Stoichiometric oxygen demand

There are three general trends in SCWO kinetic data. First, in most cases, the oxidation rate is independent of or weakly dependent on the concentration of oxidants. As a general rule, the oxidant concentration is at least 200% in excess of stoichiometric oxygen demand. Second, the pseudo first-order kinetics with respect to the concentration of starting compounds is usually a reasonable assumption for SCWO. Third, the activation energy ranges from about 30 to 480 kj/mol. 

When the oxygen concentration is equal to 300% in excess of stoichiometric oxygen demand, the global rate of phenol destruction can be expressed as ... 

Excess air ratio was measured by the oxygen content of the flue gas. The excess portion of dry air volume is derived from the oxygen content of the flue gas and the stoichiometric oxygen demand. 

If the composition of the waste stream is known, then the theoretical oxygen demand can be calculated from the appropriate stoichiometric equations. As a first level of approximation, we can assume that this theoretical oxygen demand would be equal to the COD. Then, experience with domestic sewage indicates that the average ratio of COD to BOD will be on the order 1.5 to 2. The following example will help to clarify these relationships. 

The byproduct is a stoichiometric amount of 60 wt % H2S04, which is used in the chemical industry. The wastewater (0.3 m3/100 kg active matter), which contains paraffin, oxidation products of the paraffin, alkanesulfonate, and sulfur dioxide, has a chemical oxygen demand (COD) of 1800 mg/L and is readily biodegradable (>95% after 7 days). The sulfur dioxide emission after repeated washing of the off-gas amounts to 0.5 g/100 kg active matter [6]. 

The stored oxygen demand was estimated from the difference between the actual conversions measured at the stoichiometric point with +0.5 A/F perturbations at 1 Hz and steady state conversions measured at the +0.5 and -0.5 A/F extremes. 

The theoretical chemical (or ultimate) oxygen demand, or ThCOD (BODU), can be calculated for a wastewater with relatively few oxidizable components. The procedure requires one to calculate the equivalent oxygen concentration necessary for the complete stoichiometric oxidation of each of the wastewater components to its corresponding highest oxidation state and sum them for the total wastewater ThCOD. Carbonaceous components of wastewater generally considered to be fully... 

Aphotic zone oxygen consumption rates that, when vertically integrated, provide a net water column oxygen demand that can then be related stoichiometrically to a carbon export flux. 

The theoretical oxygen demand (ThOD) is solely the oxygen needed on a stoichiometric basis to oxidize the solvent completely and is thus the worst possible effect but may be useful if no laboratory results are available. In this book the values of ThOD do not include for the oxidation of the nitrogen where it exists in the solvent s molecule. This tends to be a slow reaction and seldom is represented in the 5-day BOD test. 

The results are quoted as oxidizability (potassium permanganate consumption) in mg/1 KMnO/ and additionally in mg/1 (oxygen equivalent) in a similar manner to the chemical oxygen demand. On the basis of the stoichiometric relationships... 

In this review we will focus on their use as catalysts and promoters in the introduction of molecular oxygen into organic substrates. Oxidized hydrocarbons serve as important feedstocks for the chemical and pharmaceutical industries. Unfortunately, hydrocarbons are also infamous in their ability to resist oxidation under environmentally benign and easily controlled conditions. The large volume of these materials needed to satisfy the demand of the chemical industry economically precludes all stoichiometric oxidants, with the sole exception of molecular... 

At the outlet of the anode the gas (RG) consists of the non-utilised fuel and the reaction products CO2 and H2O. This mass flow is equal to the mass flow of the utilised fuel and of the transferred oxygen by the ion conduction through the electrolyte. The stoichiometric demand of oxygen related to the inlet fuel mass flow is given by the figure //.o2o- Finally, we get for the enthalpy flow at the anode outlet... 

Concerning the oxidative path, operating conditions must ensure excess oxygen concentration over the stoichiometric demand during the full course of the reaction. 

The reforming exchanger concept totally eliminates the furnace and uses a hot secondary reformer outlet as its heat source. Surplus air over the stoichiometric demand or oxygen-enriched air in the secondary reformer is required to balance the heat demand for the primary reforming reaction. Chiyoda proposed this concept in 1984 [26,271 however, ICI was the first one. to comr mercialize a reformer exchanger called the Gas Heat Reformer (GHR) as part of their Leading Concept Ammonia (LCA) process. The GHR is discussed further under the LCA process section. 

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