Leaching as a pretreatment process to complement torrefaction in improving co-firing characteristics of Jatropha curcas seed cake

The presence of certain inorganic elements in biomass causes issues such as slagging, fouling and corrosion when co-firing with coal for power generation. In this work, the efficacy of leaching to remove these elements from Jatropha curcas seed cake was investigated. Leaching of both untorrefied and torrefied seed cakes was carried out in Milli-Q water at temperatures of 20, 35 and 50 °C. At 20 °C, the two critical elements, potassium and chlorine, decreased by as much as 85 and 97 %, respectively. Leaching at higher temperatures was only beneficial for the more intensely torrefied biomass, since they were more resistant to leaching. The electrical conductivity and ion content of the leachates were measured, as were the inorganic elemental content, dry ash content, volatile matter content and higher heating value (HHV) of the solid seed cake. A secondary benefit of the leaching was an increase in the HHV by up to 10 %

Influence of Coal Composition and Operating Conditions on the Release of Alkali Species During Combustion of Hard Coal

In solid fuel conversion systems, the release of alkali species can cause severe problems such as fouling, slagging, corrosion, and erosion. Especially in future coal-fired combined cycle processes such as pressurized pulverized coal combustion (PPCC), alkali species can cause corrosion of the gas turbine blading. In order to solve these problems, detailed information about the alkali release is required. In this work, the influence of coal composition and operating conditions on the release of alkali species is investigated. For this reason, laboratory combustion experiments with six different hard coals were conducted at temperatures of 800 and 1200 degrees C and absolute pressures of 1, 3, and 9 bar. High pressure mass spectrometry (HPMS) was used for online analysis of combustion products such as HCl, NaCl, KCl, SO2, and Na2SO4. In addition, two of the coals were subjected to a leaching procedure. Themodynamic equilibrium calculations with the software package FactSage 5.4 and the FACT database were conducted for comparison with the experimental findings