New materials developed to improve the corrosion resistance of carbon steel pipe

With the rapid development of the coastal petrochemical and power industries, the application of using seawater to replace the increasingly tense freshwater as industrial cooling medium can save a lot of fresh water resources, and get access to obtain significant economic and social benefits. However, due to the strong corrosion resistance of seawater, when using ordinary carbon steel or stainless steel tubes, water as the cooling medium will cause serious corrosion of the tube bundle, which can significantly reduce the life of the heat exchanger. This not only increases the number of replacement equipment, but also because of equipment failure causing equipment downtime too often and making the economic benefits reduced.
Under normal circumstances, to solve this problem, the pipe need to be done material upgrading, and upgrade materials mainly uses copper-nickel alloy and titanium tubes. Due to the high production cost of titanium tubes, it is difficult to be accepted by many users to, and copper-nickel alloy may cause corrosion due to serious pollution of seawater.
For the heat exchanger, its development has been largely relying on the adoption of the new material. Under many occasions, serious corrosion appears, the measures mainly adopted are:one surface corrosion, two is the choice of the new corrosion resistant material. The corrosion current application of new materials is mainly titanium tube, Hastelloy, super duplex stainless steel, zirconium tubes. These materials have good corrosion resistance, but their common drawback is the device cost is too high, so that the general business  is difficult to accept.
To solve the practical problems, there are companies combining the carbon steel pipe, stainless steel pipe with relatively low cost materials and thin-walled titanium tubes with strong corrosion resistance together, being applied to heat exchange equipment, and developed the desired anti-corrosion effect, the manufacturing cost is relatively low (+20 titanium steel, titanium and titanium tube was 40% + austenitic stainless steel, pure titanium pipe of 60%) and the use of the same performance and titanium tube heat exchanger tube bundle successfully. Compared with ordinary carbon steel pipe, has the following outstanding advantages:
(1) The superior corrosion resistance. In the medium offshore seawater heat exchanger tube bundle, the corrosion resistance of titanium tube is incomparable to any other pipe, composite pipe is the use of titanium tubes to achieve the advantages of corrosion-resistant, easy to scale, easy to plug, sea easy attachment of biological effects.
(2) reduce the cost of anti-corrosion materials. Composite pipe heat exchanger using thin-walled titanium tube bundles to meet corrosion requirements and use steel or stainless steel as the strength of the body, to the use of titanium tube heat exchanger effectiveness and cost much less than the latter.
(3) reduce maintenance costs. In the heat transfer area 700m2 meter under the same conditions, a flat carbon steel tubes annual maintenance cost of about 40,000 yuan, while the composite tube bundle corrosion maintenance cost is almost zero.
(4) extend the service life. Common organic preservative bundle the general life of 1 to 2 years, and titanium composite tube bundle life of over 10 years.
(5) conservation of freshwater resources to reduce overall energy consumption. Social and economic benefits using seawater were significantly higher than fresh water. Because seawater is lower than the ambient temperature 6 ~ 10 ℃, while circulating the water temperature higher than the ambient temperature is 3 ~ 5 ℃, the temperature difference between the two composite above 10 ℃, and the overall cost of the circulating water system is much higher than seawater. Meanwhile, since the surface of the circulating water will produce microbial attachment bundle and fouling can reduce heat transfer efficiency, and the titanium composite pipe can be effectively prevented in order to avoid adhesion of microorganisms to reduce heat transfer efficiency.