The disclosures in the present invention relate to a clean coal production system and method for extracting clean coal from coal refuse (coal waste) produced by coalmines and coal preparation plants (also known as coal washing or processing plants or coal washeries). The disclosed clean coal production system and method can also be used in conjunction with coal washing or preparation plants or with coal mining process to decrease the amount of coal refuse resulted from the coal washing or preparation plants or from coal mining.
Coal is one of major fossil fuel energy sources in the world. Coal is widely used in electric power generation, iron and steel industry, cement industry, gasification, liquefaction, heating, and other purposes. The top coal producing and consuming countries are China, United States, India, Australia, Indonesia, Russia, South Africa, Germany, and Poland.
Using coal as an energy source has certain advantages, e.g., abundant supply, high predictability, low capital investment, available emission-reducing carbon capture and storage (CCS) technologies, convertible into different energy formats, and full-time availability (as opposed to solar and wind). On the other hand, certain disadvantages are associated with the use of coal, e.g., non-renewable, high level of carbon dioxide per British Thermal Unit (BTU), radiation source, other pollutants to air, water, and soil, health concerns from coal mining, coal washing, and emissions, landscape and biomass destruction, and even population resettlement. Regardless of pros and cons from using coal, it will remain a significant part of world's energy sources for the foreseeable future.
The main environmental challenges from coal mining and coal processing (e.g., coal washing or preparation) are coal waste management, land use or reuse, and pollutions. Coalmines and coal processing plants have accumulated millions upon millions of tons of coal refuse (coal waste) across the coal production countries and regions, sometimes over many years or even decades.
The US Environmental Protection Agency (EPA) provides coal refuse's definition as “waste products of coal mining, physical coal cleaning, and coal preparation operations (e.g., culm, gob, etc.) containing coal, matrix material, clay, and other organic and inorganic material” 40 C. F. R., Chapter I, Part 60, § 60.251 (g). Others also described coal refuse as a by-product of coal mining activities, not including overburden, and coal preparation and processing operations, which has been spread on the land.
The coal refuse (coal waste) left behind from coal mining and coal washing operations are hazardous. The residual coal components in coal refuse (coal waste) cannot be recovered by traditional coal mining and coal processing (coal washing) methods, due to technical, economical, and sometimes, historical reasons. Take Pennsylvania, for example, as one of the major coal production states in the US, its commercial coal mining began in 1800. By some estimation, the amount of coal refuse associated with historical mining operations in Pennsylvania may range from 200 million to 8 billion cubic yards. The negative environmental and economic implications of coal refuse (coal waste) last a long time and are still largely in existence in the affected communities of coal mining regions even long after the coalmines and coal washing plants ceased operations for many years. In fact, the older the coal refuse waste, the more deeply buried, higher the level of coal component contained therein, causing more environmental pollutions, the more difficult and expensive to treat the same.
Traditional coal mining operations require the use of large amount of water, the runoff of which is a major contributor to environmental pollutions, coal waste generation, and depletion of a valuable natural resource (e.g., ground and surface water level reduction). In general, raw coal, which contains various impurities and non-coal materials, excavated from underground and surface mines have to be processed in coal preparation and washing plants (coal washeries) to yield marketable and commercially desired coal products. The coal washing plants also require significant amount of water use, similar to coal mining, contributing to environmental pollutions and waste problems.
Coal preparation, washing, or cleaning is a process of removing non-coal materials (defined as containing no tangible heating value) such as soil, rock, or other impurities, from raw coal produced by coal mining. Coal washing process usually involves (a). initial preparation, (b). clean (fine) coal processing, (c). coarse coal processing, and (d). final processing. By coal washing process, raw coal produced from coalmines can be separated into (a). coal gangue, (b). clean coal, (c). coal middlings, and (d). coal slime or coal refuse (also known as coal washing waste).
Coal refuse (slime or waste) takes up tremendous land space that can otherwise be used for more productive purposes. Millions upon millions of tons of coal refuse (slime or waste) have been piled up over the years, sometimes many decades, formed unsightly coal-waste-mountains ubiquitously seen in coal production regions around the world. There have been numerous documented mudslide and spontaneous combustion incidences from coal refuse (waste) sites, further polluting the air, water, and the land, and sometimes causing human fatalities. The coal refuse piles may also attract additional illegal waste dumping. The spontaneous combustion may start as some smoldering that may last for a long time, and then evolve into open flames and raging fire. To extinguish the coal refuse fire and reclaim the coal-refuse-occupied land require millions of dollars.
Efforts have been made in recent years on reclaiming the coal-refuse-occupied land by planting trees or grow other vegetation over the targeted land tracks and develop them into outdoor recreation facilities. These efforts require applying layers, sometimes several feet, of top soil onto the to-be-reclaimed land, probably extracted and removed from somewhere else that can also raise environmental concerns. The main deficiency for these reclaiming efforts is that they do not directly address the root problem itself—the coal refuse (slime or waste), because they neither decrease the amount of the existing coal refuse (slime or waste) nor change its nature or compositions, thus, are mostly on the surface and cosmetic. Often, even after years of the reclaiming efforts, the targeted sites are still lack of trees or vegetation due to their poor growth on such coal refuse infused land.
The invention disclosed herein is to provide a technical solution for extracting the useful coal components from coal mining and coal processing/washing refuse (coal waste). Additionally, the water used in the disclosed invention is recovered, recycled, and reused in a closed setting (ecosystem), thus, not released into the environment in order to minimize pollutions and conserve water.
Specifically, the present disclosures provide a solution directed to the root-cause to the global scale coal refuse (slime) waste problems that long troubled the coal industry for decades, by extracting substantially useful coal components out of the coal refuse (slime) waste. As a result, the present invention can significantly decrease the existing amount of coal refuse (slime) waste, address environmental concerns, as well as provide viable employment and economic revival opportunities to coal producing regions, which have been, in general, in decline for the past few decades, due to more and more stricter rules and regulations implemented by various government agencies on coal mining and coal washing or preparation industry.
A system and method for clean coal production are disclosed. The system and method can be used in a regular coal processing plant, either as a standing alone facility, or coupled with a traditional coal washing plant for treating the resulted coal refuse (slime) waste by extracting coal components out of the coal refuse (slime) waste and turning them into clean (fine) coal products of much higher heating, market, and economic value. Similarly, the system and method disclosed herein can be used to treat coal refuse (slime) waste from coalmines, extracting and generating clean (fine) coal products. The system and method can also be used for reclaiming, reforming, improving, and otherwise increasing the value of coal-waste-occupied land by extracting clean (fine) coal out of the wasteland. The disclosed system and method are designed as a closed setting (ecosystem) so that water as a valuable resource are recovered, recycled, and reused to minimize environmental concerns.
The above mentioned and other features and objects of the disclosures, and the manner of attaining them, will become more apparent and will be better understood by reference to the following descriptions of various embodiments of the invention taken in conjunction with the accompanying drawings.
The particular features, characteristics, and advantages of the provided disclosures for the present invention as well as other objects will become apparent from the following descriptions in connection with the accompanying drawings in which:
Particular screen or sieve series, cyclone separator series, floating selection separator series, and presser-filter series, their combinations and sequence ordering arrangements, are meant to be illustration or exemplary purposes, but not as restrictions or limitations thereof.
The embodiments described herein are not intended to limit the scope of the invention to the precise form disclosed. Rather, the embodiments described herein have been chosen and described to explain the principles of the invention and their applications and practical uses to best enable others skilled in the art to follow the disclosed teachings.
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(b). clean (fine) coal, which shall follow
(c). coal gangue, which shall follow
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(b). neutral coal middlings, which shall follow
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The presently disclosed invention can recover coal components from coal refuse (waste), resulting in clean (fine) coal as products. About 80% of the coal content from the coal washing tailings generated by presently operating coal washing plants, which dispose or otherwise discard the coal tailings as coal refuse wastes with tremendous negative environmental implications. The clean (fine) coal products are valuable commodities, which are very much in demand for the industries such as electric power generation, iron and steel, cement production, heating, just to name a few. The clean (fine) coal production technologies as illustrated in the presently disclosed invention will add value to presently existing coal mining and coal washing operations, increase existing coal industry related job opportunities, improve economics, decrease pollutions to the environment from the existing coal industry globally.
Furthermore, the clean coal technologies disclosed in the present invention can be used to recover clean coal from discarded coal wastes left behind from the past, cumulated over the years or even decades, by coalmines and coal washing plants, which may no longer be in operations, thereby creating much needed new job opportunities, revitalizing local economics, reclaiming hazardous and polluted landmass, and turning the same into landscapes ready to be beautified, used, and enjoyed by many generations to come.
Samples (coal washing tailings delivered from different coal washing plants or different production batches of coal washing tailings delivered from a given coal washing plant) are obtained and tested to determine the initial baseline (or starting point) for their coal content (weight of coal content/total weight of coal washing tailings, expressed in %). Final clean coal (fine coal) products resulted from the presently disclosed invention are measured at their output points (plus screen and minus screen, respectively) and calculated against the initial baseline (starting point) coal content to determine the recovery rate (%). On average, the recovery rate of clean (fine) coal as products from the presently disclosed invention is about 80%, as shown in Table 1 with data points illustrating coal recovery rate of the disclosed invention in comparison with coal recovery rate of traditional coal washing plants
While the present invention has been described as having different embodiments, the invention may be further modified within the spirit and scope of the disclosures herein. This application is therefore intended to cover any variations, uses, or adaptations of the disclosed invention using its general principles. Furthermore, these disclosures are intended to cover such departures from, changes, or substitutions of the present disclosures made by those skilled in the art or as within known or customary practice in the art to which this invention pertains to and which fall within the limits of the appended claims.