Waste heat is generated by fuel combustion or chemical reaction, which is then “dumped” into the environment. The strategy of how to recover this heat depends partially on the temperature of the waste heat gases and the economics involved. Hot flue gases are generated from boilers, kilns, ovens and furnaces (sponge iron kilns, coke oven gas, blast furnace gas, steel plants, sinter plants, etc.). If some of this waste heat is recovered, a considerable amount of primary fuel could be saved.
According to Technavio, market research analysts envisage the global waste heat recovery (WHR) market to grow steadily at a compound annual growth rate of 7 per cent by 2021. The primary growth factor is the rising power consumption due to the increasing global population. Besides, WHR systems in process plants like cement, steel, chemicals, fertilisers and petrochemicals help improve their efficiency. Also, the installation of WHR systems in existing plants is cheaper than building new power plants.
New industries are coming up with pre-installed heat recovery units, while the older plants are incorporating WHR technologies to lower fuel consumption and realise cost savings. Even though WHR is a proven technology, its uptake, particularly in the cement industry, has been limited, except in China. Currently, there are a range of commercially proven and mature WHR power systems ranging from classic Rankine-cycle steam-based installations to organic Rankine cycle and Kalina cycle WHR power systems. As of 2016, there were over 850 WHR power installations across the world with China in the lead (739 WHR installations), followed by India (26) and Japan (24 installations).
During 2016, the chemical industry was the main end user in the WHR market. The increasing demand for petrochemicals, pesticides and fertilizers, and synthetic rubber will contribute to the growth of this market segment in the coming years. This is followed by petroleum refining and paper industries. Globally, the rise in population increases the demand for education, which will in turn drive the paper industry. For instance, India has one of the leading higher education markets (accounting for more than half of the country’s education market) in the world.
The Americas will be the major revenue contributor to the WHR market throughout the forecast period, driven by the introduction of stringent emission regulations and the need for efficiency in countries such as the US and Canada.
Potential in India
The potential of WHR technology in India is huge, particularly from the cement industry. Cement plants have a considerable amount of waste heat available (35 per cent of heat is lost primarily from the preheater and cooler waste gases), which can be recovered and used for generating power. However, this heat is available at a very low temperature, which results in high equipment costs and thus, slow project returns on investment.
Being one of the largest cement producers in the world, second only to China, Indian cement plants are yet to reach high efficiency levels in terms of heat recovery. As of 2014-15, only 18 cement plants had installed WHR systems, with 237 MW of power being produced. So far, only around 35 per cent of the available heat potential has been recovered.
According to ISGEC Heavy Engineering, the cement industry accounts for 5 per cent of global CO2 emissions and WHR power plants can help reduce their impact on the environment. As per Thermax, one of the largest WHR power plants in the cement industry commissioned in India utilises hot exhaust gases released by the cement plant to produce 18 MW of power. This has reduced coal consumption at the captive power plant and lowered greenhouse gas emissions by nearly 122,000 tonnes per year, considering a plant load factor of 90 per cent.
In sum, concerns about rising power prices and supply reliability have led many Indian industries to install on-site captive power plants and more recently, WHR systems. Although the latter involves relatively high initial capital expenditure, the overall lifetime cost of this “in-house” source of energy proves to be much lower. This increases the plant’s profitability over time and makes it less susceptible to fluctuations in fuel pricing.