The research facility at the University of Manchester in the Morton Laboratory is a full scale replica of an industrial sized natural circulation thermosyphon reboiler, which comprises 50 tubes of 3 m length and 25.4 mm OD. The facility is operated under vacuum. Water is used as the process fluid and condensing steam is the heating source. Experimental datasets were obtained for the reboiler and have been presented in the form of profile plots of feed rate, fluid recirculation, recirculation ratio and vapour quality. The data elucidate the effect of pressure [0.1 to 1.0 bar] and heat duties [78 to 930 kW] on the performance of the reboiler. Three distinct modes of operation have been observed. Mode one is defined as a flow-induced instability or geysering (low heat duty) and exists below a definite transitional point that is independent of process pressure. Mode two is a region of stable operation that occurs above the threshold of the flow-induced instability, while mode three, which is defined as the heat-induced instability (density-wave instability), is pressure dependent obtained at high duties and is characterised by violent oscillations. These instability thresholds represent the lower and upper limits of operation of the reboiler. The region of stable operation is enveloped between the two limits and is very dependent on process pressure as it progressively becomes smaller as the vacuum becomes lower. These studies led to unique experimental observations, which revealed the existence of intermittent reversed flow in the entire loop. The use of throttling in the heat-induced unstable region to return to stable operation tends to be over a narrow range, outside of which the sole way to regain stability is to lower the heat load or increase the process pressure. In the region of flow-induced instability, throttling the fluid at the inlet is useless and actually makes the situation worse. These instabilities are alleviated by increasing the heat load.

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Maximising recovery of hydrocarbons from oil and gas fields represents responsible asset management and is extremely valuable both to the operator and the host country. Doing this successfully involves a complex combination of technical, commercial, organizational and human factors. This was addressed by developing the Reservoir Technical Limits (RTL™) process; the process and its application to oil fields was described in a 2009 SPE paper (109555). The present paper describes subsequent progress in developing RTL™, including a description of a new gas efficiency factor framework for use in volumetric and aquifer-drive reservoirs.

Vapour generation through boiling is one of the most ubiquitous industrial processes. Vertical thermosyphon reboilers are frequently used to generate vapour at the base of distillation columns. Present design methods have the major emphasis on the process side (boiling). The heating of the vertical boiler is decoupled from the system. Additionally, most academic research has considered a single tube flow arrangement with controlled and uniform electrical heating. However, many applications in distillation are now using sub-atmospheric pressure operation (higher thermodynamic efficiency, reduced energy consumption, prevents thermal degradation, cheaper materials of construction and safe operation). The literature does not contain many references to this mode of operation and existing design techniques do no adequately cover sub-atmospheric pressure operation. The thermosyphon reboiler research facility at the University of Manchester in the Morton Laboratory comprises 50 tubes of 3 m thermal lengths (19.86 mm ID) and 3 segmental baffles (TEMA E type shell and TEMA A type header) with steam condensing on the shell side, 2 large horizontal condensers with 106 and 196 tubes, both TEMA E type shells and B type headers. Vacuum is pulled on the process side and the shell side by means of two separate liquid ring pumps. The process fluid is water flowing in the tubes counter-current to the condensing steam in the shell side. The primary objective is to study the operation of the thermosyphon reboiler over the pressure range 0.1 bar -atmospheric. New additional instrumentation for temperature, pressure and flow measurements have been calibrated and installed. At the present time, the equipment is fully instrumented, re-insulated and has been successfully commissioned. This paper describes the equipment in detail, its configuration, instrumentation (control, safety and scientific), modifications from the previous arrangement (Emerson DeltaV computer control software and data logger, new instrumentation) and the effect on errors in the mass and energy calculations. A brief reference will be made to the complications encountered during commissioning and the solutions adopted.