A one-dimensional reactor model was developed to simulate the performance of an entrained flow gasifier under various operating conditions. The model combined the plug flow reactor (PFR) model with the well-stirred reactor (WSR) model. Reaction kinetics was considered together with gas diffusion for the solid-phase reactions in the PFR model, while equilibrium was considered for the gas-phase reactions in the WSR model. The differential and algebraic equations of mass balance and energy balance were solved by a robust ODE solver, i.e., an semi-implicit Runge-Kutta method, and by a nonlinear algebraic solver, respectively. The computed gasifier performance was validated against experimental data from the literature. The difference in product gas concentration from the equilibrium model, and the underlying mechanisms were discussed further. The optimal condition was found after parameter studies were made for various operating conditions.

As a treatment method of sewage sludge, the hydrothermal carbonization (HTC) process was adopted in this work. HTC has a great advantage considering the economic efficiency of its process operation due to its reduced energy consumption and production of solid fuel upgraded through the increased fixed carbon and heating value. The ash of sewage sludge, however, contains up to 52.55% phosphate, which degrades the efficiency of the thermochemical conversion process such as pyrolysis, combustion, and gasification by causing slagging. In this study, three kinds of organic acids, i.e., oxalic, tartaric, and citric acid, were selected to eliminate phosphorus from hydrochars produced through the HTC of sewage sludge. The efficiency of the phosphorus removal and the properties of the corresponding HTC hydrochars were analyzed by adding 20 mmoles of organic acids per 1 g of phosphorus in the HTC sample. In addition, the phosphorus reduction effect and the applicability to an upgrading process were verified. Oxalic acid was selected as the most appropriate organic acid considering the economic efficiency of its process operation. Furthermore, the optimal conditions were selected by analyzing the efficiency of the phosphorus elimination and the characteristic property of the HTC hydrochars with the weight fraction of oxalic acid.

The turbo-pump and turbine are driven by liquid fuel fed into a gas generator, where the fuel is oxidized with a liquid oxidizing agent. For stable operation of the turbine, the combustion temperature of the gas generator must be maintained below 1000 K. The thermodynamic characteristics of kerosene oxidation in the gas generator must be understood to optimize the design and operation conditions of the liquid-fueled rocket engine system. Herein, the 3-species surrogate mixture model for kerosene was selected, and the detailed Dagaut's kerosene oxidation mechanism consisting of 225 chemical species and 1800 reversible chemical reactions was utilized. The exit gas temperature and product gas composition in the gas generator under fuel-rich conditions were simulated by applying the perfectly stirred reactor model. The perfectly stirred reactor model was used in combination with the liquid spray model for evaporation of the droplets and the two-temperature model for evaluation of the flame temperature separately from the locally averaged reactor temperature. The theoretical prediction of the gas species fraction and soot yield could be improved by applying the tar cracking mechanism, where the reaction characteristics under high temperature were taken into account.

Coastal debris has recently emerged as a serious environmental pollution problem. Coastal debris can be treated using pyrolysis because it consists mainly of combustible materials like plastics (e.g., polyethylene (PE), polypropylene (PP), nylon) and wood. In this study, the pyrolysis characteristics of coastal debris were fully utilized by applying their basic data to fuel production. The initial temperature increased from 330 °C to 380 °C for the nylon fishing net coastal debris sample, from 405.01 °C to 430.08 °C for the PE fishing net coastal debris sample, from 395.01 °C to 419.96 °C for the PP rope coastal debris sample, and from 114.95 °C to 115.02 °C for the wood (bamboo) coastal debris sample. The activation rate of the global activation energy and the pre-exponential factors rose with the increasing heating rate, complementing the reduction rate constant due to the larger growth of the exponential term due to the kinetic models used.

The amount of cattle manure generated accounts for over 40% of the livestock manure in South Korea. Most livestock manure is utilized as a fertilizer and a soil amendment. However, the soil nutrients have exceeded saturation in South Korea. Accordingly, cattle manure, including lignocellulosic biomass, was applied for solid fuel production in this study. The three different types of carbonization process, namely, hydrothermal carbonization, torrefaction, and carbonization (slow pyrolysis), were estimated for a comparison of the hydrochar, torrefied char, and biochar characteristics derived from cattle manure. The processes were performed at temperatures ranging from 190 to 450 °C. The evaluation of the hydrochar, torrefied char, and biochar produced by three processes was conducted by the proximate, ultimate, calorific value, fuel ratio, and energy yield, which were used for the analysis of fuel quality. Additionally, the ash properties, including silicon dioxide, chlorine, and base-to-acid ratio (B/A) on hydrochar, torrefied char, and biochar were investigated to predict ash deposition during combustion. These analyses are essential to stabilize the operation of the combustion chamber. The thermogravimetric analysis represented the upgraded quality of hydrochar, torrefied char, and biochar by three different carbonization processes.