Bahia de Bizkaia Regasification Plant, Spain

Bahía de Bizkaia or BBG is a regasification facility located in Bilbao, Spain. Owned jointly by four partners, BP, EVE (Ente Vasco de la Energía – Basque Energy Board), Iberdrola and Repsol YPF, the facility supplies natural gas for domestic, industrial and commercial consumption. Its main activity includes regasification of LNG brought in gas tankers. The gas produced at the facility is also used for generating electrical power at Bahía de Bizkaia Electricidad’s (BBE) plant.

The facility was built in 30 months at a cost of €264m. It came into operation in August 2003, with the first gas tanker arriving on 8 August 2003. Designed to operate 24 hours a day, 365 days a year, the facility has the capacity to produce 800,000m3 of gas per hour.

Design

The facility consists of a boil-off system, an LNG delivery system, vaporisers and pipers. The system is equipped with a Sulzer Espana boil-off collector and compressor, and an Idesa-manufactured re-condenser. There are primary LNG pumps and natural gas burners in the LNG delivery system. The LNG delivery system also contains two storage tanks, one inside the other, that have a capacity to store 150,000m3 of LNG.

The self-contained storage tanks are designed to keep evaporation losses at less than 0.05% a day. Built completely out of 9% nickel steel, the innermost primary tank consists of an open-top cylinder, a flat metal base and a flat ceiling supported by hangers from the outer concrete tank.

The suspended ceiling is meant to provide thermal insulation. To prevent the granular perlite from entering the tank, a metal seal has been formed with elongated panels placed above the top ring of the tank. The ceiling is also fitted with an aperture at the centre.

The secondary tank is formed of a metal-concrete foundation slab, a cylindrical-shaped post-tensioned concrete wall and a dome made of metal and concrete. The foundation slab and the ceiling form a single unit without connectors. Cryogenic passive reinforcements are fitted at the ring beam inside the metal tank while the outer side of the concrete tank is fitted with standard passive reinforcements.

The interior of the concrete tank is covered with a protective carbon steel plate lining. An insulation system that encloses the inner tank from all sides covers the inside of the outer tank.

The foundation slab of the tank sits atop a secondary base of 9% nickel steel. Between this base and the foundation slab, an insulating material (foamglass blocks) is positioned to prevent the evaporation of gas. Further insulation is provided by using expanded perlite, glass wool and fibreglass in the walls, the ceiling and the outer surface of the ceiling.

The facility also includes seawater vaporisers, a submerged combustion vaporiser, and safety and relief valves. Regulating and metering stations have been installed at the facility to direct the regasified and odourised LNG to the gas grid or to the combined cycle gas turbine plant on the site next to the regasification terminal. The facility is also equipped with smokestacks to burn production and emergency discharges.

Pipeline

The facility has two pipelines to transport the LNG from ships to storage tanks. The first pipeline, measuring 42in in length, runs parallel to another pipeline that stretches 6in. Gas is transported via these pipelines to a 36in manifold situated in the storage tank zone. To allow gas to flow through, the pipelines are fitted with bypasses.

Process technology

The LNG is unloaded from the ship via three unloading arms at a rate of 12,000m³/h. The gas is stored in storage tanks that have a design pressure of 290mbarg. As the vapour return line in the storage tank is maintained at an ambient temperature to prevent the gas from heating, the gas is allowed to circulate continuously. It flows through the 40in pipeline to the loading zone from where it returns via the 6in pipeline to re-liquefaction unit. To maintain the vapour that enters the ship below -120 degrees, LNG is injected at the cooling unit of the return line leading to the ships. The wharf area also contains a separator tank that removes any liquid remaining downstream from the cooler.

The surplus boil-off vapours are sent from the storage tanks to the compressor via the manifold. A smokestack system installed at the facility removes the excess gas safely.

Prior to being condensed into sub-cooled LNG, the gas is compressed. LNG pumps installed in the storage tanks push the LNG to the re-condenser via the send-out manifolds. The compressed boil-off gas is then condensed in the re-liquefaction unit, using LNG from the tanks.

From the re-liquefaction unit, the LNG is routed to the send-out-pumps. The send-out pumps release gas to the vapourisers via send-out manifolds at a pressure of about 82 barg. The vapourisers that operate at nearly 80 barg, convert the LNG into gaseous form by increasing the gas temperature to 0 degrees.

The produced natural gas is released from the vapourisers at a pressure of 72 barg and 45 barg, with a minimum temperature of 0 degrees. The gas is then routed via the metering station to the natural gas grid at 72 barg. Before reaching the gas grid, the gas is odourised with liquid additives such as THT (tetrahydrothiophene). The gas meant for the power plant is preheated with seawater before passing to the regulating and metering station where its pressure is brought down from 72 barg to nearly 47 barg.