Optimal Utilization of Biogas from Western Wastewater Treatment Plant of Nablus City

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Shehab Eddin, Motaz Adli Tawfeeq
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An-Najah National University
Wastewater treatment plants with anaerobic digesters produce sufficient quantities of biogas. One of the best methods to utilize biogas in such plants is the cogeneration technologies CHP, where two types of energy are produced from one fuel, i.e. electrical and thermal energy are produced on-site to be consumed in the same facility, and it is known that wastewater treatment plants are consumers of electrify and thermal power. In this study; for Western Wastewater Treatment Plant of Nablus city as a case study; optimal unit sizing and arrangement of CHP units which were Micro-Gas turbines and Internal Combustion Engines was studied by conducting an energy, economic and environmental calculations and analysis. The number of units to be operated every month was selected using four commercial Micro-Gas Turbines C30/30kW, C65/65kW, T100/100kW, C200/200kW from CAPSTONE manufacturer and three Internal Combustion Engines G3306/143kWe, G3406/235 kWe, CG132-8/400kWe from CATERPILLAR manufacturer, depending on the data of biogas production rates since there is instantaneous variation in these rates, but this variation is being regulated to a monthly level, using Biogas storage technology already being used. The number of Micro-Gas turbines or internal combustion engines that must be operated every month was calculated depending on the fact that these engines give the maximum efficiency when operated at full load or near it. Some of the alternatives can produce the needed annual thermal energy of 2137MWh as a total, but may have shortage during some months. It was found that the alternative which produced the maximum electrical energy was using one unit of the Internal Combustion engineCG132-8/400kWe with yearly energy production of 2442 MWh. Economic analysis were done using annual worth of cost calculation and finding the levelized cost of electrical energy, also, the total yearly saving from each alternative was also calculated. It was concluded that the using one unit of the Internal Combustion engine CG132- 8/400kWe has the lowest value of unit energy cost of 0.09$/kWh and annual savings of 195,243$/year. Environmental analysis were conducted to investigate the total CO2 emissions and other pollutional emissions, and was found that the alternative of using one unit of the Internal Combustion engine CG132-8/400kWe produced the maximum saving of CO2 production with a value of 2,203 Ton/year instead of the current situation of separate heat and electricity generation with CO2 production of 3,912Ton/year Achieving a total CO2 saving of 1,709Ton/year.