Economic investigation on the use of internal coating for natural gas trunk-lines

Abstract

Natural gas transmission through pipeline is the most common method for high capacity gas transmission especially when LNG technology is impossible or uneconomical. These systems are too cost intensive mainly due to fuel consumption of compressor stations. To cope with this problem, internally coated pipeline is considered as an effective approach. A mathematical model was developed in previous study and a visual program was compiled to reach optimum design of natural gas trunk-lines. Effect of different parameters such as pressure, diameter, and material grade can be investigated by developed model. This paper aims to study the effect of surface roughness from economic viewpoint. Results show that internal coating has an insignificant effect on pipeline Life Cycle Cost while it has a considerable decreasing effect on pressure drop and consequently fuel consumption cost. This study shows a coated pipeline is not ever profitable. Internal coating is disadvantageous before breakeven flow rate and breakeven point is a function of other operating conditions. The profitability will increase by increasing flow rate especially at high flow rates. This behavior is a direct result of decrease in laminar sublayer's thickness. Therefore, a detailed economic research seems indispensable over the whole project's lifetime before making any decision about using of internal coating.