Co-gasification of coal and empty fruit bunch in an entrained flow gasifier : A process simulation study

Co-gasification of coal and biomass is a proven method to improve gasification performance and a platform towards being independent of fossil fuel in power generation. Thus, this research was conducted to assess the feasibility of coal and EFB as fuels in co-gasification using Aspen HYSYS. A sequential model of an EFG was developed to predict the syngas composition and the optimum operating condition of the gasifier. The process was modelled with a set of five reactors to simulate various reaction zones of EFG in accordance with its hydrodynamics. The model considers devolatilization, char and volatile combustion, char gasification and water-gas shift reactions. The model prediction has exhibited excellent agreement with the experimental results. Three parameters of BR, Top and S/F were considered to account for their impacts on syngas composition in the process. The CE, CGE, PE and HHV were adopted as the indicators of process performance. The optimal values of BR, Top and S/F were 50%, 950°C and 0.75, respectively. While the value of CE reached above 90% and the maximum value of CGE, PE and HHV was obtained. This finding should be helpful in designing, operating, optimizing and controlling any co-gasification process especially in the entrained flow system

Towards an effective potential for the monomer, dimer, hexamer, solid and liquid forms of hydrogen fluoride

We present an attempt to build up a new two-body effective potential for hydrogen fluoride, fitted to theoretical and experimental data relevant not only to the gas and liquid phases, but also to the crystal. The model is simple enough to be used in Molecular Dynamics and Monte Carlo simulations. The potential consists of: a) an intra-molecular contribution, allowing for variations of the molecular length, plus b) an inter-molecular part, with three charged sites on each monomer and a Buckingham "exp-6" interaction between fluorines. The model is able to reproduce a significant number of observables on the monomer, dimer, hexamer, solid and liquid forms of HF. The shortcomings of the model are pointed out and possible improvements are finally discussed.Comment: LaTeX, 24 pages, 2 figures. For related papers see also http://www.chim.unifi.it:8080/~valle

E-DEMOKRASI DI INDONESIA, ANTARA PELUANG DAN HAMBATAN PENDEKATAN FENOMENOLOGIS

Hadirnya teknologi informasi dan komunikasi (TIK) serta teknologi digital lainnya termasuk internet, telah menjadi media baru dan dijadikan sebagai instrumen penting bagi organisasi swasta (bisnis) dan organisasi publik, salah satunya adalah organisasi pemerintahan. Pemanfaatan TIK dan internet pada organisasi pemerintahan dikenal dengan istilah e-government. Pelaksanaan e-government bertujuan untuk meningkatkan efisiensi, efektifitas, transparansi, dan akuntabilitas penyelenggaraan pemerintahan, sehingga tercapai penyelenggaraan pemerintahan yang baik (good governance). Sementara, TIK dan internet sebagai media dalam proses demokrasi suatu negara dikenal dengan istilah e-demokrasi. Kedua istilah tersebut adalah dua entitas yang berbeda, tetapi saling terkait. Perkembangan TIK dan internet beberapa tahun terakhir yang diikuti oleh peningkatan penggunanya adalah merupakan peluang bagi lembaga-lembaga pemerintah dan partai politik untuk melakukan perubahan sistem, baik sistem administrasi, pelayanan publik maupun sistem demokrasi. Namun, inisiatif penerapan e-demokrasi di Indonesia masih dikatakan sebagai tahap pengenalan. Sehingga, banyak masalah yang perlu menjadi perhatian sebelum e-demokrasi diimplementasikan. E-demokrasi tidak sekedar mengimplementasikan TIK dan internet ke dalam sistem demokrasi, tetapi banyak aspek-aspek nontechnology yang menjadi hambatan dan perlu penyelesaian. Hambatan pertama adalah terkait dengan implementasi e-government yang telah di laksanakan di Indonesia selama ini. Beberapa hambatan lain yang teridentifikasi diantaranya adalah masalah belum adanya nomer identitas warganegara yang valid, masalah budaya birokrasi dan budaya politik, masalah kesenjangan digital, masalah partisipasi, masalah teknologi, dan masalah organisasi

Effects of sodium hydroxide (NaOH) solution concentration on fly ash-based lightweight geopolymer

In this study, the effects of NaOH concentration on properties of fly ash-based lightweight geopolymer were investigated. Lightweight geopolymer was produced using fly ash as source materials and synthetic foaming agents as air entraining agent. The alkaline solutions used in this study are combination of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) solution. Different molarities of NaOH solution (6M, 8M, 10M, 12M, and 14M) are taken for preparation of 50 x 50 x 50 mm cubes of lightweight geopolymer. The ratio of fly ash/alkaline solution, Na2SiO3/NaOH solution, foaming agent/water and foam/geopolymer paste were kept constant at 2.0, 2.5, 1:10 and 1:1 respectively. The samples were cured at 8