Tuning plan for the particle size distribution of coal fed into a circulating fluidized bed boiler

This post was last edited by gjn1970 on 2016-1-19 at 10:13. It is certain that the particle size of coal fed into the furnace should be controlled between 0 and 10 mm; however, it is also crucial to ensure that the coal meets the required screening standards. It is necessary to prevent a situation where the coal particles are larger at both ends and smaller in the middle (in other words, an excessive amount of fine powder and large particles). Currently, the recommended proportions for coal particles used in circulating fluidized bed boilers in Europe are as follows: the proportion of particles smaller than 0.1 mm is less than 10%, those smaller than 1.0 mm are less than 60%, those smaller than 4.0 mm are less than 90%, and there are no particles larger than 10 mm. Below is the screening situation of a circulating fluidized bed boiler from Dongfang Boiler Co., Ltd.; it can serve as a reference. Sieve distribution table for Dongfang Boiler DG470/13.73—II1: Particle size (mm), Design coal type (%), Verification coal type (%)
0－0.053: 0.22, 0.13; 0.053－0.09: 0.73, 0.96; 0.09－0.18: 2.24, 4.83;
0.18－0.3: 6.94, 6.22; 0.3－0.56: 13.45, 8.87; 0.56－1: 9.87, 8.06;
1－2: 20.79, 17.85; 2－3.2: 18.04, 19.38; 3.2－9: 27.63, 33.32
Total: 100, 100

The question is, how can we achieve the coal particle size distribution required by the boiler factory in actual production? How is two-stage crushing achieved when raw coal arrives at the plant? For example: The coal is to be crushed in accordance with the requirements of the boiler factory, but the raw coal arriving at the plant is already in a fine form (without screening), accounting for 70% of the total; the remaining 30% consists of coal lumps with sizes ranging from 10 to 50 mm. How can experiments be used to ensure that the coal fed into the furnace meets the required particle size specifications? If the raw coal entering the plant does not meet the requirements for particle size distribution after crushing. How can we determine which type of raw coal can meet the particle size requirements in the most energy-efficient and cost-effective way?

Obviously, there is too much fine powder in the raw coal upon arrival, which is already a defect; this issue must be resolved first. It can be addressed by negotiating with the coal supplier or by switching to a different source of coal； Depending on the actual conditions, primary crushing can be carried out using a ring hammer coal crusher; the gap between the hammer heads and the crushing plates can be adjusted to control the particle size of the coal and facilitate screening. Additionally, the mesh size of the drum screen should be chosen appropriately – it is recommended to use a self-cleaning drum screen. If two-stage crushing is necessary, the first stage should use gear rollers while the second stage uses ring hammers. If the coal passing through the first drum screen meets the required standards, it should not be sent to the second stage of crushing to avoid over-refinement.

Thank you for the answer. I’ll start working on it after the New Year. It’s likely to be a time-consuming and difficult task; there are no shortcuts