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Show The combustor failed to melt the material as required in the production situation, even while firing at its maximum capacity of 800,000 BTU/hr (for this configuration). It is concluded that the presence of the numerous material rods adjacent to the outlet of the combustor had an adverse effect on the operation of the combustor, probably by affecting the returning pressure wave. (The lab tests had involved only one or two rods at a time.) During the lab testing this pressure wave was also observed to lower the exhaust temperature as the gas input was increased, and the combustion cycle became stronger. This also may have had an negative effect in the field trial. The conclusion of these tests was that more development was required to take into account the effects of the pressure waves. Novadyne is conducting further developments. Figure 4 gives a typical relationship between the combustion chamber pressure and capacity for the lab tests. The chamber pressure is approximately linear with the firing capacity, all other things being equal. Application to Industrial Drying Novadyne has been developing a pulse combustion dryer to compete with flash dryers and rotary drum dryers. The design of the dryer has evolved to meet a number of objectives. These include: Reduce the capital cost of a pulse combustion dryer in order to compete with other technologies. Design the dryer to be single pass to eliminate expensive back-mixing equipment with high power demands. Adopt a design with a small footprint to minimize required floor space. Show efficiencies equal to or better than competing technologies, ie. 1300 to 1500 BTU/lb water evaporated. Pilot Plant Description The pulse drying system consists of an inlet air blower, a 1,000,000 BTU/hr pulse combustor, material hopper, agitator and feed mechanism, a drying chamber, exhaust blower, and exhaust cyclone. The plant is fully instrumented and has a fail-safe control system. Aside from the pulse combustor itself, the mechanical components of the dryer are conventional. Components with moving parts are the inlet and outlet blowers, plus the inlet screw auger, outlet airlock on the cyclone, and the combustor's flapper valves. This makes for a relatively low maintenance system. 6 |
