Coal drying method and system

Abstract

The present invention provides methods and systems for reducing moisture in coal, particularly coal fines and other coal streams comprising small diameter particles, using a granular drying material. The invention also relates to novel coal products and intermediates useful in connection with the process. The method and system reduced moisture by contacting the coal with the granular drying material. The granular drying material is selected to be readily separated from the coal fines using a size separation technique such as a sieve screen. The granular drying material is the regenerated, preferably using a process involving heat exchange and cross-flow air. The granular drying material is preferably capable of regeneration and recycling in a continuous process with minimal attrition.

Description

RELATED APPLICATIONS[0001]The present application is a continuation-in-part of patent application Ser. No. 13 / 168,186 entitled “COAL DRYING METHOD AND SYSTEM” filed Jun. 24, 2011 which continuation-in-part of patent application Ser. No. 12 / 924,570 entitled “COAL FINE DRYING METHOD AND SYSTEM” filed Sep. 30, 2010 which claims benefit from U.S. Provisional Patent Application Ser. No. 61 / 247,688 filed Oct. 1, 2009. The contents of these applications are incorporated by reference in their entirety.FIELD OF INVENTION[0002]The present invention relates generally to removing moisture from coal and more specifically to drying coal, coal fines and coal refuse.BACKGROUND OF THE INVENTION[0003]In the continued push for cleaner technology, a concurrent growth trend is the better utilization of existing resources. A common and abundant energy resource is coal. But, there are various concerns and issues associated with coal that challenge the cost-effectiveness and product maximization in the cur...

AI Technical Summary

Benefits of technology

This patent describes a method and system for using granular drying media to dry coal, coal fines and fine coal refuse. By combining the coal with the granular drying media and agitating them, the surface moisture on the coal is removed and the granular drying media is separated from the coal. This process recaptures and utilizes the coal, reducing processing inefficiencies and eliminates waste. The preferred granular drying media are zeolites and desiccants such as activated alumina. Overall, this technology is environmentally friendly and efficient in drying coal.

Problems solved by technology

But, there are various concerns and issues associated with coal that challenge the cost-effectiveness and product maximization in the current industry.

The inclusion of too much moisture in coal is problematic from both a cost perspective and a use perspective.

Current technology is incapable of reducing coal having a size below 28 mesh to a moisture content of 8% or below.

Methods of drying coal fines beyond this point typically employ blowers and heaters which require capital intensive investment, require substantial energy use, and create environmental problems and hazards both from energy use and from aerosolization of the coal fines.

The existing techniques of using coal beyond a moisture content of around 12% typically employs blowers and heaters, which require capital intensive investment, require substantial energy use, and creates environmental problems and hazards.

These hazards are from both energy use and aerosolization of the coal.

Current thermal drying techniques cause the loss and therefore the disposal of a portion of the smallest coal pieces, also referred to as coal fines, because based on current thermal drying techniques, there lacks a known means to retain these dried smallest coal pieces.

This requires an excess cost to dry this coal.

The costs associated with the highest percent of moisture on the finer sized coal are greater than the return achieved by selling this size coal themselves.

As a result, coal fines have been pumped into coal impoundments which represent an environmental hazard and waste of energy resources.

Inclusion of high moisture content increases the weight of the coal, thus having to be sold at a lower price.

The inclusion of excess moisture content reduces the effectiveness of the coal because of energy wasted to evaporate off the moisture.

The lower the moisture content, the greater the expected costs for purchasing coal.

The problem of dewatering coal fines has long eluded the coal industry.

These coal fine impoundments can lead to safety and environmental concerns from run-off and other associated problems.

Although these techniques successfully reduced the water content of coal fines, these technologies still produced coal fines having greater than 20% moisture.

These technologies have only been employed where the use of high temperatures degrade the materials which are sought to be dried, such as foodstuffs and materials that are known to chemically react and / or degrade with heat thereby making conventional thermal drying techniques infeasible.

Severinghaus teaches that heat drying of calcite results in calcination and production of calcine (CaO), which is detrimental to the use of calcite in fillers and extenders.

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