Coal Blending

The quality attributes that are most important in coal blending will differ from one mine site to another.RPM Solutions, based in Lexington, Kentucky, understands coal blending and specializes in it. Coal blending is the process of mixing coals after coal has been mined to achieve quality attributes that are desirable for the coal’s intended application (i.e., steam generation and coking). The blending of coal process is practiced for combustion and gasification, particularly in power generation which is distinguished from blending for coke in the steel industry.

The physical and chemical characteristics of coal are highly variable. Coal characteristics affect nearly every operational aspect of a power plant, including forced outage rate, maintenance costs, auxiliary power requirements, net plant heat rate, emissions and the ability to meet full load. It is becoming more and more common for plants to have to consider accepting coals that do not match the characteristics for which they were originally designed. Since coal characteristics affect almost every area of plant performance and operation, it is necessary to predict, as closely as possible, the physical and economic challenges that will arise when switching coals. Coal blending in its simplest form is the mixing of available coals to produce a blend which combusts well to produce heat and/or power.

The quality attributes that are most important in coal blending will differ from one mine site to another and also depend on how the coal seams vary in quality and their final intended use. Coal blending allows utilities to save on generation costs by combining low grade coal with a higher grade in order to arrive at a certain BTU and sulfur content. Many new plants are being built with the capabilities of blending coal and older plants are being converted to adapt the ability to do so.

The method of coal blending selected depends upon the site conditions, the level of blending required, the quantity to be stored and blended, the accuracy required and the end use of the blended coal. Blending can take place at the coal mine, the power plant, preparation plant or trans-shipment point.

Applying blending techniques goes a long way in reducing the cost of power generation. Low-grade coals can be mixed with high-grade coal, while retaining thermal performance of the boiler. Generally, any two coals can’t just be blended: successful blending occurs with respect to non-additive properties, like the combination reactivity of coal, ash characteristics, grind ability index and selling characteristics of the two coals.

Coal industries are using different types of blending. The most common type is blending on a moving belt which is used for all coal processing industries. Taking an environment-friendly approach in thermal power plants with coal blending requires an understanding of the interaction of inorganic components of coals in the blend process and how it affects ash behavior including its emissivity and thermal conductivity.

While cost is still a high priority, as coal markets evolve and the power sector changes, many plants now also have to consider other factors when deciding on an acceptable blend of coals. Some plants may consider moisture content a more important parameter than ash content and will blend accordingly. RPM Solutions specializes in coal blending. Contact us at www.RPMSolve.com