Author: Site Editor Publish Time: 2022-12-16 Origin: Site
Dissolved oxygen and free carbon dioxide in water are the main factors causing corrosion in feedwater systems. Boiler feedwater deaeration and carbon dioxide is the key to ensure the safe and economic operation of boilers. This paper introduces the principle and application of degassing membranes through the system design, frame assembly and operating parameters of engineering examples, and ensures efficient and stable operation of the degassing membrane process, fully reflecting the superiority of degassing membrane technology in the application of water treatment and de-oxygenation process.
The degassing membrane is made of a water-repellent micro-porous hollow fibre membrane made of polypropylene polymer and PTFE polymer, which allows dissolved gases in the water to pass through the micro-porosity of the membrane to achieve a gas-water separation effect. The membrane consists of a number of microporous hollow polypropylene fibres woven together and wrapped around a cloth water pipe. The hollow fibres are non-hydrophilic so that the water does not penetrate into the microporous pores. High purity nitrogen is generally used as blow off gas to remove oxygen and carbon dioxide from water.
The various failures of boilers related to oxygen corrosion account for more than 40%, about 70% of boilers have varying degrees of oxygen corrosion, causing significant losses to the economy and production. Boiler oxygen corrosion of metal is a kind of electrochemical corrosion, also known as depolarisation corrosion. When the boiler feed water residual dissolved oxygen and carbon dioxide, the tube wall metal in the pure iron and impurities between the potential difference, the formation of numerous tiny corrosion cells. Ferrous ions (Fe2+) will become ferrous hydroxide when encountering dissolved oxygen, while Fe(OH)2 is unstable, the metal of the tube wall will soon be corroded, Fe(OH)3 and its dehydration product Fe2O3 is the main component of the red-brown rust.
The advantages of membrane oxygen removal are small footprint, light weight, low operating costs, degassing in a closed system, clean, pollution-free, easy to manage, room temperature operation, no chemical consumption, long service life of the membrane, easy to operate, stable operation, in addition to oxygen removal can also remove carbon dioxide and other gases in the water, oxygen removal water quality is good, no secondary pollution to the environment. This method of removing oxygen from boiler feed water at room temperature can ensure water safety, high efficiency and energy saving, and will gradually become a high-tech replacement for traditional oxygen removal methods.