|1. Pressure dense
|2. Vacuum dense
Pressure dense phase will require a specifically designed sender hopper in order to withstand pressures from 1 to 3-4 barg in most cases. Such a tank is called a pressure tank. It features a compressed air inlet at the top and another one after its discharge valve. It should also be equipped with a pressure safety valve in order to avoid any uncontrolled pressure increase. A degassing system with a filter must also be installed.
The receiver must be equipped with a filter and may also be equipped with a star valve if necessary. If the receiver is big emough and designed to work at atmospheric pressure, such equipment may not even be necessary.
As part of the instrumentation, pressure sensors in the tank, at the beginning of the pipe and at reception will be key since the whole system will be driven depending on the pressures. Level sensors in the sender hopper in order to detect the end of filling and the end of discharge are necessary while a level sensor at the receiver should be installed to avoid overfilling. Compressed air flowmeters are optional but constitute a good troubleshooting tool.
Figure 1 : Pressure dense phase typical process arrangement
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A vacuum dense phase system is quite similar to a lean phase setup except that a vacuum pump allowing to reach pressure <-900 mbarg should be installed.
The inlet of material is usually done through a sender hopper. No specific construction for the sender hopper is needed, which can be an advantage compared to pressure dense phase since the access is easier.
The receiver, on the contrary, must be designed for full vacuum, which means it must be reinforced and will account for some cost increase. It should be equipped with a star valve or with a butterly valve if the transport is in batch
A pressure sensor at the receiver and at the pump suction is necessary. The pump should be on frequency drive.
Figure 2 : Vacuum dense phase typical process arrangement