Temperatures retention times

Relatively high (typically 980—1200°C) temperatures are required to decompose spent acids at reasonable burner retention times. Temperatures depend on the type of spent acid. A wide variety of spent acids can be processed in this way, but costs escalate rapidly when the sulfuric acid concentration in spent acid (impurity-free basis) falls below about 75%. A few relatively uncontaminated spent acids can be reused without decomposition by evaporating the excess water in concentrators, or by mixing in fresh sulfuric acid of high concentration. Weak spent acids are frequently concentrated by evaporation prior to decomposition. 

O Changes in process conditions, such as retention times, temperatures, agitation, pressure, and catalysts... 

Tests must be performed throughout implementation in order to optimize performance of the system. For example, indications are that RAC-activated sludge operates more efficiently on longer residence times and the same solids retention time. Temperature also has a major effect on reactor performance. 

Net retention time Replaced by Retention time Corrected retention time Temperature Trennzahl number (SN)... 

A series of experiments was conducted to examine the response of the sphalerite concentrate to ferric ion leaching. The parameters varied were retention time, temperature and the initial ferric ion concentration. 

Retention times, temperatures, and turbulence are interdependent. For example, secondary chambers that are specially designed for maximum turbulence but that have relatively short retention times may perform as well as other designs with longer retention... 

Mobile-phase hold-up time it is also equal to the retention time of an unretained compound Peak elution time Adjusted retention time Corrected retention time Temperature in general (always in Kelvin)... 

Temperature regulation is recommended to maintain within-day and day-to-day reproducibility. VariatiOTis in column temperature result in substantial fluctuation of the carotenoid retention times. Temperature may also influence selectivity. 

Fntrained Systems. In entrained systems, fine grinding and increased retention times intensify combustion but the temperature of the carrier and degree of dispersion are also important. In practice, the coal is introduced at high velocities which may be greater than 30 m/s and involve expansion from a jet to... 

The definition of polymer thermal stabiUty is not simple owing to the number of measurement techniques, desired properties, and factors that affect each (time, heating rate, atmosphere, etc). The easiest evaluation of thermal stabiUty is by the temperature at which a certain weight loss occurs as observed by thermogravimetric analysis (tga). Early work assigned a 7% loss as the point of stabiUty more recentiy a 10% value or the extrapolated break in the tga curve has been used. A more reaUstic view is to compare weight loss vs time at constant temperature, and better yet is to evaluate property retention time at temperature one set of criteria has been 177°C for 30,000 h, or 240°C for 1000 h, or 538°C for 1 h, or 816°C for 5 min (1). 

Chlorination can be carried out at 25°C or below. However, the reaction is exothermic and, as mills have used filtrate recycle, operating temperatures have unavoidably risen. Retention times are 30—60 minutes but decrease as temperature increases. In most mills the retention time cannot be changed because the tower is upflow in design. The normal pulp consistency is 3—4%, but the trend is toward higher (ca 10%) consistency or gas-phase chlorination. Target pH in the chlorination stage (also (7 ) is about 1.8. 

Pre-liming. Lime slurry, 0.25% lime on juice (0.250 g of CaO/100 g juice), is added to bring the pH of the mixture into the alkaline range. Insoluble calcium salts are precipitated as finely dispersed coUoids. Calcium carbonate in the form of recycled first carbonation sludge is added to provide coUoid absorption and stabilization. Temperature may be cool (50°C) or hot (80°C) depending on the temperature of the next step, or occasionally on the type of diffusion equipment. Retention time is 15 to 30 min. 

First Carbonation. The process stream OH is raised to 3.0 with carbon dioxide. Juice is recycled either internally or in a separate vessel to provide seed for calcium carbonate growth. Retention time is 15—20 min at 80—85°C. OH of the juice purification process streams is more descriptive than pH for two reasons first, all of the important solution chemistry depends on reactions of the hydroxyl ion rather than of the hydrogen ion and second, the nature of the C0 2 U20-Ca " equiUbria results in a OH which is independent of the temperature of the solution. AH of the temperature effects on the dissociation constant of water are reflected by the pH. 

Second Carbonation. Calcium is reduced to the practical minimum by the addition of carbon dioxide at a OH of 4.5 at a temperature of as near to 100°C as possible. This is the maximum temperature in the purification process and the retention time is only long enough to effect the OH... 

Other advantages of gravity beds include flexibility in gas and sohds flow rates and capacities, variable retention times from minutes to several hours, space economy, ease of startup and shutdown, the potentially large number of contacting stages, and ease of control by using the inlet- and exit-gas temperatures. 

For estimating purposes for direct-heat drying applications, it can be assumed that the average exit-gas temperature leaving the sohds bed wih approach the final solids discharge temperature on an ordi-naiy unit carrying a 5- to 15-cm-deep bed. Calculation of the heat load and selec tion of an inlet-air temperature and superficial velocity (Table 12-32) will then permit approximate sizing, provided an approximation of the minimum required retention time can be made. 

The method was validated in accordance to the guidelines of the international conference on harmonization (ICH). Data with respect to accuracy, within- and between run precision, recovery, detection and quantitation limits were reported and found to be within the accepted international criteria. Neither endogeneous substances nor the commonly used dmgs were found to interfere with the retention times of the analytes. Standard solutions of the dmg and quality control preparations at high and low level concentrations were demonstrated to be stable at room temperature and/or -20°C for long and short periods of time. 

They include the combustion chamber, gas burners, burner controls, and exit temperature indicator. Usual exit temperatures for the destruction of most organic materials are in the range of 650°-825°C, with retention times at the elevated temperature of 0.3-0.5 sec. 

It is seen that the viscosity of the gas will change significantly during a temperature program and, thus, at a constant gas mass flow rate, the inlet pressure will rise proportionally. This increase in inlet pressure will result in an increase in the inlet/outlet pressure ratio and, as a consequence, will extend the retention time and oppose the effect of any increase in temperature. It also follows that the effect of... 

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