(9b) Development of a Hydrogasification Process for Co-Production of Substitute Natural Gas (Sng), Biofuel and Electric from Western Coal

Arizona Public Service (APS) Hydrogasification Project (AHP Project) goal is to develop and demonstrate an engineering-scale coal hydrogasification-based process for co-production of Substitute Natural Gas (SNG), Biofuel and electricity with near-zero emissions from Western coals with carbon recycling. The phase I of the project focuses on process alternatives selection, hydrogasification reactor configuration, process flow modeling and bench scale experimental design. During the course of this study, a new process for coal hydrogasification to SNG was developed. In the new process, the hydrogasifier has a single pass with no hot gas recirculation. Hydrogen is directly injected into hydrogasifer. A tip burner is used to fire a minimum portion of hydrogen in the presence of oxygen (95 or 99.5% purity) to generate a high temperature hydrogen-rich gas stream and a small amount of water vapor. Hot hydrogen then contacts with coal resulting in the production of methane. The reaction is exothermic and will result in a bulk gas temperature increase. The desired operating conditions for hydrogasifer are 1600°F and 1000 psi. It is anticipated that 60% carbon in the coal can be hydrogasified in this manner. Unconverted coal will be introduced into oxy-burner with or without additional fresh coal to produce CO2 and generate electricity. The CO2 stream out of oxy-burner is introduced to the algae farm. The algae farm can capture about 150 tons/acre-year carbon dioxide and produce 11,000 gallons biodiesel and 50 ton cattle meal annually per acre, based GreenFuel Technology GEN3 performance tests.

Process modeling has been performed to determine the optimum operating conditions and investigate the mass and energy flow of the whole process. The process is simulated in ASPEN 2004.1 and includes hydrogasification, ash removal, desulfurization, methanation, water separation, hydrogen membrane separation and oxy-burner et al. processes. The Aspen modeling indicates that with 60% carbon conversion in the hydrogasifier, more than 50% methane yield can be achieved. The preferred operating conditions are 1000 psi and 1600°F. Excess hydrogen is needed to ensure high carbon converion.

Bench scale lab testing was initiated to mainly determine the energy and material balance around the gasifier including flow rate to estimate the hydrogasification kinetics. The effect of temperature, pressure, H2/C ratio, H2/O2 ratio, coal residence time and coal particle size will be studied. The composition of gas stream (CH4, CO, CO2, H2S, H2O, H2, light HCs), the weight and composition of oil (light aromatics, tar) as well as ash (C, S) will be analyzed.