Furnaces – Utilizing powdered fuel – Having secondary air mixing means
Patent
1992-03-02
1993-11-23
Favors, Edward G.
Furnaces
Utilizing powdered fuel
Having secondary air mixing means
110264, 110347, F23D 100
Patent
active
052634264
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a combustion apparatus, and for example, to a combustion apparatus of a pulverized coal boiler.
BACKGROUND OF THE INVENTION
In a pulverized coal firing boiler, a combustion apparatus injects a mixture of pulverized coal and air into a furnace through a mixture feeding pipe. The mixture injected is ignited so as to form a flame in the furnace. As directed in U.S. Pat. No. 4,545,307, a radially outwardly flared flame maintaining ring is provided at an end of the mixture feeding pipe. Vortices of the mixture are formed along the flame maintaining ring so that the pulverized coal is concentrated in the vicinity of the flame maintaining ring. As a result, an ignition takes place from the end portion of the mixture feeding pipe located in the furnace to form a high temperature strong reduction flame, thereby making it possible to suppress the generation of nitrogen oxides (NOx).
Disadvantages of the above construction reside in the fact that the flame maintaining ring gets, covered with ashes and is maintained under a reduced atmosphere and, further is exposed to high temperature due to radiant heat from the furnace. These conditions may cause a burnout of the flame maintaining ring or, when the operation is not proper, a formation of slag on the flame maintaining ring, that is, promotion of the slagging, under certain circumstances. The burnout of the flame maintaining ring or the formation of the slag results in the deterioration of the effect of the flame maintaining ring, an increase of the amount of NOx, or the trouble of the apparatus.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a combustion apparatus capable of effecting a low NOx combustion in a stabilized manner regardless of the unit capacity or the operating load of the combustion apparatus.
To this end, according to the present invention, a radiation from the flame is shut off and one of three factors of occurrence of the slagging, namely, high temperature, reduced atmosphere and existence of ash, is eliminated.
According to the present invention, a projection extends into a furnace beyond a flame maintaining means so as to adequately prevent radiation from the inside of the furnace to the flame maintaining means and to suppress an excessive increase in temperature, thereby restraining the burnout of the flame maintaining means and the occurrence of the slagging on the flame maintaining means.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a sectional view of a combustion apparatus according to an embodiment of the present invention;
FIG. 2 is a front view taken along the lines II--II in FIG. 1;
FIG. 3 is a partly fragmentary sectional view illustrating a projection shown in FIG. 1;
FIG. 4 is a partly fragmentary front view of the projection of FIG. 3;
FIG. 5 is an enlarged fragmentary front view of the projection of FIG. 4;
FIG. 6 is a sectional view taken along the lines VI--VI in FIG. 5;
FIG. 7 is a partly fragmentary front view illustrating a modification of the projection;
FIG. 8 is a fragmentary sectional view taken along the lines VIII--VIII in FIG. 7;
FIG. 9 is a fragmentary sectional view illustrating another modification of the projection;
FIG. 10 is a sectional view of another embodiment of the combustion apparatus;
FIG. 11 is a side view illustrating a conical portion of a pulverized coal/air separating member shown in FIG. 10;
FIG. 12 is a front view taken along the lines XII--XII in FIG. 11;
FIG. 13 is a side view illustrating the conical portion of another pulverized coal/air separating member;
FIG. 14 is a front view taken along the lines XIV--XIV in FIG. 13;
FIG. 15 is a side view illustrating the conical portion of still another pulverized coal/air separating member;
FIG. 16 is a front view taken along the lines XVI--XVI in FIG. 15;
FIGS. 17 to 19 are sectional views illustrating other modifications of the conical portion of the pulverized coal/air separating member, respectively; and
FIG. 20 is a sectional view of a different combustion a
REFERENCES:
patent: 4545307 (1985-10-01), Morita et al.
patent: 4807541 (1989-02-01), Masai et al.
patent: 5090339 (1992-02-01), Okiura et al.
Patent Absracts of Japan-Publishing No. JP59086809-Pub. date May 19, 1984 Application date Sep. 11, 1982-Application No. JP820195274.
Chinese Office Action and translation of same.
Baba Akira
Hodozuka Kunio
Ishii Keiji
Jimbo Tadashi
Kobayashi Hironobu
Babcock-Hitachi Kabushiki Kaisha
Favors Edward G.
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