What are the methods for treating the vapor phase at the top of the nitric acid storage tanks in various installations?
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Currently, the plant has two nitric acid storage tanks, each with a capacity of around 2,000 tons. During summer, nitric acid undergoes thermal decomposition under exposure to sunlight and high temperatures. After decomposition, a small amount of yellow smoke (nitrogen oxides) is released from the top vent. I would like to ask all the experts here: how do you recover the gaseous phase from your nitric acid storage tanks, or what effective treatment methods do you recommend?
For the treatment of the gas phase at the top of nitric acid storage tanks, common methods include the following: 1. Discharging the gas into the air through exhaust pipes – this is a fairly common approach, but it may cause pollution to the environment. 2. A gas recovery device is used to collect the gas for processing and utilization. For example, gases can be fed into a reactor for a catalytic reaction to convert nitrogen oxides into harmless nitrogen and water vapor. 3. A spraying system is installed at the top of the nitric acid storage tank; by spraying certain chemical reagents, nitrogen oxides are converted into harmless substances. For example, reagents such as sulfur dioxide or sodium nitrite can be used for the reaction. It is necessary to select an appropriate gas treatment method based on the actual circumstances, and to strictly comply with relevant environmental protection regulations and standards in order to ensure production safety and meet environmental requirements. .
For the nitrogen oxides emitted during the venting of nitric acid storage tanks, the following treatment methods are available: a vent opening as high as possible is installed at the top of the tank, and it is connected to a nitrogen oxide treatment system. Gases emitting nitrogen oxides are introduced into a treatment system for processing. Oxidants are used to oxidize nitrogen oxides into harmless substances. For example, oxidizing NOx to nitrogen dioxide (NO2), or oxidizing ammonia to nitric acid (HNO3). Use an absorbent to absorb nitrogen oxides in the exhaust gases. Common absorbents include ammonia water and alkaline solutions. Reduce the gas concentration in the storage tank to minimize emissions. For example, a pressure retention valve and a pressure relief valve can be installed at the top of the storage tank to maintain the pressure inside the tank
Nitrogen oxides are emitted into a spray tower and treated with urea solution
A water seal can be considered, or an alkaline scrubber can be added, along with sodium thiosulfate for absorption.