In ammonia-based desulfurization, how is it best to remove heavy metal wastewater from the system?

Before carrying out ammonia-based desulfurization, the flue gas must be dust-removed; otherwise, the ammonia-based desulfurization process cannot operate.

First, figure out what ammonia-based desulfurization is Ammonia-based desulfurization uses ammonia water as the desulfurizing agent. The flue gas from the boiler enters the desulfurization tower, where it is absorbed by circulating ammonia water to produce sulfurous acid. The desulfurized flue gas is then purified through mist removal, passes through a heat exchanger for heat exchange, and is finally released into the chimney. The absorbent, ammonia water, is mixed with the absorption liquid and fed into the absorption tower. The sulfurous acid formed as a result of absorption is oxidized at the bottom of the absorption tower to form an ammonium sulfate solution; after evaporation and crystallization, solid-liquid separation, drying, and packaging, the final product, ammonium sulfate, is obtained. Therefore, the most important aspect of ammonia-based desulfurization is corrosion prevention.

Hehe, it seems to be another person who uses the ammonia method without discharging wastewater. Have you ever wondered where the heavy metals from ammonia-based desulfurization go? We can’t just look at the absorption by ammonia; we also need to consider the formation of other substances during that absorption process, right?

Before ammonia-based desulfurization, efficient dust removal is usually carried out; as a result, the dust concentration in the flue gas is already very low, and thus the level of heavy metals is also low. Moreover, filter units are installed before the ammonium sulfate production equipment during the ammonia-based desulfurization process (most of the heavy metals, along with a small amount of dust, precipitate under alkaline conditions and are thus filtered out). Additionally, thanks to the efficient dust removal done earlier, the dust that enters the ammonia-based desulfurization system is generally in gaseous form, and it is hardly removed during the washing and absorption processes; therefore, there is little to no heavy metals left at this point. No substance can be completely absent; it’s merely a matter of whether it has an impact, or whether that impact renders the method infeasible. What do you think?

On the 3rd floor, CDPulin is answering a question that isn’t being asked. Ammonia-based desulfurization requires a relatively low dust content in the flue gas; there is little heavy metal entering the system, and part of it can be removed by discharging the acid sludge. Additionally, some studies suggest that certain heavy metal ions such as Mn, Co, and Cu act as catalysts for the oxidation of sulfites. The effect of fly ash on crystallization is likely to be more of an encapsulation effect.

If 150 mg/m3 of dust still enters the desulfurization unit after electrostatic dust removal, considering a boiler with a capacity of 220 tons, is this amount of dust considered low or high? The flue gas volume is generally around 200,000 standard cubic meters.

The original post was posted by cxlcxl on 2009-3-17 at 13:25. If 150 mg/m3 of dust still reaches the desulfurization unit after electrostatic dust removal, considering a boiler with a capacity of 220 tons, is this amount of dust considered small or large? The flue gas volume is generally around 200,000 standard cubic meters. The person upstairs asked quite detailed questions. Could you reveal what it specifically does? A dust concentration of 150 mg/m3 should be fine. The best scenario is high sulfur content and low dust content, while the worst scenario is low sulfur content and high dust content.

Electrostatic dust removal can generally remove dust particles of 2 microns or larger, as well as even smaller particles. Dust at a concentration of 150 mg/Nm3 is mostly in gaseous form; it passes through the ammonia-based desulfurization tower without having its dust particles removed, as the tower only absorbs SO2. Dust at 150 mg/Nm3 still ends up in the flue gas discharged outside, as it cannot be removed by the desulfurization tower. You can first learn about the particle size ranges and efficiency of wet methods, bag filters, and electrostatic dust removal. That way, it will be clear.

Also, introducing dust-laden flue gas into the desulfurization device does not mean it enters the desulfurization liquid, nor does it mean it enters the ammonium sulfate solution. It’s the same as before: it’s not that there’s absolutely none, but rather very little or just a trace.

Maybe you’re just thinking about it in theory? I pulled out a large amount of mud from the site; how can that be justified as not causing secondary pollution?