Abstract

The goal of this thesis was to understand what parameters would be most impactful when delivering dry, pulverized coal in a dilute-phase, with a high-pressure feed-system to a pressurized oxy-combustion (POC) reactor. Many studies have conveyed materials in dense-phase plugs at high-pressure or in dilute-phase flows at atmospheric pressure. Very few studies have fluidized and conveyed materials in dilute-phase flows at high pressure, as we needed to. Additionally, studies which might have been applicable based upon system -pressure and -phase delivered findings that were empirically based and therefore not specifically applicable to non-similar systems. 220 different tests were ran using a bench-scale apparatus consisting of a hopper, connecting conveying pipes, and a filter point (representing the future reactor). The system was pressurized to 300 psi using CO2. Dry, pulverized coal with an average diameter of 50 microns and a bulk density of 800.9 kg/m3 was fluidized and conveyed with different combinations of fluidization inlet and fluidization outlet flowrates. Each specific flowrate combination was tested 3 to 5 times. The resulting coal flowrates were recorded and analyzed to see which flowrate combination delivered 13.6 kgs coal/hr and had the least variability between tests. The fluidization inlet and outlet flowrates, coal moisture content, and system geometry were key parameters. In a 2-inch diameter hopper the fluidization inlet flowrate should be kept at 0.119 m/s or below to keep the fluidization regime within the hopper below the transition point to the bubbling fluidization regime. This was beneficial since less CO2 was needed by the system and smaller perturbations within the bed didn't disrupt flow leaving the hopper. The fluidization outlet flowrate could still advance the fluidization regime within the hopper even if the fluidization inlet flowrate is kept at 0.119 m/s. For a ¼ inch diameter the outlet should be kept at 0.005 m/s or above. Additionally, the standard deviation in the measured coal flowrate decreased dramatically when flow of gas was allowed to exit through the top of the coal column (fluidization outlet). The standard deviation was 8.2 kg/hr with the fluidization outlet closed and 3.5 kg/hr with the fluidization outlet flowing to provide 0.005 m/s in the bed above the coal outlet. Coal should have a moisture content between 3% and 6% to ensure that electrostatic interactions between coal particles is kept to a minimum. Finally, these results were found for specific hopper and fluidization inlet and outlet diameters. If these diameters are changed then some calculation must be done for these results to be applicable to systems that are not like the one described later in this thesis.

Degree

MS

College and Department

Ira A. Fulton College of Engineering and Technology; Chemical Engineering

Rights

http://lib.byu.edu/about/copyright/

Date Submitted

2019-07-01

Document Type

Thesis

Handle

http://hdl.lib.byu.edu/1877/etd10945

Keywords

fluidized bed, dilute-phase, high pressure, oxy-combustion

Language

english

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