Blended firing of coal and lignite, ICSC/316

Many emerging economies depend on coal for secure, affordable and reliable electricity generation and supply. Therefore, it is vital to ensure that coal is used efficiently with minimum environmental impacts. Firing indigenous lignite with high quality coals in countries like India, Pakistan and Bulgaria can help to cut the cost of energy generation and keep generating electricity at high efficiency and low emissions to provide energy at an affordable price. In general, coal quality is declining as reserves become depleted, so more lignite, subbituminous and high ash bituminous coals are being fired in power plants, which can create complications, such as slagging and fouling. The disadvantages of firing lignite may be reduced by blending it with higher quality coals. Conversely, adding some lignite to higher quality coals may be used to reduce fuel costs. This report summarises commonly used coal blending methods and where blending can be carried out at coal-fired power plants. Coal blending methods include stockpile, bin, belt and furnace blending and can happen onsite or offsite at a power plant. Some coal properties, such as proximate and ultimate analysis data and the heating value, remain additive after blending. The effect of some physical properties on blending, such as grindability, ash fusion temperature, swelling, and combustion characteristics, is harder to predict. The main issues related to firing lignite blends at power plants are blending ratio, boiler and mill performance, combustion characteristics, and ash deposition. Firing low ratio lignite blends (less than 15%) can be carried out without plant modification at coal-fired power plants. Case studies of firing lignite blends include examples from Bulgaria, China, India, Pakistan, and the USA. Firing lignite with coal can play a role in the achievement of some of the United Nations Sustainable Development Goals, particularly, Goal 7 affordable and clean energy, Goal 8 decent work and economic growth, Goal 9 industry innovation and infrastructure, Goal 12 sustainable consumption and production patterns, and Goal 13 climate action.