Biogas is a form of alternative energy which can be obtained from the anaerobic degradation process of organic materials. The presence of CO2 in biogas needs to be removed to increase its CH4 concentration, which simultaneously increasing its calorific value and biogas qualities. This study used the water scrubber method to absorb CO2 and separate it from the CH4 contained in biogas. The variables used are the biogas pressures of 2, 3, and 4 bar and water flow rates of 0.1 and 0.15 L/s with a contact time of 60 seconds. The results of this study showed that the greatest effectiveness in both CO2 removal of 99.5 percent and CH4 increase of 38.18 percent were obtained at biogas pressure of 4 bar and water flow rate of 0.15 L/s. The most effective results of CO2 biogas removal were obtained at greater biogas pressures and water flow rates.

No abstract

The potential of water in Indonesia to generate electrical energy is quite large. This water potential is very suitable for generating small-scale energy. Water is sent through the penstock to drive the turbine. The turbine is coupled with a generator to produce electrical energy. The turbines used vary widely. For this research, the Kaplan turbine is used. The Kaplan turbine was chosen because of the low head required, which is suitable for conditions in Indonesia. The diameter of the Kaplan turbine tested was 25 cm. It is equipped with a guide vane arrangement. To obtain the Kaplan turbine output, the turbine is coupled to a generator. The test refers to the IEC standard. The turbine is operated at a constant speed and the generator voltage is fixed and the discharge varies. The results showed that the larger the guide vane opening, the higher the flow rate; the greater the flow rate of the resulting power, the greater. Efficiency for guide vane 30 openings occurs at 6.65m head and 0.065m 3 /sec volumetric flowrate with efficiency 50,13%. The highest efficiency is obtained for the guide vane 40 opening, which is 57.14% at 4.15 head and 0.074m3/sec flow rate.

Biogass is produced from fermentation of organic materials such as domestic waste and manure from animal husbandary. To increase the quality of biogass as a fuel, it has to be followed by the increasing of CH4 concentration. It could be done with seperating CH4 from other gases such as CO2. One of separation methode is using a water scrubber with water act as medium which as CO2 is more soluable to water than CH4. The result showed that CO2 absorption was increased followed by the increasing of the pressure and the biogass flow rate. The percentage of CO2 absorption at 2,5 m3 per hour of biogass flow rate and 8 bar was 4,6%, meanwhile it was 11,l% at 10 bar. In the other side, there was 9,5% of CH4 increasing at 10 bar. Therefore, CO2 separation from biogass using water scrubber at 10 bar is better than at 8 bar.

Waterwall merupakan tempat terjadinya proses perpindahan panas konveksi dan radiasi antara fluida kerja dengan gas hasil pembakaran pada Furnace. Ada 3 jenis waterwall, yaitu multi-pass waterwall, spiral waterwall, dan Benson waterwall. Pada teknologi supercritical boiler, jenis waterwall yang paling banyak digunakan yaitu jenis spiral waterwall karena perpindahan panas yang terjadi lebih baik dari jenis yang lainnya dan juga mengurangi jumlah pipa yang digunakan pada boiler tersebut. Temperatur dan tekanan fluida kerja pada supercritical boiler beroperasi di atas titik kritis, titik kritis tekanan fluida air adalah sebesar 22,1 MPa dan titik kritis temperatur 374,14°C. Hssil rancangan waterwall adalah jenis spiral waterwall dengan volume furaace waterwall sebesar 2952i,36 m3, tinggi furnace waterwall sebesar 65,66 m,  lebar furnace waterwall sebesar 21,42 m, kedalaman fumace waterwall sebesar 20,99 m dan diameter luar water tubes spiral waterwall sebesar 76,2 mm (3 in) serta ketebalan pipa tersebut sebesar 1,27 nn (0,05 in). Jumlah energi kalor yang diserap oleh waterwall adalah 689.33 MW.