How to Get Representative Coal Sample?

Coal sampling is a necessary procedure for many coal power plant and coal process factory. Because of the various coal-fired boilers and the classified coal, how to ensure the coal quality is a crucial problem.

What is coal sampling? Sampling is a method to inspect the entire lot quality. In term of inspecting the entire lot, it will cost lots of time and money. In contrast, when the sample is taken properly, the sample can reflect the content of the lot.

Nowadays, the coal sampling technology is more and more mature. China as the biggest country of coal consumption, the technology of coal sampling grows rapidly. With the society developed, people recognize the importance of coal sampling gradually. As we know, the purpose of sampling is getting the representative sample from the entire lot, and getting the coal basic attribute by testing. While coal sampling procedure is the precondition of coal sample preparation and sample analytics. And the coal analytics result is the criterion of acceptance inspection and settlement price.

Coal is a kind of material which is difficult to sample. Due to the coal particle size and chemical composition is not uniform and this coal essential character results in the coal sampling procedure difficulty. According to some research, it said that the bias caused by sampling procedure takes 96 percent, and the sample analytics procedure takes 4 percent. So how to get the representative sample is a project which worth studying. How to get sample scientifically and normatively is a task for each worker who works with coal.

Generally, coal sampling means the sample from the coal truck, coal wagon, and the coal pile storage. For different worksite, the coal sampling methods are not similar.

Coal sampling method

The most common coal sampling method is getting coal sample from the coal trucks. The coal trucks are common in coal power plant, coal process factory. When making coal sample from the coal truck, workers should obey the ASTMD 7430 Standard or the ISO13909:4 Standard to sample.

Manual coal sampling method

manual coal sampling method

One coal sampling from the truck method is diagonal sampling by the coal trucks, we also called that three-sampling-point sampling method. The beginning point and end point should be set in a position which away from the truck 5 meters, and the third point should at the center position. Then digs 0.4 meters and samples the sub-sample. That is the manual coal sample method. Workers need to get the sample by the drill. This sampling method is not the suitable method because the coal samples are influenced by the human factor. It is the outdated sampling method.

Coal auger sampling method

mechanical coal sampling method

TOP SAMPLER provides the mechanical coal sampling system for coal trucks. This coal sampling process is automatic. The PLC control system will choose the sampling points automatically and randomly after the coal trucks enter the sampling zone. And the sampling point’s position will be changed with the different coal trucks.

Besides, the mechanical coal sampling collector is an auger sampler. The auger sampler has two main advantages. Firstly, the auger sampler is good at sampling in any depth. On another hand, the auger sampler has the crush, division and incision functions so it is suited for continuous work and work in winter.

Of course, this TOP SAMPLER mechanical coal sampling system is also used for the coal railcar (wagon). And there are crane type coal sampling system and door type coal sampling system for you to choose.

Conveyor belt sampling method

moving coal conveyor belt

For the moving coal conveyor belt, there are the cross belt samplers to get the sample directly. The sampling method for the moving coal stream is different with sampling method for the coal trucks or the coal railcar. The cross belt sampling system has two main types that are head belt sampler and central belt sampler.

head belt coal sampler & central belt sampler

Head belt sampling system

The head belt sampler system working process is simple: the sample collector installed in the conveyor belt the sample collector will rotate in a certain interval time to collect the primary coal sample increment from the falling coal material. Then the primary sample increment will send to the sample feeder through the coal chute, the sample feeder will send the coal primary increment to the sample crusher, we will acquire the sub-sample. Then the crushed-sample will be divided by the sample divider, and the final sample will be collected into the sample bottle and the redundant coal will back to the conveyor belt.

Central belt sampling system

The central belt sampler is installed on the center of the conveyor belt. The sample collector will sample the primary increment from the horizontal or slant coal conveyor belt. The typical central cross belt sampling system is a 2-stage sampling system which contains rotary sampler, sample feeder, sampler hammer crusher, and residue returns system. The central belt sampling system working process is different with the head belt sampling system: the central rotary sampler will rotate in a certain interval time to collect sample increment, and the coal sample increment will send to the sample feeder by the coal chute. Then, crushing, dividing, after these coal sampling procedure, the final coal sample will put into the collection bottle, meanwhile the redundant coal will back to the coal conveyor belt through the residue returns system.

These two types cross belt sampling system is suited for the coal moving stream, and the coal sampling process is automatic, it is better to collect the representative sample. The interval time is set by the PLC controlled system, so this sampling system guarantees the sampling process is random, and the sample precision to the full extent.

Coal sample preparation method

Except for paying more attention to the coal sampling method, the sample preparation is also crucial for guaranteeing the sample representative.

For example, how to solve the coal briquette (granularity >150mm)? If the coal granularity is more than 150mm, we should not sample the coal and should calculate the percentage of coal briquette which granularity is larger than 150 mm, then calculate the weighted average according to coal briquettes calorific value.

The second issue, crushing the coal sample is better to use the closed-sample crusher. The essential reason is the high temperature will cause the coal sample evaporation of water. This situation is obvious, especially in the summer. In term of this issue, TOP SAMPLER pushes out the three types sample crushers that are hammer sample crusher, jaw sample crusher, and the roller sample crusher. You can choose the suitable machines.

So far, we have introduced some coal sampling methods and sample preparation methods. Meanwhile, we have listed some issues during the sampling process and give us responses. If you still have questions, you can contact us directly. If you are interested in our sampling machines, welcome to send the inquiry!