Industrial silicon smelting furnace flue gas comprehensive treatment system and process

Abstract

The application discloses an industrial silicon smelting furnace flue gas comprehensive treatment system and process, and belongs to the field of industrial silicon smelting furnace flue gas treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flue gas treatment, and particularly relates to an industrial silicon smelting furnace flue gas comprehensive treatment system and process. BACKGROUND

[0002] The information disclosed in this Background section is for the purpose of generally presenting the context of the application. The information

[0003] In recent years, with the rapid development of the photovoltaic industry, the demand for industrial silicon, a raw material for polycrystalline silicon, has rapidly increased. Industrial silicon is produced by smelting silicon stone with carbonaceous reducing agents at high temperatures in a smelting furnace. A 33,000 kVA industrial silicon smelting furnace discharges flue gas with a temperature of 400-800℃, a flue gas volume of 220,000 Nm 3 / h, a particulate matter (micro-silicon powder) content of about 4 g / Nm 3 , a SO2 content of 130 mg / Nm 3 , a NO x content of about 85 mg / Nm 3 , which pollutes the ecological environment on which human beings depend for survival and seriously affects human health and life.

[0004] Many industrial silicon smelting furnace flue gas treatment processes have been reported, however, the existing industrial silicon smelting furnace flue gas treatment processes are independent of the industrial silicon smelting process, and the two cannot produce a synergistic effect. At the same time, the existing flue gas treatment process generally arranges desulfurization, denitrification and dust removal procedures between the waste heat boiler and the discharge chimney, which on the one hand leads to low desulfurization and denitrification temperatures and thus low efficiency; on the other hand, the sensible heat of the flue gas after desulfurization and denitrification cannot be fully recovered (for example, heat in the temperature range of 150℃ to 200℃ is not recovered), and if a waste heat boiler is continuously added, it will lead to a long process and a large device footprint. In addition, since the waste heat boiler is before the dust removal step, a large amount of micro-silicon powder binder accumulates in the waste heat boiler, which is difficult to clean and has dead angles for cleaning, and long-term incomplete cleaning will lead to a decrease in the heat exchange efficiency of the waste heat boiler.

[0005] In the smelting of industrial silicon, a large amount of high-volatility silicon dioxide and silicon gas is also generated in the smelting furnace, and the silicon dioxide and silicon gas are oxidized, condensed and precipitated during the flue gas emission process, i.e., micro-silicon powder is formed. In the existing industrial silicon smelting furnace flue gas treatment process, when micro-silicon powder is recovered, the flue gas treatment sequence is usually dust removal first, denitration last and desulfurization last, and the micro-silicon powder is recovered through a dust removal device, and the desulfurizer used in the process is generally a sodium-based desulfurizer (i.e., sodium bicarbonate); when micro-silicon powder is not recovered, the flue gas treatment process is usually desulfurization first, dust removal last and denitration last, and the desulfurizer used is generally a calcium-based desulfurizer (i.e., calcium hydroxide) with lower cost. For the process of recovering micro-silicon powder, the micro-silicon powder is generally used in the refractory brick and cement industries, but the silicon element therein is difficult to be effectively utilized, and the desulfurizer used in the process is sodium bicarbonate with high cost. For the process of not recovering micro-silicon powder, the micro-silicon powder collected by dust removal contains calcium hydroxide, calcium oxide, calcium sulfate and calcium sulfite, and is currently only used in the cement industry or harmless landfill treatment, and the silicon element cannot be effectively utilized. SUMMARY

[0006] Therefore, the present application provides an industrial silicon smelting furnace flue gas comprehensive treatment system and process, which can produce a synergistic effect with the industrial silicon smelting process, has high desulfurization and denitration efficiency, can fully recover the sensible heat in the process, and can effectively utilize the silicon element in the micro-silicon powder when using calcium hydroxide with low cost as the desulfurizer.

[0007] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0008] In a first aspect, the present application provides an industrial silicon smelting furnace flue gas comprehensive treatment system, which comprises, in sequence along the flue gas flow direction, a flue gas outlet pipe, a dust removal device, a high-temperature SCR denitration device, a waste heat boiler and a chimney; the flue gas outlet pipe is provided in multiple sections, the first pipe section is a vertical section, the second pipe section is a vertical-to-horizontal turning section, the third pipe section is a horizontal section, and the fourth pipe section is a horizontal-to-inclined turning section; the first pipe section, the second pipe section, the third pipe section and the fourth pipe section are connected in sequence, the bottom of the first pipe section is connected to a smoke hood on the smelting furnace body, and the end of the fourth pipe section is connected to the dust removal device through a connecting pipe; each of the first pipe section, the second pipe section, the third pipe section and the fourth pipe section is provided with a desulfurizer injection port, and the particle size of the desulfurizer in the desulfurizer injection ports of the first pipe section, the second pipe section, the third pipe section and the fourth pipe section decreases in sequence.

[0009] In a second aspect, the present application provides an industrial silicon smelting furnace flue gas comprehensive treatment process, which uses the above-mentioned system to treat the flue gas of an industrial silicon smelting furnace, and comprises the following steps:

[0010] Step (1): The flue gas of the industrial silicon smelting furnace passes through the smoke hood of the smelting furnace and enters the flue gas outlet pipe;

[0011] Step (2): Spraying calcium hydroxide desulfurizer into the desulfurizer spraying inlet on the multiple pipe sections of the flue gas leading pipe;

[0012] Step (3): After desulfurization, the flue gas enters the dust removal device, and the micro-silicon powder is collected by the dust removal device;

[0013] Step (4): After dust removal, the flue gas enters the high-temperature SCR denitration device;

[0014] Step (5): After denitration, the flue gas enters the waste heat boiler for heat exchange, and is finally discharged through the chimney.

[0015] In a third aspect, the present application provides a method for recycling the micro-silicon powder collected by the above process, comprising: the micro-silicon powder is used to produce manganese-silicon alloy, and the specific method comprises the following steps:

[0016] Step (1): Grinding the manganese ore, dolomite and bituminous coal to 150 mesh or less to obtain ground materials;

[0017] Step (2): Blending and mixing the ground materials in step (1) with the micro-silicon powder to obtain a mixture;

[0018] Step (3): Preheating the mixture in step (2) to 400-460 DEG C;

[0019] Step (4): Sending the preheated material into the pair roller balling device to obtain hot-pressed pellets;

[0020] Step (5): Sending the hot-pressed pellets into the submerged arc furnace for smelting to obtain manganese-silicon alloy, slag and submerged arc furnace gas.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] (1) The present application sets multiple flue gas leading pipes, and sets desulfurizer spraying inlets on each section, sprays calcium hydroxide desulfurizer with different particle sizes at different positions, and realizes the synergistic effect of flue gas treatment process and smelting process: for the flue gas treatment process, desulfurization and denitrification have higher temperature, so the efficiency is higher; the dust removal device has less burden, and the dust removal is easy; the waste heat boiler does not accumulate dust, and can continuously and efficiently operate; for the smelting process, part of the desulfurizer adsorbs micro-silicon powder and unreacted carbon, settles back into the furnace, improves the silicon yield, reduces the consumption of silica and carbon; improves the furnace charge resistance, improves the smelting intensity; improves the slag fluidity, avoids the furnace bottom lifting to cause shutdown for maintenance;

[0023] (2) The waste heat boiler of the present application can fully recover the sensible heat of the flue gas after desulfurization, dust removal and denitrification, and the process is short, and the device occupies small area;

[0024] (3) The present application uses low-cost calcium hydroxide as a desulfurizer, and the micro-silicon powder containing calcium oxide, calcium sulfate, calcium sulfite and other substances collected in the process is used to prepare manganese-silicon alloy, greatly improving the utilization rate of silicon element in the micro-silicon powder, and the produced manganese-silicon alloy can be used as a deoxidizer and alloying agent during steelmaking.

[0025] (4) The particulate matter content of flue gas after the process purification treatment of the present application is less than 10 mg / Nm 3 , the SO2 content is less than 30 mg / Nm 3 , the NO x content is less than 35 mg / Nm 3 , meeting the standard for direct flue gas discharge. BRIEF DESCRIPTION OF DRAWINGS

[0026] The drawings accompanying the specification of the present application serve to provide a further understanding of the present application, and the schematic embodiments of the present application and the description thereof serve to explain the present application and do not constitute an improper limitation on the present application.

[0027] Figure 1 is the elevation view of the submerged arc furnace body and the submerged arc furnace flue gas leading pipe of example 1 of the present application;

[0028] Figure 2 is the elevation layout diagram of the submerged arc furnace flue gas dust removal, denitration and waste heat boiler of example 1 of the present application;

[0029] Figure 3 is the flow diagram of the industrial silicon submerged arc furnace flue gas comprehensive treatment of example 2 of the present application;

[0030] Figure 4 is the micro-silicon powder recycling flow diagram of example 3 of the present application;

[0031] Among them, 1, submerged arc furnace body; 2, submerged arc furnace smoke hood; 3-1, first pipe section of flue gas leading pipe; 3-2, second pipe section of flue gas leading pipe; 3-3, third pipe section of flue gas leading pipe; 3-4, fourth pipe section of flue gas leading pipe; 4-1, first desulfurizer injection port; 4-2, second desulfurizer injection port; 4-3, desulfurizer injection port of second pipe section; 4-4, desulfurizer injection port of third pipe section; 4-5, desulfurizer injection port of fourth pipe section; 5, smelting workshop; 6, metal fiber filter bag dust collector; 7, high-temperature SCR denitration device; 8, waste heat boiler; 9, chimney. DETAILED DESCRIPTION

[0032] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs.

[0033] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0034] In view of the problems in the prior art that the industrial silicon smelting process and the industrial silicon furnace flue gas treatment process are independent of each other, the desulfurization and denitrification efficiency is low, the ash in the waste heat boiler is not easy to clean, the sensible heat cannot be fully recovered, and the element silicon in the micro-silicon powder cannot be effectively utilized when calcium hydroxide with low cost is used as a desulfurizing agent, the present application provides an industrial silicon furnace flue gas comprehensive treatment system and process.

[0035] In order for those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in combination with specific embodiments.

[0036] Embodiment 1

[0037] The present application provides an industrial silicon furnace flue gas comprehensive treatment system, as shown in Figure 1 and Figure 2 The system comprises, in sequence along the flue gas flow direction, a flue gas leading pipe, a dust removal device 6, a high-temperature SCR denitrification device 7, a waste heat boiler 8 and a chimney 9. The flue gas leading pipe is provided in multiple sections, and is used to lead the flue gas generated by the furnace body of the furnace to outside the workshop for subsequent flue gas treatment.

[0038] The first pipe section 3-1 of the flue gas leading pipe is a vertical section, the bottom of which is connected with the furnace hood 2 of the furnace, and two calcium hydroxide desulfurizing agent injection ports, i.e., a first desulfurizing agent injection port 4-1 and a second desulfurizing agent injection port 4-2, are provided at intervals on the upper portion of the flue gas leading pipe. The desulfurizing agent injection ports are both provided on the side of the flue gas leading pipe. There is no prior art that discloses a scheme of directly injecting desulfurizing agent into the flue gas leading pipe above the industrial silicon furnace. The flue gas temperature in the flue gas leading pipe of the present application is 400-800 DEG C, and therefore the desulfurizing agent action temperature interval is also in this temperature interval, and the desulfurization efficiency is relatively higher.

[0039] The first desulfurizer injection port 4-1 is located 1-4 m above the smoke hood, and the second desulfurizer injection port 4-2 is located 5-8 m above the smoke hood; the desulfurizer injected by the first desulfurizer injection port 4-1 and the second desulfurizer injection port 4-2 has a particle size of less than 8 mm, and the injection amount per hour is 4-10 kg. The flue gas generated from the submerged arc furnace body fully contacts with the calcium hydroxide desulfurizer injected by the first pipe section to occur a desulfurization reaction. Since the particle size of the desulfurizer at this position is relatively large, the particle size can even reach 8 mm. Meanwhile, two desulfurizer injection ports are arranged on the vertically arranged first pipe section at intervals, so that more desulfurizer is settled back to the furnace due to gravity. A large amount of flue gas generated from the submerged arc furnace also contains unreacted silicon dioxide (main component of micro silicon powder) and carbonaceous reducing agent. The loose and porous calcium-based desulfurizer can adsorb the micro silicon powder and unreacted carbonaceous reducing agent, and settle in the furnace. The main reaction occurring in the furnace is SiO2+2C→Si+2CO↑, so the silicon yield is improved, and the average silicon yield can be increased by 1 point, thereby reducing the consumption of raw materials such as silica and carbon. The settled desulfurizer can realize higher temperature (1500℃) desulfurization, and the calcium oxide in the furnace participates in slagging, which is beneficial to adsorb the sulfur in the furnace charge. At the same time, it can also improve the furnace charge resistance, increase the smelting intensity, and realize the production increase of the submerged arc furnace. The calcium-based desulfurizer entering the furnace can also form slag with unreacted SiO2, improve the slag fluidity, and avoid the deposition of unreacted SiO2 in the furnace, which can cause the furnace bottom to rise. If the furnace bottom rises too much, the furnace needs to be stopped for maintenance. Therefore, the improvement of the slag fluidity can reduce the frequency of stopping the furnace for maintenance.

[0040] The second pipe section 3-2 of the flue gas leading pipe is a vertical to horizontal turning section, the third pipe section 3-3 is a horizontal section, and the fourth pipe section 3-4 is a horizontal to downward turning section; the first pipe section 3-1, the second pipe section 3-2, the third pipe section 3-3, and the fourth pipe section 3-4 are sequentially connected, the flue gas generated in the smelting workshop is led out through the multi-pipe section, and the end of the fourth pipe section 3-4 is connected with the dust removal device 6 through a connecting pipe. Along the flue gas flow direction, the particle size of the desulfurizer is sequentially reduced, and the injection amount of the desulfurizer per hour is sequentially increased. Specifically, the desulfurizer injection port 4-3 of the second pipe section is located 10-14 m above the smoke hood, the particle size of the desulfurizer injected by the desulfurizer injection port 4-3 is less than 0.2 mm, and the injection amount per hour is 4-10 kg; the particle size of the desulfurizer injected by the desulfurizer injection port 4-4 of the third pipe section is less than 0.074 mm, and the injection amount per hour is 10-40 kg; the particle size of the desulfurizer injected by the desulfurizer injection port 4-5 of the fourth pipe section is less than 0.02 mm, and the injection amount per hour is 10-120 kg. The desulfurizer with a smaller particle size has a larger contact area with SO2 in the flue gas, and the desulfurization reaction is more sufficient under a higher injection amount. Therefore, the sequentially reduced particle size of the desulfurizer and the sequentially increased injection amount per hour make the SO2 in the led-out flue gas fully react with the desulfurizer, and the SO2 content in the finally purified flue gas is less than 30 mg / Nm 3In addition, the fine desulfurizer is beneficial to the modification of the micro silicon powder, promotes the particle size growth of the micro silicon powder, reduces the high temperature adhesion, and facilitates the back blowing and ash removal treatment of the filter bag of the subsequent dust removal device after capturing a large amount of dust.

[0041] The flue gas enters the dust removal device 6 from the fourth pipe section 3-4 of the flue gas guide pipe. Since the desulfurization process of the application is arranged before the dust removal device, the desulfurization process is beneficial to appropriately reducing the flue gas temperature, thereby reducing the high temperature impact on the filter bag of the dust removal device. In addition, the appropriate reduction of the flue gas temperature is also beneficial to the transformation of SiO to SiO2. Part of the SiO2 returns to the furnace in the desulfurization process, so the burden of the dust removal process is smaller. In the embodiment, the dust removal device is a metal fiber filter bag dust collector, which has excellent high temperature resistance and can realize dust removal at a higher temperature. In addition, the metal fiber filter bag dust collector itself is relatively easy to clean by back blowing, and the front process sprays calcium hydroxide desulfurizer, realizes the growth, modification and viscosity reduction of the micro silicon powder, and is more beneficial to back blowing, dust collection and sending to the subsequent process.

[0042] After the flue gas of the industrial silicon furnace is desulfurized and the metal filter bag is removed, it enters the high temperature SCR denitration device 7. The denitration temperature range is below 450 DEG C. Compared with the medium and low temperature SCR denitration, the denitration efficiency is relatively improved, the use of catalyst is reduced, and the denitration cost is reduced. If the temperature of the flue gas before denitration is higher than 450 DEG C, the temperature can be adjusted to below 450 DEG C by mixing air.

[0043] The flue gas after dust removal and denitration enters the waste heat boiler 8 for heat exchange, without facing the problem of ash removal, so the waste heat boiler can be continuously and efficiently operated for a long time without ash removal and reduction of heat exchange time. In the embodiment, the flue gas can be heat exchanged to below 150 DEG C through the waste heat boiler, so as to fully recover the heat in the flue gas.

[0044] Embodiment 2

[0045] The application provides an industrial silicon furnace flue gas comprehensive treatment process, as shown in Figure 3 As shown in the figure, the above system is used for treating the industrial silicon furnace flue gas, including the following steps:

[0046] Step (1): the flue gas of the industrial silicon furnace passes through the flue gas hood of the furnace and enters the flue gas guide pipe;

[0047] Step (2): calcium hydroxide desulfurizer is sprayed into the desulfurizer spraying inlet on the plurality of pipe sections of the flue gas leading pipe; room temperature air can also be sprayed into the first desulfurizer spraying inlet and the second desulfurizer spraying inlet of the first pipe section of the flue gas leading pipe, and the spraying amount of the room temperature air is 0-15,000 standard cubic meters per hour. Spraying the room temperature air can promote the rapid cooling of SiO at the contact interface and the conversion of SiO into SiO2 in a large amount of oxygen atmosphere, avoid the heat release of the conversion reaction at the subsequent position, sintering and then bonding and blocking the filter bag of the dust removal device, and cause the difficulty in cleaning the filter bag of the dust removal device; spraying the room temperature air can also promote the rapid conversion of liquid molten SiO2 and other substances in the flue gas into solid substances, and part of the substances fall back into the furnace, thereby reducing the burden of the dust removal device. The method can also prevent the flue gas leading pipe of industrial silicon from being occasionally blocked.

[0048] Step (3): the desulfurized flue gas then enters the dust removal device, and the microsilica powder is collected through the dust removal device.

[0049] Step (4): the flue gas after dust removal enters the high-temperature SCR denitration device.

[0050] Step (5): the flue gas after denitration enters the waste heat boiler for heat exchange, and is finally diffused through the chimney.

[0051] The flue gas particle content after the purification treatment by the above process is less than 10 mg / Nm 3 , the SO2 content is less than 30 mg / Nm 3 , the NO x content is less than 35 mg / Nm 3 , and the flue gas meets the direct emission standard.

[0052] Example 3

[0053] The application also provides a recycling method of the microsilica powder collected by the above process. In addition to the main component SiO2, the microsilica powder also contains calcium oxide, calcium sulfate, calcium sulfite and other substances.

[0054] The microsilica powder is used for producing manganese-silicon alloy, and the specific method comprises the following steps as shown in the figure: Figure 4

[0055] Step (1): finely grind the manganese ore, dolomite and bituminous coal to 150 mesh or less to obtain the ground material;

[0056] Step (2): proportion and mix the ground material in step (1) with the microsilica powder to obtain the mixed material; in the mixed material, the manganese ore accounts for 60-67% by weight, the dolomite accounts for 2.8-4.2% by weight, the bituminous coal accounts for 21-28% by weight, and the microsilica powder accounts for 9-14% by weight.

[0057] ​Step (3): the mixture of step (2) is preheated to 400-460℃. The bituminous coal is heated to soften, melt, flow, expand and thermally decompose, and has the property of being solidified and bonded after thermal decomposition, i.e. the cohesiveness of the coal; the microsilica is heated to increase the cohesiveness, so that the mixture can be solidified into pellets without adding additional bonding agents;

[0058] Step (4): the preheated material is fed into a pair of roller pelletizing devices to obtain hot-pressed pellets; the pellets have high strength, and the compressive strength is 1500N per pellet; the pellets can be suitable for smelting in a large-scale electric arc furnace, and the capacity of the electric arc furnace can be as high as 60000kVA or more;

[0059] Step (5): the hot-pressed pellets are fed into an electric arc furnace for smelting to obtain manganese-silicon alloy, slag and electric arc furnace gas, wherein the electric arc furnace gas can be combusted to serve as a heat source for preheating the mixture.

[0060] The microsilica utilization method provided in the embodiment is suitable for both the microsilica collected in the industrial silicon electric arc furnace flue gas comprehensive treatment system and process and the conventional microsilica. The method can be applied to treat 2 million tons of microsilica produced in China every year.

[0061] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An industrial silicon smelting furnace flue gas comprehensive treatment system, characterized in that, The system comprises, in sequence along the direction of flue gas flow, a flue gas leading pipe, a dust removal device, a high-temperature SCR denitration device, a waste heat boiler and a chimney; the flue gas leading pipe is provided in multiple sections, the first pipe section is a vertical section, the second pipe section is a vertical-to-horizontal turning section, the third pipe section is a horizontal section, and the fourth pipe section is a horizontal-to-inclined turning section; the first, second, third and fourth pipe sections are connected in sequence, the bottom of the first pipe section is connected to a smoke hood on the furnace body of the industrial silicon furnace, and the end of the fourth pipe section is connected to the dust removal device through a connecting pipe; each of the first, second, third and fourth pipe sections is provided with a desulfurizing agent injection port, and the particle size of the desulfurizing agent of the desulfurizing agent injection ports of the first, second, third and fourth pipe sections decreases in sequence.

2. The industrial silicon smelting furnace flue gas comprehensive treatment system according to claim 1, characterized in that, The first desulfurizing agent injection port and the second desulfurizing agent injection port are arranged at intervals in the vertical direction of the first pipe section, and each of the second, third and fourth pipe sections is provided with one desulfurizing agent injection port.

3. The industrial silicon smelting furnace flue gas comprehensive treatment system according to claim 2, characterized in that, The first desulfurizing agent injection port is located 1-4 m above the smoke hood, the second desulfurizing agent injection port is located 5-8 m above the smoke hood, and the desulfurizing agent injection port of the second pipe section is located 10-14 m above the smoke hood.

4. The industrial silicon smelting furnace flue gas comprehensive treatment system according to claim 2, characterized in that, The particle size of the desulfurizing agent of the first desulfurizing agent injection port and the second desulfurizing agent injection port is less than 8 mm; the particle size of the desulfurizing agent of the desulfurizing agent injection port of the second pipe section is less than 0.2 mm; the particle size of the desulfurizing agent of the desulfurizing agent injection port of the third pipe section is less than 0.074 mm; and the particle size of the desulfurizing agent of the desulfurizing agent injection port of the fourth pipe section is less than 0.02 mm.

5. The industrial silicon smelting furnace flue gas comprehensive treatment system according to claim 4, characterized in that, The hourly injection amount of the desulfurizing agent of the first desulfurizing agent injection port and the second desulfurizing agent injection port is 4-10 kg; the hourly injection amount of the desulfurizing agent of the desulfurizing agent injection port of the second pipe section is 4-10 kg; the hourly injection amount of the desulfurizing agent of the desulfurizing agent injection port of the third pipe section is 10-40 kg; and the hourly injection amount of the desulfurizing agent of the desulfurizing agent injection port of the fourth pipe section is 10-120 kg.

6. The industrial silicon smelting furnace flue gas comprehensive treatment system according to claim 1, characterized in that, The desulfurizing agent is calcium hydroxide; the dust removal device is a metal fiber filter bag dust remover; the temperature of the flue gas in the flue gas leading pipe is 400-800℃; the temperature range of the high-temperature SCR denitration device is below 450℃; and the temperature after heat exchange of the waste heat boiler is below 150℃.

7. A process for comprehensive treatment of flue gas from an industrial silicon smelting furnace, characterized in that, The industrial silicon furnace flue gas comprehensive treatment system of claim 1 is used to treat industrial silicon furnace flue gas, comprising the following steps: Step (1): the industrial silicon furnace flue gas passes through the smoke hood of the industrial silicon furnace and enters the flue gas leading pipe; Step (2): calcium hydroxide desulfurizing agent is injected into the desulfurizing agent injection ports on the multiple pipe sections of the flue gas leading pipe; Step (3): the desulfurized flue gas then enters the dust removal device, and the microsilica powder is collected by the dust removal device; Step (4): the dust-removed flue gas enters the high-temperature SCR denitration device; Step (5): the denitrated flue gas enters the waste heat boiler for heat exchange, and is finally diffused through the chimney.

8. The industrial silicon smelter off-gas comprehensive treatment process according to claim 7, characterized in that, Room temperature air is injected into the desulfurizing agent injection port of the first pipe section at an hourly injection amount of 0-15,000 standard cubic meters.

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