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MINIPILOT SOLAR SYSTEM: DESIGN/OPERATION OF SYSTEM AND RESULTS OF NON-SOLAR TESTING AT MRI
Citation:
Gorman, P., E. Ball, AND et al. MINIPILOT SOLAR SYSTEM: DESIGN/OPERATION OF SYSTEM AND RESULTS OF NON-SOLAR TESTING AT MRI. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-94/027 (NTIS PB94-152238), 1993.
Description:
Prior to this project, MRI had carried out work for the Environmental Protection Agency (EPA) on the conceptual design of a solar system for solid waste disposal and a follow-on project to study the feasibility of bench-scale testing of desorption of organics from soil with destruction in a solar furnace. The feasibility study involved a two-step process: (1) thermal desorption of organics from soil (non-solar) with recovery of the organics in liquid form and (2) destruction of the organics in a solar furnace. Previous laboratory work by the National Renewable Energy Laboratory (NREL) and others indicated efficient destruction of organics by solar input at high temperatures, but the experiments were limited to low concentrations of organic vapors in air. The feasibility study conducted by MRI recommended the important difference that the organics should be fed to the solar furnace in liquid form, to provide destruction through combustion and solar photolytic effects. Based on the feasibility study, EPA directed MRI to proceed with design, construction, and testing of a Minipilot Solar Reactor System with liquid organic feed. Testing of the system on this project was intended to be carried out in two parts. The first part was to be non-solar testing at MRI using a synthetically prepared liquid organic mixture. The primary purpose of the non-solar testing at MRI was to utilize EPA sampling and analysis methods and determine if the organic emissions quantitated by those methods would enable quantitation of the expected significantly lower emissions when operating with solar input. A secondary purpose of the testing at MRI was to conduct tests with a UV lamp to determine if this provided any significant reduction in emissions. The second part of the project was to carry out subsequent testing with solar input at NREL. MRI proceeded with design and construction of the Minipilot System, and included complete instrumentation with computerized data logging, flame detectors, automatic shutdowns, and continuous monitors for CO, O2, and THC. NREL staff contributed valuable advice that aided in the development of the design. Extensive operational tests were conducted and resulted in some system design and operational changes that improved the system's overall utility. Operational techniques were established for this system during the initial operating tests. The operational performance of the Minipilot System was demonstrated during a series of 10 tests using the EPA-approved sampling and analysis methods. This report summarizes the results of those tests, as well as the design and construction work mentioned above. Results of the 10 tests showed that it should be possible to determine if there is a significant reduction in emissions (> 3X) when operating with solar input. Such reduction in the emissions should be determinable for two of the POHCs contained in the synthetic feed liquid (CCI4 and DCB), for both the volatile and semivoiatile PICs, and for dioxins and furans. But reductions are probably not determinable for the other two POHCs (toluene and naphthalene). Results also showed that a three-fold reduction in volatile PICs occurred in both single-chamber tests when an artificial UV light was utilized. The Minipilot System is now fully operational and has been designed to utilize the full solar capability of the NREL facility (10 kW) with temperature control via different aperture openings (to vary the radiation heat losses) and/or water injection. It has already been operated in the non-solar mode over a temperature range of 1400° to 2000°F. Further, the baseline levels of the organic emissions have already been determined using EPA sampling and analysis methods for two different operating modes (single- and dual-chamber) and two different flow rates. Thus the system is ready for the next phase: solar testing at NREL. Carrying out the tests as planned at NREL is crucial to the overall goal of the project: to determine if solar input provides a significant reduction in organic emissions as compared to emissions in the non-solar mode at the same operating conditions (i.e., temperature and feed rates, etc.). Moreover, the tests at NREL are intended to provide data on the effect of certain parameters that are very important to the design of larger pilot- or full-scale systems. Specifically, tests at NREL would: (1) investigate effects of solar exposure time (over the range of 4 to 8 s), which is critical to sizing of reactors; and (2) investigate operation at different solar flux levels, up to 10 kW, to determine the optimum kilowatt input per unit of gas flow rate (scfm), which is critical to sizing the costly solar collector/concentrator units. Considering the important goals of the solar tests at NREL, and results of the non-solar tests that have already been completed at MRI, it is recommended that work proceed on transporting the Minipilot system to NREL and testing it with solar input.