The operating environment of the desulfurization nozzle is relatively harsh. The corrosion of sulfurous acid and sulfuric acid, and the wear and corrosion caused by calcium sulfite, calcium sulfate and calcium carbonate particles are the primary factors affecting the operating function and service life of the nozzle. Therefore, the materials used for desulfurization nozzles are generally silicon carbide or ceramics, which not only have excellent resistance to sulfurous acid and sulfuric acid corrosion, but also have a wear resistance that is 15-30 times that of stainless steel. The most commonly used flue gas desulfurization nozzle materials in domestic flue gas desulfurization projects are silicon carbide (or silicon nitride) and stainless steel. The most widely used silicon carbide is the nitrogen-connected silicon carbide nozzle based on imported brands. The advantages of silicon carbide nozzles are low price and long service life, especially the wear resistance and acid and alkali resistance of silicon carbide.
One, Methods and precautions for selecting desulfurization nozzles
Because the operating environment of the desulfurization nozzle is relatively harsh, the following points should be paid attention to when selecting:
1. Nitrogen-connected silicon carbide (SNBSC), this material has anti-corrosion and anti-wear properties, but its cracking modulus is low and its impact resistance is poor. This material is mostly used in refractory materials for industrial furnaces and kilns.
2. Responsive connection of silicon carbide (RBSC), the material has anti-corrosion and anti-wear properties. RBSC is 5-7 times the cracking coefficient of SNBSC material. It is mostly used for manufacturing complex methods. RBSC is much more expensive than SNBSC material. This material is also not resistant to impact, and RBSC is mainly used in the manufacture of desulfurization nozzles. Because of the fragility of ceramic materials, it is difficult to predict the life of the nozzle. In terms of wear, the life of the nozzle is unknown, but no nozzle damaged due to wear has been seen. Generally, the damage to the nozzle is caused by cracking. Many factors that cause cracking are mainly: unreasonable installation process, pressure shock (water hammer) when the system is started, or blockage in the cleaning nozzle body, and unreasonable normal maintenance operations.
3. Cobalt Alloy 6 (CobaltAlloy6-AMS5387): It is a cobalt-based alloy with anti-corrosion and anti-rust functions. It is one of several alloys that can be used in limestone slurry scrubbing towers. The recommended operating pressure is 0.5-1bar, and its impact resistance is strong. It is generally used to manufacture spiral solid cone nozzle desulfurization nozzles.
4. Polyurethane is a kind of corrosion-resistant polymer. All MP series and TH series can be made of this material. The life cycle of this nozzle for desulfurization is 12-24 months.
Second, the distinction between desulfurization nozzle materials
The most commonly used flue gas desulfurization nozzle materials in FGD projects are silicon carbide (or silicon nitride) and stainless steel. The most widely used silicon carbide is the nitrogen-connected silicon carbide nozzle based on imported brands. With the understanding of the owners and environmental protection technicians, it is now gradually transformed into a reactive sintered silicon carbide nozzle. The advantages of reactive sintered silicon carbide nozzles are low price and long service life, especially the wear resistance and acid and alkali resistance of silicon carbide are relatively good.
There are two types of silicon carbide nozzles: tangential hollow cone and solid cone. Tangential hollow cone is divided into one-way tangential hollow cone, one-way tangential solid cone, one-way double-head tangential hollow cone, one-way double-head tangential solid cone, two-way hollow cone, two-way solid cone, etc. A solid cone is a spiral nozzle. The tangential hollow cone nozzle has stable and uniform atomization effect, and the free diameter is large and not easy to be blocked. Solid cone nozzle atomization is finer, but it varies greatly with pressure, and the free passage is small. Some desulfurization methods will easily block the nozzle.
The requirement for desulfurization effect is ultra-low emission. The nozzles used in most ultra-low projects are: one-way tangential hollow cone nozzle, one-way tangential solid cone nozzle and one-way double-head tangential hollow cone nozzle. Among them, the one-way double-head hollow cone nozzle is a product that has just emerged in recent years, and there are not many manufacturers of one-way double-head tangential hollow cone nozzles that can really meet the requirements. Stainless steel desulfurization nozzles are divided into two types: unidirectional tangential hollow cone and solid cone, but the classification of stainless steel unidirectional tangential hollow cone is simpler, divided into unidirectional tangential hollow cone and bidirectional hollow cone.
Comparison of nozzle products made of silicon carbide and stainless steel:
1. The service life of silicon carbide is 10 times or more than that of stainless steel.
2. Silicon carbide is brittle, so it cannot be opened with force after the game is blocked, and it is not easy to clean. Stainless steel can be cleaned with force.
3. The wear resistance of silicon carbide is much stronger than that of stainless steel.
4. The acid and alkali resistance of silicon carbide material is much stronger than that of stainless steel.
Three, The main purpose of desulfurization nozzle
Power plant flue gas desulfurization can be divided into dry method and wet method: dry method also requires the reaction of desulfurizer lime slurry with S02 to generate solid ash, which is then discharged through dust removal; wet method is to use (0.0l ~ 0.05) g/ Limestone water with L solubility, plus some other chemical solutions, spray and wash the flue gas through a large number of nozzles arranged in the absorption tower. In order to achieve a good absorption effect, the absorption tower is designed to be counter-current, and the limestone water is sent to the spray layer nozzles arranged at different heights in the tower through a circulating pump. Air for spray washing. The gas (gas) desulfurization method produced by the gasifier in the coal-fired combined cycle system is similar to the flue gas desulfurization method of the power plant. Generally, the coal-water slurry is burned in the fluidized bed, and the desulfurizer is often mixed with the smoke, which is sprayed through the nozzle. Burning in the furnace to produce gas. Part of the sulfur has been removed from the gas, and then it goes through a desulfurization device to remove H2S above 98% to obtain clean gas that is fed into the combustion chamber of the gas turbine.