Cement is critical to the construction industry – mixed with water and gravel it forms concrete, a key construction material.
To produce cement, energy is required. Coal is an important source of the energy needed. A high-temperature kiln, often fuelled by coal, heats the raw materials of calcium carbonate (generally in the form of limestone), silica, iron oxide and alumina to a partial melt at 1450°C, transforming them chemically and physically into a substance known as clinker. This grey pebble-like material comprises special compounds that give cement its binding properties. Clinker is mixed with gypsum and ground to a fine powder to make cement.
Coal combustion products (CCPs), such as Fly Ash also play an important role in cement manufacture and in the construction industry generally.
200-450kg of coal is needed to produce 1 tonne of cement
of the energy used to produce aluminium comes from coal
of hydrogen production comes from coal-to-gas processes
Coal is a key energy fuel in the production of aluminium – a non-ferrous metal known for its lightweight properties and widely used in cars, trains, and airplanes to reduce the weight of these vehicles and their energy consumption. Coal accounts for over 60% of the energy used to produce aluminium.
Coal-derived fuels, as well as coal-based electricity, play a significant role in responding to the growing energy needs of the transport sector. Not only is coal an important raw material and source of primary energy for the manufacturing of materials used to build transport infrastructure, coal-based electricity has a role to play in supporting the electrification of the transport sector.
Liquid fuels from coal can provide a viable alternative to conventional oil products and can be used in the existing supply infrastructure. Several coal-to-liquids (CTL) demonstration plants are being developed in China, whilst in South Africa liquid fuels derived from coal provide 30% of South Africa’s transport fuel requirements and CTL plants produce more than 160,000 barrels of liquid fuel per day from coal.
Hydrogen is used daily as a gas and liquid by many industries, including the petroleum industry, transport and in manufacturing processes for producing chemicals, foods and electronics.
Coal gasification offers a versatile and clean method of converting coal into hydrogen and other valuable products. Gasification breaks down the coal into its basic chemical components. In modern gasifiers, coal is typically exposed to steam and carefully controlled amounts of air or oxygen under high temperatures and pressures. Under these conditions, molecules in coal break apart, initiating chemical reactions that typically produce synthesis gas (syngas), hydrogen, carbon monoxide and other gaseous compounds. The hydrogen can then be captured and stored. 20% of hydrogen production comes from coal-to-gas processes.
Japan and Australia are pursuing hydrogen production strategies using lignite as the primary source product.
- Japan’s ‘Basic Hydrogen Strategy’ plans to use lignite fuels that are decarbonised by gasification and catalytic conversion, providing hydrogen fuel.
- A proposed lignite gasification project in Australia would use the production of synthetic gas from burning coal under high pressure, then converting the carbon monoxide generated into carbon dioxide with steam and separating out the hydrogen.
Further non energy uses
Other important users of coal include alumina refineries, paper manufacturers, and the chemical and pharmaceutical industries.
Coal is an essential ingredient in the production of specialist products, from activated carbon used in filters for water and air purification and in kidney dialysis machines to carbon fibre, the extremely strong but light weight material used in construction.
It is also used in the production of silicon metal used to produce silicones and silanes, which are, in turn, used to make lubricants, water repellents, resins, cosmetics, hair shampoos and toothpastes.
Several chemical products can be produced from the by-products of coal in the coal-to-chemicals (CTC) industry. Refined coal tar is used in the manufacture of chemicals, such as creosote oil, naphthalene, phenol, and benzene. Ammonia gas recovered from coke ovens is used to manufacture ammonia salts, nitric acid and agricultural fertilisers. Thousands of different products have coal or coal by-products as components: soap, aspirins, solvents, dyes, plastics and fibres, such as rayon and nylon.