Fuel nitrogen conversion in solid fuel fired systems

This paper presents information on global energy consumption by fuel type (liquid fuels, coal, natural gas, renewables and nuclear) and sectors (buildings, industrial, transportation and electricity), and environmental impact of global energy consumption (SOx, NOx and CO2 emissions). There is a strong relationship between energy consumption and economic growth. The Global Financial Crisis has affected the global economic growth violently. The governments have recently adopted some effective measures to fight against the Global Financial Crisis. The structure of energy consumption and the conditions of SOx, NOx, and CO2 emissions affect the global changes (acid rain and greenhouse effect). Today, considerable effort is being devoted to reduce CO2 emissions because of the Kyoto Protocol on climate change. This publication presents multidisciplinary perspectives on the interrelated topics of energy consumption, energy security and energy policy. Additionally, the present study examines the relationship between energy consumption and greenhouse gas emission.

Structure and environmental impact of global energy consumption

Clean solid biofuel production from high moisture content waste biomass employing hydrothermal treatment.

A comprehensive review of measurements and data analysis of laminar burning velocities for various fuel+air mixtures

NOx control through reburning

Basic effects on NOx emissions in air staging and reburning at a bench-scale test facility

The possibility of a combined application of coal and biomass using two different co-combustion technologies has been investigated. A blending of pulverized biomass with coal showed a high burnout up to 20% thermal input of biomass for all particle sizes of the biofuels tested. CO emissions were generally lower than 150 mg/m3 (6% O2) and remain below 100 mg/m3 in the most cases. Reburn investigations with three pulverized biomasses resulted in NOx emissions of approximately 300 mg/m3 (6% O2). With pyrolysis gas as reburn fuel, minimum NOx emissions of 200 mg/m3 (100 ppm) at 6% O2 in the flue gas are possible. The main parameters are pyrolysis gas composition, stoichiometry, and residence time in the reduction zone. Best minimizing results have been achieved with pyrolysis gas produced at about 800 °C using coal as raw material; using biomass as feedstock, the influence of the pyrolysis temperature is only small. The nitrogen concentration, especially in the tar components of the pyrolysis gas, appears to ...

Investigations in Combined Combustion of Biomass and Coal in Power Plant Technology

Distribution of fuel nitrogen in pyrolysis products used for reburning

At an experimental facility of the Stuttgart University, the process of fuel splitting and staging is investigated with a view to lower NOx emissions. Raw coal is introduced into either an electrically heated, entrained flow reactor or a fluidized bed reactor where it is split into pyrolysis gas and residual char. In a following staged combustion, the remaining char or raw coal is used as primary fuel and the pyrolysis gas as reburn fuel. The test facility allows a systematic study to evaluate the effect of different parameters on NOx reduction independently of each other. Pyrolysis experiments, combustion studies, and calculations have been performed to explain the effective NOx reduction with coal pyrolysis gas. To compare the results and show the advantage of this process, investigations with fuel staging were carried out. With gaseous reburn fuels and residence times higher than 1.5 s, minimum NOx emissions below 200 mg/m3 at 6% O2 could be achieved independently of the coal type (200 mg/m3 is approximately equivalent to 100 ppmv). Reburning with coal pyrolysis gas increases the optimum air/fuel ratio from 0.75 to 0.9, yielding the same or even lower NOx emissions. The main parameters are stoichiometry and residence time in the fuel-rich secondary zone. The results also show an increase of the reduction efficiency with increasing reburning temperatures in the reburn zone. The tar components in the reburn fuel and the fuel-N content are very important parameters in achieving excellent results when using coal pyrolysis gas. These appear to have a positive effect on the reduction of NOx emissions. To explain this effect, the model of the perfectly stirred reactor (PSR) was employed. The modeling results agree well with the experimental investigations.

Impact of temperature and fuel-nitrogen content on fuel-staged combustion with coal pyrolysis gas

Publisher Summary This chapter discusses the reburning efficiency of a pyrolysis gas produced in an entrained flow or fluidized-bed reactor. Pyrolysis experiments are performed for a series of Australian and German coals and combustion studies in a two-stage fuel splitting and staging reactor. Fuel staging or reburning is an efficient method to reduce NOx emissions from bituminous and brown coals. With coal pyrolysis gas as reburn fuel, the NOx reduction is improved. The German emission standards of 200 mg/m3 at 6% oxygen (O2) are achieved at the test facility. The optimum pyrolysis temperature for brown coal maximum NOx reduction is determined at 800°C. At this temperature, the pyrolysis gas contains maximum concentrations of tar, hydrocarbons, and ammonia (NH3).

U. Greul

Papers

Basic effects on NOx emissions in air staging and reburning at a bench-scale test facility

Investigations in Combined Combustion of Biomass and Coal in Power Plant Technology

Distribution of fuel nitrogen in pyrolysis products used for reburning

Impact of temperature and fuel-nitrogen content on fuel-staged combustion with coal pyrolysis gas

NOX reduction using coal pyrolysis gas as reburn fuel: Effects of pyrolysis gas composition