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详解工业废气治理技术的特点

作者: 来源: 日期:2016-7-23 10:25:24 人气:0 评论:0


     工业废气是大气污染物的重要来源,工业废气的高效治理显得非常重要,今天为大家介绍常见的六类工业废气的治理技术,再也不用为废气治理发愁了。

一、碳氢化合物的净化

  燃烧法

  用燃烧方法销毁有害气体、蒸气或烟尘,使其变为无害物质的过程,称为燃烧净化。燃烧净化时所发生的化学作用主要是燃烧氧化作用及高温下的热分解。

  目前在实际中使用的燃烧净化方法有直接燃烧和热力燃烧。对化工、喷漆、绝缘材料等行业的生产装置中所排出的有机废气,广泛采用了燃烧净化的手段。

  特点:用于净化那些可燃的或在髙温情况下可以分解的有害气体,还可以用来消除恶臭,回收热量。

  催化燃烧法

  即在催化剂作用下,使废气中的有害可燃组分完全氧化为CO2和H2O。由于绝大部分有机物均具有可燃烧性,因此催化燃烧法已成为净化含碳氧化合物废气的有效手段之一。

  目前催化燃烧法已应用于金属印刷、绝缘材料、漆包线、炼焦、油漆、化工等多种行业中净化有机废气。

  特点:因废气温度较高、有机物浓度较髙,对燃烧反应及热量回收有利,具有较好的经济效益,因此应用最为广泛。

  吸附法

  作为净化碳氢化合物废气的吸附剂有活性炭、硅胶、分子筛等,利用吸附剂对有机物进行吸附,其中应用最广泛、效果最好的吸附剂是活性炭。

  特点:

  ①可以相当彻底地净化废气,即可进行深度净化,特别是对于低浓度废气的净化比用其他方法显现出吏大的优势;

  ②在不使用深冷、髙压等手段下,可以有效地回收有价值的有机物组分。

  吸收法

  在对碳氢化合物废气进行治理的方法中,吸收法的应用不如燃烧法、催化燃烧法、吸附等广泛,特别是对使用有机溶剂的各种行业,如喷漆、绝缘材料、漆包线等的生产过程所排出的废气,还不能完全达到工业应用水平。

  影响应用的主要问题是合适的吸收剂的选择。

  目前在石油炼制及石油化的生产及储运中采用吸收法进行烃类气体的回收利用。

  冷凝法

  利用物质在不同温度下具有不同饱和蒸汽压这一物理性质,采用降低系统温度或提高系统压力的方法,使处于蒸汽状态的污染物冷凝并从废气中分离出来的过程。

  特点:

  冷凝净化法适用范围冷凝净化法适于在下列情况下使用。

  处理高浓度废气,特别是含有害物组分单纯的废气;

  作为燃烧与吸附净化的预处理;特别是有害物含量较高时,可通过冷凝回收的方法减轻后续净化装置的操作负担;

  处理含有大量水蒸气的高温废气。

  冷凝净化法所需设备和操作条件比较简单回收物质纯度髙。

  冷凝净化法对废气的净化程度受冷凝温度的限制,要求净化程度髙或处理低浓度废气时,需要将废气冷却到很低的温度,经济上不合算。


二、含硫废气的净制

  该法是使用粉状、粒状吸收剂,吸附剂或催化剂去除废气中的80%。

  优点:治理中无废水、废酸排出,减少了二次污染。

  缺点:脱硫效率较低,设备废大,操作要求髙。


       湿法脱硫

  该法是采用液体吸收剂如水或械溶液洗涂含S02的烟气,通过吸收去除其中的S02。由于使用不同的吸收剂可获得不同的副产物而加以利用,因此湿法脱硫是各国研究最多的方法。

  优点:湿法脱硫所用设备较简单,操作容易,脱硫效率较高。

  缺点:脱硫后烟气温度较低,于烟囱排烟扩散不利。


三、含H2S废气的净制

       干法脱硫

  干法是利用的还原性和可燃性,以固体氧化剂或吸附剂来脱硫,或者直接使之燃烧。干法脱硫是以氧气使H2S氧化成硫或硫氧化物的一种方法,也可称为干式氧化法。

  常用的有改进的克劳斯法、氧化铁法、活性碳吸附法、氧化锌法和卡太苏耳法。

  所用的脱硫剂、催化剂有活性炭、氧化铁、氧化锌、二氧化锰及铝矾土,此外还有分子筛、离子交换树脂等。一般可回收硫、二氧化硫、硫酸和硫酸盐。


  吸收剂有甲醇、碳酸丙烯酯、聚乙二醇二甲醚等,不仅能脱除硫化氢,氧硫化碳、二硫化碳等,溶液可以再生,并将硫化氢回收,而且也能选择性地吸收二氧化碳。


  化学吸收法


  常用的有氨水催化法及改良蒽醌二磺酸法(砷碱法因溶液有毒已较少采用)。


四、NOx废气的净制

  烟气脱硝

  在烟气净化技术上控制NOx排放,目前主要方法有选择性非催化还原SNCR、选择性催化还原SCR、低氮燃烧技术和电子束照射法、臭氧氧化法、吸附法、氧化吸收法等。其中,选择性非催化还原SNCR、选择性催化还原SCR,低氮燃烧,臭氧氧化法等技术已商业化。


五、含卤素废气的净制

  1、含氟废气的净制

  该法是以粉状的吸附剂吸附废气中的氟化物。该净化方法首先是烟气与吸附剂的接触,完成吸附过程;二是烟气与吸附剂分开。该过程都是在吸附设备中完成的。

  特点:净化效率高、工艺简单、没有水的二次污染,也不受各种气候的影响,但净化设备的体积较大。

  吸收法

  该法是用水、减性溶液或某些盐类溶液来吸收含氟废气中的氟化物,从而达到净化回收的目的,同时还可以得到副产品氟硅酸、冰晶石、氟硅酸钠及氟硅脲等。

     水法吸收和碱吸收法是常用的两种方法。

  特点:净化工艺过程可以连续操作和回收各种氟化物,净化效率高、效果好;其缺点是会造成二次污染,在寒冷地区还需保温措施。

  稀释法

  是向含氟气体的厂房送新鲜空气或将含氟废气向高空排放进行自然稀释。这种方法一般不采用。


  2、含氯废气的净制

  含氯废气的治理主要是通过湿法来净化,一般是采用化学中和法、氧化还原法等过程对废气进行吸收,作到综合利用。

  碱液中和法

  即以碱液作为吸收液对氯气进行吸收,常用的吸收剂有氢氧化钠溶液、碳酸钙溶液、石灰乳溶液等。

  硫酸亚铁或氯化亚铁吸收法

  该方法以氯化亚铁或硫酸亚铁作为吸收剂,据氧化还原反应性质对氯气进行回收与净化。其工艺设备可采用填料塔,并以废铁屑作填料,生产的三氯化铁可作为防水剂,三价铁可被铁屑还原,再次参与吸收反应。

  特点:该方法设备简单,操作容易,废铁屑来源丰富,技术合理;但反应速度比中和法要慢,效率较低。


  四氯化碳吸收法

  当氯气浓度大于1%时,可采用四氯化碳为吸收剂,其设备可采用喷淋或填充塔,在吸收塔内将氯的吸收液通过加热或吹脱解吸回收的氯气可再次使用。

  水吸收法

  当氯气浓度<1%时,有时可用水通过喷淋塔来吸收氯气,其效果不如碱性中和法好。用水蒸气加热解吸时可回收氯气,如国内的一些氯碱厂在“氯水”解吸时用蒸气或热交换方法回收氯气。

  此外,还有用硅胶、活性炭、离子交換树脂等进行吸附的方法,但因成本太高或是技术还不十分成熟而没有得到广泛的应用。


六、氯化氢废气的净制

  水吸收法

  处理氯化氢主要采用水吸收法。水吸收法是基于气体易溶于水的原理常常采用水直接吸收氯化氢气体。当所得氯化氢溶液达到一定浓度时,经净化浓缩可得到副产品盐酸。

  同时,处理氯化氢废气还有碱液吸收法,联合吸收法以及冷凝法。


  

Industrial emissions is an important source of atmospheric pollutants, efficient treatment of industrial waste gas is very important today to introduce common governance six industrial gas technology, no longer have to worry about gas treatment.


A hydrocarbon purification


Combustion


Combustion method to destroy harmful gases, vapors or dust, it becomes harmless substances in the process, called combustion purification. Chemical reaction that occurs when combustion purification mainly thermal combustion oxidation and high temperature decomposition.


Currently combustion purification methods used in practice have a direct combustion and heat of combustion. Chemical, paint, insulation materials and other industries in the production unit of organic waste discharged, a widely used means of combustion purification.


Features: for purifying harmful gas or in the case of Gao temperature can break those flammable, can also be used to eliminate odor, heat recovery.


Catalytic combustion


That is in the catalyst, the exhaust gas harmful combustible components are completely oxidized to CO2 and H2O. Since most organic compounds have can burn, therefore the catalytic combustion has become one of the effective means to purify exhaust gases containing carbon and oxygen compounds.


Currently catalytic combustion method has been applied to the metal printing, insulation materials, wire, coke, paint, chemical and other industries in the organic waste gas purification。


Features: Due to the higher exhaust gas temperature, concentration of organic matter than the Gao, the combustion reaction and heat recovery favorable, with good economic and therefore the most widely used。


Adsorption


As the exhaust gas purifying hydrocarbon adsorbent activated carbon, silica gel, molecular sieve, using an adsorbent for adsorption of organic matter, including the most widely used, the best effect is activated carbon adsorbent.


Features:


① can be quite thoroughly purify exhaust gas, deep purification can be carried out, especially for the low-concentration exhaust gas purification using other methods show Officials large odds ratio;


② without the use of deep cold, under pressure of Gao and other means to effectively recover valuable organic components。


Absorption


On hydrocarbons in the exhaust gas treatment method, absorption method of application is better combustion, catalytic combustion, adsorption and so widely, particularly on the use of organic solvents in a variety of industries, such as painting, insulation materials, wire and other production processes the exhaust gas, it can not fully meet the level of industrial application.


The main issues affecting the application of suitable absorbent choice。


Currently recycling hydrocarbon gas absorption method using the oil refining and petrochemical production and storage and transportation.


Condensation method


The use of material having different saturation vapor pressure at different temperatures, the physical properties, the use of lower system temperature or pressure of the system to improve the ways in which the condensed contaminants in the vapor state and separated from the exhaust gas process.


Features:


Condensate purification method scope condensate purification method is suitable for use in the following cases.


Treatment of high concentration waste gas, particularly those containing harmful components of exhaust gas alone;


As a pretreatment of the combustion and adsorption clarifier; especially when high content of harmful substances, can reduce the operational burden of the subsequent purification by means of condensation recovery method;


Processing of high temperature exhaust gas containing a large amount of water vapor。


Condensate purification method required equipment and operating conditions are relatively simple purity of recovered material Gao.


Condensate purification method for purifying exhaust gas is limited by the degree of condensation temperature required degree of purification or treatment Gao low concentration waste gas, the waste gas needs to be cooled to very low temperatures, economically viable.


Second, the net sulfur exhaust system


This method is the use of powdered, granular absorbents, adsorbents or catalyst removal in the exhaust gas of 80%.


Advantages: No waste water treatment, waste acid discharge, reduce the secondary pollution.


Disadvantages: desulfurization efficiency is low, large waste facilities, operating requirements Gao.




Wet desulfurization


The method is the use of a liquid absorbent, such as water or mechanical wash coat solution containing S02 flue gas by absorption to remove one of the S02. Due to the use of different absorbent obtain different by-products and take advantage of, so wet desulphurization was the most national research method.


Advantages: wet desulfurization equipment used is relatively simple, easy to operate, high desulfurization efficiency.


Disadvantages: low temperature flue gas desulfurization, chimney smoke diffusion in the negative.



Third, the exhaust gases containing H2S net system


Dry desulfurization


Dry method is the use of combustible and reducing to an oxidizing agent or a solid adsorbent desulfurization, or simply to make it burn. Dry desulfurization make H2S is oxidized to sulfur oxygen or sulfur oxides a method, also known as dry oxidation method.


Commonly used to improve the Claus process, iron oxide method, activated carbon adsorption, zinc oxide and chi too Su ear method.


The desulfurization agent used, catalysts are activated carbon, iron oxide, zinc oxide, manganese dioxide and bauxite, in addition to molecular sieves, ion exchange resins and the like. Usually recoverable sulfur, sulfur dioxide, sulfuric acid and sulfates.


Absorbents, methanol, propylene carbonate, polyethylene glycol dimethyl ether, etc。, not only to remove hydrogen sulfide, carbonyl sulfide, carbon disulfide, the solution can be regenerated and recycled hydrogen sulfide, but also capable of selectively removing carbon dioxide 。


Chemical absorption


Commonly used ammonia catalytic anthraquinone disulfonic acid and Improvement Act (arsenic soda solution because toxic has been less used)。


Fourth, the net made NOx exhaust gas


Flue gas denitrification


In the flue gas purification technology to control NOx emissions, the main method of selective non-catalytic reduction SNCR, selective catalytic reduction SCR, low NOx combustion technology and electron beam irradiation, ozone oxidation, adsorption, absorption oxidation method. Wherein the selective non-catalytic reduction SNCR, selective catalytic reduction SCR, low NOx combustion, ozone oxidation technology has been commercialized.


Fifth, the halogen-containing exhaust gases net system


1, net made of fluorine gas


The method is based on powdered adsorbent exhaust gas fluoride。 The flue gas purification method first contact with the adsorbent, the adsorption process is completed; the second is separated from the flue gas with the adsorbent。 This process is done in the adsorption device。


Features: high purification efficiency, simple process, no secondary pollution of water, is not affected by all kinds of weather, but the larger the volume of purification equipment.


Absorption


The law is water, some subtractive solution or salt solution to absorb fluoride fluorine-containing exhaust gas, so as to achieve the purpose of purification and recovery, but also can be a by-product fluosilicic acid, cryolite, sodium fluoride and silicon fluoride urea or the like.


Water absorption and alkali absorption method is commonly used in two ways.


Features: purification process can be operated continuously and recycling of fluorides, high purification efficiency, good effect; the drawback is cause secondary pollution, insulation measures needed in cold areas.


Dilution


Fresh air is sent to a gas containing fluorine or fluorine-containing gas plant to high-altitude emissions for natural dilution. This method is generally not used.


2, net made of chlorine gas


Chlorine gas governance mainly through wet to purify, is generally used in the chemical process and method, redox method of gas absorption, utilization done.


Lye and law


Namely lye as the absorbing liquid to absorb chlorine, sodium hydroxide solution commonly used absorbent, sodium carbonate solution, lime solution and the like。


Ferrous sulfate or ferrous chloride absorption method


In this method, ferrous chloride or ferrous sulfate as an absorbent, according to the nature of the redox reaction of chlorine gas is recovered and purified. Its process equipment can be packed towers, and scrap iron as a filler, the production of ferric chloride can be used as a waterproofing agent, ferric iron can be reduced again to participate in the absorption reactions.


Features: This method is simple equipment, easy to operate, a rich source of scrap iron, technically sound; but the reaction rate is slower than the neutralization method, less efficient.


CTC Absorption Spectrometry


When the chlorine concentration is greater than 1%, it can be used as absorbent carbon tetrachloride, which can be spray equipment or packed column, in the absorber absorbing liquid chlorine by heating or stripping desorption recycling of chlorine can be used again.


Water Absorption Spectrometry


When the chlorine concentration of <1%, sometimes by spraying water tower to absorb chlorine, are less effective than alkaline and good law. Recyclable chlorine by heating the desorption of water vapor, such as some domestic chlor-alkali plants in the "chlorine" desorption-recovery steam or heat exchange process chlorine.


In addition, there were adsorption method using silica gel, activated carbon, ion exchange resin, but the cost is too high or the technology is not very mature and has not been widely used.


Sixth, the net hydrogen chloride gas


Water Absorption Spectrometry


Mainly deal with hydrogen chloride water absorption. Water absorption principle is soluble in water-based gas is often used water directly absorb hydrogen chloride gas. When the resulting hydrogen chloride solution reaches a certain concentration, purified and concentrated hydrochloric acid by-product can be obtained.


At the same time, the process of hydrogen chloride gas as well as alkali absorption method, combined with absorption and condensation。


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