A belt calciner pellet production system using low-calorific-value coal gas.

Abstract

This invention discloses a belt calciner pellet production system using low-calorific-value coal gas, relating to the field of pellet production technology. It solves the technical problem in related technologies that low-calorific-value coal gas cannot be directly injected and burned within the pellet calciner to generate sufficient heat and temperature for pellet roasting. The system includes a belt calciner, a hot blast stove, a gas heat exchanger, and a combustion air heat exchanger. The high-temperature zone of the belt calciner is equipped with several oxygen-enriched burners. The hot blast stove is connected to several hot air nozzles that transport high-temperature flue gas to the preheating and roasting zones of the belt calciner. The gas heat exchanger preheats the low-calorific-value coal gas to 200-300°C, and the combustion air heat exchanger preheats the combustion air to 500-600°C. This system fully utilizes the high-yield, low-calorific-value coal gas for pellet production by leveraging the hot blast stove, compensating for the insufficient heat generated by the combustion of low-calorific-value coal gas and saving on the consumption of high-calorific-value coal gases such as coke oven gas.

Description

Technical Field

[0001] This invention relates to the field of pellet production technology, and in particular to a belt roaster pellet production system using low-calorific-value coal gas roasting. Background Technology

[0002] Iron ore pellets are a type of artificial ore. They are made by using fine-grained iron ore powder to form pellets through a pelletizing device. The pellets are then subjected to a series of processes, including drying, preheating, roasting, homogenization, and cooling, through a belt roaster, in order to produce raw materials that meet the needs of blast furnaces, shaft furnaces, and other metallurgical equipment.

[0003] In existing belt roasting pelletizing processes, high-calorific-value gaseous fuels such as natural gas and coke oven gas are used as heat sources. Combustion of these high-calorific-value gases produces high-temperature flue gas, which is used to dry, preheat, and roast the pellets. Depending on the type and properties of the iron ore powder, the maximum roasting temperature can reach 1250–1340℃ or even higher. Generally, low-calorific-value gases such as blast furnace gas and converter gas cannot meet the required fuel calorific value and cannot achieve high-temperature roasting. Therefore, the reliance on high-calorific-value natural gas or coke oven gas is the most significant drawback of belt roasting pelletizing processes. Summary of the Invention

[0004] This application provides a belt roaster pellet production system using low-calorific-value coal gas, which solves the technical problem in related technologies that low-calorific-value coal gas cannot be directly injected and burned in the pellet roaster to generate sufficient heat and temperature to roast the pellets.

[0005] This application provides a belt calciner pellet production system using low-calorific-value coal gas, comprising a belt calciner, a hot air furnace, a gas heat exchanger, and a combustion air heat exchanger. The belt calciner has several hot exhaust gas outlets, and several oxygen-enriched burners are installed in the high-temperature zone of the belt calciner. The hot air furnace is connected to several hot air nozzles that transport high-temperature flue gas to the preheating and calcining zones of the belt calciner. The gas heat exchanger is connected to a third pipeline, a first gas pipeline, and a second gas pipeline. The third pipeline is connected to the belt calciner at at least one hot exhaust gas outlet. The first gas pipeline supplies low-calorific-value coal gas to the gas heat exchanger, which preheats the low-calorific-value coal gas to 200-300°C. The gas heat exchanger is connected to the hot air... The furnace input end is connected to all oxygen-enriched burners via a second gas pipeline. The combustion air heat exchanger is connected to the second pipeline, the first air pipeline, the second air pipeline, and the third air pipeline. The second pipeline is connected to the belt roaster at at least one hot exhaust gas outlet. The first air pipeline supplies combustion air to the combustion air heat exchanger, which preheats the combustion air to 500-600°C. The end of the second air pipeline away from the combustion air heat exchanger is connected to the hot air furnace. The third air pipeline is connected to the oxygen pipeline and several oxygen-enriched air branch pipes. The oxygen pipeline is located before the oxygen-enriched air branch pipes along the airflow direction. The end of the oxygen-enriched air branch pipes away from the third air pipeline is connected to each of the oxygen-enriched burners.

[0006] Optionally, the hot air furnace is connected to hot air nozzles that convey high-temperature flue gas to the preheating zone and the roasting zone of the belt roaster, including:

[0007] The hot air duct is connected at one end to the output end of the hot air furnace.

[0008] The main hot air duct connects to the end of the hot air pipe furthest from the hot air furnace, and is positioned above the hood of the belt roaster; and

[0009] Several hot air branch pipes are connected at one end to the hot air main pipe. The hot air branch pipes are arranged on both sides of the hot air main pipe. The end of the hot air branch pipe away from the hot air main pipe is connected to the hot air nozzle.

[0010] Optionally, the belt calciner includes, in sequence according to the material flow direction, a blower drying zone, an exhaust drying zone, a preheating stage 1, a preheating stage 2, a calcining stage 1, a calcining stage 2, a homogenizing zone, a cooling stage 1, and a cooling stage 2. The exhaust gas temperature of the preheating stage 1 is below 300℃, the exhaust gas temperature of the preheating stage 2 is 300-400℃, the exhaust gas temperature of the calcining stage 1 is 400-500℃, the exhaust gas temperature of the calcining stage 2 is 500-700℃, and the exhaust gas temperature of the homogenizing zone is 600-700℃.

[0011] The hot exhaust gas from the second preheating stage and the hot exhaust gas from the first calcination stage are transported to the third pipeline, which is equipped with a third fan.

[0012] The hot exhaust gas from the second roasting stage and the hot exhaust gas from the homogenization zone are transported to the second pipeline, which is equipped with a second fan.

[0013] The hot air furnace is connected to several hot air nozzles that transport high-temperature flue gas to the preheating zone and the roasting zone of the belt roaster. The preheating zone includes a first preheating section and a second preheating section, and the roasting zone includes a first roasting section and a second roasting section.

[0014] Optionally, the hot exhaust gas output end of the combustion air heat exchanger is connected to the exhaust drying zone.

[0015] Optionally, the temperature of the hot exhaust gas in the second cooling stage is 200-350℃. The hot exhaust gas in the second cooling stage enters the blower drying zone through the first pipe. The first pipe is equipped with a fifth fan. The blower drying zone is also connected to a sixth fan that draws out the hot exhaust gas.

[0016] Optionally, the temperature of the hot exhaust gas in the cooling section is 900-1000℃, and the hot exhaust gas in the cooling section is transported to the hot air nozzle through the fourth pipe and to the heat equalization zone through the fifth pipe.

[0017] Optionally, the hot exhaust gas from the exhaust drying zone and the hot exhaust gas from the preheating stage are transported to the chimney via a fourth fan.

[0018] Optionally, the hot air nozzle is made of a refractory material with excellent high temperature resistance and thermal shock resistance, and the hot air nozzle is fixedly connected to the machine cover.

[0019] Optionally, the gas heat exchanger is connected to all oxygen-enriched burners via a second gas pipeline, including:

[0020] The second gas pipeline is connected to several gas branch pipes. The second gas pipeline is equipped with a tenth blower. The end of the gas branch pipe away from the second gas pipeline is connected to an oxygen-enriched burner.

[0021] Optionally, the second gas pipeline, the second air pipeline, the third air pipeline, the second pipeline, the oxygen-enriched air branch pipe, the hot air branch pipe, and the gas branch pipe are all equipped with gas regulating valves.

[0022] The beneficial effects of this application are as follows: This application provides a belt calciner pellet production system using low-calorific-value coal gas. Part of the waste gas from the belt calciner is used as a heat source for a gas heat exchanger, which preheats the low-calorific-value coal gas to 200-300℃. The preheated low-calorific-value coal gas is then transported to the hot blast stove and the oxygen-enriched burner. Part of the waste gas from the belt calciner is also used as a heat source for a combustion air heat exchanger, which preheats the combustion air input from the first air pipe to 500-600℃. The preheated combustion air is then transported to the hot blast stove and the oxygen-enriched burner, respectively. The independent hot blast stove... The low-calorific-value coal gas, after combustion and preheating, forms high-temperature flue gas at 1000-1100℃. This high-temperature flue gas is transported to the preheating and roasting zones of the belt roaster through hot air nozzles. The system also generates high-temperature flue gas through oxygen-enriched combustion at the oxygen-enriched burner. This mixed flue gas, which is mixed with the high-temperature flue gas at the hot air nozzles, has a temperature of 1250-1350℃, meeting the temperature requirements of the preheating and roasting zones. In summary, this system makes full use of the high-yield, low-calorific-value coal gas in the hot air furnace for pellet production, compensating for the problem of insufficient heat generation from the combustion of low-calorific-value coal gas and saving the consumption of high-calorific-value coal gas such as coke oven gas. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention.

[0024] Figure 1 A schematic diagram of the arrangement structure of the belt roaster burner in a belt roaster pellet production system using low-calorific-value coal gas provided in this application.

[0025] Figure 2 A process diagram of a belt roaster pellet production system using low-calorific-value gas for this application.

[0026] Attached diagram labels: 1-Hot air furnace, 2-Hot air duct, 3-Hot air main duct, 4-Hot air branch duct, 5-Hot air nozzle, 6-Oxygen-enriched burner, 7-Machine hood, 8-Belt roaster, 801-Blow-air drying zone, 802-Exhaust-air drying zone, 803-Preheating stage 1, 804-Preheating stage 2, 805-Roasting stage 1, 806-Roasting stage 2, 807-Soaking zone, 808-Cooling stage 1, 809-Cooling stage 2, 9-Blower box, 10-Fan, 1001-First fan, 1002-Second fan, 1003-Third fan, 1004-Fourth fan, 1005-Fifth fan, 1006-Sixth fan Machine, 1007-Seventh Fan, 1008-Eighth Fan, 1009-Ninth Fan, 1010-Tenth Fan, 1011-Eleventh Fan, 1012-Twelfth Fan, 11-Gas Heat Exchanger, 12-Air Heat Exchanger, 13-Gas Regulating Valve, L1-First Pipeline, L2-Second Pipeline, L3-Third Pipeline, L4-First Gas Pipeline, L5-Second Gas Pipeline, L6-First Air Pipeline, L7-Second Air Pipeline, L8-Third Air Pipeline, L9-Oxygen Pipeline, L10-Oxygen-Enriched Air Branch Pipe, L11-Gas Branch Pipe, L12-Fourth Pipeline, L13-Fifth Pipeline. Detailed Implementation

[0027] This application provides a belt roaster pellet production system using low-calorific-value coal gas, which solves the technical problem in related technologies that low-calorific-value coal gas cannot be directly injected and burned in the pellet roaster to generate sufficient heat and temperature to roast the pellets.

[0028] The technical solution in this application is to solve the above-mentioned technical problems, and the general idea is as follows:

[0029] A belt calciner pellet production system using low-calorific-value coal gas includes a belt calciner, a hot air furnace, a gas heat exchanger, and a combustion air heat exchanger. The belt calciner has several hot exhaust gas outlets. Several oxygen-enriched burners are installed in the high-temperature zone of the belt calciner. The hot air furnace is connected to several hot air nozzles that transport high-temperature flue gas to the preheating and calcining zones of the belt calciner. The gas heat exchanger is connected to a third pipeline, a first gas pipeline, and a second gas pipeline. The third pipeline is connected to the belt calciner at at least one hot exhaust gas outlet. The first gas pipeline supplies low-calorific-value coal gas to the gas heat exchanger, which preheats the low-calorific-value coal gas to 200-300°C. The gas heat exchanger is connected to the hot air furnace via pipelines. The input end is connected to all oxygen-enriched burners via a second gas pipeline. The combustion air heat exchanger is connected to the second pipeline, the first air pipeline, the second air pipeline, and the third air pipeline. The second pipeline is connected to the belt roaster at at least one hot exhaust gas outlet. The first air pipeline supplies combustion air to the combustion air heat exchanger, which preheats the combustion air to 500-600°C. The end of the second air pipeline away from the combustion air heat exchanger is connected to the hot air furnace. The third air pipeline is connected to the oxygen pipeline and several oxygen-enriched air branch pipes. The oxygen pipeline is located before the oxygen-enriched air branch pipes along the airflow direction. The end of the oxygen-enriched air branch pipes away from the third air pipeline is connected to each of the oxygen-enriched burners.

[0030] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0031] Please refer to Figure 2 This embodiment provides a pellet production system using a belt roaster 8 with low-calorific-value coal gas roasting, including a belt roaster 8, a hot air furnace 1, a coal gas heat exchanger 11, and a combustion air heat exchanger 12.

[0032] In this system, please refer to Figure 2 The belt roaster 8 has several hot exhaust gas outlets, which enable the reuse of hot exhaust gas at specific locations. The high-temperature zone of the belt roaster 8 is equipped with several oxygen-enriched burners 6, including a preheating zone and a roasting zone, to achieve oxygen-enriched combustion and increase the gas temperature.

[0033] In this system, please refer to Figure 2 The hot air furnace 1 is connected to several hot air nozzles 5, through which high-temperature flue gas is transported to the preheating zone and roasting zone of the belt roaster 8.

[0034] In this system, please refer to Figure 2The gas heat exchanger 11 is connected to the third pipe L3, the first gas pipe L4, and the second gas pipe L5. The third pipe L3 is connected to the belt roaster 8 at at least one hot exhaust gas outlet. The first gas pipe L4 supplies low-calorific-value gas to the gas heat exchanger 11, which preheats the low-calorific-value gas to 200-300°C. The gas heat exchanger 11 is connected to the input end of the hot air furnace 1 through a pipe, and the gas heat exchanger 11 is connected to all the oxygen-enriched burners 6 through the second gas pipe L5.

[0035] In this system, please refer to Figure 2 The combustion air heat exchanger 12 is connected to the second pipe L2, the first air pipe L6, the second air pipe L7, and the third air pipe L8. The second pipe L2 is connected to the belt roaster 8 at at least one hot exhaust gas outlet. The first air pipe L6 supplies combustion air to the combustion air heat exchanger 12, which preheats the combustion air to 500-600°C. The end of the second air pipe L7 away from the combustion air heat exchanger 12 is connected to the hot air furnace 1. The third air pipe L8 is connected to the oxygen pipe L9 and several oxygen-enriched air branch pipes L10. The oxygen pipe L9 is positioned in front of the oxygen-enriched air branch pipes L10 along the airflow direction. The end of the oxygen-enriched air branch pipes L10 away from the third air pipe L8 is connected to the oxygen-enriched burners 6 one by one.

[0036] In the above-described belt calciner 8 pellet production system, a portion of the hot waste gas from the belt calciner 8 is used as a heat source for the gas heat exchanger 11. The gas heat exchanger 11 preheats the low-calorific-value gas to 200-300℃, and the preheated low-calorific-value gas is then transported to the hot blast stove 1 and the oxygen-enriched burner 6. A portion of the hot waste gas from the belt calciner 8 is also used as a heat source for the combustion air heat exchanger 12. The combustion air heat exchanger 12 preheats the combustion air input from the first air pipe L6 to 500-600℃, and the preheated combustion air is then transported to the hot blast stove 1 and the oxygen-enriched burner 6, respectively. In the independent hot blast stove 1, the preheated low-calorific-value gas is combusted to form high-temperature flue gas at 1000-1100℃. This high-temperature flue gas is then transported to the preheating zone and calcination zone of the belt calciner 8 through the hot air nozzle 5. This system also generates high-temperature flue gas through oxygen-enriched combustion at the oxygen-enriched burner 6, which mixes with the high-temperature flue gas at the hot air nozzle 5 to form a mixed flue gas with a temperature of 1250-1350℃, meeting the temperature requirements of the preheating zone and the calcination zone.

[0037] In summary, this system utilizes hot blast stove 1 to fully leverage low-calorific-value coal gas with high output and low calorific value for pellet production, thus compensating for the problem of insufficient heat generation from combustion of low-calorific-value coal gas and saving on the consumption of high-calorific-value coal gas such as coke oven gas.

[0038] Please refer to Figure 1 and Figure 2The aforementioned hot air furnace 1 is connected to hot air nozzles 5 that transport high-temperature flue gas to the preheating and roasting zones of the belt roaster 8. In some feasible embodiments, it includes a hot air duct 2, a hot air main duct 3, and several hot air branch pipes 4. One end of the hot air duct 2 is connected to the output end of the hot air furnace 1, and the hot air main duct 3 is connected to the end of the hot air duct 2 away from the hot air furnace 1. The hot air main duct 3 is located above the machine cover 7 of the belt roaster 8. One end of each of the several hot air branch pipes 4 is connected to the hot air main duct 3, and the hot air branch pipes 4 are respectively arranged on both sides of the hot air main duct 3. The ends of the hot air branch pipes 4 away from the hot air main duct 3 are connected to the hot air nozzles 5 one by one. The hot air branch pipes 4 enter the space above the machine cover 7 and the belt roaster 8 through the hot air nozzles 5, supplying the heat of the high-temperature hot air to the pellets on the belt roaster 8 to heat the pellets and meet the process requirements of pellet drying, preheating, and roasting.

[0039] The hot air nozzle 5 can be made of refractory material with excellent high temperature resistance and thermal shock resistance. The hot air nozzle 5 is fixedly connected to the cover 7 as one piece, which is convenient for maintenance and repair.

[0040] Please refer to Figure 1 and Figure 2 In some feasible implementations, several hot air branch pipes 4 are symmetrically or alternately arranged on the left and right sides of the machine cover 7.

[0041] Please refer to Figure 1 The flue gas passing through the belt roaster 8 is discharged from the hood 7 by the blower 10 through the blower box 9, and can be used as low-temperature flue gas for recycling.

[0042] Generally speaking, the belt roaster 8 needs to carry out a series of processes such as drying, preheating, roasting, homogenization and cooling. Along the material flow direction, it includes the blower drying zone 801, the exhaust drying zone 802, the preheating zone, the roasting zone, the homogenization zone and the cooling zone arranged in sequence.

[0043] For some possible implementations of this embodiment, please refer to Figure 2 The preheating zone includes a first preheating stage 803 and a second preheating stage 804; the roasting zone includes a first roasting stage 805 and a second roasting stage 806; and the cooling zone includes a first cooling stage 808 and a second cooling stage 809. Specifically, the belt roaster 8, in the order of material flow direction, includes a forced-air drying zone 801, a forced-air drying zone 802, a first preheating stage 803, a second preheating stage 804, a first roasting stage 805, a second roasting stage 806, a homogenization zone, a first cooling stage 808, and a second cooling stage 809. The relevant limitations are: the exhaust gas temperature of the first preheating stage 803 is below 300℃; the exhaust gas temperature of the second preheating stage 804 is between 300-400℃; the exhaust gas temperature of the first roasting stage 805 is between 400-500℃; the exhaust gas temperature of the second roasting stage 806 is between 500-700℃; and the exhaust gas temperature of the homogenization zone is between 600-700℃.

[0044] Please refer to Figure 2 The hot exhaust gas from the preheating stage 804 and the hot exhaust gas from the calcination stage 805 are transported to the third pipeline L3. The third pipeline L3 is equipped with a third fan 1003 to smoothly transport the hot exhaust gas from the preheating stage 804 and the calcination stage 805 to the gas heat exchanger 11. The hot exhaust gas from the preheating stage 804 and the calcination stage 805 mix to form hot exhaust gas at approximately 400°C, further increasing it to 400-450°C. This preheats the low-calorific-value gas from approximately 25°C to above 200-300°C, including 300-400°C. Preheating the gas to above 200-300°C significantly increases the combustion temperature. The gas heat exchanger 11 can be a separate heat pipe heat exchanger or a metal tube heat exchanger.

[0045] Please refer to Figure 2 The hot exhaust gas from the second calcination stage 806 and the hot exhaust gas from the homogenization zone are transported to the second pipeline L2. The second pipeline L2 is equipped with a second fan 1002 to transport the hot exhaust gas from the second calcination stage 806 and the hot exhaust gas from the homogenization zone to the combustion air heat exchanger 12, so as to heat the combustion air from about 25°C to 500-600°C and achieve preheating of the combustion air.

[0046] Alternatively, see Figure 2 The hot exhaust gas output end of the combustion air heat exchanger 12 is connected to the exhaust drying zone 802. Specifically, the temperature of the hot exhaust gas from the second calcination stage 806 and the hot exhaust gas from the heat homogenization stage 807 after mixing far exceeds the temperature requirement of the exhaust drying zone 802. Therefore, the solution is to reduce the temperature of this part of the hot exhaust gas to about 350°C after passing through the combustion air heat exchanger 12 and then deliver it to the exhaust drying zone 802.

[0047] Alternatively, see Figure 2 The temperature of the pellets in the second cooling section 809 is about 400℃, and the temperature of the hot exhaust gas after being cooled by the blower is about 200-350℃. The first pipe L1 is equipped with the fifth fan 1005. The hot exhaust gas from the second cooling section 809 enters the blower drying zone 801 through the first pipe L1 under the blowing action of the fifth fan 1005.

[0048] Alternatively, see Figure 2 The blower drying zone 801 is also connected to a sixth fan 1006 that draws out hot exhaust gas. After drying in the blower drying zone 801, the exhaust gas is drawn out by the sixth fan 1006 and discharged into the atmosphere.

[0049] The roasting zone has a high heat requirement. In addition to supplementing the heat through the high-temperature flue gas and oxygen-enriched combustion of the hot blast furnace 1, the heat can also optionally be supplemented by the hot exhaust gas from the cooling section 808. Specifically, the temperature of the pellets entering the cooling section 808 is approximately 1100℃, and the temperature of the hot exhaust gas discharged from the cooling section 808 is 900-1000℃. Regarding the hot exhaust gas from the cooling section 808, part of it is transported to the hot air nozzle 5 through the fourth pipe L12. Specifically, the fourth pipe L12 can be connected to the hot air main pipe 3, and transported along the hot air main pipe 3 and the hot air branch pipe 4 to the hot air nozzle 5, which supplements the heat of the preheating zone and the roasting zone. Part of it is transported to the homogenization zone through the fifth pipe L13, where it is roasted and solidified by the heat of the upper pellets themselves.

[0050] Optionally, the hot exhaust gas from the exhaust drying zone 802 and the hot exhaust gas from the preheating section 803 are transported to the chimney via the fourth fan 1004 and then discharged into the atmosphere.

[0051] The aforementioned gas heat exchanger 11 is connected to all oxygen-enriched burners 6 via a second gas pipeline L5. Optionally, such as... Figure 2 As shown, the second gas pipeline L5 is connected to several gas branch pipes L11. The second gas pipeline L5 is equipped with a tenth blower 1010. The end of the gas branch pipe L11 away from the second gas pipeline L5 is connected to the oxygen-enriched burner 6. The preheated low-calorific-value gas is transported to the oxygen-enriched burner 6 along the second gas pipeline L5 and the gas branch pipes L11.

[0052] Alternatively, please refer to Figure 2 A first fan 1001 is installed at the air inlet of the first cooling section 808 and the second cooling section 809.

[0053] Alternatively, please refer to Figure 2 The exhaust port of the gas heat exchanger 11 is equipped with a seventh fan 1007 to draw the exhaust gas into the atmosphere.

[0054] The aforementioned gas heat exchanger 11 is connected to the input end of the hot air furnace 1 via a pipeline, and the gas heat exchanger 11 is connected to all the oxygen-enriched burners 6 via the second gas pipeline L5. Optionally, please refer to... Figure 2 An eighth fan 1008 can be installed at the gas outlet of the gas heat exchanger 11 to smoothly transport the preheated low-calorific-value gas to the hot blast stove 1 and the oxygen-enriched burner 6.

[0055] Alternatively, please refer to Figure 2 The second air duct L7 is equipped with the ninth fan 1009, which successfully delivers the preheated combustion air to the hot blast stove 1.

[0056] Alternatively, please refer to Figure 2The hot air duct 2 is equipped with an eleventh fan 1011 to transport the high-temperature flue gas of 1000-1100℃ generated by the hot air furnace 1 to the hot air nozzle 5 along the hot air duct 2.

[0057] Alternatively, see Figure 2 The first air duct L6 is equipped with the twelfth fan 1012 to smoothly deliver the combustion air to the combustion air heat exchanger 12.

[0058] Optionally, gas regulating valves 13 are installed in the second gas pipeline L5, the second air pipeline L7, the third air pipeline L8, the second pipeline L2, the oxygen-enriched air branch pipe L10, the hot air branch pipe 4, and the gas branch pipe L11. The gas regulating valves 13 are used to precisely control the temperature and heat in different areas of the belt roaster 8, including but not limited to:

[0059] Most of the preheated low-calorific-value gas is transported to the hot blast stove 1 through the gas regulating valve 13 on the second gas pipeline L5, and a small portion is diverted to the second gas pipeline L5.

[0060] The preheated combustion air is distributed through the gas regulating valve 13 on the second air duct L7 and the gas regulating valve 13 on the third air duct L8.

[0061] The amount of high-temperature flue gas introduced into different areas of the belt roaster 8 is controlled by the gas regulating valve 13 on the hot air branch pipe 4.

[0062] The amount of oxygen-enriched air supplied to the oxygen-enriched burners 6 at different locations in the belt roaster 8 is controlled by the gas regulating valve 13 on the oxygen-enriched air branch pipe L10, thereby controlling the different temperature requirements of the preheating zone and the roasting zone.

[0063] The amount of gas supplied to the oxygen-enriched burners 6 at different locations is controlled by the gas regulating valve 13 on the gas branch pipe L11.

[0064] The above description includes temperature control in different sections of the belt roaster 8, involving the regulation of low-calorific-value gas volume, combustion air volume, and hot exhaust gas volume. For further explanation, this embodiment also provides a gas regulation and control method, including but not limited to the following steps:

[0065] Pellet temperature detection devices are installed at the beginning of the preheating zone and the end of the roasting zone to detect the pellet temperature value T1 at the beginning of the preheating zone and the temperature value T2 at the end of the roasting zone in real time.

[0066] The temperature and flow rate of the high-temperature flue gas entering the preheating zone and the roasting zone of the hot blast stove 1, the temperature and flow rate of the low-calorific-value coal gas and oxygen-enriched combustion air injected into the oxygen-enriched burner 6, and the temperature and flow rate of the hot exhaust gas entering the preheating zone and the roasting zone from the cooling section 808 are monitored in real time.

[0067] The flow rate and temperature of the flue gas extracted by the third fan 1003 and the fourth fan 1004 are monitored, and the flow rate of the air blown in by the first fan 1001 is also monitored.

[0068] The heat absorbed by the pellets, Q_pellet, is equal to the total heat input from the hot blast stove 1, the oxygen-enriched burner 6, and the 808 cooling section of the hot waste gas. Specifically, it is the difference between Q_heat supplied and Q_heat discharged from the hot waste gas extracted through the third fan 1003 and the fourth fan 1004, i.e., Q_pellet = Q_heat supplied - Q_heat discharged.

[0069] Simultaneously, the total amount of hot air input into the preheating and roasting zones from the hot blast stove 1, oxygen-enriched burner 6, and cooling section 808 is monitored and calculated to determine the theoretical combustion temperature T3 that the flue gas can reach, ensuring that the temperature reaches approximately 1260℃ (limited to the range of 1250-1350℃) to meet the pellet roasting requirements. The calculation formula is: T3 = Q_heating / (C_hot_air × V_hot_air), where C_hot_air is the specific heat capacity of the mixed hot air from the hot blast stove 1, oxygen-enriched burner 6, and cooling section 808, which can be calculated through gas composition monitoring; V_hot_air is the volume of mixed gas entering the preheating and roasting sections per unit time.

[0070] Based on Q pellet = Q heat supply - Q heat discharge, the total heat supply Q heat supply is calculated. The relevant gas regulating valve 13 is adjusted to control the flue gas volume and coal gas volume. At the same time, the amount of waste gas entering the blower drying zone 801 from the second cooling stage 809 is adjusted to control the amount of waste gas entering the roasting zone and preheating zone from the first cooling stage 808.

[0071] The highest temperature T3 of the mixed flue gas in the roasting zone is calculated based on T3 = Q_heat supply / (C_hot air × V_hot air). This temperature is then compared with the data from the temperature detection device to guide the oxygen enrichment rate of the combustion air and the amount of gas.

[0072] In summary, the belt roaster pellet production system using low-calorific-value gas provided in this embodiment has at least the following beneficial effects:

[0073] 1) By using hot blast stove 1, the low-calorific-value gas with large output and low calorific value can be fully utilized to make up for the problem of insufficient heat generated by the combustion of low-calorific-value gas and save the consumption of high-calorific-value gas such as coke oven gas.

[0074] 2) Based on the heat demand of different areas in the preheating zone and roasting zone, the hot air can be intelligently and precisely sprayed onto different sections through the hot air nozzles 5 using dedicated hot air pipes 2, to meet the temperature control requirements and ensure uniform distribution.

[0075] 3) Preheated blast furnace gas and oxygen-enriched combustion air can be used for combustion, which not only increases the local roasting temperature and provides precise and targeted heat replenishment to meet the high-temperature requirements of roasting sections and other areas, but also reduces the excess air coefficient, effectively reducing NOx generation and emissions.

[0076] 4) The physical sensible heat in the hot exhaust gas of the roasting machine is comprehensively utilized. Before entering the hot air furnace 1 and the oxygen-enriched burner 6, the combustion air is preheated at high temperature and the low-calorific-value gas is preheated at low temperature, which significantly increases the temperature of the high-temperature flue gas after the gas is burned, thereby avoiding heat waste, realizing effective energy recovery, and being conducive to carbon saving and environmental protection in the process.

[0077] 5) Significantly improves energy utilization, achieves ultra-low emissions of flue gas in the pellet production process, has a compact process flow, highly efficient and intensive equipment, and a high level of automation, and has good application prospects.

[0078] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0079] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A belt calciner pellet production system using low-calorific-value coal gas, characterized in that, The belt calciner pellet production system includes: A belt roaster has several hot exhaust gas outlets, and several oxygen-enriched burners are installed in the high-temperature zone of the belt roaster. A hot air furnace is connected to several hot air nozzles that transport high-temperature flue gas to the preheating zone and the roasting zone of the belt roaster. A gas heat exchanger is connected to a third pipeline, a first gas pipeline, and a second gas pipeline. The third pipeline is connected to the belt roaster at at least one of the hot exhaust gas outlets. The first gas pipeline supplies low-calorific-value gas to the gas heat exchanger, which preheats the low-calorific-value gas to 200-300°C. The gas heat exchanger is connected to the input end of the hot air furnace via a pipeline and to all the oxygen-enriched burners via the second gas pipeline. A combustion air heat exchanger is connected to a second pipe, a first air pipe, and a third air pipe. The second pipe is connected to the belt roaster at at least one of the hot exhaust gas outlets. The first air pipe supplies combustion air to the combustion air heat exchanger, which preheats the combustion air to 500-600°C. The end of the second air pipe away from the combustion air heat exchanger is connected to the hot air furnace. The third air pipe is connected to an oxygen pipe and several oxygen-enriched air branch pipes. The oxygen pipe is positioned before the oxygen-enriched air branch pipes along the airflow direction. The end of the oxygen-enriched air branch pipes away from the third air pipe is connected to an oxygen-enriched burner. The belt calciner, arranged sequentially according to the material flow direction, includes a forced-air drying zone, a forced-air drying zone, a preheating stage 1, a preheating stage 2, a calcining stage 1, a calcining stage 2, a homogenizing zone, a cooling stage 1, and a cooling stage 2. The exhaust gas temperature in the preheating stage 1 is below 300℃, the exhaust gas temperature in the preheating stage 2 is between 300-400℃, the exhaust gas temperature in the calcining stage 1 is between 400-500℃, the exhaust gas temperature in the calcining stage 2 is between 500-700℃, and the exhaust gas temperature in the homogenizing zone is between 600-700℃. The hot exhaust gas from the preheating stage and the hot exhaust gas from the calcination stage are transported to the third pipeline, which is equipped with a third fan. The hot exhaust gas from the calcination stage and the hot exhaust gas from the homogenization zone are transported to the second pipeline, which is equipped with a second fan. The hot air furnace is connected to several hot air nozzles that transport high-temperature flue gas to the preheating zone and the calcination zone of the belt calciner. The preheating zone includes the first preheating stage and the second preheating stage, and the calcination zone includes the first calcination stage and the second calcination stage. The temperature of the hot exhaust gas in the second cooling stage is 200-350℃. The hot exhaust gas in the second cooling stage enters the blower drying zone through the first pipe. The first pipe is equipped with a fifth fan. The blower drying zone is also connected to a sixth fan to draw out the hot exhaust gas. The temperature of the hot exhaust gas in the cooling section is 900-1000℃. The hot exhaust gas in the cooling section is transported to the hot air nozzle through the fourth pipe and to the heat equalization zone through the fifth pipe.

2. The belt calciner pellet production system as described in claim 1, characterized in that, The hot air furnace is connected to hot air nozzles that transport high-temperature flue gas to the preheating zone and the roasting zone of the belt roaster, including: A hot air duct, one end of which is connected to the output end of the hot air furnace; A main hot air duct is connected to the end of the hot air pipe furthest from the hot air furnace, and the main hot air duct is positioned above the hood of the belt roaster; and Several hot air branch pipes are connected at one end to the hot air main pipe. The hot air branch pipes are respectively arranged on both sides of the hot air main pipe. The end of the hot air branch pipe away from the hot air main pipe is connected to the hot air nozzle.

3. The belt calciner pellet production system as described in claim 1, characterized in that, The hot exhaust gas output end of the combustion air heat exchanger is connected to the exhaust drying zone.

4. The belt calciner pellet production system as described in claim 1, characterized in that, The hot exhaust gas from the exhaust drying zone and the hot exhaust gas from the preheating section are transported to the chimney by the fourth fan.

5. The belt calciner pellet production system as described in claim 2, characterized in that, The hot air nozzle is made of a refractory material with excellent high temperature resistance and thermal shock resistance, and the hot air nozzle is fixedly connected to the machine cover.

6. The belt calciner pellet production system as described in claim 2, characterized in that, The gas heat exchanger is connected to all the oxygen-enriched burners via the second gas pipeline, including: The second gas pipeline is connected to several gas branch pipes, and a tenth blower is installed on the second gas pipeline. The end of each gas branch pipe away from the second gas pipeline is connected to the oxygen-enriched burner.

7. The belt calciner pellet production system as described in claim 6, characterized in that, The second gas pipeline, the second air pipeline, the third air pipeline, the second pipeline, the oxygen-enriched air branch pipe, the hot air branch pipe, and the gas branch pipe are all equipped with gas regulating valves.

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