How to choose low nitrogen burner for gas boiler
- Author:Shenzhen Zhongli Weiye Electromechanical Equipment Co., Ltd.
- Origin:Shenzhen Zhongli Weiye Electromechanical Equipment Co., Ltd.
- Time of issue:2021-06-16 14:09
How to choose low nitrogen burner for gas boiler
On April 1, 2017, Beijing officially implemented the most stringent nitrogen oxide emission standards for boilers, requiring that the emission of nitrogen oxides from newly built boilers is less than 30 mg, and the emission of nitrogen oxides from boilers in use is less than 80 mg. In the future, this standard It will be gradually applied to various provinces and cities across the country. For most owners of gas-fired boilers currently in use in the market, it means that they must be replaced with low-nitrogen burners in order to meet the emission requirements.
Before understanding the low-nitrogen burner of gas boilers, let's first understand the formation mechanism of NOx nitrogen oxides:
thermal NOx is NOx generated by the oxidation of nitrogen in the air at high temperature, which is the main source of nitrogen oxides in air pollution. primary source. For gas-fired boilers, the generation of thermal NOx has an exponential relationship with the combustion temperature, which usually begins when the combustion temperature is higher than 1000 degrees Celsius, and the generation rate of NOx increases sharply above 1400 degrees Celsius. The graph below reflects the relationship between NOx emissions and temperature for gas-fired boilers.
Based on the above NOx generation mechanism, the NOx control technology of gas boiler low-nitrogen burners mainly focuses on two directions:
① Reduce the flame temperature
② Reduce the oxygen content of the air
Low NOx and Ultra-Low NOx Burner Types
Conventional gas boiler burners typically emit around 120-150 mg of NOx. Gas boiler low-nitrogen burners usually refer to burners with NOx emissions of 30-80 mg. NOx emissions below 30 mg are commonly referred to as ultra-low NOx burners.
Gas boiler low nitrogen burners are usually based on the following technologies:
1. Electronic proportional regulation and oxygen content control technology to precisely control oxygen content;
2. FGR flue gas recirculation technology to reduce flame temperature and oxygen content;
3. Fully premixed surface Combustion technology to reduce flame temperature and achieve full combustion.
Among the above technologies, 1 is usually a necessary configuration for low-nitrogen burners of gas-fired boilers; based on the above technologies, gas-fired low-nitrogen burners in the market are mainly divided into the following types:
1. FGR low-nitrogen burners
FGR low-nitrogen burners can usually reduce NOx in It is controlled to 65 mg in the full fire range, and the limit is about 40 mg. Further reduction of NOx emission may lead to unstable combustion, or sacrifice of adjustable ratio and other disadvantages.
2. Surface-burning ultra-low NOx burners
Surface-burning ultra-low NOx burners are usually able to control NOx to within 30 mg over the full fire range. The advantage is that it is simple to install and does not require FGR flue gas recirculation piping; its main disadvantage is that The air needs to be filtered, which increases the maintenance workload; at the same time, the oxygen content is about 7%, which reduces part of the combustion efficiency.
3. Surface combustion + FGR ultra-low nitrogen burner.
Surface combustion + FGR ultra-low nitrogen burner combines the NOx control advantages of surface combustion and the advantages of FGR oxygen reduction, which can control NOx to 20 mg in the full fire range, while controlling the oxygen content within 3%, maximizing combustion efficiency . The main disadvantage is the high equipment cost.
Main parameters to consider when choosing a low nitrogen burner for gas boilers
Tail Oxygen Content
The limit excess air factor to achieve full combustion is about1.1, corresponding to a theoretical tail oxygen content of about 2%. Higher tail oxygen content generally means a reduction in burner efficiency. The ideal burner tail oxygen content can be controlled within 3%; the tail oxygen content of surface-burning burners on the market is usually around 7%. Compared with 3% tail oxygen content, it means that the same amount of heat is generated, but more consumption is required. About 6-8% natural gas. For owners who operate year-round or whose equipment runs at a high load for a long time and consumes a large amount of natural gas, choosing a burner with low tail oxygen content is crucial to reducing operating costs.
Low nitrogen burners that use electronic proportional adjustment should usually have a high turndown ratio of at least 5:1 .
A lower turndown ratio means moreON/OFF starts and stops during actual operation, which also means more natural gas consumption. Unless it is a boiler with a relatively small and stable load all year round, choosing a burner with a high adjustable ratio is very important to reduce natural gas consumption, reduce operating costs, and extend the service life of equipment.
Other main considerations
Combustion stability is the main consideration in choosing a low nitrogen burner for gas boilers, including the reliability of the equipment itself. Forlow-nitrogen burners using FGR technology, special attention should be paid to the FGR flue gas recirculation ratio. Excessive ratio means that the combustion is easily unstable, or there are strict requirements for the technology and control level of the equipment.
The above is the relevant knowledge about low-nitrogen burners of gas boilers. If you need to know more relevant information, please consult online customer service, we will serve you wholeheartedly. The low-nitrogen boiler independently developed by ZOZEN stands out in the boiler market by virtue of the advantages of high thermal efficiency and low NOx emission, and its users are in many industries such as food, paper, rubber, building materials, and chemical industry.