The Problem
A chemical company in Southern Louisiana, which manufactures 100,000 tons per day of herbicide, was faced with a potentially costly dilemma. They needed to expand their plant output by 30%, but their Cl2 stripper was already at maximum capacity. At a Cl2stripper capacity of 50 gpm, they needed at least 75 gpm (a 50% increase), which meant they would not only need to find a packing that had a substantially lower pressure drop to allow for the increased flow, but it would also have to have an increased transfer efficiency to be able to meet effluent specifications at the higher flow rate.In addition to the capacity issue, the stripper, having a diameter of 18″ and packing height of 28.5 ft, performs the function of stripping elemental chlorine (Cl2) from hydrochloric acid (HCl). The Cl2 in the process was reducing packing service life to only 2 years, which was forcing frequent costly shutdowns. Not only did they need better hydraulic and transfer performance, they needed the packing to be made out of an affordably priced material that could resist attack from chlorine.
Why #2 NUPAC® was Used
The alternatives were to purchase a new stripper at a cost of $150,000 or to retrofit the existing equipment with #2 NUPAC which would cost much less and promised the desired increase in capacity and a big boost in efficiency. NUPAC also could be made out of polyethylene material that can yield better life in a Cl2 environment.
Meeting the Requirements
In February (1999) the 28.5 ft bed of 2″ plastic Pall rings was replaced with polyethylene #2 NUPAC. The results were astonishing. The pressure drop was reduced from 15″-H2O to 9″-H2O with an increase in capacity of 70%. This was 20% higher than needed!
The efficiency also increased; so much so that even at the higher throughput the efficiency was still 10 % higher than before.
In their words, “we now operate with flows up to 85 gpm. This will allow us much more flexibility and the possibility of saving costs by shutting down the other stripper. The new packing does all LANTEC said it would for performance.”
