Structure and classification of dual fuel burners - self recycling burner

Structure and classification of dual fuel burners
At present, there are two main combustion methods for natural gas boilers. One is the specialized combustion method, which combines the boiler with gas. Gas boilers can fully demonstrate their advantages in equipment investment, operational efficiency, and other aspects; Another type is the mixed combustion method, which is equipped with two combustion systems: gas fuel and gas coal. The boiler can burn gas alone or separately burn another or a mixture of two fuels, also known as a dual fuel burner.
A dual fuel burner is a type of burner in which both burners have gas and fuel nozzles simultaneously. The air regulator, flame stabilizer, ignition device, and flame monitoring device in the control room of the dual fuel burner must be able to meet the requirements of both fuels simultaneously.
1、 Design
Although dual fuel burners come in various forms, for high-power boilers, they are mainly a multi burner combustion method formed by mixing coal powder or oil gun with coal powder or heavy oil for combustion. The effect of the central air pipe rotating airflow further strengthens the mixing and combustion; To improve low load performance, the air adopts a three channel structure, and each air volume is adjusted by a separate regulating baffle, making the burner more complex.
2、 Organizational structure
The dual burner mainly consists of three parts: shared part, fuel component, and gas component.
1. Common components
Includes air ducts, guide vanes for controlling airflow direction, air branches, and fire-resistant fire channels. In addition, there is a small flame igniter, which should be located in a reliable position to store fuel and gas. The position of the fire detector should be able to detect small flames, gas main flames, and fuel (or coal) flames. When a larger gas supply system is installed inside the fuel burner, it may interfere with the mixing method of fuel combustion. The solution is to arrange the gas inlet outward on the periphery of the burner.
2. Fuel components
Mainly an oil atomizer, its function is to separate the oil and evenly distribute the oil mist into the airflow in a controllable way. The following types of atomizers are commonly used:
(1) Jet atomizer
The oil enters the swirl chamber through the air hole at the corner and sprays out in a conical form from the ring pipe mouth, dispersing into droplets. The pressure of oil is generally between 0.35 and 1.4 megapascals, up to 7.5 megapascals. The viscosity of the oil during operation is about 15 × 1030 m2/second. The simple jet atomizer has a certain impact on the load regulation rate of the burner, but it can be improved by overflow reflux. Because too much oil can reflux, regardless of the flow rate, the amount of oil entering the swirl chamber is constant: a good swirl can be formed at high flow rates, and a certain thickness of oil mist flow can be maintained at the outlet.
(2) Steam assisted atomizer
This type of atomizer was used in the early stages, where the water vapor was directed into the oil flow and ruptured in the oil flow, forming mist. During use, due to the high consumption of steam, the use of jet atomizers has had a certain impact on it. In recent years, this model has undergone significant reforms, resulting in a significant reduction in steam consumption.
3. Gas components
The gas components of the dual material burner adopt a nozzle mixing type. Due to the oil atomizer occupying the center position of the stable area of the burner, the gas components are subject to certain limitations. Using detachable nozzles or ring chambers for heating, it can reach the center position; However, if a rotary cup oil mist eliminator is used simultaneously, this cannot be achieved, and in other design styles, central air supply becomes difficult as the load increases. Therefore, gas entry is usually through a ring or nozzle located between the atomizer and the casing.
3、 Classification.
Dual fuel burners can be divided into two types: assembled burners (including fans and control devices, which are assembled by the manufacturer before leaving the factory) and on-site assembled burners (burners and controllers are assembled on-site, with additional fans). The first type is mainly used in fire tube boilers, while the latter is mainly used in water tube boilers. Generally speaking, a dual fuel burner is formed around an existing fuel burner, with an injector installed in the center of the burner, and gas must be introduced from the opening of the oil atomizer and housing.