IMPROVEMENT OF LOW RANK COAL PROPERTIES BY VARIOUS UPGRADING PROCESSES

A low rank coal from Banko, South Sumatera was used to study the properties improvement of the coal due to coal upgrading process. Various coal upgrading processes were conducted i.e. upgraded brown coal (UBC), hot water drying (HWD) and steam drying (SD). The UBC process was carried out in pilot scale with a capacity of 5 tons/day at temperature of 160°C and pressure of 0.35 MPa, while the HWD and SD pro- cesses were conducted in laboratory scale using autoclave at the temperature of 300ºC and pressure of about 12 MPa for 1 hour. The result indicates that the properties of Banko coals after the UBC, HWD and SD processes were improved. The calorific value of the upgraded coals was significantly increased in relevant to the decreasing of inherent moisture content and have better combustion characteristics than that of the raw coal. The highest calorific value can be achieved by SD process, followed by HWD and UBC processes

STUDY OF POLYMETHACRYLATE (PMA) INFLUENCE AS DISPERSANT ON UBCWM PREPARATION

Upgraded brown coal water mixture (UBCWM) is a mixture of coal resulted from upgraded brown coal (UBC) process with water in a certain ratio to form a homogeneous and stable suspension during storage, transpor- tation and combustion. UBCWM can be used as direct fuel as substitute for heavy fuel oil, particularly in industrial boilers. To obtain a UBCWM with high coal concentration and low apparent viscosity as well as good flow characteristics, the addition of additive as dispersant is needed. To study the effectiveness of polymethacrylate (PMA) as dispersant, research on the effect of PMA in the production of UBCWM needs to be carried out. The research was conducted by preparing UBCWM with the addition of PMA of 0.1, 0.3 and 0.5% and also carboxymethyl cellulose (CMC) of 0.01% as stabilizer. Preparation of UBCWM using 0.3% PMA and CMC, xantham gum (S- 60) and ransham gum (S-194) of 0.01% each was also carried out. Flow characteristic of the UBCWM was measured by using a viscometer at various shear rate. Results indicate that the addition of 0.3% PMA in the production of UBCWM is effective as dispersant. The addition of 0.5% PMA did not significantly reduce apparent viscosity. The addition of 0.3% PMA together with 0.01% CMC produces UBCWM with the highest coal concentration of 58.3% with yield stress of 23.22 Pa

STRATEGY TO MAXIMIZING THE USE OF COAL AND ASSOCIATED GASEOUS FUELS IN SOUTH SUMATERA BASIN

South Sumatera Basin has been known as one of the most promising sedimentary basins in Indonesia. This basin has large coal resources and is currently also believed to have an enormous amount of coalbed methane (CBM) resources. The coal seam in the basin is considerably thick and continuous, low ash and sulphur contents and could be found at favourable depth for CBM development. Coal seams can be ex- ploited by traditional mining methods, which are open cut and underground minings. When the coal seam is not economic to exploit using traditional method, underground coal gasification (UCG) technology could be implemented to optimize the use of coal and associated gaseous fuels in the basin. However, CBM operation has to be conducted before UCG operation. South Sumatera coal could be utilized for direct combustion in mine site in order to reduce transport cost; could be upgraded to obtain high calorific value coal or converted to gas, liquid and coke fuels through gasification, liquefaction and carbonization technologies

PEMBUATAN DAN PEMBAKARAN CWF DARI BATUBARA HASIL PROSES UPGRADING

Coal Water Fuel (CWF) adalah suatu campuran antara batubara halus dan air dalam perbandingan tertentu membentuk suatu suspensi kental yang homogen dan stabil dengan penambahan zat aditif. CWF dapat digunakan sebagai bahan bakar pengganti minyak berat pada industri-industri yang biasa menggunakan ketel uap (boiler). Hasil penelitian pembuatan CWF dengan menggunakan batubara produk proses upgraded brown coal (UBC) menunjukkan bahwa dari berbagai jenis dispersan sebagai aditif yang dicoba, yaitu (Ca ligno sulfonat, Na ligno sulfonat, dodecyl bensen sulfonat, PHPA dan SPA), dodecyl bensen sulfonat sebanyak 0,3% dan CMC 0,05% sebagai penstabil merupakan jenis aditif yang terbaik, yang menghasilkan CWF dengan persen padatan tertinggi, yaitu 60% dan viskositas 1.215 cP pada kecepatan putar spindel 100 rpm

EFFECT OF COAL UPGRADING ON RHEOLOGY OF COAL WATER MIXTURE

Coal water mixture (CWM) is coal-water slurry in which particles of coal with a certain particle size distribution are suspended in water. CWM is required to have the highest possible coal concentration and a moderate viscosity in order to make handling easy. The main purpose of this study is to obtain the effect of coal upgrading on the rheology of CWM in terms of finding the most suitable dispersing additive in producing CWM with highest coal concentration. Two kinds of coal, raw and upgraded coal, from three areas in Indonesia have been used. Three kinds dispersing additives, i.e. formalin conden- sation product of naphthalene sulfuric acid (NSF), polystyrene sulfonic acid (PSS) and poly (meth) acrylate (PMA) were tested to produce CWM with good flow characteristics. The rheology of CWM was prepared, measured by a stress control type rheometer (Rheometric Scientific Co. Ltd., SR-5) in steady shear mode at 25ºC. The apparent viscosity of upgraded coals showed a better slurry-ability of CWM as a function of coal concentration for every dispersing additive compared to the raw coal

CHEMICAL AND PHYSICAL PROPERTIES OF UPGRADED BROWN COAL

Results of proximate analyses indicate that inherent moisture of the upgraded coals decrease signifi- cantly compared to that of the raw coals. Hence, the calorific value of the upgraded coals increases. The ash content of the upgraded coals did not change obviously due to the UBC process which was conducted at low temperature. However, the volatile matter content increase slightly due to the residue plugs over coal pores to prevent re-absorb of moisture. From ultimate analyses, carbon content of the upgraded coals increases, whereas the hydrogen and oxygen contents decrease. The UBC process hardly effects to the sulfur and nitrogen contents. The equilibrium moisture of the upgraded coals was determined by using ASTM Standard method, most of them were less than 9%. The functional group of C-H and C=O of the upgraded coals were slightly less than that of the raw coals. The aromaticity of coal, all of the upgraded coals was increase. The petrography of both the raw and the upgraded coals indicates that the mean vitrinite reflectance was slightly higher in the upgraded coal compared to that of the raw coal. There was no significant quantity and textural differences of maceral in both coals. The specific surface area of the upgraded coals was lower than that of the raw coals due to the plugging of pore structure and shrinkage by residual oil addition. The briquettability of Upgraded coal briquette according to drop shatter test and compressive strength indicates good characteristics of briquette

PRA STUDI KELAYAKAN FINANSIAL PEMBANGUNAN COAL WATER MIXTURE DI INDONESIA (PROSES UPGRADING BERTEKNOLOGI HOT WATER DRYING)

Sesuai dengan Undang-Undang Nomor 4 Tahun 2009 tentang Pertambangan Mineral dan Batubara serta Peraturan Pemerintah Nomor 23 Tahun 2010 tentang Pelaksanaan Kegiatan Usaha Pertambangan Mineral dan Batubara, maka pemerintah perlu memaksimalkan pengolahan batubara di dalam negeri. Salah satu teknologi pengolahan batubara yang akan dikembangkan adalah coal water mixture (CWM). Pabrik demo CWM direncanakan akan dibangun oleh JGC Corporation dari Jepang bekerjasama dengan Puslitbang Teknologi Mineral dan Batubara (tekMIRA) dari Kementerian Energi dan Sumber Daya Mineral serta PT Sinar Mas pada tahun 2011 di Karawang, Jawa Barat, Indone- sia. Pabrik demo CWM ini akan menggunakan batubara peringkat rendah yang telah melalui proses upgrading teknologi hot water drying (HWD).Coal water mixture (CWM) adalah bahan bakar campuran antara batubara dan air serta bantuan zat aditif sehingga membentuk suspensi kental yang homogen dan stabil selama penyimpanan, pengangkutan dan pembakaran. CWM dapat menggantikan minyak bakar berat (heavy fuel oil) yang biasa digunakan di industri-industri yang menggunakan boiler sebagai penghasil uap untuk proses maupun untuk pembangkit listrik.Penelitian ini bertujuan untuk mengkaji aspek finansial dari pembangunan pabrik komersial CWM di Indonesia. Analisis finansial dilakukan dengan menggunakan kriteria Net Present Value (NPV), Internal Rate of Return (IRR), Return on Investment (ROI), dan Pay Back Period (PBP). Metodologi yang digunakan adalah studi pustaka melalui laporan serta informasi dari pihak JGC Corporation. Hasil penelitian menunjukkan bahwa pembangunan pabrik komersial CWM secara finansial menguntungkan. Namun pra studi kelayakan finansial ini masih perlu ditindaklanjuti dengan studi kelayakannya.

Prospective observational cohort study on grading the severity of postoperative complications in global surgery research

Background The Clavien–Dindo classification is perhaps the most widely used approach for reporting postoperative complications in clinical trials. This system classifies complication severity by the treatment provided. However, it is unclear whether the Clavien–Dindo system can be used internationally in studies across differing healthcare systems in high- (HICs) and low- and middle-income countries (LMICs). Methods This was a secondary analysis of the International Surgical Outcomes Study (ISOS), a prospective observational cohort study of elective surgery in adults. Data collection occurred over a 7-day period. Severity of complications was graded using Clavien–Dindo and the simpler ISOS grading (mild, moderate or severe, based on guided investigator judgement). Severity grading was compared using the intraclass correlation coefficient (ICC). Data are presented as frequencies and ICC values (with 95 per cent c.i.). The analysis was stratified by income status of the country, comparing HICs with LMICs. Results A total of 44 814 patients were recruited from 474 hospitals in 27 countries (19 HICs and 8 LMICs). Some 7508 patients (16·8 per cent) experienced at least one postoperative complication, equivalent to 11 664 complications in total. Using the ISOS classification, 5504 of 11 664 complications (47·2 per cent) were graded as mild, 4244 (36·4 per cent) as moderate and 1916 (16·4 per cent) as severe. Using Clavien–Dindo, 6781 of 11 664 complications (58·1 per cent) were graded as I or II, 1740 (14·9 per cent) as III, 2408 (20·6 per cent) as IV and 735 (6·3 per cent) as V. Agreement between classification systems was poor overall (ICC 0·41, 95 per cent c.i. 0·20 to 0·55), and in LMICs (ICC 0·23, 0·05 to 0·38) and HICs (ICC 0·46, 0·25 to 0·59). Conclusion Caution is recommended when using a treatment approach to grade complications in global surgery studies, as this may introduce bias unintentionally