Dry scrubbing for safety in extreme waste environments

Some waste gas generating environments are simply too dangerous or too volatile to clean using conventional filtration methods. That’s where dry scrubbing comes in. Typically, high temperature environments that generate so called “acid gases” (an acid gas is anything that contains a high concentration of sulphuric type gases or carbon dioxide) are not stable enough to have their atmospheres cleaned using wet scrubbing – a technique that collects the dust like or particulate waste from most hot gas processes. The dry form of air scrubbing uses sorbents, which are substances that absorb gas without the need for liquid – taking the acid gases straight out of the waste plumes. In general terms, the gases that have been treated by sorbents in dry scrubbing end up as salts or minerals, which can be disposed of safely and easily in their solid form.
The dry form of gas scrubbing has a particular advantage with respect to applications where exhaust pipes, chimneys or flues are not necessarily practical. The classic example is a submarine, which obviously is unable to have any kind of smokestack because it works underwater. Dry format gas scrubbing doesn’t give out any steam or smoke because it isn’t using water to saturate particulate waste: which means there is no need to find a vent for the sanitised waste product. Dry scrubbers have been used to take the carbon monoxide out of breathed air for decades, in both nuclear and conventional subs – the same technique can be applied to land based locations and applications where smoke stacks or exhausts are simply not practical.
Dry scrubbing doesn’t produce any waste water, which wet scrubbing obviously does. Handling that waste water can, it and of itself, become a fairly high intensity procedure, requiring time, money and space for proper resolution. Scrubbing air dry, rather than wet, completely removes the need for the often large waste water treatment and reclamation areas that the liquid form of hot gas cleaning can engender. That means that intensive industrial processes, which themselves have a hugely important safety purpose (including the disposal of bio hazardous material in certain field situations), can be completed without fear of secondary contamination, and without the need for giant processing pools or enormous quantities of water cleaning gear.
Dry scrubbing is done using two main techniques – either sorbent injection, or sorbent spray. In sorbent injection, the scrubber injects sorbents straight into a gas stream so they can crystallise the acid gases. In sorbent spray scrubbing, waste gas is drawn up into a processing chamber, where it is drenched in atomised sorbent – basically particles so fine they might as well be water. In spray scrubbing, the sorbent acts like a reverse version of the water in wet scrubbing. The water in wet scrubbing makes a paste out of dust type gas particles: the dust type particles of sorbent in spray scrubbing connect with the acid gases, which make a paste out of it. In both cases, dry scrubbing and wet scrubbing, the idea is to convert a gas into a solid so that it can be safely removed and dealt with.

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