SHAFT FURNACES

• US 3,601,377 A
• Filed: 03/24/1969
• Issued: 08/24/1971
• Est. Priority Date: 03/29/1968
• Status: Expired due to Term

• Current Assignee: Edward Charles Jope
• Original Assignee: Edward Charles Jope
• Inventors: Jope, Edward Charles
• Primary Examiner(s): Camby, John J.
• Application Number:
  US04/809,876
• Time in Patent Office: 883 Days
• Field of Search: 263/29,30,53 266/25 34/174
• US Class Current: 432/18
• CPC Class Codes: F27B 1/005 wherein no smelting of the charge occurs, e.g. calcining or sintering furnaces

Abstract

An apparatus for the calcination of a mineral, for example lime, magnesite or dolomite which consists of a fuel oil-fired furnace provided with two parallel shafts. Each of the shafts communicate with one or more gas bypass passages one of which is common to both shafts, which enables the downwardly moving charge to be isolated from the upwardly flowing furnace gases at a point in the furnace where a high degree of temperature uniformity is necessary in the charge.

Claims

1. A shaft furnace for converting a mineral to a calcined mineral with the production of gas, said furnace comprising two substantially parallel and vertical shafts of substantially rectangular cross section lined with refractory material said refractory material forming a single dividing wall between said shafts and three external walls of each shaft, each shaft being provided close to its upper end with an inlet means for said mineral and with an exit means for said gas and close to its lower end with an exit means for said calcined mineral, a heavy fuel oil gasifyer protruding into each shaft between said inlet means and said calcined mineral exit means, each shaft being provided with means for the introduction of recirculated furnace gas and air at various levels in the furnace wherein a gas passage common to both shafts is constructed in said dividing wall, said gas passage bypassing a preheat soaking zone in each of said shafts and being provided with means for the introduction of a free oxygen containing gas and wherein the two refractory external walls opposite said dividing wall are each provided with a gas passage which bypasses a preheat soaking zone in each of said shafts.

2. A shaft furnace for converting a mineral to a calcined mineral with the production of gas, said furnace comprises a substantially vertical shaft lined with refractory material, said shaft being provided close to its upper end with an inlet means for said mineral and with an exit means for said gas and close to its lower end with an exit means for said calcined mineral, fuel-burning means opening into said shaft between said inlet means and said calcined mineral exit means, a soaking zone in said shaft, at least one gas passage bypassing said soaking zone, the entry point for said gases into said gas passage being at a level in said shaft above the calcining zone and the exit point from said gas passage for said gases to reenter said shaft being at a higher level in said shaft, said higher level marking the upper boundary of said soaking zone and the lower boundary of the preheating zone.

3. A shaft furnace according to claim 2 comprising at least two gas passages, the gas entry and exit points of at least one of said gas passages being respectively at a level in the kiln above the gas entry and exit points of at least one of the remaining gas passages.

4. A shaft furnace according to claim 2 wherein there are two of said shafts and at least one of said gas passages is constructed in a dividing wall between said shafts to communicate with both shafts and bypasses a soaking zone in each of said shafts.

5. A shaft furnace according to claim 2 wherein means for the controlled introduction of a free-oxygen-containing gas is provided in said gas passage.

6. A shaft furnace for converting a mineral to a calcined mineral with the production of gas, said furnace comprising two substantially parallel and vertical shafts of substantially rectangular cross section lined with refractory material, said refractory material forming a single dividing wall between said shafts and three external walls of each shaft, each shaft being provided close to its upper end with an inlet means for said mineral and with an exit means for said gas and close to its lower end with an exit means for said calcined mineral, a heavy fuel oil gasifyer opening into each shaft between said inlet means and said calcined mineral exit means, each shaft being provided with means for the introduction of recirculated furnace gas and air at various levels in the furnace, a soaking zone in each of said shafts, a gas passage common to both shafts in said dividing wall bypassing said soaking zone, means for the introduction of a free oxygen containing gas into said gas passage and two refractory external walls opposite said dividing wall each provided with a gas passage bypassing a preheat soaking zone in each of said shafts.

7. A shaft furnace according to claim 6 wherein the gas entry and exit points of the gas passages constructed in the external walls are respectively at a level in the kiln above the gas entry and exit points of said gas passage constructed in the dividing wall.

8. A continuous process for calcining a mineral comprising the steps of a. charging said mineral to a shaft furnace. b. heating said mineral in a preheating zone of said furnace by contacting said mineral with hot gas rising through said furnace. c. passing the heated mineral to a soaking zone of said furnace in which contact with said hot gas is prevented. d. burning said mineral to a calcined mineral in a burning zone of said furnace with the production of gas. e. cooling said calcined mineral in a cooling zone of said furnace. f. withdrawing said calcined mineral from the bottom of said furnace wherein the gases produced in said burning zone are continuously withdrawn through the mass of mineral in the furnace except in the soaking zone of the furnace which the gas bypasses by means of at least one gas passage.

9. A process according to claim 8 wherein the depth of the soaking zone is controlled by passing a proportion of the gases through at least one gas passage, the gas entry and exit points of which gas passage are respectively at a level in the kiln above the gas entry and exit points of at least one of the remaining gas passages.

10. A process according to claim 8 wherein the mineral is limestone of from about 1 inch to 2 inches in diameter.