What are the methods of waste heat recovery from regenerative incinerators?
One of RTO's waste heat recovery methods includes directly supplying warm air to the workshop. After adjusting the temperature by adding high-temperature flue gas with ambient air, the warm air is then directly delivered to the workshop. Alternatively, it can be used through a plate heat exchanger to obtain fresh warm air ranging from 100 to 400°C, which is then directed to the heating equipment.
The technology for waste heat recovery is mature and widely used in corporate production. Waste gas treatment is crucial, as it not only promotes environmental protection but also achieves cost savings.
By installing a heat transfer oil heat exchanger at the rear of the rotating RTO, the excess heat is converted into high-temperature heat transfer oil. If the customer has a heat transfer oil boiler and piping system, they simply need to connect the RTO heat oil heat exchanger in series with the existing system output path. If the customer does not have the corresponding system, a new heat transfer oil system will be configured and connected to the customer's heating equipment.
The heat recovery method for thermal oil is suitable for heat process temperatures of ≤250°C, and is currently mainly applied in industries such as coating.
By installing a hot water tube heat exchanger at the rear of the rotating RTO high-temperature bypass valve, a water circulation system is configured to convert excess heat into 85°C hot water, which is then stored in a hot water storage tank. An external water circulation system is also set up to deliver the hot water to heating equipment, which includes printing hot air heat exchangers, industrial washing hot water, and domestic water supply. Additionally, it can be connected to the central air conditioning system to reduce the cooling load, serving as heating for the workshop.
The heat recovery method for hot water is characterized by its economic simplicity and low investment. Moreover, the equipment does not fall under special equipment for high pressure and high temperature, thus no inspection or special protection is required. The hot water recovery method is suitable for heating processes at temperatures of ≤75°C and is currently widely used in flexible packaging printing equipment.
By configuring a steam waste heat boiler at the rear of the rotating RTO, excess heat can be converted into high-pressure steam. This steam can be connected in parallel with the manufacturer's original steam boiler or the municipal steam supply. It is then adjusted for temperature and pressure using a steam accumulator before being delivered to the corresponding heating equipment. The steam heating system with a backup steam heat source ensures that when the waste heat from the exhaust does not meet the heating requirements of the workshop, the backup steam heat source supplements the heat. This allows for quick startup of the heating equipment, flexible steam usage, and the operation time is not limited by the RTO's boiler startup. In a steam heating system without a backup steam heat source, when the waste heat from the exhaust does not meet the workshop's heating needs, the RTO burner supplements the heat, and the startup time of the heating equipment is limited by the RTO's boiler startup time.
The steam waste heat recovery method boasts high heat exchange coefficients, compact heat exchanger volume, and good temperature control accuracy. It is suitable for heating processes with temperatures of ≤160℃ and is currently widely used in industries such as flexible packaging, coating, painting, and food processing.
How to Achieve Even Greater Energy Efficiency:
The company has designed a new furnace type that combines regenerative thermal oxidation (RTO) technology with catalytic combustion. This innovative design leverages the energy-saving benefits of RTO furnaces with the low-temperature catalytic combustion advantages of CO furnaces, enabling the RTO to achieve both energy and emission reduction.
The structure and dimensions of the combustion chamber should be calculated and determined based on factors such as the combustion temperature, residence time, and the volume flow rate of the waste gas to be treated passing through the combustion chamber. The temperature/concentration field can be simulated and calculated using fluid mechanics models.
The correct residence time of exhaust gas in the combustion chamber depends on factors such as the cross-sectional area and length of the furnace, as well as the flow velocity of the gas. Generally, a residence time of 1.0 to 1.3 seconds within the furnace is sufficient to meet the exhaust gas emission standards.
Combining the swirl secondary atomization technology, the special air staging technology, and the automatic control technology based on the burner's structure and performance, we have improved the combustion performance of the burner, achieving complete combustion.
Five, insufficient gas supply can lead to incomplete combustion of waste gases, producing a large amount of carbon monoxide. Excessive oxygen can cause more heat energy to be lost with the hot air, resulting in heat loss. The correct air supply not only saves fuel but also ensures sufficient combustion of combustible materials, purifies exhaust gases, and reduces emissions of pollutants.
Six, Appropriate combustion temperatures are more conducive to RTO energy saving. Increasing the furnace temperature can enhance the completeness of oxidation combustion. However, excessively high furnace temperatures lead to increased heat loss, shorten the lifespan of the RTO, and increase the company's costs. Moreover, overly high furnace temperatures consume more fuel, reducing the effectiveness of waste gas purification and affecting the compliance of waste gas emissions.
The RTO regenerative thermal oxidizer is a common waste gas treatment equipment, with a waste gas treatment efficiency of % and a heat recovery rate of 90%, making it popular among many enterprises. However, in actual operation, RTO regenerative thermal oxidizers often experience explosion accidents. Why do RTO units cause accidents, and what are the solutions?
The cause of the explosion incident at the regenerative incinerator:
One: System malfunctions or sudden power or gas outages in equipment such as gauges and valves can lead to the failure of the system's stable automatic control design, causing the system to overheat and potentially explode.
VOCs emissions are flammable and, coupled with the high temperatures and open flames inherent in operation, it is prone to explosive accidents in regenerative thermal oxidizers when the concentration exceeds the explosive limit.
Three, excessive heat within the oxidation chamber of a regenerative incinerator can also lead to overtemperature explosions, should the heat exceed the permissible limit.
Preventive Measures for Explosion Accidents in Regenerative Thermal Oxidizers
One: Interlock shutdown due to operational overload, equipment failure: The system triggers an interlock shutdown when the concentration entering the regenerative incinerator cannot be controlled, excess heat within the furnace cannot be released, or equipment failure prevents operation.
By controlling the combustion chamber temperature to adjust the bypass valve opening, excess heat in the furnace is dispersed: when the combustion chamber temperature rises, the bypass valve is opened wider to increase the heat sent to the waste heat recovery unit; when the combustion chamber temperature drops, the bypass valve is closed narrower to reduce the heat sent to the waste heat recovery unit. The main control is to maintain the combustion chamber temperature between 900-1000°C, typically set at 950°C and automatically tracked. If the regenerative incinerator system is not equipped with a waste heat recovery unit, excess heat can be directly discharged into the chimney through the bypass valve.
The company has implemented a limit on the concentration of exhaust gas entering the furnace: The oxidation and decomposition of useful substances release a large amount of heat, causing the exhaust gas temperature to rise. As the temperature increases, it lowers the lower explosive limit (LEL) concentration of the useful substances. Therefore, it is typically necessary to control the concentration of exhaust gas entering the furnace to be less than 25% LEL. During the design phase, a variable frequency dilution fan is used to adjust the dilution air volume, controlling the exhaust gas concentration entering the oxidation furnace. The primary control is set to maintain the LEL between 20% and 25%, with a general setting at 20% and automatic tracking.
Due to the risks of instrument and valve failures, as well as the requirements for system stability and rapid control response in the event of sudden power or gas outages, the system valves are equipped with pneumatic actuators. The oxidation furnace inlet valves and transfer valves are selected with air-open type valves, while the emergency bypass valves are fitted with air-closed type valves.
