A Commercial Scale Demostration of HEIGE for Bulk CO2.
HIEGE is a rotating mass transfer apparatus in which centrifugal force is used to intensify mass transfer this paper describes a joint program by Chevron, Statoil and Glitsch involving the installation, operating experience and performance of a prototype HIEGE at Chevron?s Judge Digby Gas Treating Plant near Baton Rouge, Louisiana. The HIEGE operated at 1000psig and processed up to 20 MMSCFD of gas for dehydration and for bulk CO2 removal. Because the absorption of CO2 by amines is often reaction rate controlled it was thought that the short residence times employed within the HIEGE may be insufficient to achieve adequate CO2 removal. This proved not to be the case.
In the paper we shall
briefly describe the HIGEE operating principles
describe the specific machine and its installation at Judge Digby
outline operating results for C02 removal and gas drying; - and finally,
outline comparisons of HIGEE and more conventional equipment.
The name HIEGE was coined to describe a proprietary patented mass transfer device because it employs a high gravitational (or centrifugal) force. The principles of operations of HIEGE have been described in a number of papers, but for the sake of completeness a brief description is included here.
A simple sketch is shown in Fig. 1.
HIEGE comprises a rotor containing the packing arranged as a toroid and a stationary casing.
The packing is a reticulated material (usually metal), which is characterized by both a large surface area per unit volume and a high voltage. Typically specific areas of 750 ft2/ ft3 and voltages in excess of 90% are employed.
Two sets of seals are incorporated; one set of shaft seals between the rotating shaft and the casing. The other between the rotor and outlet duct to prevent gas bypassing the rotating packing.
Gas enters via a nozzle in the casing and is forced through the rotating annulus of packing. There it comes into intimate contact with the scrubbing liquid which, having been distributed at the " eye" of the packing annulus, is forced outward by the centrifugal force. Treated gas leaves from the center of the machine while the loaded solution impinges on the casing walls and is drained from the casing.
At quite modest speeds (e.g. 500-1200rpm) " g" forces 100 to 1000 times atmospheric gravity are created. The resulting high shear forces produce very thin liquid films, rapidly renewed surfaces. And substantial turbulence such that extremely efficient mass transfer takes place. As in conventional mass transfer equipment, good distribution of both gas and liquid phases is of paramount importance in achieving optimum performance.
Design and operating parameters are discussed below as they affect:
Fig. 2 shows the familiar Sherwood flooding correlation. It will be seen that the ordinate term contains " g". In the case of HIEGE " g" is equivalent to w2r where w = rotational speed (radians/sec) and r = radius of rotor/packing.