No abstract

Painan coals of West Sumatra were selected as semi-anthracitic coal sample for studying the physicochemical properties such as measurement, evaluation and description of the changes of surface characteristic of coal sample and their oxidation in the atmospheric air at a temperature ranging from 105 to 400°C for 30 min. Several methods are adopted to analyze and discuss several phenomena of the oxidized Painan coal surface during oxidation process for the change in the physicochemical properties as determined by Atomic Force Microscope (AFM), contact angle, Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric and Differential Thermal Analysis (TG-DTA) analyses as well as other supporting analytical equipment. AFM analyses revealed some changes in adhesion force and surface morphology with more adhesion force available between 0.6 and 8.6 nN on polished coal surfaces due to the increased oxidation temperature. The study revealed that the extent of hydrophobicity of coal surface decreased with the increased of oxidation temperature expressed as contact angles at about 80°and 20°. Another phenomenon occurred during the experiment was hydrophilicity index of coal surface increase at approximately 1.3 and 2.9. Oxidation of coal that occurred with increased temperature also indicated an increase in oxygen content from 3.8% to 22.9 wt%. Increased oxygen functional group also noted that oxidation of coal took place during the treatment. We also found that oxidation treatment also affected the combustion properties of coal: decreasing ignition temperature between 452.9 and 317.6, lowering the reactivity of coal at maximum combustion rate temperature, and reflecting their char characteristics as burnt out, ranging from 652.3 to 648.5°C.

GEM is one of the composite material which is used as backfill to protect the electronic equipments, communication network and to stem the voltage of the electrical power problem. GEM has been commonly used in Indonesia, but it is still imported. Therefore it is important to look for substitution minerals. The main compositions of GEM are silica (Si), Aluminium (Al) and carbon (C ). Therefore, this research focus on the aluminofilosilicate minerals (bentonite, from Karangnunggal, Tasikmalaya), and charcoal. Laboratory experimentations are involved characterizations of raw materials, mineral engineering, and developing formulation and prototype of GEM. The result of this characterizations show that Nabentonite is the most potential material for GEM raw materials (514 Ohm cm).

Coal bottom ash was included in Hazardous and Toxic Waste (LB3), which requires seriously manage not to warm the environment and humans health. LB3 management becomes an obligation for the industry which producing it and being a burden in itself due to the project of waste utilization often regarded as the high-cost investment projects or less profitable. This study aims to conduct an economic assessment of pilot-scale projects to reuse bottom ash to support the clean industry strategy. The study mixed coal bottom ash with biomass from municipalities solid waste (MSW), called bio-coal fuel. These raw materials were combined with a composition 60%:40% weight (bottom ash: biomass) to be briquette form by adding amylum as a binder. This study used the benefit-cost analysis approach to assess economic feasibility. Tree indicators used in this study were net benefit-cost ratio, payback period, and return on investment. These indicators provided the company policy to continue or stop this project. The finding study showed that the company got a payback period and the net benefit from the ninth year. The company also achieved a net B/C ratio was more than one, and ROI was 1.09 times in the ninth year. The other beneficiaries acquired by the company was included external costs, such as risks from commitment failure by third parties in coal waste management, costs rising risk of purchasing coal, and given a positive value for providing employment.

ABSTRAK Makalah ini membahas perbandingan nilai porositas sampel karang Porites berdasarkan citra yang dihasilkan dari teknik optik dan micro-CT. Teknik optik biasa digunakan dalam perhitungan porositas batuan dengan menghitung prosentasi lubang pori dengan matrik batuan pada sayatan tipis. Sedangkan micro-CT merupakan teknik nondestructive yang sering digunakan dalam analisa 3D untuk menginvestigasi struktur internal sebuah benda, termasuk rongga pori. Karakteristik dan nilai porositas karang Porites ditentukan dengan mengklasifikasikan citra micro-CT dan optik sebagai pori dan matrik berdasarkan tingkat keabuannya. Karakteristik pori menunjukkan bahwa teknik optik lebih bisa mengidentifikasi struktur pori yang menerus dan memanjang, sedangkan micro-CT lebih mampu mengidentifikasi pori dengan kebundaran tinggi. Hasil penelitian juga menunjukkan bahwa metode micro-CT mampu mengidentifikasi ruang pori lebih banyak dibanding pada klasifikasi secara optik pada lapisan yang sama. Nilai porositas karang Porites berdasarkan teknik micro-CT dan teknik optik tidak menunjukkan perbedaan yang signifikan sehingga teknik micro-CT dapat digunakan dalam perhitungan porositas karang Porites dimana teknik micro-CT mampu mengidentifikasi pori yang sering tidak teridentifikasi oleh teknik optik.