Oxygen enrichment of the combustion gases for sinterbed ignition

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• Publié par: EUROPEAN-COMMISSION
• Nombre de lectures: 52
• Langue: English
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Commission of the European Communities
technical steel research
Reduction of ores
OXYGEN ENRICHMENT OF IGNITION GAS
IN A DL SINTER PLANT
Report
EUR 8694 EN
Blow-up from microfiche original Commission of the European Communities
technical steel research
Reduction of ores
OXYGEN ENRICHMENT OF IGNITION GAS
IN A DL SINTER PLANT
P. HOFMANN
ARBED RECHERCHES
66, rue de Luxembourg
L-4221 ESCH-SUR-ALZETTE
Contract No 7210.AA/505
(01.07.1979 - 30.09.1982)
FINAL REPORT
Directorate-General
Science, Research and Development
1986 EUR 8694 EN Published by the
COMMISSION OF THE EUROPEAN COMMUNITIES
Directorate-General
Information Market and Innovation
L-2920 LUXEMBOURG
LEGAL NOTICE
Neither the Commission of the European Communities nor any person acting
on behalf of then is responsible for the use which might be made of
the following information
>ECSC-EEC-Euratom, Brussels · Luxembourg ARBED
CEC/ARBED CONTRACT NO. 7210/AA/505
OXYGEN ENRICHMENT OF IGNITION GAS IN A »L SINTER PLANT
FINAL REPORT
CONTRACTOR: ARBED S.A.
Sub-Contractor: Lurgi, Frankfurt
In charge of research: P. Hofmann, Arbed Research
Location of: Arbed, Esch-Belval Works
Duration of project: 1.7.1979 - 30.9.1982
1. INTRODUCTION
This project is part of the investigations which aim at a reduction in
energy consumption and rational use of energy in the practice of grate
sintering.
Among known methods of diversifying, and even reducing, the primary energy
input into sintering are the techniques which consist in replacing part
of the solid fuel either with gas fuels or hot air. The following should
be mentioned in particular:
- methods of preheating the sinter mix before ignition, and
- methods of reheating after ignition.
These methods may at the same time provide a partial solution to the
problem of reducing harmful emissions during sintering.
Additional heat input in gas form requires an extended ignition
hood or a heat treatment hood located up line or down line from the ignition
furnace.
While it is necessary in the first case ie. for preheating the mix, to
use neutral or only slightly oxidising waste gas so as not to cause
premature combustion of the solid fuel in the mix before ignition, it is ERC 1983/55 2.
on the other hand desirable, in the second case, when using waste gas
from combustion, that this gas should be sufficiently oxidised to allow
good combustion efficiency from the solid fuel already in the heat
treatment zone. This condition is particularly important for correct
sintering of the upper layer of the mix.
The objective in the second case, and which also applies to ignition,
is not achieved when the gas fuel used is a poor gas of the blast furnace
gas type slightly enriched with natural gas.
Depending on the operating conditions for ignition and for possible
subsequent heat treatment, the oxygen content of the combustion waste
gas may vary to a large extent and have a marked effect on the sintering
process.
The aim of this study is to verify, under industrial conditions, both
for the ignition phase and for a subsequent heat treatment phase, the
effect of an increased oxygen content in the combustion waste gas on sintering
characteristics and on the properties of the sintered product.
II. OBJECTIVE OF THE RESEARCH
This research basically pursues two objectives. The first is to improve
ignition conditions for the mix and for combustion of the solid fuel in
order to obtain improved efficiency from the fuel in the upper part of the
sinter bed. This must lead to a reduction in the specific consumption of
solid fuel and improved physical quality of the sinter in the upper part
of the bed.
The second objective is to simulate, by oxygen enrichment of the waste
gas, the operating conditions corresponding to the use of preheated
combustion air in order to define the economic range of application for
recycling hot process air. ERC 1983/55 3.
III. MEANS EMPLOYED
1. Means of increasing the oxygen content of the waste gas
Combustion of a gas with a given calorific value using cold air produces
waste gas at a temperature which reaches the maximum theoretical value
when combustion takes place with the theoretical air volume. This waste
gas then contains no free oxygen. To obtain waste gas temperatures below
the maximum theoretical temperature it is necessary for combustion to
take place with excess air while aiming at complete combustion, which
is indispensible in an industrial process. This excess air then also
determines the oxygen content of the waste gas.
In what follows we shall base our considerations on combustion of a poor
gas consisting of blast furnace gas slightly enriched with natural gas
and we shall take as reference the case which applies at Esch-Belval Works
ie. combustion of a mixed gas with a nett calorific value of 4190 kJ/m n.
Combustion of this type of gas with cold air produces waste gas with
an oxygen content at the usual ignition temperature which does not exceed
5%.
This concentration is too low to allow combustion of the solid fuel in
the sinter mix. The minimum content necessary for stoichiometric combustion
is then, according to Cappe1 and Kilian (2), 10 to 12% for mixes consuming
60 to 70 kg of dry fuel per t sinter.and when maximum suction head is
applied below the ignition hood. When the suction head is reduced, oxygen
requirements are higher.
The means available for increasing the oxygen content of the waste gas,
with constant temperature, are as under:
- oxygen enrichment of the combustion air, or direct enrichment of the
waste gas,
- increasing the temperature of the combustion air,
-g the calorific value of the gas.