Fluid sprinkling – spraying – and diffusing – Including supplemental gas shaping or shielding jet
Patent
1995-03-30
1997-06-24
Morris, Lesley D.
Fluid sprinkling, spraying, and diffusing
Including supplemental gas shaping or shielding jet
239431, B05B 128, B05B 706
Patent
active
056411243
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus for cleaning gas in order, from a flow of polluted gas, to remove gaseous pollutants.
The apparatus comprises a nozzle for atomizing a liquid, optionally containing suspended dry matter, by means of compressed gas, comprising, an inlet for liquid, an inlet for compressed gas, and an outlet for gas mixed with finely divided liquid, as well as an intermediate mixing space. The inlet for compressed gas is adapted to give the gas a substantially rectilinear path through the mixing space. The inlet for the liquid is separated from the mixing space by a partition having a plurality of first holes for introducing the liquid into the mixing space in a direction substantially perpendicular to the main flow direction of the gas in the mixing space. The mixing space is defined downstreamby a wall having a plurality of second holes.
The apparatus is especially suited for separating sulphur dioxide from flue gases. In such separation, use is generally made of completely wet methods or methods where a large amount of absorbent is suspended in water and supplied in finely divided form to the flue gas, because completely dry methods do not yield satisfactory separation of sulphur dioxide on account of the relatively low reactivity thereof, with inexpensive absorbents such as slaked lime or finely milled limestone.
BACKGROUND OF THE INVENTION
The emission of acidifying gases, such as sulphur dioxide, from e.g. coal-fired power plants has become a major environmental problem. Several different methods have been tried in order to reduce emissions of this type.
To this end, it has been suggested both to purify the fuel and to take measures during the combustion and/or to clean the flue gas produced. Certain pollutants, such as nitrogen oxides, can be dissolved in harmless substances. The formation of pollutants can also be counteracted or obviated by optimizing the combustion process. Other substances, such as sulphur, can however be taken care of only as a residual product and must not be emitted in any form in an uncontrolled manner. In order to remove sulphur, for example, an absorbent is generally added which contains substances forming together with sulphur stable compounds, either in the combustion chamber or in a specially designed flue gas cleaning system.
Examples of prior-art methods are given in SE-8005571-8 involving the injection of absorbent into the combustion chamber, DE-36 07 357 involving wet flue gas cleaning, SE-7904382-4 involving wet-dry flue gas cleaning, EP-0 177 896 involving completely dry flue gas cleaning, and SE-8505269-4 disclosing a combinatory solution.
When supplying absorbent in the combustion chamber, the major drawback is the low degree of utilization of the absorbent. The wet flue gas scrubbers are far more efficient in this respect, but involve high investment costs and maintenance problems.
Wet-dry flue gas cleaning entails lower investment costs but requires a more refined and thus more expensive absorbent than the wet flue gas scrubbers. To avoid precipitation of moisture in the flue gas cleaning system, the absorbent is supplied, in the wet-dry methods, dissolved or suspended in an amount of water which is smaller than the amount required for cooling the flue gas to a temperature below the saturation temperature. The amount of liquid supplied and, hence, the amount of absorbent supplied are thus limited by the heat content of the flue gas.
The completely dry methods involve the lowest investment costs for the flue gas cleaning systems, but most often require a highly refined and, thus, expensive absorbent and do not permit high-grade cleaning. The main reason for this is that solid phase reactions are slow at the temperatures normally prevailing after a coal-fired boiler.
To obtain high-grade cleaning by means of a simple flue gas cleaning system which does not include means for producing, transporting or atomizing an absorbent suspended in water, different techniques intermediate between the dry and wet-dry methods hav
REFERENCES:
patent: 1565996 (1925-12-01), French
patent: 2566040 (1951-08-01), Simmons
patent: 2613737 (1952-10-01), Schwietert
patent: 3790086 (1974-02-01), Masai
patent: 4625916 (1986-12-01), Nieuwkamp et al.
ABB Flakt AB
Morris Lesley D.
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