Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Sulfur or sulfur containing component
Patent
1987-05-15
1988-08-16
Hart, Charles
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Sulfur or sulfur containing component
55 73, 55 97, 55304, B01J 800
Patent
active
047643552
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a National phase application corresponding to PCT/EP86/00447 filed July 29, 1986 and based, in turn, on a German National application P 35 29 272.5 filed Aug. 16, 1985.
FIELD OF THE INVENTION
This invention relates to a process for the simultaneous removal of solid and gaseous noxious matter from hot sulphur-containing gases, by means of filters on which a filter cake is deposited.
BACKGROUND OF THE INVENTION
It is known that dust removal by filtration can also be used for desulphurization. In that case alkaline additives such as calcium hydroxide are added to the gas stream in order to bind sulphur oxides (W. Schulte.beta., Brennstoff-Warme-Kraft, Vol. 36 (1984), No. 10, p. 420-426). After reaction, these additives must be removed, together with the dust, from the gas stream. To this end, fabric filters are used so that filtration takes place within and on the forming filter cake. It has been found that the reaction of Ca(OH).sub.2 with SO.sub.2 is substantially boosted by continued reaction in the filter.
In fabric filters, however, an irreversible deposit of ultrafine particles in the filter fabric takes place (irreversible partial plugging). The resulting high pressure drop and high cleaning-cycle frequency result in excessive wear. Furthermore, the known fabric filters can only be run at operation temperatures of up to approx. 250.degree. C. (W. Schulte.beta., Brennstoff-Warme-Kraft, Vol. 36 (1984), No. 10, p. 422), and in particular in case of high solids concentrations, an upstream preliminary separation step may become necessary.
OBJECT OF THE INVENTION
The object of the invention is to improve methods of separating solid and gaseous noxious matter from hot gases in a way that the above mentioned draw-backs as well as the necessity of a preliminary separation step are avoided.
SUMMARY OF THE INVENTION
This object is achieved in accordance with the invention by cycling the hot gases loaded with solid and gaseous noxious matter through a filtration unit with metallic gap-type candle filters.
Such filtration units with metallic gap-type candle filters are known from filtration of liquid matter (DE-PS 28 28 976, DE-OS 27 06 938). With gap-type candle filters, irreversible partial plugging does not take place. The possible filtration time is controlled exclusively by the permeability of the building-up filter cake. Preliminary dedusting, previously necessary in case of high solids loads, is not necessary. Temperature- and corrosion-conditioned limitations to the use of metallic gap-type candle filters can be overcome by purposeful material selection, so that the process covered by this invention is particularly well suited for separations run at high temperatures. The gap-type candle filters of the most preferred type have gap widths in the range between 0.05 and 0.15 mm.
The adhesion of the filter cake to the surface of a gap-type candle filter is low, so that the cake can be removed simply and rapidly. For this reason, gap-type candle filters are particularly suited for processes in the course of which additives for binding gaseous noxious matter are added, because the additives must be removed from the gas stream, and this constitutes an additional task for the filtration process.
As additives, we can use substances which bind gaseous noxious substances by chemical reaction (chemisorption) or matter which bind the gaseous components by adsorption (physisorption). Basic metallic compunds such as calcium hydroxide, calcium carbonate and ferric hydroxide as well as adsorbents such as activated carbon, activated coke, silicon oxide, aluminum oxide and aluminum silicates can be used. The additives have a particle size in the range between 0.05 and 0.3 mm. With this particle size we can ensure that the filter cake which is built up remains permeable to gas.
According to composition, temperature of the gas and the additives chosen for binding the gaseous noxious matter, the additive either is metered into the hot gas stream or, prior t
REFERENCES:
patent: 4269613 (1981-05-01), Miko et al.
patent: 4372927 (1983-02-01), McCullough
patent: 4512787 (1985-04-01), Mathews
patent: 4533532 (1985-08-01), Gebhard et al.
patent: 4581210 (1986-04-01), Teller
patent: 4609539 (1986-09-01), Hnecky et al.
"Filterende Staubabscheidung fur Kohlefeuerkessel", by W. Schultess, published in BWK, vol. 36 (1984) No. 10, Oct.
Ahland Erwin
Pass Reinhard
Romey Ingo
Verfuss Franz
Bergwerksverband GmbH
Dubno Herbert
Hart Charles
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