Proposal of a Pneumatic Transport System in Aspiration based on Steam Jet Ejector

Pneumatic transport is a well-known and widely applied system for transporting materials in dust or grain conditions. In the last years, no improvements have been done regarding pneumatic transport systems, for which the design main characteristics have remained substantially unchanged: a blower placed either upstream (in pressurized plants) or downstream (in depressurized plants) of the silos containing the material generates the motion of the same, while a separator opportunely designed (often a cyclone) provides the separation between the air stream and the material in correspondence of the discharge point. In this paper, an improvement to the aspiration pneumatic system is proposed. The blower is substituted by a steam jet ejector placed immediately downstream of the air-material separator and filter. Feeding the ejector inlet with steam having the opportune pressure and flow-rate, the blower can be eliminated. The ejector outlet port, which is crossed by a mixture of steam and air, needs to be followed by a condenser to allow the recycling of the water used for generating the steam, and by an air extractor to exhaust the air employed in the transport. In the paper the feasibility of the plant is discussed together with its advantages compared to the classical solution providing blowers as material prime movers. One particular advantage is the lack of moving parts, which improves the plant reliability. Another advantage is the possibility to integrate the system with the steam produced by a steam turbine cycle and the possibility to employ the plant in modular stations, in order to increase the transport distance. Moreover, a comparative analysis with the classical solution is carried out in terms of economical feasibility.