EQUIPMENT - 15-INCH AND 24-INCH-DIAMETER FLUID BED
Hazen has both 15-inch-diameter and 24-inch-diameter pilot-scale fluidized-bed systems available for process demonstration. Testing in these units normally is performed to verify information previously developed at the bench-scale level and to develop design sizing information for commercial application. The primary distinctions between these two systems is that the 24-inch unit is capable of testing larger quantities of material than the 15-inch unit. Consequently, more confidence can be placed in design data developed from the 24-inch unit, while the 15-inch unit is more suitable for pilot testing when there are limited quantities of material available. The equipment specifications shown below summarize dimensions and capacities for each test unit and provide a schematic of either pilot plant system.
Both pilot plant furnaces are refractory-lined with high-temperature castable, backed by insulating castable to minimize heat loss. Each system is equipped to measure temperatures and pressures in the preheater, in the fluid bed, and in the process exhaust stream. Appropriate meters are used to measure and control the flow of air, fuel, cooling water, etc., used during testing.
Hazen's fluidized-bed demonstration systems, available for use with unusually short setup times and fully configurable for varying process parameters, make us uniquely capable of providing state-of-the-art data for commercial plant scaleup.
Both fluidized-bed furnaces are directly heated by a propane-fired windbox. Primary fluidization gas is supplied to the windbox, then passes to the bed through a distribution plate equipped with T-bar tuyeres. Hot process gases with entrained particles leaving the fluidized bed pass into an expanded freeboard section where the coarser particles disengage and return to the fluid bed. Finer particles pass through the freeboard and enter a cyclone where over 90% of the particles larger than ten microns are disengaged and collected. A baghouse is available for installation downstream of the cyclone, if required. Gases leaving the cyclone and baghouse are scrubbed in a closed-circuit, venturi scrubber system to capture the remaining solid particles. A second stage of scrubbing, using a packed tower scrubber, further cleans the process gases. The clean gases are conveyed from the system by means of an induced-draft fan which also serves to balance the pressures in the system.
Test programs in either pilot-plant system can utilize solid, liquid, gaseous, or slurry feeds introduced into or on top of the fluidized bed. Solid product from the fluid bed can be withdrawn from the system continuously or batchwise, as required. Cyclone and baghouse solids are collected on a continuous basis.
The pilot-plant fluidized-bed systems are equipped with online instrumentation to obtain process data. Process temperatures, pressures, and gas compositions, including O2, CO2, CO, SO2, NOx, and total hydrocarbons (THC), are monitored and recorded continuously. A gas chromatograph and mass spectrometer are available for measuring other gaseous constituents, such as water, hydrogen, nitrogen, and methane. Differential pressure is measured between the bed and freeboard to monitor and control the fluidization characteristics of the bed medium. A data-acquisition system is used to monitor and record selected process data. Emission sampling for organic compounds, metals, and other inorganic species can be performed as required, using EPA-approved methods.
| Pilot Plant Operating Information | ||
| 15-inch Unit | 24-inch Unit | |
| Maximum operating temperature, ºC | 1,000 (1,850ºF) | 1,000 (1,850ºF) |
| Typical bed weight, lb | 200–300 | 600–1,000 |
| Linear space velocity range, ft/s | 1–8 | 1–6 |
| Bed section height, ft | 5 | 7 |
| Expanded freeboard section height, ft | 3 | 6 |
| Freeboard section diameter, ft | 2 | 3 |
| Heating capability, Btu/hr | 300,000 | 750,000 |
| Water evaporation rate, lb/hr | 80 | 220 |
| Typical material processing rates, lb/hr | 50–200 | 200–1,000 |
