Coke formation quenched coking

In the blast furnace, the reaction of the nitrogen in the blast with coke leads to the formation of poisonous chemicals such as hydrogen cyanide and cyanogens, and each cubic meter of the blast furnace gas contains from 200 to 2000 mg of these compounds. The blast furnace gas is scrubbed with water in the dust collection system the cyanide compounds dissolve in the water, which is then discharged after the compounds have been destroyed. Another poisonous emission in blast furnace operations is hydrogen sulfide. The sulfur present in the coke is converted into calcium sulfide in the slag, the water-quenching of... 

It is well known that pitch, solvent-refined coal (SRC), and coking coal produce various kinds of mesophase at the early stages of carbonization (3y 4y 5). The mechanisms of many chemical reactions and physical transformations relating to mesophase formation are studied by quenching techniques. Such research techniques as polarized-light microscopy can be extremely fruitful. On the other hand, observation of phenomena at reaction temperatures may yield more easily interpretable or more relevant results. 

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]. 

Coke formation will always be a potential problem in any high temperature process involving hydrocarbons. Coke and tars formed during reaction can deposit on reactor surfaces or in quench heat exchangers, and several effects have been observed in a steam cracker tube (4, 9 ). As the reaction proceeds the tube will accumulate coke towards the reactor exit, while the inlet zone remains relatively coke free, as a result of the induction time associated with the formation of tars and coke (J ). Gas phase reactants may adsorb and react on this bare metal, and the components of the gas phase in the reactor should and do reflect this interaction (4, 9, JO). Since carbon formation depends on the nature of the gas phase species, these interactions should also influence coke formation towards the exit of the ractor. Again, this is found to be the case (4, 9 - 11). 

Formation of Coke. Tracer and quenching studies were... 

AX21, a result that quenched the enthusiasm of the earlier report. Coke formation from styrene polymerization was recognized as one of the shortcomings of the reaction, leading to micropore plugging. No direct relationship could be found between the activity and the surface area of the carbon materials, and it was observed that the most active catalysts were those with more mesopores and higher external surface area. 

Figure 17.1 presents a simplified flowsheet, as developed in Chapter 7. Fresh raw materials mixed with recycled toluene and hydrogen is heated up to the reaction temperature. The reaction takes place in an adiabatic plug flow reactor. The reactor outlet is quenched with recycled hydrocarbon to prevent coke formation. Finally, the reaction mixture is cooled at 33 °C, and separated in a flash vessel in gas and liquid. 

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. 

Hot vapors from the coke drum are quenched by the liquid feed, thus preventing any significant amount of coke formation in the fractionator and simultaneously condensing a portion of the heavy ends that are then recycled. 

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