Low-nitrogen combustion

1. The calorific value of coke oven gas ranges from approximately 16,720 to 18,810 kJ/m^3, while natural gas and liquefied petroleum gas have a calorific value several times higher. Both of the latter types come equipped with low-nitrogen burners; so what is wrong with coke oven gas, or are there any other special requirements from the client? 2. Gas combustion produces excessive NOx due to high flame temperatures; therefore, there are many measures to reduce these temperatures, both structural and operational in nature. Among them, grading is one of the main structural measures, while the accompanying diagrams represent the main measures for low-nitrogen combustion technology. As an extreme example, if the burner is designed in the style of a household gas stove, the flame temperature will not be too high. I remember that over a decade ago, when the promotion of low-nitrogen combustion began in China, one company proposed a solution that involved using the burners from multiple gas stoves as alternatives to high-power burners. Although we rejected this idea, it still represented an early form of low-nitrogen combustion technology. From a practical perspective, as long as the total heat supply meets the requirements and helps achieve low nitrogen levels, while the investment cost is low, why not do it? 3. The building owner requires a flame temperature of over 700 degrees, probably due to the requirements related to melting lead. For flames, a lit cigarette can also reach this temperature, and the generation of NOx at such a temperature is very low. The combustion of single-component gases such as H2 can reach 2100°C, while the combustion of methane can reach 1950°C. It is necessary to reduce the temperature by optimizing the burner structure and operation in order to suppress the generation of NOx. 4. In addition to optimizing the burner structure, from an operational perspective, since lead can melt at 700 degrees, it is not advisable to supply too much heat that would cause the furnace temperature to rise excessively. The accompanying diagram also shows the relationship between furnace temperature and NOx generation for reference. 5. There is currently a lot of information on the internet regarding products and patents related to low-nitrogen burners for coke oven gas; this information should not be taken entirely at face value, nor should it be completely dismissed. If such burners are indeed needed, it is necessary to test them in practice to see the actual results. Of course, it is necessary to have experts who can evaluate the experimental process and results; it would be even better if we could get *** the all-knowing expert: lol.

Generally speaking, in coal-fired boilers or other gas burners, there is indeed a possibility that the combustion temperature affects the amount of NOx generated, but this usually applies to temperatures above 1300°C. At 700°C, it is by no means a high temperature for combustion, and temperature does not constitute a decisive factor affecting NOx generation

Sure, 700 degrees isn’t high; there are likely many companies that can handle it. You should check with a few more companies.

1. There is a difference between the furnace temperature and the flame temperature; examples are provided to illustrate this. 2. The attached table shows 4 combustion scenarios, in which the composition of the fuel, as well as the temperature/pressure conditions and consumption rates, remain constant. It is assumed that there is no heat loss from the furnace. The differences among these scenarios and their corresponding results are as follows: 2.1. When dry air is used to supply oxygen for combustion, with zero excess air and no other cooling loads, both the flame temperature and the furnace temperature are 2161°C. 2.2. When 100% humid air is used to supply oxygen for combustion, with zero excess air and no other cooling loads, the flame temperature and furnace temperature are 2113°C. 2.3. Again, 100% humid air is used for combustion, with zero excess air; however, an equal amount of humid air is introduced into the furnace to absorb heat. In this case, the furnace temperature is 1234°C. 2.4. Still using 100% humid air for combustion and zero excess air, but this time twice as much humid air is introduced into the furnace to absorb heat. The furnace temperature in this scenario is 619°C. 3. The above comparisons aim to illustrate one point: the flame temperature depends on the fuel and oxidizing air involved in combustion, while the furnace temperature is greatly influenced by cooling loads. In the above example, since the fuel remains unchanged, only the difference in the air used for combustion affects the flame temperature ； The cooling load does not contribute to combustion but acts only as a heat absorber, causing significant changes in the furnace temperature. Of course, the furnace temperature also has a slight influence on the flame center temperature, but it is not the main factor. 4. The 700℃ mentioned in the topic of this floor is not the temperature at which the flame burns, but rather the temperature required for melting lead; it is the equilibrium temperature achieved when the heat released by the fuel is balanced by the heat absorbed by the melting lead. When the amount of molten lead is low, less fuel is needed; otherwise, the furnace temperature rises, and vice versa. It is not closely related to the burner flame temperature; even with non-low-nitrogen burners, the flame center temperature can still exceed 1200°C, so modification is meaningful.