4.1) Natural gas heater
Natural gas ducts are under 60 atm pressures. At the city-gates, where smaller diameter pipelines take the gas to consumption points, the pressure is lowered to 20 atm. For security reasons, these decompression and measurement stations are usually located on remote areas. The city-gate requires a heating gas device in order to avoid the natural gas to freeze during expansion. The commercially available system employs an indirect heating gas burner, as shown in Figure 1. The device has a liquid water bath with two pipe lines: one carries hot combustion gas generated by the gas burner and the other carries natural gas to be heated (Figure 2-a). The hot gas tube heats the bath, which heats the natural gas. Such a device requires periodical water refilling, because the water vaporizes under operation. Since the device is located in remote areas, the maintenance team has to take water to the site by ground transport.
The vapor chamber concept can be used to indirectly heat natural gas (Figure 2-b). The device would then require a sealed tank with both liquid and water vapor, in the absence of atmospheric air. The water level in the tank must submerge the hot gases tube. The heat vaporizes the liquid water and the vapor comes condenses on the cold natural gas tube, transferring heat to the tube walls. Therefore, water transfers heat from hot gas pipe to the cold natural gas pipe through phase change. A clear advantage in using the vapor chamber concept in this device would be the non-refilling of water, because the tank is sealed, as well as a reduction in the overall thermal resistance.
Publications: MANTELLI, M. B. H.; ÂNGELO, W. B.; MILANEZ, F. H. Aquecedores de GN para City-Gates Assistidos por Termossifões e Câmara de Vapor. In: 1º Seminário da Rede Gás & Energia, 2006, Rio de Janeiro, 2006.
MILANEZ, F. H.; MANTELLI, M. B. H.; BORGES, T. P. F.; LANDA, H. G. Aquecimento Indireto de Gás Natural com uso de Câmaras de Vapor. In: Rio Pipeline Conference & Exposition 2005, 2005, Rio de Janeiro.
