استفاده از آزمایش سیلندر و پیستون برای پیش‌بینی تاثیر ایجاد بار در گردش محصول لبه بر روی عملکرد آسیاهای غلتکی فشار بالا

نوع مقاله: گزارش فنی

نویسندگان

1 بخش مهندسی معدن-دانشگاه شهید باهنر کرمان

2 رییس پژوهشکده آهن و فولاد گل گهر

چکیده

مکانیزم غالب شکست درآسیاهای غلتکی فشار بالا (HPGR)، شکست فشارشی است.  جهت تحقیقات پایه و کاربردی شکست فشارشی، آزمایش­های ساده، سریع الانجام و دانش بنیان مورد نیاز است.  بنابراین برای اولین بار در ایران با طراحی جدید و ساخت سیلندر و پیستون و همچنین پانچی برای جداسازی محصول مرکزی و محصول لبه، آزمایش­های شکست فشارشی با فشار 1730 بار با استفاده از پرس هیدرولیکی قابل کنترل، بر روی خوراک خط چهارم این مجتمع انجام شد. محصول لبه با خوراک تازه با نسبت بار در گردش 8/0 با هم ترکیب شدند و در سیلندر با همان فشار، مجدداً مورد خردایش قرار گرفتند. در این حالت D50 محصول نهایی با استفاده از بار در گردش به میزان 25% کاهش یافت. بررسی ذرات کیک محصول آزمایش سیلندر و پیستون با استفاده از میکروسکوپ نوری و میکروسکوپ الکترونی (SEM) نشان داد که تعداد کمی از آنها دارای ترک سطحی هستند. بنابراین، ایجاد بار در گردش محصول لبه، احتمال شکست یا ایجاد ترک را برای ذرات افزایش خواهد داد. با توجه به این نتیجه، فلوشیت پیشنهادی برای ایجاد بار در گردش در مقیاس صنعتی ارایه شد. همچنین جهت محاسبه انرژی مصرفی ویژه از گراف نیرو-جابجایی که از داده­های آزمایش سیلندر و پیستون به دست آمد؛ استفاده شد. در واقع انرژی جذب شده در طی فشارش، تابعی از فشار اعمال شده بر پیستون است و از مساحت زیر نمودار نیرو-جابجایی، به دست می­آید. این مساحت با استفاده از روش محاسبات عددی به نام فرمول ذوزنقه (trapezoid formula) محاسبه شد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Prediction of the Edge Recycle Effect on the High Pressure Grinding Rolls Performance Using Piston and Die Test

نویسندگان [English]

  • Reza Kazerani nejad 1
  • Abbas Sam 1 2
1 Dept. of Mining, Shahid Bahonar University of Kerman
2 Dept. of Mining, Shahid Bahonar University of Kerman
چکیده [English]

Summary
The dominant mechanism in the High Pressure Grinding Rolls (HPGR) is compressive breakage.  A laboratory scale experiment could be implemented to study the compressive mechanism.  In the present research, for the first time in Iran, the piston and die device consists of controllable hydraulic press (P&D test) were utilized at Golgohar complex to study the compression breakage.  This test was applied to investigate the edge recycle effect on the HPGR performance.
Introduction
The usage of HPGR in the iron mineral processing plants is extending in Iran.  Edge product of the HPGR is coarser than the central product that is not favorable for downstream processes.  It is imaginable that the HPGR performance could be controlled by separating and circulating the edge materials.  Before any mechanical changes in the industrial HPGR machine at the 4th train of iron concentrate plant in Golgohar, it was necessary to investigate the edge recycle effect fundamentally.  From operational point of view, the HPGR in pilot scale is required for feasibility study, investigating the variables and predicting the associated operational advantages of any changes.  The pilot plant scale of HPGR is not available at Golgohar complex.  Also, conducting the pilot scale experiment requires a significant amount of samples, which is costly and time-consuming.
In both cases, fundamental and operational researches, the simple, available and knowledge-based laboratory tests are required.  In addition, the laboratory tests play an important role in understanding and prediction of variable behaviors in industrial scales.
Methodology and Approaches
A laboratory method was developed to study the effect of the edge product recycling. After designing and constructing of the piston and die system, compressive breakage tests were conducted at the pressure of 1730 bars using samples taken from the feed of the 4th train of the concentrate plant.  For separating the central product from the edge product of the experiments, a punch system was designed and constructed.  To obtain the effect of edge product circulation, this material was mixed with the fresh feed at the ratio of 0.8.  The sample was compressed at the same pressure.  The D50 of the product was reduced by 25% with the edge product recycle.  Particles from test product were studied using optic microscope and  scanning electron microscope (SEM).  Also a numerical method (trapezoid formula) was implemented to calculate the compressive breakage specific energy.
Results and Conclusions
Study of piston and die test cake product particles using optic microscope and scanning electron microscope (SEM) showed that just a few numbers of particles have surface micro cracks.  Therefore, circulating the edge product will increase probability of particle breakage or crack creation.  Finally a flowsheet was proposed which allows circulating the edge product of the industrial HPGR at the 4th train of the concentrate production of the Golgohar complex.
Also the compressive breakage specific energy was obtained by a numerical method named trapezoid formula using force-displacement graph.  This graph was attained from piston and die test data.

کلیدواژه‌ها [English]

  • High Pressure Grinding Rolls
  • HPGR
  • Circulating Load
  • D&P Test
  • Micro Cracks
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