Determination of sand mass flow rate in a test reactor

Plastic has become a necessity and a permanent part of modern society. Plastic production continues to increase annually, but current recycling rates cannot keep up with the growing amount. Landfills and plastic waste hotspots keep accumulating waste, causing adverse impacts on ecosystems, economies and to human health. Plastic pyrolysis technology has gained the attention of researchers as a viable solution to address the virgin material shortage and the plastic waste recycling problem. The purpose of the thesis was to determine the bed material mass flow rate in a fluidized bed test reactor that will be later used for plastic pyrolysis. The objective was to calculate the mass flow rate which can be later used to determine mass and energy balances and applied to scale up the process to a larger model. The research method used was a combination of experimental, qualitative, and quantitative approaches. A test matrix was created to ensure that all research questions were addressed. Methods for measuring the sand mass flow rate were evaluated. A total of seven tests were conducted in a test setup built in four shipping containers, and the bed material mass flow rate was examined in both open and closed systems, using hot and cold sand. The sand mass flow rate was successfully measured using a scale, and it was found that pressure drop rate test was too complex and inaccurate. The maximum cold sand mass flow rate of 0,38 kg/s (SEM of ± 5,97 %) was reached when sand circulation valve, L-valve, aeration was 7 l/min and maximum hot sand mass flow rate of 0,45 kg/s (SEM 9,44 %) was reached when L-valve aeration was 4 l/min. When using hot sand, mass flow rate increased by 0,07 kg/s and the L-valve aeration dropped by 3 l/min. In the cold tests, the reactor maximum capacity of 5,5 l/min was reached at a reactor bottom pressure of 9,3 kPa, and in the hot tests, the reactor maximum capacity of 1,5 l/min was reached at reactor bottom pressure of 5,5 kPa. In the future, sand mass flow rate limitations should be investigated further, and a larger research question would be finding the optimal plastic pyrolysis process parameters for different feedstocks.