How thick are generally the high-pressure water-coal slurry pipelines for 600,000 tons of methanol per day using coal as feedstock?
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Generally, the velocity of water-coal slurry in pipelines should be between 0.6 and 1.5 m/s, but what is the actual flow velocity during operation? I have seen some process packages for 600,000-ton methanol projects; some use 8-inch pipes while others use 6-inch pipes. The gasification furnaces are all configured as three in operation and one as backup, and the processing capacity is more or less the same. Why is there such a big difference in pipe diameter?
The slurry pipeline in our plant is DN200, which is 8”. It depends on what aspects the design institute takes into consideration.
8”, 6” is too small; a flow rate of no more than 0.8 m/s is optimal
We are 5 inches, with all four nozzles being 5 inches as well.
The normal flow rate does not exceed 0.8 m/s; then, at half-load operation, wouldn’t the flow rate be 0.4 m/s? Such a low flow rate will cause the water in the coal slurry to separate and settle in layers
For coal slurry gasification technologies similar to Texaco’s, 8” pipes are commonly used for coal slurry conveyance.
We have a furnace with a capacity of 40 kilograms, and the coal slurry pipeline is DN150; I’m not sure what that corresponds to in inches! It seems our pipes are quite thin! However, with a smaller pipe diameter, the flow rate should be higher, resulting in less sedimentation of coal slurry inside the pipe. It seems pretty good too, right?
It depends on the design philosophy. The advantage of using pipes with a larger diameter is that the flow rate is lower, the wear rate of the pipes is reduced, their service life is longer, they are less prone to blockage, and the operation of the coal slurry is more stable. However, the downside is that the cost is relatively high, and a large amount of slurry is wasted each time the system is started up or shut down (the startup procedure includes a timing period during which the pipes are filled with slurry; the larger the pipe diameter, the longer this timing period, and thus the longer it takes to complete the startup procedure). The coal slurry remaining in the pipes when parking must generally be discharged and discarded; the larger the pipe diameter, the more coal slurry is stored inside it). The advantage of using pipes with a small diameter is that the cost of such pipes is relatively low, and less coal slurry is wasted each time the system is started or stopped. However, the downside is that the pipes wear out more quickly, especially at the bends; the pipes are prone to blockage, and the stability of the coal slurry flow is relatively poor. To put it simply, using 8-inch pipes is a lifestyle for the wealthy – those who have no financial worries and prioritize quality. Using 6-inch pipes is the lifestyle of those who are trapped in mortgage burdens; one has to save wherever possible and be very frugal.