Effect of jet mill operating parameters during the production of ultrafine limestone.
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Date
2011-01
Authors
Jamil, Noorina Hidayu
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Pengisaran halus batu kapur di dalam pengisar jet telah dilakukan dengan mengubah kadar suapan, halaju putaran pengkelas dan tekanan pengisar pada lima peringkat. Selain itu, keadaan dalam kebuk pengisar seperti jisim lapisan terbendalir dan tekanan dandang pengisar juga direkodkan. Partikel terkisar dicirikan berdasarkan taburan saiz partikel dan taburannya, kesan mekanokimia dan penambahbaikan bentuk partikel. Produk terkisar menunjukkan taburan secara poli-model di mana diameter momen isipadu berada di dalam julat antara 2.11μm hingga 7.12μm, manakala nilai taburan adalah di antara 1.1 hingga 2.9. Partikel halus diperolehi pada keadaan tekanan atasan dan jisim lapisan terbendalir sebanyak 1500g. Kesan mekanokimia dicirikan melalui Belauan Sinar-X dan FTIR. Pola belauan Sinar-X menunjukkan penurunan pada puncak keamatan, kelebaran tapak puncak dan perubahan posisi puncak. Darjah pengkristalan pada partikel terkisar adalah di antara 27.56% hingga 97.12%. Saiz kristal pula di dalam julat 144.1nm ke 228.2nm manakala terikan kekisi antara 0.153 hingga 0.201. Pengembangan kekisi kristal ditunjukkan pada sampel terkisar. Penurunan pada ikatan O-H melalui spektra IR menunjukkan terdapatnya kesan mekanokimia. Bentuk partikel dicirikan melalui nilai kebulatan di mana terdapat 30 % penurunan pada produk partikel. Mekanisma pemecahan lelasan membantu pemecahan pada bucu partikel di mana menghasilkan partikel sub-mikron manakala mekanisma pemecahan hentaman menghasilkan partikel dengan saiz micron. Partikel batu kapur kurang daripada 10m dengan taburan sempit dengan penambahbaikan bentuk partikel serta separa amorfus merupakan ciri-ciri yang sesuai untuk aplikasi pengisi di dalam pelbagai produk pembuatan.
Fine grinding of limestone in jet mill was carried out by varying the operational parameters such as feed rate, classifier rotational speed and grinding pressure at five levels. Besides that the inside mill condition such as holdup mass and grinding camber pressure was noted as well. The ground particle was characterized for particle size and its distribution, mechanochemical effect and improvement in particle shape. The ground product exhibits poly-modal distribution where the volume moment diameter ranged from 2.11μm to 7.12μm whilst the span values are in between 1.1 to 2.9. Finer particles were obtained at overpressure grinding chamber condition and the mass of holdup of 1500g. The mechanochemical effect was characterized through X-ray diffractogram and FTIR. The X-ray diffraction pattern exhibits reduction in peak intensity, peak base broadening and shift in peak position. The degree of crystallinity of the ground particles ranged from from 27.56% to 97.12%. The crystallite size ranged from 144.1nm to 228.2nm whilst lattice strain ranged from 0.153 to 0.201. The expansion of crystal lattice was observed in the ground samples. The IR spectra exhibits reduction of O-H band which indicate the mechanochemical effect has taken place. The particle shape was characterized through circularity values where a reduction of 30% in this value was observed in the ground particles. Abrasion breakage mechanism facilitates breakage of particles edges which produces sub-micron particles whilst impact breakage mechanism produces micron size particles. Limestone particles below 10m with narrow distribution and improved particle shape with partially amorphous characteristics is suitable for filler application in various manufacturing products.
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Keywords
Jet mill , Limestone