Quench reactors

Reactor vapor quench. LCO, naphtha, or other quench streams can be used to quench reactor vapors to minimize thermal cracking. 

Chemical equilibria are frequently temperature dependent, and we should not expect that the organic phase trapped in the quenched catalyst will always be identical to that existing immediately prior to the quench. However, the organic material in the quenched catalyst should be sufficiently related to its antecedents that inferences about structures present at higher temperatures will be possible. Another advantage of the pulse-quench reactor that proved useful is the fact that products are removed from the catalyst bed in this experiment. This has proven useful for the observation of hydrolytically unstable species which form in reactions that also generate water (16). In sealed ampoules or rotors, the water can not escape the catalyst bed in the pulse-quench reactor, the water is swept out in the gas stream. Most of the experiments that motivated the calculations in this contribution were performed using "conventional" sealed-rotor methods, but the pentamethylbenzenium study (vide infra) would not have been possible without the pulse-quench reactor. 

In the Lurgi process a cooled tube reactor is applied. The catalyst particles are located in the tubes and cooling takes place by boiling water. The most important difference between the two reactor types is the temperature profile. In the Lurgi reactor it is much flatter than in a quench reactor. 

Another concern we have is the propagation of disturbances. Consider, for example, an increase in the quenched reactor effluent temperature, Ti (Fig. 5.17). We can use Eqs. (5.4) and (5.5) to estimate the effect that this temperature increase has on the streams around the preheater upstream of the furnace. If the bypass flow is small under normal operating conditions, we can assume that (mCP)g (rhCp)c ... 

Figure 5.17 HDA process illustration of disturbance propagation in quenched reactor effluent temperature.

For the reaction time of less than 1 sec, a special quick-heating quick-quenching reactor (SWQH-QQ) was developed by Ikushima et ah, as shown in Fig. 8. The organic stream is mixed with the preheated water stream using a T-joint so that the process stream is heated in merely 0.05 sec. The reactor is composed of a small tubing of 50 pL volume. After the reaction the mixture is again quickly quenched to stop the reaction. 

Fig. 2 shows I.C.I. cold-shot quench converter methanol loop which operates similar to the warm-shot loop. This adiabatic type quench reactor with its associated equipment is used when the syngas entering the methanol loop is stoichiometric or slightly carbon rich. It has the same adiabatic reactor profile as shown in Fig. 3. The main features of the cold-shot reactor loop are ...

The system actually is comprised of two reactors in series I. the plasma reactor, wherein high-temperature transient species are generated, followed by II. the quench reactor, wherein the plasma precursors are rapidly cooled within the cold-walled sampling tube to yield room-temperature stable products. 

In order to control heat removal and therefore the catalyst temperature, multiple-tube reactors (Lurgi process) or quench reactors with several catalyst layers and introduction of cold gas (ICI process) are mainly used. Catalyst performance in modern larger reactors is 1.3-1.5 kg of methanol per liter per hour, and large-scale plants have capacities of up to 10 fra, which reflects the position of methanol as a key product of Ci chemistry. 

This type of reactor contains several separate, adiabatically operated catalyst beds, allowing defined temperature control. Several methods of coohng are possible internal or external heat exchangers or direct cooling by introduction of cold gas (quench reactor). The multibed reactor is particularly suitable for high production capacities. 

Methanol synthesis by the high-pressure process CO/H2, 350-400 °C, 200-300 bar, Zn/Cr oxide catalyst, quench reactor. 

A four blade glass rectangle, specially made to fit the reactor, was used as a baffle system when desired. Figure 3 shows the reactor mixing configuration and the dimensions of the two types of impellers tested. A Sage Instruments model 355 syringe pump was used to feed the reaction solution to the quench reactor at a... 

Tests with catalysts containing copper were carried out by Imperial Chemical Industries Ltd., England, from about 1958 to 1962 and eventually a practical copper catalyst for methanol synthesis and the first Low-pressure Methanol Processes were brought onto the market. In the process developed by ICI the quench reactor, in which the reaction heat is removed by quenching with cold gases and which is known from high-pressure methanol synthesis, is used. 

Fig. 3.6. Temperature profiles in methanol reactors. Left) WatCT cooled tubular reactor right) quench reactor (saw tooth profile)...

The temperature gradient in the reactor, shown across the height of the overall catalyst chamber, gives the saw tooth diagram typical for quench reactors, as already shown in Fig. 3.6. Some of the reacted gas flows through the heat exchanger after it leaves the reactor where it heats the reactor feed. TTie sensible heat of the other portion is used for preheating feed water, as shown in Fig. 3.9, or to produce low-pressure steam. The gas cooled to about the methanol/water dew... 

A certain limitation in regard to its maximum size is dictated for the multistage quench reactor in view of the pressure drop at the catalyst [3.21]. For that... 

Figure 21 compares the thermal efficiency of this process and of the conventional multibed quench reactor operated at 100 bar. 

The salient advantages of the slurry process over conventional multibed adiabatic quench reactors are ... 

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