Immersion, heats

Liquid level is not automatically maintained in the vessel, and the vessel does not have an immersed heating element subject to excess temperature. 

Equipment downstream of liquid outlet(s) can safely handle maximum gas rates that can be discharged through the liquid outlet(s), and vessel does not have an immersed heating element subject to excess temperature. Restrictions in the discharge line(s) may be used to limit the gas flow rate. 

Martin, H., Heat Transfer Between Gas Fluidized Beds of Solid Particles and the Surface of Immersed Heat Exchanger Element, Parts I II, Chem. Eng. Process, 18 157-169,199-223 (1984)... 

In BSCR heat can be removed through the walls of immersed heat exchanger s tubes. The heat transfer coefficient in BSCR can be correlated, supposing that the hydrodynamic conditions may be satisfactorily represented by ug, // /, psi, Cp si, and As/ as ... 

In the case of solutions of flammable liquids having a boiling point below 100 °C, the stainless steel electrically-heated water bath or steam bath provided with a constant-level device must be used. The individual circular type is provided with a series of concentric rings in order to accommodate flasks and beakers of various sizes. A rectangular type, suitable for use in student classes, has several holes each fitted with a series of concentric rings. In both cases the water bath is fitted with an immersion heating element controlled by a suitable regulator. 

Compared to the fluidized bed, a spouted bed with immersed heat exchangers is less frequently encountered. Thus, the bed-to-surface heat transfer in a spouted bed mainly is related to bed-to-wall heat transfer. The bed-to-immersed-object heat transfer coefficient reaches a maximum at the spout-annulus interface and increases with the particle diameter [Epstein and Grace, 1997]. 

Roy and Fuerstenau153 and Mellgren154) determined the adsorption heat of long-chain surfactants on oxides with PDI H+ and OH" and with surfactants adsorbing as counterions in the EDL. The former authors153 studied the immersion heat of a-Al2C>3 in... 

Heat evolution during immersion processes involving surface rehydration has been found to occur over a 20- to 40-minute interval, so that high precision methods are required if immersion heats include a contribution due to rehydration. The immersion heat determinations were carried out in a microcalorimeter having a temperature sensitivity of 5 X 10 6° C., rapid thermal response, and carefully determined heat transfer characteristics. The calorimetric system has a demonstrated capability of handling heat input rates as low as 0.005 joule per second (15). Samples for immersion were contained in very thin-walled bulbs holding... 

The hazard involved in generalization with regard to thermal pretreatment conditions is further emphasized by the immersion heat characteristics of Silica SL. This material is characterized by a decreasing immersion heat over a very wide range of outgassing conditions. The maximum immersion heat is obtained follow-... 

There is, in addition, a readily recognizable rehydration rate dependence on the surface siloxane content. This is most apparent in the immersion heat data for silica FS, for which the time of slow heat evolution on immersion becomes appreciably longer for sample pretreatment temperatures above 225° C. Consideration of the precision of the calorimetric measurement with regard to slow heat input does not seem to have been afforded adequate attention. Immersion heat calorimeters constructed for the essentially instantaneous wetting heat measurement often do not perform adequately when heat is evolved slowly. 

At thermal pretreatment temperatures above 110° C., rehydration contributions are significant. The rehydration energy can be obtained from the increase in immersion heat values when the silica surface rehydrates completely to its stable surface state, and the heat of immersion determination is such that the total heat evolved, including that evolved slowly, is included in the measurement. 

The immersion heat curves for the three gel samples are shown as a function of surface hydroxyl content in Figure 3. Silicas SB and FS exhibit a linear relationship between hydroxyl content and immersion heat over segments of the total curve. The rehydration of silica SL is confined to a very limited silanol content. Rehydration energies, obtained from the straight-line portion of the immersion heat curves, are given in Table I. 

Figure 4 presents the immersion heats of two quartz materials in water as a function of pretreatment temperature. There is no decline in the immersion heat... 

On applying to the quartz A immersion heats the set of assumptions previously utilized with some success in evaluating the energy associated with rehydration of the gel surface, we obtain 2350 cal. per mole of bound water for the bound water reversibly lost during thermal pretreatment. This value is approximately half that for the average rehydration energy of the silica gel surface. 

Time of Immersion Heating (min) Concentration of Phenol [p] (mol/liter) Concentration of Lignin Units [L] (mol/liter) In [P]/[L]... 

The gas fluidized-bed reactor is the most efficient approach to pyrolysis. In this reactor the waste plastic is suspended around the heating medium and snbjected to pyrolysis by means of immersed heating tubes and gas-solid convective heat transfer. At present the only difficulty with this reactor is the problem of its structure. Fluidized-bed pyrolyzers have been designed for pyrolysis of waste tyre mbber in Taiwan and in Hangzon. A schematic apparatus of a fluidized-bed pyrolyzer is shown in Fignre 27.2. 

If a surface is wet by, but not chemically interacting with, a liquid of known surface tension, measurement of the heat of immersion (heat of wetting) can be related to the surface energy (Fowkes 1965). 

There are several different types of immersion heated that work well with this apparatus. 

This is a highly exothermic reaction that takes place in the gas phase in the presence of a CuCb catalyst. Small amounts of alkali and rare-earth metals in the catalyst inhibit by-product formation. The reactor is operated at 220-240°C and 2-4 bar. Immersed heat exchangers again remove the excess exothermic heat of reaction. 

---