An analysis of CH4/N2 rich biogas production, fuel treatment process and microturbine application

Abstract

Biogas usually contains CH 4 and CO 2 as main components with the ratio of 6 : 4, and its composition varies with wide range depending on digester conditions. In addition to concentration change of each constituent, biogas composition could be changed due to the variations in the organic matter treatment process. The aim of the study is to analyze the production and application to a microturbine system of CH 4 /N 2 rich biogas produced from Gong-Ju wastewater treatment plant. CH 4 /N 2 rich biogas is produced due to the internal wastewater recirculation. The internal wastewater recirculation is intended to enhance NO 3 − removal without additional carbon source input. As a result, the digester was shown to be the highest contributor for nitrogen removal and average CH 4 concentration was lowered compared to the typical biogas composition. Nitrate removal rate was influenced by the internal recirculation ratio. Content of N 2 has no effect on biogas clean-up system performance. Besides, adaptability of CH 4 /N 2 rich biogas to microturbine was satisfactory with very low NOx and SO 2 concentration in microturbine exhaust gas. Influence of high N 2 concentration of biogas on NOx concentration was limited due to the low combustion temperature.

Turbomachinery analysis and design for hybrid SOFC-GT systems optimized performance

“…The CO and the NO emissions decreased significantly when biodiesel was used; on the other hand, the turbine inlet and exhaust temperatures did not change notably. Park et al [12] fed with biogas a microturbine. The raw biogas, from waste water treatment process, was further treated to remove the harmful contaminants (moisture, H 2 S, NH 3 , siloxane etc.)…”

“…The overall heat exchanger thermal conductance (UA s ) varies at off-design conditions according to the power low expression of Eq. (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18), where the reference values are for the design point of heat exchanger.…”

“…The vaned diffuser model utilizes a performance map that takes into account the Mach number, the total pressure and the blockage at throat section and estimates the pressure recovery coefficient for the specified geometric area ratio. Assuming one-dimensional flow the exit conditions are estimated and the enthalpy loss is given from the relation (7)(8)(9)(10)(11)(12)(13)(14)(15). The geometry parameters affecting the performance as well as the operational range are summarized in Table 7-3.…”

“…Equation (7)(8)(9)(10)(11)(12)(13)(14)(15)(16) represents the difference between the desired operating points for the compressor and the map operating points. The w i are weight factors for each operating point.…”

“…It is not necessary to be used for the isentropic efficiency since its values vary always between 0 and 1. (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17) The previous equation (Eq. (7-17)) requires the pressure ratio and the mass flow parameter at idle and full load conditions.…”