Introduction:
Producing electricity in coal power plants can take place in a number of ways with varying degrees of efficiency. In conventional coal-fired plants coal is first pulverised into a fine powder and then combusted at temperatures of between 1300 and 1700 C. This process heats water in tubes in the boiler so that it becomes steam at a pressure of around 180 bar and a temperature of 540oC. This steam is passed into a turbine to produce electricity (see Figure 1). Pulverised coal power plants account for about 97% of the world's coal-fired capacity (IEA 2008, p. 225). The average net efficiency (energy produced minus energy used within the plant) is around 35%, which means that 35% of the energy in one unit of coal is transferred into electricity. Pulverised coal power plants can have a size of up to 1000 MW and are commercially available worldwide.
Over the years, improvements have been made to make the technology more efficient, including measures to minimise emissions of SO2, NOx and particulates and application of advanced steam cycles that allow for greater plant efficiency. An example of this improvement is the ‘supercritical’ pulverised fuel (SPF) technology which can reach efficiency levels of up to 45%. Further improvements can be made in ultra-supercritical plants, which are still in the phase of research and development but which could be deployed in the market around 2020. An example of a research project on this technology is AD700, which is supported by EU equipment manufacturers and several end users. It has been the subject of a significant EU cooperative R&D programme involving 39 companies from 12 Member States.
The eventual efficiency level that can be achieved depends on whether hard or brown coal (lignite) is used and on the quality of coal (e.g. high vs low ash content).
Other higher efficiency coal-based techniques are Integrated Coal Gasification Combined-Cycle (IGCC) and Fluidised Bed Combustion (FBC).
Feasibility of technology and operational necessities:
Early supercritical steam-cycle plants in the USA and Europe in the 1970s had problems with operational flexibility and maintenance, but these problems have nowadays been largely solved. The technology is now considered reliable and economically viable. The main technical challenge with supercritical plants is that the higher steam pressure and temperature require components (superheaters, headers, water tubes, steam chests, rotors and turbine casings) which are produced from nickel-based alloys.
Nickel is an expensive commodity so that for an increased use of SPF at lower costs further developments are needed in new steels for water and boiler tubes and high-alloy steels that minimise corrosion.
Another operational aspect which would support the market penetration of supercritical and ultra-supercritical plants is the development of advanced control equipment and procedures (i.e. expert systems, condition monitoring) to operate a plant more flexibly.
With respect to developing countries with a high coal consumption, such as China and India, SPF technology transfers could take place by the sale of equipment, licensing, joint ventures, co-operative production, subcontracting of the manufacture of components, and co-operative research and development (Beijing Research Institute of Coal Chemistry, 2000). Possible forms of co-operation between industrialised and developing countries in this context could be selling licenses to developing countries, mounting joint ventures, and agreeing co-operative production.
Most notably and publicly, former New York Mayor Michael Bloomberg almost singlehandedly underwrote the Sierra Club’s “Beyond Coal” campaign several years ago, to the tune of more than $80 million. In partnership with the Obama administration’s regulatory regime, their plan was astonishingly successful. He and the Sierra Club now boast on several websites that the “Beyond Coal” campaign has closed more than half the nation’s coal plants, 289 out of 530. That is not enough; he wants all the rest closed within 10 years. In June of 2019, he announced that he had committed over $500 million more to “close every coal-fired power plant in the United States.”
Not surprisingly, that has caused the closure of over half the coal mines, too — more than 760 closed in eight years. Before the anti-coal campaign began, there were more than 2,000 coal miners in Colorado alone. But in case you wondered, none of that $500 million is intended to help the families of unemployed and displaced coal miners. The New York Times explained that it is “to fund lobbying efforts aimed at state and local government officials.” In other words, it all goes to environmental lawyers, lobbyists, and activists.
Ironically, while America shifts to natural gas and other sources, India, China, and dozens of other nations are mining coal. That’s why America’s “fuel switching,” however well-meaning, may not help the global environment at all. In fact, worldwide, the coal industry is booming like never before.
Although perhaps a questionable investment in the U.S., new coal power plants have attracted $745 billion in new investment worldwide, in just three years. So says a new report by the world’s oldest international news service, Agence France-Presse. The report looked at all 258 coal plant developers identified in the “Global Coal Exit List,” created by several international banks. The analysis found more than 1,000 new coal power plants in the planning pipeline — almost twice as many as were ever in the United States.
Needless to say, environmental groups are not happy about this trend, though they may have less power to stop it outside the U.S. An organization called BankTrack follows world banking investments closely, for the purpose of persuading banks to disinvest in activities it considers environmentally “unsustainable.” A BankTrack “climate campaigner” lambasted these new coal investments, saying, “Most of the top banks providing loans or investment banking services to these companies acknowledge the risks of climate change, but their actions are a slap in the face to the Paris Climate Agreement.”
According to the report, much of the investment comes from three top Japanese banks: Mizuho, Mitsubishi, and Sumitomo Mitsui. Those bankers apparently realize what many in America seem to have forgotten. Namely, that coal is by far the world’s most abundant and affordable source of energy, and that much of the world is still starving for the lifestyle that affordable energy provides.
Americans have a love affair with their environment, and because they live in the world’s most prosperous society, can afford to spend fortunes improving it — including tremendous strides in clean coal technology. They might remember, though, that affordable energy is one of the main reasons they have that luxury.
