Pipe particulate systems

Conservation is a general concept widely used in chemical engineering systems analysis. Normally it relates to accounting for flows of heat, mass or momentum (mainly fluid flow) through control volumes within vessels and pipes. This leads to the formation of conservation equations, which, when coupled with the appropriate rate process (for heat, mass or momentum flux respectively), enables equipment (such as heat exchangers, absorbers and pipes etc.) to be sized and its performance in operation predicted. In analysing crystallization and other particulate systems, however, a further conservation equation is... 

The University of California field stations have dealt with dilute pesticide waste disposal on an experimental basis by using lined soil evaporation beds. The beds typically are 20 x 40 x 3 ft pits lined with a butyl rubber membrane and back filled with 12 to 18 Inches of sandy loam soli. Figure 1 Is a cross secton of such a bed. Used containers and spray equipment are washed on an adjacent concrete slab the wastewater drains Into a sedimentation box for trapping particulates, followed by a distribution box In the bed. From the distribution box, the dilute pesticide solutions run underneath the soli surface through leach lines made of 4 Inch perforated PVC pipe. The system Is designed so that water moves up through the soli by capillary action and evaporates off the surface. 

In the following it is demonstrated how heat and mass transfer correlations for pipe flow may be transferred to particulate systems. In Fig. 4.3-2 a particulate system with the particle diameter and the overflown length L = is illustrated. The following is about a fixed or a fluidized bed, through which a fluid flows at volume flux v. ... 

The heat and mass transfer correlations for pipe flow can be applied for particulate systems, if the ratio d / L ) and a corresponding parameter for pipe flow are known (Schliinder 1972 Krischer and Kast 1978 Kast et al. 1974). 

Figure 4.3-3 illustrates this diagram for parameter allocation, which was created on the basis of numerous diying experiments. A particle s ratio mass transfer for pipe flow can also be used for particulate systems. If the volume fractions for the continuous and the dispersed phase are known, the ratio d / L ) can be calculated and in addition the ratio diameter by length can be determined using Fig. 4.3-3. 

Recently, dry wire-pipe ESPs are being cleaned acoustically with sonic horns (Flynn, 1999). The horns, typically cast metal horn bells, are usually powered by compressed air, and acoustic vibration is introduced by a vibrating metal plate that periodically interrupts the airflow (AWMA, 1992). As with a rapping system, the collected particulate slides downward into the hopper. The hopper is evacuated periodically, as it becomes full. Dust is removed through a valve into a dust-handling system, such as a pneumatic conveyor, and is then disposed of in an appropriate marmer. 

Goodfellow, H. D., et al. Hood System Design for Capture of Process Fugitive Particulate Emissions. Heatmg/Piping/Air Conditioning 58 (February 1986) no. 2, pp. 47-54. 

Seawater systems should be designed to avoid excessive water velocities, turbulence, aeration, particulates in suspension, rapid changes in piping section and direction. Likewise, extended periods of shutdown should also be avoided since stagnation of contained seawater, will result in bacterial activity and HjS production with consequential and perhaps serious corrosion and health and safety problems. 

Large quantities of particles are handled on the industrial scale, and it is frequently necessary to define the system as a whole. Thus, in place of particle size, it is necessary to know the distribution of particle sizes in the mixture and to be able to define a mean size which in some way represents the behaviour of the particulate mass as a whole. Important operations relating to systems of particles include storage in hoppers, flow through orifices and pipes, and metering of flows. It is frequently necessary to reduce the size of particles, or alternatively to form them into aggregates or sinters. Sometimes it may be necessary to mix two or more solids, and there may be a requirement to separate a mixture into its components or according to the sizes of the particles. 

Fio. 1. An example of a future integrated soot-NOx emission control system. DPF stands for diesel particulate filter. Sensory inputs of temperature (7), pressure (/ ), pressure drop (AP), soot and NOx concentration will be required along the exhaust pipe. 

It takes a lot more than just connecting an IR instrument to a pipe to make the instrument into a process analyzer. The system not only has to be constructed correctly and be capable of flawless operation 24 hours a day, but it also has to be packaged correctly, and be able to access the stream correctly and without any interference from process-related disturbances such as bubbles, water, particulates, etc. Finally, the data acquired from the instrument has to be collected and converted into a meaningful form and then transmitted to the process computer, where the information is used to assess the quality of the product and to report any deviations in the production. Beyond that point, the process computer, typically not the process analyzer, handles any decisions and control issues. There are a few exceptions where robotics are integrated with the analyzer, and good vs. bad product quality are assessed at the point of measurement. The use of... 

The pretreatments, described above, that deliver a particulate-free stream at 38 °C to the amine system provide a ready-made feed for processing via membrane modules. This feed can be used with simple and efficient membranes, new structured sorbents, membrane + structured sorbent hybrid systems or more advanced super H2 selective membranes. These membrane systems can simplify and condense the flow sheet in Figure 7.10, thereby enabling a more compact plant with less piping and associated maintenance concerns. 

---