By using electric fields to control the combustion of fuel by manipulating the shape and brightness of flames, it could soon be possible to nearly eliminate key pollutants from power plants and refineries and make them more efficient.
The technology could offer a cheaper way to reduce pollution in poor countries. And because the approach reduces pollution, it also reduces the amount of fuel a power plant consumes, it can pay for itself, said officials at Seattle-based ClearSign Combustion. The need for better pollution controls is clear now in China, where hazardous pollution has been shutting down schools and roads.
The company said its technology could reduce fuel consumption by as much as 30 percent. While outside experts said the likely improvement would be far less, possibly only a few percent, even that would still result in large savings.
Much of the pollution from a power plant is the result of problems with combustion. If parts of a flame get too hot, it can lead to the formation of nitrogen oxides, which contribute to smog. Similarly, incomplete burning, which can result from the poor mixing of fuel and air, can form soot.
ClearSign uses high-voltage electric fields to manipulate the electrically charged molecules in a combustion flame. This can improve the way air and fuel mix together, and can spread out a flame to prevent hot spots that cause pollution.
The idea of using electricity to shape flames has been around for decades. But conventional approaches typically involve plasma, and the plasma needs large amounts of energy. ClearSign said its technology only uses one-tenth of 1 percent of the energy in the fuel that a power plant consumes. It works using electrodes within the flame. The electrode produces high voltages that influence the movement of ions; by varying the voltage, it’s possible to control the way the flame forms. The technology can be effective at reducing smog-forming NOx emissions, carbon monoxide, and soot.
“There’s been interest in electric fields for some time, but nothing with as strong an effect as they’ve demonstrated,” said Michael Frenklach, a professor of mechanical engineering at the University of California, Berkeley.
In addition to reducing pollution, the technology can improve the efficiency of a power plant or a refinery in several ways. Improved mixing of fuel and air means less fuel ends up wasted by incomplete combustion; the technology can also improve heat transfer from the flame to the water in a boiler, so it uses less fuel to make steam, which drives the turbines in a power plant. But the biggest potential for fuel savings could be in reducing or eliminating the need for conventional pollution controls, which can consume significant amounts of energy, and can be expensive.