Intensified separation processes
15 Jan 2000
The last paper presented at the three-day Antwerp conference was perhaps the perfect way to round off a meeting that was a mixture of the past, present and future possibilities for process intensification.
As its author A Meili of the Swiss process engineering company Sulzer Chemtech says, process intensification is not just theory. And here was a prime example of its practical application in the shape of the anthraquinone process to produce crude hydrogen peroxide, and then purify and concentrate it for on-site use such as the pulp and paper and textile industries.
Illustrated (right) is a conventional distillation plant for H2O2. Typically it comprises a steam-heated evaporator (1), separator (2), tray column (3), water-cooled shell-and-tube condenser (4), vacuum pump (5) and all connecting piping. Now compare this with Sulzer's patented design (far right). The separate reboiler is now an integrated climbing film evaporator (a); the column contains a lamella-type separator (b); structured packing (c) replaces trays; and a direct condenser (d) which allows a temperature difference of only 2 to 3degC between vapour and cooling water is mounted on top of the column, with the vacuum pump (e) being connected to the condenser. For added safety, there is a flooding tank (f) on top.
The result is a separation process with much lower product hold-up, increased safety because of lower operating temperature, and a high product yield in fact, all the characteristics of a successful application of process intensification methods to process and plant design.
