systems for controlling NO_x emissions from syngas-fired, combined-cycle power plants.

Finding. The use of oxygen in place of air to fire hydrogen in integrated gasification combined cycle (IGCC) plant combined cycles has been proposed as a method of reducing NO_x emissions. Diluents will be needed to reduce the adiabatic flame temperature in the combustion zone.

Recommendation. System studies should be used to determine if the use of oxygen and hydrogen in a turbine to reduce NO_x emissions is economically viable.

The primary aim of the Vision 21 Program is elimination of environmental impacts from the use of coal to produce electricity, fuels, and chemicals. Emissions to the air are controlled in Vision 21 technologies by improved efficiency and emission control technology. Emission control technology development within the DOE is found in three different program areas: coal and environmental systems, gasification, and sequestration. The coal and environmental systems area is divided into two programs: (1) Innovations for Existing Plants (IEP), which focuses on pulverized coal and fluidized-bed combustion systems for existing and new power plants and (2) Vision 21, which focuses on gasification-based systems for new power plants. IEP has been aimed at reducing the emissions of conventional pollutants such as sulfur dioxide (SO₂), NO_x, and particulate matter, but more emphasis is now being given to controlling hazardous emissions such as trace metals, acid gases, and organics. In the gasification area the focus is on syngas cleanup rather than post-syngas combustion releases to the ambient air. Syngas cleanup is discussed more fully in the section on gas purification. The sequestration program deals with the capture, separation, and reuse or disposal of CO₂ emissions. Capture and separation of CO₂ are discussed in the section on gas separation. The disposal of CO₂ is not addressed in this review of the Vision 21 R&D program.

The emission control goal of the Vision 21 Program (gasification-based system focus) is as follows: Remove environmental concerns (i.e., achieve near-zero emissions) associated with the use of fossil fuels (coal, gas) for producing electricity and, where appropriate, clean transportation fuels (including