Thermo Structural Analysis of Biomass Combustion Steam Generation Heat Exchangers Using Three Dimensional Numerical Modelling

Biomass with all its positive characteristics contains some elements and compounds that react negatively with stainless which are known for its usage in high temperature, corrosive prone and, hash environment. Therefore, it is pertinent to comparatively study the strength of various corrosive resistance metals to be able to have an alternative to stainless steel.  The purpose of this study is to model and simulate a three-dimensional steam generating boiler plant heat exchanger for a biomass firing process. In the study, inlet temperature and operating temperature of shell and tube sides are taken as input parameters with a square pitch bundle arrangement. The heat transfer analysis is done by considering hot flue gas inside the tubes and steam on shell side to determine the thermal stress, strain and deformation distributions in the tubes and shell of the heat exchanger. The study also presented time-history analysis of the both shell and tubes to ascertain the material reactions within the specified time range. The comparison of deformations and the equivalent strain rate between the two designs indicated an excellent performance of the AL6XN over the 306L stainless steel. The strain amplitude for PMX110 and WKX110 sequentially dropped from 903 to 496 and 621 to 332 between the temperature range of 100 – 10000C respectively. The maximal equivalent strain values for the shells and tubes were 2.238e-003 and 1.294e-004 for PMX110 and 1.490e-003 and 3.212e-004 for WKX110 respectively. The highest deformation in both PMX110 and WKX110 were estimated as 6.729e-004 and 6.131e-004 for the shells and 1.441e-004 and 1.328e-004 for tubes respectively.