Episode 119 | Sensational Scrubbers | Dry Scrubbers Users Association
Scrubbers are critical to the success of our energy portfolio. In my monologue, I point out that it hasn’t always been this way. Modern civilization has had to learn from its mistakes to ensure we have clean air and water. The United States alone has passed five amendments to the Clean Air Act since 1963.
The Dry Scrubber Users Association has been around since 2008. My guest, DSUA President Jerry Hunt, and I covered the gamut of scrubber technologies, however.
“All these technologies, there’s typically somewhat of a whack-mole effect,” says Jerry, pointing out that one scrubber can affect the next.
Typical pollutants and scrubbers are:
- Nitrogen oxides (NOx) — Causes smog. Selective Catalytic Reactors are the industry standard for scrubbing this out.
- Particulate Matter (PM) — Can lead to respiratory and cardio vascular issues. These are usually filtered out by a baghouse or an electrostatic precipitator.
- Acid Gases (Sulfur Dioxide, Hydrogen Chloride, also Mercury) — Can cause acid rain. Dry scrubbers and wet scrubbers are used.
DSUA, as the name implies, focuses mainly on the dry scrubbers for acid gases. Jerry listed three technologies:
- Spray Dryer Absorber (SDA)
- Circulating Dry Scrubber (CDS)
- Dry Sorbent Injection (DSI)
Much of the focus these days is on DSI, which Jerry says is more tolerant of hot flue gas temperatures and can essentially be placed in any order along the treatment sequence.
All of these dry scrubbers introduce pulverized media, typically calcium (i.e. lime, sodium bicarbonate), that comes in contact with the exhaust flue gas from a power plant and absorbs the gases. This mixture is commonly referred to as “cake.” Most of the media can usually be returned back to the scrubber. Once it is completely spent, the cake is sent to a landfill.
We discussed the misconceptions surrounding air quality from these plants. “It’s probably a lot cleaner than what people perceive coal to be,” says Jerry. For instance, HCl has to be 2 parts per million or less.
Despite all best efforts, coal will continue to decline. Jerry says the association is focused on industries outside the power sector, like smelters and cement plants. They are also looking abroad to expand and share knowledge. This came into focus during COVID, when many international guests joined their presentations.
“I think the US has a lot of great dry scrubbing experience,” he says, “and a lot of folks who participate, from a vendor perspective, have international capabilities to offer these solutions.”
For this reason, it is important that scrubber technology improve as well.
“In many cases people have solutions in place,” says Jerry. “The goal is how do you optimize solutions? How can we do it smarter, better, cheaper? We’re trying to keep coal alive and economic as long as possible and these folks that have these dry scrubbers as part of that.”
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