Selection of optimal design of drop collector for plants separating natural gas under high pressure

Abstract

Results of investigations of the hydrodynamics, flow structure, and operating efficiency of various designs of centrifugal separators with an ascending gas flow are presented. Technical data are compared for four models of centrifugal separators most frequently employed in industry, and recommendations are given for selection of optimal design. In many branches of industry, various forms of interaction between gaseous and liquid flows are the basis of production processes: absorption, desorption, evaporation, condensation, fractionation, and the cleaning of dust, liquid aerosols, and harmful gaseous components from gases. Intensification of the processes, which is associated with an increase in flow velocities, will lead to increased loss of liquid due to its being carried away from the active zone and disturbance of production regimes, while removal of liquids from the finishing equipment to the atmosphere will result in loss of expensive products and corrosion of adjacent components and structures.In this connection, the refinement of drop collectors, and the development of principally new designs are urgent problems.Various designs of drop collectors are currently under development and in industrial service; centrifugal drop collectors, which are distinguished by high efficiency, reliability, and simplicity of design, occupy a special place among these collectors [1][2][3][4].As analysis of equations of motion of drops in a centrifugal-force field indicates, operating efficiency of the equipment diminishes, and the ratio of the liquid and gas densities increases with increasing pressure [4,5]. A significant reduction in limiting allowable loads with respect to liquid and gas occurs simultaneously [6,7].It is possible to compensate for these negative effects by increasing the centrifugal forces with an increase in either swirling of the flow (tangential velocity w τ ), or the average velocity of the flow w 0 when w τ = w τ /w 0 = const.The first alternate scheme is implemented by varying the design and geometric characteristics of the swirling device, and the second by creating direct-flow centrifugal elements with one-directional movement of the gas-liquid-film phases. For apparatus with an ascending direct flow of the phases, moreover, the direction of the film flow will vary from descending to ascending, and the trapped liquid is released through an end slot in the upper portion of the separating branch pipe.The first concept was adopted primarily for technical solutions implemented by the company Adsorbent-Tekhnologiya at the Astrakhan Gas Processing Plant [8], and the second primarily for type designs developed by the Central Design Bureau of Petroleum Machinery (CDBPM) for centrifugal separators for the oil and gas industry [2].