Process for calcining mineral rock in a regenerative parallel-flow vertical shaft furnace, and furnace used

Patent metadata

Field	Value
Publication number	US-11280546-B2
Application number	US-201615765002-A
Country	US
Kind code	B2
Filing date	Oct 5, 2016
Priority date	Oct 6, 2015
Publication date	Mar 22, 2022
Grant date	Mar 22, 2022

Abstract

Process for calcining mineral rock in a regenerative parallel-flow vertical shaft furnace, containing at least two shafts ( 1, 2 ) interconnected by a gas transfer channel ( 3 ), each shaft operating alternately in firing mode and in preheating mode, the firing mode comprising a combustion of fuel in the presence of air so as to obtain a firing of the rock to give calcined rock, an emission of combustion gases, and a passage of these gases from one shaft to the other by means of said channel ( 3 ), the preheating mode comprising a heat exchange between said rock and said combustion gases from said channel ( 3 ), this process additionally comprising an injection of supplementary air into said channel ( 3 ) with oxidation of unburnt products contained in the combustion gases passing through this channel.

First claim

The invention claimed is:

1. Method for calcining mineral rock in a regenerative parallel-flow vertical shaft furnace, wherein two shafts are interconnected by a gas transfer channel, wherein said gas transfer channel is a crossover channel that directly connects one shaft to the remaining shaft of the two shafts of said vertical shaft furnace or said gas transfer channel is formed from a crossover channel that connects peripheral channels arranged around each shaft in such a way as to allow an access to combustion gases from each shaft in the crossover channel, and wherein the furnace further comprises a source of air, oxygen enriched air, or oxygen and an injection device connected to the source of air, oxygen enriched air, or oxygen and arranged to inject the air, oxygen enriched air, or oxygen from said source of air, oxygen enriched air, or oxygen into said gas transfer channel wherein:
the injection device comprises at least one straight perforated injection unit introduced into the crossover channel and supplied by said source of air, oxygen enriched air, or oxygen, said injection unit comprises one or several orifices oriented to inject the air, oxygen enriched air, or oxygen from said source of air, oxygen enriched air, or oxygen towards a top portion of the crossover channel; or
the crossover channel has a ceiling and a longitudinal axis (L) and the injection device for injecting air, oxygen enriched air, or oxygen from said source of air, oxygen enriched air, or oxygen comprises one or several openings provided in the ceiling of the crossover channel through which the air, oxygen enriched air, or oxygen can be supplied from said source of air, oxygen enriched air, or oxygen;

the method comprising the steps of:
loading a mineral rock at the top of the shafts, and
unloading a calcined mineral rock at the bottom of the shafts,
operating each shaft alternately in firing mode and in preheating mode, with one shaft being in firing mode for a predetermined period of time while the other shaft is in preheating mode, and inversely,
firing the mineral rock, in the shaft in firing mode, comprising a combustion of fuel in the presence of gas containing oxygen so as to obtain the calcined mineral rock, an emission of combustion gases, and a passage of these combustion gases from the shaft in firing mode to the other shaft in preheating mode by means of said gas transfer channel,
preheating said mineral rock, in the shaft in preheating mode, comprising a heat exchange between said mineral rock and said combustion gases from said gas transfer channel,

wherein the method further comprises a step of injecting, air, oxygen enriched air, or oxygen from said source of air, oxygen enriched air, or oxygen into said gas transfer channel so as to oxidize unburnt products contained in the combustion gases passing through the gas transfer channel.

2. Method according to claim 1 , wherein the gas containing oxygen supplied to a shaft in firing mode is in the form of a gas containing primary oxygen, conveyed simultaneously to the fuel, and a gas containing secondary oxygen is introduced at the top of the shaft in firing mode through the rock to be fired.

3. Method according to claim 1 , wherein said oxidation of unburnt products is carried out at an oxidation temperature that is high enough to allow for an oxidation of carbon monoxide and low enough to prevent a thermal degradation of molecules of dinitrogen into atomic nitrogen.

4. Method according to claim 3 , wherein said oxidation temperature is between 800° C. and 1,300° C.

5. Method according to claim 1 , wherein the quantity of air, oxygen enriched air, or oxygen injected into said gas transfer channel using said air, oxygen enriched air, or oxygen is between 0.1 and 50 times the stoichiometric quantity of oxygen calculated based on the quantity of CO measured at the outlet of the furnace in the absence of said air, oxygen enriched air, or oxygen.

6. Method according to claim 1 , wherein the air, oxygen enriched air, or oxygen injected into said gas transfer channel contains at least one combustion catalyst.

7. Method according to claim 1 , wherein the air, oxygen enriched air, or oxygen injected into said gas transfer channel is injected into the crossover channel at an equal distance from the shafts that it interconnects.

8. Method according to claim 1 wherein the fuel is conveyed into the shaft in firing mode by lances that produce parallel beams of streams of fuel that undergo the combustion and form lines of combustion gases that pass through the crossover channel, with an injection of the aforementioned air, oxygen enriched air, or oxygen into said gas crossover channel being carried out on each one of these lines of combustion gas.

9. Method according to claim 1 , wherein said injection of air, oxygen enriched air, or oxygen takes place in the crossover channel, in the peripheral channels or in both the crossover channel and the peripheral channels.

10. Method according to claim 1 , wherein the furnace comprises three shafts and three gas transfer channels wherein each gas transfer channel interconnects two of said aforementioned shafts, and wherein one shaft of the three shafts is in firing mode for a predetermined period of time while the remaining shafts are in preheating mode.

11. A regenerative parallel-flow vertical shaft furnace for the production of calcined mineral rock, the furnace comprising:
two shafts interconnected by a gas transfer channel,
with each one of said shafts comprising:
at least one device for supplying fuel,
at least one supply of gas containing oxygen for combustion of the fuel,
an inlet for loading of mineral rock and
an outlet for unloading of calcined mineral rock produced, and
an exhaust stack for removal of combustion gases,

wherein the gas transfer channel is a crossover channel that directly connects one shaft to the remaining shaft of the two shafts of said vertical shaft furnace or is formed from a crossover channel that connects peripheral channels arranged around each shaft in such a way as to allow an access to combustion gas from each shaft in the crossover channel, and wherein the furnace further comprises a source of air, oxygen enriched air, or oxygen and an injection device connected to the source of air, oxygen enriched air, or oxygen and arranged to inject the air, oxygen enriched air, or oxygen from said source of air, oxygen enriched air, or oxygen into said gas transfer channel; wherein:
the injection device comprises at least one straight perforated injection unit introduced into the crossover channel and supplied by said source of air, oxygen enriched air, or oxygen, said injection unit comprises one or several orifices oriented to inject the air, oxygen enriched air, or oxygen towards a top portion of the crossover channel; or
the crossover channel has a ceiling and a longitudinal axis (L) and the injection device for injecting air, oxygen enriched air, or oxygen comprises one or several openings provided in the ceiling of the crossover channel through which the air, oxygen enriched air, or oxygen can be supplied from said source of air, oxygen enriched air, or oxygen.

12. Furnace according to claim 11 , wherein the crossover channel has a longitudinal axis (L) and said at least one straight perforated injection unit is placed transversely with respect to the longitudinal axis of the crossover channel.

13. Furnace according to claim 11 , wherein said injection unit is introduced into the crossover channel by an opening that is equally distant from said shafts.

14. Furnace according to claim 11 , wherein the

Assignees

• Lhoist Rech Et Developpement Sa

Inventors

• Habib Ziad
• Padox Guilhem

Classifications

• C04B2/02

  Lime {(obtaining Ca(OH)2 otherwise than by simple slaking of quick lime C01F11/02)} · CPC title

• C04B2/12

  in shaft or vertical furnaces (shaft or vertical furnaces in general F27B1/00) · CPC title

• F27B1/24

  Cooling arrangements · CPC title

• F27B1/04

  Combinations or arrangements of shafts · CPC title

• F27D7/02

  Supplying steam, vapour, gases or liquids · CPC title