Propane Pre-cooling Dual Nitrogen Expander Liquefaction Process And Dynamic Characteristic Research Of FLNG

The FLNG (also known as FPSO-LNG) and FLPG (also known as FPSO-LPG) wereproposed in the marine engineering sector in recent years, setting the liquefaction, storage,load and unload and transportation of offshore gas/liquefied petroleum as a whole. Theparameters of the raw natural gas will always change in the actual operation. In the designstage, it is basis on steady-state conditions. But process parameters constant fluctuations inthe actual production and steady-state full load design can not describe the process accuratelywhen the device is in the start, parking, accident and external diaturbance conditions.Therefore, the dynamic simulation is more instructive to the actual production.In this paper, the propane pre-cooling dual nitrogen expander natural gas liquefactionprocess was designed as for the characteristics of the target gas field in the deep sea. It wasappropriate for offshore production environment. It included the deacidification anddehydration unit, heavy hydrocarbon removal unit and the natural gas liquefaction unit. Thispaper proposed different heavy hydrocarbon removal processes and choosed the best oneaccording to the floating production environment and the economics. This paper did thesensitivity analysis of the inlet parameters of the feed gas, analyzing the adaptability of theprocess.This paper established the dynamic model of the target gas field natural gas liquefactionprocess on the basis of the steady-state model, including the propane pre-cooling unit and thedual nitrogen expansion refrigeration unit. It analysed the dynamic reponse characteristics ofthe key parameters under different disturbing conditions, including the pressure, temperature,flow rate and composition of feed gas, cooling temperature of the reftigerant and the compressor power.This paper established the steady-state model of the pilot plant, a simplified steadymodel of the target gas field natural gas liquefaction process. The parameters of the feed gaswere changed. It established the dynamic model on the basis of the steady-state model,analyzing the dynamic reponse characteristics under the disturbance. It made a comparativeanalysis of the processes of the pilot plant and the target gas field, summarizing the differenceand the contact between the two processes.