15 questions to answer the catalyst principle, application and common questions of VOCs catalytic combustion

Catalytic combustion technology as one of the VOCs exhaust gas treatment process, because of its high purification rate, low combustion temperature (generally less than 350 degrees C), combustion without open fire, there will be no NOx and other secondary pollutant generation, safety, energy saving and environmental protection, etc. , in the environmental protection market application has a good development prospects. As a key technical link of catalytic combustion system, the synthesis technology and application rules of catalyst are very important.
1. Catalytic combustion reaction principle
Catalytic combustion reaction principle is that organic exhaust gas at lower temperatures under the action of the catalyst is fully oxidized and decomposed, to achieve the goal of purifying the gas

. Catalytic combustion is a typical gas-solid phase catalytic reaction, the principle of which is that reactive oxygen participates in deep oxidation. In the process of catalytic combustion, the role of the catalyst is to reduce the active energy of the reaction, while the reactant molecules are collected on the catalyst surface to improve the reaction rate. With the help of catalysts, organic exhaust gases can burn without flame at lower ignition temperatures and release large amounts of heat, while oxidizing and decomposing into CO2 and H2O.
the catalyst reaction schematic for catalytic combustion . 2. What is a low temperature catalyst
low temperature catalyst performance index: starting temperature ≤200 degrees C, oxidation conversion efficiency ≥95%, hole density 200-400cpsi, pressure strength ≥8MPa.
3.VOCs catalyst in catalytic combustion system role and impact
usually VOCs have a higher self-combustion temperature, through the catalyst's active, can reduce voCs combustion of the active energy, thereby reducing the combustion temperature, reduce energy consumption, save costs.
addition: the general (without catalyst) combustion temperature will be above 600 degrees C, such combustion will produce nitrogen oxides, commonly called NOx, which is also to strictly control pollutants. Catalytic combustion is not the burning of open flames, generally below 350 degrees C, there will be no NOx generation, so more safe and environmentally friendly.
4. What is airspeed?
What factors affect airspeed
In VOCs catalytic combustion systems, reaction airspeed usually refers to volume-empty speed (GHSV), which reflects the processing power of the catalyst: reaction airspeed refers to the amount of gas treated by the catalyst per unit of time per volume under specified conditions, in m3/(m3 catalyst-h), which can be reduced to h-1. For example, the product labeled air speed 30000h-1: represents each cubic catalyst can handle 30000m3 exhaust gas per hour. Airspeed reflects the VOCs processing power of the catalyst and is therefore closely related to the performance of the catalyst.
the relationship between precious metal load and air speed, is the higher the precious metal content, the better?
the performance of precious metal catalysts is related to the content, particle size and dispersion of precious metals. Ideally, precious metals are highly dispersed, at which point the precious metals are present in carriers with very small particles (several nanometers) and the precious metals are used to the maximum extent possible, at which point the processing power of the catalyst is positively related to the precious metal content. However, when the precious metal content is high to a certain extent, metal particles tend to gather and grow into larger particles, precious metals and VOCs contact surface downside down, most precious metals are wrapped in the interior, at this time increase the precious metal content is not conducive to the increase of catalyst activity.
6. After gas combustion, the effect of gas volume expansion on air throes
In a stable operating state, gas volume expansion has little effect on air throes, because in general, VOCs content is not high, only the expansion of this part of the gas, the volume flow increase is very small.
7. Advantages of nanocatalysts
national catalysts refer to the active components of catalysts (e.g. precious metals) dispersed on the carrier at the nanoscale, the active components of catalysts as much as possible exposed to the gas, so that the opportunity for contact between the two greatly increased, such catalysts generally superior performance.
8. The definition of the starting temperature and the full conversion temperature, and the relationship with the exhaust gas concentration
ignition temperature: the purification rate reaches 10% of the required temperature
completely converted temperature: purification rate >98% of the required temperature
catalytic combustion will reach a high temperature in a very short period of time, and the exhaust gas concentration reaches a certain degree, its reaction heat release can achieve self-heating catalytic reaction.
9. The stacking method of the catalyst
in the range allowed by the pressure drop, the catalyst should be stacked in accordance with the "high thin type" mode, the high diameter ratio should be greater than 1.5. Otherwise, the utilization rate of the catalyst against the wall will be lower, affecting the catalytic effect of the overall catalyst bed. The hole channel is consistent with the gas flow, maintain a certain length of the hole, each section of the catalytic block should be staggered, the four sides and the reactor wall contact area should be used steel skeleton folding edge or the use of high temperature material seal to prevent exhaust gas leakage.
10. Waste gas pre-treatment can prolong the life of catalysts and catalytic combustion equipment reason analysis
exhaust gases may contain some harmful components to the catalyst, if such chemicals are known to exist, the exhaust gas should be pre-treated, otherwise these harmful components will have a great impact on the life of the catalyst.
exhaust gas should be pre-treated (dehumidification of dust and oil) before entering the catalytic tank. Dust, carbon accumulation and high-boiling viscosity attached to the surface of the catalyst, covering the active position of the catalyst, will lead to catalyst catalysis, therefore, the introduction of dust and high-boiling viscous should be avoided.
high humidity environment, water vapor and oil mist can easily act with the catalyst at high temperatures, causing catalyst sintering infestion, so water vapor and oil mist should be minimized into the catalyst bed layer.
11. The importance of the control of exhaust gas concentration in catalytic combustion systems
The appropriate exhaust gas concentration ensures the safe and efficient handling of exhaust gases in catalytic combustion systems, while helping to extend the service life of equipment and catalysts.
concentration is too low: a large amount of energy is used to heat the air, the energy consumption is high, the reaction heat is not enough to maintain the system's self-heating combustion, this condition is recommended to concentrate the exhaust gas.
concentration is too high: the risk of explosion, the temperature rise is too high, the combustion temperature is too high (long time above 600 degrees), damage to equipment and catalysts, this condition is recommended to add new wind dilution exhaust gas below the lower explosion limit.
12. Catalytic combustion equipment start-up and parking precautions
before the system starts, fresh air preheats the catalyst, and then warms up the exhaust gas to more than 250 degrees before introducing the catalytic chamber;
13. Catalyst poisoning instructions
Certain chemicals can cause catalyst poisoning, such as phosphorus, sulfur, lead, mercury, arsenic and halogens, such as organic or inorganic materials on the catalyst damage is very strong, will lead to permanent ineration of the catalyst, can not restore activity.
14. The treatment of carbon from catalysts
heats the catalyst in fresh air to 500 degrees C for 2-4 hours, removing or partially removing carbon accumulation.
15. Factors affecting the life of the catalyst
the use of catalysts should be strictly in accordance with the conditions of the catalyst. Factors affecting the life of the catalyst include the pre-treatment of the exhaust gas, i.e. the cleanliness of the exhaust gas, the temperature of the catalytic chamber, the toxicity of halogens and catalysts, and the operating procedures of the catalytic combustion equipment.
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