Reaction quench systems

The means by which a quench system works depends on the nature of the reactive material e.g., for water-reactive materials, a quench system will destroy the material in a last-resort situation and generally form less-hazardous products, and will at the same time absorb some of the heat of reaction. Most quench systems are designed to both cool down and dilute a material that may be reacting uncontrollably the quenching medium may also actually interfere with the chemical reaction or deactivate a catalyst. 

Dump Systems For an inhibitor injection or quench system, the inhibitor or quenching medium is transferred from an external supply to the reactive material in a dump system, the reactive material is transferred from the storage/handling facility to a safer location that is the same size or, more commonly, larger than the normal capacity of the facility. This allows depressurizing and deinventory of the reacting mass from the facility in an out-of-control situation, such as an incipient runaway reaction. 

A reaction quench is a system where an inhibiting substance (quench solution stored in a separate container vessel) can be quickly and effectively fed into the reactor via a pipe which is protected with appropriate isolation valves. This action is independent of other process actions that may be required. The reaction quench can be manually initiated or automatically when certain process parameters are exceeded. 

In the process (Figure 9-37), the residue feed is slurried with a small amount of finely powdered additive and mixed with hydrogen and recycle gas prior to preheating. The feed mixture is routed to the liquid phase reactors. The reactors are operated in an up-flow mode and arranged in series. In a once through operation conversion rates of >95% are achieved. Typically the reaction takes place at temperatures between 440 and 480°C and pressures between 150 and 250 bar. Substantial conversion of asphaltenes, desulfurization and denitrogenation takes place at high levels of residue conversion. Temperature is controlled by a recycle gas quench system. 

For extremely exothermic reactions, emergency quench systems are sometimes used to protect against a runaway reaction. If the reactor temperature exceeds a predetermined maximum safe temperature, the reactor contents are rapidly... 

Reaction quench or chemical short stop systems to stop or slow the reaction by removing heat sources, cooling the reactants, deactivating any catalyst, or interfering with reaction chemistry ... 

Hydrogen cyanide, H-C=N , is a colorless, extremely toxic, volatile liquid, mp -13.4°C, bp -1-25.6 °C, with a high dielectric constant (107 at 25 °C). It functions as a weak acid Ka = 4.9 x 10 °). It is made by acidifying aqueous solutions of cyanides or industrially by the exothermic reaction of methane with ammonia in a fast flow/rapid quench system (equation 16). Hydrogen cyanide polymerizes readily nnder a variety of conditions hydrogen cyanide oligomers include the trimer aminomalononitrile and the tetramer diaminomaleonitrile (Figure 8). 

Highly elaborate architectures, such as 346 could be prepared from 344 and 345 using the Sonogashira reaction. These systems could be used as hgands for intramolecular electron-transfer quenching systems [121]. 

In the Texaco process, if the desired product is hydrogen, the raw syngas leaving the reactor is cooled with a direct-water-quench system. In this way, the steam necessary for the downstream shift reaction is produced in situ. A simplified flow diagram depicting the process flow scheme with the direct-quench cooling system is shown in Figure 13 [17). 

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