughly investigated and implemented. One of the earliest lines was 108 miles long, 10 in. dia, 50-60 wt % solids up to 14 mesh, at velocities of 4.5-5.25 ft/sec, with positive displacement pumps at 30-mile intervals. The longest line in the United States is 273 miles, 18 in. dia and handles 4.8-6.0 million tons/yr of coal it is described in detail by Jacques and Montfort (1977). Other slurry pipeline literature is by Wasp, Thompson, and Snoek (1971), Bain and Bonnington (1970), Ewing (1978), and Zandi (1971). 

E. Jacques and J.G. Montfort, Coal transportation by slurry pipeline, in Considine (Ed.), Energy Technology Handbook, McGraw-Hill, New York, 1977, pp. 1.178-1.187. 

The world-wide knowledge in design, construction and operation of hydraulic pipeline systems based on experimental investigation and operational experiences as well as on theoretical calculations has shown the efficiency and prospect of the pipeline transport of coal in comparison with other kinds of transport. However, at a level of technical projects a series of weaknesses and/or imperfections in contemporary used systems of the coal pipelining with water used as a carrier liquid have been detected. One of them is a rather difficult, energy consuming and expensive process of dehydration of coal slurry before combustion. Besides, transport of a great quantity of ballast - the carrier water - also requires considerable power inputs and usually also expensive water treatment before reutilization or... 

The first way is pipeline transport of concentrated coal-water slurry. It assumes that utilisation of coal particle distribution preparation and/or using the various additives can substantially increase mass concentration of coal-water slurry till 70-80 %. For example, Black Messa Pipeline realised in USA transports 4.8 million tons of coal per year over the distance 439 km from the colliery in North Arizona to power plant Mohave near the border of Nevada and California with mass ratio of coal to water about 1 1, without using any additives, [5]. Recently, in the USA, Italy, China, Russia and other countries several coal pipelines were already realised. Even Oil and gas should be effectively transported as hydrate slurries, [6],... 

Based on the above mentioned, the programme of theoretical and experimental investigation of the main parameters of coal-methanol (or its water solution) mixture pipeline transport should be opened. As the first step of the programme the comparison of power consumption (dependency of hydraulic gradient I on slurry flow velocity V and solid concentration Cs) for the pipeline transport of coal-water mixture and coal-methanol solution mixture was realised. The special laboratory measurements were made to define unknown input data of semi-empirical relationships, i.e. the limit volumetric concentration Cm and the coefficient of mechanical friction of coal in the water or water-methanol solution ka. The resultant comparison of the hydraulic gradient I of the coal-water and coal-methanol solution mixture flow is presented in Figure 2, where density of coal was pc = 1480 kg/m3, diameter of the pipe was D = 0.103 mm, the maximal grain size of coal dmax was less than 0.25 mm, volumetric concentration - C = 20 %. 

It follows from economical comparison that coal-log pipeline is cheaper than truck transport for distances longer than 65 km and pipe diameter D = 200 mm. For D = 500 m even for distance over 25 km. Compared with railway, the transport cost is on the level of unit trains. For large quantity of coal it could be even less. Another advantage is given by fact that length of pipeline is usually at least about 30 % lower than that of the railway. From environmental protection point of view, capsule pipeline, similarly as slurry pipeline, is dust free and noiseless. In spite of these advantages the utilisation of coal-log pipeline system could expect only for transport of coal from new mines to power stations, especially in mountains areas without railways and highways or in heavy populated and industrial areas, where railway is overloaded. 

As follows from Figure 4, for coarse coal transport the power consumption of slurry pipelining reaches from 300 % to 100 % higher values than that in case of hydraulic capsule pipeline transport. The energy reduction increases with reduction of the operational velocity. 

Except traditional slurry transport of coal as coal-water slurry or coal-water fuel, pipeline transport of coal in hydrocarbons seems to bring some advantage especially for arctic areas. 

Slurry pipeline pipeline that can transport a coal-water mixture for long distances. 

Unlike coal slurry fuels, which are utilized in a fluid form, coal transported by pipeline is used as a solid after dewatering. As a result, it does not need to be stable when stored in tanks, and it is not so critical that its solid loading be maximized. The following variables are important for a pipeline system ... 

Once the coal slurry has been transported to its destination by pipeline, it is dewatered for utiliza-tion.f Chemical additives are not normally used in slurry pipelines, as they would be an unnecessary added cost and a possible source of water contamination. It is important to monitor the quality of the water removed from the slurry, as it could contaminate waterways if it dissolves harmful materials before being released. 

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