Method and apparatus for reducing the nox emissions in a rotary kiln

Patent metadata

Field	Value
Publication number	US-2018252473-A1
Application number	US-201615758191-A
Country	US
Kind code	A1
Filing date	Aug 30, 2016
Priority date	Sep 8, 2015
Publication date	Sep 6, 2018
Grant date	—

Abstract

In a method for reducing the NOx emissions of a rotary kiln of a clinker production plant, fuel supplied through a burner of the rotary kiln is burned along with primary air fed through the burner, wherein the primary air has a lower oxygen content and the primary air has an oxygen content reduced relative to that of the ambient air and a temperature increased relative to that of the ambient air, and the primary air is obtained by mixing ambient air with exhaust gas from the rotary kiln or from a heat exchanger connected to the rotary kiln and used for preheating raw meal. The primary air is further obtained by mixing with hot air, in particular waste air from a clinker cooler.

First claim

1 . A method for reducing the NOx emissions of a rotary kiln of a clinker production plant, in which fuel supplied through a burner of the rotary kiln is burned along with primary air fed through the burner and the primary air has an oxygen content reduced relative to that of the ambient air and a temperature increased relative to that of the ambient air, the primary air being obtained by mixing ambient air with exhaust gas from the rotary kiln or from a heat exchanger connected to the rotary kiln and used for preheating raw meal, wherein the primary air is further obtained by mixing with hot air.

2 . A method according to claim 1 , wherein the mixing ratio of ambient air, exhaust gas and hot air is controlled such that the primary gas is fed to the burner at a temperature of 50-250° C. and an oxygen content of 8-18% by vol.

3 . A method according to claim 1 , wherein the mixing of ambient air, exhaust gas and hot air is controlled to maintain a volume flow of primary gas adapted to the process.

4 . A method according to claim 1 , wherein hot air is used at a temperature of 80-150° C.

5 . A method according to claim 1 , wherein exhaust gas is used at a temperature of 100-200° C.

6 . A method according to claim 1 , wherein exhaust gas with an oxygen content of 6-10% by vol. is used.

7 . A method according to claim 1 , wherein 5-20% by vol. of primary gas, and 80-95% by vol. of secondary gas, are fed to the rotary kiln.

8 . A method according to claim 1 , wherein a portion of the primary gas is used as transport gas for fuels.

9 . A device for carrying out the method according to claim 1 , comprising a rotary kiln with a burner, a heat exchanger connected to the rotary kiln on the exhaust-gas side, and a clinker cooler, wherein a primary gas supply for the burner with a main fan is provided, wherein a mixing device including an ambient air supply, an exhaust gas supply fed with the exhaust gas from the heat exchanger, and a hot air supply fed with the waste air from the clinker cooler are disposed upstream of the main fan.

10 . A device according to claim 9 , wherein the ambient air supply, the exhaust gas supply and the hot air supply are each equipped with a control element for controlling the respective volume flow, wherein the control elements are connected to a control device to which measurements of a temperature sensor and oxygen-content sensor disposed downstream of the main fan are fed, wherein the control device is arranged to adjust the control elements such that a specified temperature and a specified oxygen content of the primary gas supplied to the burner are maintained.

11 . A device according to claim 9 , wherein the control device is arranged to adjust the control elements such that a specified volume flow of the primary gas supplied to the burner is maintained.

12 . A method according to claim 1 , wherein the hot air is waste air from a clinker cooler.

13 . A method according to claim 2 , wherein the mixing ratio of ambient air, exhaust gas and hot air is controlled such that the primary gas is fed to the burner at a temperature of 100-150° C.

14 . A method according to claim 2 , wherein the oxygen content is of 13-16% by vol.

15 . A method according to claim 4 , wherein hot air is used at a temperature of 90-100° C.

16 . A method according to claim 5 , wherein exhaust gas is used at a temperature of 145-185° C.

17 . A method according to claim 6 , wherein exhaust gas with an oxygen content of 6-8% by vol. is used.

18 . A method according to claim 10 , wherein the specified temperature is 50-250° C. and the specified oxygen content is 8-18% by vol.

19 . A method according to claim 18 , wherein the specified temperature is 100-150° C.

20 . A method according to claim 18 , wherein the specified oxygen content is 13-16% by vol.

Assignees

• Holcim Technology Ltd

Inventors

• Gafner Irwin

Classifications

• C04B7/364

  Avoiding environmental pollution during cement-manufacturing · CPC title

• F23L7/00

  Supplying non-combustible liquids or gases, other than air, to the fire, e.g. oxygen, steam · CPC title

• F23D14/02

  Premix gas burners, i.e. in which gaseous fuel is mixed with combustion air upstream of the combustion zone · CPC title

• F27B7/00 Primary

  Rotary-drum furnaces, i.e. horizontal or slightly inclined · CPC title

• F23D99/00

  Subject matter not provided for in other groups of this subclass · CPC title