ENRICHMENT OF LEAN NATURAL GAS BY PSA PROCESS

Abstract

Vast amounts of lean natural gas reserves are located through out the world. In India these reserves are located at Ghotaru (Rajasthan). The calorific value of this gas is around 1700 kcal. per m3 at STP. And its average composition by volume is N, = 72 %, CH4 = 18 %, CO2 = 9%, Higher hydrocarbon = 0. 9 % and He = 0. 1%. Such a lean gas is not combustible by itself. Hence it can be used only by increasing the combustible content either by mixing it with higher calorific value gas or enriching its combustibles by removal of non-combustibles such as N, and CO2. Even if gas is enriched by mixing it with high calorific value gas, the volume of product of combustion shall be very high and hence a lot of energy shall be lost in flue gases. Further the transportation cost of gas shall be high because of the transportation of non-combustibles along with combustibles. To make this gas of pipeline quality, it is desirable to remove non-combustibles.. Non-combustibles can be removed from this gas either by cryogenic technique or pressure swing adsorption. (PSA). Of these, cryogenic technique is very costly and may not be commercially viable. Hence, it is considered proper to employ Pressure Swing Adsorption technique for the enrichment. Present work concerns the technical viability of adoption of PSA for enrichment in combustibles of this gas. This work is reported in five chapters. First chapter introduces various gas separation processes . It also gives the details of pressure swing adsorption process and a brief literature review of the work done. Second chapter deals with the thermodynamic treatment of the process. In this chapter equations are derived for binary and ternary systems. Chapter III concerns the material and equipment requirements and the experimental procedure adopted . Chapter IV deals with the results of present investigations. In this chapter it has been concluded that it is technically possible on commercial scale to enrich Ghotaru field gas to pipe line quality. In chapter V conclusions and the scope for future work is indicated..