Combustion tests, staged

Hay DJ, Finkelstein A, Klicius R. 1986. The national incinerator testing and evaluation program two-stage incinerator combustion tests. Chemosphere 15 9-12. 

During the initial stages of a fire, fire-retardant-treated wood contributes less heat than does untreated wood, especially from the flammable volatiles (8,26). This means that the spread of fire to nearby combustibles is slow. The fire tends to be confined to the primary source. In the ASTM E84 test for building materials, treated specimens produce about 75 percent less heat than untreated red oak. In a total combustion test, however, such as the National Bureau of Standards potential heat method (54), both treated and untreated wood release about the same total heat. 

It should be noted that the combustion tests were conducted with only primary air supply. Attempts were made to keep the feed rate and excess air as similar as possible between trial burns, however, the operation conditions were very hard to keep fixed, as the excess air was controlled manually and these biomass fuels do not have good flow characteristics due to their inconstant particle shape, uneven particle size distribution and high moisture content. Many studies related to incomplete combustion have focused on processes with two-stage air supply and have identified that excess air is a key factor influencing the formation of CO and CH (2, 4, 5. 13). It has also been shown that each wood furnace has a typical correlation between the CO-emissions and the excess air ratio regardless of fuel type (13). 

Similar behavior was observed for LNG clouds during both continuous and instantaneous tests, but average flame speeds were lower the maximum speed observed in any of the tests was 10 m/s. Following premixed combustion, the flame burned through the fuel-rich portion of the cloud. This stage of combustion was more evident for continuous spills, where the rate of flame propagation, particularly for LNG spills, was very low. In one of the continuous LNG tests, a wind speed of only 4.5 m/s was sufficient to hold the flame stationary at a point some 65 m from the spill point for almost 1 minute the spill rate was then reduced. 

So far, only the non-combustibility (ISO 1182) and the ignitability (ISO 5657) tests are available as international standards. For the other parameters, the test methods are still at a development stage. A solution to the 1992 objective is not yet possible, even if the necessary tests can be finalised prior to that date, because many practical difficulties still remain to be solved. 

Work in the first phase involved preliminary checking of equipment and instruments for measuring emissions, as well as establishment of N0X reduction trends using staged combustion techniques, while burning the current power plant fuel, a low-sulfur No. 6 fuel oil. The purpose of this phase was to reduce the time necessary to carry out the subsequent SRC-II tests and to achieve minimum NO levels with the limited supply (4,500 bbls) of SRC-II fuel oil. X... 

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