Method for producing pellets by using blast furnace gas and converter gas in grate-rotary kiln

Abstract

The invention belongs to the technical field of iron and steel smelting, and particularly discloses a method for producing pellets by using blast furnace gas and converter gas in a grate-rotary kiln, which comprises the following steps: starting a combustion fan, closing a main valve of a fan air door, igniting by using an ignition gun, feeding to the lower part of a kiln head burner, opening a valve of natural gas, and starting a combustion furnace; a main air door valve of a combustion fan is gradually opened, meanwhile, the valve opening degree of rotational flow air and the valve opening degree of direct flow air are adjusted to be 70% and 30% respectively, when the kiln tail temperature reaches 800 DEG C, a converter gas valve is opened, the valve opening degree of the converter gas valve is 10%, and when the kiln tail temperature reaches 900 DEG C, a blast furnace gas valve is opened, the valve opening degree of the blast furnace gas valve is 20%, and the valve opening degree of the blast furnace gas valve is 20%; and when the temperature of the kiln tail reaches 950-980 DEG C, material distribution is started, and production is carried out. In order to solve the problem of high production cost caused by the fact that natural gas needs to be purchased as fuel to roast pellets at present, the pellet production is carried out in a blast furnace gas and converter gas co-combustion mode, so that the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of steel smelting, and in particular to a method for producing pelletized ore by using blast furnace gas and converter gas in a chain grate-rotary kiln. Background Art

[0002] Chain grate-rotary kiln is the main process for roasting pellets, with the characteristics of high temperature, large scale, continuous, high temperature and closed. The production of pellets by chain grate-rotary kiln is divided into four process sections: batching, pelletizing, roasting and cooling. Among them, the chain grate-rotary kiln system belongs to the roasting and cooling process section. The control and regulation of the thermal system of the system is one of the most important links in the whole pellet production process.

[0003] The heat sources used in pellet production include natural gas, blast furnace gas, pulverized coal, etc. Considering the heat demand in the pellet production process, the fuels used in pellet production are generally blast furnace gas and natural gas or pulverized coal. The combustion of a single blast furnace gas cannot reach the heat required for pellet production. Among these fuels, blast furnace gas is an auxiliary product produced by blast furnaces in full-process steel enterprises. Its use in production can make full use of energy and reduce costs. However, natural gas and pulverized coal are both externally purchased fuels, and their use will increase the cost and energy consumption of the production unit.

[0004] The purpose of the present invention is to provide a method for producing pellets by using blast furnace gas and converter gas in a chain grate-rotary kiln to address the situation in which the production cost is high due to the use of a portion of purchased natural gas and coal powder in the production process of pellets. The method can effectively utilize the calorific value of the converter gas to make up for the shortcoming that the calorific value of the blast furnace gas production does not meet the production needs, and has a very obvious promoting effect on stabilizing the system temperature, increasing the output of pellets, and extending the ring-forming period of the rotary kiln.

[0005] Therefore, it is necessary to design a method for producing pellets using blast furnace gas and converter gas using a chain grate-rotary kiln. By reducing the purchase of natural gas, pulverized coal and other fuels, and adding the company's own converter gas, the production cost can be reduced, the relatively suitable calorific value of converter gas can be fully utilized, the temperature of the rotary kiln system can be optimized, and the output of pellets can be increased. This is used to solve the problem of high production costs when using blast furnace gas and natural gas or pulverized coal as fuel to produce pellets because both natural gas and pulverized coal need to be purchased from outside. Summary of the invention

[0006] The object of the present invention is to provide a method for producing pellets by using blast furnace gas and converter gas in a chain grate-rotary kiln, so as to solve the problem of high production cost caused by using a part of purchased natural gas and coal powder in the process of producing pellets.

[0007] To achieve the above object, the basic scheme provided by the present invention is: a method for producing pellets using blast furnace gas and converter gas by a chain grate-rotary kiln, comprising the following steps:

[0008] S1: Before pelletizing, first turn on the combustion-supporting fan and close the main valve of the fan damper;

[0009] S2: Use an ignition gun to ignite and send it to the bottom of the kiln head burner, then open the natural gas valve, the opening of the natural gas valve is 10%;

[0010] S3: Open the main valve of the fan damper, and then adjust the valve opening of the swirl air to 70% and the valve opening of the direct air to 30%;

[0011] S4: When the staff in the central control room observe that the temperature at the kiln tail reaches 800℃ and the flame is continuous and stable, they open the valve of the converter gas and burn the converter gas according to the opening of the converter gas valve of 10%;

[0012] S5: When there is an obvious flame of converter gas burning in front of the burner, that is, the flame is bright, first close the natural gas valve, then gradually increase the opening of the converter gas valve to adjust the amount of converter gas;

[0013] S6: When the staff in the central control room observed that the temperature at the kiln tail reached 900°C, they opened the valve of the blast furnace gas, and the valve opening of the blast furnace gas was 20%;

[0014] S7: When there is an obvious flame of blast furnace gas burning in front of the burner, that is, the flame is blue, start to adjust the amount of blast furnace gas, and adjust the valve opening of blast furnace gas to 90%-100%;

[0015] S8: When the staff in the central control room observe that the temperature at the kiln tail reaches 950℃-980℃, they start laying the materials.

[0016] The beneficial effects of the present invention are as follows: (1) the present invention uses converter gas and blast furnace gas as production fuels, produces pellets by co-burning converter gas and blast furnace gas, and uses the company's self-produced converter gas instead of natural gas to produce pellets, thereby reducing the purchase of natural gas and further reducing the production cost of pellets;

[0017] (2) During operation, the temperature at the kiln head is adjusted by adjusting the amount of converter gas, the temperature at the kiln tail is adjusted by adjusting the amount of blast furnace gas, and the high-temperature section position in the kiln is adjusted by adjusting the valve opening of the swirl air and the direct current air, thereby extending the ring-forming cycle of the rotary kiln; it can avoid the high-temperature position in the kiln being concentrated, resulting in the temperature of the green balls rising too fast after entering the kiln, causing the green balls to burst, thereby affecting the yield; and the powder generated after the green balls burst will liquefy in the kiln and adhere to the kiln wall to form rings. The rings will not only increase the equipment load, but also increase the longitudinal length and thickness of the rings if not handled in time. When the rings fall, the labor intensity of the workers will also increase. The shutdown for processing will also affect the output of the pellets.

[0018] In summary, the use of mixed combustion of converter gas and blast furnace gas to produce pellets can not only reduce the purchase of natural gas, coal powder and other fuels, thereby reducing the production cost of pellets, but also prevent the raw balls from bursting due to excessively rapid temperature rise after entering the kiln, thereby extending the ring formation cycle in the kiln and increasing the output of pellets.

[0019] Option 2 is the preferred basic option. In S4, when the staff in the central control room observes that the temperature at the kiln tail reaches 800℃ and the flame is stable, the valve opening of the swirl air is adjusted to 20%, and the valve opening of the direct current air is adjusted to 80%. After that, the valve openings of the swirl air and the direct current air are adjusted alternately every 4 hours, and this cycle is repeated. The position of the high-temperature section in the rotary kiln is adjusted by adjusting the valve openings of the swirl air and the direct current air to avoid the concentration of high-temperature positions, which will cause the temperature of the green balls to rise too quickly when they enter the rotary kiln, causing the green balls to burst.

[0020] Scheme 3 is the preferred basic scheme. In S5, the amount of converter gas is gradually adjusted, and the valve opening of the converter gas is adjusted from the opening in S4 to 20%-40%; by adjusting the amount of converter gas, the temperature of the kiln head is adjusted.

[0021] Scheme 4 is the preferred basic scheme. In S5, the converter gas consumption is maintained at 3000-3700m 3 / h; to ensure stable combustion of converter gas.

[0022] Scheme 5 is the preferred basic scheme. In S7, the amount of blast furnace gas is gradually adjusted, and the valve opening of the blast furnace gas is adjusted from the opening in S6 to 90%-100%; by adjusting the amount of blast furnace gas, the temperature of each section of the kiln tail and the chain grate is adjusted.

[0023] Scheme 6: This is the preferred basic scheme. In S7, the consumption of blast furnace gas is maintained at 11000-13000m 3 / h; ensure stable combustion of blast furnace gas. DETAILED DESCRIPTION

[0024] Example 1

[0025] A method for producing pelletized ore using blast furnace gas and converter gas by using a chain grate-rotary kiln comprises the following steps:

[0026] S1: Before pelletizing, first turn on the combustion-supporting fan and close the main valve of the fan damper;

[0027] S2: Use an ignition gun to ignite and send it to the bottom of the kiln head burner, then open the natural gas valve, the opening of the natural gas valve is 10%;

[0028] S3: Open the main valve of the fan damper, and then adjust the valve opening of the swirl air to 70% and the valve opening of the direct air to 30%;

[0029] S4: When the staff in the central control room observed that the temperature at the kiln tail reached 800℃ and the flame was continuous and stable, that is, the shape of the flame was like a brush, thick in the middle and thin at the end, the valve of the converter gas was opened, and the valve opening of the converter gas was 10%, and it was burned with natural gas. Then the valve opening of the swirl air was adjusted to 20%, and the valve opening of the direct current air was adjusted to 80%. After that, the valve openings of the swirl air and the direct current air were adjusted alternately every 4 hours, and this cycle was repeated.

[0030] S5: When the staff in the central control room and the on-site personnel confirm that there is an obvious flame of converter gas burning in front of the burner, that is, the flame is bright, first close the natural gas valve, then gradually increase the converter gas valve opening, and adjust the converter gas consumption. The converter gas valve opening is gradually adjusted from the opening in S4 to 20%-40%, and the converter gas consumption is 3000-3700m 3 / h;

[0031] S6: When the staff in the central control room observed that the temperature at the kiln tail reached 900°C, they opened the valve of the blast furnace gas, with the valve opening of the blast furnace gas at 20%, and burned it with the converter gas;

[0032] S7: When the staff in the central control room and the on-site personnel confirm that there is an obvious flame of blast furnace gas burning in front of the burner, that is, the flame is blue, the valve opening of the blast furnace gas is gradually increased to adjust the amount of blast furnace gas. The valve opening of the blast furnace gas is gradually adjusted from the opening in S6 to 90%-100%. The consumption of blast furnace gas is 11000-13000m 3 / h;

[0033] S8: When the staff in the central control room observe that the temperature at the kiln tail reaches 950℃-980℃, they start to place the materials;

[0034] S9: Finally, the finished pellets are subjected to a compression test. If the compression test reaches 2.6KN or above, the finished pellets are qualified. If not, the rotation speed of the rotary kiln is adjusted.

[0035] Through the above production method, it is easier to successfully ignite by first using natural gas with a lower ignition point. Then, when the temperature at the kiln tail reaches 800°C, a certain amount of converter gas is introduced for mixed combustion, which can make the converter gas fully burn. When the temperature at the kiln tail reaches 900°C, blast furnace gas is introduced for mixed combustion. The order of introducing the above fuels can make the converter gas and blast furnace gas burn fully, avoiding incomplete combustion of the fuel and explosion accidents.

[0036] Table 1: Fuel cost table

[0037]

[0038] In Table 1, when the blast furnace gas usage is the same, the blast furnace gas usage is 12000m 3 / h, 800m 3 / h natural gas or 3500m 3 / h converter gas and 12000m 3 / h of blast furnace gas, when converter gas and blast furnace gas are mixed for pellet production, the output is higher than when natural gas and blast furnace gas are mixed; and under this fuel structure, energy consumption is reduced by 5.58kgce / t and fuel cost is reduced by 15.75 yuan / ton.

[0039] In summary, the production of pellets by mixed combustion of converter gas and blast furnace gas in Example 1 not only reduces energy consumption and fuel costs, but also increases output; by adjusting the valve openings of the swirl air and the direct current air, the high-temperature position is continuously changed in the kiln, and the high-temperature position is concentrated, so that the raw balls are prevented from bursting due to excessive temperature increase when entering the kiln, resulting in a low yield of pellets; at the same time, it can also avoid the excessively concentrated high-temperature position causing the rotary kiln to form rings, and the ring formation period is extended from about 30 days to 55 days. It can be seen that by adjusting the valve openings every 4 hours, the high-temperature position can be adjusted to a certain value every 4 hours. The valve opening of the secondary swirl air and the direct current air improves the yield of the pellets and prolongs the ring formation period in the kiln, thereby increasing the output of the pellets. In Example 1, the production is carried out in the manner of sequentially introducing natural gas, converter gas and blast furnace gas to ensure production safety. If the production is carried out in the manner of sequentially introducing natural gas, blast furnace gas and converter gas, since the ignition point of blast furnace gas is higher than that of converter gas, incomplete combustion of blast furnace gas is likely to occur. When the incompletely burned gas enters the chain grate and the dust collector, explosion accidents are likely to occur.

[0040] The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for producing pellets using blast furnace gas and converter gas in a grate-rotary kiln, characterized in that: The following steps are involved: S1: Before pelletizing, first turn on the combustion-supporting fan and close the main valve of the fan damper; S2: Use an ignition gun to ignite and send it to the bottom of the kiln head burner, then open the natural gas valve, the opening of the natural gas valve is 10%; S3: Open the main valve of the fan damper, and then adjust the valve opening of the swirl air to 70% and the valve opening of the direct air to 30%; S4: When the staff in the central control room observe that the temperature at the kiln tail reaches 800℃ and the flame is continuous and stable, they open the valve of the converter gas and burn the converter gas according to the opening of the converter gas valve of 10%; S5: When there is an obvious flame of converter gas burning in front of the burner, that is, the flame is bright, first close the natural gas valve, then gradually increase the opening of the converter gas valve to adjust the amount of converter gas; S6: When the staff in the central control room observed that the temperature at the kiln tail reached 900°C, they opened the valve of the blast furnace gas, and the valve opening of the blast furnace gas was 20%; S7: When there is an obvious flame of blast furnace gas burning in front of the burner, that is, the flame is blue, start to adjust the amount of blast furnace gas, and adjust the valve opening of blast furnace gas to 90%-100%; S8: When the staff in the central control room observe that the temperature at the kiln tail reaches 950℃-980℃, they start laying the materials.

2. The method for producing pellets using blast furnace gas and converter gas by using a chain grate-rotary kiln according to claim 1, characterized in that: In S4, when the staff in the central control room observed that the temperature at the kiln tail reached 800℃ and the flame was stable, the valve opening of the swirl air was adjusted to 20%, and the valve opening of the direct current air was adjusted to 80%. After that, the valve openings of the swirl air and direct current air were adjusted alternately every 4 hours, and this cycle was repeated.

3. The method for producing pellets using blast furnace gas and converter gas by using a chain grate-rotary kiln according to claim 1, characterized in that: In S5, the amount of converter gas is gradually adjusted, and the opening of the converter gas valve is adjusted from the opening in S4 to 20%-40%.

4. The method for producing pellets using blast furnace gas and converter gas by using a chain grate-rotary kiln according to claim 1, characterized in that: In S5, the converter gas consumption is maintained at 3000-3700m 3 / h.

5. The method for producing pellets by using a chain grate-rotary kiln using blast furnace gas and converter gas according to claim 1, characterized in that: In S7, the amount of blast furnace gas is gradually adjusted, and the valve opening of the blast furnace gas is adjusted from the opening in S6 to 90%-100%.

6. The method for producing pellets by using a chain grate-rotary kiln using blast furnace gas and converter gas according to claim 1, characterized in that: In S7, the consumption of blast furnace gas is maintained at 11000-13000m 3 / h.

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