Literature report: Natural gas reburning

 
Summary

This report is a literature study about gas reburning, a new technology to reduce the NOx emission. In reburning, natural gas is injected after the primary combustion zone, where it reacts with NOx forming free nitrogen.

Chapter 2 handles the background. This is a short description of NOx emissions, how it reacts in the atmosphere and the historical trend with increasing NOx emission. Also described are the main sources of NOx, which are the transport sector and power plants. Finally, efforts and methods to reduce NOx emission are described.

Chapter 3 contains a description of the reburn technology and status concerning recent work and research applied to full-scale boilers. A short review of potential industrial applications of gas reburning is also given.

In chapter 4 is given a short description and discussion of important parameters for the reburn process. These parameters are, for the primary zone: primary fuel, stoichiometry, temperature, residence time and design and operating conditions. Important parameters for the reburn zone: fuel type, stoichiometry, residence time, temperature and mixing effects.

Important parameters are, for the burnout zone: temperature, unburned carbon, stoichiometry, residence time and mixing effects.

The chemistry involved in the reburn process is described in chapter 5, with special focus on reaction path and reactions where there are uncertainties. First part is a description of the hydrocarbon oxidation path and thereafter there is a description of the nitrogen chemistry involved in combustion. A full kinetic mechanism for the reburning process is given in appendix B.