The functions of the air duct pre-sprayer include:
✓ Primary spray purification
✓ Cooling and fire safety
✓ Prevention of adhesion to the inner duct walls
Ningbo Tenzon Umwelttechnik Co., Ltd ，High-efficiency energy-saving core processing equipment
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Heat Treatment Oil Fume Processes
Release Date：
Apr 14,2026
Heat treatment equipment includes box furnaces, continuous furnaces, ring furnaces, pusher furnaces, pit carburizing furnaces, medium-frequency furnaces, etc. The processes range from pre-oxidation, carburizing, nitriding, quenching, washing, tempering, air cooling, air quenching, and water quenching. Among the aforementioned, the processes that require priority attention for oil mist control include multi-purpose furnaces, tempering furnaces, pit furnaces, quenching operations, etc.<br> The exhaust air from heat treatment contains various oil mists, carbon black, metal oxide impurities, and certain acidic oxides. The dust particles are fine in size, and the flue gas temperature inside the ducts ranges from 50°C to 200°C. The gas is oily, viscous, high-temperature, and carries sparks (with flames present at the source, and the adherent deposits on the inner duct walls are prone to ignition). It also contains low concentrations of NMHC, among other components.
TECHNOLOGY
— Heat treatment equipment includes box furnaces, continuous furnaces, rotary hearth furnaces, pusher-tray furnaces, pit-type carburizing furnaces, and medium-frequency furnaces. Processes range from pre-oxidation, carburizing, nitriding, and quenching to cleaning, tempering, air cooling, air quenching, and water quenching. Among these, multi-purpose furnaces, tempering furnaces, pit furnaces, and quenching operations are the primary sources requiring oil mist and fume control.
— Heat treatment exhaust fumes contain various oil mists, carbon black, metal oxide impurities, and certain acidic oxides. The particulate matter is fine, and the flue gas temperature ranges from 50°C to 200°C. The emissions are oily, viscous, and hot, and may contain sparks (flames exist at the source, and deposits on the inner duct walls are prone to ignition); they also contain low concentrations of non-methane total hydrocarbons (NMTHC).
— Based on the operating conditions described above, Tenzon is high-efficiency Venturi wet separator is ideally suited for the collection and purification of the waste gas stream. The proposed solution utilizes a high-efficiency Venturi wet purification system equipped with a pre-spraying system; depending on environmental compliance requirements, secondary purification stages—such as filtration, electrostatic precipitation, or activated carbon adsorption beds—can be added downstream to ensure the exhaust meets discharge standards. The process flow is as follows:
Fume hood ➔ Balancing damper ➔ Interlocked damper ➔ Pre-scrubber ➔ Collection duct ➔ Venturi primary scrubber ➔ High-efficiency wet separator (with recirculation tank) ➔ (Filtration/Electrostatic) ➔ (Activated carbon adsorption bed) ➔ Centrifugal fan ➔ Exhaust stack
— Depending on the production line configuration—for instance, in a box-type furnace line where only one or two furnace doors among several multi-purpose and tempering furnaces are opened simultaneously—interlocking valves can be installed to coordinate the air duct branches with the furnace door operations. This significantly reduces the total system airflow, thereby substantially lowering costs associated with environmental protection investment and operational energy consumption, while still ensuring effective collection and purification performance.
— A Venturi pre-nozzle is installed behind the capture hood; pre-spraying the fumes not only treats the grease and smoke but also extinguishes sparks and lowers the temperature.
— The inner walls of the ductwork are flushed to prevent the buildup of deposits.
— Raw air containing dust and fumes undergoes pre-spraying with water, and the resulting air-water mixture is conveyed through the duct system to the separator.
— A main Venturi nozzle is positioned upstream of the separator. Here, the airflow accelerates, fully atomizing the spray water to create a uniform water curtain that washes the dust and fumes in the raw air. Particles that have agglomerated with the water mist are separated from the air within the separator through high-speed centrifugal action. The separated air is then exhausted outdoors by a fan.
— The majority of the spray water and particulate matter (which combines with the water to form sludge or oily residue) drains into the circulation tank via a return pipe. Sludge and oily residue are removed from the tank by automatic desilting or oil-water separation equipment.
— To better meet market demands within the heat treatment industry and address the issue of oil mist and exhaust emissions from workshops, Tenzon offers the aforementioned solutions. These systems effectively treat oil mist and VOC emissions from various types of heat treatment equipment, creating a comfortable working environment for frontline personnel, ensuring customer compliance with environmental regulations, fostering the healthy and sustainable development of the industry, and contributing to the achievement of carbon peak and carbon neutrality goals.
— With the rapid growth of my country's machinery manufacturing sector in recent years, heat treatment equipment has undergone significant upgrades. Many enterprises that previously relied on pit-type or box-type furnaces have transitioned to fully automated continuous multi-purpose furnace production lines. These lines support a wide range of heat treatment processes, including carburizing followed by direct quenching, carburizing with slow cooling, carbonitriding, quenching, bright quenching, protective-atmosphere hardening and tempering, and annealing.
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