Increase in calorific value of organic waste liquids
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Dear seniors, at present, the high-concentration waste liquids in our company have a high water content and a low calorific value; therefore, natural gas is required to assist in their combustion. There is now an idea: by evaporating and concentrating wastewater, could its calorific value be increased?
A higher water content means a lower calorific value; doesn’t concentrating wastewater require more energy? A simple heat balance will make it clear. To give a simple example, the combustible portion in your wastewater is equivalent to 1 kg of standard coal, with a calorific value of 7000 kcal. When completely burned, it can vaporize 7000/500 = 14 kg of water, assuming that the latent heat of vaporization of water is 500 kcal/kg. This is just an approximate estimate; accuracy isn’t necessary. . Well, if the amount of waste liquid you have is 1+14=15 kg, then you hardly need to supply any additional heat. 1 kg of standard coal is sufficient to evaporate 14 kg of water. But if the amount of water exceeds 14 kg, you will need to supply heat. For example, if the amount is now 1+15=16 kg, meaning there’s an extra 1 kg of water, and you use some other method to concentrate and evaporate this extra 1 kg of water, won’t that also require energy? Of course, you could say things like using multi-effect evaporation, and there are more devices involved as well; the process becomes more complex. Organic waste liquids may emit unpleasant odors at high temperatures, and there can also be issues such as corrosion and other problems. . . It’s not annoying enough; direct afterburning is the simplest solution. For environmental protection devices, simplicity and reliability are of utmost importance. . In simple terms, burning organic waste liquids with a low calorific value means using fuel to heat boilers, and the steam produced can hardly be utilized. . . The incineration of organic waste liquids is an environmentally friendly process with high costs, and it is only natural to pay such a price.
This post was last edited by qugd on 2017-5-8 at 17:26. What the user on the second floor said is absolutely true. To evaporate a little water, adding more equipment, processes, and costs might simply not be worthwhile. Sometimes, some measures that seem to promote energy conservation and emission reduction actually end up consuming more energy and generating more emissions when implemented.