Corrosion from liquid systems

The parameter p (= 7(5 ) in gas-liquid sy.stems plays the same role as V/Aex in catalytic reactions. This parameter amounts to 10-40 for a gas and liquid in film contact, and increases to lO -lO" for gas bubbles dispersed in a liquid. If the Hatta number (see section 5.4.3) is low (below I) this indicates a slow reaction, and high values of p (e.g. bubble columns) should be chosen. For instantaneous reactions Ha > 100, enhancement factor E = 10-50) a low p should be selected with a high degree of gas-phase turbulence. The sulphonation of aromatics with gaseous SO3 is an instantaneous reaction and is controlled by gas-phase mass transfer. In commercial thin-film sulphonators, the liquid reactant flows down as a thin film (low p) in contact with a highly turbulent gas stream (high ka). A thin-film reactor was chosen instead of a liquid droplet system due to the desire to remove heat generated in the liquid phase as a result of the exothermic reaction. Similar considerations are valid for liquid-liquid systems. Sometimes, practical considerations prevail over the decisions dictated from a transport-reaction analysis. Corrosive liquids should always be in the dispersed phase to reduce contact with the reactor walls. Hazardous liquids are usually dispensed to reduce their hold-up, i.e. their inventory inside the reactor. 

Materials in the whole system must be appropriate, that means reactor and piping for ozone gas as well as for ozonated water must be chosen carefully. For example, the material of the reactor and sampling system, especially the seals, has also to be chosen to avoid not only corrosion from ozone, but adsorption of the compound(s) being studied. It is advisable to let the liquid phase contact only glass and stainless steel. In stirred reactors for example, the stirrer seals (unless the stirrer is a magnetic bar) and all connectors for piping are best placed at the top of the reactor, so that the liquid does not come in contact with them. 

Industrial Problems. Problems have also been encountered in attempts to commercialize various homogeneous catalytic reactions. These, in addition to the highly corrosive nature of many metal solution systems involve general problems of large scale handling of liquid systems such as mass and heat transfer and the isolation of products from solution. Moreover, the recovery and/or regeneration of metals often presents difficulties. 

Referring to Fig. 4.3 these values lie in region II indicating that the reaction is only moderately fast and that a relatively high liquid hold-up is required. A packed column would in any case therefore be unsuitable. We therefore conclude from the above considerations that an agitated tank, a simple bubble column or a packed bubble column should be chosen. The final choice between these will depend on such factors as operating temperature and pressure, corrosiveness of the system, allowable pressure drop in the gas, and the possibility of fouling. 

Hiac 2000 liquid particle counter provides an inexpensive means to transfer up to four channels of particle size information data from sensor to host computer system. Data can be viewed in real-time via a liquid erystal display. The 2000 interfaces to all Hiac liquid sensors including the MicroCount, submicron and HRLD laser sensors. Applications include point-of-use monitoring for corrosive chemieal delivery systems, DI water lines, wet process tools, hydraulic oil systems and parts cleaning... 

Vanadium also forms a very stable carbide VC, and carburization of this metal is part of the corrosion reactions of vanadium based alloys contacted with liquid lithium as well as sodium. Vanadium alloys with contents of titanium have an even higher affinity to form solid carbides by absorbing of carbon from liquid metals. In systems in which vanadium titanium alloys and stainless steels are in contact with the same lithium or sodium, carbon migrates from the steel to the refractory metal alloy, thus passing the alkali metal serving as a transport medium The free energies of formation of the alkali acetylides are compared with the values of several metal carbides in Table V. 

Callium Elemental gallium can be electrodeposited from both chloroaluminate [17] and chlorogallate [18] ionic liquids. In the latter case l-ethyl-3-methylimidazohum chloride was mixed with GaQs, thus giving a highly corrosive ionic liquid that was studied for GaAs thin film electrodeposition. In the chloroaluminates Ga can be deposited from Lewis acidic systems. It was found that the electroreduction from... 

The more common classification scheme is to divide the corrosive media into their state of aggregation, that is to subdivide into corrosion by solids, liquids and gases. While solid state corrosion is rarely dealt with, we have vast amount on literature on hot gas corrosion. The case of corrosion by liquids is commonly further subdivided into more specific cases, such as aqueous corrosion (e.g. acids and water), corrosion by glasses, metal melts and salt melts. The last case is for historic reasons known in the form of a rather misleading expression hot corrosion. A special case, which spans from the liquid into the gaseous state is given by the corrosion in hot water systems hydrothermal corrosion. 

In one study, the corrosion resistance of tantalum in a vapor-liquid mixture from the system H3PO4-KCI-H2O containing 60-250 ppm fluoride has been investigated at 120°C and atmospheric pressure. Corrosion rates... 

Heavy foaming can be expected in systems involving heavy oils, amines, or insoluble fine solids. Corrosion products or chemical breakdown end products often collect on the liquid surface and cause foaming. Filtration or adsorption operations commonly are employed to remove such contaminants from the system. 

The liquid from the centrifuge flows into a clarifier from which settled particles are returned to the crystallizer, and clarified liquor (containing 0.7 to 1.0% sulforic acid) is returned to the absorber/oxidizer circuit The flow rate of the return stream is approximately 500 gpm. A small amount of the dilute acid is continuously purged from the system to prevent build-up of chlorides that could cause corrosion of stainless steel equipment. A chloride limit of 200 ppm has been specifred for the plant Hie catalyst, iron sulfate, is not a major... 

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