An ultra-low emission low calorific value gas heating furnace

Abstract

The present invention belongs to the technical field of industrial furnaces and environmental protection in the metallurgical industry, and specifically relates to a low-calorific-value gas heating furnace with ultra-low emissions. A number of low-calorific-value gas burner units are provided in the heating zone of the furnace body. The low-calorific-value gas burner unit includes a gas nozzle and an air regenerative heat storage nozzle. The gas supply unit includes a gas-flue gas heat exchange preheater and a gas transmission pipeline. The gas-flue gas heat exchange preheater is respectively connected to each gas nozzle through the gas transmission pipeline. The air supply unit includes an air transmission pipeline, and the air transmission pipeline is respectively connected to each air regenerative heat storage nozzle. The flue gas emission unit includes an empty flue gas emission pipeline, a furnace tail flue gas emission pipeline, and a flue gas environmental protection treatment component. The empty flue gas emission pipeline is connected to each air regenerative heat storage nozzle. After the empty flue gas emission pipeline and the furnace tail flue gas emission pipeline converge, they are connected to the gas-flue gas heat exchange preheater. The present invention adopts low-calorific-value gas preheating and air regenerative heat storage technologies to reduce harmful gases in the flue gas emissions of the heating furnace.

Description

Technical Field

[0001] The invention belongs to the field of industrial furnaces and environmental protection technology in the metallurgical industry, and specifically relates to an ultra-low emission low calorific value coal gas heating furnace. Background Art

[0002] Traditional long-process steel enterprises in the metallurgical industry generally use low calorific value gas as industrial furnace fuel. Taking blast furnace gas as an example, when it is the only fuel, air-gas dual heat storage technology is generally used to meet the production temperature of the steel rolling heating furnace. According to its own characteristics, the heating furnace using air-gas dual heat storage generally has the following characteristics: (1) O is discharged from the air heat storage chamber and the gas heat storage chamber respectively. 2 The flue gas with higher CO content and the flue gas with higher CO content cannot be mixed for safety reasons. Two sets of exhaust systems are required to discharge them separately. When the flue gas is treated according to environmental protection requirements, two sets of environmental protection treatment devices need to be set up; (2) Since the regenerative combustion technology requires reciprocating reversing, the gas in the common section after the gas and smoke reversing valve will be discharged with the flue gas. The average CO emission concentration in the smoke flue gas is generally 6000-30000 mg / m3. The CO emission concentration of the smoke flue gas of some heating furnaces can even reach 50 (3) The NOx emission concentration in flue gas is generally above 150mg / m3, and some are even between 200-350mg / m3. Only a small number of heating furnaces with temperatures below 1100℃ can be controlled within 100-150mg / m3 in the initial stage of production. However, with the increase of service life, the NOx emission concentration will gradually increase. (4) The flue gas temperature is generally below 180℃, and a large proportion of low calorific value gas heating furnaces have a flue gas emission temperature between 80-140℃.

[0003] Environmental protection standards in some provinces require that CO emissions from industrial furnaces be less than 6000 mg / m3 (some provinces require CO emissions not to exceed 1000 mg / m3), and that flue gas NOx emissions should not exceed 100 mg / m 3 , flue gas SO2 emissions shall not exceed 50mg / m 3 This requires that industrial furnaces in the metallurgical industry must reduce the emission of flue gas pollutants, and according to the current development trend of the environmental protection industry, the requirements for flue gas emissions from industrial furnaces will be more stringent.

[0004] In the pollutant emissions of industrial furnaces in the metallurgical industry, SO2 mainly comes from fuels. For each industrial furnace, due to different fuel conditions, the sulfur content in the flue gas varies. Moreover, there are many end-treatment methods for flue gas SO2, and the treatment by desulfurization facilities can meet the emission index requirements. Regarding the treatment methods for CO and NOx in the flue gas of low-calorific-value gas double regenerative heating furnaces, the following methods are generally adopted: (1) The current technology to solve the problem of excessive CO emissions and already in implementation is to blow the flue gas in the commutation common section back into the furnace through flue gas circulation technology. Using this flue gas circulation and back-blowing technology not only wastes the electric energy of the fan, but also affects the combustion effect and wastes fuel when pursuing low emissions. From the result, it can only reduce part of the CO emission index, and some industrial furnaces can meet the emission index, but in the long run, it cannot meet higher environmental protection requirements; (2) For the treatment of nitrogen oxides in flue gas, the currently more economical and mature treatment method generally adopts low-temperature SCR denitration, but the catalytic reaction temperature needs to be above 180°C, and the temperature range with higher efficiency is 200 - 450°C. However, the flue gas emission temperature is generally lower than 180°C, and even below 140°C, so the flue gas needs to be heated up. Considering energy conservation, the flue gas also needs to be cooled down by secondary heat exchange, which increases the one-time fixed investment and operating cost. In view of this, the present invention proposes a low-calorific-value gas heating furnace with ultra-low emissions to solve the problems existing in the traditional low-calorific-value gas double regenerative technology. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a low-calorific-value gas heating furnace with ultra-low emissions, which adopts the technologies of preheating low-calorific-value gas and air regeneration.

[0006] The present invention is implemented as follows. A low-calorific-value gas heating furnace with ultra-low emissions is provided, which includes a heating furnace body, a low-calorific-value gas burner unit, a gas supply unit, an air supply unit, and a flue gas emission unit. In each heating zone of the heating furnace body, there are several low-calorific-value gas burner units. The low-calorific-value gas burner unit includes a gas nozzle and an air regeneration nozzle. The gas supply unit includes a gas-flue gas heat exchange preheater and a gas transmission pipeline. The gas-flue gas heat exchange preheater is respectively connected to each gas nozzle through the gas transmission pipeline. The air supply unit includes an air transmission pipeline, and the air transmission pipeline is respectively connected to each air regeneration nozzle. The flue gas emission unit includes an empty flue gas emission pipeline, a furnace tail flue gas emission pipeline, and a flue gas environmental protection treatment component. The empty flue gas emission pipeline is connected to each air regeneration nozzle. After the empty flue gas emission pipeline and the furnace tail flue gas emission pipeline converge, they are connected to the gas-flue gas heat exchange preheater, and then connected to the flue gas environmental protection treatment component.

[0007] Preferably, the gas transmission pipeline includes a main gas transmission pipeline, a gas transmission heating zone branch pipeline, and a gas transmission nozzle branch pipeline. The main gas transmission pipeline branches out into multiple gas transmission heating zone branch pipelines, and each gas transmission heating zone branch pipeline branches out into multiple gas transmission nozzle branch pipelines. On the gas transmission heating zone branch pipeline, a gas flow meter and a gas automatic regulating valve are provided. On each gas transmission nozzle branch pipeline, a gas pneumatic quick cut-off valve and a gas manual regulating valve are provided.

[0008] More preferably, the air transmission pipeline includes a main air transmission pipeline, an air transmission heating zone branch pipeline, and an air transmission nozzle branch pipeline. The main air transmission pipeline branches out into multiple air transmission heating zone branch pipelines, and each air transmission heating zone branch pipeline branches out into multiple air transmission nozzle branch pipelines. On each air transmission heating zone branch pipeline, an air flow meter and an air automatic regulating valve are provided;

[0009] The empty flue gas discharge pipeline includes a main empty flue gas discharge pipeline, an empty flue gas discharge heating zone branch pipeline, and an empty flue gas discharge nozzle branch pipeline. The main empty flue gas discharge pipeline branches out into multiple empty flue gas discharge heating zone branch pipelines, and each empty flue gas discharge heating zone branch pipeline branches out into multiple empty flue gas discharge nozzle branch pipelines. On the empty flue gas discharge heating zone branch pipeline, a flue gas automatic regulating valve is provided;

[0010] Each empty flue gas discharge nozzle branch pipeline is connected to the air transmission nozzle branch pipeline. On each empty flue gas discharge nozzle branch pipeline, a first pneumatic two-way changeover valve and a flue gas manual regulating valve are provided. On each air transmission nozzle branch pipeline, a second pneumatic two-way changeover valve and an air manual regulating valve are provided. On the air transmission nozzle branch pipeline between the connection point of the empty flue gas discharge nozzle branch pipeline and the air storage nozzle, an empty flue gas manual regulating valve is provided.

[0011] More preferably, it further includes a cold air dilution pipeline. One end of the cold air dilution pipeline is connected to the air transmission pipeline, and the other end is connected to the furnace tail flue gas discharge pipeline. A cold air manual regulating valve and a cold air automatic regulating cut-off valve are provided on the cold air dilution pipeline.

[0012] More preferably, the gas supply unit further includes a gas control valve group. The gas control valve group includes an electric butterfly valve, an electric blind plate valve, and a pneumatic quick cut-off valve connected in sequence according to the gas transmission direction. A nitrogen purge and discharge pipeline is connected to the gas transmission pipeline.

[0013] Further preferably, the empty cigarette emission pipeline is first connected to the empty cigarette induced draft fan, and then branches out into two branches. One branch is connected to the furnace tail flue gas emission pipeline, and the other branch is connected to the flue gas environmental protection treatment component; the flue gas environmental protection treatment component includes one or more of a desulfurization device, a denitration device, a dust removal device, and a second waste heat recovery device. The flue gas environmental protection treatment component is finally connected to the flue gas induced draft fan. A first waste heat recovery device is arranged on the furnace tail flue gas emission pipeline or on the flue gas outlet side of the gas-smoke heat exchange preheater.

[0014] Further preferably, each of the low calorific value gas burner units includes one or more of the gas nozzles and one or more of the air regenerative nozzles. The gas nozzles and the air regenerative nozzles in each group of low calorific value gas burner units are arranged vertically or horizontally with respect to each other.

[0015] Further preferably, the air supply unit further includes an air blower, and the air blower is connected to the air delivery pipeline.

[0016] Further preferably, an all-oxygen supply unit is further provided. The all-oxygen supply unit includes an all-oxygen burner and an oxygen supply pipeline. The all-oxygen burner is arranged in the high-temperature section of the heating furnace furnace body. The oxygen supply pipeline includes an oxygen supply main pipeline and an oxygen supply all-oxygen burner branch pipeline. The oxygen supply main pipeline branches out into a plurality of oxygen supply all-oxygen burner branch pipelines, and each oxygen supply all-oxygen burner branch pipeline is connected to an all-oxygen burner.

[0017] Further preferably, on the oxygen supply main pipeline, in the direction from far to near the oxygen supply all-oxygen burner branch pipeline, a first oxygen manual valve, a first oxygen pressure sensor, an oxygen automatic regulating valve, an oxygen automatic cut-off valve, a second oxygen manual valve, and a second oxygen pressure sensor are sequentially arranged. On the pipeline on the side of the first oxygen manual valve close to the oxygen supply all-oxygen burner branch pipeline, a first flame arrester is provided. On the pipeline on the side of the second oxygen manual valve far from the oxygen supply all-oxygen burner branch pipeline, a second flame arrester is provided.

[0018] Compared with the prior art, the advantages of the present invention are as follows:

[0019] 1) The CO emission concentration of the flue gas is reduced to less than 2000 mg / m3, and even below 1000 mg / m3, which can meet the current most stringent local environmental protection standards;

[0020] 2) The temperature of the flue gas desulfurization and denitration is in a suitable catalytic temperature range, and no additional heat source needs to be added. The secondary heating and heat exchange processes are reduced, the process is simplified, and the primary investment and the flue gas environmental protection treatment cost are reduced;

[0021] 3) Compared with the two flue gas environmental protection treatment devices of the original low calorific value gas double regenerative heating furnace, the heating furnace of the present invention has only one kind of flue gas, and only one set of environmental protection treatment device needs to be set when environmental protection treatment is required. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 FIG. is a schematic structural diagram of a heating furnace with a low calorific value gas heating furnace provided with ultra-low emissions according to the present invention;

[0023] Figure 2 FIG. is a schematic diagram of the vertical arrangement of the low calorific value gas burner units in the present invention;

[0024] Figure 3 FIG. is a schematic diagram of the left-right arrangement of the low calorific value gas burner units in the present invention;

[0025] Figure 4 FIG. is a schematic diagram of the oxygen-enriched pipeline system of the low calorific value oxygen-enriched burner in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not used to limit the present invention.

[0027] Embodiment 1

[0028] Refer to Figure 1 , the present invention provides a low calorific value gas heating furnace with ultra-low emissions, including a heating furnace body 20, a low calorific value gas burner unit, a gas supply unit, an air supply unit and a flue gas discharge unit. A number of low calorific value gas burner units are provided in each heating zone of the heating furnace body 20. The low calorific value gas burner unit includes a gas nozzle 1 and an air regenerative nozzle 2. The gas supply unit includes a gas-flue gas heat exchange preheater 3 and a gas pipeline 4. The gas-flue gas heat exchange preheater 3 is respectively connected to each gas nozzle 1 through the gas pipeline 4. The air supply unit includes an air pipeline 5, and the air pipeline 5 is respectively connected to each air regenerative nozzle 2. The flue gas discharge unit includes an empty flue gas discharge pipeline 6, a furnace tail flue gas discharge pipeline 7 and a flue gas environmental protection treatment component. The empty flue gas discharge pipeline 6 is connected to each air regenerative nozzle 2. After the empty flue gas discharge pipeline 6 and the furnace tail flue gas discharge pipeline 7 converge, they are connected to the gas-flue gas heat exchange preheater 3 and then connected to the flue gas environmental protection treatment component.

[0029] When using the low-calorific-value gas heating furnace with ultra-low emissions provided by the present invention, the flue gas first enters the gas-flue gas heat exchange preheater 3 for preheating. After being preheated to 200 - 450 °C, the gas is sent to the gas nozzle 1 through the gas delivery pipeline 4, and the air is sent to the air regenerative nozzle 2 through the air delivery pipeline 5. The air is regenerated by the high-temperature flue gas generated in the regenerator of the air regenerative nozzle 2 and regenerated to 700 - 1200 °C. The preheated gas is ejected from the gas nozzle 1, and the regenerated air is ejected from the air regenerative nozzle 2. The two diffuse and burn in the heating furnace to heat the billet; the flue gas generated by combustion is divided into two parts. One part enters the air regenerative nozzle 2 to heat the air in the regenerator, and then the flue gas that has completed air regeneration is discharged through the empty flue gas discharge pipeline 6. The remaining part of the flue gas is discharged through the furnace tail flue gas discharge pipeline 7 and converges with the flue gas discharged from the empty flue gas discharge pipeline 6 and enters the gas-flue gas heat exchange preheater 3 together to preheat the gas. After the preheating is completed, the flue gas is then subjected to environmental protection treatment by the flue gas environmental protection treatment component, and after being treated to meet the discharge standard, it is discharged.

[0030] The regenerator of the air regenerative nozzle 2 can use a honeycomb body or ceramic balls; it is advisable to select a regenerative material with good regenerative performance. To ensure the service life of the gas-flue gas heat exchange preheater 3, preferably, the proportion of stainless steel material in the gas-flue gas heat exchange preheater 3 is increased, and all stainless steel materials are used. The spray gun of the gas nozzle 1 is preferably made of stainless steel, and different materials can be selected according to different temperature ranges.

[0031] The present invention preheats the gas to 200 - 450 °C and regenerates the air to 700 - 1200 °C. There is no common area for low-calorific-value gas regeneration, which can achieve complete combustion and greatly reduce the CO content in the flue gas. Using the system of the present invention, in the CO emission reduction project of the third rolling heating furnace in the rolling mill department of a certain company, the CO in the flue gas discharged from the heating furnace was detected three times, and the detection results were 856 mg / m 3 、785 mg / m 3 、860 mg / m 3 , all of which are lower than the implementation standard of 1000 mg / m 3 .

[0032] In order to regulate the gas transported by the gas transmission pipeline 4, as an improvement of the technical solution, the gas transmission pipeline 4 includes a main gas transmission pipeline 401, a gas transmission heating zone branch 402, and a gas transmission nozzle branch 403. The main gas transmission pipeline 401 branches out into multiple gas transmission heating zone branches 402, and each gas transmission heating zone branch 402 branches out into multiple gas transmission nozzle branches 403. On the gas transmission heating zone branch 402, there are a gas flow meter 4021 and a gas automatic regulating valve 4022. On each gas transmission nozzle branch 403, there are a gas pneumatic quick cut-off valve 4031 and a gas manual regulating valve 4032.

[0033] During the gas transmission process, after preheating, the gas first passes through the main gas transmission pipeline 401, then through the gas transmission heating zone branch 402. On the gas transmission heating zone branch 402, the gas flow is measured by the gas flow meter 4021, and the flow is automatically adjusted by the gas automatic regulating valve 4022. Then it passes through the gas transmission nozzle branch 403 and enters the gas nozzle 1. On the gas transmission nozzle branch 403, it is adjusted by the gas pneumatic quick cut-off valve 4031 and the gas manual regulating valve 4032.

[0034] In order to regulate the air transported by the air transmission pipeline 5 and the flue gas discharged by the empty flue gas discharge pipeline 6, as an improvement of the technical solution, the air transmission pipeline 5 includes a main air transmission pipeline 501, an air transmission heating zone branch 502, and an air transmission nozzle branch 503. The main air transmission pipeline 501 branches out into multiple air transmission heating zone branches 502, and each air transmission heating zone branch 502 branches out into multiple air transmission nozzle branches 503. On each air transmission heating zone branch 502, there are an air flow meter 5021 and an air automatic regulating valve 5022;

[0035] The empty flue gas discharge pipeline 6 includes a main empty flue gas discharge pipeline 601, an empty flue gas discharge heating zone branch 602, and an empty flue gas discharge nozzle branch 603. The main empty flue gas discharge pipeline 601 branches out into multiple empty flue gas discharge heating zone branches 602, and each empty flue gas discharge heating zone branch 602 branches out into multiple empty flue gas discharge nozzle branches 603. On the empty flue gas discharge heating zone branch 602, there is a flue gas automatic regulating valve 6021;

[0036] Each empty flue gas discharge nozzle branch 603 is connected to the air transmission nozzle branch 503. On each empty flue gas discharge nozzle branch 603, there are a first pneumatic two-way changeover valve 6031 and a flue gas manual regulating valve 6032. On each air transmission nozzle branch 503, there are a second pneumatic two-way changeover valve 5031 and an air manual regulating valve 5032. On the air transmission nozzle branch 503 between the connection point of the empty flue gas discharge nozzle branch 603 and the air storage nozzle 2, there is an empty flue gas manual regulating valve 5033.

[0037] When air intake is required, the first pneumatic two-way changeover valve 6031 closes, and the second pneumatic two-way changeover valve 5031 opens. Air enters the air regenerative nozzle 2 through the main air delivery pipeline 501, the air delivery heating zone branch 502, and the air delivery nozzle branch 503. The air flowmeter 5021 on the air delivery heating zone branch 502 detects the air flow rate, the air automatic regulating valve 5022 adjusts the air flow rate, and the air manual regulating valve 5032 performs manual adjustment;

[0038] When flue gas discharge is required, the first pneumatic two-way changeover valve 6031 opens, and the second pneumatic two-way changeover valve 5031 closes. After the flue gas passes through the air regenerative nozzle 2, it is discharged through the empty flue gas discharge nozzle branch 603, the empty flue gas discharge heating zone branch 602, and the empty flue gas discharge main pipeline 601. The flue gas is adjusted by the empty flue gas manual regulating valve 5033, the flue gas manual regulating valve 6032, and the flue gas automatic regulating valve 6021.

[0039] In the above two processes, the changeover valve is for changeover adjustment and has a changeover time. The combustion side and the smoke exhaust side alternate in working.

[0040] For a group of burners, combustion and smoke exhaust alternate. Each changeover is a changeover cycle. When a group of burners are burning, a certain burner on the other side of the furnace wall should be in the smoke exhaust state to achieve the balance of the furnace pressure. The burners corresponding to smoke exhaust are generally arranged symmetrically along both sides of the furnace wall, or can also be other nearby burners, forming a pair of burners.

[0041] The working states of the low calorific value gas environmental protection burner can be divided into 3 states: combustion - shutdown - smoke exhaust. The conversion of its working states can be: combustion - smoke exhaust - combustion - smoke exhaust, or can also be: combustion - shutdown - smoke exhaust - shutdown - combustion - shutdown - smoke exhaust - shutdown. Within a changeover cycle, the burner can continuously burn or continuously exhaust smoke, or can also be combustion + shutdown, or smoke exhaust + shutdown.

[0042] To further cool down the flue gas, as an improvement of the technical solution, it further includes a cold air dilution pipeline 12. One end of the cold air dilution pipeline 12 is connected to the air delivery pipeline 5, and the other end is connected to the furnace tail flue gas discharge pipeline 7. A cold air manual regulating valve 1201 and a cold air automatic regulating cut-off valve 1202 are provided on the cold air dilution pipeline 12. The cold air dilution pipeline 12 ensures that the temperature of the flue gas entering the gas - flue gas heat exchange preheater 3 does not exceed the temperature limit.

[0043] To further control the gas transmission, as an improvement to the technical solution, the gas supply unit further includes a gas control valve group. The gas control valve group includes an electric butterfly valve 8, an electric blind plate valve 9, and a pneumatic quick cut-off valve 10 connected in sequence according to the gas transmission direction. A nitrogen purge and discharge pipeline 11 is connected to the gas transmission pipeline 4.

[0044] To provide power for the empty flue gas discharge and comprehensively treat the flue gas environmentally, as an improvement to the technical solution, the empty flue gas discharge pipeline 6 is first connected to the empty flue gas induced draft fan 13, and then branches out into two branches. One branch is connected to the furnace tail flue gas discharge pipeline 7, and the other branch is connected to the flue gas environmental protection treatment component; the flue gas environmental protection treatment component includes one or more of a desulfurization device 14, a denitration device 15, a dust removal device 16, and a second waste heat recovery device 17. The flue gas environmental protection treatment component is finally connected to the flue gas induced draft fan 18. A first waste heat recovery device 22 is provided on the furnace tail flue gas discharge pipeline 7. The function of the first waste heat recovery device 22 is to reduce the flue gas temperature entering the gas-gas heat exchange preheater 3, protect the gas-gas heat exchange preheater 3 from overheating, improve the safety of the gas in the gas-gas heat exchange preheater 3, and at the same time make the flue gas temperature more suitable for the optimal reaction temperature of the desulfurization device 14 and the denitration device 15. If the first waste heat recovery device 22 is arranged in front of the desulfurization device 14 according to process requirements, it is to reduce the flue gas temperature and make the flue gas temperature more suitable for the optimal reaction temperature of the desulfurization device 14 and the denitration device 15. If the flue gas temperature is already at the optimal reaction temperature, the first waste heat recovery device 22 can be not arranged.

[0045] It is set like this to adjust the flue gas flow rate of the gas-gas heat exchange preheater 3 and further adjust the designed external dimension of the gas-gas heat exchange preheater 3; preferably, on the branch connected to the flue gas environmental protection treatment component, a manual regulating valve, an electric regulating valve, and a manual regulating valve are arranged in sequence according to the flue gas discharge order.

[0046] Since the flue gas temperature is in the active temperature range of dry desulfurization (taking sodium bicarbonate or calcium carbonate powder as an example of the flue gas desulfurization adsorbent), preferably, the desulfurization device 14 adopts dry desulfurization, which can effectively reduce the desulfurization production cost and consumable costs.

[0047] Reference Figure 2 and Figure 3, according to specific circumstances, each of the low calorific value gas burner units includes one or more of the gas nozzles 1 and one or more of the air regenerative nozzles 2. The gas nozzles 1 and the air regenerative nozzles 2 in each group of low calorific value gas burner units are arranged vertically or horizontally relative to each other. When arranged vertically, the gas nozzles 1 of the upper low calorific value gas burner unit are at the bottom and the air regenerative nozzles 2 are at the top, while the gas nozzles 1 of the lower low calorific value gas burner unit are at the top and the air regenerative nozzles 2 are at the bottom. This arrangement can reduce the oxidation loss of the billet during heating; when arranged horizontally, the air regenerative nozzles 2 and the gas nozzles 1 can be arranged in pairs, or several gas spray guns can be arranged on the left and right sides with the air regenerative nozzles 2 in the middle and the gas nozzles 1, which is convenient for uniform mixing and complete combustion.

[0048] To provide power for air delivery, as an improvement of the technical solution, the air delivery unit further includes an air blower 19, and the air blower 19 is connected to the air delivery pipeline 5.

[0049] In this reheating furnace, the low calorific value gas burner units can be controlled individually or as a whole in zones. When controlling in zones, dual cross-limiting control can be adopted according to the set air-fuel ratio; when controlling individually, interval combustion or pulse combustion can be achieved. Through the opening and closing cooperation of the gas pneumatic cut-off valve, the air pneumatic cut-off valve, and the air and flue gas pneumatic cut-off valve, the air regenerative nozzles in the low calorific value gas burner units perform the processes of alternating combustion and smoke exhaust. In each group of low calorific value gas burner units, when the air regenerative nozzle 2 sprays air, the corresponding gas nozzle 1 sprays gas, and they are mixed and burned in the furnace; when the air regenerative nozzle 2 discharges flue gas, the corresponding gas nozzle 1 cuts off the gas and stops burning.

[0050] The furnace body 20 of the reheating furnace is a refractory masonry furnace wall and a refractory masonry furnace roof, generally composed of a combination of refractory fiber, refractory bricks, and refractory castables, and preferably uses a fiber module structure, which can improve the heat preservation performance of the furnace body.

[0051] Example 2

[0052] In some reheating furnaces with higher furnace temperature requirements, preferably, flat flame burners or straight flame burners or a combination of both are arranged in the high temperature section. These burners can use high calorific value gas burners. When using low calorific value gas, preferably, low calorific value gas oxy-fuel burners or low calorific value gas enriched oxygen burners are used. When using low calorific value gas oxy-fuel or enriched oxygen burners, oxygen pipelines and related valve groups must be configured. Preferably, the oxygen pipeline uses degreased stainless steel pipes; for the preferred configuration of the oxygen valve group, there is at least one control valve group in each heating zone, and each burner oxygen pipeline is equipped with an oxygen special hand valve and an oxygen special automatic cut-off valve, and the corresponding manual valve and pneumatic cut-off valve are configured for each burner gas pipeline.

[0053] ReferenceFigure 4 , the difference between this embodiment and Embodiment 1 is that there is also an all-oxygen gas supply unit, which includes an all-oxygen burner 23 and an oxygen gas supply pipeline 24. The all-oxygen burner 23 is arranged in the high-temperature section of the heating furnace body 20. The oxygen gas supply pipeline 24 includes an oxygen gas supply main pipeline 2401 and an all-oxygen burner branch 2402 of the oxygen gas supply. The oxygen gas supply main pipeline 2401 branches out multiple all-oxygen burner branches 2402 of the oxygen gas supply, and each all-oxygen burner branch 2402 of the oxygen gas supply is connected to an all-oxygen burner 23.

[0054] For the convenience of monitoring and control, as an improvement of the technical solution, on the oxygen gas supply main pipeline 2401, in the direction from far to near the all-oxygen burner branch 2402 of the oxygen gas supply, a first oxygen manual valve 25, a first oxygen pressure sensor 26, an oxygen automatic regulating valve 27, an oxygen automatic cut-off valve 28, a second oxygen manual valve 29 and a second oxygen pressure sensor 30 are successively arranged. On the pipeline on the side of the first oxygen manual valve 25 close to the all-oxygen burner branch 2402 of the oxygen gas supply, a first flame arrester 31 is arranged. On the pipeline on the side of the second oxygen manual valve 29 far from the all-oxygen burner branch 2402 of the oxygen gas supply, a second flame arrester 32 is arranged.

[0055] The all-oxygen gas supply unit is also provided with an all-oxygen nitrogen purging pipeline 33 and a replacement and sewage discharge pipeline 34; on both sides of the first oxygen pressure sensor 26, an oxygen flowmeter 35 and an oxygen temperature sensor 36 are arranged.

[0056] An oxygen special manual valve 37 and an oxygen special automatic cut-off valve 38 are arranged on each all-oxygen burner branch 2402 of the oxygen gas supply.

[0057] If an oxygen-enriched oxygen supply system is selected, an air-oxygen mixer, an oxygen analyzer, a pressure detection instrument, a temperature detection instrument and an air blower are added to adjust the appropriate proportion of air and oxygen, and then they are mixed in the air-oxygen mixer and transported to each oxygen-enriched burner branch pipeline.

[0058] Embodiment 3

[0059] The difference between this embodiment and Embodiment 1 is as follows:

[0060] Temperature detectors are arranged in the empty flue gas, the furnace tail flue gas, the flue gas after each mixing, the flue gas before environmental protection treatment, the flue gas after environmental protection treatment, and the final discharged flue gas to measure the flue gas temperature at these positions; preferably, temperature measurement points are arranged behind each air regenerative nozzle 2 and in the flue gas pipeline after the empty flue gas header of each heating zone, and the combustion system of the heating furnace is optimized and controlled according to the measured temperature.

[0061] A calorimeter is installed in the main gas pipeline 401. According to the real-time calorific value of the gas detected by the calorimeter, the required air-fuel ratio is calculated by a computer to optimize the control of the heating furnace combustion system.

[0062] O2 and CO detectors are installed in the empty flue gas discharge pipeline 6 and the furnace tail flue gas discharge pipeline 7 to optimize the control of the heating furnace combustion system.

[0063] O2, CO, SO2, and NOx detectors are installed in the pipelines before and after the flue gas environmental protection treatment component to optimize the control of the environmental protection treatment system.

[0064] An in-line heating pyrometer for billets is installed in the heating furnace to directly measure the temperature of the billets in the furnace. The measurement results are fed back to the computer system to optimize and implement the combustion control.

Claims

1. An ultra-low emission low calorific value gas heating furnace, characterized in that, it includes a heating furnace body (20), a low calorific value gas burner unit, a gas supply unit, an air supply unit and a flue gas emission unit. A number of low calorific value gas burner units are provided in each heating zone of the heating furnace body (20). The low calorific value gas burner unit includes a gas nozzle (1) and an air regenerative heat storage nozzle (2). The gas supply unit includes a gas-gas heat exchange preheater (3) and a gas transmission pipeline (4). The gas-gas heat exchange preheater (3) is respectively connected to each gas nozzle (1) through the gas transmission pipeline (4). The air supply unit includes an air transmission pipeline (5). The air transmission pipeline (5) is respectively connected to each air regenerative heat storage nozzle (2). The flue gas emission unit includes an empty flue gas emission pipeline (6), a furnace tail flue gas emission pipeline (7) and a flue gas environmental protection treatment component. The empty flue gas emission pipeline (6) is connected to each air regenerative heat storage nozzle (2). After the empty flue gas emission pipeline (6) converges with the furnace tail flue gas emission pipeline (7), it is connected to the gas-gas heat exchange preheater (3), and then connected to the flue gas environmental protection treatment component; The gas transmission pipeline (4) includes a gas transmission main pipeline (401), a gas transmission heating zone branch (402) and a gas transmission nozzle branch (403). The gas transmission main pipeline (401) branches out multiple gas transmission heating zone branches (402). Each gas transmission heating zone branch (402) branches out multiple gas transmission nozzle branches (403). On the gas transmission heating zone branch (402), a gas flow meter (4021) and a gas automatic regulating valve (4022) are provided. On each gas transmission nozzle branch (403), a gas pneumatic quick cut valve (4031) and a gas manual regulating valve (4032) are provided; The air transmission pipeline (5) includes an air transmission main pipeline (501), an air transmission heating zone branch (502) and an air transmission nozzle branch (503). The air transmission main pipeline (501) branches out multiple air transmission heating zone branches (502). Each air transmission heating zone branch (502) branches out multiple air transmission nozzle branches (503). On each air transmission heating zone branch (502), an air flow meter (5021) and an air automatic regulating valve (5022) are provided; The empty flue gas emission pipeline (6) includes an empty flue gas emission main pipeline (601), an empty flue gas emission heating zone branch (602) and an empty flue gas emission nozzle branch (603). The empty flue gas emission main pipeline (601) branches out multiple empty flue gas emission heating zone branches (602). Each empty flue gas emission heating zone branch (602) branches out multiple empty flue gas emission nozzle branches (603). On the empty flue gas emission heating zone branch (602), a flue gas automatic regulating valve (6021) is provided; Each empty flue gas discharge nozzle branch (603) is connected to the air delivery nozzle branch (503). On each empty flue gas discharge nozzle branch (603), there is a first pneumatic two-way changeover valve (6031) and a flue gas manual regulating valve (6032). On each air delivery nozzle branch (503), there is a second pneumatic two-way changeover valve (5031) and an air manual regulating valve (5032). On the air delivery nozzle branch (503) between the connection point of the empty flue gas discharge nozzle branch (603) and the air delivery nozzle branch (503) and the air regenerative heat storage nozzle (2), there is an empty flue gas manual regulating valve (5033). The empty flue gas discharge pipeline (6) is first connected to the empty flue gas induced draft fan (13), and then branches into two branches. One branch is connected to the furnace tail flue gas discharge pipeline (7), and the other branch is connected to the flue gas environmental protection treatment assembly. The flue gas environmental protection treatment assembly includes one or more of a desulfurization device (14), a denitration device (15), a dust removal device (16), and a second waste heat recovery device (17). The flue gas environmental protection treatment assembly is finally connected to the flue gas induced draft fan (18). A first waste heat recovery device (22) is provided on the furnace tail flue gas discharge pipeline (7) or on the flue gas outlet side of the gas-gas heat exchange preheater (3).

2. The low calorific value gas heating furnace with ultra-low emissions according to claim 1, characterized in that, it further includes a cold air dilution pipeline (12). One end of the cold air dilution pipeline (12) is connected to the air delivery pipeline (5), and the other end is connected to the furnace tail flue gas discharge pipeline (7). A cold air manual regulating valve (1201) and a cold air automatic regulating cut-off valve (1202) are provided on the cold air dilution pipeline (12).

3. The low calorific value gas heating furnace with ultra-low emissions according to claim 1, characterized in that, the gas supply unit further includes a gas control valve group. The gas control valve group includes an electric butterfly valve (8), an electric blind plate valve (9), and a pneumatic quick cut-off valve (10) connected in sequence according to the gas transmission direction. A nitrogen purge and discharge pipeline (11) is connected to the gas transmission pipeline (4).

4. The low calorific value gas heating furnace with ultra-low emissions according to claim 1, characterized in that, each of the low calorific value gas burner units includes one or more of the gas nozzles (1) and one or more of the air regenerative heat storage nozzles (2). The gas nozzles (1) and the air regenerative heat storage nozzles (2) in each group of low calorific value gas burner units are arranged vertically or horizontally with respect to each other.

5. The low calorific value gas heating furnace with ultra-low emissions according to claim 1, characterized in that, the air supply unit further includes an air blower (19). The air blower (19) is connected to the air delivery pipeline (5).

6. The low calorific value gas heating furnace with ultra-low emissions according to claim 1, characterized in that, An all-oxygen supply unit is further provided. The all-oxygen supply unit includes an all-oxygen burner (23) and an oxygen supply pipeline (24). The all-oxygen burner (23) is arranged in the high-temperature section of the heating furnace body (20). The oxygen supply pipeline (24) includes an oxygen supply main pipeline (2401) and an all-oxygen burner branch of the oxygen supply pipeline (2402). The oxygen supply main pipeline (2401) branches out multiple all-oxygen burner branches of the oxygen supply pipeline (2402), and each all-oxygen burner branch of the oxygen supply pipeline (2402) is connected to an all-oxygen burner (23).

7. The low-calorific value gas heating furnace with ultra-low emissions according to claim 6, characterized in that on the oxygen supply main pipeline (2401), in the direction from far to near the all-oxygen burner branch of the oxygen supply pipeline (2402), a first oxygen manual valve (25), a first oxygen pressure sensor (26), an oxygen automatic regulating valve (27), an oxygen automatic cut-off valve (28), a second oxygen manual valve (29) and a second oxygen pressure sensor (30) are successively arranged. On the pipeline on the side of the first oxygen manual valve (25) close to the all-oxygen burner branch of the oxygen supply pipeline (2402), a first flame arrester (31) is arranged. On the pipeline on the side of the second oxygen manual valve (29) far from the all-oxygen burner branch of the oxygen supply pipeline (2402), a second flame arrester (32) is arranged.

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