초록 ▼

During combustion of a water-vapor generating sulfur-containing fuel, the pressurized flue gases are cooled, while extracting the main part of the latent heat of evaporation of the water vapor included and while removing sulfur impurities, using a coolant liquid in drop form in a scrubber. After hav

During combustion of a water-vapor generating sulfur-containing fuel, the pressurized flue gases are cooled, while extracting the main part of the latent heat of evaporation of the water vapor included and while removing sulfur impurities, using a coolant liquid in drop form in a scrubber. After having passed through the scrubber, the flue gases are mixed with a proportion of heated flue gases, which have previously passed through the scrubber, so that the temperature of the flue gases after said mixing exceeds the dew point for sulfuric acid in the flue gases. The flue gases are then heated in a heat exchanger and are thereafter expanded in an expansion machine to atmospheric pressure while reducing their temperature again without falling below the dew point for sulfuric acid.

대표청구항 ▼

1. A method for recovering energy from flue gases created during the combustion of a sulfur-containing, water-vapor generating fuel, in which pressurized flue gases are cooled while recovering a major part of the latent heat of evaporation of the water contained therein and while at least partially

1. A method for recovering energy from flue gases created during the combustion of a sulfur-containing, water-vapor generating fuel, in which pressurized flue gases are cooled while recovering a major part of the latent heat of evaporation of the water contained therein and while at least partially removing sulfur impurities contained in the flue gases, before the flue gases are expanded to atmospheric pressure in an expansion machine, characterized in that the cooling while recovering the latent heat of evaporation of water and while removing sulfur impurities is carried out by scrubbing with a flow of coolant liquid in drop form, in that the flue gases, after scrubbing are mixed with a proportion of heated flue gases which has been scrubbed previously and then had its temperature raised in a heat exchanger, so that the temperature of the flue gases after said mixing exceeds the dew point for sulfuric acid in the flue gases under the prevailing conditions, in that the flue gases, after such temperature enhancement, are led to a heat exchanger and in that thereafter the flue gases are expanded to atmospheric pressure in the expansion machine under conditions in which the temperature reduction produced by the expansion does not cause the flue gases temperature to fall below the dew point for sulfuric acid in the flue gases under the then prevailing conditions. 2. A method according to claim 1, characterized in that before the flue gases are cooled by scrubbing they are cooled in the said heat exchanger without the temperature falling below the dew point for sulfuric acid in the flue gases under the then prevailing conditions. 3. A method according to claim 1, characterized in that the combustion is carried out with compressed air and that water is supplied with the compressed air. 4. A method according to claim 2, characterized in that the combustion is carried out with compressed air and that water is supplied with the compressed air. 5. A method according to claim 1, characterized in that the flue gases at the inlet of the expansion machine have a temperature of at least 150° C. 6. A method according to claim 2, characterized in that the flue gases at the inlet of the expansion machine have a temperature of at least 150° C. 7. A method according to claim 3, characterized in that the flue gases at the inlet of the expansion machine have a temperature of at least 150° C. 8. A method according to claim 4, characterized in that the flue gases at the inlet of the expansion machine have a temperature of at least 150° C. 9. A method according to claim 1, characterized in that the flue gases at the outlet of the expansion machine have a temperature which exceeds ambient temperature. 10. A method according to claim 2, characterized in that the flue gases at the outlet of the expansion machine have a temperature which exceeds ambient temperature. 11. A method according to claim 4, characterized in that the flue gases at the outlet of the expansion machine have a temperature which exceeds ambient temperature. 12. A method according to claim 6, characterized in that the flue gases at the outlet of the expansion machine have a temperature which exceeds ambient temperature. 13. A plant for recovering energy from flue gases created during the combustion of a sulfur-containing, water-vapor generating fuel, in which pressurized flue gases are cooled while recovering a major part of the latent heat of evaporation of the water contained therein and while at least partially removing sulfur impurities contained in the flue gases, before the flue gases are expanded to atmospheric, comprising a combustion chamber for combustion of the fuel, a scrubber, connected to the combustion chamber via a first conduit, for the flue gases, means to feed coolant liquid in drop form to the scrubber to effect cooling of the flue gases while recovering latent heat of evaporation of water contained in the flue gases and while at least partially removing sulfur trioxide and other impurities, a heat exchanger connected to the scrubber via a second conduit for the flue gases, for heating the flue gases, a third conduit connected to the second conduit for mixing, with the scrubbed flue gases, a proportion of heated flue gases which were scrubbed previously and had its temperature raised, so that the temperature of the flue gases after such mixing exceeds the dew point for sulfuric acid in the flue gases under the prevailing conditions, and an expansion machine connected to the heat exchanger via a fourth conduit for expanding the flue gases to atmospheric pressure under conditions in which the temperature reduction produced by the expansion does not cause the flue gas temperature to fall below the dew point for sulfuric acid in the flue gases under the then prevailing conditions. 14. Plant according to claim 13, in which the heat exchanger is located both in the second conduit for heating the flue gases from the scrubber and in the first conduit for cooling the flue gases flowing from the combustion chamber to the scrubber whereby interchange of heat takes place between the flue gases flowing from the scrubber and the flue gases flowing to the scrubber. 15. Plant according to claim 13, in which the combustion chamber is provided with a supply conduit for air which includes two compressors and in which means is provided to supply water to the air in the supply conduit at a point between the two compressors. 16. Plant according to claim 14, in which the combustion chamber is provided with a supply conduit for air which includes two compressors and in which means is provided to supply water to the air in the supply conduit at a point between the two compressors. 17. In a method of recovering energy from flue gases resulting from the combustion of a sulfur-containing water-vapor generating fuel in which heat energy is extracted from and sulfur impurities are removed from, the flue gases as these are cooled under pressure, the improvement which comprises effecting some heat energy extraction and impurity removal by contacting the flue gases with liquid droplets, bringing the flue gases, upstream and downstream of said droplet contact into heat exchange relationship in a heat exchanger, and returning a proportion of the flue gases flowing downstream of the heat exchanger back into the flue gases at a location upstream of the heat exchanger but downstream of the said droplet contact. 18. Combustion plant for burning a water-vapor generating fuel that contains sulfur which comprises a combustion chamber in which the fuel is burnt to create flue gases, means to supply fuel and combustion air to the combustion chamber, a first flue gas conduit leading from the combustion chamber, a scrubber connected to the first flue gas conduit with means therein to contact flue gases passing therethrough with drops of a liquid coolant, a second flue gas conduit leading from the scrubber to lead scrubbed flue gases away therefrom, a heat exchanger thermally interconnecting flue gases in said first and second flue gas conduits, a third flue gas conduit adapted to feed a proportion of the flue gases leaving the heat exchanger from the second flue gas conduit back to the second flue gas conduit at a point of the second flue gas conduit position between the scrubber and the heat exchanger, an expansion machine receiving the residue of the flue gases from the heat exchanger, and a waste stack receiving flue gas from the expansion machine. 19. Plant according to claim 18, further comprising means to pressurize the combustion air fed to the combustion chamber which means are powered by the expansion machine. 20. Plant according to claim 19, further comprising means to add water to the combustion air.