Rapeseed System
Chris,
At a pickup velocity of 28 m/s the solids loading at 12 t/h is approximately 1.59, which is on the low side even for a system 240 meters in length. Even at the desired 20 t/h the solids loading would rise to a modest 2.65. Nothing wrong here.
This system is underperforming because it must accommodate the 30 meter sloped (upward) section of pipe. In this section, despite the excess velocity, the rapeseed tends to salt out of the conveying stream and accumulate on the bottom of the pipe. The accumulation process continues until the pipe is blocked.
The only practical solution here is to repipe the system to eliminate the sloped section. Otherwise the system must be modified to accommodate a considerably higher pressure, i.e. a 3.5 bar compressor and rotary valve. I do not consider this to be a practical alternative.
Dennis Hauch, PE ■
Pneumatic conveying of rapeseed
I have a pressure pneumatic line where I want to convey rapeseed (canola) with a particle size of around 2.5mm. The bulk density is about 650kg/m3. I want to transport 20t/h over a distance of 240m. The pipeline was existing with a diameter of 206mm.
I selected a blower to produce 28m/s (the saltation velocity is around 21m/s) in the line with a total pressure delivery of 40kPa.
The outlet is about 10m higher than the inlet and the last 30m of the pipe is running at an angle upwards (unfortunately rather difficult to change to horisontal and vertical lines). The outlet itself is into a silo and fairly open with low pressure drop.
The result is that the system does not convey more than 12t/h continuously.
The infeed is from a tipping scale via a rotary valve.
Initially the capacity is OK, but after a few hours the pipe starts to block and eventually the safety valve blows.
Is there anyone with experience with canola that can shed light on my problem? ■