EPA CHALLENGES FOR BAGASSE FIRED POWER STATIONS

By
M.B. INKSON, B.J. MISPLON and E. de VILLIERS 
Thermal Energy Systems
mike.i@sucrose.com

KEYWORDS: Cogeneration,
Environmental Impact, Emissions.

Abstract 

TRADITIONALLY, the sugar industry has been treated leniently with respect to emissions
standards but, as it focuses more on electricity as a profitable by-product, that is changing
even though bagasse is a renewable fuel.
Nowhere is that more the case than at US Sugar’s Clewiston factory in Florida: even
though it is not a major exporter of electricity, when it installed a new boiler, the factory was
obliged to conform with stringent EPA standards.
The challenges imposed by the standards are discussed together with the engineering
solutions and the results obtained.
The outline specification was for a 500 000 lbs/h [~226 800 kg/h] boiler delivering
600 psig, 750ºF [~4137 kPa, ~399°C] steam when firing bagasse.
The main challenges were seen in obtaining the 0.026 lbs/MMBTU [~24 mg/Nm³]
PM10limit and the original 0.12 lbs/MMBTU [~70 ppmvd] NOXlimit without exceeding the
0.38 lbs/MMBTU [~363 ppmvd] CO limit or the 20 ppmvd ammonia slip limit.
Continuous monitoring was required. Engineering was supported by fluid dynamic
studies, in particular with respect to the NOxand CO profiles in the furnace: i) maximum NOx
reduction was required from the urea injection system so location was critical; and ii)
engineering down combustion NOxincreases CO.
In the event, the unit comfortably passed all tests. The variable OFA nozzles which
had been installed proved particularly usefulin tuning the boiler and the low uncontrolled
NOxlevels [meaning there will be reduced urea charges] were pleasing to see.
While these stringent requirements are unlikely to be applied to other bagasse boilers
in the short term, the lessons learned will makeit possible to rise to those challenges when
they arise.

Co-Products Proc. Int. Soc. Sugar Cane Technol., Vol. 27, 2010