Vapor-line quench

Some months later a resourceful technical service engineer decided to use heavy cycle oil (HCO) instead of slurry oil in the vapor-line quench nozzle. I leave it to the reader to explain why the tower began to flood at its former rate, even though the vapor feed was desuperheated by the HCO in the reactor vapor line. The above calculations quantifying the bubble effect partially provide the answer. 

Coke deposits in vapor line Quenching vapor line Plugged trays Condensers fouled Low pumparound duty... 

Determine which section initiates flooding Desuperheating reactor vapor Bubble effect in slurry P/A Reactor vapor line quench... 

Since the mid-1980s, FCC technology licensors and a number of oil companies have employed a number of RTD s to reduce non-selective post-riser cracking reactions. Two general approaches have been used to reduce post riser cracking. The most widely used approach is direct connection of the cyclones to the riser and on to the reactor vapor line. The second approach is quenching the reactor vapors downstream of the riser-cyclones (rough-cut cyclones). 

Coke that builds up in the coke drum overhead vapor line is responsible for most of the back-pressure incidents. Operators find that tearing the insulation off these lines slows the rate at which coke deposits. A belter method is to inject a heavy slop oil quench, as shown in Figure 3-4, into the vapor line to retard coke formation. 

Coke drum overhead vapor valves are massive affairs. Switching a pair of 20-ft diameter drums may require the manipulation of four 18-in. and four 12-in. valves. Size aside, the vapor valves are difficult to open and close because of coke deposits on valve internal parts. Removing the insulation on piping upstream of the vapor valves or injecting a small liquid quench (typically 3 vol%) into the vapor line at the first 90° turn will help. 

Fresh reducing gas is generated by reforming natural gas with steam. The natural gas is heated in a recuperator, desulfurized to less than 1 ppm sulfur, mixed with superheated steam, further preheated to 620°C in another recuperator, then reformed in alloy tubes filled with nickel-based catalyst at a temperature of 830°C. The reformed gas is quenched to remove water vapor, mixed with clean recycled top gas from the shaft furnace, reheated to 925°C in an indirect fired heater, and injected into the shaft furnace. For high (above 92%) metallization a CO2 removal unit is added in the top gas recycle line in order to upgrade the quaUty of the recycled top gas and reducing gas. 

However, the optical train illustrated in Figure 22B allows the determination of fluorescence quenching. The interfering effect described above now becomes the major effect and determines the result obtained. For this purpose the deuterium lamp is replaced by a mercury vapor lamp, whose short-wavelength emission line (2 = 254 nm) excites the luminescence indicator in the layer. Since the radiation intensity is now much greater than was the case for the deuterium lamp, the fluorescence emitted by the indicator is also much more intense and is, thus, readily measured. 

Vapor quenching provides a method of bridging the miscibility gap which exists in many alloy systems, and makes a range of novel alloys available for study. Such films, of course, would not be ideal for catalytic studies. They could not be used at high temperatures, and indeed the heat of reaction might be sufficient to induce a transformation to a more stable structure. In addition, characterization by X-ray diffraction would be difficult, even for the crystalline films, because of line broadening by the small crystallites. Nevertheless, alloy films which are metastable above room temperature can be prepared, and their high surface area would... 

Hot Surfaces. The incomplete immersion of hot metal in quenching baths, the contact of flammable vapors and hot combustion chambers, hot dryers, ovens, boilers, ducts and steam lines all are frequent causes of flammable vapor fires. Care should be taken that material whose auto-ignition point is lower than the temperature sometimes reached by operating equipment be kept at a safe distance from such equipment. 

It is therefore possible to reduce magnesium oxide to the metal with coke above about 1600 °C (Fig. 17.8), even though there would be no intersection of the Ellingham lines for the oxidations of solid Mg and coke in an accessible temperature range. The practicability of producing magnesium in this way depends on rapid quenching of the Mg vapor below temperatures at which the reverse reaction... 

Vapor-phase nitration of paraffin hydrocarbons, particularly propane, can be brought about by uncatalyzed contact between a large excess of hydrocarbon and nitric acid vapor at around 400°C, followed by quenching. A multiplicity of nitrated and oxidized products results from nitrating propane nitromethane, nitroethane, nitropropanes, and carbon dioxide all appear, but yields of useful products are fair. Materials of construction must be very oxidation-resistant and are usually of ceramic-lined steel. The nitroparaffins have found limited use as fuels for race cars, submarines, and model airplanes. Their reduction products, the amines, and other hydroxyl compounds resulting from aldol condensations have made a great many new aliphatic syntheses possible because of their ready reactivity. 

After the addition of the tin(IV) chloride-etherate slurry is completed, the reaction mi.xture is allowed to warm slowly (over a period of at least 30 minutes) to —20°. The mixture is then quenched to —78°, and the reaction flask is removed from the vacuum line. The material in the —95° trap (mostly solvent) is discarded. The crude product in the —196° traps is combined and passed four times through a —112° trap (carbon disulfide slush) to remove traces of solvent. This procedure typically gives 0.020 mole (30% yield) of stannane %vith a vapor pressure of 17 mm. at —112°. 

Preparation of blast furnace coke involves the heating of metallurgical coal to 1,000-1,100°C in the absence of air in a battery of refractory brick-lined coke ovens. This is referred to as the by-product coke plant from the association of by-product recovery with coke formation. The coal charge is heated until all of the volatile matter has been vaporized and pyrolysis is complete, a process which takes 16-24 hr. The residual lumps of coke, still hot, are then pushed out of the oven through a quenching shower of water and into a rail car for final shipment. About 700 kg of coke plus a number of volatile products are recovered from each tonne of metallurgical coal heated. More details on the coking process itself are available [40]. 

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