Some questions about ammonia-based desulfurization
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We have just taken on a project to prepare a feasibility study for a fertilizer factory, involving a waste heat boiler for blowing air that produces sulfuric acid as a by-product of the ammonia-based desulfurization process. I have a few questions I would like to ask the experts. First, the flue gas at the boiler outlet contains about 2 grams of dust per cubic meter; how can it be ensured that the sulfuric acid AN produced meets the dust standards? How to remove dust before ammonia-based desulfurization? Using a water film for dust removal would likely result in all the sulfur being removed as well. Secondly, the resistance of the desulfurization tower at the back must be considerable; what is an appropriate wind pressure for the boiler exhaust fan? Please advise.
This post was last edited by fangqiong on 2011-1-27 at 12:42; a cyclone + belt can be used for the front part, but the rest are probably not suitable. The fan pressure depends on the resistance of your desulfurization tower; the gas must be dried after passing through the tower before it can reach the fan. The pressure of the fan = the sum of the cyclone resistance, bag filter resistance, desulfurization tower resistance, pipe bends, and dryer tower resistance, multiplied by around 1.2; this is specified in the design manual.
2 grams per cubic meter is an extremely high value! The resistance of the bag filter is too high; why not use electrostatic dust removal?
A dust concentration of 2 g/m3 in the flue gas is too high; it makes it difficult to ensure the quality of the final desulfurization by-product, sulfuric acid. It is recommended to improve dust removal from this flue gas, for example by using an electrostatic precipitator with an additional electric field or by employing highly efficient bag filters； If wet dust removal is used, a simple water film system is not sufficient for achieving effective dust removal; it is recommended to use power wave dust removal or Venturi dust removal, although this results in a higher pressure drop ； The resistance of the desulfurization tower is not high; in particular, the resistance of the tower without spraying is relatively low.
Desulfurization equipment cannot be used as a dust collector.
Sulfuric acid AN seems to be somewhat useful; it’s best to use a bag filter beforehand, otherwise dealing with the by-products becomes quite difficult. Excess dust levels have a significant impact on crystallization within the tower; not only is the purity of sulfuric acid low, but the crystallization quality is also poor. Even with an external crystallization process, it is necessary to remove lime from the slurry; otherwise, it will cause problems once it enters the evaporator.
The reason is not that simple; for the project carried out by Jiangnan Environmental Protection at the Hubei Fertilizer Plant, bag filters were already in use before desulfurization, and it seems there were still issues. It seems that the products formed inside the ammonia tower are not that simple.
A dust collector must be installed after the boiler exhaust; the exhaust first passes through the dust collector and then the absorption tower. As for the exhaust fan, you need to perform resistance calculations; generally, 1200 Pa is sufficient for towers
Sulfuric acid AN is a by-product of ammonia-based flue gas desulfurization. There is already an industry standard for it – DL/T808-2002 \"By-product Sulfuric Acid AN\", which applies to \"Sulfuric Acid AN produced as a by-product of ammonia-based flue gas desulfurization in thermal power plants\". The key quality requirements for this sulfuric acid AN include total nitrogen content, moisture level, and free acid content; in addition, it is required to have a white or off-white appearance.
We have just taken on a project to prepare a feasibility study for a fertilizer factory, involving a waste heat boiler for blowing air that produces sulfuric acid as a by-product of the ammonia-based desulfurization process. I have a few questions I would like to ask the experts. First, the flue gas at the boiler outlet contains about 2 grams of dust per cubic meter; how can it be ensured that the sulfuric acid AN produced meets the dust standards? How to remove dust before ammonia-based desulfurization? Using a water film for dust removal seems... Published by Geng Yanli on 2009-3-5 09:54. The by-products of ammonia-based desulfurization inevitably contain heavy metals. Dust removal is necessary both before and after desulfurization; the key is to remove heavy metals. Everyone is aware of the dangers of heavy metals (especially mercury). When used as agricultural fertilizers, these heavy metals accumulate in the fruits of crops, and from there they accumulate in the human body. Over time, an excess of heavy metals in the body can lead to serious consequences.
It is not very practical to discuss the removal of heavy metals at the moment; measuring Hg in actual flue gases is a problem in itself.