With ageing of the equipments, the efficiency of existing plant decreases with time. In LPG (Liquefied Petroleum Gas) plant, decreased efficiency is demonstrated through reduced products yield or less throughput. However, often there exists some opportunities to address this problem by minimizing pressure drop across piping and control valves which facilitates higher recovery of heavier hydrocarbons (C 3 + components) from the rich gas for production of VAP (Value Added Products) such as LPG and Naphtha.

In present case study described in this paper, one of the opportunities was identified and recommended for improving efficiency of the existing LPG-I & LPG-II plants in terms of improved throughput and also effectively capturing the C 3+ heavier hydrocarbons from the rich feed gas by suitable debottlenecking. The combined processing capacity of these plants is 11.3 MMSCMD. The outlet lean gas as second stage vapor (SSV) from LPG-II is routed through an 18" header which joins the lean gas of SSV of LPG-I and combined SSV is routed downstream through a 20" header for further processing. Pressure drop issue in the combined header was identified & addressed in the present case study through suitable modifications in the pipe sizing.

Thus the detailed analysis of the existing system provided the scope for further improvement through a cost effective scheme with CAPEX of INR 3.01 Crores (0.5 Million USD), enabling LPG plants to operate at higher pressure resulting in increased throughput of 12 MMSMCD. The equivalent gain in value added products is around 173 TPD. The estimated pay back period is around 15 days. This case study demonstrates the hidden opportunities in an existing LPG plant for valorization of natural gas liquids from rich gas which resulted in additional LPG and Naphtha production.

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