CN112361834B - Method for improving concentration of carbon dioxide in flue gas - Google Patents

Method for improving concentration of carbon dioxide in flue gas Download PDF

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CN112361834B
CN112361834B CN202011242328.6A CN202011242328A CN112361834B CN 112361834 B CN112361834 B CN 112361834B CN 202011242328 A CN202011242328 A CN 202011242328A CN 112361834 B CN112361834 B CN 112361834B
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flue gas
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kiln
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CN112361834A (en
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卞正培
李维祥
付太陆
毛忠仁
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Jiangsu Yuli Energy Saving Technology Co ltd
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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
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2/00—Lime, magnesia or dolomite
    • C04B2/10—Preheating, burning calcining or cooling
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2/00—Lime, magnesia or dolomite
    • C04B2/10—Preheating, burning calcining or cooling
    • C04B2/108—Treatment or selection of the fuel therefor
    • 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
    • F23L7/00—Supplying non-combustible liquids or gases, other than air, to the fire, e.g. oxygen, steam
    • 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
    • F27D19/00—Arrangements of controlling devices

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  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
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  • General Engineering & Computer Science (AREA)
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  • Physics & Mathematics (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Combustion & Propulsion (AREA)
  • Environmental & Geological Engineering (AREA)
  • Treating Waste Gases (AREA)
  • Furnace Details (AREA)

Abstract

The invention discloses a method for improving the concentration of carbon dioxide in flue gas, which comprises the following steps: calculating the total amount of the flue gas and CO in the total amount of the flue gas 2 The content of the components; calculating the air flow needed to reduce the input air flow into the kiln and the pure oxygen quantity used for replacement; calculating the amount of flue gas to be doped; according to the amount of the flue gas to be doped, simultaneously inputting a part of circulating flue gas of the lime kiln flue gas and substituted pure oxygen into the kiln through an air input port which meets the requirements of a calcination process; and the rest of the flue gas is sent to the next recovery process. The method for improving the concentration of the carbon dioxide in the flue gas utilizes the pure oxygen and the flue gas to replace part of combustion air, the proportion of the pure oxygen and the flue gas is adjustable, the influence on combustion temperature caused by fuel calorific value deviation can be compensated in a large range by a method of increasing and decreasing the amount of the returned flue gas, the thermal efficiency of the kiln cannot be lost, and the proportion of various substances in the flue gas of the lime kiln cannot be influenced by increasing and decreasing the amount of the returned flue gas.

Description

Method for improving concentration of carbon dioxide in flue gas
Technical Field
The invention relates to a lime kiln flue gas treatment technology, in particular to a method for improving the concentration of carbon dioxide in flue gas.
Background
Limestone (main component is CaCO) 3 ) A large amount of CO is released in the calcination process 2 Approximately 400Nm3 of CO per 1 ton of lime produced 2 A gas. Plus CO produced by combustion of fuel 2 CO released to the atmosphere during lime production 2 The amount of (a) is quite considerable. On the other hand, CO 2 Has important application in many fields such as industrial and agricultural production and the like. But the problem is that CO in the flue gas of most lime kilns at present 2 The concentration is only 25% -45%. The difference depends mainly on the kind of fuel used and the operating principle of the kiln. Because of CO 2 The concentration is too low, so the utilization value is not high. In the environmental protection field, low CO is treated by a carbon sequestration process 2 Flue gas of a concentration also comes at a costly economic price.
Disclosure of Invention
The invention aims to provide a method for improving the concentration of CO2 in lime kiln flue gas, so as to reduce the difficulty and cost of subsequent purification and utilization, or can be directly used by a subsequent process, improve the combustion quality and reduce the generation of pollutants.
In order to achieve the purpose, the invention provides a method for increasing the concentration of carbon dioxide in flue gas, which comprises the following steps:
step 1, according to CaCO 3 Calculating CO under design yield by decomposition chemical equation 2 The amount of the generated products in unit time is calculated according to the input amount of air and fuel in unit time required by the calcination process requirement and the chemical equation of combustion of each combustible component in the fuel, and then CaCO is added 3 CO decomposed in calcination 2 Adding the combustion products to calculate the total smoke and CO in the total smoke 2 The content of the components;
step 2, according to the total amount of the smoke and CO in the total amount of the smoke 2 Component content and target CO 2 Concentration calculation for reducing N input into kiln 2 Calculating the air flow required to reduce the input air flow into the kiln and the pure oxygen quantity for replacement;
step 3, calculating the amount of flue gas to be doped according to the amount of pure oxygen for substitution and a set combustion temperature;
step 4, simultaneously inputting a part of circulating flue gas of the lime kiln flue gas and substituted pure oxygen into the kiln through an air input port which meets the requirement of the calcination process according to the amount of the flue gas to be doped;
and 5, conveying the rest flue gas to the next recycling procedure except the recycled flue gas returned to the kiln.
Further, in step 4, the circulating flue gas and the substituted pure oxygen enter the upper combustion chamber from an upper combustion chamber combustion air input port of the annular sleeve kiln and enter the lower combustion chamber from a driving air input port.
Further, the pure oxygen amount and the circulating flue gas amount entering the upper combustion chamber are calculated, the input pure oxygen amount is determined according to the ratio of the oxygen flow to the fuel flow, and the input circulating flue gas amount is determined according to the temperature value requirement of the combustion chamber.
Furthermore, the pure oxygen amount and the circulating flue gas amount entering the lower combustion chamber are independently controlled, the input pure oxygen amount is controlled according to the proportional value of the oxygen flow and the fuel flow, and the input circulating flue gas amount is adjusted according to the injection amount of the injector.
Further, in step 4, a part of the circulating flue gas of the lime kiln is purified and dehydrated before being input into the kiln.
Compared with the prior art, the invention has the beneficial effects that: (1) CO in lime kiln flue gas can be greatly improved through cyclic utilization of flue gas 2 Concentration of CO 2 The recycling of (2) provides a high-quality gas source; (2) Because of the combustion zone N 2 The concentration is reduced, and NO can be effectively reduced x Generating; (3) Lime calcination requires that the combustion temperature be controlled within a reasonable range when air is used as the combustion promoter, because of O 2 The proportion in the air is fixed, when the fuel heat value deviates from the design, the balance and compromise between the combustion quality and the combustion temperature are needed, even the combustion temperature can not be controlled in a reasonable range, so that the quality of lime products and the heat efficiency of the kiln are lost, therefore, pure oxygen and flue gas are used for replacing part of combustion air, the proportion of the pure oxygen and the flue gas is adjustable, the influence of the fuel heat value deviating from the combustion temperature can be compensated in a large range by increasing and decreasing the amount of the backflow flue gas, the heat efficiency of the kiln can not be lost, and the proportion of various substances in the flue gas of the lime kiln can hardly be influenced by increasing and decreasing the amount of the backflow flue gas.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
Detailed Description
The technical solution of the present invention is described in detail below with reference to the accompanying drawings, but the scope of the present invention is not limited to the embodiments.
Because the flue gas component of the lime kiln is mainly CO 2 And N 2 Corresponding to a certain lime production no matter CaCO 3 CO released by decomposition 2 Or CO formed by combustion of fuel 2 Cannot be significantly increased, and therefore the technique adopted in the present inventionThe scheme is that proper amount of pure oxygen is used to replace partial combustion air to reduce N in kiln 2 To increase CO in the flue gas 2 The ratio of (a) to (b). In order to overcome the combustion temperature rise brought by pure oxygen combustion supporting, a proper amount of flue gas is introduced according to the expected combustion temperature to dilute the pure oxygen.
Example 1:
as shown in fig. 1, the invention provides a method for increasing the concentration of carbon dioxide in flue gas, which comprises the following steps:
step 1, according to CaCO 3 Calculating CO under design yield by decomposition chemical equation 2 The amount of the generated products in unit time is calculated according to the input amount of air and fuel in unit time required by the calcination process requirement and the chemical equation of combustion of each combustible component in the fuel, and then CaCO is added 3 CO decomposed in calcination 2 Adding the combustion products to calculate the total smoke and CO in the total smoke 2 The content of the components;
step 2, according to the total amount of the smoke and CO in the total amount of the smoke 2 Component content and target CO 2 Concentration calculation for N required to reduce input into kiln 2 Calculating the air flow required to reduce the input air flow into the kiln and the pure oxygen quantity for substitution;
step 3, calculating the amount of flue gas to be doped according to the amount of pure oxygen for substitution and a set combustion temperature;
step 4, simultaneously inputting a part of circulating flue gas of the lime kiln flue gas and the substituted pure oxygen into the kiln through an air input port which meets the requirement of the calcination process according to the amount of the flue gas to be doped;
and 5, sending the rest flue gas to the next recycling process except the recycled flue gas returned to the kiln.
Further, in step 4, the circulating flue gas and the substituted pure oxygen enter the upper combustion chamber from an upper combustion chamber combustion air input port of the annular sleeve kiln and enter the lower combustion chamber from a driving air input port. The pure oxygen and the flue gas are connected to the primary air and the driving air inlet of the upper combustion chamber, so that the requirement of temperature adjustment of the upper combustion chamber is met conveniently, and the frequent change of the driving air volume is considered, so that the components of the flue gas cannot be influenced when the flue gas is used as the driving air and the air volume is changed.
Further, the pure oxygen amount and the circulating flue gas amount entering the upper combustion chamber are calculated, the input pure oxygen amount is determined according to the ratio of the oxygen flow to the fuel flow, and the input circulating flue gas amount is determined according to the temperature value requirement of the combustion chamber.
Furthermore, the pure oxygen amount and the circulating flue gas amount entering the lower combustion chamber are independently controlled, the input pure oxygen amount is controlled according to the proportional value of the oxygen flow and the fuel flow, and the input circulating flue gas amount is adjusted according to the injection amount of the injector.
Further, in step 4, a part of the circulating flue gas of the lime kiln is purified and dehydrated before being input into the kiln.
The calculation in the steps is carried out according to a conventional calculation method in the thermal engineering field.
The lime kiln aimed at in this example uses natural gas fuel to calcine lime, the output requirement is 500TPD, and the main components of the raw material calcined lime are shown in table 1:
TABLE 1
Categories CaCO 3 MgO Acid insoluble substance SiO 2 P
Is in percentage by weight 98.1 0.3 0.9 0.2 0.002
The average value of the heat value of the adopted natural gas is 8500kCal/Nm 3 (ii) a The compositional results are shown in table 2:
TABLE 2
Composition of matter CH 4 C 2 H 6 +C 3 H 8 +C 4 H 10 CO 2 H 2 S N 2 Moisture content Others
Content (v%) 97.8 0.7 1.3 0 0.1 0.1 0
The components of the flue gas before the lime kiln is modified are shown in table 4:
TABLE 4
Composition of flue gas CO 2 O 2 CO
Is in percentage by weight 25 4.5 0.3
The present example is fully based on the original operating parameters and is only intended to illustrate the method and steps for increasing the CO2 concentration. The analysis and calculation of various parameters before the lime kiln is reformed are as follows:
(1) Fuel consumption estimation
Analyzing according to the actual production condition: the lime heat consumption is 950kCal/kg lime, and the heat value of natural gas is 8497kCal/Nm 3 Then the unit consumption of natural gas is 111.8Nm 3 T lime; the total consumption of natural gas per hour is about 2329.2Nm 3 H; the fuel in the upper and lower combustion chambers is distributed according to 3:7 in the current production, and the fuel quantity in the upper combustion chamber is 0.3 × 2329.2 ≈ 699Nm 3 H; lower combustion chamberThe fuel quantity is 0.7 × 2329.2 ≈ 1630Nm 3 H; complete combustion 1Nm 3 The amount of oxygen theoretically required for natural gas is about 1.98Nm 3 The required amount of air is about 9.4Nm 3 The amount of smoke generated is about 10.4Nm 3 (ii) a The total air required for complete combustion of the fuel is: 2329.2 × 9.4 ≈ 21895Nm 3 H; the total flue gas amount required for complete combustion of the fuel is: 2329.2 × 10.4 ≈ 24224Nm 3 /h。
(2) Lower combustion chamber combustion air analysis
The theoretical air quantity required for the lower combustion chamber is: 1630 × 9.4=15322nm 3 /h；
The combustion air of the lower combustion chamber is as follows: primary air, combustion air and lime cooling air;
a. the primary air is blown to the air duct,
primary air coefficient: assuming complete combustion of 1Nm 3 The air quantity needed by the fuel gas is K, the primary air actually input into the burner is lambda x K, and lambda is called a primary air coefficient; a lower burner: λ sb =0.2-0.3; the primary air volume is about: 0.2 x 15322=3064nm 3 H; wherein the oxygen amount is: 643Nm 3 /h。
b. Combustion-supporting air
The air quantity of the combustion air of the 500TPD sleeve kiln is about 7500Nm 3 The oxygen content is as follows: 7500 × 0.21=1575nm 3 /h；
c. Lime cooling air (with kiln bottom air leakage)
The lime cooling air (+ kiln bottom air leakage) of 500t kiln can be 10500Nm 3 Calculating the time/h;
then, the total combustion air amount of the lower combustion chamber is: 3064+7500+10500=21064Nm 3 /h。
(3) Upper combustion chamber combustion air analysis
The combustion-supporting air of the upper combustion chamber is as follows: primary air
The theoretical air quantity required by the upper combustion chamber is as follows: 699 × 9.4=6570Nm 3 H; the corresponding oxygen amounts were about: 1380Nm 3 H; and (4) upper burner: λ su =0.5-0.55; namely, the combustion air of the upper combustion chamber is about: 6570 × 0.5=3285Nm 3 /h；
About 50% of the fuel in the upper chamber is combusted in the combustion chamber and the remaining 50% is combusted in the bed encountering excess air from the lower chamber.
The excess air amount entering the material layer from the lower combustion chamber is as follows: 21064-15322=5742Nm 3 And h, far exceeding the requirement that the fuel in the upper combustion chamber is fully combusted by 50 percent, namely the fuel in the upper combustion chamber can be fully combusted.
The kiln tail flue gas contains kiln top air leakage and cold air mixed with the flue gas before entering a dust remover.
The 500TPD muffle operates at rated capacity and has a drive air flow of about 7500Nm to provide sufficient power for cycle gas formation 3 The oxygen content is as follows: 7500 × 0.21=1575nm 3 /h。
The air volume of combustion air is about 7500Nm 3 The oxygen content is 1575Nm 3 H; i.e. 7500Nm 3 1575Nm combustion air/h 3 Pure oxygen +5925 Nm/h 3 And/h, mixing and replacing kiln tail flue gas. Pure oxygen participates in combustion, and the flue gas tends to be recycled, so that the flue gas can be regarded as internal circulation, and the whole flue gas is not counted finally.
The theoretical air quantity required by the upper combustion chamber is as follows: 699 × 9.4=6570Nm 3 H; the corresponding oxygen amounts are: 1380Nm 3 H; and (4) upper burner: λ su =0.5-0.55; namely, the combustion air of the upper combustion chamber is about: 6570 × 0.5=3285Nm 3 /h。
Combustion air for upper combustion chamber: 3285Nm 3 H, wherein the amount of oxygen is about: 690Nm 3 H; i.e. 3285Nm 3 690 Nm/h combustion air 3 Oxygen +2595Nm 3 And/h, mixing and replacing the flue gas.
When lifting and transforming the lime kiln, the method comprises the steps of lifting and transforming the lower combustion chamber and lifting and transforming the upper combustion chamber.
Lifting and reforming the lower combustion chamber: cooling the flue gas by using an air cooler, reducing the temperature of the flue gas to be below 80 ℃, and reducing the temperature of water vapor in the flue gas, condensing and discharging the water vapor; a part of the smoke after cooling and dewing is conveyed to a combustion air pipeline of the lower combustion chamber by the additionally arranged smoke fan and the smoke pipeline, and is preheated by the heat exchanger and then enters the spray gun, so that the injection effect is met.
Lifting and reforming the upper combustion chamber: a flue gas ring pipe and a flue gas fan are additionally arranged between the flue gas pipeline and the upper combustion chamber; and a part of the cooled and dewed flue gas is conveyed to the upper combustion chamber by utilizing the additionally arranged flue gas circular pipe and the flue gas fan. Oxygen and natural gas are combusted, a large amount of flue gas can absorb partial heat and enter the kiln to preheat limestone; meanwhile, a large amount of smoke can reduce local high temperature and protect the refractory material of the upper combustion chamber; and the water is conveyed to a plant water treatment system for treatment through a pipeline.
After the transformation is completed, the concentration verification is also carried out on the result of the replacement calculation, and the concentration verification comprises the following steps:
(1) And (3) carrying out combustion verification on the lower combustion chamber:
analyzing the composition of combustion air of the lower combustion chamber, and obtaining the air quantity of each composition, wherein the combustion air of the lower combustion chamber is as follows: primary air, driving air, lime cooling air and kiln bottom air leakage; primary air: 3064Nm 3 H air, wherein the oxygen amount is: 643Nm 3 H; driving wind: 1575Nm 3 Pure oxygen +5925 Nm/h 3 H, smoke gas; cooling air by lime: 10500Nm 3 H air, wherein the oxygen amount: 2205Nm 3 H; natural gas: 1630Nm 3 /h；
The total amount of oxygen-free components in the air: 3064-643+10500-2205= 1071696m 3 /h。
Calculating the combustion reaction of pure oxygen in the combustion air of the lower combustion chamber and natural gas to obtain the oxygen consumption, the generated flue gas quantity, the generated carbon dioxide quantity and the generated water vapor quantity after combustion;
natural gas 1630Nm 3 Reaction with oxygen, consuming about 3227Nm 3 Oxygen,/h, formation: 1630Nm 3 Carbon dioxide and 3213Nm 3 H water vapor.
The amount of residual oxygen: 643 calcium 1575, 2205-3227=1196Nm 3 H oxygen.
(2) And (3) carrying out combustion verification on the upper combustion chamber:
analyzing the composition of combustion air of the upper combustion chamber, and acquiring the air quantity of each composition; the combustion-supporting air of the upper combustion chamber is as follows: primary air and secondary air; primary air: 690Nm 3 Oxygen/hGas +2595Nm 3 H, smoke gas; secondary air flow: 1196Nm 3 H air; natural gas: 699Nm 3 /h；
Calculating the combustion reaction of pure oxygen in the combustion air of the upper combustion chamber and natural gas to obtain the oxygen consumption, the generated flue gas quantity, the generated carbon dioxide quantity and the generated steam quantity after pure oxygen combustion;
699Nm Natural gas 3 Reaction with oxygen, consuming about 1384Nm 3 Oxygen,/h, formation: 699Nm 3 Carbon dioxide and 1378Nm 3 H water vapor.
The amount of residual oxygen: 690+1196-1384=502Nm 3 /h。
The oxygen amount in the kiln accords with the calcining environment of the excess air coefficient of the sleeve kiln, and the calcining effect can be met.
Calculating the total amount of carbon dioxide in the flue gas:
the amount of each carbon dioxide generated by the lower combustion chamber and the upper combustion chamber after the air combustion and the pure oxygen combustion reaction is 1630Nm 3 /h、699Nm 3 /h；
Carbon dioxide generated by limestone decomposition:
100/56*500*1000/24*0.44/1.964*0.97＝8085Nm 3 /h。
and accumulating the generated carbon dioxide quantities to calculate the total carbon dioxide quantity as follows:
8085+1630+699＝10414Nm 3 /h；
calculating the total amount of water vapor in the flue gas:
the steam amount of each steam generated by the lower combustion chamber and the upper combustion chamber after the air combustion and the pure oxygen combustion reaction is 3213Nm respectively 3 /h、1378Nm 3 H; and accumulating the generated steam quantities to calculate the total steam quantity as follows:
3213+1378＝4591Nm 3 /h；
calculating the total amount of the smoke:
obtaining the amount of each smoke generated by the lower combustion chamber and the upper combustion chamber after air combustion and pure oxygen combustion reaction; the total amount of the flue gas is calculated by accumulating the generated flue gas amountsIs 27223Nm 3 H; the total smoke composition after fuel combustion is shown in table 7:
TABLE 7
Figure BDA0002768838380000061
Figure BDA0002768838380000071
Calculating the proportion of carbon dioxide in the flue gas:
without subtracting water vapor: 10414/27223 by 100% =38.25%;
subtracting water vapor: subtracting the total amount of the water vapor from the total amount of the smoke to obtain the total amount of the smoke after the water vapor is cooled and condensed, and checking and reading data, wherein the saturated smoke water content is about 30g/Nm at 30 DEG C 3 It can be seen that when the temperature of the flue gas is reduced to 30 ℃, the water vapor content in the total flue gas is about 817kg/h, and about 3130Nm can be calculated 3 And/h condensation, the total smoke gas amount can be reduced to: 27223-3130=24093Nm 3 /h；
The proportion of carbon dioxide in the dry flue gas is as follows: 10414/24093 ≈ 100% 43.2%. Namely, after being reformed, the concentration of the carbon dioxide in the flue gas can be adjusted between 38.25 and 43.2 percent.
As noted above, while the present invention has been shown and described with reference to certain preferred embodiments, it is not to be construed as limited thereto. Various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (5)

1. A method for improving the concentration of carbon dioxide in discharged flue gas of a lime kiln is characterized by comprising the following steps:
step 1, according to CaCO 3 Calculating CO under design yield by decomposition chemical equation 2 The amount of the formed product per unit time, the input amounts of air and fuel per unit time required by the calcination process, and the combustion of each combustible component in the fuelCalculating the amount and components of the combustion product per unit time by using a mathematical equation, and adding CaCO 3 CO decomposed in calcination 2 Adding the combustion products to calculate the total smoke and CO in the total smoke 2 The content of the components;
step 2, according to the total amount of the smoke and CO in the total amount of the smoke 2 Component content and target CO 2 Concentration calculation for reducing N input into kiln 2 Calculating the air flow required to reduce the input air flow into the kiln and the pure oxygen quantity for replacement;
step 3, calculating the amount of flue gas to be doped according to the amount of pure oxygen for substitution and a set combustion temperature;
step 4, simultaneously inputting a part of circulating flue gas of the lime kiln flue gas and the substituted pure oxygen into the kiln through an air input port which meets the requirement of the calcination process according to the amount of the flue gas to be doped;
and 5, conveying the rest flue gas to the next recycling procedure except the recycled flue gas returned to the kiln.
2. The method for increasing the concentration of carbon dioxide in lime kiln exhaust flue gas according to claim 1, wherein in step 4, the circulating flue gas and the substitute pure oxygen are introduced into the upper combustion chamber from the combustion air inlet of the upper combustion chamber of the annular sleeve kiln and are introduced into the lower combustion chamber from the driving air inlet.
3. The method for improving the concentration of carbon dioxide in the lime kiln exhaust flue gas according to claim 2, wherein the amount of pure oxygen and the amount of circulating flue gas entering the upper combustion chamber are calculated, the amount of pure oxygen to be input is determined according to the ratio of the oxygen flow to the fuel flow, and the amount of circulating flue gas to be input is determined according to the requirement of the temperature value of the combustion chamber.
4. The method for increasing the concentration of carbon dioxide in lime kiln exhaust flue gas according to claim 2, wherein the amount of pure oxygen entering the lower combustion chamber and the amount of circulating flue gas are independently controlled, the amount of pure oxygen input is controlled according to the ratio of the oxygen flow to the fuel flow, and the amount of circulating flue gas input is adjusted according to the injection amount of the injector.
5. The method for increasing the concentration of carbon dioxide in the discharged flue gas of the lime kiln according to claim 1, wherein in the step 4, a part of the circulating flue gas of the lime kiln is purified and dehydrated before being input into the kiln.
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