Low-temperature long-time

Figure 3-7 Plot of nominal space times (or reactor residence times) required for several important industrial reactors versus the nominal reactor temperatiwes. Times go from days (for fermentation) down to milliseconds (for ammonia oxidation to form nihic acid). The low-temperature, long-time processes involve liquids, while the high-temperature, short-time processes involve gases, usually at high pressures.

LTLT (low temperature, long time) HTST (high temperature, short time) Fore warming (for sterilization)... 

Grigioni G. M., Margaria C. A., Pensel N. A., Sanchex G., and Vandagma S. R., Warmed-over flavonr analysis in low-temperature-long time processed meat by an electronic nose. Meat Science, 56, 221, 2000. 

L.F. Moreno-Perez, J.H. Gasson-Lara, and E. Ortega-Rivas, Effect of low temperature-long time blanching on quality of dried sweet potato. Drying Technol., 14(7-8) 1839-1857... 

Low-temperature long-time (LTLT) pasteurization Procedure in which milk is heated to 62.0°C for at least 30 min. 

Low-temperature long-time (LTLT) blanching (65-70°C for 15-20 min) was found to improve the... 

At low temperature, mixing times of about 1 s are excessively long. This can be seen from the buildup curve for geminal pair GlyH /H , which reached saturation around 300 ms. 

Reaction of Ammonia with Various Sugars at Low Temperature (Long Reaction Time with No Catalyst)... 

In polymerization at low temperatures, the time required to form one polymer chain is long enough to consume one monomer fully and allow the subsequent addition of another one. Thus, it becomes possible to synthesize block copolymers, provided that the polymerization (especially when it is catalyzed by hafnocenes) starts with propylene and, after the propylene is nearly consumed, continues with ethylene. 

The rate of chemical reaction has units of moles/time-volume and is a function of temperature and composition. If the rate is high, as we would anticipate for a high-temperature oxidation or pyrolysis reaction, the time needed for a desired production rate is small Similarly, if the rate is low, a long time is needed. The reactor volume is determined by the reaction rate and amount of product to be manufactured. 

The necessity to find an adequate reduction method for the creep curves in the short-time region is obvious if we try to construct the function b (A,A ) from Figures 5 and 7 for creep times smaller than 0.1-0.3 t. Due to the extremely flat course of the creep curves at low temperatures, the time-age shift function without vertical shift is only accessible at very long creep times, i.e., at 50°C for creep times longer than 5 lO s. 

This is important in rubber technology because it means that a rubber that is above its transition temperature in some low rate, long time use could be below the transition temperature, and so become a breakable glass in some high rate, very short time use. 

For a long time the official specifications for diesel fuel set only a mciximum viscosity of 9.5 mm /s at 20°C. Henceforth, a range of 2.5 mm /s minimum to 4.5 mm /s maximum has been set no longer for 20°C but at 40°C which seems to be more representative of injection pump operation. Except for special cases such as very low temperature very fluid diesel fuel and very heavy products, meeting the viscosity standards is not a major problem in refining. 

Equilibration of the interface, and the establislnnent of equilibrium between the two phases, may be very slow. Holcomb et al [183] found that the density profile p(z) equilibrated much more quickly than tire profiles of nonnal and transverse pressure, f yy(z) and f jfz), respectively. The surface tension is proportional to the z-integral of Pj z)-Pj z). The bulk liquid in the slab may continue to contribute to this integral, indicatmg lack of equilibrium, for very long times if the initial liquid density is chosen a little too high or too low. A recent example of this kind of study, is the MD simulation of the liquid-vapour surface of water at temperatures between 316 and 573 K by Alejandre et al [184]. 

These studies at the same time aroused my interest in the mechanistic aspects of the reaetions, including the complexes of RCOF and RF with BF3 (and eventually with other Lewis acid fluorides) as well as the complexes they formed with aromatics. 1 isolated for the first time at low temperatures arenium tetrafluoroborates (the elusive (T-complexes of aromatic substitutions), although I had no means to pursue their structural study. Thus my long fascination with the chemistry of car-bocationic complexes began. 

Cakes are dried in low temperature, high humidity conditions for a long time in order to minimize strain and absorbency variabiUty. The continuing usage of the cake system almost a century after its invention owes much to the desirable strain-free yam arising from its washing and drying operations. 

Thermochemical Liquefaction. Most of the research done since 1970 on the direct thermochemical Hquefaction of biomass has been concentrated on the use of various pyrolytic techniques for the production of Hquid fuels and fuel components (96,112,125,166,167). Some of the techniques investigated are entrained-flow pyrolysis, vacuum pyrolysis, rapid and flash pyrolysis, ultrafast pyrolysis in vortex reactors, fluid-bed pyrolysis, low temperature pyrolysis at long reaction times, and updraft fixed-bed pyrolysis. Other research has been done to develop low cost, upgrading methods to convert the complex mixtures formed on pyrolysis of biomass to high quaHty transportation fuels, and to study Hquefaction at high pressures via solvolysis, steam—water treatment, catalytic hydrotreatment, and noncatalytic and catalytic treatment in aqueous systems. 

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