ASME PTC 34 is a test procedure for determining the thermal capacity and thermal efficiency of systems (typically boilers) combusting waste fuels (typically Municipal Solid Waste - MSW) and for determining the higher heating value (HHV) of those waste fuels. The basis of the procedure is more commonly known as the “boiler-as-a-calorimeter” method. The need for PTC 34 arose from the difficulties in obtaining representative samples and accurate fuel analyses using traditional laboratory methods such as a “bomb calorimeter”. Unsuccessful attempts were made to come up with a larger “bomb calorimeter”, so a committee was formed to create PTC 34 which was published in 2007.
ASME PTC 34 is firmly based on the widely accepted boiler test code, ASME PTC 4 – “Fired Steam Generators”, but has several different challenges in having to measure the relatively difficult parameters of flue gas flow and moisture and fuel and ash quantities. As a result, the uncertainty of PTC 34 is higher. However, the philosophy of correcting results to standard, contract or reference fuel analysis is the same in PTC 4 and PTC 34. So, an industry approved Code for acceptance testing is available to the Energy-from-Waste industry.
ASME PTC 34 can be used in several ways depending on the analysis time period. It can be used for typical short-term, i.e. 8-hour, performance or acceptance tests, again with the ability to correct to reference fuel analyses. Alternatively, multiple “samples” of fuel HHV can be obtained using PTC 34. With the test data and HHV results, accurate correlations can then be generated to be able to make adjustments for varying fuel conditions in longer term, i.e. 7-day, throughput capacity testing. The 8-hour HHV determinations can also be used to validate or even calibrate correlations used over the life of a waste combustor as operating parameters stray from their normal ranges. Taken to the extreme, PTC 34 can be used as a basis for near-real-time monitoring of fuel quality or possibly combustion control. Recent developments of laser-based flue gas moisture instruments and the economizer heat balance method for determining flue gas flow make this leap possible.
The goals of this paper are to make the industry more aware of ASME PTC 34 and the guidance it contains on making the difficult measurements, to promote its use as a standard in the industry and to instill confidence in the time-tested and accepted process of making corrections to test results for off-design fuel characteristics.