In the last few decades, in the chemical industry and wider, there has been an ever greater demand for ever more effective separation processes, with which we produce cleaner intermediate and end products. This is the result of economic efforts to increase production output and to lower production costs, which are needed to accommodate the rising demands of the market, as well as environmental efforts to reduce or even eradicate waste products, which are created during production and for which we, as of now, don’t have any secondary use or the option of recycling, due to which these waste products, in some form or another, end up in the environment, thereby affecting it’s purity and balance.
One company, which makes these efforts, is Belinka Perkemija d.o.o. Among other things, they produce hydrogen peroxide via the anthraquinone process, where the end product is acquired in the form of an aqueous solution with a high concentration of organic solvents, which then have to be removed. This is achieved by different separation processes, such as: extraction, distillation and membrane filtration. In this thesis we focus on membrane filtration, for which, at the moment, polyamide membranes are used. These membranes are relatively cheap and effective in removing organic solvents, but are quite short-lived, which is why they’re inconvenient for continuous operating conditions. This is why we conducted a pilot research with ceramic and composite polyamide-polypropylene membranes of different permeabilities, in hopes of finding a potential long-lived alternative. Due to better chemical, thermal and mechanical properties, especially of ceramic and less so of polymeric membranes, a longer membrane lifespan was expected, while also maintaining a satisfactory removal of organic compounds, in spite of higher permeabilities of the tested membranes.
It was discovered, that both ceramic membranes, which were used, were almost completely ineffective in removing organic compounds in the crude form of hydrogen peroxide. This is the result of the permeabilities of these membranes, the pores of which were evidently too high, in comparison to the size of the organic molecules, to separate them from the rest of the mixture. As a result of such low rejection rates, it was decided, that the durability of these membranes wouldn’t be determined, as it was deemed to be not relevant and quite impossible. On the other hand, the composite polymeric membrane, which had a much lower permeability, was very effective in removing these organic compounds, but as a result of the filtration device malfunctioning, which led to the destruction of the membrane, the experiments had to be cut short and consequently it was not possible to determine it’s durability. In the end the composite polyamide-polypropylene membrane was selected for further testing, on the basis of the experimental evidence, which we had been able to gather. Future experiments will give us the answers to the questions, which have been left open in this thesis, as well as determine whether optimization of the industrial process with these membranes is possible and reasonable.
|
