Application of Suzhou Huaene | Regenerative Exhaust Gas Treatment Furnace (RTO) in Color Coating Line:

RTO

1. Incineration Principle of Organic Solvents and Characteristics of RTO

The organic solvents in steel plate coating are incinerated before discharging. The conditions required for solvent incineration are sufficient temperature (760 C), sufficient residence time (1.6s), good mixing of air and solvent, and larger heat can be generated when a solvent is incinerated.

With the successful operation of regenerative incineration technology in the field of steel rolling reheating furnace, the development of waste gas incinerator has been greatly promoted. RTO is an engineering technology that applies regenerative incineration technology to waste gas incinerator, thus achieving a major breakthrough in the field of energy saving and environmental protection.

Regenerative Thermal Oxidiger (RTO) is short for RTO. It is a new generation of organic waste gas treatment equipment. Its working principle is that organic waste gas is heated and heated by preheating chamber, then it is incinerated into incinerator chamber at high temperature (up to 800 degrees C), oxidizing organic matter into carbon dioxide and water, and then discharged after storing heat in another regenerator. The stored heat is used to preheat the newly entered organic waste gas, and the direction of air flow is periodically changed to maintain the stability of furnace temperature.

The operation principle of RTO equipment is shown in Figure 1. The equipment has three symmetrical regenerator and two incineration chambers. Organic exhaust gas first enters ceramic regenerator A under the effect of blower. After absorbing heat, it enters the incineration chamber. The regenerator A is cooled by exothermic heat. After incineration, the gas enters regenerator B. After heat exchange, the heat is stored in ceramic regenerator B, and then discharged. The residual untreated organic waste gas in the regenerator C space was purged back to the incinerator for incineration treatment. After treatment of exhaust gas at a certain time (about 2 minutes), the direction of air flow changes from regenerator B to incineration chamber. After heat absorption and heating by regenerator B, it is incinerated at high temperature in the furnace. Finally, it is discharged after heat exchange in regenerator C. The regenerator A is in reverse purge condition. After a certain time (about 2 minutes), the direction of air flow is changed again and the temperature of incineration chamber is ensured to be 800 degrees C. Above all, high removal rate and heat transfer efficiency are ensured.

RTO incinerator

RTO equipment consists of three regenerator chambers, two incineration chambers and six main flow switching valves. The regenerator is filled with honeycomb ceramic regenerator, and each incinerator is equipped with a liquefied petroleum gas (LPG) incinerator with share adjustment. The heating capacity of each incinerator is actively regulated by the temperature response signal in the furnace through the PID regulator. In addition, the incineration system has the functions of active pre-purging, extinguishing protection, over-temperature alarm and over-temperature active blocking of fuel supply before ignition. RTO furnace has six conditions: pre-blowing, ignition, heating, incineration, thermal insulation and post-blowing shutdown. When RTO furnace is in pre-blowing, ignition, heating, thermal insulation, post-blowing shutdown 5

In all cases, the exhaust gas from the drying room is discharged directly. According to the start and stop conditions of each drying chamber, this equipment can actively give the actual operating air volume of RTO furnace, and then actively adjust the speed and air volume of blower and induced draft fan of RTO furnace system through frequency converter to ensure the normal production of drying chamber. Once RTO furnace breaks down, RTO furnace will send signals to each drying chamber, exhaust gas will be directly exhausted, RTO furnace will be converted into fault blowing condition. RTO performance characteristics:

(1) The purification efficiency is high, 94% in two rooms and 99% in three rooms.

(2) High heat transfer efficiency (>90%) and energy saving, the concentration of organic waste gas above 3g/m3 can reach heat balance.

(3) Low resistance, low fan installed power, energy saving and low operating costs.

(4) High temperature resistance (1000 C), normal temperature is 800 850 C.

2. The Characteristics of RTO in Colour Painting of an Enterprise

The color coated RTO which has been put into use now is a typical two-chamber furnace, including two pairs of regenerator and one incineration chamber. The amount of waste gas treated is about 44000 m3/h. It is the largest RTO equipment in operation in China at present. The maximum running speed of color coating machine is 110 m/min.

RTO's incineration system is ECLIPSE special incinerator, which is characterized by a large conditioning ratio of 1:40. Together, RTO's pressure fluctuation in the incinerator during the reversing process is well adapted. As a reversing device, the conditioning plugging valve satisfies the requirement of 40-60 s reversing once and running for a long time.

The operation of the RTO is not only a new and higher requirement for energy saving, but also a new standard for exhaust emission.

Problems and Solutions of 3RTO

In order to deal with this problem, the best way is 3-compartment RTO, but the cost is expensive. In order to deal with this problem, two-compartment RTO is used to reduce the exhaust. A kind of RTO based on two-chamber combined with back-blowing function is designed, which is two-chamber RTO plus back-blowing chamber.

Room two RTO

It can be seen that in addition to the regenerator (A), the regenerator (B) and the incineration chamber, a back-blowing chamber is added to the gas emission. The purpose of the reverse blowing chamber is to lead the exhaust gas into the reverse blowing chamber through the control of the blocking valve in the reversing process. After the air outflow and reversing in the reverse blowing chamber are completed, the fan first blows the gas in the reverse blowing chamber back into the RTO interior, thus repeating the process, and treating the outflow of the gas in the reversing process, the RTO exhaust treatment rate can be improved by 5%.

After adding the design of the back-blowing chamber, the waste gas treatment rate can be greatly improved without obvious addition of the investment scale, and the special commutation equipment has great potential for development.

4 Conclusion

(1) RTO is suitable for organic waste gases of 2-8g/m3 concentration. For low calorific value gases (e.g. ethyl acetate, etc.), RTO can reach 12g/m3, especially for incineration of refractory components.

(2) RTO can effectively utilize the incineration temperature of the incinerator and the incineration heat of solvents under the condition of continuous operation, and the thermal efficiency is up to 90%.