Study on the moisture state of lignite by NMR technique |
| With the acceleration of China's industrialization process and increasing energy demand, how to use low-level coal resources efficiently is of great significance. In the eastern part of Mongolia, China, lignite is abundant, but the high moisture content of lignite makes its economic benefits in transportation, storage and utilization lower. The moisture in the coal is divided into the free water in the crack and the surface according to the state of existence, the bound water in the mesopores and macropores, and the adsorbed water in the micropores. Removing from coal is a continuous and complex process in water to remove internal water. Free water existing in coal-like fissures and coal surface is easily lost during contact with the atmosphere. However, the moisture present in the capillary is difficult to lose due to the capillary force, and some moisture is present in the coal. In small voids, it is difficult to lose due to strong surface adsorption. Studying the existence state of moisture in lignite and the process of moisture removal have a great effect on improving the process conditions.
Nuclear magnetic resonance technology can explain the existence of water in coal samples from a microscopic point without damaging the coal sample. Combined with other analytical methods, it can provide data support for determining the lignite dehydration and upgrading process. |
| Low field NMR experimental results: effect of drying temperature on moisture in coal samples | The brown coal was dried and dehydrated at different temperatures (50 ° C, 70 ° C, 90 ° C, 105 ° C, 150 ° C), and the distribution of the sample relaxation signal after inversion was as shown in the following figure.
As the drying dehydration temperature increases, the relaxation peak gradually moves to the left. When the treatment temperature is lower than 50 °C, there is no peak in the range of 1~10ms. After the treatment temperature is higher than 50°C, it appears in the range of 1~10ms. The peaks, and the peaks of the samples with a treatment temperature between 70 and 105 ° C are similar, while the peaks of the samples with a treatment temperature of 150 ° C are obviously shifted to the left. |
| References: “Study on the migration of water and its drying kinetics during the upgrading of lignite in Lignite†(Materials Report B: Research) February 2014 (below) Volume 28, Issue 2 |
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