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Collaborating Authors
Liquified natural gas (LNG)
ABSTRACT The use of titanium plate heat exchangers is widespread for Offshore and Coastal installations where seawater cooling is required. Several years ago difficulties to supply titanium Grade 1 for this application triggered the need for qualification of other alloys for this application. Applications using passive alloys are especially susceptible to crevice corrosion when exposed to hot seawater. Since titanium is the most corrosion resistant alloy in seawater only highly corrosion resistant alloys could be considered for its replacement in plate heat exchangers. In addition since they need to be shaped into plates by cold pressing only alloys with a high formability could be selected. This narrowed even further candidate alloys for plate heat exchangers. In this study nickel chromium molybdenum alloys and a highly alloyed stainless steel were tested between 30 and 70°C in natural seawater with up to 1 ppm free chlorine. Rather than using short term electrochemical testing that is often difficult to compare with service performance long term exposure tests (up to 18 months) of real plate heat exchangers were carried out. These tests are considered to be more representative of actual service conditions. The results of these tests and their significance are discussed and compared with previous reported work. INTRODUCTION Many industrial sites such as oil and gas production facilities are located on the sea shore and offshore. These facilities use seawater as a cooling medium because of its immediate availability. The cooling of fluids is a full part of the process through the use of tubular and plate heat exchangers (PHE's). Direct seawater cooling is normally used to limit cost and save space and weight. Titanium alloys are usually the preferred choice for seawater cooled heat exchangers because of their outstanding corrosion resistance even in hot aerated seawater and their good strength and low density. In particular low pressure seawater cooling is usually accomplished using PHE's made of Grade 1 titanium. This grade is used because of its good formability. Grade 2 is typically utilized in tubular HE. Several years ago new projects had difficulty securing deliveries of titanium Grade 1 for PHE's because of a high demand on the market and limited production capabilities. As a consequence it was decided to look for potential replacement alloys for this application. Two major properties are normally required for use as a PHE material: a good cold formability to easily press the plates into shape and an excellent corrosion resistance because very severe crevices are present in particular under the elastomer gasket seals. In addition the required plate thickness is low with typical values between 0.5 and 0.7 mm. This means that any localized corrosion would quickly lead to HE leaks which could have very serious consequences in terms of loss of production. This study was designed to investigate the effects of temperature, crevice tightness, and the addition of chlorine on service life because each of these parameters accelerates seawater crevice corrosion.
- Europe > France (0.48)
- North America > United States > Texas (0.29)
- Materials > Metals & Mining > Titanium (1.00)
- Machinery > Industrial Machinery (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.35)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Natural Gas Conversion and Storage > Liquified natural gas (LNG) (1.00)
INTRODUCTION ABSTACT A concerted 3-year R&D program has been completed in France and in the US on materials for heat exchangers of next generation nuclear gas-cooled reactors. The scope was to gain data on the mechanical and corrosion behavior of candidate heat exchanger alloys in the range of service conditions expected for a Very High Temperature Reactor (VHTR), specifically the temperature, the load and cycling, and the chemical environment. As far as corrosion was concerned, the main objectives of the program were to compare the performances of materials and to improve the understanding of their properties. Oxidation, carburization and decarburization modes were evidenced depending on the coolant impurity content. A special emphasis was placed on the consequences of corrosion on alloy properties: microstructure, ductility, tensile strength. Next step will involve the study of the environmental effect on fatigue and creep-fatigue life. This paper presents the main achievements on corrosion of the R&D program. As part of the US Department of Energy bilateral International-Nuclear Energy Research Initiatives (I-NERI), a 3-year concerted R&D program has been completed in April 2009 . The scope was the materials for heat exchangers of Generation IV high-temperature gas-cooled nuclear reactors (HTGR) such as the Next Generation Nuclear Plant NGNP, High Temperature Reactors HTR, the Gas-cooled Fast Reactor GFR, or Very High Temperature Reactors VHTR. HTGR systems may attain high yields for electricity generation and have the capability to efficiently produce hydrogen from the high temperature process heat produced in the core. Table 1 gives basic features of some of these concepts of nuclear plant. Except for the long-term GFR, the technology is based on the design of HTGR plants which have been built and operated in the past. The primary in-core structures are made of graphite, either as a prismatic block or as pebble-bed core. The key out-of-core structures include the reactor pressure vessel (made of 2 ¼ Cr steel or F/M steel), the cross-vessel component and the intermediate heat exchangers (IHX) which receive gas of the highest possible temperature for delivery to the hydrogen production plant. Such components place great demands on their materials of construction. INL for the US and CEA(B) for France were the leading organizations of the collaboration. The scope was to gain data on the mechanical and corrosion properties of IHX materials in the range of service conditions expected for these reactors, specifically the temperature, the load and cycling, and the chemical environment. (Table in full paper) Regardless of the IHX design - compact heat exchangers would be preferred from an efficiency standpoint but the manufacture technologies are not mature yet - material selection for this component is critical. The material must be available in the appropriate product form - both plate and sheet, weldable and suitable for use up to 750°C or above. Thin products must also sustain a differential pressure of 5 to 7 MPa during off-normal events. Therefore, mechanical strength at high temperature, as well as creep, fatigue, creep-fatigue and corrosion resistance is required for extended lifetime (tenths of years).
- North America > United States (1.00)
- Europe (1.00)
- Machinery > Industrial Machinery (1.00)
- Energy > Power Industry > Utilities > Nuclear (1.00)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
- Facilities Design, Construction and Operation > Natural Gas Conversion and Storage > Liquified natural gas (LNG) (1.00)