Inside Coal FIRST: America’s tech drive to clean up coal

JP Casey 13 November 2019 (Last Updated November 13th, 2019 09:55)

In April, the US Department of Energy (DOE) announced the recipients of $1.95m in funding as part of its Coal FIRST (flexible, innovative, resilient, small and transformative) initiative, which aims to make coal plants more efficient and less environmentally damaging. From carbon capture techniques to the repurposing of waste carbon dioxide, JP Casey looks at four projects that aim to clean up the performance of coal.

Inside Coal FIRST: America’s tech drive to clean up coal
Echogen’s heat-to-power system has already produced 9MW of power, and can be scaled up tp provide more than 500MW. Credit: Echogen

8 Rivers’ Allam Cycle

The North Carolina-based firm received $149,147 in DOE funding, with the money expected to go towards its subsidiary company, NET Power, which has developed a carbon-neutral coal plant in Texas.

The plant uses a collection of technologies known as the Allam Cycle, which are headlined by two key innovations: a process called oxycombustion, where fuel is burned with pure oxygen rather than air, eliminating the production of nitrous oxide that leads to the formation of acid rain; and an entirely closed system where waste carbon dioxide is fed back into the combustor, where it replaces steam as the plant’s primary working fluid. NET Power claims that this latter development can overcome energy losses of up to 40% seen in conventional steam-fired power stations, where the expansion and contraction from water to steam and back again results in the wasting of energy.

The process’ only byproducts are liquid water and pure carbon dioxide, which NET Power aims to redirect into other industrial operations, such as enhanced oil recovery, a process to extract additional oil from reserves while simultaneously storing carbon dioxide underground. The company has already built a 50MW demonstration plant in Texas, and now plans to begin work on commercial-scale 300MW plants across the US.

While the technology is undoubtedly impressive, and has been proven to be effective on a large scale, concerns remain about the company’s ability to reduce reliance on fossil fuels in the long-term. Many of NET Power’s innovations benefit from and in turn benefit traditional energy sources, such as the enhanced oil recovery potential, raising questions about the Allam Cycle’s long-term viability.

Echogen’s heat-to-power scheme

Another cycle being used to improve efficiency and environmental performance in the Rankine Cycle, which has been adapted by Echogen Power Systems to form the backbone of a heat-to-power system. The company received $150,000 in funding, the joint-most awarded to any single project, to develop its system, which involves waste carbon dioxide being captured, converted into a liquid, and fed back into an engine to operate as the working fluid, effectively reducing the system’s waste carbon dioxide emissions to zero.

The company has already tested its solution in facilities producing up to 9MW of net power, but claims that it could be scaled up to operations producing more than 500MW. These figures suggest a solution earlier in its lifespan than the Allam Cycle developed by NET Power, as Echogen’s ‘heat engine’ is designed as a modular system that can be applied to a range of existing industrial facilities, from fossil fuel plants to biomass facilities. The company is also developing a variation of the Rankine Cycle that uses supercritical carbon dioxide, a fluid state of matter with properties of both a liquid and a gas, as the working fluid, further reducing the environmental impact of the process.

Echogen also has stronger renewable credentials than many of the other companies involved in the Coal FIRST scheme, as it has developed a chemical process to store solar energy collected during the day by panels, to be used later. The technology, which also uses supercritical carbon dioxide as its working fluid, has received a further $1m in funding from the DOE’s SunShot initiative.

Wormser Energy’s coal gasification

One of two companies to receive a total of $300,000 in funding, Wormser has refined the coal gasification process to deliver a number of financial and environmental benefits. While the process is not new – the production of a mixture of carbon monoxide, carbon dioxide, hydrogen, natural gas and water vapour from coal has existed in some form since the 17th century – Wormer’s solution produces significantly more hydrogen than conventional gasification, and the process has been made more efficient to reduce the size and cost of machinery involved.

As a result, the company claims to be able to reduce capital costs by at least 40% for plants that adopt its gasification technology, and to be able to capture and store up to 95% of the carbon dioxide produced in the process, dramatically reducing the environmental impact of coal-fired plants that use the solution. The technology can also be applied to a range of facilities, from existing power plants to new flexible generators, so Wormser is optimistic that the process will be deployed across the industry.

However, much of the solution is a refinement of existing technology, rather than unique innovations, and there are concerns that while the gasification process may improve the efficiency of existing coal-fired power stations, this remains a power source in decline, and Wormser’s work does little to address this. The fact that the DOE is investing so heavily in a project with relatively limited potential for long-term change also reflects poorly on the Coal FIRST initiative as a whole, with money going towards projects that aim to prolong the industry’s status quo, rather than more disruptive solutions.

Barr Engineering’s carbon capture solution

The second project to receive $300,000 in DOE funding, Barr’s carbon capture solution is similar in form to Wormser’s, although the technology has a more established history. The solution is based on technology developed in 2010 by the Institute of Energy Studies and the University of North Dakota, with Barr becoming involved in the project in 2012, demonstrating that the technology could be scaled up for use in a 550MW coal-fired power plant.

The technology itself, dubbed the CACHYS process, involves the use of a solid sorbent in the carbon capture process, rather than gases, which are traditionally used as reactants but can be less efficient. The use of a solid sorbent can reduce the total energy needed to complete the carbon capture process, and enable it to take place at lower temperatures, reducing the costs of the operation and enabling it to take place in a greater range of environments, increasing the overall volume of carbon captured.

Barr has completed planning work ahead of expanding the solution to the 550MW scale, including cost estimates for larger-scale operation and the development of another small-scale demonstration plant, and the support of the DOE will go a long way in continuing this development.

While the extensive academic and technological background of the project is a positive, the fact that it has failed to reach the commercial or industrial scale following nearly a decade of work and a number of grants could raise concerns about how effective this concept will be in reality.