Adiabatic cracking

Adiabatic Cracking Reactor. This principle is based on the injection of hydrocarbon feedstock into the flue gas at elevated temperatures. 

M. Dente, E. Ran2i, and S. Barendregt, "Adiabatic Cracking Yields Theoretically Predicted," paper presented stHIChE Meeting, New Orleans, July 1981. 

Adiabatic cracking reactor, 10 617-618 Adiabatic decomposition, of hydrogen peroxide, 14 61-62 Adiabatic dehydrogenation, 23 337 Adiabatic dehydrogenation unit, 23 339 Adiabatic evaporation, general separation heuristics for, 22 319 Adiabatic flame temperature, 12 322 Adiabatic flash calculation, 24 681 Adiabatic nitration process, 17 253—255 Adiabatic pressure-reducing valve,... 

The search continues for better and more economical processes for the production of ethylene. Those processes include catalytic thermal cracking, methanol to ethylene, oxidative coupling of methane, advanced cracking technology, adiabatic cracking reactor, fluidized bed cracking, membrane reactor, oxydehy-drogenation, ethanol to ethylene, propylene disproportionation, and coal to ethylene. Much work is still needed before any such process can compete with current processes. 

Example 5.6 Hydrocarbon cracking reactions are endothermic, and many different techniques are used to supply heat to the system. The maximum inlet temperature is limited by problems of materials of construction or by undesirable side reactions such as coking. Consider an adiabatic reactor with inlet temperature Tm. Then T z) < T, and the temperature will gradually decline as the reaction proceeds. This decrease, with the consequent reduction in reaction rate, can be minimized by using a high proportion of inerts in the feed stream. 

Trickle Hydrodesulfurization A process for removing sulfur-, nitrogen-, and heavy-metal-compounds from petroleum distillates before catalytic cracking. The preheated feed is hydrogenated, without a catalyst, in an adiabatic reactor at 315 to 430°C. Developed by Shell Development Company. As of 1978, 91 units had been installed. 

During the strike, the sulfur plant was shut down for minor repairs. I had to supervise its start-up. Mainly, I had to reheat the adiabatic-combustion chamber to 1800°F, before restoring the flow of H2S. This was done by burning a controlled amount of methane or natural gas, with a carefully regulated flow of air. The idea was to slowly heat up the combustion chamber with hot flue gas by 100 to 200°F per hour. This slow reheat was needed to avoid cracking the refractory bricks, because of uneven heating. To carry away a portion of the heat of combustion of the natural gas, we used pipeline nitrogen. 

The cuprous-cupric electron transfer reaction is believed to be the rate-limiting step in the process of stress corrosion cracking in some engineering environments [60], Experimental studies of the temperature dependence of this rate at a copper electrode were carried out at Argonne. Two remarkable conclusions arise from the study reviewed here [69] (1) Unlike our previous study of the ferrous-ferric reaction [44], we find the cuprous-cupric electron transfer reaction to be adiabatic, and (2) the free energy barrier to the cuprous cupric reaction is dominated in our interpretation by the energy required to approach the electrode and not, as in the ferrous-ferric case, by solvent rearrangement. 

The extremely high energy dissipation in the craze layer, 5 X 108 ergs/gram, would lead to an adiabatic temperature rise of about 24°C during crack/craze propagation, which is insufficient to cause most matrix polymers to pass through their T0 at usual environmental temperatures. Introduction of rubber particles can only lower this temperature rise since rubber secant modulus is very low and rubber deformation does not exceed the 300% or so of the deformed matrix. 

The changes in crack propagation types (from stable to stick-slip) are associated with the crack blunting mechanism, which is favored by high temperatures and low strain rates, conditions that decrease general trends cannot be extended to very high strain rates because a transition from isothermal to adiabatic conditions may... 

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