Techniques for control of splitting ratios of particulate materials at bifurcations in pneumatic conveying pipelines

Abstract

In this paper the negative effect on the efficiency of coal-fired power generating stations, caused by unequal split ratios of pulverized fuel in pipeline branches downstream from bifurcations, is identified. Five active techniques for controlling split ratios have been developed and tested on a test-scale rig. Three of the five techniques were deemed to have potential for retrofitting into existing power generating stations and have been tested in detail on a large pilot-scale rig. The observations and the ensuing conclusions are presented.

Investigation of nonuniformity in a liquid–solid fluidized bed with identical parallel channels

“…The system was inherently unstable and experienced serious problems. Similar phenomena have occurred in PF‐fired boilers where a significant contributor to the inefficiency of PF‐fired boilers can be unequal fuel distribution to the burners 8. The pneumatic conveying pipeline that carries the PF from a mill to the furnace typically bifurcates two or three times to feed four or eight burners.…”

“…Maldistribution can negatively affect industrial equipment, e.g., by causing decreased cyclone capture efficiency,3, 8 differential erosion, differential fouling and more frequent shutdowns. For example, early fluidized bed reactors for the production of ethylene oxide and hydrocarbon synthesis featured multiple open vertical heat transfer tubes of equal length and diameter through which the fluidized suspension was intended to pass uniformly.…”

“…Few solutions are available to solve these maldistribution problems. Holmes et al8 suggested five active techniques to control the split ratios, involving back pressure, flow diversion, and an active riffle box. By opening communication between adjacent fluidization channels, Grace et al10 solved the problem of maldistribution, which plagued earlier geometries of fluidized bed membrane reactors where parallel vertical chambers of equal dimensions were isolated from each other over their entire height.…”

Gas‐solid flow distribution through identical vertical passages: Modeling and stability analysis

“…This is a major problem related to distribution of pulverized fuel through large parallel coalfired boilers. [14][15]22 Also numerical studies by Schneider et al 13 showed that upstream nonuniformities can play a significant role in flow distribution through parallel pipes. In another study, Yue et al 12 reported maldistribution of gas-solids flow through identical multicyclones at the top exit of a CFB boiler.…”