Process for operating a coal-fired furnace with reduced slag formation

Abstract

There is provided a process for operating a coal-fired furnace to generate heat. The process has the steps of a) providing the coal to the furnace and b) combusting the coal in the presence of a first slag-reducing ingredient and a second slag-reducing ingredient in amounts effective to reduce slag formation in the furnace. The first slag-reducing ingredient and the second slag-reducing ingredient are different substances. The first slag-reducing ingredient is selected from the group consisting of magnesium carbonate, magnesium hydroxide, magnesium oxide, magnesium sulfate, and combinations thereof. The second slag-reducing ingredient is selected from the group consisting of copper acetate, copper nitrate, aluminum nitrate, aluminum oxide, aluminum hydroxide, and ammonium phosphate. There is also provided a method for reducing slag formation in a coal-fired furnace.

Claims

1. A method for reducing slag formation in a coal-fired furnace, comprising: combusting coal in the furnace in the presence of a first slag-reducing ingredient and a second slag-reducing ingredient in amounts effective to reduce slag formation in the furnace; wherein the first slag-reducing ingredient comprises magnesium; wherein the second slag-reducing ingredient comprises copper; and wherein the ratio of the first slag-reducing ingredient to the second slag-reducing ingredient ranges from about 95:5 to about 60:40.

2. The method of claim 1, wherein the first slag-reducing ingredient is magnesium hydroxide.

3. The method of claim 1, wherein the second slag-reducing ingredient is selected from the group consisting of copper acetate, copper nitrate, and a combination thereof.

4. The method of claim 1, wherein the first and second slag-reducing ingredients are present at up to about 2000 ppm by weight based upon the weight of the coal as received.

5. The method of claim 1, wherein the first and second slag-reducing ingredients are present at from about 100 ppm to about 1000 ppm by weight based upon the weight of the coal as received.

6. The method of claim 1, wherein the ratio of the first slag-reducing ingredient to the second slag-reducing ingredient ranges from about 90:10 to about 80:20.

7. The method of claim 1, wherein rate of formation of slag is reduced by a factor of about 10 to about 100 compared to the presence of the first slag-reducing ingredient alone.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The present invention affords reduced slagging in the operation of coal-fired furnaces.

(2) The first slag-reducing ingredient functions to reduce slag formation relative to combustion without such first slag-reducing ingredient. The first slag-reducing ingredient is selected from among magnesium carbonate, magnesium hydroxide, magnesium sulfate, magnesium oxide, and combinations thereof. A preferred first slag-reducing ingredient is magnesium hydroxide. The first slag-reducing ingredient may also function as a combustion catalyst to improve the oxidation of the coal.

(3) The second slag-reducing ingredient acts synergistically with the first slag-reducing ingredient to significantly reduce slag formation relative to combustion with the first slag-reducing ingredient alone. The rate of formation of slag with the second slag-reducing ingredient is preferably reduced by a factor of about 10 to about 100 compared to the presence of the first slag-reducing ingredient alone.

(4) The second slag-reducing ingredient is selected from among copper acetate, copper nitrate, aluminum nitrate, aluminum oxide, aluminum hydroxide, and ammonium phosphate. Preferred ingredients are copper acetate, copper nitrate, and a combination thereof.

(5) The first and second slag-reducing ingredients are added to the coal in amounts preferably up to about 2000 ppm based upon the weight of ash in the coal, which is typically about 2 wt % to about 3 wt % of the total weight of the coal. The composition and proportion of ash in the coal will vary from coal sample to coal sample. The indicated upper limit is preferred due to economic considerations, but higher amounts are operable and possible. A more preferred range is about 100 ppm to about 1000 ppm based upon the weight of the coal as received. A most preferred range is about 500 ppm to about 750 ppm based upon the weight of the coal as received. The ratio of the first slag-reducing ingredient to the second slag-reducing ingredient preferably ranges from about 95:5 to about 60:40 and more preferably about 90:10 to about 80:20.

(6) The first and second ingredients may be added directly into the furnace or boiler in powder or liquid forms or added to the coal as received prior to conveyance of the coal to the furnace or boiler. Suitable liquid forms include solutions and slurries. A preferred solvent or vehicle is water. A liquid is preferably sprayed onto the coal prior to bunkering or in the gravimetric feeders prior to pulverization or prior to the cyclone.

(7) It should be understood that the foregoing description is only illustrative of the present invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances that fall within the scope of the appended claims.