Kiln Burners– engineered for specific job requirements
The burner system is an important and integral component of a rotary kiln system to optimize the combustion of fuels to release heat in the kiln. Safety considerations, ease and flexibility of operation, product quality, energy efficiency, maintenance costs, and the environmental impact of the products of combustion are some of the most critical areas that a kiln operator must evaluate in selecting a kiln burner.
Metso, with over half a century of experience in designing and manufacturing rotary kiln-based thermal processing systems, has the technical expertise and capability to provide rotary kiln operators with a kiln burner system that best meets their requirements. Since 1950 Metso has successfully engineered and supplied more than 300 burner systems.
At Metso we have experience with many different fuels, including conventional fuels such as coal, coke, gas and oil, and unconventional fuels such as, COG (coke oven gas), saw dust, tires, biofuels and other alternative fuels. Different types and qualities of fuels can cause different temperature profiles within a rotary kiln, which will cause changes in operations.
The burner and process system oxygen content can affect product quality and energy consumption; controlling it, therefore, has great economic advantages. Air is typically used as the oxidizing agent, but in some applications purified oxygen is introduced to reduce gas flows, reduce nitrogen oxide generation and/or obtain higher temperatures. When the exact amount of air is mixed with a fuel to completely oxidize the hydrocarbon species present, it is calledstoichiometric combustion. Most plants that burn fuel target an excess air rate of 0.5% to up to 5% above stoichiometric conditions. The lower the excess oxygen content, the less gases are being sent through the system and therefore downstream gas handling equipment will be more efficient. Unfortunately, not all fuels may be combusted at such a low oxygen level, and in some applications having excess air can act as a benefit to the overall system.
When designing a burner system, Metso’s engineers consider: the process, primary and secondary air momentum, system temperature profile requirements, and emissions requirements. Reduced NOx emissions and optimum flame shape is achieved with the use of two primary air chambers.
Metso can engineer burner systems for specific job requirements based on our vast burner experience:
- Multi-fuel capability designed to handle gas, oil, pulverized coal, petroleum coke or non-condensable gases separately or in combination.
- Complete fuel flow control, directional adjustability, and flame shape control is obtained by dual air channels.
- Low primary air design is used to maximize fuel efficiency and energy recovery from auxiliary cooling devices.
- Design features include mechanical or steam atomization of oil and sturdy, rugged construction for high temperature duty, utilizing stainless steel materials for blast pipe, blast pipe internals and fuel nozzles.
- Engineered and custom designed valve trains for safe, efficient, reliable combustion are provided.
- Burner systems range from preheat to 300 MBtu/hr (315 GJ/hr).
Burner combustion system
The Metso kiln burner is designed for maximum flexibility of fuel type and flame shape. The primary fuel is typically pulverized coal or coal+coke, with the option to burn natural gas or fuel oil. Either natural gas or fuel oil can be ignited directly by the integral ignition system. Typically, natural gas or fuel oil is be used to heat up the rotary kiln and then ignite the coal flame, but either may be used to fire the kiln up to full operating capacity if desired.
The Metso combustion system is designed with the flexibility to suit the following specific kiln firing applications:
- Wide selection of components including burner, primary air fan, fuel valve trains, pumps and heater sets, flame management system with panel.
- Single or multiple fuels.
- Steam or mechanical fuel oil atomization.
Based on the extensive field experience of Metso engineers, the critical factors of flame shape and location to complement kiln internals is applied to burner design.
Burner design features include single or dual primary air path, dual (axial and radial) natural gas paths, easily changeable fuel oil nozzle, adjustable fuel nozzle to primary air nozzle relationship, and easily adjustable burner mount and primary air flow.