Nondestructive quantification of moisture in powdered low-rank coal by a unilateral nuclear magnetic resonance scanner

Abstract

Moisture content in coal powder is a critical index because it controls the difficulty of coal handling and ultimately its combustion efficiency in coalfired power plants. A unilateral proton nuclear magnetic resonance (NMR) scanner was applied in a laboratory to nondestructively quantify moisture content in powdered samples of brown and subbituminous coals. Due to the open geometry of the sensor unit, the scanner allows the nondestructive moisture quantification of a portion several millimeters below the surface of a large sample. Proton transverse relaxation was measured by the unilateral NMR scanner, and obtained moisture content values were compared with those by a conventional bilateral NMR apparatus. The comparison showed reasonable agreement with a root mean square residual of 4.1 wt.%H 2 O for a moisture content range of > 12 wt.% H 2 O (wet basis). This moisture-quantification performance by unilateral NMR is sufficient for the quality control of wet coal having a critical value of approximately 30 wt.%H 2 O in terms of the handling property (flow-ability). Because unilateral NMR requires no specific sample preparation, such as sample insertion into tubes, the system is potentially applicable to insitu nondestructive monitoring of the coal moisture in power plants to contribute to improved efficiency of handling and combustion. ARTICLE HISTORY

Optimized Unilateral Magnetic Resonance Sensor with Constant Gradient and Its Applications in Composite Insulators

“…Magnet optimization was carried out by calculating its magnetic field distribution. The remanent magnetization of a permanent magnet is equivalent to a toroidal current around the surface of the permanent magnet block, for which the magnetic field distribution of the permanent magnet can be calculated using the Biot–Savard law [ 20 , 21 ]. The magnetic field strengths B x , B y , and B z generated at any point P (x, y, z) in space can be expressed by Equations (2)–(6), where dB x , dB y , and dB z are the magnetic inductance components in the x, y, and z directions at point P. where is the magnetic permeability in a vacuum and is the surface current density.…”

Experimental Study on the Microstructural Characterization of Retardation Capacity of Microbial Inhibitors to Spontaneous Lignite Combustion

“…Figure 5 shows the fitting diagram of 13 C-NMR. According to the structural attribution of chemical shifts in the 13 C-NMR diagram [38], the functional group belonging to the region where each absorption peak appears is determined. According to the image, the chemical shift of this sample is mainly concentrated within 0~90 ppm relative to aliphatic carbon, 100~170 ppm relative to aromatic carbon, and 160~250 ppm relative to carbonyl carbon.…”

Optimized Unilateral Magnetic Resonance Sensor with Constant Gradient and Its Applications on Composite Insulators

“…Magnet optimization was carried out by calculating its magnetic field distribution. The remanent magnetization of a permanent magnet is equivalent to a toroidal current around the surface of the permanent magnet block, for which the magnetic field distribution of the permanent magnet can be calculated using the Biot-Savard law [20,21]. The magnetic field strengths Bx, By, and Bz generated at any point P (x, y, z) in space can be expressed by Equations ( 2) -( 6), where dBx, dBy, and dBz are the magnetic inductance components in the x, y, and z directions at the point P.…”