This group was augmented by a small number of visiting investigators, who are presently in residence and have carried out a substantial part of their project.

In this and the following editions of EuroFlam News,  we are publishing abstracts of the presentations made.

Abstract
The present work is concerned with the effect of different bituminous coal chars pore surface structure on their combustion behavior. The chars were sampled in a semi-industrial coal jet flame of 2.5MW thermal input. The solid samples from the jet flame were compared with samples tested in an Isothermal Plug Flow Reactor (IPFR).

For surface characterization, N₂-adsorption and Scanning Electron Microscopy have been applied. Differences in the BET-surface area up to one order of magnitude were observed for char samples collected in both combustion facilities. It was concluded that the larger surface area of the IPFR char samples was due to a micropore structure, which was developed during devolatilization. The higher the initial particle heating rate was, the larger micropore structure and thus larger pore surface area was measured.

Since there was a difference in the char pore structure between the samples from the two facilities, it was attempted to apply the kinetic parameters derived from the IPFR experiments to calculate the burnout behavior of the char in the jet flame. The burnout behavior measured in the jet flame could be predicted with the kinetic data of the microporous char provided from combustion tests in the Isothermal Plug Flow Reactor. Therefore it was concluded that the micropores do not significantly affect the combustion rate and char reactivity.

Pyrolysis is a generic term used for the thermochemical breakdown of carboneous material to form a combination of gas, solid and liquid fractions.

There is great interest shown in the development of this technology to have strong commercial viability. Cardiff School of Engineering has designed a fast pyrolysis system.

This presentation contains the details of work done on a number of crucial areas to understand the operation of the rig. These areas are the process and description of pyrolysis in general, the calibration and set up of the feeders, the representation of velocity profile and the features of the pyro-oil.

Greenhouse effects, ozone problems, smog and acid rain are terms used when people talk about human influence on nature. 90 % of world-wide energy is produced by fossil energy through combustion reactions. This is an important reason to work with combustion systems.

In the last years there has been a growing interest in the mathematical modelling of combustion processes in many industrial sectors. This is more or less traditionally related to the development of Computational Fluid Dynamics (CFD). The main reason for this growing interest are the increasing reliability and the decreasing costs (in term of computational resources and required know-how) of these tools and the range of possibility for analysis of existing systems and evaluation, design and optimisation of the new ones.

The glass industry nowadays is facing the same problems that the energy industry approached ten years ago, due to the need for costs control and a tightening of pollutant law limits.

In this case, a mathematical simulation has been made of a natural gas-fired glass-melting furnace with a glass production of 200 t/day. The numerical approach is made with a commercial CFD - code FLUENT and is divided in two parts the numerical grid (Pre-processing with Gambit) and the solver (Calculation with FLUENT 5).

The aim of the work is to develop and set up a reliable 3D combustion model with a commercial code. It includes the model, mesh and the calculation for different cases. Using the model it should be possible to analyse and study the existing combustion systems to understand and solve process problems. This will mainly take into account the heat release of the wall.

Fuel Lean Gas Reburning (FLGR) is an in-furnace technique to reduce NO_x emissions from a coal fired boiler or furnace. It consists of the injection of hydrocarbon gas (5 - 10% of the total heat input) with high velocity jets in the lower temperature region of the combustion chamber. The formed CH-radicals transform the NO_x into pure nitrogen in local fuel rich zones, while remaining at global fuel lean conditions in the injection zone. No downstream addition of overfire air (OFA) is therefore needed.

This thesis presents the results of the theoretical study of the FLGR process and the parametric tests done on the 500 kW furnace of the experimental area of ENEL in Livorno.

Kinetics of combustion and nitrogen formation and destruction are discussed and applied to the kinetics of FLGR. The dependency of NO reduction efficiency on flue gas composition and injection zone temperature is shown.

Parametrical sensitivity and reduction rates are investigated during combustion tests on a 500 kW furnace. For this a gas injection probe is designed that produces small high velocity jets.

Whilst burning coal, reduction rates of 50% are reached with the injection of 8 - 10% gas heat input.

CO levels remained at an acceptable level, proving that the gas is able to combust completely and reduce NO at the same time.

For boilers and furnaces that need a moderate reduction of NO emissions, the FLGR process can be a more economic NO_x reduction technique than conventional gas reburning. Although reduction rates are higher with the latter, capital retrofit costs are also higher, because of the need for OFA and higher percentages of gas heat input.

This periodical forms part of the group of publications owned by the IFRF
The IFRF Monday Night Mail is published by:
IFRF NET, P O Box 10,000, The Netherlands
Edited: Peter Roberts
ISSN 1562-4781