Resid conversion

Reported residue conversion is significantly high for the five types of included reactors and largest for the slurry type of reactor. Besides, the slurry reactor together with the ebullated bed reactor can handle heaviest feedstocks and highest metal contents. Resid conversion requires higher temperatures, and pressure drop is essentially zero in these two reactors. However, product quality is better for the fixed and moving bed processes. 

Naber et al (9) have demonstrated that FCC still has a considerable potential to remain the (resid) conversion "workhorse" of the oil industry. At present about 45% of the world s crude can be envisioned to be within the frontiers of Resid FCC (figure 1). Apart from the importance of FCC feed pretreatment and FCC unit design, also the impact of FCC catalyst performance is crucial to allow the processing of heavier feeds. 

Although an increase in meso pore surface area and activity will result in an increase in conversion and resid conversion, Table IV also shows that there is no simple correlation between the observed catalyst properties and these results. Apparently other aspects such as pore size distribution and pore chemistry also play an important role. 

Hettinger et al (7) have presented this staged cracking concept as a useful model for FCC resid catalyst design (figure 4). Based on this model we can envision a very specific Pore Size Acidity Distribution (figure 5), which would be necessary to achieve an improvement in resid conversion. 

Table XIII. Resid conversion at constant coke...

It is interesting to see that a number of new resid conversion technologies were announced in the eighties. Most of these technologies lack success due to ... 

Veba Combi Cracking ( 89) Veba Resid Conversion 14 Yes... 

It is the polynuclear aromatic system and the heteroatom species that pose the greatest limitation to resid conversion. The polynuclear aromatic and heteroatom species 1) have high thermal stability 2) poison catalysts by deposition of heteroatoms and metals and 3) readily form coke that deposits on the catalyst and detracts from liquid production. 

Therefore, in a mixture as complex as petroleum, the reaction processes can only be generalized because of the difficulties in analyzing not only the products but also the feedstock as well as the intricate and complex nature of the molecules that make up the feedstock. The formation of coke from the higher molecular weight and polar constituents of a given feedstock is detrimental to process efficiency and to catalyst performance. One method by which the process chemistry can be rationalized is to separate the resid and its conversion products into fractions using solubility/ insolubility in volatile liquids as well as adsorption/ desorption on solids. In this way a number of resids and resid conversion products were separated into coke (toluene insoluble), asphaltenes (toluene soluble/ n-heptane insoluble), resins (n-heptane soluble, adsorbs on alumina), aromatics (n-heptane soluble, does not adsorb on alumina), and saturates (n-heptane soluble, does not adsorb on alumina). 

In this model, there are four common features that apply to resid conversion and these features are 1) an induction period prior to coke formation 2) a maximum concentration of asphaltenes in the reacting liquid 3) a decrease in the asphaltene concentration that parallels the decrease in heptane-soluble material and 4) the high reactivity of the unconverted asphaltenes. Thus, the model can be represented as ... 

Resid conversion is now in a significant transition period as the demand for transportation fuels increases. To satisfy the changing pattern of product demand, significant investments in resid conversion processes... 

Wiehe, I.A. A solvent-resid phase diagram for tracking resid conversion. Ind. Eng. Chem. Res. 1992, 31, 530. 

Wiehe, LA. Tutorial on Resid Conversion and Coking, Proc. 2" Inti. Conf. on refinery processing, AIChE 1999 Spring National Meeting, Houston, TX, March 14-18,499-505. 

Humbach et al. (1990) have reported resid FCC yields for Arabian Light atmospheric tower bottoms with the FCC in maximum gasoline mode (Figure 25). These yields should be contrasted with those for the VGO of a similar crude in maximum gasoline mode as given in Table 3. With the resid, conversion and gasoline yield is lower, but coke and C - gas make is higher. Typically the resid FCC will operate at about 980°F reactor temperature and 7 cat/oil. 

Kamienski, P., Wright, M., de Wit, M., Wakui, T. 2007. Maximize value of resid conversion with FLEXICOKING technology maximize technology. In BBTC Technology Conference, Athens, Greece, October 10-12. 

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