Unusually shaped rain water cisterns, mobile liquid manure tanks, aquaculture tanks with special requirements – the family-owned company manufactures them all by rolling fiberglass mats into negative forms and fixating them with polyester resin.
Polyester resin contains styrene as a solvent and reactant. While not specifically toxic, the odor of styrene is extremely penetrating and affects many people strongly. While the emissions were for the most part bekow regulatory limits, the factory was situated in a mixed use area and the residents were complaining. So, the administrative district office ordered the company to install a waste gas purification unit.
- For a small business, employing no more than twelve workers, the investment was a major one.
- Styrene is not abatable with aqueos scrubbers,
- nor is it suitable for regenerative adsorption filters, due to its tendency to polymerize.
- The VOC concentration was well below the autothermal range of even the most sophisticated regerenative thermal oxidations available.
- The administrative district office was not willing to accept a classic, open biofiltration unit due to its poor efficacy with styrene.
- And catalytic combustions are less than ideal for one-shift operations.
So, what’s to do?
The Customer Wanted…
- to spend as little money as possible;
- to get a waste gas purification that would serve them for the next decade at least – accepted by the administration;
- nothing too complicated, nothing requiring an chemical engineer to run it properly;
- nothing water-based – there was only the communal water treatment facility where contaminated water could go to
- and to know exactly what would be coming, both financially, regulatory and technically.
The Customer did not want…
- to invest in a waste gas purification unit that would be obsolete within a few years;
- to have a sensitive operation running which would cause frequent incidents;
- to go bankrupt.
What We Did
- Based on prior experience, we assesed the efficacy of available waste gas purification techniques and selected those that were at all suited. Some, like the aqueous scrub, dropped out at this stage.
- We then compiled costs with the help of manufacturer’s proposals:
- Upfront costs,
- capital costs,
- running costs,
- man hours (important in a business that is not luxuriously staffed), probable gains like waste heat, and so on.
- This was broken down for several scenarios: One shift or two shift operation, an increase or decrease in emissions. The resulting figure the customer wanted was the cost per cubic meter of waste air treated. At this stage, techniques that were inefficient for this type of operation, like non-regenrative or recuperative combustion, dropped out.
- The next step was a risk analysis. What could go wrong with the individual technology, how probable was the occurrence, what kind of disruption would it cause, how long would down time be and and how much would restarting the operation cost? For example,
- the composition of microbial strains in a biofilter can switch, causing the filter to either block up, or diminish its function.
- With UV-based technologies, lamps can burn out, become tarnished or lose their radiation intensity.
- As a last step, we aided the customer in obtaining approval from the administrative district office. Their comment and input was essential in making the decision which of the remaining three technologies – in this case, activated carbon, UV degradation and biofiltration – to choose.