What are the causes of dust formation in the exhaust gas from granulation towers? How to manage it?

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Reply to 1# Qingxin Ningjing 1: The large amount of urea dust generated during the urea production process – to analyze the reason for the high dust concentration in the exhaust gases from the urea granulation tower, it is related to the large amount of dust produced inside the tower. Dust generation is influenced by operating conditions and granulation equipment, and the main reasons are: 1) The granulation nozzles cause a large amount of dust to be produced. If there is scale buildup inside the nozzle, urine will form larger droplets, resulting in incomplete solidification of the urea particles. These incompletely solidified particles can develop cracks or shatter due to water evaporation during the cooling process. The poor smoothness of the nozzle orifices makes it easy for tiny urine droplets to form during the granulation process; these droplets solidify to form dust, which can easily be carried away by the cool air in Philadelphia. 2) The melt temperature is high. A higher temperature of the urea melt fed into the nozzle will cause more water to evaporate, leading to the formation of tiny droplets that result in dust. Experience shows that molten material at 145°C produces about 10% more dust than that formed at 138°C. 3) Form molten material mist. The wind speed distribution inside the tower is uneven; particularly in the area near the nozzles, molten material mist can scatter, thereby forming urea dust particles. 4) Mechanical wear. The impact wear between the sprayed particles and the tower bottom plate can generate tiny urea dust particles. 5) The levels of free NH3 and CO2 in the molten material are high. At the moment this molten material exits the granulation nozzle, as the pressure drops rapidly, NH3 and CO2 evaporate from the urine, carrying along tiny urea droplets and thus forming dust. 6) The temperature inside the tower is high, resulting in poor cooling effects, low urea strength, and excessive dust generation. 2. Affected by natural conditions: Different regions have varying natural conditions; as a result, there are significant differences in the temperature and humidity of the cooling air supplied. When the air temperature is high, the cooling effect inside the tower is poor, more dust is generated during production, and the dust concentration in the exhaust gases is high ； With low air humidity, the dust purification capacity inside the tower is reduced, which also leads to an increase in the dust concentration in the exhaust gases.

The technology and design for urea granulation in tall towers are quite mature; therefore, not installing a dust recovery system in new projects can meet environmental assessment requirements.

Watching the white smoke rising from the three granulation towers in front of my home every day is really unpleasant – firstly, it’s impossible to deal with the excessive dust, and secondly, it causes environmental pollution

Environmental protection standards certainly cannot be met; it’s best to have a dust removal system

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