Abstract: The current research status and basic process characteristics of zeolite runner adsorption enrichment and incineration technology are introduced. A new process of concentrating + catalytic combustion of volatile organic compounds by zeolite is introduced. The characteristics and key points of this process are pointed out , And the development of the technology.
The wide range of VOCs, their complex composition and their varying nature make VOCs difficult to meet regulatory requirements and uneconomical in many cases. Using the advantages of different unit management techniques, the combination of treatment process, not only to meet the emission requirements, but also reduce the operating costs of purification equipment. Therefore, in the organic waste gas treatment, the combination process using two or more purification technologies has been rapidly developed. Zeolite rotary concentrating technology is a new technology developed for the treatment of low-concentration VOCs, combined with catalytic combustion or high-temperature incineration to form zeolite runner adsorption enrichment + incineration technology.
Technical research status quo
Honeycomb rotor adsorption + catalytic combustion technology is an organic waste gas treatment system invented by Japan in the 1970s. The adsorption device is a honeycomb rotor assembled with corrugated cardboard made of molecular sieve, activated carbon fiber or carbonaceous material, and the adsorption In contrast to the flow of desorbed gas, both processes are carried out simultaneously. This system was introduced and imitated by our country in the early 1980s. However, due to the adsorption element (honeycomb rotor) and the connection of key parts of the system, the problem of channeling wind was not fundamentally solved, and the performance of the equipment Stable, so less domestic applications, has been unable to get promotion.
In the late 1980s, a fixed bed adsorption + catalytic combustion system was developed. The system is to adsorb the material loaded in a fixed bed, and then combined with the catalytic combustion bed adsorption bed purification system. The principle of the process system is basically the same as that of the above-mentioned honeycomb wheel adsorption + catalytic combustion technology. However, the adsorption and desorption regeneration processes of the single-component adsorption bed are separately carried out and overcome the problems that the honeycomb wheel cleaning system sucks and desorbs easily Gas shortcomings. After continuous improvement, the system configuration is more reasonable, high purification efficiency, energy-saving operation significantly, technically reached the international advanced level. The process system is ideal for treating large volumes of VOCs and low concentrations of VOCs, with a single system of exhaust gas throughput ranging from a few thousand m3 / h to more than 100,000 m3 / h. This technology is our country truly innovative VOCs exhaust gas treatment technology, since 1989 for the first time in the domestic promotion, so far there have been hundreds of sets of such systems and devices in use. Has become one of the mainstream products for domestic Industrial VOCs exhaust gas treatment and it is expected that there will still be great application prospects in the future.
The use of catalytic combustion of industrial organic waste gas treatment has been widely used in automotive spraying, tape manufacturing and aircraft parts spraying. Catalytic combustion technology will volatilize a large number of organic solvents combustion. The catalyst adopts porous ceramic carrier catalyst. The preheating temperature before catalysis depends on the type of VOCs: polyurethane 380 ℃ ~ 480 ℃, polyesterimine 480 ℃ ~ 580 ℃; organic concentration 1600mg / m3, the average purification efficiency 99%.
Runner concentrated + catalytic combustion of new technology
1 Technical Overview Aiming at the problems such as large equipment investment, high operation cost and low removal efficiency when various methods are used to deal with VOCs pollutants with low concentration and large volume of air, domestic enterprises have developed a system for the treatment of low VOCs, large Industrial air emissions of high efficiency, safe process. The basic idea of ​​this method is as follows: Adsorption separation method is used to separate and concentrate VOCs in low-concentration and large-volume industrial waste gas, and then the concentrated and small amount of polluted air is decomposed and purified by combustion method. Combustion decomposition purification method. The adsorption rotor with the honeycomb structure is installed in a housing divided into three zones of adsorption, regeneration and cooling, and is slowly rotated at a speed of 3-8 rotations per hour under the driving of the speed governing motor. The three zones of adsorption, regeneration and cooling are respectively connected with the processing air, the cooling air and the regeneration air duct. In addition, in order to prevent air leakage between the zones and air leakage between the circumference of the adsorption rotor and the casing, between the partition plate of each zone and the adsorption rotor and between the circumference of the adsorption rotor and the casing A high temperature, solvent-resistant fluorine rubber sealing material. Contaminated air containing VOCs is sent to the adsorption zone of the adsorption rotor by the blower. When the contaminated air passes through the rotor honeycomb channel, the VOCs contained in the contaminated air are adsorbed by the adsorbent and the air is purified. As the adsorption rotor rotates, the adsorption rotor close to the adsorption saturation enters the regeneration zone. During contact with the high temperature regeneration air, the VOCs are desorbed into the regeneration air and the adsorption rotor is regenerated. Regeneration after the adsorption wheel cooled down through the cooling zone, the adsorption zone back to complete the adsorption / desorption / cooling cycle. Because the air volume of the regeneration air in the process is generally only 1/10 of the air volume of the process air, the concentration of VOCs in the air at the outlet of the regeneration process is concentrated to 10 times the concentration in the air. Therefore, this process is also called VOCs concentration and removal process.
Wheel adsorption concentration - catalytic combustion process shown below.
No. 1 fan driven exhaust VOCs containing a region through the runner, a region for the adsorption zone, according to different objectives can be filled in the wheel different adsorbent material. Area a adsorbed VOCs with the wheel rotation to the b area for desorption. The high-temperature air flowing through the heat transfer 1 desorbs the VOCs adsorbed on the wheel and reaches the light-off temperature through the heat transfer 2, and then enters the catalytic combustion chamber for catalytic oxidation. Since the rotor is desorbed and then adsorbed, the cooling zone c is provided next to the desorption zone to cool with air, and the warmed air after cooling becomes the hot air for desorption via the heat transfer 1. The hot gas stream after the catalytic combustion reaction transfers part of the heat to the heat transfer 2 and the heat transfer 1 to the air. In order to prevent the catalytic combustion chamber temperature is too high, set the third-party cooling circuit for catalytic combustion chamber emergency cooling. The whole system consists of two monitoring systems. PC1 is responsible for monitoring the temperature of catalytic combustion chamber and heat exchanger (its internal electric auxiliary heating device is used to balance temperature fluctuation). PC2 is responsible for fan control and regulates the intake air flow according to the actual situation. PC2 belongs to the sub-system of PC1. When PC1 detects the temperature fluctuation exceeding the allowable range, PC2 immediately sends the message to PC2, and PC2 transfers the received message to each fan.
2 new technology features
(1) adsorption zone bypass the establishment of internal circulation. When the exhaust gas adsorption area after adsorption does not meet the standard, into the bypass within the loop, adsorption treatment again. The basic idea of ​​this by-pass cycle is to eliminate existing pollution and absorb new pollution.
(2) Cooling air bypass established. In the case of very complex conditions, the concentration of VOCs is likely to rise sharply. At this time, part of the cooling air is introduced into the adsorption zone to reduce the amount of desorbed air while fresh air is added after heat transfer 2 to maintain the volume of air entering the catalytic reactor Within the preset range. The basic idea of ​​this by-pass is to dilute high-concentration VOCs with fresh air, so from the effect point of view, this method will also extend the treatment time.
(3) compared with the traditional process, the entire system uses induced draft fan design, easy to bypass the regulation. Removal of the cooling fan for the catalytic combustion device, this machine is a temporary solution, instead of controlling VOCs concentration in the rotor part.
(4) The catalytic combustion chamber to remove the electric heating system, replaced by heat transfer 2 to the air heating VOCs ignition temperature, and the use of reaction exotherm catalytic combustion chamber temperature stabilized at 500 ℃ ~ 600 ℃ range.
(5) The speed of the wheel is easy to adjust. Under the condition of 2, the speed of the wheel can be properly increased to reduce the amount of VOCs adsorbed per unit area of ​​the wheel per unit time, so as to ensure the safety of the system.
Influence factors of wheel adsorption
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