What are the classifications, characteristics, and applications of coal automatic samplers?

Coal is a bulk, loose, and non-uniform commodity, and its price varies according to quality grades, directly affecting the economic benefits of coal preparation plants. To accurately assess the quality of coal products, sampling, sample preparation, and testing are necessary, with sampling being a fundamental and crucial step. Sampling involves extracting a representative sample from a large quantity of coal. If the sampling error is large, it directly leads to significant errors in coal quality analysis results. Therefore, when sampling coal, it is essential to select a sample that can represent the entire batch's quality.

In the past, manual sampling methods were commonly used, which were inefficient, uneven, and had low representativeness. With advancements in the industry and technology, automatic samplers have now replaced manual methods. Coal automatic samplers are devices designed for automatic sampling of entire batches of coal. They can sample during coal conveyance and transfer processes, offering high automation, efficient sampling operations, low labor costs, uniform sampling, strong representativeness, and ensuring sampling time, sub-sample quantity, and sub-sample weight, thereby improving the accuracy of coal quality testing.

 Classifications of Coal Automatic Samplers 

Based on the movement state of coal and the conveying equipment used, coal automatic samplers can be classified into belt automatic samplers and train (truck) automatic samplers.

1.  Belt Automatic Samplers 

Belt automatic samplers perform mechanized sampling during coal conveyance on a belt. They are mainly categorized into three types based on the sampling benchmark: time-based sampling, mass-based sampling, and stratified random sampling. Additionally, they can be classified as belt mid-section samplers and belt head samplers based on their installation and application positions.

   -  Belt Mid-Section Sampler : Installed in the middle section of the belt, this sampler rotates its sampling head at fixed time intervals, sweeping coal samples into a collection hopper to complete sampling.

   -  Belt Head Sampler : Installed at the ends (head or tail) of the belt, this sampler rotates its collection hopper at fixed time intervals. When the hopper rotates to the coal discharge point, it completes the sampling of one sample.

2.  Train (Truck) Automatic Samplers 

Train (truck) automatic samplers are used for sampling coal on trains or trucks. These samplers are primarily classified into bridge-type samplers and cantilever-type samplers, sampling solely based on coal quality. During sampling, the sampler inserts into the coal to take a full-depth column sample from top to bottom or removes a stratified sub-sample at a certain depth, adhering to the standard requirement of taking full-depth samples whenever possible.

 Characteristics and Applications of Different Coal Automatic Samplers 

Belt automatic samplers can effectively avoid the overlap of sampling with coal quality change cycles, offering higher sampling representativeness compared to train (truck) automatic samplers.

However, when using train (truck) automatic samplers, safety considerations must be taken into account, as they may not be able to sample the edges or bottom of the carriage.

Nevertheless, train (truck) automatic samplers comply with sampling process standards and are suitable for coal quality sampling occasions in power plants, coal yards, coal terminals, etc. Regardless of the sampling method, the representativeness of automatic sampling is unmatched by manual methods, offering high automation and efficient sampling.