Coal analysis time
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I would like to ask my fellow students: how long does it take, from the moment a coal sample is collected until the analysis results are available, in the shortest possible time? We need at least 9 hours right now, but the results are available in just 2 hours. I really want to know if it’s possible to get the results in 2 hours.
If only moisture, ash, and volatile matter are to be analyzed, it can be done in 2 hours using a fully automatic industrial analyzer.
The samples crushed to 13 mm have their surface moisture removed using a microwave oven; they are then immediately crushed and reduced in size to 1 mm to form analysis samples. The calorimeter can be used to measure the heat of combustion, or the rapid ash method can be employed for industrial analysis, allowing reference results to be obtained within roughly 2 hours.
It depends on the method used; of course, a fully automatic industrial analyzer takes less time. If you use a muffle furnace or an oven, it will take longer, but 9 hours is a bit too long. With proper adjustment of the time, around 7 hours should be sufficient.
Reply to 3# xwtsq: How long is an appropriate drying time in a microwave oven?
This parameter needs to be determined by oneself based on the type of coal, its moisture content, and the model of the microwave oven. It is important to note that some coals contain metals, and some are flammable; therefore, safety is a key consideration.
We are analyzing the coal samples in the same way as the original poster – using muffle furnaces and ovens, here to learn*~~
If there are many samples, 2 hours is hardly enough
1. Two hours is the time required for industrial analysis methods; it should be sufficient. 2. If analyzed entirely using classical methods, it will take at least 28 hours. This is because the air-dried coal sample must be left to stand in the air for 24 hours before it can be ground to a particle size of less than 0.2 mm in order to analyze its ash content, volatile matter, internal moisture, lower heating value, and total sulfur content. Among these four, ashing takes the longest time – it takes over three hours from when it is placed in the muffle furnace to when it is removed and cooled to room temperature.
Reply to 9# wolf1147: Were your air-dried coal samples left in the air for a day? So for some units that use 50°C for 1 hour, is what’s being done related to the external moisture? Speaking while still alive, is what is obtained after a 50-degree drying titration time the coal sample on an air-dried basis? Some more coal samples have arrived; after weighing them at over 200 grams, they are dried at 105 degrees until a constant weight is reached, thereby determining the total moisture content. This value can be used as an auxiliary indicator for pricing coal. Do you think that’s acceptable?
Reply to 10# chenhaidong5758: Haha, I’m referring to the standard method – only energy monitoring stations and arbitration agencies use it. It’s completely unrealistic for users. We dry the received coal sample at 50°C for 1.5 hours and then prepare an air-dried coal sample; actually, this method yields pretty much the same result. The criteria for settlement depend on what the user and the supplier agree upon; as long as both parties are in agreement, it’s fine. As a joke, it’s even possible to use the size of the coal particles as the basis for settlement, as long as both sides are willing to that. However, for scientific calculation, I believe the factors to consider include moisture on a basis weight basis, lower calorific value, and total sulfur content. In addition, the values for ash, volatile matter, and moisture should be determined according to the design parameters of the coal utilization equipment.