Unit, rapid heat

Cl in conjunction with a direct exposure probe is known as desorption chemical ionization (DCI). [30,89,90] In DCI, the analyte is applied from solution or suspension to the outside of a thin resistively heated wire loop or coil. Then, the analyte is directly exposed to the reagent gas plasma while being rapidly heated at rates of several hundred °C s and to temperatures up to about 1500 °C (Chap. 5.3.2 and Fig. 5.16). The actual shape of the wire, the method how exactly the sample is applied to it, and the heating rate are of importance for the analytical result. [91,92] The rapid heating of the sample plays an important role in promoting molecular species rather than pyrolysis products. [93] A laser can be used to effect extremely fast evaporation from the probe prior to CL [94] In case of nonavailability of a dedicated DCI probe, a field emitter on a field desorption probe (Chap. 8) might serve as a replacement. [30,95] Different from desorption electron ionization (DEI), DCI plays an important role. [92] DCI can be employed to detect arsenic compounds present in the marine and terrestrial environment [96], to determine the sequence distribution of P-hydroxyalkanoate units in bacterial copolyesters [97], to identify additives in polymer extracts [98] and more. [99] Provided appropriate experimental setup, high resolution and accurate mass measurements can also be achieved in DCI mode. [100]... 

Acids act similarly and rapidly to permanently disrupt the glyeosidic bonds. Thus polysaccharides degrade to their original monosaccharide units when heated with aqueous acids. Enzymes catalyze this degradation and provide both plants and animals with a source of glucose. 

Small-volume ovens (100-500 cubic inches) for portable units and for single column isothermal units. These ovens seldom have the capability of rapid heating and cooling. 

The field of chemical process miniaturization is growing at a rapid pace with promising improvements in process control, product quality, and safety, (1,2). Microreactors typically have fluidic conduits or channels on the order of tens to hundreds of micrometers. With large surface area-to-volume ratios, rapid heat and mass transfer can be accomplished with accompanying improvements in yield and selectivity in reactive systems. Microscale devices are also being examined as a platform for traditional unit operations such as membrane reactors in which a rapid removal of reaction-inhibiting products can significantly boost product yields (3-6). 

A bonding process in which the surfaces to be united are subjected to non-continuous rapid heating, pressure being maintained after heating. flSO 472 ... 

The feedstock in hydrodealkylation units is heated to 1,200° F (650°C) in a preheat furnace before entering the reactor. Above 1,100°F (590°C), metal dusting or catastrophic carburization occurs on ail alloys that are otherwise suitable for the temperature conditions. The attack is very rapid and takes the form of round bottom pits. The surface of the remaining metal is heavily carburized. A small quantity of sulfur (0.05 to 0.5 wt%) in the form of hydrogen sulfide or mercaptan added to the feed will prevent attack. Aluminizing has also been used to prevent attack. 

The rapid heat transfer allows nearly isothermal operation with a defined residence time. Therefore, undesired side reactions can be effectively suppressed. The formation of hot spots within the reactor and reactor runaway during fast, highly exothermic reactions can be avoided. As a consequence, higher operating temperatures are attainable, and the same conversion can be achieved with a smaller reactor volume and less catalyst. The smaller unit size in turn improves the energy efficiency, reducing the operational cost. 

Similarly, when the pyrolysis behavior was studied in a rapid heating unit with a heatup time of one to two minutes, virtually identical residue yields were obtained. 

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