Control coal preparation

J. L. Anastasi and co-workers, 5th Annual Coal Preparation, Utilisyation and Environmental Control Contractors Conference, U.S. Department of Energy, Pittsburgh, Pa., July 31—Aug. 3, 1989. 

Currently, about 70 percent of the coal mined east of the Mississippi River is cleaned in commercial preparation plants (27). This includes both metallurgical and steam coal. Although coal cleaning has not traditionally been a means to control SO2 emissions but rather has been a way to control coal quality, it can... 

Our goal is to gradually replace all coal and fossil fuel power plants with renewable energy ones, but while they exist (and probably will for most of this century), it is very important to reduce the damage they cause by optimizing their operation. In the United States, there are about 1000 coal preparation plants and coal-fired power plants. One key consideration in operating coalburning facilities is the control of C02 and sulfur dioxide (S02) emissions to the atmosphere. The characteristics of coal are monitored for environmental protection, quality assurance, and process control purposes. 

The schedule leading to mechanical completion in the fourth quarter of 1979 is shown in Figure 3. The control house is scheduled for completion in May. Final electrical facilities including substations and interplant lines are scheduled for completion in June. Coal preparation facilities and operational tankage are to be commissioned in August followed by completion of the solvent hydrogenation section in October. Final mechanical completion will be accomplished with turnover of the liquefaction reactor and fractionation sections, and is projected for mid November. 

The operating experience at Moss No 3 clearly indicates that the Sortex Ash Monitor is a very useful tool and that it possess sufficient reliability and accuracy to be suitable for control of plant circuitry Through use of a correlation equation and careful calibration, the system should be able to provide the accuracy required to meet the quality control requirements of the coal preparation industry. 

This plant is a multi-boiler complex with 1600 megawatt capacity The CONAC system will be used in connection with a consent agreement involving environmental regulations, compliance schedules, and methods of achieving compliance for sulfur dioxide and particulate emissions While it seems most desirable to control coal quality at the mine or at a preparation plant, the important control point for a utility is at the delivery area at the power station TVA s initial effort will concentrate on the use of the "Sulfcoalyzer to monitor coal as it is delivered A CONAC system has not been installed at any coal preparation plant ... 

Two installations of the MDH "Elemental Analyzer" are planned, one in a coal application and a second unit in an oil blending facility (12) The coal application is in the Homer City, Pennsylvania, coal preparation plant currently under construction The analyzer system will provide a feedback signal that will be used to control the specific gravity of the heavy media coal cleaning operations The installation was scheduled for Spring, 1981 The unit cost 300,000. 

Most coal preparation plants use Instrumentation to inform the control room operator of equipment status and guide the employees within the plant in the manual adjustment of the set points on the process equipment. Many unit operations are not equipped with any instrumentation and successful implementation of these unit operations relies totally upon the experience of an employee charged with the responsibility of monitoring specific pieces of process equipment. New plants are being designed with increased levels of automation and on-line instrumentation however, the investment in instruments is only a small fraction of comparable investments in other process industries. For example, the project team visited two modern coal preparation plants in the Appalachian coal fields which cost 75,000,000 and the total on-line instrumentation investment was approximately 150,000. 

Several quality control devices are available and the development status has been summarized in a previous section Laboratory studies indicate that the precision and accuracy of these devices are adequate to meet product certification needs Fielding testing of these units in the coal preparation plant environment is required to demonstrate their usefulness and economic viability ... 

The development status of process control instrumentation lags that of the quality control instruments significantly Nuclear density gauges function in the coal preparation plant environment The slurry concentration meter has application in the intermediate and fine sized coal cleaning circuits and needs to be tested in a preparation plant Other devices, such as ash monitors to control the operation of heavy media baths or jigs are not available and instruments developed for other process industries are not suitable for use in coal preparation plants Modeling studies of the various unit operations are required in order to ascertain the fundamental parameters required to automate the control of these systems Primary process control instrument needs include ash, sulfur, and moisture monitors secondary needs include an on-line washability and ash fusion measurement ... 

Fauth, G., "On-Stream Determination of Ash and Moisture Content in West German Coal Preparation Plants , Proceedings of the 1980 Symposium on Instrumentation and Control for Fossil Energy Processes, Virginia Beach, VA, 1980. 

All of the materials described earlier are combined with the coal to form the ROM feed. Coal, as referred to earlier, denotes the portion of the feed that is desired for utilization. These are the characteristics that can be controlled by preparation. 

Coal preparation processes can improve the ROM coal to meet market demands, as limited by the inherent characteristics of a given coal. The top size of the ROM can be reduced to any size specified, although control of the varying size increments can be poor, depending on the amount of crushing required. 

Coal sampling is an important part of the process control in a coal preparation plant. A grab sample is a one-off sample of the coal at a point in the process stream, and tends not to be very representative. A rontine sample is taken at a set frequency, either over a period of time or per shipment. Coal sampling consists of several types of sampling devices snch as a crosscut sampler to mimic the stop belt sample (Speight, 2005) which designate the manner in which coal must be sampled. A crosscut sampler mounts directly on top of the conveyor belt. The falling stream sampler is placed at the head section of the belt. 

Burchfield, J.W. 1993. Automated flotation control at Jim Walter resource. Mining Division. In Coal Prep 93, Proceedings of Tenth International Coal Preparation Exhibition and Conference. Lexington, KT, May,... 

Fonseca, A.G., Meenan, G.R, and Oblad, H.B. 1993. Automatic control coal flotation and dewatering processes. Coal Preparation, 17 73-83. 

Luttrell, G.H., Kohmuench, J.N., and Yoon, R.H. 2000. An evaluation of coal preparation technologies for controlling trace element emissions. Fuel Processing Technology, 65/66 407-422. 

Coal preparation plants invariably contain various types of active machinery, in addition to large throughput tonnages of free-falling solids, and have long been recognized as presenting a serious noise problem. Most of the noise control measures may be classified broadly into measures that... 

On September 25, 2009, the United States Environmental Protection Agency (USEPA) set more stringent emissions standards for coal preparation and processing facilities. The final rule, according to USEPA, reflects improvements in air emission control technologies that have been developed since the new source performance standards (NSPS) for these sources were first issued in 1976. 

New, modified and reconstructed coal preparation and processing plants will need to install controls or utilize work practices to meet the revised limits. 

Storage of coal at coal preparation plants is not practiced to the same extent as it was decades ago. The active principles in reducing coal storage at coal preparation plants were (1) fugitive dust and (2) runoff control. 

Harding, N.S. and Owens, W.D, 1994. "The Utilization of Waste Tire-Derived and Railroad-Tie-Derived Fuels in Coal-fired Stoker Boilras, 10 Annual Coal Preparation, Utilization and Environmental Control Contractors Conference, Pittsburgh, PA. 

Helfritch, D. J., Bortz, S. J., and Beittel, R., 1991, Dry Sorbent Injection for Combined SO2 and NO, Control, Seventh Annual Coal Preparation, Utilization, and Environmental Control Contractors Conference—Proceedings, Pittsburgh, PA, July 15-18, pp. 223-230. 

Charcoal—sulfur processes need low ash hardwood charcoal, prepared at 400—500°C under controlled conditions. At the carbon disulfide plant site, the charcoal is calcined before use to expel water and residual hydrogen and oxygen compounds. This precalcination step minimises the undesirable formation of hydrogen sulfide and carbonyl sulfide. Although wood charcoal is preferred, other sources of carbon can be used including coal (30,31), lignite chars (32,33), and coke (34). Sulfur specifications are also important low ash content is necessary to minimise fouling of the process equipment. 

Recent trends in protective coatings used on buried pipelines have been away from reinforced hot applied coal tar and asphalt enamels and butyl rubber laminate tapes, particularly where applied over-the-ditch . The more recently developed coatings based on fusion bonded epoxies, extruded poly-ethylenes, liquid-applied epoxies and polyurethanes, require factory application where superior levels of pipe preparation and quality control of the application process can be achieved. 

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