At present, the mechanized sampling and preparation system has been widely popularized in coal power plants in China, which mainly includes the bridge type auger sampling system for truck, the auger sampling system for railcar, the head cross belt sampling system and the central cross belt sampling system. These systems are usually composed of four parts: the head sampler, crusher machine, division machine and the residue return system. Compared with the manual sampling, the mechanical sampling reduces the labor intensity, avoids the subjective error of artificial sampling and improves the precision of sampling.
The retention sample collection is a crucial part during the sampling and sample preparation process. In the retention sample collection process, the moisture loss of the samples is an inevitable phenomenon. Following, we will make a study on the causes that result in this phenomenon and find some methods to reduce the moisture loss.
In the process of sample collection, no matter the opening-degree of the sample collection barrel or the environmental temperature and humidity has a certain impact on the moisture loss of retention samples. According to study on the influence of the retention coal samples weight on moisture loss, the opening-degree of the sample collection barrel on moisture loss and the environmental temperature and humidity on moisture loss in the process of collecting samples, we found that the larger the mass of retention samples, the smaller the moisture loss rate; as the opening-degree of the sample barrel reduces, the moisture loss rate decreases and when the ambient temperature rises or humidity drops, the water loss rate increases. Therefore, we can reduce the moisture loss during the retention samples collection process by increasing the weight of retention coal samples, reducing the opening between the closed feed inlet and the sample collection barrel, lowering the ambient temperature and increasing the environmental humidity. They are of great significance to reduce the moisture loss of the whole equipment.
The Effect of Coal Sample Mass on Moisture Loss
We can respectively weigh the test coal samples with the granularity of 13 mm and put them in the no. 1-8 sample collection barrels (11.5 cm in diameter and 26 cm in height). The mass of the sample collection barrels should be weighed for 1 time every hour within 6 hours. The ambient temperature and the humidity should be 28.6 – 29 degree centigrade and 77%. The external water of the coal samples is 7.
According to the test result, we found that with the increase in the coal sample height, the water loss did not increase significantly. While with the growth of the coal weight, the water loss rate was decreased. In addition, we can take the coal sample with the weight of 3,000 g as an example, taking time as the horizontal coordinate axis and the accumulated amount of the moisture loss as the vertical coordinate, drawing a coordinate map. The results are shown in the figure below. When the ambient temperature is 28.6 – 29 degree centigrade and the humidity is 77%, the moisture loss within 6 hours presents a good linear relationship with time. The longer the coal sample is placed, the greater the moisture loss. So if we want to reduce the moisture loss of the coal samples, we need to increase the weight of the samples and decrease the storage time.
In the above contents, we mainly talked about the effect of coal sample mass on the moisture loss. In the article Study on the Moisture Loss in the Retention Sample Collection Process of the Coal Sampling Machine (2), we will talk about some other factors in details. Hope this article will bring you some useful information.