Review of 30 Years of Research Using the Chemical Percolation Devolatilization Model

The chemical percolation devolatilization (CPD) model for coal pyrolysis was first published in 1989, and a completed version that included the vapor-liquid equilibrium model and cross-linking model was published in 1992. The CPD model was one of three pyrolysis models developed using a lattice model to account for the chemical structure of the coal and was directly based on solid-state C-13 nuclear magnetic resonance (NMR) measurements of the coal structure. A correlation of coal structure parameters measured by NMR spectroscopy was performed to permit use of the CPD model to determine pyrolysis rates and yields of tars and light gases for any coal type. A separate nitrogen release model was also developed on the basis of the chemical structure. In the past 30 years, the CPD model or the concepts in the CPD model have been used to describe pyrolysis in many situations for many fuels. The CPD model has been incorporated directly into simulations of large coal combustors as well as detailed simulations of single-pyrolyzing or burning coal particles, which was the original intent. Some investigators added a more rigorous treatment of light gas release. Other investigators have used the CPD model to determine rate coefficients for simpler models for a given range of heating conditions. In addition, the concepts in the CPD model have been used to develop models for other solid fuels, including biomass, black liquor, oil shale, rigid foams, propellants, heavy oil, asphalt, and scrap tires. The CPD model has also been extended to low heating rates for underground coal thermal treatment and hydropyrolysis. This paper is a review of the development, improvement, and uses of the CPD model, along with extended uses of the concepts in the CPD model.