Process for renovating nitrogen oxide emission in carbon fiber manufacturing

Abstract

The invention relates to the technical field of nitrogen oxide emission, in particular to a process for regulating nitrogen oxide emission in carbon fiber manufacturing. The invention discloses a process for renovating nitrogen oxide emission in carbon fiber manufacturing, which comprises the following steps: sequentially carrying out incineration treatment and two-stage oxidation cyanide breaking absorption treatment on waste gas of an oxidation furnace by using a heat storage incinerator to obtain emission; and or the waste gas of the carbonization furnace is sequentially subjected to incineration treatment, primary denitration treatment, dust removal treatment and two-stage oxidation cyanide breaking absorption treatment through a direct-fired incinerator, and emissions are obtained. According to the technology for renovating nitrogen oxide emission in carbon fiber manufacturing, by optimizing the treatment technology, the waste gas treatment efficiency is improved, the treatment cost and energy consumption are reduced, remarkable economic benefits are brought to enterprises, nitrogen oxide and other harmful gases in waste gas are effectively removed, environmental pollution is reduced, and the economic benefit is increased. And human health and ecological balance are protected.

Description

Technical Field

[0001] The invention relates to the technical field of nitrogen oxide emissions, and in particular to a process for regulating nitrogen oxide emissions in carbon fiber manufacturing. Background Art

[0002] In the current carbon fiber manufacturing industry, with the expansion of production scale and continuous technological advancement, the problem of exhaust gas emissions has become increasingly prominent, especially nitrogen oxides (NO x ) has become a key factor restricting the green development of the industry. In the process of carbon fiber production, oxidation furnaces and carbonization furnaces, as key equipment, will produce a large amount of waste gas containing toxic and harmful gases such as nitrogen oxides and silicon dioxide under high temperature conditions. If these waste gases are not effectively treated and directly discharged into the atmosphere, they will seriously pollute the environment and have an immeasurable impact on human health and ecological balance.

[0003] At present, the control of nitrogen oxides in carbon fiber production mainly relies on incineration technologies such as regenerative thermal incineration (RTO) and direct-fired incinerators (TO), as well as denitrification technologies such as selective catalytic reduction (SCR) and non-selective catalytic reduction (SNCR). These technologies can reduce nitrogen oxide emissions to a certain extent, but there are still some technical problems and challenges as follows.

[0004] 1. In the existing denitrification technology, the reaction between ammonia and nitrogen oxides is not sufficient, resulting in ammonia escape, which not only reduces the denitrification efficiency but also may cause secondary pollution to the environment.

[0005] 2. The silicon-containing components in the oil on the raw silk will produce a large amount of silica dust during the high-temperature oxidation process; since the bag filter of the TO furnace can only filter larger particles, a large amount of nano-scale silica dust will escape, which will be deposited on the catalyst of the SCR reactor, covering the active sites, hindering the contact between the catalyst and the pollutants in the flue gas, thereby reducing the activity of the catalyst and affecting the treatment effect of nitrogen oxides. In addition, the escape of ammonia and silica dust may cause secondary pollution to the environment, increasing the difficulty and cost of subsequent treatment.

[0006] To this end, the present application provides a process for regulating nitrogen oxide emissions during carbon fiber manufacturing. Summary of the invention

[0007] In order to overcome the shortcomings of the prior art, the present application provides a process for controlling nitrogen oxide emissions in carbon fiber manufacturing. By optimizing the treatment process, the exhaust gas treatment efficiency is improved, the treatment cost and energy consumption are reduced, and significant economic benefits are brought to the enterprise. Nitrogen oxides and other harmful gases in the exhaust gas are effectively removed, reducing environmental pollution and protecting human health and ecological balance.

[0008] The technical solution adopted by this application to solve its technical problem is: A process for regulating nitrogen oxide emissions in carbon fiber manufacturing, comprising the following steps: treating the exhaust gas from an oxidation furnace by incineration in a regenerative incinerator and then by two-stage oxidation, cyanide breaking and absorption treatment to obtain emissions; And\or the waste gas from the carbonization furnace is successively treated by incineration in a direct-fired incinerator, primary denitrification, dust removal, and two-stage oxidation and cyanide breaking absorption to obtain emissions.

[0009] In some embodiments, the nitrogen oxides in the exhaust are less than 41 mg / m 3 .

[0010] In some specific embodiments, the oxidation furnace and the carbonization furnace are used for carbon fiber production.

[0011] In some specific embodiments, when the heat storage incinerator is performing incineration treatment, the combustion temperature is 900-950°C, the residence time is 1-2s, the switching air volume is 30-50%, the heat storage body is ceramic balls, and the oxygen content is 18-20%.

[0012] In some specific embodiments, when the direct-fired incinerator is performing incineration treatment, the combustion temperature is 800~1050°C, the oxygen content is 2~6%, and the negative pressure in the furnace of the direct-fired incinerator is -170Pa; the direct-fired incinerator is equipped with an in-furnace purge device, which purges and cleans the crystals once every 2 hours.

[0013] In some specific embodiments, the primary denitration treatment is to introduce the waste gas after the incineration treatment into the SNCR reactor for a primary denitration treatment; the temperature during the primary denitration treatment is 850~1100°C.

[0014] In some specific embodiments, a urea solution with a concentration of 5-10% is used in the SNCR reactor.

[0015] In some specific embodiments, the dust removal process is to use a bag filter to remove dust.

[0016] In some specific embodiments, the two-stage oxidation and cyanide destruction absorption treatment includes using a first-stage oxidation reactor for oxidation treatment and using a second-stage absorption tower for absorption treatment; The oxidant in the first-stage oxidation reactor includes sodium hypochlorite; the absorbent in the second-stage absorption tower includes an alkaline solution.

[0017] The beneficial effects of the present invention are: 1. The process described in this application uses a heat storage body to store heat in a heat storage incinerator to preheat the waste gas to be treated, thereby improving the incineration efficiency and reducing energy consumption; the waste gas after incineration is further purified by a two-stage oxidation and cyanide absorption device to ensure that harmful gases such as nitrogen oxides are effectively removed.

[0018] 2. In the process described in the present application, a direct-fired incinerator oxidizes and decomposes organic matter in the exhaust gas through high-temperature incineration, and reduces the concentration of pollutants; a primary denitrification treatment uses a reducing agent such as urea to reduce nitrogen oxides to nitrogen and water at high temperature, thereby reducing nitrogen oxide emissions; a bag filter is used to capture solid particulate matter in the exhaust gas, especially silica dust; finally, a two-stage oxidation and cyanide absorption device is used to completely remove harmful gases in the exhaust gas.

[0019] 3. The process described in this application improves the waste gas treatment efficiency, reduces the treatment cost and energy consumption by optimizing the treatment process, and brings significant economic benefits to the enterprise. Nitrogen oxides and other harmful gases in the waste gas are effectively removed, reducing environmental pollution and protecting human health and ecological balance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0021] Figure 1 A flow chart of a process for controlling nitrogen oxide emissions in carbon fiber manufacturing. DETAILED DESCRIPTION

[0022] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments, and the contents mentioned in the implementation modes are not intended to limit the present invention.

[0023] As used herein, "and / or" includes the term of any and all combinations of one or more associated listed items. The terms used herein are only used to describe specific embodiments and are not intended to limit the present invention. As used herein, the singular forms "a", "an", "an" and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It is further understood that "including", when used in this specification, specifies the stated features, integers, steps, operations, elements and / or compositions, but does not exclude the existence or addition of one or more other features, integers, steps, operations, elements, compositions and / or combinations thereof.

[0024] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. It is further understood that terms, such as defined in commonly used dictionaries, are interpreted in accordance with their meanings in the context of the relevant art and are not idealized or overly formal meanings unless explicitly defined as such herein.

[0025] The exemplary invention described herein may appropriately lack any one or more element limitations that are not specifically disclosed herein. Therefore, the terms "comprise", "include", "contain", etc. should be understood broadly and non-restrictively. In addition, the terminology used herein is used as a description, not a limitation, and it is unintentional to use these terminology expressions that do not include any equivalent characteristics, but only describe some of their characteristics, but various modifications are possible within the scope of the present invention according to the rights. Therefore, although the present invention has been specifically disclosed by preferred embodiments and optional features, the modifications disclosed herein to embody the changes of the present invention may be recorded by those skilled in the art, and such modifications and changes will be considered to be within the scope of the present invention.

[0026] In order to solve the ammonia escape problem and the silica dust escape problem, the present application provides the following Figure 1 A process for regulating nitrogen oxide emissions in carbon fiber manufacturing is shown, comprising the following steps: treating the exhaust gas from the oxidation furnace by incineration in a regenerative incinerator and then by two-stage oxidation, cyanide breaking and absorption treatment to obtain emissions; And\or the waste gas from the carbonization furnace is successively treated by incineration in a direct-fired incinerator, primary denitrification, dust removal, and two-stage oxidation and cyanide breaking absorption to obtain emissions.

[0027] Specifically, in some embodiments, when the heat storage incinerator performs incineration treatment, the combustion temperature is 900-950°C, the residence time is 1-2s, the switching air volume is 30-50%, the heat storage body is ceramic balls, and the oxygen content is 18-20%.

[0028] In this application, the combustion temperature is controlled at 900-950°C, and the organic matter and other combustible components in the exhaust gas can be burned quickly and fully, and converted into harmless substances such as carbon dioxide and water. At the same time, this temperature range also helps to suppress thermal NO x The residence time of 1~2s ensures that the waste gas has enough residence time in the incinerator to complete the combustion reaction and the conversion of pollutants; the residence time of the waste gas in the incinerator directly affects its combustion efficiency and the removal rate of pollutants. Too short a residence time may lead to incomplete combustion, while too long a residence time may increase energy consumption and equipment costs. Therefore, controlling the residence time to 1~2s can not only ensure combustion efficiency, but also take into account economy and environmental protection.

[0029] By controlling the switching air volume, the oxygen content in the incinerator can be adjusted, thereby affecting the conditions of the combustion reaction. Appropriate oxygen concentration helps the complete combustion of waste gas and reduces the thermal NO caused by excess oxygen. xThe switching air volume setting needs to be adjusted according to the specific exhaust gas composition and combustion conditions. Too low oxygen concentration may lead to incomplete combustion, while too high oxygen concentration may increase thermal NO x By controlling the oxygen content within the range of 18-20%, the combustible components in the exhaust gas can be fully burned and the generation of nitrogen oxides can be suppressed. This control can be achieved by adjusting the opening of the oxygen supply fan valve.

[0030] More specifically, the process of incineration treatment by the thermal storage incinerator is: The exhaust gas first passes through a pre-treatment device (such as a dust collector) to remove impurities such as particulate matter, and then enters the RTO preheater; in the preheater, the exhaust gas exchanges heat with the thermal storage body (ceramic balls), and the temperature gradually increases. At the same time, the thermal storage body releases the previously stored heat.

[0031] The preheated waste gas enters the incineration chamber and is incinerated at a set combustion temperature of 900~950℃ and a retention time of 1~2s. At this time, the combustible components in the waste gas are fully burned and converted into harmless substances. The waste gas after incineration is purified (such as two-stage oxidation and cyanide absorption) and then discharged into the atmosphere. At the same time, the heat generated during the incineration process is absorbed and stored again by the heat storage body to prepare for the next round of incineration process.

[0032] Specifically, in some embodiments, when the direct-fired incinerator is performing incineration treatment, the combustion temperature is 800~1050°C, the oxygen content is 2~6%, and the negative pressure in the furnace of the direct-fired incinerator is -170Pa; the direct-fired incinerator is equipped with an in-furnace purge device, which purges and cleans the crystals once every 2 hours.

[0033] In this application, the combustion temperature of the direct-fired incinerator is set within the range of 800~1050℃, and the combustible components in the exhaust gas can be fully burned to generate stable combustion products, such as carbon dioxide and water vapor, thereby greatly reducing the generation of harmful gases such as nitrogen oxides. The oxygen content is controlled between 2~6%, which not only ensures the oxygen supply during the combustion process, but also avoids excessive combustion and increased generation of nitrogen oxides due to excessive oxygen content.

[0034] The negative pressure in the furnace is set to -170Pa, which helps to maintain the stability of the airflow in the furnace and prevent the particles in the exhaust gas from settling in the furnace and causing blockage. At the same time, the negative pressure can also promote the uniform distribution of the exhaust gas in the furnace and improve the incineration efficiency; the furnace purge device is purged every 2 hours, which can effectively remove the crystals and dust accumulated on the inner wall and components of the furnace, and prevent the decrease in thermal efficiency and equipment failure caused by dust accumulation.

[0035] Specifically, in some embodiments, the primary denitration treatment is to introduce the waste gas after the incineration treatment into the SNCR reactor for primary denitration treatment; the temperature during the primary denitration treatment is 850-1100° C. A urea solution with a concentration of 5-10% is used in the SNCR reactor.

[0036] In this application, urea solution is sprayed into the high-temperature exhaust gas in the SNCR reactor. In the temperature range of 850~1100℃, urea will quickly decompose to produce ammonia and isocyanic acid (HNCO); this step is the initial stage of the SNCR denitrification process, and the ammonia produced by the decomposition is the main reducing agent for the subsequent reduction of nitrogen oxides; the ammonia and isocyanic acid produced by the decomposition further react with nitrogen oxides (NO x ) undergoes a reduction reaction, converting nitrogen oxides into harmless nitrogen.

[0037] Specifically, in some embodiments, the dust removal process is to use a bag filter to remove dust. In the present application, the dust removal process is performed by using a bag filter, and its main purpose is to remove particulate matter in the exhaust gas, including tiny dust that may still exist in the exhaust gas after being treated by the SNCR reactor. The bag filter uses the capture effect of porous filter materials to effectively separate dust from the gas through screening, inertial collision, electrostatic adsorption, diffusion and other mechanisms.

[0038] Specifically, in some embodiments, the two-stage oxidation cyanide destruction absorption treatment includes using a first-stage oxidation reactor for oxidation treatment and using a second-stage absorption tower for absorption treatment; The oxidant in the first-stage oxidation reactor includes sodium hypochlorite, potassium permanganate or ozone; the absorbent in the second-stage absorption tower includes alkaline solution, activated carbon and ion exchange resin.

[0039] In the present application, the first-stage oxidation reactor uses sodium hypochlorite as an oxidant. The oxidant has strong oxidizing properties and can react quickly with cyanide and other reducing substances in the exhaust gas to oxidize them into harmless or low-toxic substances, quickly destroy the cyanide structure in the exhaust gas, and provide more favorable conditions for subsequent absorption treatment.

[0040] The second stage absorption tower uses NaOH to absorb the acidic gases (such as CO2, NO x The second-stage absorption tower can further purify the waste gas, remove residual cyanide and other harmful substances, and ensure that the discharged waste gas meets environmental protection standards.

[0041] A process for controlling nitrogen oxide emissions during carbon fiber manufacturing is further described by the following examples.

[0042] Example 1 A process for regulating nitrogen oxide emissions in carbon fiber manufacturing, comprising: treating the exhaust gas from an oxidation furnace by incineration in a regenerative incinerator and then by two-stage oxidation, cyanide breaking and absorption treatment to obtain emissions; When the heat storage incinerator is performing incineration treatment, the combustion temperature is 900-950°C, the residence time is 1-2s, the switching air volume is 30-50%, the heat storage body is ceramic balls, and the oxygen content is 18-20%.

[0043] The two-stage oxidation and cyanide destruction absorption treatment comprises an oxidation treatment using a first-stage oxidation reactor and an absorption treatment using a second-stage absorption tower; the oxidant in the first-stage oxidation reactor comprises sodium hypochlorite; and the absorbent in the second-stage absorption tower comprises an alkaline solution.

[0044] The first stage oxidation reactor uses sodium hypochlorite as an oxidant. The second stage absorption tower absorbent includes sodium hydroxide solution, activated carbon, and ammonium ion adsorption resin.

[0045] Example 2 A process for controlling nitrogen oxide emissions in carbon fiber manufacturing includes sequentially treating the waste gas from a carbonization furnace by incineration in a direct-fired incinerator, primary denitration, dust removal, and two-stage oxidation and cyanide-breaking absorption to obtain emissions.

[0046] When the direct-fired incinerator is incinerating, the combustion temperature of zone one is 800-850°C, and that of zone two is 900-1050°C. The oxygen content is 2-6%, and the negative pressure of the furnace of the direct-fired incinerator is -170Pa. The direct-fired incinerator is equipped with an in-furnace purge device, which purges and cleans the crystals once every 2 hours.

[0047] The primary denitrification treatment is to introduce the waste gas after incineration treatment into the SNCR reactor for primary denitrification treatment; the temperature during the primary denitrification treatment is 850~1100℃, and a urea solution with a concentration of 5~10% is added.

[0048] The dust removal process is to use a bag dust collector to remove dust.

[0049] The exhaust gas from the oxidation furnace in Example 1 contains nitrogen oxides, volatile organic compounds (acrylonitrile, dimethyl sulfoxide, methyl acrylate, etc.), carbon monoxide, carbon dioxide, smoke and industrial dust; In Example 2, the carbonization furnace exhaust gas contains carbon monoxide, carbon dioxide, hydrocarbon gases (such as methane, ethylene, ethane, etc.), smoke and industrial dust; After treatment in Examples 1 and 2, the nitrogen oxides in the exhaust gas are less than 41 mg / m 3 .

[0050] The raw materials or reagents used in the embodiments of the present invention and / or the comparative examples are all purchased from mainstream manufacturers in the market. Those without indicating the manufacturer or the concentration are all analytically pure raw materials or reagents that can be routinely obtained, and there are no special restrictions as long as the expected effect can be achieved. The instruments and equipment used in this embodiment are all purchased from major manufacturers in the market, and there are no special restrictions as long as the expected effect can be achieved. If specific techniques or conditions are not indicated in this embodiment, the techniques or conditions described in the literature in this area or the product specifications are followed.

[0051] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention may also be implemented in other ways. Any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A process for regulating nitrogen oxide emissions in carbon fiber manufacturing, comprising the following steps: The exhaust gas from the oxidation furnace is incinerated in a regenerative incinerator and then treated by two-stage oxidation, cyanide destruction and absorption to obtain emissions; And\or the waste gas from the carbonization furnace is successively treated by incineration in a direct-fired incinerator, primary denitrification, dust removal, and two-stage oxidation and cyanide breaking absorption to obtain emissions.

2. The process according to claim 1, characterized in that The nitrogen oxides in the emissions are less than 41 mg / m 3 .

3. The process according to claim 1, characterized in that The oxidation furnace and the carbonization furnace are used for carbon fiber production.

4. The process according to claim 1, characterized in that When the heat storage incinerator is performing incineration treatment, the combustion temperature is 900-950°C, the residence time is 1-2s, the switching air volume is 30-50%, the heat storage body is ceramic balls, and the oxygen content is 18-20%.

5. The process according to claim 1, characterized in that When the direct-fired incinerator is incinerating, the combustion temperature is 800-1050°C, the oxygen content is 2-6%, and the negative pressure of the furnace of the direct-fired incinerator is -170Pa; the direct-fired incinerator is equipped with an in-furnace purge device, which purges and cleans the crystals once every 2 hours.

6. The process according to claim 1, characterized in that The primary denitration treatment is to introduce the waste gas after the incineration treatment into the SNCR reactor for a primary denitration treatment; the temperature during the primary denitration treatment is 850~1100℃.

7. The process according to claim 6, characterized in that A urea solution with a concentration of 5-10% is used in the SNCR reactor.

8. The process according to claim 1, characterized in that The dust removal process is to use a bag dust collector to remove dust.

9. The process according to claim 1, characterized in that The two-stage oxidation and cyanide destruction absorption treatment comprises using a first-stage oxidation reactor for oxidation treatment and using a second-stage absorption tower for absorption treatment.

10. The process according to claim 9, characterized in that The oxidant in the first-stage oxidation reactor includes sodium hypochlorite; the absorbent in the second-stage absorption tower includes an alkaline solution.

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