The first patent covers energy recovery during expansion of compressed gas using power plant low-quality heat sources.
The invention capitalises on energy that would otherwise be lost in cold compressed gas streams in power plants. Once a gas stream has been cooled and condensed, this invention uses exit cooling water from a power plant condenser (or other comparable low-quality heat source) to heat the cool high-pressure gas stream.
The warmed compressed gas is then sent through an expansion engine (such as a turbine) to recover the energy.
“Current processes for removing pollutants and greenhouse gases from flue gas streams at power plants are significant net energy users and incur significant parasitic costs in processing the flue gas streams. The production of this extra energy will help offset processing costs and encourage the use of environmental safeguards to slow the accumulation of greenhouse gases in the atmosphere,” NETL said.
The patent covering mercury capture from gas streams recognises the need for a low-cost technique to remove mercury from coal-utilising facilities.
The inventors developed a method to absorb mercury from high- and ambient-temperature gas streams instead of emitting the mercury into the environment.
The invention uses metal sorbents to capture the trace metals mercury, arsenic and selenium during various cycles of emissions, and it provides for potentially regenerating the sorbents in a one-step process. Because it can operate at temperatures greater than 205C, the method can be used in integrated gasification combined cycle systems without disturbing their high thermal efficiency.
“The method will also facilitate Energy Department plans to expand the use of coal gasification over the next 20 years by mitigating the trace metals produced in the gasification process,” NETL said.
