Structure and classification of dual-fuel burner

Structure and classification of dual-fuel burnerdmxBoiler Burner
At present, there are two main combustion modes of natural gas boiler. One is the special combustion mode, that is, the combination of boiler and gas. This gas boiler can fully reflect its advantages in terms of equipment investment and operation economy; The other is the mixed combustion mode, which is equipped with two sets of combustion systems, namely, gas-oil and gas-coal. The boiler can burn gas separately or burn another or two fuels separately, which is also called a dual-fuel burner at this time.dmxBoiler Burner
Dual-fuel burner means that in the same burner, both burners have gas and fuel nozzles at the same time. The air conditioner, flame stabilizer, ignition device and flame monitoring device in the control room of the dual-fuel burner must meet the requirements of both fuels at the same time.dmxBoiler Burner
1、 DesigndmxBoiler Burner
Although there are many forms of dual-fuel burners, for high-power boilers, it is mainly a multi-burner combustion mode formed by mixing combustion of pulverized coal pipe or oil gun with pulverized coal or heavy oil. The role of rotating airflow in the central air pipe further strengthens the mixing and combustion; In order to improve the low-load performance, the air adopts a three-way structure, and each air volume is adjusted by a separate regulating baffle, so the burner is relatively complex.dmxBoiler Burner
2、 OrganizationdmxBoiler Burner
The dual-fuel burner is mainly composed of three parts: common part, fuel oil part and gas part.dmxBoiler Burner
1. Common partsdmxBoiler Burner
It includes air pipe, deflector used to control the direction of air flow, air branch pipe and fire-resistant flue. In addition, there is a small fire igniter, whose position should be able to reliably place fuel and gas. The position of fire detector shall be able to detect small fire, main flame of gas, and flame of oil (or coal). When a large gas supply system is installed in the fuel burner, it may interfere with the mixing mode of fuel combustion. The solution is to arrange the gas inlet outside the burner.dmxBoiler Burner
2. Fuel componentsdmxBoiler Burner
It is mainly an oil atomizer, whose function is to separate the oil and distribute the oil mist evenly into the air flow in a controllable way. The following types of atomizers are commonly used:dmxBoiler Burner
(1) Jet atomizerdmxBoiler Burner
The oil enters the swirl chamber through the air hole at the corner, and is ejected from the ring nozzle in a conical form, and dispersed into droplets. The oil pressure is generally between 0.35 and 1.4 MPa, up to 7.5 MPa. The viscosity of oil during operation is about 15 × 1030 m2/sec. The simple jet atomizer has some influence on the burner load regulation rate, but it can be improved by overflow and backflow. Because too much oil can flow back, the amount of oil entering the swirl chamber is certain regardless of the flow rate: a good swirl can be formed when the flow rate is large, and a certain thickness of oil mist flow can be maintained at the outlet.dmxBoiler Burner
(2) Steam assisted atomizerdmxBoiler Burner
This kind of atomizer was used in the early stage. The water vapor was led into the oil stream and broke in the oil stream to form fog. In the process of use, due to the large consumption of steam, the use of jet atomizer has a certain impact on it. In recent years, the model has undergone major reforms, and steam consumption has been significantly reduced.dmxBoiler Burner
3. Gas componentsdmxBoiler Burner
The gas components of the dual-fuel burner are all of nozzle mixing type. Because the oil atomizer occupies the central position of the stable area of the burner, the gas components are subject to certain restrictions. It can reach the central position by using detachable nozzle or ring cavity for heating; However, if the rotary cup oil mist atomizer is used at the same time, this cannot be achieved. In other design styles, when the load increases, the central air supply becomes difficult. Therefore, the gas enters through the ring pipe or nozzle arranged between the atomizer and the shell.dmxBoiler Burner
3、 Classification.dmxBoiler Burner
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 the site, with additional fans). The former type is mainly used in fire tube boilers, while the latter type is mainly used in water tube boilers. Generally speaking, the dual-fuel burner is formed around the existing fuel burner. The fuel injector has been installed in the center of the burner, and the gas must be introduced from the opening of the oil atomizer and the shell.