CN111141149A - Reduce rotary kiln waste gas NOxMethod (2) - Google Patents

Reduce rotary kiln waste gas NOxMethod (2) Download PDF

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Publication number
CN111141149A
CN111141149A CN201911338995.1A CN201911338995A CN111141149A CN 111141149 A CN111141149 A CN 111141149A CN 201911338995 A CN201911338995 A CN 201911338995A CN 111141149 A CN111141149 A CN 111141149A
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Prior art keywords
rotary kiln
coal
nox
secondary air
injection amount
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CN201911338995.1A
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董武斌
张顺元
闫伟超
张金园
李永明
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D1/00—Burners for combustion of pulverulent fuel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
    • F23L9/00—Passages or apertures for delivering secondary air for completing combustion of fuel 
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N1/00—Regulating fuel supply
    • F23N1/02—Regulating fuel supply conjointly with air supply

Abstract

The invention discloses a method for reducing NOx in waste gas of a rotary kiln, which reduces the concentration of NOx by controlling the air-coal ratio of the rotary kiln coal dust combustion, wherein the main oxygen content of the rotary kiln coal dust combustion comes from secondary air volume, and the air-coal ratio can be changed by adjusting the coal injection amount or the secondary air volume. According to the invention, the coal injection amount per hour is increased, the lime heat consumption is increased, the secondary air quantity of the rotary kiln is reduced, the secondary air quantity is adjusted to be 6 times of the coal injection amount, the NOx concentration of the pulverized coal combustion of the rotary kiln is effectively reduced, and the emission requirement of environmental protection on NOx is met.

Description

Reduce rotary kiln waste gas NOXMethod (2)
Technical Field
The invention belongs to the technical field of environmental protection, and particularly relates to a method for reducing NO in waste gas of a rotary kilnXThe method of (1).
Background
The nitrogen oxides formed by combustion generally come from two main aspects: the oxidation of nitrogen in the air (combustion air) used for combustion, and the oxidation of nitrogen oxides contained in the fuel during the combustion processThermal decomposition oxidation, the thermal decomposition temperature of nitrogen in the fuel is lower than the combustion temperature of coal powder, and combustion type NO can be generated at 600-800 DEG CX，It accounts for 60-80% of nitrogen oxides in pulverized coal combustion, wherein volatile matter combustion accounts for a large part of combustion type nitrogen oxides, the NOx conversion amount is increased when fuel volatile matter is increased, the NOx conversion rate of the volatile matter is increased along with the square of oxygen concentration, and the higher the flame temperature is, the larger the NOx conversion amount is.
The nitrogen oxides are main constituents of acid rain and greenhouse gases and have certain harm to human bodies, so the nitrogen oxides in the flue gas discharged by the rotary kiln need to be treated to meet the emission requirement.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for reducing the exhaust gas NO of a rotary kilnXThe method can effectively reduce the concentration of NOx in the kiln tail waste gas of the rotary kiln, overcomes the defect that the NOx in the waste gas of the existing rotary kiln exceeds the standard, and can not reach the condition that the NOx is less than 240mg/m in an environment-friendly way3The requirements of (1).
In order to achieve the purpose of the invention, the technical scheme is as follows:
a method for reducing NOx in waste gas of a rotary kiln is characterized in that the concentration of NOx is reduced by controlling the air-coal ratio of coal powder combustion of the rotary kiln, the main oxygen content of the coal powder combustion of the rotary kiln is derived from secondary air volume, and the air-coal ratio can be changed by adjusting the coal injection amount or the secondary air volume.
Preferably, the coal injection amount is adjusted to improve the coal injection amount per hour and increase the lime heat consumption.
Preferably, the secondary air quantity is adjusted to reduce the secondary air quantity of the rotary kiln.
Preferably, the secondary air quantity is 6 times of the coal injection quantity.
More preferably, the lime heat consumption control standard is 1050-1150 Kcal/Kg.
The invention has the beneficial effects that: the concentration of NOx is reduced by controlling the air-coal ratio of the rotary kiln coal powder combustion, the main oxygen content of the rotary kiln coal powder combustion is derived from the secondary air quantity, the heat consumption of lime is increased by improving the hourly coal injection quantity, the secondary air quantity of the rotary kiln is reduced, and the secondary air quantity is adjustedThe coal injection amount is 6 times, the NOx concentration of the pulverized coal combustion of the rotary kiln is effectively reduced, and the aim of environmental protection on NOx less than 240mg/m is achieved3The requirements of (1).
Detailed Description
The following examples are intended to further illustrate the present invention and should not be construed as limiting the scope of the invention, and other insubstantial modifications and adaptations of the invention by those skilled in the art based on the teachings herein are intended to be covered thereby.
Examples
A method for reducing NOx in waste gas of a rotary kiln is characterized in that the concentration of NOx is reduced by controlling the air-coal ratio of coal powder combustion of the rotary kiln, the main oxygen content of the coal powder combustion of the rotary kiln is derived from secondary air volume, and the air-coal ratio can be changed by adjusting the coal injection amount or the secondary air volume.
The coal injection amount is adjusted to improve the coal injection amount per hour and increase the lime heat consumption.
And adjusting the secondary air quantity to reduce the secondary air quantity of the rotary kiln.
The secondary air quantity is 6 times of coal injection quantity.
The lime heat consumption control standard is 1050-1150 Kcal/Kg.
According to the environmental protection requirement, Tai Xin Yu resource Limited company, Tai Xin Yu 2 rotary kilns and a kiln tail waste gas online monitoring system are installed in 2017 in 5 months, and the Tai Xin Yu resource Limited company in Shanxi province is put into operation in 2017 in 7 months. In 2017, month 7 to month 12, NOx at the kiln tail of the rotary kiln 1# and the rotary kiln 2# continuously exceed the standard, and the average month of the rotary kiln 1# is 200-3Average 259-322mg/m in 2# rotary kiln3The environmental protection to NOx is less than 240mg/m3The requirements of (1).
The oxygen content in the rotary kiln combustion mainly comes from secondary air volume, so different air-coal ratio calcination tests are carried out in a No. 2 rotary kiln, and the nitrogen oxides, the rotary kiln secondary air volume, the coal injection quantity, the CO concentration and the O concentration are searched2The correlation between the process parameters such as content, air-coal ratio and the like is shown in the table 1.
TABLE 1 statistical table relating NOx to main parameters of rotary kiln
Figure BDA0002331738430000031
As can be seen from Table 1:
(1) the higher the coal injection quantity is, the lower the NOx is;
(2) the higher the CO concentration, the lower the NOx;
(3) the lower the oxygen content, the lower the NOx;
(4) the lower the wind-coal ratio, the lower the NOx;
(5) the relationship between the kiln head, the center and the exhaust gas temperature and NOx is not obvious and is not considered.
And (5) drawing a conclusion that: the wind-coal ratio is inversely proportional to the coal injection quantity, so the above factors can be finally summarized as: the coal injection quantity is increased, the oxygen content is reduced, and the NOX concentration can be reduced.
And (3) calculating the concentration of NOx in the kiln tail waste gas of the rotary kiln:
the principle of NOx generation is as follows:
CaCO3＝CaO+CO2
C+O2＝CO2
N2+O2＝2NO
2NO+O2＝2NO2
when the rotary kiln is in operation, the ore consumption is 87.5t/h, the raw coal consumption is 8.25t/h, the carbon content in the raw coal is 55 percent, and the primary air quantity is controlled to be 4650Nm3The secondary air quantity is controlled to be 40800-3The coal injection air volume is 2250Nm3The nitrogen content in air is about 78% and the oxygen content about 21%. The total air volume is about 47700 Nm and 66100Nm3H, an hourly nitrogen content of about 37206-51558Nm3The oxygen content is about 10017-13881Nm3。
a. O consumed by combustion of coal fines2M1Comprises the following steps:
Figure BDA0002331738430000041
under the standard condition, 1m3O2Equal to 1.43kg, O2Consumption amount of Q1Comprises the following steps: q1＝12.1×1000÷1.43＝8461m3/h；
b. Residual O2Hourly content-total air volume-O2The consumption of (10017-13881) -8461 of (1556-5420) Nm3；
c. Residual O2Hourly production of NO hourly O2Comprises the following steps:
Figure BDA0002331738430000042
Figure BDA0002331738430000043
under the standard condition, 1m3NO equals 1.27kg, so the amount of NO produced M2Comprises the following steps: m21.27 × (2918-10162) ═ 3706-12906 kg, according to 200000Nm in kiln tail exhaust gas3Air volume calculation, the hour NO concentration rho (NO) ((3706-12906) × 1000 ÷ 200000 ═ 18.53-64.53) mg/Nm3。
And the excess air coefficient is controlled by reducing the secondary air quantity of the rotary kiln. Revising the control standard of the secondary air quantity of the key process control parameter, controlling the secondary air quantity to be 6 times of coal injection quantity, and controlling the total air quantity to be about 50000Nm3/h。
Through project implementation, the NOx content of kiln tail exhaust gas of No. 1 rotary kiln is 279.6mg/m3The reduction is 51.56mg/m3And the concentration of the tail exhaust gas NOx of the 2# rotary kiln is 235mg/m3The reduction is 45.64mg, and the NOx is not less than 240mg/m3The requirements of (1).
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement or combination made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims (5)

1. A method for reducing NOx in rotary kiln exhaust gas is characterized by comprising the following steps: the method reduces the concentration of NOx by controlling the air-coal ratio of the rotary kiln coal powder combustion, the main oxygen content of the rotary kiln coal powder combustion comes from secondary air volume, and the air-coal ratio can be changed by adjusting the coal injection amount or the secondary air volume.
2. A method for reducing NOx in rotary kiln exhaust gas according to claim 1, wherein: the coal injection amount is adjusted to improve the coal injection amount per hour and increase the lime heat consumption.
3. A method for reducing NOx in rotary kiln exhaust gas according to claim 1, wherein: and adjusting the secondary air quantity to reduce the secondary air quantity of the rotary kiln.
4. A method for reducing NOx in rotary kiln exhaust gas according to claim 1, wherein: the secondary air quantity is 6 times of coal injection quantity.
5. A method for reducing NOx in rotary kiln exhaust gas according to claim 2, wherein: the lime heat consumption control standard is 1050-1150 Kcal/Kg.
CN201911338995.1A 2019-12-23 2019-12-23 Reduce rotary kiln waste gas NOxMethod (2) Pending CN111141149A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112665404A (en) * 2020-12-18 2021-04-16 包头钢铁（集团）有限责任公司 Method for reducing emission of nitric oxide in rotary kiln waste gas

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102425807A (en) * 2011-11-23 2012-04-25 华北电力大学（保定） Combustion feedforward and feedback composite optimization controlling method for pulverized coal fired boiler
CN104634097A (en) * 2014-12-26 2015-05-20 中国建筑材料科学研究总院 Method and system for reducing nitrogen oxide in rotary kiln

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102425807A (en) * 2011-11-23 2012-04-25 华北电力大学（保定） Combustion feedforward and feedback composite optimization controlling method for pulverized coal fired boiler
CN104634097A (en) * 2014-12-26 2015-05-20 中国建筑材料科学研究总院 Method and system for reducing nitrogen oxide in rotary kiln

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
范潇: "1.1.2 目前水泥工业中常用的NOx 减排技术", 《水泥工业富氧燃烧技术对烟气中NOX排放影响的试验研究》 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112665404A (en) * 2020-12-18 2021-04-16 包头钢铁（集团）有限责任公司 Method for reducing emission of nitric oxide in rotary kiln waste gas

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