CN115216625B

CN115216625B - Method for assisting sintering by gas periodic interval injection

Info

Publication number: CN115216625B
Application number: CN202111390081.7A
Authority: CN
Inventors: 周浩宇; 叶恒棣; 魏进超; 王业峰; 陈思墨; 李谦; 刘前
Original assignee: Zhongye Changtian International Engineering Co Ltd
Current assignee: Zhongye Changtian International Engineering Co Ltd
Priority date: 2021-11-22
Filing date: 2021-11-22
Publication date: 2023-06-23
Anticipated expiration: 2041-11-22
Also published as: CN115216625A

Abstract

A method for assisting sintering by gas periodic interval injection is characterized by comprising the following steps: periodically injecting fuel gas at intervals to the material surface of the sintering mixture, and enabling the fuel gas to enter a sintering material layer for burning and heating; in the gas injection process, the temperature of the sinter zone and the combustion zone area in the sinter bed is controlled by adjusting the gas injection duration in a single period. According to the invention, the injection and stop of the fuel gas are skillfully controlled through the periodic interval injection, so that the fuel gas is repeatedly ignited and extinguished near the combustion zone, namely, a certain cooling time is reserved for the sintered finished ore in a specific area while the heat is supplemented to the material layer through the fuel gas, so that the temperature of the combustion zone and the position of the sintered ore zone can be controlled without overhigh condition.

Description

Method for assisting sintering by gas periodic interval injection

Technical Field

The invention relates to a gas injection auxiliary sintering process, in particular to a gas periodic interval injection auxiliary sintering method, and belongs to the technical field of sintering.

Background

Due to CO ₂ The greenhouse effect caused by the gases such as glacier melting, sea level rising, natural ecological degradation and natural disaster frequency directly threatens the life of part of regional human beings, and carbon reduction is arranged as strategic development focus in all countries of the world in view of the fact that the problems such as the greenhouse effect are increasingly prominent at present. With the annual increase of the steel output of China, the total carbon emission of the steel industry of China is in an annual rising trend, the annual carbon emission is over ten thousand t, and the CO of the steel industry is improved ₂ Emission reduction tasks face tremendous stress.

As a key link in iron and steel industry iron making process, the sintering process mainly comprises the steps of mixing various powdery iron-containing raw materials with proper amount of fuel and flux, adding proper amount of water, mixing and pelletizing, making the materials undergo a series of physical and chemical changes on sintering equipment, sintering into blocks, and conveying the blocks to a blast furnace for the next process.

According to the related data, the carbon dioxide emission of the sintering and blast furnace process accounts for about 60% of the total industrial emission. In order to reduce carbon emission and subsequent blast furnace smelting costs during the sintering process, the requirements of the blast furnace on the sintered ore tend to be high strength and high reducibility. In the sintering process, sintered ore is generally required to have high strength, high yield, low return rate, and low fuel consumption. The high-strength and high-reducibility sintered ore consumes less coke in the blast furnace smelting process, thereby reducing the emission of carbon dioxide.

After the pulverized coal of the upper material layer is ignited in the sintering process, the combustion heat release is not only used for sintering nearby raw materials, but also used for exhaust type operation production, and the self-heat-storage effect enables the upper heat to be brought into the lower material layer by gas to participate in the sintering of the lower material layer, so that the heat required by the material layer from top to bottom is gradually reduced. When the material is distributed, segregation material is adopted, the upper material layer is provided with more pulverized coal, and the lower material layer is provided with less pulverized coal. The quality index of the finished product can be greatly improved under the same fuel consumption index, or the fuel consumption index can be greatly reduced under the same quality index of the finished product, so that the purposes of saving energy and reducing carbon emission are achieved.

However, due to the limitations of device technology, in the practical industrial production of sintering plants, the strictly ideal layered segregation type fuel distribution is difficult to achieve, and owners have to distribute solid fuel according to the high values of the theoretically required fuel amount in each layer. Meanwhile, as some large-particle coke powder can fall to the bottom of the material layer when the sintering machine head is used for distributing, the opposite situations of high solid fuel quantity at the lower part and low solid fuel quantity at the middle and upper parts can be caused. Therefore, the problems of insufficient heat of the upper material layer and excessive heat of the middle and lower material layers in the sintering material layers during sintering production can be caused, the conditions of excessive melting of the lower sintering material and the like can be easily caused, and finally, the waste of energy and resources is caused, and the generation of smoke pollutants is greatly aggravated.

Under the large environment, the technology of 'sintering material surface gas fuel injection' developed by JFE company in Japan is developed, natural gas fuel diluted below the lower limit of the combustible concentration is injected above the sintering material surface at a certain distance behind an ignition furnace, so that the natural gas fuel is burnt in a sintering material layer to supply heat, and the solid carbon consumption and CO in the production of the sintering ore are reduced ₂ Discharge amount. Meanwhile, the burning of the gas fuel widens the width of a high-temperature zone of the sinter layer during production, so that the temperature time of the sinter at 1200-1400 ℃ is prolonged, and the strength and the 5-10 mm porosity of the sinter are effectively enhanced.

In the initial sintering process, the distribution of the material layers in the sintering process is shown in fig. 3, and the material layers on the trolley are mainly a sinter belt, a combustion belt, a drying preheating belt, an overwetting belt and an original material belt from top to bottom in sequence, and the approximate temperature distribution is shown in a curve corresponding to "no blowing" in fig. 4. The burning zone is high in temperature due to ignition of the coke powder in the sintering material layer, and physical and chemical processes such as melting and sintering of minerals are realized at 1200-1400 ℃ to form finished sintered ore (the burning zone is evolved into a sintered ore zone), and the burning of the coke powder is completed. And because of the influence of the exhaust, fresh air can be continuously supplemented at the top of the material layer to cool the material layer, so that the temperature of the sinter belt is low at a position close to the top of the material layer and high at a position close to the combustion belt.

After the gas injection technology is adopted, the burning of the gas fuel widens the width of a high-temperature zone of the sinter bed during productionThe cooling speed of the fresh air to the sintered finished ore is slowed down, so that the temperature of the position, close to the combustion zone, in the sintering ore zone is higher than that of the position, not adopting blowing, and the effect is shown by a curve corresponding to 'adopting blowing' in fig. 4. Laboratory researches and sintering process engineering practices show that in a certain range, the larger the injection quantity and the larger the injection concentration of the fuel gas, the more heat is released after the fuel gas is sucked into a material layer, the larger the quantity of the substitute solid fuel is, so that the lower coke consumption and CO consumption are realized ₂ And (5) discharging. In general, the higher the concentration of the combustible gas in the mixed gas, the lower the ignition temperature, so it can be found from the temperature distribution in the material layer that, after the injection amount of the combustible gas is increased and the injection concentration is increased, the ignition position of the combustible gas in the material layer moves from the position of the combustion zone near the sinter zone to the direction of the sinter zone, and the temperature curve in the material layer is shown as a dotted line in fig. 5, and the temperature in the material layer is higher at the position of the sinter zone near the combustion zone. The red layer is used for describing the region of the sintering material layer, the temperature of which is above 1000 ℃, and obviously, after the gas injection quantity is increased, the thickness of the red layer in the material layer is obviously increased, and due to the fact that the temperature in the red layer is high and liquid phase is generated, the too thick red layer can cause poor air permeability of the material layer, the sintering exhaust negative pressure is too large, the air quantity and the sintering process of the material layer are influenced, and the yield and the quality of the sintering ore are reduced.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a method for assisting sintering by gas periodic interval blowing. The invention aims to solve the technical problems of poor material layer air permeability, rising sintering induced draft negative pressure and the like after improving the gas injection quantity in the gas injection auxiliary sintering process, and realizes the maximum gas injection quantity under the condition of maintaining the material layer air permeability and the induced draft negative pressure normal, thereby remarkably improving the solid fuel substitution quantity and reducing CO ₂ And (5) discharging.

The invention provides a method for changing the original continuous injection of fuel gas in the fuel gas injection process, which adopts the periodic interval injection measure to periodically inject the fuel gas into the material layer of the sintering mixture. According to the invention, the injection and stop of the fuel gas are skillfully controlled through the periodic interval injection, so that the fuel gas is repeatedly ignited and extinguished near the combustion zone, namely, a certain cooling time is reserved for the sintered finished ore in a specific area while the heat is supplemented to the material layer through the fuel gas, so that the temperature of the combustion zone and the position of the sintered ore zone can be controlled without overhigh condition. Therefore, the invention can improve the temperature change curve of the sinter belt and the area near the combustion belt on the premise of maintaining the original fuel gas supplementing amount, weaken the thickness of a red layer and ensure proper material layer air permeability and normal exhaust negative pressure.

According to an embodiment of the invention, a method for assisting sintering by gas periodic interval injection is provided.

A method for assisting sintering by periodically and alternately spraying fuel gas to the material surface of a sintering mixture comprises the steps of periodically and alternately spraying fuel gas, and enabling the fuel gas to enter a sintering material layer for burning and heating. In the gas injection process, the temperature of the sinter zone and the combustion zone area in the sinter bed is controlled by adjusting the gas injection duration in a single period.

Along the thickness direction of the sinter bed, the sinter bed on the sintering trolley mainly comprises a sinter belt, a combustion belt, a drying preheating belt, an overwetting belt and an original material belt from top to bottom.

In the invention, the control of the temperature of the sinter belt and the combustion belt area in the sinter bed is realized, and the method specifically comprises the following steps:

1) And determining the cycle number of the gas injection, the duration of the initial gas injection in a single cycle and the duration of the initial gas stopping injection in a single cycle.

2) And calculating the injection quantity of the fuel gas in unit time according to the total quantity of the fuel gas required to be injected by the sintering mixture in the sintering trolley.

3) And calculating the heat emitted by the combustion of the injected fuel gas in the sinter bed in the fuel gas injection time of a single period.

4) And calculating the cooling quantity of the air to the sinter bed in the gas blowout time of a single period.

5) And judging the temperature change condition of the sinter bed in a single period according to the heat released by the combustion of the injected fuel gas and the cooling quantity of air to the sinter bed, so as to realize the control of the temperatures of the sinter zone and the combustion zone region in the sinter bed.

In the present invention, step 1) comprises the sub-steps of:

1a) According to the length L of the gas injection section on the sintering machine and the running speed v of the sintering trolley, calculating the running time t of the sintering trolley in the gas injection section, namely, the total duration t of gas injection to the sintering mixture in the sintering trolley is as follows:

It should be noted that, the total duration of gas injection to the sintering mixture in the sintering pallet described herein includes the injection duration and the stop duration in each cycle.

1b) Setting the cycle number of the gas injection to the sintering mixture in the sintering trolley as N and the duration of the initial gas injection in a single cycle as deltat ₁ Thus, the duration Δt of the initial stop of the gas injection in a single cycle ₂ The method comprises the following steps:

in the present invention, in step 2), the total amount of gas required to be blown by the sintering mixture in the sintering pallet is:

wherein: g is the total amount of gas required to be blown by the sintering mixture in the sintering trolley. And m is the mass of the sintered mixture in the area corresponding to the gas injection section. Q (Q) _{Tonifying device} The heat is needed to be supplemented for the sintered mixture of unit mass after the solid fuel ratio is reduced as a whole. Wherein Q is _{Tonifying device} Is determined by the type of sintering raw materials, the average particle size of the sintering mixture, the solid fuel ratio and the like. H is the heat value of the fuel gas.

Preferably, in step 2), the calculating the injection amount of the fuel gas in the unit time specifically includes:

wherein: s is the injection quantity of fuel gas in unit time.

In the present invention, in step 3), the heat released by the combustion of the injected fuel gas in the sinter bed is calculated within the fuel gas injection time of a single cycle, specifically:

Wherein: q (Q) _in Is delta t ₁ The heat released by the combustion of the injected fuel gas in time.

In the present invention, in step 4), the cooling amount of air to the sinter bed is calculated in the fuel gas off-time of a single cycle, specifically: stop time Δt for a single cycle ₂ In the sintering material layer, the cooling rate of the sintering material layer cooled by air is q _co The method comprises the following steps:

q _co ＝h _co ·(T _{combustion process} -T _∞ )·ξ·m·A............(6)。

Wherein: q (Q) _co Is delta t ₂ And cooling the sinter bed by air in time. h is a _co To sinter the material layer cooling coefficient, h is empirically determined _co The value range of (2) is 50-60W/(m) ² ·℃)。T _{Combustion process} The combustion temperature of the gas in the sintering bed is generally selected empirically in the range of 1000-1200 ℃. T (T) _∞ The air temperature is, for example, 30 ℃, 25 ℃, 20 ℃ or the like. And m is the mass of the sintered mixture in the area corresponding to the gas injection section. A is the specific surface area of the combustion zone in the sintered material layer. Xi is the height direction of the burning zoneThe value of xi is 0-1, preferably 0.01-0.1, which is the proportion of the whole sintering material layer height.

In the present invention, step 5) comprises the sub-steps of:

5a) According to the heat balance principle, calculating the temperature change value delta T of the sintering material layer at the corresponding position in a single period:

c _p ·ξ·m·ΔT＝Q _in -Q _co ............(8)。

namely there is

Wherein: c _p Is the average specific heat capacity of the sinter bed.

5b) Calculating the actual final temperature T of the sinter bed at the corresponding position in a single period _co ：

T _co ＝T _{Combustion process} +ΔT………(10)。

5c) Comparing the actual final temperature T of the sinter bed in a single cycle _co And target temperature T _aim And further adjusting the duration of gas injection in a single period, thereby realizing the control of the temperature of the sinter belt and the combustion belt area in the sinter layer.

Preferably, the substep 5 c) is specifically:

if the actual final temperature T of the sinter bed in a single cycle _co Target temperature T _aim And the temperature of the sintering ore belt and the combustion belt is controlled in a normal range in the period, and the system keeps the current blowing parameters to continue to operate.

If the actual final temperature T of the sinter bed in a single cycle _co Target temperature T _aim At the moment, the duration of gas injection in a single period is shortened, so that T is formed _co ＝T _aim 。

If the actual final temperature T of the sinter bed in a single cycle _co < target temperature T _aim At the moment, the duration of gas injection in a single period is prolonged, so that T is formed _co ＝T _aim 。

Preferably, in substep 5 c), the target temperatureDegree T _aim The value of (C) is 600-1000 ℃, preferably 700-850 ℃, more preferably 740-780 ℃.

Generally, in the initial sintering process, the material layers in the sintering process mainly comprise a sinter belt, a combustion belt, a drying preheating belt, an overwet belt and an original material belt from top to bottom. The burning zone is high in temperature due to ignition of the coke powder in the sintering material layer, and physical and chemical processes such as melting and sintering of minerals are realized at 1200-1400 ℃ to form a finished product sintering ore, namely the burning zone is evolved into a sintering ore zone, and the coke powder is burnt. And because of the influence of exhaust in the exhaust type sintering, fresh air can be continuously supplemented at the top of the material layer to cool the material layer, so that the temperature of the sinter belt is low at a position close to the top of the material layer and high at a position close to the combustion belt.

In the prior art, in order to reduce CO during sintering ₂ And (3) the technology of gas injection assisted sintering is proposed. The gas fuel which is diluted below the lower limit of the combustible concentration is blown above the surface of the sintering material, so that the gas fuel is burnt and heated in the sintering material layer, thereby reducing the solid carbon consumption and CO in the production of the sintering ore ₂ Discharge amount. In fig. 4, the temperature distribution of the sinter bed is compared in the sintering process with and without the gas injection technique. The temperature distribution of the sinter bed without adopting the gas injection technology in the sintering process is shown as a curve corresponding to "without adopting injection" in fig. 4, and the temperature distribution of the sinter bed with adopting the gas injection technology is shown as a curve corresponding to "adopting injection" in fig. 4. As can be seen from fig. 4, after the gas injection technique is adopted, the combustion of the gas fuel widens the high-temperature zone width of the sinter bed during production, and slows down the cooling speed of the sintered finished ore by the fresh air, so that the temperature of the position, close to the combustion zone, in the sinter zone is higher than that of the position, not adopting injection.

To further reduce CO ₂ Laboratory researches and sintering process engineering practices show that in a certain range, the larger the injection quantity and the injection concentration of the fuel gas are, the more heat is released after the fuel gas is sucked into a material layer to replace solid The greater the fuel quantity, and thus the less coke consumption, i.e. the less CO ₂ And (5) discharging. The temperature distribution of the sinter bed after increasing the injection amount and the injection concentration is shown by the dotted line in fig. 5. As can be seen from fig. 5, after increasing the injection amount of the fuel gas and increasing the injection concentration, the ignition position of the fuel gas in the material layer moves from the position of the combustion zone near the sinter zone to the direction of the sinter zone, that is, the temperature at the position of the sinter zone near the combustion zone is higher. The red layer is used for describing the region of the sintering material layer, the temperature of which is above 1000 ℃, and obviously, after the gas injection quantity is increased, the thickness of the red layer in the material layer is obviously increased, and due to the fact that the temperature in the red layer is high and liquid phase is generated, the too thick red layer can cause poor air permeability of the material layer, the sintering exhaust negative pressure is too large, the air quantity and the sintering process of the material layer are influenced, and the yield and the quality of the sintering ore are reduced. That is, the solid carbon consumption and CO in the sinter production are reduced due to the improvement of the gas injection quantity in the gas injection auxiliary sintering process ₂ The discharge amount, however, brings new technical problems.

In the prior art, the conventional sintering assisting method adopting the gas injection technology or the method of injecting and assisting the sintering after increasing the injection quantity and the injection concentration adopts a method of continuously injecting (or injecting) the gas to the surface of the sintered material. Aiming at the problems in the prior art that the injection quantity of the fuel gas is improved, and the injection concentration is increased, the fuel gas is continuously injected to assist in sintering, the invention provides a method for assisting in sintering by periodically injecting the fuel gas at intervals. The method provides a method for changing the original method for continuously spraying the fuel gas in the fuel gas spraying process, and periodically spraying the fuel gas into the material layer of the sintering mixture by adopting a periodic interval spraying measure. As shown in fig. 6, in the present invention, the gas is injected Δt ₁ Stopping spraying for a short time after a period of time ₂ Duration, then continue blowing Δt ₁ Duration and stop of spray Δt ₂ Duration … … is cycled through. Wherein, spray deltat ₁ Duration + stop of spray Δt ₂ The duration is a blowing period, and the process of blowing fuel gas in the whole sintering process is repeated continuously. The blowing duration Δt in a single cycle ₁ In, due to the fuel gasSpraying, namely igniting and burning fuel gas at the position of the area nearby the burning zone and the sintering ore zone to release heat; the stop-spray period deltat in a single period ₂ In the gas burner, the gas is not injected and supplemented, so that the position where the gas is burnt is flameout, and the region is cooled by air. That is, through the periodical jetting of gas, stop spouting, can control the sintering ore area and be close to the ignition of burning area nearby position repeated emergence gas, thereby guarantee that the too high temperature of corresponding region can not appear and arouse too thick red layer, and then effectively avoided the material bed gas permeability relatively poor that brings after improving the gas jetting volume, technical problem such as sintering convulsions negative pressure rising. Further, the invention determines a proper injection system by adjusting parameters of injected fuel gas (such as the cycle number of injected fuel gas, the period of injection in the period, the period of stopping injection in the period, and the like), thereby improving the temperature change curve of the sinter belt and the area near the combustion belt on the premise of maintaining the original fuel gas feeding amount (namely the existing improved fuel gas injection amount), weakening the thickness of a red layer, ensuring proper material layer air permeability and normal exhaust negative pressure, and realizing the maximum fuel gas injection amount on the premise of maintaining the material layer air permeability and the exhaust negative pressure, thereby more obviously improving the solid fuel substitution amount and reducing CO ₂ And (5) discharging.

In the invention, the method for assisting sintering by gas periodic interval injection firstly determines initial parameters of injected gas, wherein the initial parameters of injected gas comprise a period number N of injected gas and a duration deltat of initial injected gas in a single period ₁ Duration Δt of initial fuel gas stopping in single cycle ₂ And the injection amount S of the fuel gas (i.e., the fuel gas injection flow rate) per unit time. After the initial parameters of the injected fuel gas are determined, the fuel gas is injected periodically at intervals to the material surface of the sintering mixture according to the initial parameters, and the fuel gas enters the sintering material layer to burn and supply heat for assisting sintering. Then, the heat quantity Q emitted by the combustion of the injected fuel gas in the sinter bed in a single period is calculated _in Air at Δt ₂ Cooling quantity Q of sinter bed in time _co Judging the temperature change condition of the sintering material layer at the corresponding position in a single period according to the heat balance principle,thereby realizing the control of the temperature of the sinter band and the burning zone area in the sinter bed. The control of the temperature of the sinter belt and the combustion belt area in the sinter layer is realized according to the temperature change condition of the sinter layer in a single period, and the method specifically comprises the following steps: according to the heat balance principle, calculating the temperature change value delta T of the sintering material layer at the position corresponding to the single-period internal combustion gas injection, and then calculating the actual final temperature T of the sintering material layer at the position corresponding to the single-period internal combustion gas injection _co The calculated actual final temperature T _co And target temperature T _aim And comparing, and further adjusting the duration of gas injection in a single period, so as to realize the control of the temperature of the sinter belt and the burning belt area in the sinter layer, and avoid the conditions of overhigh temperature and overlarge red layer.

In the present invention, the target temperature T _aim The temperature critical value which can cause the gas in the sinter zone and the combustion zone to flameout in a single period is summarized according to laboratory research and sintering engineering practice experience. The target temperature T _aim The value of (C) is 600-1000 ℃, preferably 700-850 ℃, more preferably 740-780 ℃. According to the invention, the proper injection system is determined by adjusting the cycle number of injected fuel gas, the injection duration in a single cycle and the stop injection duration in a single cycle, namely, the final temperature of the sinter bed in the control system (10) in the cycle is controlled, so that the trend of a temperature curve between the sinter belt and the vicinity of the combustion belt in the sintering process is precisely controlled, the high-temperature holding time in the sintering process is ensured to be prolonged by supplementing fuel gas but not to be too slow in cooling due to continuous supplementing of fuel gas, the thickness of a red layer is further weakened, and the air permeability and the exhaust negative pressure of the material bed are ensured to be in an optimal state. In the present invention, if the actual final temperature T of the sinter bed is at the corresponding position in a single period _co Target temperature T _aim I.e. the actual final temperature of the sinter bed is within the range of the target temperature, and the gas flameout at the corresponding position of the sinter bed (i.e. the gas flameout at the corresponding position of the gas stopping time interval) shows that the temperature of the sinter belt and the burning belt area are controlled within the normal range in the spraying periodAnd (3) the blowing parameters at the moment are proper blowing parameters, and the system keeps the current blowing parameters to continue to operate. If the actual final temperature T of the sinter bed at the corresponding position in a single period _co Target temperature T _aim The fact that the temperature of the sinter belt and the combustion belt area is higher in the injection period is shown, and at the moment, the condition that the gas at the position corresponding to the sinter layer is not flameout (namely, the gas at the position corresponding to the gas injection stopping time interval is not flameout) possibly occurs, so that the gas permeability of the sinter belt is influenced, and the ventilation negative pressure is increased possibly; the blowing parameters at this time need to be adjusted, for example, the duration of blowing gas in a single cycle is shortened, or the cycle number of blowing gas is increased, or both the duration of blowing gas and the cycle number of blowing gas in a single cycle are adjusted so that T _co ＝T _aim And further controlling the temperature of the sinter band and the combustion band area to return to the normal range. If the actual final temperature T of the sinter bed at the corresponding position in a single period _co < target temperature T _aim At the moment, the gas at the position corresponding to the sinter bed is extinguished (namely, the gas at the position corresponding to the gas stopping and spraying time interval is extinguished), but the temperature of the sinter belt and the combustion belt area is lower in the spraying period, so that the normal operation of sintering and the quality of the sinter can be influenced; the blowing parameters at this time need to be adjusted, for example, the duration of blowing gas in a single cycle is prolonged, or the cycle number of blowing gas is reduced, or both the duration of blowing gas and the cycle number of blowing gas in a single cycle are adjusted so that T _co ＝T _aim And further controlling the temperature of the sinter band and the combustion band area to return to the normal range.

In the process of adjusting the duration of gas injection and/or the cycle number of gas injection in a single cycle according to the present invention, when only the duration of gas injection in a single cycle is adjusted (prolonged or shortened), the cycle number of gas injection is unchanged, so that the duration of gas injection in a single cycle needs to be adjusted (shortened or prolonged) synchronously during the adjustment. When only the cycle number of the injected gas is adjusted (increased or decreased), the duration of the injected gas in a single cycle is not changed, so that synchronous adjustment (shrinkage) is required in the adjustment process Short or prolonged) duration of fuel gas shut down in a single cycle. When the duration of gas injection and the cycle number of gas injection in a single cycle are adjusted simultaneously, the duration of gas injection stopping in the single cycle is also required to be adjusted synchronously. Furthermore, according to formula (4), i.e. the amount of fuel gas injected per unit time

Therefore, when the duration of gas injection and/or the cycle number of gas injection in a single cycle are adjusted, the injection quantity of gas in unit time is synchronously adjusted correspondingly.

In the invention, the total amount of gas required to be blown by the sintering mixture in the sintering trolley

Wherein Q is _{Tonifying device} Since the type of the sintering material, the average particle size of the sintering mixture, the proportion of the solid fuel in the sintering mixture, and the like are determined, it can be seen from the formula that the total amount of the gas required to be blown by the sintering mixture in the sintering carriage is related to the quality of the sintering mixture, the type of the sintering material, the average particle size of the sintering mixture, the proportion of the solid fuel in the sintering mixture, the type of the gas, and the like. In the present invention, the cooling rate q of the sinter bed by air cooling _co ＝h _co ·(T _{Combustion process} -T _∞ ) From the equation, it can be seen that the cooling rate of the sinter bed by air is related to the sinter bed cooling coefficient, the combustion temperature of the gas, the ambient air temperature, the sinter bed inner surface area, the ratio of the combustion zone to the entire sinter bed height in the height direction, and the like. In addition, in the present application, specific values of the respective parameters referred to in the formulas (1) to (10) may be obtained by detection, calculation, or in accordance with production experience or the like.

The number of periods of gas injection and the total amount of gas to be injected into the sinter mix in the sinter trolley are all based on the sinter mix in the region corresponding to the gas injection section. The cycle number of the injected fuel gas is the number of times of injection and stop injection when the sintered mixture passes through the fuel gas injection section. Sintering trolleyThe total amount of the fuel gas required to be blown by the sintering mixture in the furnace is that the maximum fuel gas blowing amount is realized so as to improve the solid fuel substitution amount and reduce CO ₂ On the premise of emission, the gas quantity required to be sprayed by the sintering mixture is required.

In addition, since the "red layer" is a region where the temperature in the sinter bed is about 1000 ℃ or higher, and the region where the temperature in the sinter bed is about 1000 ℃ or higher is mainly concentrated in the combustion zone and a partial region of the sinter zone near the combustion zone, the control of the temperature of the sinter zone and the combustion zone region in the sinter bed is realized, and the control of the thickness of the red layer is realized, mainly by controlling the temperature of the upper region of the combustion zone and the temperature of the sinter zone near the combustion zone position in the thickness direction of the sinter layer within a reasonable range.

In the present application, the "gas combustion position", "gas combustion vicinity position" and "corresponding position" are expressed in the same meaning.

Compared with the prior art, the invention has the following beneficial technical effects:

1. the invention changes the existing method for continuously spraying the fuel gas, adopts the periodically-spaced spraying measure, skillfully controls the spraying and stopping of the fuel gas by periodically-spaced spraying, further repeatedly fires and extinguishes the fuel gas near the burning zone, and supplements heat through the fuel gas feeding layer while keeping a certain cooling time for the sintered finished ore in a specific area, thereby being capable of controlling the temperature of the burning zone and the position of the sintered ore zone without overhigh condition.

2. According to the invention, the proper injection system is determined by selecting and adjusting the cycle number of the injected fuel gas, the injection duration in a single cycle and the stop injection duration in a single cycle, so that the final temperature in the cycle of the sinter bed can be controlled, the trend of a temperature curve near a sinter belt and a combustion belt in the sintering process is precisely controlled, the high-temperature holding time in the sintering process is ensured to be prolonged by supplementing the fuel gas but not to be too slow in cooling due to the continuous supplementing of the fuel gas, the thickness of a red layer is further weakened, and the air permeability and the induced draft negative pressure of the sinter bed are ensured to be in an optimal state.

3. The invention realizes the maximum gas injection quantity in the sintering process under the condition of maintaining the air permeability of the material layer and the normal negative pressure of the air draft, thereby realizing the substitution of solid fuel and CO with larger proportion ₂ And emission reduction.

Drawings

FIG. 1 is a schematic diagram of a method for assisting sintering by gas periodic interval injection;

FIG. 2 is a flow chart of a method for assisting sintering by gas periodic interval injection according to the present invention;

FIG. 3 is a layer distribution diagram of a sinter mix;

FIG. 4 is a graph of sinter bed temperature for both the case of gas injection and the case of no gas injection;

FIG. 5 is a graph showing the temperature of a sinter bed in the case of increasing the concentration of fuel gas injection and in the case of conventional fuel gas injection;

FIG. 6 is a schematic diagram of the periodic intermittent injection of fuel gas according to the present invention;

FIG. 7 is a graph showing the temperature of the sinter bed in the case of the gas injection at periodic intervals and the conventional gas injection continuously according to the present invention.

Reference numerals:

1: sintering trolley; a1: a sinter belt; a2: a combustion zone; a3: drying the preheating zone; a4: overwet belt; a5: the original material belt.

Detailed Description

In the present invention, step 1) comprises the sub-steps of:

wherein: s is the injection quantity of fuel gas in unit time.

q _co ＝h _co ·(T _{combustion process} -T _∞ )·ξ·m·A…………(6)。

Wherein: q (Q) _co Is delta t ₂ And cooling the sinter bed by air in time. h is a _co To sinter the material layer cooling coefficient, h is empirically determined _co The value range of (2) is 50-60W/(m) ² ·℃)。T _{Combustion process} The combustion temperature of the gas in the sintering bed is generally selected empirically in the range of 1000-1200 ℃. T (T) _∞ The air temperature is, for example, 30℃or 25℃or 20℃or the like. And m is the mass of the sintered mixture in the area corresponding to the gas injection section. A is the specific surface area of the combustion zone in the sintered material layer. And xi is the proportion of the combustion zone to the height of the whole sintering material layer in the height direction, and the value range of xi is 0-1, preferably 0.01-0.1.

In the present invention, step 5) comprises the sub-steps of:

c _p ·ξ·m·ΔT＝Q _in -Q _co …………(8)。

namely there is

Wherein: c _p Is the average specific heat capacity of the sinter bed.

T _co ＝T _{Combustion process} +ΔT………(10)。

5c) Comparing the actual final temperature T of the sinter bed in a single cycle _co And target temperature T _aim Further, the duration of gas injection in a single period is adjusted, so that the temperature control of the sinter zone and the burning zone area in the sinter bed is realizedAnd (5) preparing.

Preferably, the substep 5 c) is specifically:

If the actual final temperature T of the sinter bed in a single cycle _co Target temperature T _aim At this time, the duration of gas injection in a single period is shortened, so that T _co ＝T _aim 。

Preferably, in substep 5 c), the target temperature T _aim The value of (C) is 600-1000 ℃, preferably 700-850 ℃, more preferably 740-780 ℃.

Example 1

As shown in fig. 1, in the method for assisting sintering by periodically and alternately spraying gas, the gas is sprayed to the material surface of the sintering mixture at periodic intervals, and the gas enters the sintering material layer to burn and supply heat. In the gas injection process, the temperature of the sinter zone A1 and the temperature of the combustion zone A2 in the sinter bed are controlled by adjusting the gas injection time length in a single period.

As shown in fig. 3, the sinter bed on the sinter trolley 1 mainly comprises a sinter belt A1, a combustion belt A2, a drying preheating belt A3, an overwetting belt A4 and an original material belt A5 from top to bottom in sequence along the thickness direction of the sinter bed.

Example 2

A method for assisting sintering by periodically and alternately spraying fuel gas to the material surface of a sintering mixture comprises the steps of periodically and alternately spraying fuel gas, and enabling the fuel gas to enter a sintering material layer for burning and heating. In the gas injection process, the temperature of the sinter zone A1 and the temperature of the combustion zone A2 in the sinter bed are controlled by adjusting the gas injection time length in a single period.

The method for controlling the temperature of the areas of the sinter belt A1 and the combustion belt A2 in the sinter bed specifically comprises the following steps:

5) And judging the temperature change condition of the sinter bed in a single period according to the heat released by the combustion of the injected fuel gas and the cooling quantity of air to the sinter bed, so as to realize the control of the temperatures of the sinter zone A1 and the combustion zone A2 in the sinter bed.

Example 3

As shown in fig. 2, the implementation of the control of the temperature of the sinter band A1 and the combustion band A2 in the sinter bed specifically includes the following steps:

Step 1) comprises the following sub-steps:

In the step 2), the total amount of gas required to be blown by the sintering mixture in the sintering trolley is as follows:

wherein: g is the total amount of gas required to be blown by the sintering mixture in the sintering trolley. And m is the mass of the sintered mixture in the area corresponding to the gas injection section. Q (Q) _{Tonifying device} The heat is needed to be supplemented for the sintered mixture of unit mass after the solid fuel ratio is reduced as a whole. H is the heat value of the fuel gas.

The gas injection quantity in the unit time is calculated, and the gas injection quantity is specifically as follows:

wherein: s is the injection quantity of fuel gas in unit time.

3) In the single period of gas injection time, calculating the heat emitted by the injected gas in the sintering material layer, wherein the heat is specifically as follows:

4) In the gas stopping time of a single period, the cooling quantity of air to the sinter bed is calculated, and the method specifically comprises the following steps: stop time Δt for a single cycle ₂ In the sintering material layer, the cooling rate of the sintering material layer cooled by air is q _co The method comprises the following steps:

q _co ＝h _co ·(T _{combustion process} -T _∞ )·ξ·m·A…………(6)。

Wherein: q (Q) _co Is delta t ₂ And cooling the sinter bed by air in time. h is a _co For the cooling coefficient of the sinter bed, h _co The value of (2) is 60W/(m) ² ·℃)。T _{Combustion process} Is the combustion temperature of the fuel gas in the sintering material layer. T (T) _∞ Is the air temperature. And m is the mass of the sintered mixture in the area corresponding to the gas injection section. A is the specific surface area of the combustion zone in the sintered material layer. And xi is the proportion of the combustion zone to the height of the whole sintering material layer in the height direction, and the value of xi is 0.07.

Step 5) comprises the sub-steps of:

c _p ·ξ·m·ΔT＝Q _in -Q _co …………(8)。

namely there is

Wherein: c _p Is the average specific heat capacity of the sinter bed.

T _co ＝T _{Combustion process} +ΔT…………(10)。

5c) Comparing the actual final temperature T of the sinter bed in a single cycle _co And target temperature T _aim And further adjusting the duration of gas injection in a single period, thereby realizing the control of the temperatures of the areas of the sinter belt A1 and the combustion belt A2 in the sinter bed.

Example 4

Example 3 is repeated, except that in substep 5 c) the target temperature T _aim The value of (2) is 700 ℃.

The substep 5 c) is specifically:

If the actual final temperature T of the sinter bed in a single cycle _co Target temperature T _aim At the moment, the duration of gas injection in a single period is shortened, so that T is formed _co ＝T _aim ；

Example 5

Example 4 is repeated, except that in substep 5 c) the target temperature T _aim The value of (2) is 850 ℃.

Example 6

Example 4 is repeated, except that in substep 5 c) the target temperature T _aim The range of values of (2) is 750 ℃.

Application example 1

Step 1) comprises the following sub-steps:

1a) According to the length L=16m of the gas injection section on the sintering machine and the running speed v=2m/min of the sintering trolley, calculating the running time t of the sintering trolley in the gas injection section, namely, the total duration t of gas injection to the sintering mixture in the sintering trolley is as follows:

1b) Setting a cycle number N=10 of injecting fuel gas to the sintering mixture in the sintering trolley and a duration deltat of initial fuel gas injection in a single cycle ₁ =30s, whereby the initial fuel gas stopping time Δt in a single cycle ₂ The method comprises the following steps:

wherein: g is the firing in the sintering trolleyThe total amount of gas to be blown is required for the mix. m is the mass of the sintering mixture in the area corresponding to the gas injection section, and m= 172800kg. Q (Q) _{Tonifying device} To supplement heat for the sintered mixture of unit mass after the solid fuel is mixed integrally, Q _{Tonifying device} =12000 kJ/kg. H is the heating value of the gas, h= 35588kJ/m ³ 。

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wherein: s is the injection quantity of fuel gas in unit time.

q _co ＝h _co ·(T _{combustion process} -T _∞ )·ξ·m·A…………(6)。

Wherein: q (Q) _co Is delta t ₂ And cooling the sinter bed by air in time. h is a _co For the cooling coefficient of the sinter bed, h _co ＝50W/(m ² ·℃)。T _{Combustion process} T is the combustion temperature of fuel gas in the sintering material layer _{Combustion process} ＝1200℃。T _∞ Is airTemperature, T _∞ =30℃. m is the mass of the sintering mixture in the area corresponding to the gas injection section, and m= 172800kg. A is the specific surface area of a combustion zone in the sintered material layer, and A= 0.02326m ² And/g. ζ is the ratio of the combustion zone to the total sinter bed height in the height direction, ζ=0.05.

Step 5) comprises the sub-steps of:

5a) According to the heat balance principle, calculating a temperature change value delta T of a sintering material layer at a position near the combustion of the gas in a single period:

c _p ·ξ·m·ΔT＝Q _in -Q _co …………(8)。

namely there is

Wherein: c _p C is the average specific heat capacity of the sinter bed _p ＝1.1kJ/(kg·℃)。

5b) Calculating the actual final temperature T of the sinter bed at a position near the combustion of the gas in a single period _co ：

T _co ＝T _{Combustion process} +ΔT＝1200℃+(-448℃)＝752℃…………(10)。

Due to the target temperature T _aim =752 ℃, obviously with T _co ＝T _aim It is explained that the temperature of the sinter band A1 and the combustion band A2 is controlled in the normal range in the period, and the system keeps the current injection parameters to continue to operate.

Application example 2

Step 1) comprises the following sub-steps:

1b) Setting a cycle number N=10 of injecting fuel gas to the sintering mixture in the sintering trolley and a duration deltat of initial fuel gas injection in a single cycle ₁ =30.3 s, whereby the initial fuel gas cut-off duration Δt in a single cycle ₂ The method comprises the following steps:

wherein: g is the total amount of gas required to be blown by the sintering mixture in the sintering trolley. m is the mass of the sintering mixture in the area corresponding to the gas injection section, and m= 172800kg. Q (Q) _{Tonifying device} To supplement heat for the sintered mixture of unit mass after the solid fuel is mixed integrally, Q _{Tonifying device} =12000 kJ/kg. H is the heating value of the gas, h= 35588kJ/m ³ 。

wherein: s is the injection quantity of fuel gas in unit time.

q _co ＝h _co ·(T _{combustion process} -T _∞ )·ξ·m·A…………(6)。

Wherein: q (Q) _co Is delta t ₂ And cooling the sinter bed by air in time. h is a _co For the cooling coefficient of the sinter bed, h _co ＝50W/(m ² ·℃)。T _{Combustion process} In which the fuel gas is in the sintered material layerCombustion temperature, T _{Combustion process} ＝1200℃。T _∞ Is the air temperature, T _∞ =30℃. m is the mass of the sintering mixture in the area corresponding to the gas injection section, and m= 172800kg. A is the specific surface area of a combustion zone in the sintered material layer, and A= 0.02326m ² And/g. ζ is the ratio of the combustion zone to the total sinter bed height in the height direction, ζ=0.05.

Step 5) comprises the sub-steps of:

c _p ·ξ·m·ΔT＝Q _in -Q _co …………(8)。

namely there is

T _co ＝T _{Combustion process} +ΔT＝1200℃+(-77)℃＝1123℃…………(10)。

Due to the target temperature T _aim =752 ℃, i.e. T _co ＞T _aim The method shows that in the injection period, the temperature of the sinter belt and the combustion belt area is higher, and the gas in the sinter material layer is not extinguished in the interval time of possibly stopping the injection of the gas, so that the too thick red layer appears to influence the gas permeability of the material layer and causeUnder the condition of rising suction negative pressure, the duration of gas injection in a single period is shortened at the moment, so that T is formed _co ＝T _aim And further controlling the temperature of the sinter band and the combustion band area to return to the normal range.

Application example 3

Step 1) comprises the following sub-steps:

1b) Setting a cycle number N=10 of injecting fuel gas to the sintering mixture in the sintering trolley and a duration deltat of initial fuel gas injection in a single cycle ₁ =29.7 s, whereby the initial fuel gas cut-off duration Δt in a single cycle ₂ The method comprises the following steps:

wherein: s is the injection quantity of fuel gas in unit time.

q _co ＝h _co ·(T _{combustion process} -T _∞ )·ξ·m·A…………(6)。

Wherein: q (Q) _co Is delta t ₂ And cooling the sinter bed by air in time. h is a _co For the cooling coefficient of the sinter bed, h _co ＝50W/(m ² ·℃)。T _{Combustion process} T is the combustion temperature of fuel gas in the sintering material layer _{Combustion process} ＝1200℃。T _∞ Is the air temperature, T _∞ =30℃. m is the mass of the sintering mixture in the area corresponding to the gas injection section, and m= 172800kg. A is the specific surface area of a combustion zone in the sintered material layer, and A= 0.02326m ² And/g. ζ is the ratio of the combustion zone to the total sinter bed height in the height direction, ζ=0.05.

Step 5) comprises the sub-steps of:

c _p ·ξ·m·ΔT＝Q _in -Q _co …………(8)。

namely there is

T _co ＝T _{Combustion process} +ΔT＝1200℃+(-819)℃＝381℃…………(10)。

Due to the target temperature T _aim =752 ℃, i.e. T _co ＜T _aim The temperature of the sinter belt and the area of the combustion belt in the injection period is lower, the normal operation of sintering and the quality of the sinter can be affected, and the duration of gas injection in a single period is prolonged at the moment, so that T is caused _co ＝T _aim And further controlling the temperature of the sinter band and the combustion band area to return to the normal range.

Comparative example 1

A method for assisting sintering by continuously spraying gas includes continuously spraying gas to the material surface of the sintering mixture, enabling the gas to enter the sintering material layer for burning and heating, and assisting sintering. Wherein, the total amount G of continuously injected fuel gas is aimed at the sintering mixture in the corresponding area of the fuel gas injection section ₁ ＝58266.83m ³ The total amount G of the gas continuously injected here ₁ The total amount of gas G injected at periodic intervals in application example 1 was equal. According to the length L of the gas injection section on the sintering machine ₁ Run speed v of sintering pallet of =16m ₁ The total duration t of gas injection to the sinter mix in the sinter trolley is calculated =2m/min ₁ ＝L ₁ /v ₁ 480s, total duration t of gas injection to sinter mix in sinter trolley ₁ The total duration t (including the blowing period and the stopping period) of the gas blowing to the sinter mix in the sinter trolley in application example 1 was equal. In comparative example 1, the gas injection flow rate is the injection amount S of gas per unit time ₁ ＝G ₁ /t ₁ ＝121.39m ³ /s。

The temperature of the sintered material layer during sintering was measured, and the temperature change curves of the sintered material layers of application example 1 and comparative example 1 were plotted as shown in fig. 7. Relevant test data of application example 1 and comparative example 1 were recorded as follows:

the invention changes the existing method for continuously spraying fuel gas, adopts the periodical intermittent spraying measure to burnThe gas is sprayed into the sintering material layer. As can be seen from the above table in combination with FIG. 7, the present invention can ensure a large proportion of solid fuel substitution, CO, by achieving the maximum fuel injection amount while maintaining the original fuel gas injection amount ₂ On the premise of emission reduction, the temperature change curve of the sinter belt and the area near the combustion belt is improved, the thickness of a red layer is further weakened, and the proper air permeability of a material layer and normal exhaust negative pressure are ensured, so that the yield and quality of the sinter are improved.

Claims

1. A method for assisting sintering by gas periodic interval injection is characterized by comprising the following steps: periodically injecting fuel gas at intervals to the material surface of the sintering mixture, and enabling the fuel gas to enter a sintering material layer for burning and heating; in the process of gas injection, the temperature of a sinter zone and a combustion zone area in a sinter layer is controlled by adjusting the duration of gas injection in a single period;

the method for controlling the temperature of the sinter belt and the combustion belt area in the sinter bed specifically comprises the following steps:

1) Determining the cycle number of the gas injection, the duration of the initial gas injection in a single cycle and the duration of the initial gas stopping injection in a single cycle;

2) Calculating the injection quantity of the fuel gas in unit time according to the total quantity of the fuel gas required to be injected by the sintering mixture in the sintering trolley;

3) In the single period of gas injection time, calculating the heat released by the combustion of the injected gas in the sinter bed;

4) Calculating the cooling capacity of air to the sinter bed in the gas blowout time of a single period;

2. The method according to claim 1, characterized in that: step 1) comprises the following sub-steps:

1a) According to the length L of the gas injection section on the sintering machine, the running speed v of the sintering trolley is calculated, and the running time t of the sintering trolley in the gas injection section, namely the total duration t of gas injection of the sintering mixture in the sintering trolley is as follows:

3. the method according to claim 2, characterized in that: in the step 2), the total amount of gas required to be blown by the sintering mixture in the sintering trolley is as follows:

wherein: g is the total amount of gas required to be blown by the sintering mixture in the sintering trolley; m is the mass of the sintered mixture in the corresponding area of the gas injection section; q (Q) _{Tonifying device} The heat is needed to be supplemented for the sintered mixture of unit mass after the solid fuel ratio is integrally reduced; h is the heat value of the fuel gas.

4. A method according to claim 3, characterized in that: in step 2), the calculation of the injection amount of the fuel gas in the unit time specifically includes:

wherein: s is the injection quantity of fuel gas in unit time.

5. The method according to claim 4, wherein: in step 3), the heat released by the combustion of the injected fuel gas in the sinter bed is calculated within the fuel gas injection time of a single period, specifically:

6. The method according to claim 5, wherein: in step 4), the cooling amount of air to the sinter bed is calculated in the fuel gas stopping time of a single period, specifically: stop time Δt for a single cycle ₂ In the sintering material layer, the cooling rate of the sintering material layer cooled by air is q _co The method comprises the following steps:

q _co ＝h _co ·(T _{combustion process} -T _∞ )·ξ·m·A…………(6)；

Wherein: q (Q) _co Is delta t ₂ Cooling amount of air to the sinter bed in time; h is a _co For the cooling coefficient of the sinter bed, h _co The value range of (2) is 50-60W/(m) ² ·℃)；T _{Combustion process} The combustion temperature of the fuel gas in the sintering material layer is set; t (T) _∞ Is the air temperature; m is the mass of the sintered mixture in the corresponding area of the gas injection section; a is the specific surface area of a combustion zone in the sintered material layer; and xi is the proportion of the combustion zone to the height of the whole sintering material layer in the height direction, and the value range of xi is 0-1.

7. The method according to claim 6, wherein:the value range of xi is 0.01-0.1。

8. The method according to claim 6, wherein: step 5) comprises the sub-steps of:

5a) According to the heat balance principle, calculating a temperature change value delta T of a sintering material layer at a gas combustion position in a single period:

c _p ·ξ·m·ΔT＝Q _in -Q _co …………(8)；

namely there is

Wherein: c _p The average specific heat capacity of the sinter bed;

T _co ＝T _{Combustion process} +ΔT…………(10)；

9. The method according to claim 8, wherein: the substep 5 c) is specifically:

if the actual final temperature T of the sinter bed in a single cycle _co Target temperature T _aim The temperature of the sintering ore belt and the temperature of the combustion belt are controlled in a normal range in the period, and the system keeps the current blowing parameters to continue to operate;

If the actual final temperature T of the sinter bed in a single cycle _co < target temperature T _aim At this time, the time of injecting the fuel gas in a single period is prolongedLong, so that T _co ＝T _aim 。

10. The method according to claim 8 or 9, characterized in that: in sub-step 5 c), the target temperature T _aim The value range of (2) is 600-1000 ℃.

11. The method according to claim 8 or 9, characterized in that: in sub-step 5 c), the target temperature T _aim The value range of (2) is 700-850 ℃.

12. The method according to claim 8 or 9, characterized in that: in sub-step 5 c), the target temperature T _aim The range of the value of (C) is 740-780 ℃.