Belt roaster heating system and method using blast furnace gas + pulverized coal as fuel

Abstract

The present invention relates to a heating system and method for a pellet belt roaster fueled by blast furnace gas and pulverized coal. The system comprises a belt roaster comprising a forced air drying section, an exhaust air drying section, a preheating section, a roasting section, a soaking section, a first cooling section, a second cooling section, and fume hoods correspondingly disposed above each section. The functional sections are separated by furnace walls. A pair of combustion chambers A and a preheating section heating system A are correspondingly disposed on the preheating section fume hood of the belt roaster, while a pair of combustion chambers B and a roasting section heating system B are correspondingly disposed on the roasting section fume hood of the belt roaster. By utilizing a mixture of blast furnace gas and pulverized coal as fuel, the present invention resolves the problem of the belt roaster having to use high-calorific value gas fuel, thus overcoming fuel restrictions. Furthermore, blast furnace gas is a byproduct gas resource produced during the blast furnace ironmaking process in steel mills. Its efficient utilization can reduce costs and increase efficiency for steel enterprises.

Description

Technical Field

[0001] The invention belongs to the technical field of pellet production, and in particular relates to a belt roaster heating system using blast furnace gas and pulverized coal as fuel and a method thereof. Background Art

[0002] There are three main methods for producing pellets, including belt roasters, grate kilns, ring coolers, and vertical furnaces. Belt roasters have developed rapidly due to their good adaptability to raw materials and large-scale equipment, and are currently the most widely used method.

[0003] To ensure pellet quality, the belt roaster requires maintaining a certain combustion temperature during the roasting process. Therefore, high-calorific-value natural gas, coke oven gas, and heavy oil are used as fuels. However, my country's natural gas resources are scarce, coke oven gas sources are limited, and there is a shortage of coke oven gas within steel mills. The high cost of high-calorific-value gas is also one of the main factors limiting the development of the belt roasting pelletizing process.

[0004] Blast furnace gas is a by-product gas resource in the blast furnace ironmaking process. It is cheap and has a calorific value of about 3350~4180 kJ / m 3 This is a low-calorific-value surplus gas that can solve the fuel gas problem in steel mills' belt roasting pelletizing processes and expand the range of fuel gases used by belt roasters for pelletizing. Patent CN 212778604 U discloses a combustion system for roasting pellets in a belt roaster. To avoid the consumption of high-calorific-value fuel gas and significantly reduce production costs, this patent directly uses blast furnace gas as fuel. However, the theoretical combustion temperature of blast furnace gas is typically 1400-1500°C, while the actual combustion temperature is 1050-1150°C, which does not meet the belt roaster's required roasting temperature of 1250-1350°C. Patent CN 103234350 A discloses a hot air supply system for a belt roaster, using a hot air furnace burning pulverized coal to provide hot air to the belt roaster. Its advantages are that pulverized coal is economical and practical, with high thermal efficiency and sufficient combustion. However, this patent ignores the difficulty in slagging that can arise when using pulverized coal as fuel. During the energy crisis, US belt roasters employed coal injection technology, adding a coal-fired combustion chamber adjacent to the belt roaster to provide heat. However, this technology was discontinued due to difficulties with slagging (the difficulty in achieving liquid slagging). In the boiler industry, the most economical and effective method is to mix blast furnace gas and pulverized coal, which provides more complete combustion, greater combustion stability, and higher thermal efficiency. However, this method was not adopted in belt roasters.

[0005] Under the existing technology, the thermal system of a belt roaster consists of three major parts, namely the belt roaster body, the belt roaster combustion and heating system, and the various fan devices in the system. In addition, according to the process direction, the belt roaster body is sequentially provided with a drying section, a drying section, a preheating section, a roasting section, a soaking section, a first cooling section, and a second cooling section. The combustion and heating system generally provides heat for the roasting of pellets through gas burners. Multiple burners are symmetrically arranged along both sides of the roaster. According to the actual requirements of each process section of the roaster, group control can be achieved to meet the temperature requirements of different process sections. However, since the fuel of previous belt roasters is different from that of the present invention and cannot meet the requirements of the existing technology, the structure of the combustion chamber is improved. Summary of the Invention

[0006] The present invention provides a pellet belt roaster heating system and method using blast furnace gas and pulverized coal as fuel, so as to achieve the purpose of enabling the belt roaster heating system to accurately heat the pellets to be heated in the preheating section and the roasting section, and is committed to solving the slag discharge problem caused by the combustion of pulverized coal.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention discloses a pellet belt roaster heating system using blast furnace gas and pulverized coal as fuel, comprising a belt roaster, wherein the belt roaster comprises a blast drying section, an exhaust drying section, a preheating section, a roasting section, a soaking section, a first cooling section, and a second cooling section; above the blast drying section, the exhaust drying section, the preheating section, the roasting section, the soaking section, the first cooling section, and the second cooling section, corresponding blast drying section smoke hood, exhaust section smoke hood, preheating section smoke hood, roasting section smoke hood, soaking section smoke hood, first cooling section smoke hood, and second cooling section smoke hood are respectively provided, and each functional section is separated by a furnace wall; the invention is characterized in that a pair of combustion chambers A and a preheating section heating system A are symmetrically provided on the preheating section smoke hood of the belt roaster, and a pair of combustion chambers B and a roasting section heating system B are symmetrically provided on the roasting section smoke hood of the belt roaster;

[0009] The combustion chamber A and the combustion chamber B are both rectangular parallelepiped combustion chambers, with a slag discharge port and a bin-type pump provided at the bottom of the combustion chamber A, and a temperature sensor A provided at the top of the combustion chamber A;

[0010] The combustion chamber A is connected to both sides of the preheating section smoke hood through a plurality of branch pipes A, and a temperature sensor B is provided on each branch pipe A; the structure of the combustion chamber B is the same as that of the combustion chamber A;

[0011] The preheating section heating system A includes a plasma ignition device A, a blast furnace gas burner A, a plurality of branch pipes A, a cold air duct and a cold air regulating valve. A temperature sensor B is provided on each branch pipe A. The combustion chamber A is connected to both sides of the preheating section smoke hood through a plurality of branch pipes A. The plasma ignition device A is arranged on the left side of the combustion chamber A. Blast furnace gas burners A are provided on both sides of the combustion chamber A. The blast furnace gas burner A is arranged at the lower part of the plasma ignition device A, one end of which is connected to the blast furnace gas pipeline and the other end is connected to the combustion chamber A. A cold air duct and a cold air regulating valve correspond to the lower part of each branch pipe A, and the cold air duct and the cold air regulating valve are connected to the preheating section smoke hood.

[0012] The roasting section heating system B includes a plasma ignition device B, a blast furnace gas burner B, a branch pipe B and a pulverized coal burner, and a temperature sensor C is provided on each branch pipe B; the plasma ignition device B is arranged on the left side of the combustion chamber B, and blast furnace gas burners B and control valves are provided on the left and right sides of the combustion chamber B, and the blast furnace gas burner B is arranged at the lower part of the plasma ignition device B, one end is connected to the blast furnace gas pipeline, and the other end is connected to the combustion chamber B, the pulverized coal burner is arranged inside the branch pipe B, and the pulverized coal burner is connected to the pulverized coal feeder.

[0013] Preferably, a compressed air pulse soot blower is provided at each corner of the combustion chamber A and the combustion chamber B.

[0014] Preferably, a temperature sensor is provided on the top of combustion chamber A and combustion chamber B every three meters.

[0015] Preferably, the combustion chamber A is 30 m long and is provided with eight branch pipes A; the combustion chamber B is 36 m long and is provided with eight branch pipes B; and a pulverized coal feeder is installed on every four branch pipes B.

[0016] The present invention provides a heating method for a pellet belt roaster using blast furnace gas and pulverized coal as fuel, using any one of the pellet belt roaster heating systems of claims 1 to 3, and is characterized by comprising the following steps:

[0017] S1, use plasma ignition device A and plasma ignition device B to ignite the coal powder, so that the combustion chamber

[0018] The temperature in A and combustion chamber B3 reaches 1000℃, ensuring continuous and stable combustion of blast furnace gas + coal powder;

[0019] S2. After ignition and heating, heat is provided by mixed combustion of blast furnace gas and pulverized coal. The mixing ratio of blast furnace gas and pulverized coal is 30%~35% - 70%~65%, so that the temperature of combustion chambers A2 and B3 is controlled at 1000℃~1100℃;

[0020] S3. Adjust the opening of the cold air regulating valve according to the different temperature ranges of the preheating section hood, so that the temperature of the preheating section hood of the belt roaster gradually increases from 400°C to 1100°C from left to right to meet the production process requirements;

[0021] S4. According to the different temperature ranges of the roasting section smoke hood, control the roasting section smoke hood temperature of the belt roaster to gradually increase from 1100 ℃ to 1300 ℃ from left to right to meet the production process requirements.

[0022] Preferably, when the temperature range of the preheating section hood is between 400 and 500°C, the cold air regulating valve is opened by 80%; when the temperature range of the preheating section hood is between 800 and 900°C, the cold air regulating valve is opened by 30%.

[0023] Preferably, the initial temperature of the roasting section is 1100°C~1200°C, at which time the pulverized coal feeder supplies 0.8~1.2 t of coal per hour. The temperature in the later stage of the roasting section is 1200°C~1300°C, and the pulverized coal feeder supplies 1.2~1.6 t of coal per hour. The pulverized coal burner control valve is then adjusted accordingly according to different temperature ranges of the roasting section to control the flue gas temperature of the roasting section to meet the needs of the production process.

[0024] Preferably, the pulverized coal has: ash melting point > 1450°C, volatile matter of 20-25%, particle size of -200 mesh accounting for more than 80%, calorific value > 7000 kcal / kg, ash content < 10%, and moisture < 1%.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention uses a mixture of blast furnace gas and pulverized coal as fuel for the first time, which solves the problem that the belt roaster must use high calorific value gas fuel and breaks through the fuel condition limitation. Blast furnace gas is a by-product gas resource in the blast furnace ironmaking production process of steel plants. Its efficient use can achieve cost reduction and efficiency improvement for steel enterprises, and has very important practical significance for energy conservation and emission reduction in national industrial production.

[0027] (2) The present invention is the first to add a plasma ignition device to the belt roaster heating system, using the plasma ignition device to ignite the pulverized coal, completing the combustion chamber temperature rise process and the subsequent co-burning to play a role in stabilizing combustion.

[0028] (3) The present invention can effectively solve the problem of slag removal difficulties by selecting coal powder with an ash melting point greater than 1450°C, using a plasma ignition device to stabilize combustion, controlling the temperature in the combustion chamber to be lower than 1100°C, and adding an ash blowing system in the combustion chamber.

[0029] (4) The present invention adds a cold air regulating valve and a pulverized coal burner, which can effectively control the temperature of the preheating section and the roasting section and provide precise heat supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a top view of the present invention.

[0031] Figure 2 It is the front view of the present invention.

[0032] Figure 3 For the present invention Figure 1 A-direction side view.

[0033] Figure 4 For the present invention Figure 1 B-direction side view. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings.

[0035] like Figure 1-Figure 4 As shown, a belt roaster heating system using blast furnace gas + pulverized coal as fuel of the present invention comprises a belt roaster, wherein the belt roaster 1 comprises a blast drying section, an exhaust drying section, a preheating section, a roasting section, a soaking section, a first cooling section and a second cooling section; above the blast drying section, the exhaust drying section, the preheating section, the roasting section, the soaking section, the first cooling section and the second cooling section are respectively provided with corresponding blast drying section smoke hood, exhaust section smoke hood, preheating section smoke hood, roasting section smoke hood, soaking section smoke hood, first cooling section smoke hood and second cooling section smoke hood, and each functional section is separated by a furnace wall; it is characterized in that a pair of combustion chambers A2 and a preheating section heating system A are symmetrically arranged on the preheating section smoke hood of the belt roaster, and a pair of combustion chambers B3 and a roasting section heating system B are symmetrically arranged on the roasting section smoke hood of the belt roaster,

[0036] The combustion chamber A2 and the combustion chamber B3 are both rectangular parallelepiped combustion chambers. A slag discharge port 23 and a silo pump 24 are provided at the bottom of the combustion chamber A2. A temperature sensor A5 is provided every three meters on the top of the combustion chamber A2.

[0037] The combustion chamber A2 is connected to both sides of the preheating section hood through a plurality of branch pipes A4, and a temperature sensor B6 is provided on each branch pipe A4; the structure of the combustion chamber B3 is the same as that of the combustion chamber A2;

[0038] The preheating section heating system A includes a plasma ignition device A21, a blast furnace gas burner A22, a plurality of branch pipes A4, a cold air duct and a cold air regulating valve 25. A temperature sensor B6 is provided on each branch pipe A4. The combustion chamber A is connected to both sides of the preheating section smoke hood through the plurality of branch pipes A4. The plasma ignition device A21 is arranged on the left side of the combustion chamber A2. Blast furnace gas burners A22 are provided on both sides of the combustion chamber A2. The blast furnace gas burner A22 is arranged at the lower part of the plasma ignition device A21, one end of which is connected to the blast furnace gas pipeline and the other end is connected to the combustion chamber A2. A cold air duct and a cold air regulating valve 25 are correspondingly provided below each branch pipe A4, and the cold air duct and the cold air regulating valve 25 are connected to the preheating section smoke hood.

[0039] The combustion chamber A2 is 30 m long and is provided with eight branch pipes A4.

[0040] The roasting section heating system B3 includes a plasma ignition device B31, a blast furnace gas burner B32, a branch pipe B8 and a pulverized coal burner 33. A temperature sensor C9 is provided on each branch pipe B8; the plasma ignition device B31 is arranged on the left side of the combustion chamber B3, and blast furnace gas burners B32 and control valves are provided on the left and right sides of the combustion chamber B3, and the blast furnace gas burner B32 is arranged at the lower part of the plasma ignition device B31, one end is connected to the blast furnace gas pipeline, and the other end is connected to the combustion chamber B3, the pulverized coal burner 33 is arranged inside the branch pipe B8, and the pulverized coal burner 33 is connected to the pulverized coal feeder.

[0041] The combustion chamber B3 is 36 m long and is provided with eight branch pipes B8 , and a pulverized coal feeder (not shown in the figure) is installed on every four branch pipes B8 .

[0042] The present invention provides a compressed air pulse soot blower 10 at each corner of the combustion chamber A2 and the combustion chamber B3.

[0043] The plasma ignition device A21 used in this invention is a pulverized coal burner that uses a plasma arc to ignite pulverized coal. The plasma ignition device initially heats the combustion chamber. After the temperature is raised, the plasma ignition device sprays pulverized coal to stabilize the combustion chamber temperature at 1000-1100°C. When the combustion chamber temperature drops, the plasma ignition device is reactivated to stabilize combustion.

[0044] The present invention provides a belt roaster heating method using blast furnace gas + pulverized coal as fuel, which adopts the above pellet belt roaster heating system. The belt roaster adopts an annual output of 4 million tons, 504 m 2The belt roaster has a preheating section length of 36 m and a roasting section length of 30 m. The coal powder has the following characteristics: ash melting point > 1450°C, volatile matter 20-25%, particle size -200 mesh accounting for more than 80%, calorific value > 7000 kcal / kg, ash content < 10%, moisture < 1%;

[0045] The following steps are involved:

[0046] S1, use plasma ignition device A21 and plasma ignition device B31 to ignite coal powder, so that the combustion chamber

[0047] The temperature in A2 and combustion chamber B3 reaches 1000℃, ensuring continuous and stable combustion of blast furnace gas + pulverized coal;

[0048] S2. After ignition and heating, heat is provided by mixed combustion of blast furnace gas and pulverized coal. The mixing ratio of blast furnace gas and pulverized coal is 30%~35% - 70%~65%, so that the temperature of combustion chambers A2 and B3 is controlled at 1000℃~1100℃;

[0049] S3. Adjust the opening of the cold air regulating valve 25 according to the different temperature ranges of the preheating section hood, so that the temperature of the preheating section hood of the belt roaster 1 gradually increases from 400°C to 1100°C from left to right to meet the production process requirements;

[0050] When the preheating section hood temperature range is between 400 and 500°C, the cold air regulating valve is opened 80%; when the preheating section hood temperature range is between 800 and 900°C, the cold air regulating valve is opened 30%;

[0051] S4. According to the different temperature ranges of the roasting section hood, the temperature of the roasting section hood of the belt roaster 1 is controlled to gradually increase from 1100°C to 1300°C from left to right to meet the production process requirements;

[0052] The initial temperature of the roasting section is 1100℃~1200℃. At this time, the pulverized coal supplier supplies 0.8~1.2 t of coal per hour. The temperature of the later stage of the roasting section is 1200℃~1300℃. The pulverized coal burner supplies 1.2~1.6 t of coal per 33 hours. Then, the control valve of the pulverized coal burner 33 is adjusted accordingly according to the different temperature ranges of the roasting section to control the flue gas temperature of the roasting section to meet the needs of the production process.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A pellet belt roaster heating system using blast furnace gas + pulverized coal as fuel, comprising a belt roaster, the belt roaster comprising a blast drying section, an exhaust drying section, a preheating section, a roasting section, a soaking section, a first cooling section, and a second cooling section; above the blast drying section, the exhaust drying section, the preheating section, the roasting section, the soaking section, the first cooling section, and the second cooling section are respectively provided with corresponding blast drying section smoke hoods, exhaust section smoke hoods, preheating section smoke hoods, roasting section smoke hoods, soaking section smoke hoods, first cooling section smoke hoods, and second cooling section smoke hoods, and each functional section is separated by a furnace wall; characterized in that, A pair of combustion chambers A and a preheating section heating system A are symmetrically arranged on the preheating section hood of the belt roaster, and a pair of combustion chambers B and a roasting section heating system B are symmetrically arranged on the roasting section hood of the belt roaster; The combustion chamber A and the combustion chamber B are both rectangular parallelepiped combustion chambers, with a slag discharge port and a bin-type pump provided at the bottom of the combustion chamber A, and a temperature sensor A provided at the top of the combustion chamber A; The combustion chamber A is connected to both sides of the preheating section smoke hood through a plurality of branch pipes A, and a temperature sensor B is provided on each branch pipe A; the structure of the combustion chamber B is the same as that of the combustion chamber A; The preheating section heating system A includes a plasma ignition device A, a blast furnace gas burner A, a plurality of branch pipes A, a cold air duct and a cold air regulating valve. A temperature sensor B is provided on each branch pipe A. The combustion chamber A is connected to both sides of the preheating section smoke hood through a plurality of branch pipes A. The plasma ignition device A is arranged on the left side of the combustion chamber A. Blast furnace gas burners A are provided on both sides of the combustion chamber A. The blast furnace gas burner A is arranged at the lower part of the plasma ignition device A, one end of which is connected to the blast furnace gas pipeline and the other end is connected to the combustion chamber A. A cold air duct and a cold air regulating valve correspond to the lower part of each branch pipe A, and the cold air duct and the cold air regulating valve are connected to the preheating section smoke hood. The roasting section heating system B includes a plasma ignition device B, a blast furnace gas burner B, a branch pipe B, and a pulverized coal burner. A temperature sensor C is provided on each branch pipe B. The plasma ignition device B is provided on the left side of the combustion chamber B. Blast furnace gas burners B and control valves are provided on both the left and right sides of the combustion chamber B. The blast furnace gas burner B is provided below the plasma ignition device B, with one end connected to the blast furnace gas pipe and the other end communicating with the combustion chamber B. The pulverized coal burner is provided inside the branch pipe B and is connected to a pulverized coal feeder. Compressed air pulse soot blowers are installed at each corner of combustion chamber A and combustion chamber B; A temperature sensor is provided every three meters on the top of combustion chamber A and combustion chamber B.

2. The pellet belt roaster heating system using blast furnace gas + pulverized coal as fuel according to claim 1, characterized in that: The combustion chamber A is 30m long and is provided with eight branch pipes A. The combustion chamber B is 36m long and is provided with eight branch pipes B. A pulverized coal feeder is installed on every four branch pipes B.

3. A method for heating a pellet belt roaster using blast furnace gas and pulverized coal as fuel, using any one of the pellet belt roaster heating systems of claims 1-2, characterized in that: The following steps are involved: S1, use plasma ignition device A and plasma ignition device B to ignite the coal powder, so that the combustion chamber The temperature in A and combustion chamber B3 reaches 1000℃, ensuring continuous and stable combustion of blast furnace gas + coal powder; S2. After the ignition and heating is completed, heat is provided by the mixed combustion of blast furnace gas and pulverized coal, with the mixing ratio of blast furnace gas and pulverized coal being 30%~35%-70%~65%, so that the temperature of combustion chambers A (2) and B (3) is controlled at 1000℃~1100℃; S3. Adjust the opening of the cold air regulating valve according to the different temperature ranges of the preheating section hood, so that the temperature of the preheating section hood of the belt roaster gradually increases from 400°C to 1100°C from left to right to meet the production process requirements; S4. According to the different temperature ranges of the roasting section smoke hood, control the roasting section smoke hood temperature of the belt roaster to gradually increase from 1100 ℃ to 1300 ℃ from left to right to meet the production process requirements.

4. A method for supplying heat to a pellet belt roaster using blast furnace gas and pulverized coal as fuel according to claim 3, characterized in that: When the temperature range of the preheating section hood is between 400 and 500 °C, the cold air regulating valve is opened by 80%; when the temperature range of the preheating section hood is between 800 and 900 °C, the cold air regulating valve is opened by 30%.

5. A heating method for a pellet belt roaster using blast furnace gas and pulverized coal as fuel according to claim 3, characterized in that: The initial temperature of the roasting section is 1100℃~1200℃, at which time the pulverized coal feeder supplies 0.8~1.2 t of coal per hour. The temperature in the later stage of the roasting section is 1200℃~1300℃, and the pulverized coal feeder supplies 1.2~1.6 t of coal per hour. The pulverized coal burner control valve is then adjusted accordingly according to the different temperature ranges of the roasting section to control the flue gas temperature of the roasting section to meet the needs of the production process.

6. The method for supplying heat to a pellet belt roaster using blast furnace gas and pulverized coal as fuel according to claim 3, characterized in that: The pulverized coal has: ash melting point>1450°C, volatile matter of 20-25%, particle size of -200 mesh accounting for more than 80%, calorific value>7000 kcal / kg, ash content<10%, and moisture content<1%.

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