Product
The Venturie Cargo System for Reclaiming of Hydrocarbon Losses
In transit
The venturi reabsorption unit of the Venturie Cargo System consists of a pressure controlled pump, feeding oil to a unit with two venturis. Because of the venturi suction, VOC, H2S and inert gases (IG) are drawn from the common IG line. The venturi unit is a gas compressor with no moving parts, designed to generate a bubble size optimal for rapid absorption. Released near the tank bottom, gases are kept dissolved by the pressure head there. To keep a crude oil tanker emission free in the loaded voyage, the process operates up to 1-2 hours per day. The Venturie Cargo System works on all tanker sizes, and offers a payback time of less than one year. We guarantee to keep ships free of all in-transit venting.
During loading
Tank pressure is kept constant during loading by the mast riser valve, controlled with the ship’s pressure transmitter on the inert gas line. The setpoint should be kept close to that of the ship’s p/v valves, to maximize savings. There is no venting until the vessel pressure reaches the setpoint. Both retrofits and newbuilds require minimal modification of existing valve arrangements, and offer better onboard working conditions.
How it works
While at sea, the Venturie process’ pump is started every time the pressure approaches the roof of the comfort zone. Oil from e.g. an aft cargo tank circulates through a venturi unit, where ullage gases are mixed with oil and then deposited and condensed at the tank bottom.
Venturie recommend that the pumps should be started at 1200mm WG and operate until the pressure is down to 900mm. This takes 20 – 60 minutes, depending on the ship size. At lower fill%, operation times are longer. The process keeps the ship emission free during the loaded voyage.
During loading, we control the mast riser valve position, using the ship’s existing IG line pressure transmitter. The backpressure keeps the dissolved gases ethane through heptane from leaving the oil. This graph shows that 1200mm WG pressure can reduce vapour growth by 50% (Sim by Flow Dynamics). To the right, Venturie’s measurements on Vela’s VLCC Gemini Star.
Operation
A touch panel in the cargo control room is the crew’s user interface. For backpressure loading, there will also be a switch, changing from the original IG cabinet’s valve open/close control to the Venturie control panel. Automatic pressure control and manual valve position control are the two modes of operation during loading.
The touch panel also controls automatic or manual start/stop of the venturi pump after loading.
Installation
If the ship has a remotely controlled riser valve, only the pressure controlling software is needed, no further hydraulics. Pending the ship’s docking time, backpressure control can then normally be installed without any hot work.
During docking, a standard crude oil pump is placed in the pump room, with bulkhead transmission to the 100kW motor in the Engine Room. Suction should be at least 5-7m under 98% fill level. 80-100m of DN250 piping connects the tank, pump and venturi unit. The latter sits on an aft cargo tank, with a vertical drop pipe to just above the tank bottom, and on the opposite tank side of the suction pipe.
It is recommended that the customer selects to operate the pump’s isolation valves from CCR instead of hand operation. Actuators, two solenoid valves and hydraulic piping are required.
The PLCs and control hardware is placed in the console or in the valve room, the pump motor starter in the MCC or in the Engine Room. A soft starter should be used. If the start of a second generator should be prevented completely, starting with frequency control is recommended.