Corrosion and foam

The composition of these solvents is typically subject to change during operation due to a variety of causes, for example solvent degradation (oxidative and/or thermal), solvent evaporation (vaponr pressnre and/or aerosols), solvent inactivation due to heat stable salt formation, and imbalance of the water management. Some of these canses are inherent to the process and solvent that are used, while others depend on the quality of the gas stream that is treated. In addition, these canses can also enhance other unwanted effects such corrosion and foaming. 

The irreversible reactions of amines with O2, CO2, COS, and CS2 are discussed in the preceding sections. The principal other potentially reactive gas phase impurities which may enter the absorber are organic acids (such as formic or acetic acids), HCl, HCN, SO2, NH3, and mercaptans. All of the acidic compounds form salts with the alkaline amines. If the acids are stronger than CO2 and H2S, their amine salts are not efficiently decomposed under the stripping conditions (which are designed to decompose the amine-C02 and amine-H2S salts), and they build up in the solution as heat-stable amine salts (HSAS). This, of course, lowers the capacity of the solution for CO2 and H2S, and can lead to other operational difficulties such as corrosion and foaming. Caustic soda or soda ash is often added to the solution to tie up the acids as sodium salts and release the amine however, sodium salt build up... 

When heat stable salt buildup becomes a problem a variety of options may manage it. These include partial or total solution replacement, heat stable salt removal, or adding caustic to neutralize the heat stable salts. Many operators choose caustic addition because it is perceived to be a more economical way to stop corrosion and subsequent foaming and loss problems. 

The hydraulic oil must provide adequate lubrication in the diverse operating conditions associated with the components of the various systems. It must function over an extended temperature range and sometimes under boundary conditions. It will be expected to provide a long, trouble-free service life its chemical stability must therefore be high. Its wear-resisting properties must be capable of handling the high loads in hydraulic pumps. Additionally, the oil must protect metal surfaces from corrosion and it must both resist emulsification and rapidly release entrained air that, on circulation, would produce foam. 

A properly formulated engine coolant concentrate is composed of several essential ingredients, including base fluid, corrosion inhibitors, foam suppressor, dye, and water. 

FIG. 3—Exhaust gas leakage into the cooling system can cause foaming, overflow, loss of coolant, overheating, and shortened inhibitor life with subsequent corrosion and rust clogging. 

Fuel system corrosion inhibitors must have a low tendency toward emulsification with water and toward foam enhancement in turbulent systems. These properties are especially critical whenever inhibitors are used in jet fuel. The sensitivity of jet fuel pumping and injection systems requires that fuel be free of emulsions and foam. 

Hot Lime Zeolite-Split Stream Softening. Many raw waters softened by the first two processes would contain more sodium bicarbonate than is acceptable for boder feedwater purposes. Sodium bicarbonate will decompose in (lie boiler water to give caustic soda. Caustic soda in high concentrations is corrosive and promotes foaming. The American Boiler Manufacturers Association has adopted the standard that the alkalinity content should not exceed 20% of the total solids of the boiler water. Split stream softening provides a means for reducing the alkalinity content. 

Modern motor oil provides an example of some of the ways in which a number of colloidal and interfacial considerations come into play adhesion and lubrication, detergency, dispersion and suspension stabilization, foam inhibition, and viscosity and its temperature dependence. In addition to providing lubrication, a motor oil is expected to prevent corrosion and aid engine cooling and cleaning. Table 8.1 shows how a number of additives are blended in to help the oil achieve these functions [491]. 

PG-1 covers the development of a category for manual transmissions used in trucks and buses. The key performance needs are thermal stability, seal compatibility, copper corrosion, anti-wear, high temperature lubricant stability and foaming. PG-1 is known as GL-7 ... 

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