Browsing by Author "Martiskainen, Miika"

Now showing 1 - 1 of 1

Investigating the effects of process conditions on the capturing capacity of guard materials
(2020-10-20) Martiskainen, Miika
Kemian tekniikan korkeakoulu | Master's thesis
The utilization of a guard bed can potentially mitigate fouling and poisoning of the catalysts by removing the impurities from the process stream before the catalyst. The purpose of this Master’s thesis was to be a pre-study for the removal of impurities by utilizing the guard bed technology. This work investigated the effect of temperature, pressure and space velocity on the impurity removal. Based on the evaluation of the experiments a test run procedure for future studies is proposed. This thesis focused mainly on the removal of two impurities (phosphorus and silicon) using gamma alumina as the guard material. The investigation of the topic was undertaken by performing test runs with bench scale tube reactors packed with the guard material. The two feeds were used in the test runs. One had phosphorus and the other one had silicon as the primary impurity. The test runs consisted of a reference run and three conditions change runs where one process condition was altered in each. The liquid products were analysed primarily using ICP-MS and the guard materials were characterized mainly with XRF. Test runs with the phosphorus rich feed showed that the phosphorus removal occurs mainly by formation of salts and subsequent collection in the reactor bed. The results showed that the temperature had the most influence on the phosphorus removal. Lower temperature decreased the removal and higher space time increased it. In the test runs using the silicon rich feed the removal of silicon seemed to occur mostly by decomposition of silicon compounds to volatile compounds. From the results it was difficult to distinguish the effects of condition changes due to the leaching of metals and silicon from the reactor bed or the equipment by the feed. A temperature decrease seemed to increase silicon removal by decreasing the leaching. A lower feed rate possibly favoured the removal of silicon via adsorption than the evaporation. Pressure had no major effect on the phosphorus and silicon removal. The temperature could be increased in further test runs with phosphorus rich feed while the other conditions could be kept the same as in the reference test run. gamma alumina occurred not to be a suitable guard material for the silicon rich feed due to its leaching by the feed. Without feed pretreatment, the process conditions which mitigate the leaching should be used meaning lower temperature and the space time should not be increased. For future test runs with both feeds the reactor packing should be improved. The guard beds should also be prewashed before test runs to mitigate leaching from the fixed bed.