Using LNG cooling capacity for regasification at air separation plants

Today, improvement of air separation unit circuitry to reduce either the plant’s cost or the specific energy cost of producing a unit of product is an urgent task. In addition, the issue of the possible use of LNG’s cooling potential for its regasification is becoming increasingly relevant. To study the possible combination of regasification and air separation processes and to determine the estimated dependencies to conclude on the effectiveness of such solution compared to the conventional air separation circuit. Hysys-14 software environment was used to model three air separation circuits with different options for actuating the LNG flow. We specified the relationships between nitrogen sweep efficiency and specific energy costs on the pressure in the cycle. The calculations showed that the energy costs of nitrogen are lower by an average of 46.6%, 27.2%, and 62.4%, respectively, for the first, second, and third circuits compared to the conventional air separation circuit with a pressure reducing valve and the sweep efficiency is higher by an average of 116%, 83%, and 166%, respectively. The study showed that the use of LNG cooling capacity in the air separation unit’s process flow can significantly increase the sweep efficiency, reduce specific energy costs per unit of product, and reduce the cost of the plant. The paper discusses the advantages and disadvantages of each circuit and suggests possible applications of the obtained results.