Study on the Moisture Loss in the Retention Sample Collection Process of the Coal Sampling Machine (2)

The water content in coal is easily affected by external factors, such as the weather, spraying during the transportation, type of sampling equipment, sampling method, storage time after sampling and so on, which will greatly affect the measured bias of the water content. The moisture loss during the retention sample collection process is a prevalent phenomenon. In last article Study on the Moisture Loss in the Retention Sample Collection Process of the Coal Sampling Machine, we talked about the effect of sample mass on moisture loss and the methods to reduce the moisture loss. In this article, we will study on the effect of the sample collection barrel opening-degree on moisture loss and the effect of storage conditions on moisture loss through some experiments.

The Effect of the Sample Collection Barrel Opening-degree on Moisture Loss

In order to study the effect of the sample collection barrel opening-degree on moisture loss, we will conduct an experiment. In the experiment, we respectively put 3000g test coal samples with the granularity of 13 mm in the no. 1-7 sample collection barrels. The opening-degree of the sample collection barrels includes all open, 3/4 open, 1/2 open, 1/8 open, covered and buckled with no washer, covered and unbuckled with a washer and covered and buckled with a washer. The experiment will last for 6 hours. The mass of sample barrels should be weighed every 1 hour and the ambient temperature and humidity should be kept at 24℃ – 26.3℃and 54% – 70%.

From the test result, we found that in the same environment, as the opening-degree of the sample collection barrels increases, the moisture loss of coal samples increases. When the barrel is fully opened, the moisture loss reaches 9.2g and when the barrel is covered and do not be buckled, the water loss is very small, only reduces 0.4g. So if we want to reduce the moisture loss, the best way is to seal the collection barrel to avoid the contact between the coal samples and the air.

The Effect of Storage Conditions on Moisture Loss

In this experiment, we need to separately put 3000 g of coal samples in the sample collection barrels that the opening-degree is gradually decreasing. These barrels are placed in four different environments (no direct sunlight) for 6 hours and the mass of sample barrels should be weighed every 1 hour. The experiment result shows that when the sample collection barrels are fully opened in the same ambient humidity, the higher the temperature is the greater the moisture loss. And if they are in the same temperature, the higher the humidity is the smaller the moisture loss. So during the detention sample collection process, the ambient temperature and humidity have an important influence on the moisture loss. We need to keep the detention sample collection environment as warm and humid as possible.

Under normal conditions, the detention samples will be collected and sealed or be sent into the preparation equipment after they are kept in the sample collection barrel for no more than 6 hours. The improper retention sample collection devices may lead to a severely low detection value of total moisture, resulting in huge economic losses. We can optimize the collection process through the methods we mentioned above, reducing the moisture loss to a negligible extent and lowering the cost of coal used by power plants or enterprises.

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