THEORETICAL MODEL FOR THE POWER RECOVERY OPTIMIZATION IN NATURAL GAS DISTRIBUTION NETWORKS: COLOMBIAN CASE Lesme Antonio Corredor Martínez Universidad del Norte Km 5, Antigua Vía Puerto Colombia Barranquilla, Atlántico, Colombia lcorredo@uninorte.edu.co Diego Jesús Guillén Pérez Universidad del Norte Km 5, Antigua Vía Puerto Colombia Barranquilla, Atlántico, Colombia dguillen@uninorte.edu.co Luz Adriana Castellón Pineda Universidad del Norte Km 5, Antigua Vía Puerto Colombia Barranquilla, Atlántico, Colombia lcastellon@uninorte.edu.co David Antonio González Fernández Universidad del Norte Km 5, Antigua Vía Puerto Colombia Barranquilla, Atlántico, Colombia agonzalezd@egresado.uninorte.edu.co Alberto Mario Palacio Bastos Universidad del Norte Km 5, Antigua Vía Puerto Colombia Barranquilla, Atlántico, Colombia abastos@egresado.uninorte.edu.co ABSTRACT LNG production used in passenger transport systems obtained trough natural gas expansion in city networks is a novel process and it has been demonstrated its small energy consumption. This process has made in two stages: first one consist of a pressure reduction and the second one in a cryogenic liquefaction. This paper is focused in the first stage and in a second paper the author will present the simulation result of LNG production optimization for urban transportation systems. This research has been supported by Colombian Science and Technology National Agency (Colciencias, in Spanish) and the company Terpel. As before mention, in natural gas distribution networks, this fuel is transported at high pressures through long length pipelines between the source and final consumers. In every place of consumption or at passing into a lower pressure pipeline the gas pressure must be reduced. Commonly, high pressure is achieved by using a number of compressors, each one attached to a natural gas combustion turbine, consuming energy, and gas pressure reduction is accomplished in mechanical letdown-valves, where an isenthalpic expansion takes place without any energy production. A few amount of the energy consumed could be recovered taking advantage of the enthalpy drop in delivery sites or in pressure reduction stations by the introduction of expander–generator units for power generation. However, this energy that could be recovered is limited to the pressure ratio and the gas mass flow magnitudes at each site, being both variable parameters depending on seasonal, daily and hourly demand fluctuations. For that reason, the optimization model proposed helps in the selection and location of the expander-generator units to recover the potential energy available and produce clean electricity, minimizing the investment payback period, based on the historical demand and operational restrictions of the Colombian natural gas distribution network. KEYWORDS Natural gas, distribution network, pressure reduction, turboexpander, Colombia. 1. INTRODUCTION Expander’s application to droop pressure in natural gas supply networks, without affecting the daily operation [1- 6] has a great acceptance between the researches that are focus on power recovery from any available source. Heybatian et al. [1], evaluated a City Gate Station in Shahrekord city, Iran, with the installation of a expader- generator a maximum of 1,8 MW could be recovered, with an annual benefit of USD $463.000.oo and a payback period of 3 years. At the turbo-expanders application the energy recovery is proportional to the variable expansion ratio and the gas flow rate through the system however some technical and economical limitations should be considered: (i) the gas composition and thermodynamic state; (ii) the gas will be expanded and cooled (Joule-Thompson effect) and must be preheated to ensure that no liquid or solid phase condenses at the discharge; (iii) higher initial investment and operational costs compared with a standard regulation station. Poživil [2], simulated an expansion turbine use Aspen HYSYS process simulator software, where a temperature drops of 15–20 °C. In this paper, the possibility of getting condensed phase at the turbine exit is also analyzed for the composition of the Colombian gas supplied from the north region of the country. Mahbubur [3], analyzed the potential of using this technology for Bangladesh, founding that the power recovery at individual locations is not very large Proceedings of the IASTED International Conference Power and Energy (PE 2013) November 11 - 13, 2013 Marina del Rey, USA DOI: 10.2316/P.2013.806-052 123