Method and furnace for heat treating material

Claim 2

In a mineral furnacing apparatus having structure defining at least a chamber for preconditioning material having a material inlet opening, a chamber for preheating material, a chamber for final heating material having a material inlet opening adjacent the preheating chamber and having a material outlet opening and at least one cooling chamber having a material inlet opening adjacent the material output opening of the final heating chamber, the chambers being connected together in series flow arrangement to define a material flow stream from the preconditioning chamber to the preheating chamber, to the final heating chamber and thence to cooling chamber with the final heating chamber and the preheating chamber defining a passage for a counterflow of gas From the final heating chamber to the preheating chamber, and gas conveying means connecting said cooling chamber and said preheating chamber to said preconditioning chamber, said gas conveying means comprising: A mixing box connected to the preheating chamber in which gases at a relatively high temperature are produced in position adjacent the material inlet passage of the final heating chamber and on a side of the material stream facing the flow of gas through the passage; a first duct means connected on a first end thereof to said mixing box and connected on a second end thereof to said mixing box and connected on the a second end thereof preconditioning chamber; a preheating chamber windbox operatively disposed below the material stream; a second duct means connected on a first end thereof to the preheating chamber windbox and a second end thereof being connected to the preconditioning chamber at a location above the material stream; a third duct means connected on a first end thereof to said mixing box and connected on a second end thereof to the cooling chamber; and, moisturizing means connected to said mixing box to moisturize the gases in said mixing box; whereby the gases from the preheat chamber are tempered with gases from the cooler chamber and said mixture of tempered gases are moisturized and directed to the preconditioning chamber as preconditioning gases at a controlled temperature for drying material in the preconditioning chamber and for controlling waste gas temperature and moisture content.

Claim 3

A mineral furnacing apparatus according to claim 1 wherein there is a fourth duct means connected on a first end thereof to said third duct means at a position to bypass some of the cooling chamber gases around said mixing box, said fourth duct means on a second end thereof being connected to the windbox of the preconditioning chamber at a location on the side of the material stream opposite to the flow of the tempered moisturized gas to the material in the preconditioning chamber; and, a fifth duct means connected on a first end thereof to said first duct means at a location ahead of the connection of the second end of said first duct means with the preconditioning chamber, said fifth duct means on a second end thereof being conducted to the windbox of the preconditioning chamber on the same side thereof to which said second end of said fourth duct means is connected to the windbox of the preconditioning chamber; whereby moisturized tempered gases from said mixing box is directed to the preconditioning chamber and mixed with gases from the cooler chamber to temper the temperature of the exhaust gases from the preconditioning chamber to a desired temperature and moisture content.

Claim 4

A mineral furnacing apparatus according to claim 2 wherein there is also provided a dust collecting means operably connected to said preconditioning chamber windbox

Claim 5

A mineral funacing apparatus according to claim 1 including a fan in said third duct means between the cooling chamber and said mixing box for drawing gas out of the cooler chamber and delivering the gas to said mixing box; and, a dust collecting and discharge means in said third duct means between said cooler chamber and said fan operable to collect dust particles larger than 10 to 20 microns.

Claim 6

A mineral furnacing apparatus according to claim 2 wherein there is provided a dampener means in said fourth duct, said dampener means being operable to maintain a constant pressure in the tempering air duct to the mixing box.

Claim 7

A mineral furnacing apparatus according to claim 3 wherein said moisturized exhaust gases from said preconditioning chamber are directed into an exhaust duct connected on a first side to said preconditioning chamber windbox in a location below the material flow stream, and connected on a second end thereof to an exhaust stack; a fan in said exhaust duct means for drawing the moisturized and tempered exhaust gas froM the preconditioning chamber windbox into the stack; and, a dust precipitator connected in said exhaust duct and operable to collect particles smaller than 10 to 20 microns for removing the particles prior to the gas being directed to stack; whereby moisturized exhaust gases from the preconditioning chamber windbox at a temperature above acid dew point is drawn therefrom and passed to said precipitator for filtering prior to being passed to said stack.

Claim 8

A mineral furnacing apparatus according to claim 6 wherein said exhaust duct fan is operable to provide a negative pressure on the order of 2 to 16 inches of water column in the preconditioning chamber windbow at the below the stream of material.

Claim 9

In a process for heat treating material in a material treating furnace arrangement in which a stream of material is progressed through a preconditioning chamber, a preheat chamber, a final heating chamber in which gases and volatilized alkalies are produced from the material therein and a cooler chamber in which gases from material being cooled are recouped and passed to the final heating chamber; comprising the steps of: A. bypassing a first portion of the gases and volatilized alkalies produced in the final heating chamber away from the material in the preheat chamber; B. tempering the first portion of the gases and volatilized alkalies with low temperature recouped gases from the cooler chamber; C. mixing the first portion of the gases and volatilized alkalies from the final heating chamber with the low temperature gases from the cooling chamber; D. moisturizing the mixture of gases of step C; E. directing a portion of the moisturized gases to the preconditioning chamber; F. drawing a second portion of the gases from the final heating chamber into contact with material in the preheating chamber; G. drawing the second portion of gases from the final heating chamber that has contacted the material in the preheating chamber through the material; H. admitting a supply of auxiliary heat into the preheating chamber and into contact with the second portion of the gases from the final heating chamber after the first portion of the gases from the final heating chamber has been directed away from the second portion gases and as the second portion of gas is drawn through the material in the preheating chamber; I. joining the gases which have passed through the material in the preheating chamber with a first portion of the moisturized gases of step E to heat the material in the preconditioning chamber; J. drawing the material heating gases in the preconditioning chamber through the material therein for exhausting the gas and also drawing a second portion of the moisturized gases and a second portion of the gas from the cooler chamber into the winbox of the preconditioning chamber to raise the temperature of the exhaust gas that has passed through the material in the preconditioning chamber before passing the exhaust gases to stack, so that the temperature of the gases passing to stack are above acid dew point and have a 10 percent or higher moisture content by volume.

Claim 10

In a process for heat treating material in a material treating furnace arrangement in which a stream of material is progressed through a preconditioning chamber, a preheat chamber, a final heating chamber in which gases and volatilized alkalies are produced from the material therein and a cooler chamber in which gases from material being cooled are recouped and passed to the final heating chamber; comprising the steps of: A. bypassing a first portion of the gases and volatilized alkalies produced in the final heating chamber away from the material in the preheat chamber; B. tempering the first portion of the gases and volatilized alkalies with low temperature recouped gases from the cooler chamber; C. mixing the first portion of the gases and volatilized alkalies from the final heating chamber with the low temperature gases from the cooling chamber; D. moisturizing the mixture of gases of step C; E. directing a portion of the moisturized gases to the preconditioning chamber; F. drawing a second portion of the gases from the final heating chamber into contact with material in the preheating chamber; G. drawing the second portion of gases from the final heating chamber that has contacted the material in the preheating chamber through the material; H. admitting a supply of auxiliary heat into the preheating chamber and into contact with the second portion of the gases from the final heating chamber after the first portion of the gases from the final heating chamber has been directed away from the second portion gases and as the second portion of gas is drawn through the material in the preheating chamber; I. joining the gases which have passed through the material in the preheating chamber with a first portion of the moisturized gases of step E to heat the material in the preconditioning chamber; J. drawing the material heating gases in the preconditioning chamber through the material therein for exhausting the gas and also drawing a second portion of the moisturized gases and a second portion of the gas from the cooler chamber into the winbox of the preconditioning chamber to raise the temperature of the exhaust gas that has passed through the material in the preconditioning chamber before passing the exhaust gases to stack, so that the temperature of the gases passing to stack are above acid dew point and have a 10 percent or higher moisture content by volume.

Claim 11

In a process for conditioning waste exhaust gases from a material heat treating furnace having a material preconditioning section including a windbox, a material preheat section, a kiln and a cooler; comprising the steps of: A. passing a varying amount of bypass gas from the cooler sections of the furnace to the windbox of the preconditioning section; and, B. blending the combined bypass gas and spent off-gas from the preconditioning section with off-gases from the preheat section in the windbox of the preconditioning section to establish a minimum temperature of the waste exhaust gas.

Claim 12

In a process for conditioning waste exhaust gases from a material heat treating furnace having a material preconditioning section including a windbox, a material preheat section, a kiln and a cooler; comprising the steps of: A. passing a varying amount of bypass gas from the cooler sections of the furnace to the windbox of the preconditioning section; and, B. blending the combined bypass gas and spent off-gas from the preconditioning section with off-gases from the preheat section in the windbox of the preconditioning section to establish a minimum temperature of the waste exhaust gas.

Claim 13

A process for conditioning waste exhaust gas according to claim 9; including the additional steps of: moisturizing said bypass gas; and, wherein the blending of the gases in the winDbox of the preconditioning section is controlled to establish the minimum volume of exhaust gas and at a temperature above acid dew point and with a minimum moisture content of 10 percent or higher by volume.