Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – With regeneration – reclamation – reuse – recycling or...
Patent
1992-11-25
1994-10-04
Jones, W. Gary
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
With regeneration, reclamation, reuse, recycling or...
162 29, 162 31, 239 9, 2394165, 110238, D21C 1112
Patent
active
053523334
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for partial combustion of cellulose spent liquors from the cellulose industry using a burner connected to a reactor, while supplying an oxygen containing gas as the oxidant. The burner comprises a liquor lance equipped with a nozzle at its downstream end which supplies liquor and the greater part of the non-fuel related oxygen required for the partial combustion, wherein or in which proximity the oxygen-containing gas is brought into contact with the spent liquor which then disintegrates into a divergent spray.
The object of the present invention is to facilitate partial combustion of cellulose spent liquor through use of a burner creating a stable, self-igniting flame at low air/fuel ratios and elevated pressures.
BACKGROUND OF THE INVENTION
The cellulose industry generates spent liquors differing in composition according to the delignification process used. Within the sulphate pulping industry, spent liquor, commonly referred to as black liquor, contains valuable chemicals and energy in the form of combustible carbonaceous compounds. At the present time these chemicals and energy are normally recovered in a recovery boiler in which the black liquor is completely burned.
Partial combustion of black liquor in a gasification reactor as in the present invention generates a combustible gas comprising H.sub.2, CO, CO.sub.2, and droplets of molten inorganic chemicals.
In conjunction with pulp bleaching, a diluted liquor comprising organic matter and sodium salts is obtained. Mechanical and semi-chemical pulping processes also generates diluted liquors of different compositions. These as well as other waste and spent liquors generated in the cellulose industry can, after concentration, be used as a feedstock in the process of the present invention.
Although the following description describes the present invention as it applies to black liquor it is not restricted only to this particular liquor in its application.
The mechanisms related to partial combustion of black liquor are fairly well understood and are applied inter alia in the lower part of the soda recovery boiler. The difference between the present burner and a liquor burner in a soda recovery boiler is, however, great inter alia due to the low degree of liquor atomization in recovery boiler burners and the absence of a well-defined liquor flame. Another important difference between a recovery boiler burner and the burner of the present invention is that the present burner is primarily intended for gasification at elevated pressures.
A major difference between the burner of the present invention and conventional oil burners is that a stable flame has to be formed with the use of a considerably lower amount of air or oxygen carrier.
As the exemplification below shows black liquor as a fuel is characterized by a relatively low calorific value and high water and ash contents.
______________________________________ Calorific value of
13 GJ/ton dry substance (DS)
the dry substance
Elementary composition
C.sub.29 H.sub.34 O.sub.20 Na.sub.9 S.sub.2
Dry solids content
65%
Viscosity at 100.degree. C.
100 cSt.
______________________________________
The presence of sodium compounds in the black liquor and its inherently high oxygen content make it a very reactive fuel, which means, provided an adequate burner is at hand, that the carbon conversion already in the flame zone becomes high, in spite of the fact that the combustion is substoichiometric.
The degree of atomization of the liquor is of great importance for obtaining a stable black liquor flame, the extension of the flame and high carbon conversion. The rheological properties of the black liquor are of significant importance to the degree of atomization which can be achieved in a given nozzle. The viscosity of the black liquor can be influenced by e.g. heating and/or the addition of additives. Normally the black liquor is being heated to above 100.degree. C. for use in the present invention. The viscosity of the black liquo
REFERENCES:
patent: 3163495 (1964-12-01), Greenawalt
patent: 3323858 (1967-06-01), Guerrieri
patent: 4412808 (1983-11-01), Sheppard et al.
patent: 4762532 (1988-08-01), Lipp
patent: 5044552 (1991-09-01), Becker et al.
Chemrec Aktiebolag
Jones W. Gary
Nguyen Dean T.
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