High concentration exhaust gas treatment - RTO equipment - Tianhuan purification

With the implementation of national energy conservation and emission reduction policies and this year's stricter environmental protection laws, many enterprises have begun to pay attention to environmental issues. We will provide a detailed explanation of the currently effective waste gas treatment processes for treating high concentrations of volatile organic compounds (VOCs)RTO thermal storage incineration equipment.

High concentration exhaust gas treatment RTO equipment Thermal storage incineration process

1. Working principle:

Thermal Storage Incinerator (RTO) is an organic waste gas treatment equipment. Its working principle is to heat the organic waste gas to above 760 degrees Celsius, causing volatile organic compounds (VOCs) in the waste gas to oxidize and decompose into carbon dioxide and water. The heat generated during the oxidation process is stored in a specially designed ceramic thermal storage body, which heats up and stores heat. The heat stored in the ceramic thermal storage body is used to preheat the organic waste gas that enters later, which is the "heat release" process of the ceramic thermal storage body, thereby saving fuel consumption during the waste gas heating process.

2. The simple development process of RTO

(1) First generation RTO:

The first generation RTO was a two bed structure consisting of two ceramic thermal storage packing beds, which completed the switching between "thermal storage" and "heat release" processes through a simple one in one out process. The decomposition efficiency of RTO equipment is mainly determined by factors such as reaction temperature, residence time, and gas flow rate. The two bed RTO has two heat storage chambers, and during operation, the two heat storage chambers switch states (inlet outlet) approximately every 1-2 minutes. During the switching process, the damper has about 0.3s-0.6s to directly discharge high concentration exhaust gas to the exhaust port, and the remaining undecomposed exhaust gas at the bottom of the intake heat storage chamber is also directly discharged. A large number of engineering applications have shown that the decomposition efficiency of VOCs in the two bed RTO is 95%, the comprehensive thermal efficiency is 90%, and the temperature difference between the inlet and outlet is as high as 45 degrees Celsius. During valve switching, the pressure fluctuation range in the exhaust gas pipeline is ± 500pa. When the VOCs concentration at the inlet of the two bed RTO is greater than 1g/m3, the outlet concentration will exceed the local emission standards in Beijing and Shanghai (50mg/m3).

(2) Second generation RTO

The second generation RTO also adopts a valve switching type, consisting of three or more ceramic packed beds, and adds a "blowing" function on the basis of the first generation RTO, greatly improving the efficiency of exhaust gas decomposition.

Taking the three bed RTO as an example:

Stage 1: The exhaust gas is preheated through the heat storage bed A and then enters the combustion chamber for combustion. The residual untreated exhaust gas in the heat storage bed C is purified and then blown back to the combustion chamber for incineration treatment (blowing function). The decomposed exhaust gas is discharged through the heat storage bed B, while the heat storage bed B is heated.

Stage 2: The exhaust gas is preheated through the heat storage bed B and then enters the combustion chamber for combustion. The residual untreated exhaust gas in the heat storage bed A is purified and then blown back to the combustion chamber for incineration treatment. After decomposition, the exhaust gas is discharged through the heat storage bed C, which is heated at the same time.

Stage 3: The exhaust gas is preheated through the thermal storage bed C and then enters the combustion chamber for combustion. The residual untreated exhaust gas in the thermal storage bed B is purified and then blown back to the combustion chamber for incineration and decomposition. The exhaust gas is discharged through the thermal storage bed A, and at the same time, the thermal storage bed A is heated.

Such periodic operation causes the exhaust gas to oxidize and decompose in the combustion chamber, and the temperature inside the combustion chamber is maintained at the set temperature (usually 800-850 degrees Celsius). When the exhaust gas concentration at the RTO inlet reaches a certain value, the heat released by VOCs oxidation can maintain the energy reserve for RTO's heat storage and release. At this time, RTO can maintain the temperature inside the combustion chamber without using fuel.

A large number of engineering applications have shown that the decomposition efficiency of VOCs in the three bed RTO can reach 99%, the comprehensive thermal efficiency can reach 95%, the inlet and outlet temperature difference is around 40 degrees Celsius, and the pressure fluctuation in the exhaust gas pipeline is within ± 250pa during valve switching. The VOCs treatment concentration of the three bed RTO cannot exceed 5g/m3, which may exceed the local emission standards in Beijing and Shanghai. In addition, due to its large specific surface area, it has a higher heat dissipation during operation, reducing the amount of residual heat available for reuse.

(3) Third generation RTO

The third generation RTO adopts a rotary diversion guide, with multiple equal ceramic packing beds set up in the furnace. The organic waste gas is guided to each heat storage bed for preheating and oxidation decomposition through the rotation of the rotary directional valve.

The rotary RTO mainly consists of a combustion chamber, a ceramic packing bed, and a rotary valve. The furnace body is divided into 12 ceramic packing beds, which are functionally divided into 5 inlet chambers (preheating zone), 5 outlet chambers (cooling zone), 1 blowing chamber, and 1 isolation chamber. The exhaust gas distribution valve is driven by a motor and rotates continuously and uniformly. Under the action of the distribution valve, the exhaust gas slowly passes through the 12 chambers in sequence. The exhaust gas enters the preheating zone through the intake distributor, where it is preheated to a certain temperature before entering the top combustion chamber and undergoing complete oxidation and decomposition. The purified high-temperature gas leaves the combustion chamber and enters the cooling zone, transferring heat to the ceramic heat storage body, while the gas is cooled and discharged through the gas distributor. The ceramic thermal storage body in the cooling zone absorbs heat and "stores" a large amount of heat (for heating the exhaust gas in the next cycle).

By continuously alternating, the exhaust gas undergoes oxidation and decomposition in the combustion chamber. When the concentration of VOCs in the exhaust gas exceeds a certain value and the heat released from oxidation and decomposition is sufficient to maintain the reaction temperature in the combustion chamber, there is no need to use fuel for heating, ensuring maximum energy recycling.

A large number of engineering applications have shown that the decomposition efficiency of VOCs in rotary RTO can reach 99.5%, and the thermal efficiency can reach 97%. The temperature difference between the inlet and outlet is about 20 degrees Celsius, which greatly reduces the heat loss during RTO operation and ensures the secondary recovery and utilization of thermal energy. The smooth and continuous rotation of the rotary valve has a pressure impact of only ± 25pa on the exhaust gas pipeline, which is extremely important for manufacturers producing optical materials. Due to its high decomposition efficiency, the VOCs inlet exhaust gas concentration of rotary RTO can reach up to 10g/m³.

3. Process flow:

Switching valves change the direction of airflow entering the thermal storage bed, achieving alternating conversion between the thermal storage zone and the heat release zone, and recovering heat from the incinerator. The high heat recovery rate reduces fuel demand and saves operating costs.

When the VOC concentration in the system is greater than the reserved concentration (toluene 1200mg/m3, xylene 1100mg/m3), RTO can maintain the premise of VOC oxidation and decomposition without the need for auxiliary fuel, and can also output system waste heat externally.

4. Advantages and disadvantages:

Advantages:Almost all waste gases containing organic compounds can be treated; Can handle organic waste gases with high air volume and low concentration; The elasticity of treating organic waste gas flow is high (nominal flow rate 20%~120%); Can adapt to changes and fluctuations in the composition and concentration of VOCs in organic waste gas; Not sensitive to small amounts of dust and solid particles carried in exhaust gas; Thermal efficiency (>95%) among all thermal combustion purification methods; Realize self heating operation without adding auxiliary fuel under appropriate exhaust gas concentration conditions; High purification efficiency (three rooms>99%); Low maintenance workload and reliable operation; Organic precipitates can be periodic, and the thermal storage body can be replaced; The pressure loss of the entire device is relatively small; The device has a long service life.

Disadvantages:The weight of the thermal storage incinerator is large due to the use of ceramic thermal storage bodies; The device has a large volume and can only be placed outdoors; Require continuous operation as much as possible; The one-time investment cost is relatively high; Cannot thoroughly purify and treat organic compounds containing sulfur, nitrogen, and halogens.

5. Scope of application:

High concentration exhaust gas treatment RTO equipmentSuitable for the treatment of furnace exhaust gas in painting processes, as well as for the treatment of exhaust gas in industries such as spray painting, plastics, printing, dyeing, chemical, electrophoretic coating equipment, and chemical electronics.