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Contenido archivado el 2022-11-21

The control of emissions of sulphur compounds during the treatment of blast furnace slag

Objetivo

The primary objectives of the work were to examine the factors influencing the formation and emission of sulphur compounds and to develop modified operating practices to reduce such emissions during the processing of blast furnace slags in open pits. The investigation was carried out in parallel with project PS 508 at the Verein Deutscher Eisenhuttenleute (VDEh) in Germany, where studies have been directed towards the control of emissions of sulphur compounds from slag granulation.
The present investigation was conducted on full scale slag pits at an integrated iron and steelworks. A sampling system was constructed, consisting of a probe, an inert heated line, sample conditioning unit and electro-chemical detectors, and this was used to monitor the emissions of sulphur compounds during the cooling and water quenching of the accumulated slag pool.

Under normal conditions of wet quenching, hydrogen sulphide was emitted during the first 5 or 6 h, the peak level occurring typically about 30 min after the commencement of quenching. The peak hydrogen sulphide concentrations measured above the slag surface (approximately 200 mm above the surface) were between 100 and > 500 ppm of hydrogen sulphide depending on the rate of filling and turn around of the pit. The emission of hydrogen sulphide was markedly reduced when lime was applied to the slag surface prior to quenching. The lime was applied as a 20% slurry in water by use of a water cannon and, after evaporation of the water, a blanket of lime was left on the slag surface. At a slurry application rate of 5 kg/m{2} the emission of hydrogen sulphide was almost totally suppressed. The raw materials cost of the treatment amounted to 1.6 to 2.3 p/t of hot metal. Capital costs are difficult to estimate because a full design specification has not yet been developed. Further work is also required to determine whether there is a tendency for 'ball slag' formation to occur when liming is carried out.

A sample diffusion tube sampler for monitoring of hydrogen sulphide in ambient air has also been developed and tested. The sampler consists of an acrylic tube, that is approximately 70 mm long and 12 mm internal diameter, the ends of which are machined to accept push-fit polythene caps. A stainless steel mesh disc coated with zinc acetate, which acts as an absorber for hydrogen sulphide, is placed at one end of the tube and held in place with a polythene cap. The other end of the tube is sealed with a second polythene cap which is removed before sampling, thereby allowing hydrogen sulphide to diffuse along the tube to be collected by the absorbent.

The device has been fully tested around the slag quenching pits and found to exhibit good response to ambient hydrogen sulphide. The diffusion tube sampler is simple to construct, inexpensive, unobtrusive and requires no electrical power. It therefore offers a simple yet effective method of monitoring for the impact of hydrogen sulphide emissions from slag pits and other sources.
There are two principal methods used in the EU for processing blast furnace slag, namely:

(a) open pit cooling followed by water quenching: and,

(b) granulation with water.

Convocatoria de propuestas

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Régimen de financiación

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Coordinador

CORUS U.K. LTD
Aportación de la UE
Sin datos
Dirección
Moorgate
S60 3AR ROTHERHAM
Reino Unido

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Coste total
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