Standpipe function

H H(Gravitational acceleration Height of standpipe Function, defined graphically in Fig. 8.12 Zb Height of solids in standpipe Greek Symbols... 

The kick alert detects the free gas over the whole annulus length by comparing the pump noise in the standpipe to the pump noise picked up a few feet below the flowline. The phase shift is correlated to the annulus sonic velocity, itself a function of the free gas. 

Proper standpipe design is one of the most important factors in obtaining good circulation. The standpipe provides the necessary head pressure required to circulate the catalyst. A standpipe assembly is typically comprised of three major parts hopper, standpipe, and slide or plug valve. The function and design of each part is described below. 

Figure 6. Calculation of the dimensionless solids throughput V as a function of the aeration rate for sand of 0,15 mm diameter in a standpipe aerated about midway down and operated with a modest backpressure. Note the existence of two steady values of V for some ranges of Ua the dashed line represents an unstable portion of the curve. From Mountziaris [36],...

More attention was given to instability of operation. Generally, standpipes are devices used to convey particulate solids against an adverse gas pressure gradient with the aid of gravity. The standpipe must also function as a seal to prevent backflow of gas against the direction of motion of the particles. In certain circumstances, standpipes may malfunction, apparently undergoing a transition to a state in which there is much smaller pressure buildup within... 

The vertical moving bed has been used in many chemical processes as a nonfluidized standpipe or dipleg. The main function of the nonfluidized... 

The layout of the standpipe assembly Is a function of the working of a nuclear reactor and It Is not envisaged that this layout could be changed In any way purely to facilitate decommissioning of a PCRV. The standpipe region has to withstand the internal pressures of a PCRV and consequently Its structural depth has to be consistant with the required minimum structural thickness of the PCRV. 

To minimize end effects, spherically shaped containers were utilized in the experimental apparatus. These containers were of soft aluminum (2S), having an outer diameter of 5.375 in. and a wall thickness of 0.029 in. Each sphere was fitted with a standpipe welded into its top. Two types of experiments were performed. These were (1) the determination of frost formation rates and thicknesses as functions of time, and (2) the determination of liquid oxygen vaporization rates and subsequent heat transfer rates under varying ambient conditions of temperature, pressure and humidity. 

Knowlton and Hirsan (1978) established that the best position for the injection of the aeration gas is in the vertical leg (sometimes called the downcomer or standpipe) about 1.5 pipe diameters above the centreline of the horizontal leg. This is because gas is needed to reduce friction between the particles and the pip>e at the inside comer of the elbow, and if the gas is injected on or below the centreline, less is available to perform this function. This gas then streams along the top of the bed of powder lying in the horizontal leg carrying particles with it in a mode of transport that resembles dense phase pneumatic conve5ung. As the aeration gas flow is increased the depth of the flowing stream of powder increases and the mass flow rate of solids increases. Eventually the whole depth of powder may become active with the solids velocity increasing from bottom to top of the horizontal leg. 

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