Fourth, spray method
In order to suppress the generation of NOx, it is desirable to determine the lowest point of NOx reduction without impairing the combustion stability when spraying water or steam into the flame.
Generally, the water spray has the effect of reducing the NOx concentration for the combustion of liquid and gaseous fuel, but the injected water must reach the highest temperature band of the flame. When water is sprayed, it is effective to atomize the water and then spray it to the flame. However, if the atomization is excessive, the final velocity of the droplet will decrease, and the droplet will only flow along the periphery of the flame, but cannot reach the highest point in the center of the flame. The flame temperature zone, so that the flame temperature can not be fully reduced, the rate of decline of NOx is less than expected and degree. Therefore, when the water spray method is used to suppress NOx production, the droplets should not be too small, but should have a certain end speed so that they can enter the maximum temperature zone of the flame.
For the combustion of liquid fuels, the liquid fuel must first be atomized. There are a variety of methods for atomizing liquid fuel into a number of tiny droplets. One of the methods is the use of aerodynamics. A high pressure gas stream or water vapor can be used as a fuel spray medium. Water vapor is mixed with atomized droplets and oxidizers and fed into the combustion chamber. Using this method, NOx production can be reduced.
Fifth, the oil-water emulsion combustion
In order to enhance the combustion process of oil and save fuel, some of the water may be added to the oil, or the oil originally contains more water (for example, caused by directly heating the oil with steam), and is strongly stirred to make them oily and floating. The liquid then burns through the oil atomizer.
1, emulsified oil
In order to have good combustion performance after oil is mixed with water, the water must be dispersed in the oil into very fine particles and be emulsified to form a water-in-oil type, in which the oil is a continuous phase and the water is a dispersed phase.
The methods for preparing emulsified oils can be classified into three categories:
(1) Mechanical method. The simplest is to add water in front of the pump and it can be emulsified by several cycles of the pump. Special mixers can also be used to help ensure emulsification quality.
(2) Ultrasonic method. In recent years, our successful piezoelectric phacoemulsification device is a highly efficient emulsifier.
(3) pneumatic method. High-pressure air or steam is stirred through the water-oil mixture. The water produced by this method is large and not uniform enough.
The emulsification of oil should have a certain stability in addition to the fact that the dispersed phase (water) is as uniform and fine as possible. Generally, the stability of the water-in-oil type emulsion is often measured by the length of time the oil-water is not layered, deformed, and demulsified. In order to improve its stability, a method of adding a surfactant is widely used. There are generally four types of active agents:
(1) Anionic types such as phthalates, sulfates, and phosphates.
(2) Cationic types, such as simple amine salts and scavenging amine salts.
(3) Non-ionic, including lipids (such as fatty acid polyvinyl chloride), ethers (such as fatty alcohol polyoxyethylene ether), and guanamines (alkylamines).
(4) Zwitterionics, such as carboxylic acids and sulfates.
2, the nature of oil and water emulsion
After the oil is mixed with water, the properties of the oil-water emulsion and the properties of the original oil have been greatly changed, mainly in the following aspects:
(1) The viscosity of the oil-water emulsion increases because of new internal friction between the two phases. The increase in viscosity is related to water content, viscosity of the original oil, and temperature.
(2) The freezing point is increased, generally up to 11~25°C.
(3) The density increases, and the density of the emulsion corresponds to the density of the mixture of oil and water produced in a certain proportion.
(4) Increased surface tension.
(5) Large thermal conductivity.
3, oil mixed with water combustion
Oil-water burning
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