Oxygen Control

Oxygen Control. To meet industrial standards for both oxygen content and the allowable metal oxide levels in feed water, nearly complete oxygen removal is required. This can be accompHshed only by efficient mechanical deaeration supplemented by an effective and properly controlled chemical oxygen scavenger. 

An issue with chelants, and especially EDTA as the most widely used chelant, is the risk of corrosion to the feed equipment, feed injection points, and ultraclean boiler surfaces. This issue is generally associated with a lack of oxygen control in some way or other. 

DEHA breaks down at high pressure. Its survival pressure is probably not in excess of 1,250 psig, but because of its high volatility and rapid reaction rate, it generally provides complete boiler cycle oxygen-control coverage. Some limited ammonia is also generated, and this may be useful for carbon dioxide neutralization. 

Hollander, Orin B. Oxygen Control in Boiler Circuits. Ultrapure Water, Tall Oaks Publishing, Inc., USA, March 1994. 

First, a food quahty relationship model has been developed. It considers food quahty (FQ) to be dependent on food behavior (FB) and human behavior (HB). FB is a function of food dynamics (FD) (such as variable pigment concentrations and differing color degradahon prohles) and apphed technological conditions (TCs) (such as oxygen control to maintain color concentrahons). Likewise, HB is a function of human dynamics (HD) (for example, varying color perceptions due to age differences), and administrative conditions (ACs) (such as use of color cards to support visual color inspection). These relations are reflected in the food quahty relationship model as ... 

Michaelsen M, R Hulsch, T Hdpner, L Berthe-Corti (1992) Hexadecane mineralization in oxygen-controlled sediment-seawater cultivations with autochthonous microorganisms. Appl Environ Microbiol 58 3072-3077. 

Puig, S., et al., An on-line optimisation of a SBR cycle for carbon and nitrogen removal based on on-line pH and OUR The role of dissolved oxygen control, Water Sci. Tech., 53,171, 2006. 

Thermochemical conversion processes use heat in an oxygen controlled environment that produce chemical changes in the biomass. The process can produce electricity, gas, methanol and other products. Gasification, pyrolysis, and liquefaction are thermochemical methods for converting biomass into energy. 

The concentration of ozone taken up by the media containing linolenic acid is plotted against time after addition in Figure 8. The rate of ozone breakdown is constant (ozone uptake linear with time) for the first two min until about 0.12 ml ozone are absorbed and then the rate decreases sharply, reaching a steady-state rate of ozone uptake between 10-12 min. This first break in the curve corresponds to an ozone uptake of 0.12 ml + (24 moles/liter) = 0.005 millimoles (or 10 M). This is equivalent to 1 mole of linolenic acid added per mole ozone absorbed. Thiobarbituric acid reactant production is also plotted on the same axis. This compound (TBA reactant) probably arises by formation of a three-carbon fragment (malondialdehyde) from the ozone-induced oxidation of linolenic acid (23). The rate of TBA reactant formation is also linear for the first 2 min at which point the curve undergoes a less pronounced break. Malondialdehyde formation ceases immediately when the ozone is shut off (Scrub 1 on). An oxygen control sample produced no malondialdehyde. 

Partial pressure of oxygen controls the nature of defects and nonstoichiometry in metal oxides. The defects responsible for nonstoichiometry and the corresponding oxidation or reduction of cations can be described in terms of quasichemical defect reactions. Let us consider the example of transition metal monoxides, M, 0 (M = Mn, Fe, Co, Ni), which exhibit metal-deficient nonstoichiometry. For the formation of metal vacancies in M, 0, the following equations can be written ... 

Some patients experience prolonged seizures, defined as a duration greater than 120 to 180 seconds. These patients require continued oxygenation, control of ventilation, and an i.v. bolus of the anesthetic agent (20 to 40 mg methohexital) or diazepam (2.5 to 5 mg) to abort the seizure. 

Bevan and Anderson (32) deduced that adsorbed oxygen controlled the resistance of sintered zinc oxide at temperatures between 500°C and 1000°C. This conclusion was based on the observations that (1) the oxygen pressure had a reversible controlling effect on the resistance down to 500°C, too low a temperature for thermodynamic equilibrium to be... 

Constant supervision of wine tanks Prompt and current chemical analysis Organoleptic analysis before and after all wine transfers Sanitation of tanks, hoses, equipment, and pipelines on a rigid schedule Use of N2 and CO2 for oxygen control in bulk wine, in pipelines and in tanks... 

Oxygen control by timely topping of wine tanks Control of temperature during storage... 

Dissolved oxygen control strategies are associated with the oxygen transfer term in the oxygen mass balance (Equation 1) ... 

Typically, oxygen transfer can be modified acting through the rate of impeller agitation or through the aeration or micro-aeration flow rate, which change the ki a term of Equation 1. The dissolved oxygen controller... 

Dissolved oxygen control by the adjustment of the oxygen fraction in the sparged gas. Its total flow rate is kept constant and corresponds to the sum of the two controlled gases QI and Q2. 

Kapralek, F., Jechova, E., and Otavova, M. (1982) Two sites of oxygen control in induced synthesis of respiratory nitrate reductase in Escherichia coli. J. Bacteriol. 149, 1142-1145. 

Flanagan, M.J. Bracken, B.D. "Design procedures for dissolved oxygen control of activated sludge processes" USEPA, 600/2-77-032, June 1977. 

As mentioned previously, oxygen controls the corrosion rate in the neutral pH range, if the oxygen is less than 1 ppm, the penetration rate in carbon steel or cast iron will be less than 1 mpy (0.025 mm/y) at room temperature, provided no corrosive bacteria are present. If corrosion-inducing bacteria are present, treatment with a biocide such as chlorine is imperative. In theory, because freshwater can be treated, carbon steel exchanger tubes can be used. However, control of water treating equipment is sufficiently difficult and... 

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