Metallic coke

Aromatics Sulfur Nitrogen Metals Coke -Paraffins Olefins ... 

A major fire that resulted in 65 million in property damages occurred early in the morning (4 21 A.M.) on August 2, 1993. The central unit of three delayed coker units was the origin of the fire. Each of the three units consisted of four 100-ft. metal coke drums mounted about 40 ft. above grade. The sustained, intense fire caused other pipes in the area to rupture, releasing more hydrocarbons. Over 95 fire brigade members battled the fierce fire for nearly three hours. [21] The fire killed three people. 

Pyrolysis is an ancient method of decomposing solid matter by heating to high temperatures examples are production of metals, coke furnaces, and obtaining of chemicals from coal prior to petroleum. There are many kinds of pyrolysis batch, semi-batch or continuous catalytic or non-catalytic out under vacuum or at atmospheric or high pressure. Its medium may be inert, oxidative or reductive. Heating rate, temperature, and time are important pyrolysis parameters. 

The results obtained during the helium stripping Indicate that some of the coke was removed. The TPO performed after this experiment shows that the coke removed was the metal coke (4), and the shoulder of the high temperature peak. In our case the metal coke is represented for the coke burnt below about 400<>C but the peak was not resolved. However it can be clearly seen in section 4 samples as a small peak (see Figure 5B, label D). 

The TPO results depicted in Fig.7 further illustrates the plausibility of the above supposition in that an increased metal content indeed enhances the overall coke deposition. It is generally accepted that the low-temperature peak ( 370°C) corresponds to coke deposited on, or in contact with the metal site. The intermediate temperature peak, 445°C, is associated with the coke on the acid sites close to the metal. The 570°C peak is produced by coke on the acid sites far away from any metal site [4, 11-13]. Since most of the coke deposits on acid sites and at a high coke level, the shoulder of the acid-coke peaks in Fig. 7 obscures the peaks for the metal-site coke, but one can see that the coke on acid sites near or far away from metal sites increases with increasing metal loading. The absence of a distinct metal-coke... 

Two sorts of coke are formed on the metal (Pt/Re) and the acidic sites (AI2O3), respectively, with the latter being much less reactive. At the beginning of decoking, the small amount of metal coke (e.g., 2% of the total carbon for Lc,o = 0.15g(-g 5) is rapidly burned off. To model the decoking process, only the type of coke on alumina, which is dominant (with respect to the amount) and less reactive, has to be considered. 

Catalyst activity decay due to kinetic and metal coke on catalyst... 

Coke Kinetic coke (produced by reaction scheme) Metal coke (produced by metal activity on catalyst)... 

Another important consideration in the FCC unit model is the deactivation of catalyst as it circulates through die unit Previous work has used two different approaches to model catalyst activity time on stream and coke on catalyst [49]. Since the 21-lump includes discrete lumps for the kinetic and metal cokes, this work uses a coke-on-catalyst approach to model catalyst deactivation. In addition, this work includes a rate equation in the kinetic network for coke balance on the catalyst. The general deactivation function due to coke, coke> is given by Eq. (4.4). 

Vary the reaction selectivities for reaction paths (3 parameters) that lead to coke lumps (kinetic coke and metal coke), gasohne (G lump) and VGO (PH, NH, AHs, AHrl, AHr2 and AHr2 lumps) deactivation activity factors (2 para-... 

KcoKE Deactivation function due to kinetic coke, unitless McoKE Deactivation function due to metal coke, unitless Qcoke Kinetic coke on catalyst, kg kinetic coke/kg catalyst Cmcoke Metal coke on catalyst, kg metal coke/kg catalyst METALS Metals composition on catalyst ppm metals/kg catalyst kcoke Activity factor due to kinetic coke, unidess mcoke Activity factor due to metal coke, unidess E Murphree stage efficiency factor... 

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