概述有机废气处理技术的优缺点 The advantages and disadvantages of organic waste gas treatment technology

挥发性的有机化合物，简称为VOC(VolatileOrganic Compounds))，在工业生产中，通常作为溶剂来使用，使用之后便散发到大气中。现阶段，其应用比较广泛的领域包括石油化工、印刷、人造革及电子元器件、烤漆和医药等。

从化学物质的性质来看，在工业生产等领域，一般用作溶剂的主要包括脂肪族化合物、卤代烃和芳香族化合物等。这些有机溶剂如果挥发到大气环境中，不仅会对大气环境造成严重污染，而且人体呼入被污染的气体后，对人体健康产生危害。比如苯，它常常被当作一种溶剂来使用，作为溶剂挥发到大气环境中，不仅可以被人体的皮肤所吸收，而且还可通过呼吸系统进入人体内部，造成慢性或急性中毒，不过人体的大部分中毒均是由于呼入有毒气体造成的。

苯类化合物不仅会对人体的中枢神经造成一定的损害，而且还可能造成神经系统的障碍，进入人体后还会危害血液和造血器官，如果情况比较严重，甚至会有出血症状或患上败血症。氧化作用下，苯在生物体内可氧化成苯酚，从而造成肝功能异常，对骨骼的生长发育十分不利，诱发再生障碍性贫血。如果苯蒸汽浓度过高，生物可能因急性中毒而死亡。因此，ACGIH把苯列为潜在致癌物质。卤代烃类化合物会引发神经症候群和血小板的减少、肝脾肿大等不良状况，而且很有可能致癌。所以，必须控制VOC的排放，这不仅是对环境负责，也是对我们的生命健康负责。

当前，VOC废气处理技术主要包括热破坏法、变压吸附分离与净化技术、吸附法和氧化处理方法等。

热破坏法

热破坏法是指直接和辅助燃烧有机气体，也就是VOC，或利用合适的催化剂加快VOC的化学反应，最终达到降低有机物浓度，使其不再具有危害性的一种处理方法。

热破坏法对于浓度较低的有机废气处理效果比较好，因此，在处理低浓度废气中得到了广泛应用。这种方法主要分为两种，即直接火焰燃烧和催化燃烧。直接火焰燃烧对有机废气的热处理效率相对较高，一般情况下可达到 99%。而催化燃烧指的是在催化床层的作用下，加快有机废气的化学反应速度。这种方法比直接燃烧用时更少，但是如果离开催化剂辅助，则无法发挥作用。现阶段，可作为催化剂使用的大都是金属、金属盐。这两种催化剂的催化效果虽说比较好，技术也已经相当成熟，但是其价格却比较高，所以处理成本也就比较高。近年来，催化剂研制多集中在非贵金属催化剂方向，取得了比较大的进展。

此外，在催化有机废气过程中，还需要有催化剂的载体，其起着提高催化活性和稳定性的重要作用。当前，多以陶瓷作为催化剂载体，但在未来的催化剂研究当中，应加快研发高效活性催化剂及其载体。

吸附法

有机废气中的吸附法主要适用于低浓度、高通量有机废气。现阶段，这种有机废气的处理方法已经相当成熟，能量消耗比较小，但是处理效率却非常高，而且可以彻底净化有害有机废气。

但是这种方法也存在一定缺陷，它需要的设备体积比较庞大，而且工艺流程比较复杂;如果废气中有大量杂质，则容易导致工作人员中毒。所以，使用此方法处理废气的关键在于吸附剂。当前，采用吸附法处理有机废气，多使用活性炭，主要是因为活性炭细孔结构比较好，吸附性比较强。

此外，经过氧化铁或臭氧处理，活性炭的吸附性能将会更好，有机废气的处理将会更加安全和有效。

生物处理法

从处理的基本原理上讲，采用生物处理方法处理有机废气，是使用微生物的生理过程把有机废气中的有害物质转化为简单的无机物，比如CO2、H2O和其它简单无机物等。这是一种无害的有机废气处理方式。

一般情况下，一个完整的生物处理有机废气过程包括3个基本步骤：a) 有机废气中的有机污染物首先与水接触，在水中可以迅速溶解;b) 在液膜中溶解的有机物，在液态浓度低的情况下，可以逐步扩散到生物膜中，进而被附着在生物膜上的微生物吸收;c) 被微生物吸收的有机废气，在其自身生理代谢过程中，将会被降解，最终转化为对环境没有损害的化合物质。

变压吸附分离与净化技术

变压吸附分离与净化技术是利用气体组分可吸附在固体材料上的特性，在有机废气与分离净化装置中，气体的压力会出现一定的变化，通过这种压力变化来处理有机废气。

PSA 技术主要应用的是物理法，通过物理法来实现有机废气的净化，使用材料主要是沸石分子筛。沸石分子筛，在吸附选择性和吸附量两方面有一定优势。在一定温度和压力下，这种沸石分子筛可以吸附有机废气中的有机成分，然后把剩余气体输送到下个环节中。在吸附有机废气后，通过一定工序将其转化，保持并提高吸附剂的再生能力，进而可让吸附剂再次投入使用，然后重复上步骤工序，循环反复，直到有机废气得到净化。

近年来，该技术开始在工业生产中应用，对于气体分离有良好效果。该技术的主要优势有：能源消耗少、成本比较低、工序操作自动化及分离净化后混合物纯度比较高、环境污染小等。使用该技术对于回收和处理有一定价值的气体效果良好。

氧化法

对于有毒、有害，而且不需要回收的VOC，热氧化法是最适合的处理技术和方法。氧化法的基本原理：VOC与O2发生氧化反应，生成CO2和H2O，化学方程式如下：

aCxHyOz+bO2→cCO2+dH2O

从化学反应方程式上看，该氧化反应和化学上的燃烧过程相类似，但其由于VOC浓度比较低，在化学反应中不会产生肉眼可见的火焰。一般情况下，氧化法通过两种方法可确保氧化反应的顺利进行：a) 加热。使含有VOC的有机废气达到反应温度;b) 使用催化剂。如果温度比较低，则氧化反应可在催化剂表面进行。所以，有机废气处理的氧化法分为以下两种方法：

a) 催化氧化法。现阶段，催化氧化法使用的催化剂有两种，即贵金属催化剂和非贵金属催化剂。贵金属催化剂主要包括Pt、Pd等，它们以细颗粒形式依附在催化剂载体上，而催化剂载体通常是金属或陶瓷蜂窝，或散装填料;非贵金属催化剂主要是由过渡元素金属氧化物，比如MnO2，与粘合剂经过一定比例混合，然后制成的催化剂。为有效防止催化剂中毒后丧失催化活性，在处理前必须彻底清除可使催化剂中毒的物质，比如Pb、Zn和Hg等。如果有机废气中的催化剂毒物、遮盖质无法清除，则不可使用这种催化氧化法处理VOC;

b) 热氧化法。热氧化法当前分为三种：热力燃烧式、间壁式、蓄热式。三种方法的主要区别在于热量回收方式。这三种方法均能催化法结合，降低化学反应的反应温度。

技术的发展方向。

热力燃烧式热氧化器，一般情况下是指气体焚烧炉。这种气体焚烧炉由助燃剂、混合区和燃烧室三部分组成。其中，助燃剂，比如天然气、石油等，是辅助燃料，在燃烧过程中，焚烧炉内产生的热混合区可对VOC废气预热，预热后便可为有机废气的处理提供足够空间、时间，最终实现有机废气的无害化处理。

在供氧充足条件下，氧化反应的反应程度——VOC去除率——主要取决于“三T条件”：反应温度(Temperat)、时间(Time)、湍流混合情况(Turbulence)。这“三T条件”是相互联系的，在一定范围内，一个条件的改善可使另外两个条件降低。热力燃烧式热氧化器的缺点在于：辅助燃料价格高，导致装置操作费用比较高。

间壁式热氧化器指的是在热氧化装置中，加入间壁式热交换器，进而把燃烧室排出气体的热量传送给氧化装置进口处温度比较低的气体，预热完成后便可促成氧化反应。现阶段，间壁式热交换器的热回收率最高可达85%，因此大幅降低了辅助燃料的消耗。一般情况下，间壁式热交换器有三种形式：管式、壳式和板式。由于热氧化温度必须控制在800 ℃～1 000 ℃范围内，因此，间壁式热交换必须由不锈钢或合金材料制成。所以间壁式热交换器的造价相当高，而这也是其缺点所在。此外，材料的热应力也很难消除，这是间壁式热交换的另外一个缺点。

蓄热式热氧化器，简称为RTO，在热氧化装置中计入蓄热式热交换器，在完成VOC预热后便可进行氧化反应。现阶段，蓄热式热氧化器的热回收率已经达到了95%，且其占用空间比较小，辅助燃料的消耗也比较少。由于当前的蓄热材料可使用陶瓷填料，其可处理腐蚀性或含有颗粒物的VOC气体。

现阶段，RTO装置分为旋转式和阀门切换式两种，其中，阀门切换式是最常见的一种，由2个或多个陶瓷填充床组成，通过切换阀门来达到改变气流方向的目的。

液体吸收法

液体吸收法指的是通过吸收剂与有机废气接触，把有机废气中的有害分子转移到吸收剂中，从而实现分离有机废气的目的。这种处理方法是一种典型的物理化学作用过程。有机废气转移到吸收剂中后，采用解析方法把吸收剂中有害分子去除掉，然后回收，实现吸收剂的重复使用和利用。

从作用原理的角度划分，此方法可分为化学方法和物理方法。物理方法是指利用物质之间相溶的原理，把水看作吸收剂，把有机废气中的有害分子去除掉，但是对于不溶于水的废气，比如苯，则只能通过化学方法清除，也就是通过有机废气与溶剂发生化学反应，然后予以去除。

冷凝回收法

在不同温度下，有机物质的饱和度不同，冷凝回收法便是利用有机物这一特点来发挥作用，通过降低或提高系统压力，把处于蒸汽环境中的有机物质通过冷凝方式提取出来。冷凝提取后，有机废气便可得到比较高的净化。其缺点是操作难度比较大，在常温下也不容易用冷却水来完成，需要给冷凝水降温，所以需要较多费用。这种处理方法主要适用于浓度高且温度比较低的有机废气处理。

有机废气处理除上述处理方法之外，还包括高温及触媒燃烧法、活性炭吸附法、臭氧分解法和电化学氧化法等。这些方法均适用于有机废气处理，但具体采用何种方法，则取决于废气浓度、设备装置和环境温度等条件。此外，还需要考虑操作人员的操作水平。

当前，中国的工业发展进入到了一个新阶段，环境问题的日益突出影响到了人们的正常工作和生活，环境问题越来越受到人们的关注。所以在这种形势下，必须控制工业等生产领域有害气体的排放，减少其对大气环境的污染。在本文中，主要探讨了VOC废气处理的相关技术，主要包括冷凝处理法、氧化处理法、液体吸附法、生物处理法和吸附法等。

上海永爱健净化设备有限公司专业提供VOCs净化设备及技术。致力成为一家集研发设计、设备制造、工程承包及运营管理于一体的企业。公司拥有环境污染治理总承包资质、环境工程专项设计及多个相关专利证书，是环保协会会员单位。

Volatile organic Compounds, referred to as VOC (VolatileOrganic come)), in industrial production, often used as solvent, use after they send out into the atmosphere. At present, it is widely used in the fields of petrochemical, printing, artificial leather and electronic components, baking varnish and medicine.

From the nature of chemical substances, in the field of industrial production, commonly used as solvent mainly include aliphatic compounds, halogenated hydrocarbons and aromatic compounds. If these organic solvents evaporate into the atmospheric environment, they will not only cause serious pollution to the atmospheric environment, but also cause harm to human health after the human body exhales into the polluted gas. Benzene, for example, is often used as a solvent to evaporate into the atmosphere as a solvent, not only absorbed by the skin of the human body, but also into the body through the respiratory system, causing chronic or acute poisoning, although most of human poisoning is caused by inhaling toxic gases.
Benzene compounds can not only cause certain damage to the central nervous system of the human body, but also cause neurological disorders. After entering the human body, they can also harm blood and hematopoietic organs. If the situation is serious, they may even have bleeding symptoms or have sepsis. Under the action of oxidation, benzene can be oxidized into phenol in organisms, resulting in abnormal liver function, which is very adverse to the growth and development of bones and induces aplastic anemia. If the concentration of benzene vapor is too high, organisms may die from acute poisoning. So, ACGIH listed benzene as a potential carcinogen. Halogenated hydrocarbons can cause neurologic syndromes and thrombocytopenia, hepatosplenomegaly and other adverse conditions, and are likely to cause cancer. Therefore, VOC emission must be controlled, which is not only responsible for the environment, but also for our life and health.

Currently, VOC waste gas treatment technologies mainly include thermal damage, pressure swing adsorption separation and purification, adsorption and oxidation treatment.
Thermal destruction method
Thermal damage method refers to a treatment method of directly and auxiliary combustion of organic gases, namely VOC, or using appropriate catalysts to accelerate the chemical reaction of VOC, and finally to reduce the concentration of organics so that it is no longer hazardous.
The thermal destruction method has a better treatment effect on organic waste gas with low concentration, so it has been widely used in the treatment of low concentration waste gas. This method is mainly divided into two types, direct flame combustion and catalytic combustion. The heat treatment efficiency of direct flame combustion on organic waste gas is relatively high, generally reaching 99%. Catalytic combustion refers to accelerating the chemical reaction of organic waste gas under the action of catalytic bed. This method takes less time than direct combustion, but it doesn't work without the help of a catalyst. At present, most of metals and metal salts can be used as catalysts. The two catalysts have good catalytic effect and mature technology, but their price is relatively high, so the processing cost is relatively high. In recent years, the research and development of catalysts mainly focus on non-noble metal catalysts, and great progress has been made.
In addition, in the process of catalytic organic waste gas, a catalyst carrier is needed, which plays an important role in improving catalytic activity and stability. At present, ceramic is often used as catalyst carrier, but in the future research on catalysts, the research and development of high-efficiency active catalysts and their supports should be accelerated.
Adsorption method
The adsorption method in organic waste gas is mainly applied to low concentration and high flux organic waste gas. At the present stage, the treatment method of organic waste gas is quite mature, with relatively low energy consumption, but the treatment efficiency is very high, and the harmful organic waste gas can be completely purified.
However, this method also has some defects. It requires large equipment and complicated technological process. If there are a lot of impurities in the waste gas, it is easy to cause staff poisoning. Therefore, the key to use this method to treat waste gas is adsorbent. At present, the adsorption method is adopted to treat organic waste gas, and activated carbon is mostly used, mainly because of its better pore structure and strong adsorption.
In addition, after iron oxide or ozone treatment, the adsorption performance of activated carbon will be better, and the treatment of organic waste gas will be more safe and effective.
Biological treatment
Based on the basic principle of treatment, biological treatment of organic waste gas is to use the physiological process of microorganisms to transform harmful substances in organic waste gas into simple inorganic substances, such as CO2, H2O and other simple inorganic substances. This is a harmless organic waste gas treatment.
In general, a complete biological treatment of organic waste gas process includes three basic steps: a) the organic pollutants in organic waste gas first contact with water and can be dissolved in water quickly; B) organics dissolved in the liquid membrane can be gradually diffused into the biofilm at a low liquid concentration, and then absorbed by microorganisms attached to the biofilm; C) organic waste gas absorbed by microorganisms will be degraded in the process of their own physiological metabolism, and eventually converted into a compound that is not harmful to the environment.
Pressure swing adsorption separation and purification technology
Pressure swing adsorption separation and purification technology makes use of the characteristics that gas components can be adsorbed on solid materials. In the organic waste gas and separation and purification equipment, the pressure of gas will change to a certain extent, and the organic waste gas will be treated with this pressure change.
PSA technology mainly applies physical method to achieve the purification of organic waste gas through physical method, and the material used is mainly zeolite molecular sieve. Zeolite has advantages in adsorption selectivity and adsorption quantity. At a given temperature and pressure, the zeolite can absorb the organic components of the waste gas and transfer the remaining gas to the next step. After absorbing organic waste gas, the adsorbent can be converted through a certain process to maintain and improve the regeneration capacity of the adsorbent, so that the adsorbent can be put into use again, and then the procedure is repeated and repeated until the organic waste gas is purified.
In recent years, this technology has been applied in industrial production and has good effect on gas separation. The main advantages of the technology include low energy consumption, low cost, automation of process operation, high purity of mixture after separation and purification, and low environmental pollution. The use of this technology is good for the recovery and treatment of valuable gases.
oxidation
Thermal oxidation is the most suitable treatment technology and method for toxic, harmful and non-recyclable VOC.The basic principle of oxidation method: VOC reacts with O2 to generate CO2 and H2O. The chemical equation is as follows:
ACxHyOz + bO2 - cCO2 + dH2O
From the chemical reaction equation, the oxidation reaction is similar to the chemical combustion process, but due to low VOC concentration, no visible flame will be generated in the chemical reaction. Generally, two methods are used to ensure the smooth operation of the oxidation reaction: a) heating. Bring the organic waste gas containing VOC to the reaction temperature; B) use a catalyst. If the temperature is low, the oxidation reaction can be carried out on the surface of the catalyst. Therefore, the oxidation method for organic waste gas treatment is divided into the following two methods:
A) catalytic oxidation. At present, there are two kinds of catalysts used in catalytic oxidation, namely noble metal catalyst and non-noble metal catalyst. Precious metal catalysts mainly include Pt, Pd, etc., which are attached to the catalyst carrier in the form of fine particles. The catalyst carrier is usually metal or ceramic honeycomb, or bulk packing. Non-noble metal catalysts are mainly catalysts made by mixing transition element metal oxides, such as MnO2, with a certain proportion of adhesive. In order to effectively prevent the loss of catalytic activity after catalyst poisoning, materials that can poison the catalyst, such as Pb, Zn and Hg, must be thoroughly cleared before treatment. If the catalyst poison and covering in organic waste gas cannot be removed, this catalytic oxidation method cannot be used to deal with VOC.
B) thermal oxidation. Thermal oxidation is currently divided into three types: thermal combustion type, wall type and heat storage type. The main difference between the three methods is the way heat is recovered. All three methods can be combined by catalytic method to reduce the reaction temperature of chemical reaction.
The direction of technology.
Thermal combustion type thermal oxidizer generally refers to gas incinerator. The gas incinerator consists of three parts: the booster, the mixing area and the combustion chamber. In the process of combustion, the heat mixing zone generated in the incinerator can preheat VOC waste gas. After preheating, sufficient space and time can be provided for the treatment of organic waste gas, and finally the harmless treatment of organic waste gas can be realized.
Under sufficient oxygen supply conditions, the degree of reaction of oxidation reaction -- VOC removal rate -- mainly depends on the "three T conditions" : reaction temperature, Time and Turbulence mixing. These "three T conditions" are related to each other. Within a certain range, the improvement of one condition can reduce the other two conditions. The disadvantage of thermal combustion type thermal oxidizer is that the cost of auxiliary fuel is high, resulting in relatively high operating cost of the device.
The interwall thermo-oxidizer refers to the process of adding the interwall heat exchanger in the thermal oxidation device to transfer the heat from the combustion chamber to the gas at the lower temperature at the inlet of the oxidation device. After preheating, the oxidation reaction can be promoted. At the present stage, the heat recovery rate of the wall heat exchanger is up to 85%, thus greatly reducing the consumption of auxiliary fuel. In general, there are three types of wall heat exchanger: pipe type, shell type and plate type. Due to the thermal oxidation temperature must be controlled within the scope of the 1 800 ℃ ~ 800 ℃, thus, recuperative heat transfer must be made of stainless steel or alloy materials. Therefore, the wall heat exchanger cost quite high, which is also its weakness. In addition, the thermal stress of materials is difficult to eliminate, which is another disadvantage of wall heat exchange.
The regenerative thermal oxidizer, or RTO for short, is included in the thermal oxidation device. After the VOC preheating is completed, the oxidation reaction can be conducted. At present, the recovery rate of regenerative thermal oxidizer has reached 95%, and it occupies less space and consumes less auxiliary fuel. As the current heat storage material can use ceramic packing, it can handle corrosive or VOC gas containing particulate matter.
At present, the RTO device is divided into two types: rotary type and valve switching type. Among them, valve switching type is the most common type, which is composed of two or more ceramic filling beds. By changing the valve, the purpose of air flow direction can be achieved.
Liquid absorption method
Liquid absorption refers to the transfer of harmful molecules from organic waste gas to the absorbent through the contact between absorbent and organic waste gas, so as to achieve the purpose of separating organic waste gas. This process is a typical physical and chemical process. After the organic waste gas is transferred to the absorber, the harmful molecules in the absorber are removed by analytical method, and then recycled to achieve the reuse and utilization of the absorber.
The method can be divided into chemical method and physical method. Physical method refers to using the principle of phase dissolution between substances, taking water as an absorbent, removing harmful molecules from organic waste gas. However, for the waste gas insoluble in water, such as benzene, it can only be removed by chemical method, that is, by chemical reaction between organic waste gas and solvent, and then removing.
Condensation recovery method
At different temperatures, the saturation of organic matter is different. The condensation recovery method takes advantage of the characteristics of organic matter to play its role. By reducing or increasing the system pressure, the organic matter in the steam environment is extracted through condensation. After condensation and extraction, the organic waste gas can be highly purified. The disadvantage is that the operation is more difficult, and it is not easy to use cooling water at room temperature to complete, so it needs to cool the condensed water, so it needs more costs. This method is mainly applied to organic waste gas treatment with high concentration and low temperature.
In addition to the above treatment methods, organic waste gas treatment also includes high temperature and catalyst combustion, activated carbon adsorption, ozone decomposition and electrochemical oxidation. These methods are applicable to organic waste gas treatment, but the specific method depends on conditions such as waste gas concentration, equipment and environmental temperature. Also, consider the level of operation of the operator.

At present, China's industrial development has entered a new stage. People's normal work and life are affected by the increasingly prominent environmental problems, which are attracting more and more attention. Therefore, in this situation, it is necessary to control the emission of harmful gases in the field of production, such as industry, and reduce their pollution to the atmospheric environment. In this paper, relevant technologies of VOC waste gas treatment are mainly discussed, including condensation treatment, oxidation treatment, liquid adsorption, biological treatment and adsorption.
Shanghai yongai jian cleaning equipment co., LTD. Is specialized in providing VOCs cleaning equipment and technology. We are committed to becoming an enterprise integrating r&d, design, equipment manufacturing, engineering contracting and operation management. The company has the general contracting qualification of environmental pollution control, special design of environmental engineering and a number of related patent certificates, and is a member of the environmental protection association.

发布于2017-11-27