SEPARATOR INLET

Abstract: A separator inlet for a separator in a process plant, for example a plant for processing a fluid consisting of oil, water and/or gas. The separator inlet is designed as a spiral channel (10) open at the top in a channel housing (4); the fluid flows in tangentially (at 5) and flows out through a central outlet (6) in the housing (4) downwards or the fluid flows through in the opposite direction. A funnel-shaped gas trap (12) may expediently be arranged in connection with the channel housing (4) on the outside of the channel housing (4) and extend from slightly below the outlet (6) of the housing (4) to above the surface of the fluid.

Description: Separator Inlet The present invention concerns an inlet for a separator (separator tank) in a process plant, for example a plant for processing a fluid consisting of oil, water and/or gas. The inlet arrangement in a separator in a process plant usually has several purposes: - to reduce the impulse to incoming fluid to avoid the inlet flow disturbing the steady flow conditions required in the separator; - to prevent sand or similar in the process flow being deposited in places where this is undesirable; - to prepare the process flow so that the conditions for good separation are optimal. In practice, impulse reduction is usually the guiding factor for the design of an inlet in a separator. A widely known such impulse reduction solution is based on the use of a flow interruption plate arranged just outside the separator inlet. The fluid flow meets the plate and is spread outwards and possibly backwards if the plate is curved. Another impulse reduction solution is based on the use of a U-shaped pipe in connection with the inlet to "return" the flow towards the separator wall. A third solution is based on the use of a T-pipe section in connection with the inlet to interrupt the fluid flow and steer it sideways. However, all these solutions create a greater or lesser degree of spray, agitation and disturbance to the surface of the fluid which mean that the conditions for good separation are not achieved or are poor. If the fluid supply flow consists of oil and water, large shear stresses, for example as a result of pressure loss across a valve or sudden changes of speed, can lead to the oil and/or water being turned into small drops and a so-called emulsion being formed. 2 In its simplest form, the emulsion is either of the type oil in water (oil drops in water) or water in oil (water drops in oil). Surfactants in the oil can stabilise the emulsion and make it difficult to separate the oil and water. Water in oil emulsions are considered to be more difficult to break down than oil in water emulsions. If the fluid supply flow contains free gas in addition to oil and water, shear stresses to which the fluid supply flow is exposed can lead to the formation of small gas bubbles which are mixed with the fluid phases. These gas bubbles can have an emulsion-stabilising effect like the surfactants in oil. The present invention represents an inlet to a separator in which the fluid inlet flow is not exposed to unnecessarily large shear stresses (plunging, sudden changes of speed) and in which free gas which may be present in the fluid supply flow is released before the fluid flow is exposed to shear stresses. Moreover, the present invention represents an inlet which produces steady flow conditions in the separator and prevents any sand or other particulate contaminants being deposited in places where this is undesirable. The present invention is characterised in that the separator inlet is designed as a spiral channel open at the top in a channel housing; the fluid flows in tangentially and flows out through a central outlet in the housing downwards. The dependent claims 2-3 indicate the advantageous features of the present invention. The present invention will be described in the following in further detail with reference to the attached drawings, where Fig. 1 shows a drawing of a separator inlet in accordance with the present invention arranged in a separator tank, Fig. 2 shows, in the form of a schematic diagram, an outline of the separator inlet, Fig. 3 shows a schematic diagram of the same inlet seen from above, 3 Fig. 4 shows a schematic diagram of the inlet shown in Fig. 2 during operation, i.e. filled with a fluid, for example oil/water containing gas. Fig. 1 shows, as stated, a separator inlet 1 in accordance with the present invention arranged in a separator tank 2. The separator is placed in connection with the surface of the fluid and the fluid is supplied to it from outside via a supply line 3. The separator inlet 1 comprises, as shown in Fig. 2 and Fig. 3, a separator housing 4 with channels open at the top which run from a tangentially located connection point 5 for the supply line 3 in spiral form to an outlet 6 which is arranged centrally in the housing 4. The housing 4 may expediently be made of a disc-shaped plate 7 with inward-sloping plates 8, 9 arranged on this disc 7 which run in spiral form and form walls in a channel 10. A circular, pipe-shaped part with openings 11 to the channel 10 may also expediently form the outlet 6 in the housing. The housing 4 may be equipped with a lid over the channel but any lid must be provided with openings for the evacuation of gas. In order to trap any gas bubbles which are released at the outlet 6 in the housing 4, it is preferable to arrange a funnel-shaped gas trap 12 which is connected to the housing via mounting pieces 13. The gas trap 12 is designed to extend slightly below the inlet 6 to just above the surface of the fluid outside the housing 4. The separator inlet works by the fluid being introduced to the channel 10 in the housing from the pipe 5 and flowing in spiral form through the channel 10 in the housing to the outlet 6 while releasing any gas. The fluid then flows downwards through the outlet 6 and any remaining gas will be trapped by the funnel-shaped trap 12 and conveyed to the surface. Alternatively, the flow can be in the opposite direction, i.e. the inflow can be via the central opening 6 from above and the outflow can be tangential via the opening 5, which will be immersed in the fluid in the separator. The housing may expediently be made by casting or of welded plates of a corrosion-resistant material, for example stainless steel. Example: Comparative tests were performed in a Plexiglas model of a separator in the scale 1 :4.5. Water, Exxol D80® and air were used for the three phases in the fluid which was supplied to a separator inlet in accordance with the present invention and to a well known separator inlet of the impulse type with two sets of plate packs in the water phase. The tests for the two separator types were performed under the following conditions: Water cut (percentage content of water) 60% Gas/fluid ratio (volume) 1.2 Mixing speed (inflow speed of fluid) 6 m/s Oil in water was measured with an IR instrument of make Horiba®. The following results were obtained: Oil in water at Oil in water at inlet of separator outlet of separator Widely known impulse type inlet 110-140 ppm 400-500 ppm Inlet in accordance with the present invention 100-150 ppm 220-300 ppm As the results show, the separator inlet in accordance with the present invention produces a much lower content of oil in water (better water quality) at the separator outlet than the well known inlet.

Claims: 5 Claims 1. A separator inlet for a separator in a process plant, for example a plant for processing a fluid including oil, water and/or gas, characterised in that the separator inlet is designed as a spiral channel (10) open at the top in a channel housing (4); the fluid flows in tangentially (at 5) and flows out through a central outlet (6) in the housing (4) downwards or the fluid flows through in the opposite direction. 2. A separator inlet in accordance with claim 1 , characterised in that a funnel-shaped gas trap (12) is arranged in connection with the channel housing (4) on the outside of the channel housing (4) and extends from slightly below the outlet (6) of the housing (4) to above the surface of the fluid. 3. A separator inlet in accordance with claim 1 , characterised in that the channel housing (4) comprises a disc-shaped plate (7) with upright and preferably inward-sloping plates (8, 5) arranged on this disc (7) which form the walls of the channel (10) in the housing and that the plates are connected with a pipe-shaped part (14) with openings (11) which forms the outlet (6) in the housing.

Inventors: LINGELEM MORTEN, NILSEN PAAL JAHRE, STRAND BAARD, LINGELEM, MORTEN, NILSEN, PAAL, JAHRE, STRAND, BAARD
Applicants: LINGELEM MORTEN, NILSEN PAAL JAHRE, NORSK HYDRO AS, STRAND BAARD, LINGELEM, MORTEN, NILSEN, PAAL, JAHRE, NORSK HYDRO ASA, STRAND, BAARD
Application year: 1999
Main classification: B04C5
IPC codes: B01D17, B01D19, B04C5, E21B43