Heating zones

The evolved arsine is decomposed to arsenic and hydrogen at the heated zone of the delivery tube hence arsenic deposits as a shiny black mirror beyond the heated zone. 

Any refractory material that does not decompose or vaporize can be used for melt spraying. Particles do not coalesce within the spray. The temperature of the particles and the extent to which they melt depend on the flame temperature, which can be controlled by the fueLoxidizer ratio or electrical input, gas flow rate, residence time of the particle in the heat zone, the particle-size distribution of the powders, and the melting point and thermal conductivity of the particle. Quenching rates are very high, and the time required for the molten particle to soHdify after impingement is typically to... 

Usually not suited for materials smaller than 30 mesh. Material does not tumble, except in Roto-louvre dryer. Latter operates at higher temperatures Suited to smaller objects that can be loaded on each other. Can be used to convey materials through heated zones. Roto-louvre not suited. Not apphcahle Special designs are required. Suited to veneers. Roto-louvre not applicable... 

Heating zone, where the charge is heated to the reaction temperature, i.e., the decomposition temperature for limestone or burning temperature for cement... 

Residence time in heated zone Low Medium Low Medium... 

That the compound is not allowed to stagnate in heated zones of the extruder and thus decompose. The life of many compounds at processing temperatures is little more than the normal residence time of the material in the extruder. 

Styrene and solvent are blended together and then pumped to the top of the first reactor which is divided into three heating zones. In the first zone the solution is heated to start up the polymerisation reaction but because of the exothermic reaction in the second and third zones of the first reactor and the three zones of the second reactor Dowtherm cooling coils are used to take heat out of the system. By the time the reaction mixture reaches the third reactor the polymerisation reaction has started to slow down and so the reaction mixture is reheated. 

Friction welding Heat zone effect Heli-arc welding Pressure welding Spot welding... 

Joining Adhesive joining Bonding Cracking tendency Heat zone effect Welding... 

Gas velocity is measured over an aperture in the heated zone of the sampling train, at a temperature of 110 °C, to remove the moisture by heating. Determine the gas velocity at the sampling nozzle if the measured velocity is 28 m s for the sampling diameter used. The water concentration determined from the condensate is 75 g m" (n). 

Figure 4.1 Schematic diagram of a coupled column system. The first column (ID) is connected to the second column (2D) tlirough the interface or valve system. The interface can be a diiect coupling, a live T-union, a complex multiport valve, or a thermal or cryogenic modulation system. The stimulus can be the switching of the valve, abalancing pressure to divert flow towards 2D, an added flow that is used in pressure tuning, or the drive mechanism for the modulator. The line to detector 1 will normally be a non-retaining section of column. In a two-oven system, ID and 2D will be in different ovens the dotted line indicates separately heated zones.

Vertical thermosiphon Capable of very high heat transfer rates. Compact simple piping required. Low residence time in heated zone. Not easily fouled. Good controllability. Maintenance and cleaning can be awkward. Additional column skirt required. Equivalent to theoretical plate only at high recycle. 

Flooded-bundle (kettle) Easy maintenance and cleaning. Convenient when heating medium is dirty. Equivalent to theoretical plate. Contains vapor disengaging space. Lower heat transfer rates. Extra piping and space required. High residence time in heated zone. Easily fouled. 

Select an increment of vaporization, beginning at the end of the sensible heat zone. Use an average value of x for the increment calculations. The circulation rate that must be already developed on the basis of average conditions should be used for the initial calculations. 

This represents the fraction of the total available head between points A and B, which represents the sensible heating zone. This neglects liquid friction in the sensible zone and assumes the liquid level in the distillation column is maintained even with the top of the tubesheet. Equation 10-170 then gives the fractional tube length devoted to sensible heating. Refer to Figure 10-110 and note that ... 

At pressures greater than about 100 psig, the slope of the vapor pressure curve, (At/Ap) is low enough not to influence the sensible heating zone equation, as most of the tube is in vaporization. However, at low pressures and vacuum service, a large portion of the tube is in sensible heat. 

FaiH states that the second term in the preceding equation may be neglected. Fair reports that typical units show the sensible heating zone at 4-60% for AT = 20°F, and 4-49% for AT = 30°F for selected organics and also water. The values vary with pressure. Table 10-30. 

It will be assumed that the liquid level is maintained even with the top tubesheet. Neglecting inlet line friction, the sensible heating zone length may be estimated from Equation 10-176 ... 

There are different coating techniques. The woven and nonwoven fabrics normally involves three steps as it passes from the unwind roll to the rewind roll. Powder is metered onto the fabric, heated in an oven (gas or electric) that are usually divided into several heating zones, and cooled by a chill roll. 

At low pressures, NH3 is desorbed and HC104 is also volatilized. Both may rapidly diffuse from the heated zone and recombine elsewhere on the cool walls of the vacuum envelope as sublimate. The kinetics of sublimation, which may accompany the low temperature reaction [926], have been studied and discussed in detail [931,932]. The rate of this process is deceleratory throughout, empirically obeying eqn. (7) [931]... 

If at high temperatures (> 600 K) the volatilized NH3 and HC104 are prevented from leaving the heated zone by the presence of an inert gas, decomposition in the homogeneous phase follows. This is the high temperature (gas phase) reaction in which there is complete conversion of the reactant to volatile products and no residue remains. 

The system is evacuated to a pressure of 5-10 mm., and the tube is heated to 700°, measured at the center of the heated zone. 2-Chloro-2,3,3-trifluorocycIobutyl acetate is admitted at the rate of 10-20 g. per hour. From 70 g. (0.35 mole) of the cyclobutyl acetate there is obtained 62-68 g. of mixed solid and liquid condensate (Note 10). Fractionation through a 30-cm. column packed with glass helices affords 30-35 g. (60-70%) of 1-chloro-1,4,4-trifluorobutadiene (Note 11), b.p. 50-51°, 1-3870 18-22... 

To reduce the chance of side reactions, such as the dimerization of the diamine to tUjtw -diaminodihexylamine in (3.17) and the degradation of adipic acid to Schiff bases in (3.16), the precondensation can be carried out either for 30-60 min below 250°C or very rapidly (seconds) at 250-290°C. In the (pre)polymerization step, a concentrated PA salt solution is pumped into a set of heating tubes. These tubes have several heating zones as their diameter gradually increases in size.5,6,28... 

Methyl radicals were produced by pyrolysis of azomethane (CH3N2CH3). Azomethane was synthesized as describe earlier [18]. It was purified periodically by fteeze-pump cycles at 77 K, and the gas purity verified by RGA. The methyl radical source was similar to that developed by Stair and coworkers. [10, 11] The source was made of a quartz tube with 3 mm OD and 1 mm ID, resistive heating was supplied by means of a 0.25 mm diameter tantalum wire wrapped outside the quartz tube. The len of the heating zone was 4 cm, recessed from the end of the tube by 1 cm. An alumina tube around the outside of the heating zone served as a radiation shield. Azomethane was admitted to the hot tube at a pressure of 1x10-8 to 1x10-7 Torr via a high-vacuum precision leak valve. The pyrolysis tube was maintained at about 1200 K, adequate to decrease the major peaks in the mass sp trum of the parent azomethane at 58 and 43 amu by at least a factor of 100. 

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