ABSTRACT

Sorting coal using x-ray transmission sensors has been explored since 1972 by Jenkinson et al. Coal sortability is assessed using washability derived from dual-energy X-Ray transmission (DE-XRT) system. Coal sorting is considered to be dry separation of coal that can be carried out before coal is send to the processing plant. It can act as deshaling/destoning process or it can also be used to selectively mine shallow coal seams to avoid overburden contamination hence dilution. There are a few commercial concepts in the coal industry which utilizes the XRT sensors to sort the coarse particle coal. In order to define final product quality in terms of ash as well the efficiency of any separation based on density such as yield, washability is used to determine the separation process parameter such as density of separation, e.g. specific gravity. Washability characteristics have been traditionally assessed using the float-sink (washability) tests. These analyses determine how much of coal can be separated from associated rock (mineral matter) in liquids of different densities. However, the test work requires a wet processing where organic liquids, referred to as heavy liquids are used. The test work is very time consuming as it requires significant amount of time to complete full washability for a wide spectrum of coal particles. To avoid using toxic chemicals and save time, the DE-XRT can easily become an alternative method to assess the washability of coarse coal before the coal is processed by sorting to establish separation parameters and obtain information about the yield of clean coal of desired quality in terms of ash content. In this project in order to assess effectiveness of DE-XRT for sorting and at the same time to derive the washability data for the coarse coal, the test work has been designed to test various lithotypes identified from coarse coal sample. As a result, the test work included classification of coal lithotypes (larger pieces of coal of certain petrographic composition), density measurement using both DE-XRT and float-sink tests and ash analysis. The results are compared to float-sink tests for coarse coal fractions obtained by proxy washability analysis derived from pycnometry. Similar to float-sink tests, the DE-XRT can estimate a relative density by measuring the attenuation of x-rays from two different energy levels. The paper explains the basics of the DE-XRT analysis and its data processing methods to determine the relative densities and how to derive washability curves and density of separation for coal sorting. The basic principle of dual-material decomposition is adopted from Dual-Energy CT in the medical industry where the sum of each vector provides a proportion of the two material.

摘要

自 1972 年以来，Jenkinson 等人一直在探索使用 X 射线透射传感器对煤炭进行分类。煤炭分选性使用源自双能 X 射线传输 (DE-XRT) 系统的可洗性进行评估。煤炭分选被认为是可以在煤炭被送到加工厂之前进行的煤炭干选。它可以作为去页岩/去石过程，也可以用于选择性地开采浅层煤层以避免覆盖层污染从而稀释。煤炭行业有一些商业概念利用 XRT 传感器对粗颗粒煤进行分类。为了根据灰分以及任何基于密度（例如收率）的分离效率来定义最终产品质量，可洗性用于确定分离过程参数，例如分离密度，例如比重。传统上使用浮水槽（可洗性）测试来评估可洗性特征。这些分析确定了在不同密度的液体中可以从伴生岩石（矿物质）中分离出多少煤。然而，测试工作需要湿法处理，其中使用称为重液体的有机液体。测试工作非常耗时，因为它需要大量时间才能完成对各种煤颗粒的完全可洗性。为了避免使用有毒化学品并节省时间，DE-XRT 可以很容易地成为一种替代方法，用于评估粗煤的可洗性，然后通过分选来确定煤的分离参数并获得所需质量的洁净煤的产量信息。灰分含量方面。在本项目中，为了评估 DE-XRT 对分选的有效性，同时获得粗煤的可洗性数据，设计了测试工作来测试从粗煤样品中识别的各种岩型。因此，测试工作包括煤岩型分类（具有特定岩相成分的较大煤块）、使用 DE-XRT 和浮沉测试的密度测量以及灰分分析。将结果与通过比重瓶衍生的代理可洗性分析获得的粗煤部分的浮沉测试进行比较。与浮沉测试类似，DE-XRT 可以通过测量来自两个不同能级的 X 射线的衰减来估计相对密度。本文解释了 DE-XRT 分析的基础知识及其确定相对密度的数据处理方法，以及如何推导出煤分选的可洗性曲线和分离密度。双材料分解的基本原理取自医疗行业的双能CT，其中每个向量的总和提供了两种材料的比例。