Development history of low-temperature denitrification catalysts
Publishdate：2021-04-23 Views：21
Low temperature denitrification catalystIt is of great help to improve the efficiency of denitrification, and the low-temperature denitrification catalyst developed by technology is looking forward to serving you.
The harmful substances such as smoke, sulfur dioxide, and nitrogen oxides (NOX) contained in flue gas are the main causes of environmental problems such as air pollution, acid rain, and greenhouse effect. How to effectively remove SO2 and NOX from flue gas has attracted the attention of researchers around the world. The widely used desulfurization technology in the world today is flue gas desulfurization (FGD), among which wet FGD has high desulfurization efficiency but is difficult to use for denitrification. This is because the main component of NOX in flue gas is NO, which accounts for more than 90% of the total amount. It is a colorless, odorless, and inactive gas that is almost not absorbed in water or alkaline solution, except for generating complex compounds.
Due to the significant proportion of wet desulfurization in the current FGD market, making corresponding improvements to this method for simultaneous desulfurization and denitrification will have great development prospects. In order to effectively absorb NOX, it is necessary to oxidize the NO in the flue gas to NO2/NO=1-1.3. At low concentrations, the oxidation rate of NO is very slow. Therefore, the oxidation rate of NO becomes the determining factor for the total rate of NOX removal by absorption method. To accelerate the oxidation of NO, oxidants can be used for direct oxidation.
In recent years, the method of adding chemical reagents to the liquid phase has been widely attempted. Among them, wet denitrification additives have been proven to be effective. The denitration additive oxidation-reduction method uses a wet flue gas denitration agent to oxidize NO to NO2, and then reduces NO2 to N2 with a water solution. This method can be combined with wet flue gas desulfurization technology using CaCO3 (limestone) as a desulfurizer. The reaction product of desulfurization can also serve as a reducing agent for NO2. The denitration rate of the wet flue gas denitration agent can reach 95%, and it can desulfurization simultaneously.
As early as the late 1970s, foreign flue gas denitrification institutions studied the absorption of NOX by wet flue gas denitrification agent solutions. In the 1990s, they used semi batch stirring containers with flat gas-liquid interfaces. Similar experimental studies were conducted using packed columns and stirred tanks, and based on this, simultaneous desulfurization and denitrification were attempted using spray towers and bubbling columns, respectively. The denitrification methods are divided into two types: dry denitrification and wet denitrification. The dry denitrification efficiency is around 80%, with large investment, large land area, high cost, and high operating costs; Wet denitrification has the advantages of small investment, small footprint, low cost, low operating costs, and can be organically combined with existing desulfurization technologies to achieve denitrification. It has the advantages of simple operation and convenient use.
Wet denitrification additives have water absorption, are soluble in water, and have strong oxidizing properties. The reaction of wet denitrification additive solution for removing NOX is relatively complex, and many scholars have gained a certain understanding of the reaction mechanism after conducting research in this area. This is a gas film controlled absorption oxidation reaction, where NOX is mainly absorbed through the hydrolysis of N2O3 and N2O4, and NO can be quantitatively oxidized by wet flue gas denitration agents in aqueous solution.
Although soluble in water, it cannot generate nitrogen-containing oxygen-containing acids. At 0 ℃, one volume of water can dissolve 0.07 volumes of NO, making it difficult for NO to dissolve in water. However, in wet flue gas denitrification agents, there is enough water to dissolve NO in water. Research has shown that when the nitric acid content in the aqueous solution is greater than 12%, the solubility of NO is much higher than in pure water. That is, a single accumulated water can dissolve 7 volumes of NO, and when the flue gas begins to dissolve in water, the water is pure. Firstly, NO2 dissolves in water to generate HNO3. If NO2 is not reduced in water, according to the ratio of wet denitrification additives in water, the nitric acid content in the aqueous solution is about 12%. Therefore, it can be said that NO dissolves in water without any problem.
Using a small spray tower device, all equipment includes a smoke simulation system, a spray tower, and a detection and analysis system.
Before adding compressed air, NO is first diluted by N2 in mixer 1 to avoid generating a large amount of NO2. The diluted NO is diluted again by compressed air with controlled flow rate in mixer 2 to adjust to the desired concentration. Before entering the spray tower, the simulated flue gas is heated to working temperature by an electric control heater, and then absorbed in the spray tower. Experimental analysis measures the concentrations of SO2, NO, and O2 in the gas, the size of spray droplets, and the concentration of various ions generated in the absorption solution after the reaction.
Low temperature denitrification catalystIt is of great help to improve the efficiency of denitrification, and the low-temperature denitrification catalyst developed by technology is looking forward to serving you.
The harmful substances such as smoke, sulfur dioxide, and nitrogen oxides (NOX) contained in flue gas are the main causes of environmental problems such as air pollution, acid rain, and greenhouse effect. How to effectively remove SO2 and NOX from flue gas has attracted the attention of researchers around the world. The widely used desulfurization technology in the world today is flue gas desulfurization (FGD), among which wet FGD has high desulfurization efficiency but is difficult to use for denitrification. This is because the main component of NOX in flue gas is NO, which accounts for more than 90% of the total amount. It is a colorless, odorless, and inactive gas that is almost not absorbed in water or alkaline solution, except for generating complex compounds.
Due to the significant proportion of wet desulfurization in the current FGD market, making corresponding improvements to this method for simultaneous desulfurization and denitrification will have great development prospects. In order to effectively absorb NOX, it is necessary to oxidize the NO in the flue gas to NO2/NO=1-1.3. At low concentrations, the oxidation rate of NO is very slow. Therefore, the oxidation rate of NO becomes the determining factor for the total rate of NOX removal by absorption method. To accelerate the oxidation of NO, oxidants can be used for direct oxidation.
In recent years, the method of adding chemical reagents to the liquid phase has been widely attempted. Among them, wet denitrification additives have been proven to be effective. The denitration additive oxidation-reduction method uses a wet flue gas denitration agent to oxidize NO to NO2, and then reduces NO2 to N2 with a water solution. This method can be combined with wet flue gas desulfurization technology using CaCO3 (limestone) as a desulfurizer. The reaction product of desulfurization can also serve as a reducing agent for NO2. The denitration rate of the wet flue gas denitration agent can reach 95%, and it can desulfurization simultaneously.
As early as the late 1970s, foreign flue gas denitrification institutions studied the absorption of NOX by wet flue gas denitrification agent solutions. In the 1990s, they used semi batch stirring containers with flat gas-liquid interfaces. Similar experimental studies were conducted using packed columns and stirred tanks, and based on this, simultaneous desulfurization and denitrification were attempted using spray towers and bubbling columns, respectively. The denitrification methods are divided into two types: dry denitrification and wet denitrification. The dry denitrification efficiency is around 80%, with large investment, large land area, high cost, and high operating costs; Wet denitrification has the advantages of small investment, small footprint, low cost, low operating costs, and can be organically combined with existing desulfurization technologies to achieve denitrification. It has the advantages of simple operation and convenient use.
Wet denitrification additives have water absorption, are soluble in water, and have strong oxidizing properties. The reaction of wet denitrification additive solution for removing NOX is relatively complex, and many scholars have gained a certain understanding of the reaction mechanism after conducting research in this area. This is a gas film controlled absorption oxidation reaction, where NOX is mainly absorbed through the hydrolysis of N2O3 and N2O4, and NO can be quantitatively oxidized by wet flue gas denitration agents in aqueous solution.
Although soluble in water, it cannot generate nitrogen-containing oxygen-containing acids. At 0 ℃, one volume of water can dissolve 0.07 volumes of NO, making it difficult for NO to dissolve in water. However, in wet flue gas denitrification agents, there is enough water to dissolve NO in water. Research has shown that when the nitric acid content in the aqueous solution is greater than 12%, the solubility of NO is much higher than in pure water. That is, a single accumulated water can dissolve 7 volumes of NO, and when the flue gas begins to dissolve in water, the water is pure. Firstly, NO2 dissolves in water to generate HNO3. If NO2 is not reduced in water, according to the ratio of wet denitrification additives in water, the nitric acid content in the aqueous solution is about 12%. Therefore, it can be said that NO dissolves in water without any problem.
Using a small spray tower device, all equipment includes a smoke simulation system, a spray tower, and a detection and analysis system.
Before adding compressed air, NO is first diluted by N2 in mixer 1 to avoid generating a large amount of NO2. The diluted NO is diluted again by compressed air with controlled flow rate in mixer 2 to adjust to the desired concentration. Before entering the spray tower, the simulated flue gas is heated to working temperature by an electric control heater, and then absorbed in the spray tower. Experimental analysis measures the concentrations of SO2, NO, and O2 in the gas, the size of spray droplets, and the concentration of various ions generated in the absorption solution after the reaction.
