Temperature of pastes

BS crystals are obtained during paste preparation at temperatures higher than 80°C [51]. This technology yields long, well-shaped, 4BS crystals with a thickness that varies depending on the time of paste mixing and the temperature of paste preparation. When the paste is mixed for 10-20 min, the crystals are 2-4 pm thick and require 20-30 h for formation. The PAM... 

When the paste is prepared at 70 °C, considerable amounts of 3BS crystals remain unreacted even after 30 min of mixing. The situation is different when the process of paste preparation is carried out at 90 °C. In this case, the whole paste is converted into 4BS crystals within the first 10 min. At 80 °C, the transformation of 3BS to 4BS is completed within 30 min. This indicates that the process of nucleation and growth of 4BS crystals is very sensitive to the temperature of paste preparation. In order to produce 4BS paste within 30 min the temperature of paste preparation should be above 90 °C. 

The relatively high temperature of paste preparation and mixing accelerate the above reaction. 

The active mass obtained from pastes containing no H2SO4 (0%) has very low capacity, irrespective of the temperature of paste preparation. That is why battery manufacturers use basic lead sulfate pastes, and not lead oxide ones, for the production of positive plates. 

Let us now see what the effect of IBS pastes on battery performance. Figure 6.18 evidences that batteries produced with IBS pastes have the highest initial capacity, irrespective of the temperature of paste preparation. What is this high capacity due to ... 

Depending on the temperature of paste preparation and plate curing two types of cured pastes are obtained ... 

Fig. 4.21 Effect of accelerators on the rate of heat evolution during CjS hardening (according to [35]) 1 set accelerator (CaClj) or high temperature of paste, 2 accelerator of hardening (NaCl), 3 reference, 4 set retarder (low temperature)...

These systems have been operated in extremely low quality (and radioactivity contaminated) industrial environments for the past several years without any major equipment or component failures. Utilizing specialized operating/warm-up procedures, they have operated in low grade, out-of-doors, dust ridden, rain-soaked, industrial environments at temperature ranges which greatly exceed the original equipment manufacturers (OEM) specified limits. The systems have been successfully operated at ambient temperatures of minus 10 to plus 103 degrees Fahrenheit without any pre-mature or un-anticipated equipment failures. 

Add 20 g. of /)-bromoaniline to 20 ml. of water in a 250 ml. beaker, and warm the mixture until the amine melts. Now add 23 ml. of concentrated hydrochloric acid and without delay stir the mixture mechanically in an ice-water bath, so that a paste of fine /> bromo-aniline hydrochloride crystals separates. Maintain the temperature of the stirred mixture at about 5° whilst slowly adding from a dropping-funnel a solution of 8 5 g. of sodium nitrite in 20 ml. of water con tinue the stirring for 20 minutes after the complete addition of the nitrite. 

Gently warm a mixture of 32 g. (32 ml.) of ethyl acetoacetate and 10 g. of aldehyde-ammonia in a 400 ml. beaker by direct heating on a gauze, stirring the mixture carefully with a thermometer. As soon as the reaction starts, remove the heating, and replace it when the reaction slackens, but do not allow the temperature of the mixture to exceed 100-no the reaction is rapidly completed. Add to the mixture about twice its volume of 2A -hydrochloric acid, and stir the mass until the deposit either becomes solid or forms a thick paste, according to the quality of the aldehyde-ammonia employed. Decant the aqueous acid layer, repeat the extraction of the deposit with more acid, and again decant the acid, or filter off the deposit if it is solid. Transfer the deposit to a conical flask and recrystallise it twice from ethanol (or methylated spirit) diluted with an equal volume of water. The i,4-dihydro-collidine-3,5-dicarboxylic diethyl ester (I) is obtained as colourless crystals, m.p. 130-131°. Yield 12 5 g,... 

Make a thin paste of 21 5 g. of finely-powdered o-tolidine (a commercial product) with 300 ml. of water in a 1-litre beaker, add 25 g. (21 ml.) of concentrated hydrochloric acid, and warm until dissolved. Cool the solution to 10° with ice, stir mechanically, and add a further 25 g. (21 ml.) of concentrated hydrochloric acid (1) partial separation of o tolidine dihydrochloride will occur. Add a solution of 15 g, of sodium nitrite in 30 ml. of water as rapidly as possible, but keep the temperature below 15° a slight excess of nitrous acid is not harmful in this preparation. Add the clear, orange tetrazonium solution to 175 ml. of 30 per cent, hypophosphorous acid (2), and allow the mixture to stand, loosely stoppered, at room temperature for 16-18 hours. Transfer to a separatory funnel, and remove the upper red oily layer. Extract the aqueous layer with 50 ml, of benzene. Dry the combined upper layer and benzene extract with anhydrous magnesium sulphate, and remove the benzene by distillation (compare Fig. II, 13, 4) from a Widmer or similar flask (Figs. II, 24, 3-5) heat in an oil bath to 150° to ensure the removal of the last traces of benzene. Distil the residue at ca. 3 mm. pressure and a temperature of 155°. Collect the 3 3 -dimethyldiphenyl as a pale yellow liquid at 114-115°/3 mm. raise the bath temperature to about 170° when the temperature of the thermometer in the flask commences to fall. The yield is 14 g. 

Preheat a water bath on the stove (or wherever) to about 80C and place the stainless steel mixing bowl in it. Once the temperature of the solution hits about 65C, take the bowl out and set aside while stirring all the while. This is where it rearranges, and the reaction is exothermic enough to sustain it s temperature nicely. If you find the temperature climbing past 80C, immerse the bowl into some cold waiter briefly. After about 15 minutes the temperature will start to fall, at which point you should transfer the whole mess to the distilling flask. Before you continue you need to choose whether you want to make the hydrochloride salt or the aqueous solution of Methylamine, though. 

Modem process facHities are computer controHed. Temperature and AT are programmed upward during the start of a growth cycle, pressure and temperature are monitored and controHed, and pressure and temperature overshoot alarms and overrides are provided. Such systems also store data from previous mns for correlations with properties or for identical repHcation of past conditions. 

The PEBC at the Tidd Station operates at 1200 kPa (170 psi) and a bed temperature of 860°C (51). A pressure vessel, 13.4 m in diameter by 20.7 m high, houses the combustor and its ancikafies. Coals, which contain ash contents less than about 25%, are blended with dolomite and pumped to the combustor as a paste having a total water content of 20—25%. Coals, which contain ash contents higher than 25%, and dolomite are individually fed pneumatically via separate lock hoppers. Both coal and dolomite are cmshed to 3-mm top size before being fed to the unit. 

The type of evaporator to be used and the materials of construc tion are generally selected on the basis of past experience with the material to be concentrated. The method of feeding can usually be decided on the basis of known feed temperature and the properties of feed and produc t. However, few of the listed variables are completely independent. For instance, if a large number of effects is to be used, with a consequent low temperature drop per effect, it is impractical to use a natural-circiilation evaporator. It expensive materials of construction are desirable, it may be found that the forced-circulation evaporator is the cheapest and that only a few effec ts are justifiable. 

Turbine-Blade Cooling The turbine inlet temperatures of gas turbines have increased considerably over the past years and will continue to do so. This trend has been made possible by advancement in materials and technology, and the use of advanced turbine bladecooling techniques. The olade metal temperature must be kept below 1400° F (760° C) to avoid hot corrosion problems. To achieve this cooling air is bled from the compressor and is directed to the stator, the rotor, and other parts of the turbine rotor and casing to provide adequate cooling. The effect of the coolant on the aerodynamic, and thermodynamics depends on the type of cooling involved, the temperature of the coolant compared to the mainstream temperature, the location and direction of coolant injection, and the amount of coolant. 

Example 1 shows the expander inlet conditions typical of past FCC applications with an expander inlet pressure of 30 psia and inlet temperature of 1,200°F. Example 2 shows the conditions prevalent in more recent FCC regenerator technology, where most of the CO is... 

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