Directional quenching

Equipment. Partial-oxidation gasification section equipment in many plants consists essentially of (/) the gasification reactor (2) the waste-heat exchanger for heat recovery from the hot reactor gas or direct quench system (J) the economizer heat exchanger for further heat recovery (4) the carbon removal system for separating carbon from the reactor product gas and (5) the carbon recovery system for recycle of carbon. 

An iatermediate treatment that adds both carbon and nitrogen to steel surfaces can be obtained by exposiag the parts to a bath of molten cyanide at just above the critical temperature of the core for about one hour followed by direct quenching. The hardened area is about 0.25-mm deep. 

In an aqueous solution containing 26 and 27 the excited state of the Ru(II) complex in 26 essentially has no chance to be directly quenched by the donor quencher in 27, because a strong electrostatic repulsion acts between 26 and 27. Sassoon and Rabani added methoxydimethylaniline (MDMA, 28) to this system... 

The crude gas, which will contain some carbon particles, leaves the reactor at approximately 1300°C and passes immediately into a special waste-heat boiler where steam at 600 psig (4140 kN/m2 gauge) is generated. The crude gas leaves the waste heat boiler at 250°C and is further cooled to 50°C by direct quenching with water, which also serves to remove the carbon as a suspension. The analysis of the quenched crude gas is as follows ... 

Experimentally, temperature chaos can be evidenced by aging the system at a temperature T, and changing the temperamre to a T, + AT. If the temperamre shift is large enough, the equihbrium domain configurations at 7] and 7] + AT are completely different on the length scales relevant for the experiment. Hence, if the magnetic response at 7] + AT is the same as after a direct quench, the system appears rejuvenated. 

QUINAPHOS ligands are usually synthesized in a one-pot-procedure from readily available 8-substituted quinolines [8] via nucleophilic addition of a lithium reagent [9] to the azomethinic double bond and direct quenching of the resulting 1,2-dihydroquinoline amide 1 with a phosphorochloridite derived from enantio-merically pure binaphthol (1) or from 3,3 -di-t-butyl-5,5 -dimethoxybiphenyl-2,2 -diol (m) [10] (Scheme 2.1.5.1, Method A). Alternatively, the anion 1 can be reacted with an excess (in order to avoid multiple substitution) of phosphorous trichloride to obtain the corresponding phosphorous dichloridite 2, which can be isolated (Scheme 2.1.5.1, Method B). In a second step, 2 is converted into 4 by reaction with the desired diol in the presence of triethylamine. 

With directional quenching we present an effective mechanism to induce periodic stripe patterns in phase separating systems, where the wavelength of the patterns is uniquely selected by the velocity of a quench interface. If an additional spatially periodic modulation of the quench interface is introduced, cellular patterns can also be generated. 

Directional quenching is achieved by changing e from a negative value at x < xq to a positive one for x > xq, where the point xp(t) moves in the laboratory frame with the velocity v ... 

By this moving jump of the control parameter the system is divided into a stable and an unstable region. Numerical simulations of the ID model in (68) and with the directional quenching (69) show that a periodic solution develops behind the quench interface in the unstable region. Typical examples for large and small values of the... 

For systems where thermodiffusive effects can be neglected, we have presented results on the effects of directional quenching where the control parameter jumps the critical temperature from above to below and where the location of the jump is moved with a finite velocity v. We have shown how, by this method, regular structures are created during the process of phase separation behind the moving quench interface. Moreover, it was shown that the wavelength of periodic stripe patterns is uniquely selected by the velocity of the quench interface. If an additional spatially periodic modulation of the quench interface is introduced, cellular patterns can also be generated. 

Description Fresh feedstock and recycle streams are preheated and cracked in the presence of dilution steam in highly selective PyroCrack furnaces (1). PyroCrack furnaces are optimized with respect to residence time, temperature and pressure profiles for the actual feedstock and the required feedstock flexibility, thus achieving the highest olefin yields. Furnace effluent is cooled in transfer line exchangers (2), generating HP steam, and by direct quenching with oil for liquid feedstocks. 

The hydrocarbon mixture at the furnace outlet is quenched rapidly in the transfer line exchangers (2) (TLE or SLE), generating high-pressure steam. In liquid crackers, cracked gas flows to a primary fractionator (3) after direct quench with oil, where fuel oil is separated from gasoline and lighter components, and then to a quench water tower (4) for water recovery (to be used as dilution steam) and heavy gasoline production (end-point control). 

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