Incineration method and system

A method of incinerating partially dewatered sewage sludge containing organic wastes in a multiple hearth furnace equipped with an afterburner connected to receive gases and vapors from the furnace, said method comprising the following steps:

• a. introducing the wastes into the multiple hearth furnace and moving the same downwardly therethrough by rabbling;
• b. pyrolyzing the wastes in the furnace in an oxygen deficient atmosphere and regulating that atmosphere to only partially oxidize the substances which are pyrolyzed from the organic wastes;
• c. conveying the partially oxidized products of pyrolysis in the medium of gases and vapors from the furnace to the afterburner;
• and
• d. at temperatures within said afterburner above a predetermined first temperature introducing air into the afterburner in quantities in excess of that required to complete the oxidation of the partially oxidized substances carried by the gases and vapors from the furnace and regulating the quantity of air introduced to increase with increasing temperatures and to decrease with decreasing temperatures so as to maintain temperatures in the afterburner within a predetermined range.

A method of incinerating partially dewatered sewage sludge containing organic wastes in a multiple hearth furnace equipped with an afterburner connected to receive gases and vapors from the furnace, said method comprising the following steps:

• a. introducing the partially dewatered wastes into the multiple hearth furnace and moving the same downwardly therethrough by rabbling;
• b. introducing air and fuel into the furnace to pyrolyze the wastes and regulating the introduction of the air and fuel so that the atmosphere within the furnace is deficient in oxygen and so that the organic substances which are pyrolyzed from the wastes are only partially oxidized;
• and
• c. introducing air into the afterburner in quantities in excess of that required to complete the oxidation of the partially oxidized substances carried by the gases and vapors from the furnace and regulating the quantity of air introduced into the afterburner to maintain temperatures therein within a predetermined range.

A system for incinerating partially dewatered sewage sludge containing organic wastes comprising:

• a. a multiple hearth furnace inclusive of means for admitting the wastes into said furnace and means for moving the wastes downwardly through said furnace by rabbling;
• b. first burner means connected in communication with said furnace for introducing air and fuel thereinto for pyrolyzing the wastes;
• c. means connected to said first burner means to control the action thereof so that atmosphere within said furnace is deficient in oxygen and the organic substances which are pyrolyzed from the organic wastes are only partially oxidized;
• d. an afterburner connected to said furnace to receive the partially oxidized products of pyrolysis in the medium of gases and vapors from said furnace;
• e. second burner means connected in communication with said afterburner for introducing air and fuel thereinto for combustion;
• and
• f. afterburner control means connected to said second burner means to control the introduction of air and fuel into said afterburner to complete the oxidation of the partially oxidized substances carried by the gases and vapors from the furnace.

A system for incinerating partially dewatered sewage sludge containing organic wastes comprising:

• a. a multiple hearth furnace including (i) means for admitting the organic wastes into said multiple hearth furnace;
• (ii) means for moving the wastes downwardly through said furnace by rabbling;
• (iii) first burner means connected to introduce air and fuel into selected hearth spaces in said furnace to pyrolyze the organic wastes therein;
• (iv) temperature monitoring means mounted in each of said selected hearth spaces to monitor the temperatures therein;
• (v) oxygen monitoring means mounted in communication with said furnace to monitor the oxygen content of the gases and vapors leaving said furnace;
• (vi) first burner control means connected to each of said first burner means and responsive to signals from an associated one of said temperature monitoring means to increase the quantity of air supplied through said first burner means as temperatures in the associated hearth space decrease and to decrease the supply of air as temperatures therein increase, said first burner control means further being connected to said oxygen monitoring means and responsive to signals therefrom to stop the introduction of fuel through said first burner means when the oxygen content of the gases and vapors leaving said furnace is less than a predetermined value at the same time that the temperature within the associated hearth spaces exceeds a predetermined second value;
• b. an afterburner connected to said furnace to receive the partially oxidized products of pyrolysis in the medium of gases and vapors from said furnace and including:
• (i) second burner means connected to introduce air and fuel into the afterburner for combustion to complete the oxidation of the partially oxidized substances carried by the gases and vapors from said multiple hearth furnace;
• (ii) afterburner temperature monitoring means mounted in said afterburner to monitor the temperature therein;
• (iii) afterburner oxygen monitoring means mounted in communication with said afterburner to monitor the oxygen content of the gases and vapors therein;
• (iv) second burner control means connected to said second burner means and responsive to signals from said afterburner temperature monitoring means so that the quantity of air supplied through said second burner means is increased as temperatures in said afterburner increase and is decreased as the temperatures decrease when temperatures within said afterburner exceed a predetermined first monitored temperature, and so that the quantity of air supplied through said second burner means is decreased with increasing temperatures and is increased with decreasing temperatures at temperatures below a predetermined second monitored temperature which is below said predetermined first monitored temperature, said second burner control means further being connected to said afterburner oxygen monitoring means and responsive to signals therefrom to stop the introduction of fuel through said second burner means when the monitored oxygen content is less than a predetermined monitored value at the same time that the temperature within the afterburner exceeds said predetermined second monitored temperature.

A method of incinerating partially dewatered sewage sludge containing organic wastes in an incinerating device equipped with an afterburner connected to receive gases and vapors from the incinerating device, said method of comprising the following steps:

• a. introducing the wastes into the incinerating device;
• b. pyrolyzing the wastes in the incinerating device in an oxygen deficient atmosphere and regulating that atmosphere to only partially complete the oxidation of substances which are pyrolyzed from the wastes;
• c. conveying the partially oxidized products of pyrolysis in the medium of gases and vapors from the incinerating device to the afterburner;
• and
• d. introducing sufficient air into the afterburner to complete the oxidation of the partially oxidized substances carried by the gases and vapors from the incinerating device.

A method of incinerating partially dewatered sewage sludge containing organic wastes in a multiple hearth furnace equipped with an afterburner connected to receive gases and vapors from the furnace, said method comprising the following steps:

• a. introducing the wastes into the multiple hearth furnace and moving the same downwardly therethrough by rabbling;
• b. pyrolyzing the wastes in the furnace in an oxygen deficient atmosphere and regulating that atmosphere to only partially oxidize the substances which are pyrolyzed from the organic wastes;
• c. conveying the partially oxidized products of pyrolysis in the medium of gases and vapors from the furnace to the afterburner;
• and
• d. introducing air into the afterburner in quantities in excess of that required to complete the oxidation of the partially oxidized substances carried by the gases and vapors from the furnace and regulating the quantity of air introduced to maintain temperatures in the afterburner within a predetermined range.