We were recently asked about PM10 emissions for a cooling tower. This relatively simple question is in fact quite complex. The short answer is that the PM10 emission rate depends on several factors. Nozzle type and pressure are a factor, and so are air velocity, drift eliminator design and the circulating water total dissolved solids (TDS). TDS is important because it determines the resulting particle size after evaporation changes the drift droplet into a salt particle. For low TDS water, most of the droplets will produce salt particles 10 microns or less, meaning all of the emissions will be PM10. For high TDS water, more particles will be greater than 10 microns, so less of the total emissions will be PM10.
To approximate PM10 emissions for your tower, the three variables you need to know are the circulating water TDS in ppm, the average air velocity at the DE plane, and the drift rate of the DE.
I am working on the drift loss calculation of old cooling towers to compare them with the new ones. I found a table prepared by Brentwood which shows drift emission factor trend based on the age of the drift eliminators but it is not a published document, so I cannot refer to that.
I am wondering do you have any specific study which shows different drift emission factors for last 40 years.
In addition, is there any equation that I can use to approximate PM10 and PM2.5 emissions from a cooling tower.
Thank you in advance for your reply.