Twin vessel dense phase conveying is the solution when minimal height is available and when the product needs to be conveyed gently without any creation of fines.
A customer had issues with a belt conveyor that should transport the instant chocolate drink powder from production to a sieve placed right above the filling lines. The installed belt conveyor contaminated the powder with wear which was not acceptable. As all upstream equipment was already installed, a space of less than 1m below a discharge rotary valve was available.
A lean phase pneumatic conveying system with negative or positive pressure would have been possible. However, because the powder must be treated gently, minimising the creation of fines during the transport, a low velocity dense phase conveying system Gericke PulseFlow PTA with two vessels was selected. The two 20-litre pressure vessels were placed side by side and successfully fitted below the continuously discharging rotary valve. The chocolate powder was fed at a rate of 1.5t/h into one pressure vessel while the other vessel is conveying and alternating. This mode generated a continuous product transport.
In another project the client had an IBC and a metal detector system for unloading milk powder. The task was to convey the milk powder at a rate of 3t/h to receiving hoppers above the filling line and at the same time not to create fines. Therefore, the Gericke PulseFlow PTA dense phase conveying system operating at low velocities was chosen. Due to the height restriction of 1.5m this time, two 50-litre pressure vessels were selected.
Utilising twin vessels reduces the height requirement, compared to using single vessels in combination with intermediate buffer hoppers when there is a continuous process upstream. Twin vessels allow continuous operation. At the same time, the air consumption is reduced because smaller pipe diameters can be utilised compared to a single vessel system. For single vessel conveying, filling times have to be considered too. When the conveying has paused, and to achieve the same absolute instantaneous capacity during conveying, more time must be allocated, which requires larger pipe diameters and higher air consumptions.
