Oxidative refining

Process Safety Considerations. Unit optimization studies combined with dynamic simulations of the process may identify operating conditions that are unsafe regarding fire safety, equipment damage potential, and operating sensitivity. Several instances of fires and deflagrations in ethylene oxide production units have been reported in the past (160). These incidents have occurred in both the reaction cycle and ethylene oxide refining areas. Therefore, ethylene oxide units should always be designed to prevent the formation of explosive gas mixtures. 

Phenol is recovered from the acetone finishing column bottoms (12) by extraction with caustic. AMS in the raffinate is then concentrated (13), hydrogenated (14) and recovered as cumene for recycle to oxidation. Refined AMS production is optional. 

B is one of the common impurities in the metallurgical grade Si. Since B is difficult to remove by either of directional solidification or evaporation, the oxidative refining processes are frequently used to remove B from liquid Si. 

The oxygen needed for the refining reactions in oxidative refining can be introduced either... 

Gas-blowing is usually combined with the addition of some kind of slagforming additives (e.g., CaO, MgO, and fluorides) that may also act as oxidizing agents. The removal of B from molten Si by a steam-added plasma can also be regarded as an oxidative refining process. 

Carbide precipitation hardening (in TZM, MHC) is effective up to 1400 °C. The addition of the deformable oxides La203 (in ML) and xKqO y Si02 (in K—Si—Mo), respectively, results in oxide refinement by deformation and in the possibility of tailoring the mechanical properties. This is the main alloying mechanism for Mo applied in lamps [1.119]. 

Here again, this is not a refining process, properly speaking. Partial oxidation is one of the processes for the ultimate conversion of heavy residues, asphalts, coke and even coal. 

Aluminium is obtained on a large scale by the electrolysis of the oxide, dissolved in fused cryolite The oxide, occurring naturally as bauxite, AI2O3.2H2O, usually contains silica and iron(III) oxide as impurities. These must be removed first, since aluminium, once prepared, cannot be freed of other metals (which will be deposited on electrolysis) by refining it. The crude oxide is dissolved under pressure in caustic soda solution the aluminium oxide and silica dissolve and the ironflll) oxide is left ... 

Before this treatment, the cassiterite content of the ore is increased by removing impurities such as clay, by washing and by roasting which drives off oxides of arsenic and sulphur. The crude tin obtained is often contaminated with iron and other metals. It is, therefore, remelted on an inclined hearth the easily fusible tin melts away, leaving behind the less fusible impurities. The molten tin is finally stirred to bring it into intimate contact with air. Any remaining metal impurities are thereby oxidised to form a scum tin dross ) on the surface and this can be skimmed off Very pure tin can be obtained by zone refining. 

The process of extraction requires first smelting (to obtain the crude metal) and then refining. In smelting, iron ore (usually an oxide) is mixed with coke and limestone and heated, and hot air (often enriched with oxygen) is blown in from beneath (in a blast furnace). At the lower, hotter part of the furnace, carbon monoxide is produced and this is the essential reducing agent. The reduction reactions occurring may be represented for simplicity as ... 

It is used in certain nickel-based alloys, such as the "Hastelloys(R)" which are heat-resistant and corrosion-resistant to chemical solutions. Molybdenum oxidizes at elevated temperatures. The metal has found recent application as electrodes for electrically heated glass furnaces and foreheaths. The metal is also used in nuclear energy applications and for missile and aircraft parts. Molybdenum is valuable as a catalyst in the refining of petroleum. It has found applications as a filament material in electronic and electrical applications. Molybdenum is an... 

ALKANOLAMNES - ALKANOLAMINES FROM OLEFIN OXIDES AND ALETONIA] (Vol 2) -in petroleum refining [PETROLEUM - REFINERY PROCESSES, SURVEY] (Voll8)... 

Product refining is quite facile, following the same general pattern for acetic acid (qv) recovery from acetaldehyde Hquid-phase oxidation. Low... 

Fig. 3. Typical nitric acid oxidation process. A, reactor B, optional cleanup reactor C, bleacher D, NO absorber E, concentrating stUl F, crude crystallizer G, centrifuge or filter H, refined crystallizer I, centrifuge or filter , dryer K, purge evaporator L, purge crystallizer M, centrifuge or filter N,...

---