Table of Contents
Introduction.
Material Flow Analysis.
References
Catalysts play an instrumental role in oil refining industry. There are various kinds of catalysts , however, the main types of catalysts are reforming catalysts, fluid catalytic cracking catalysts and hydroprocessing catalysts. The impurities that contaminate catalyst during processing are nickel, vanadium, sulfur and coke (these components are present in crude oil feed). As a result, a catalyst deactivates with passage of time (Kim and Kim, 2018).
A life cycle of Diesel hydrodesulfurization catalysts have 3-4 years, however, FCC catalysts looses daily and they can be changed monthly depending on their activity. The catalyst is withdrawn from the process after completion of their life cycle. They are known as spent catalysts, spent catalyst is poisonous as it contains coke and heavy metals).
The total amount of spent hydroprocessing catalyst produce worldwide is 150,000-170,000 tons/year according to Dufresne estimation (Chiranjeevi et al., 2016). A projected annual increase in catalyst consumption is 5% (Chiranjeevi et al., 2016). An evaluation of projected spent catalysts generated globally and in Australia over the next 20 years is calculated in table 2
Table 1: amount of spent catalyst and projected annual increase (Chiranjeevi et al., 2016)
Amount of spent hydroprocessing catalyst produce worldwide (tons/year) |
150,000-170,000 |
Projected annual increase |
5% |
Table 2: An evaluation of projected spent catalysts generated globally and in Australia over the next 20 years
Year |
Spent catalysts generated globally and in Australia over the next 20 years (tons/year) |
1 |
160,000 |
2 |
168000 |
3 |
176,400 |
4 |
185,220 |
5 |
194,481 |
6 |
204,205 |
7 |
214,415 |
8 |
225,136 |
9 |
236,393 |
10 |
248,213 |
11 |
260,623 |
12 |
273,654 |
13 |
287,337 |
14 |
301,704 |
15 |
316,789 |
16 |
332,629 |
17 |
349,260 |
18 |
366,723 |
19 |
385,059 |
20 |
404,312 |
Therefore, the projected amount of spent catalyst that can product globally over the next 20 years is 404,312 tons/year.
Landfill is the traditional way for deposition of spent catalyst, however, it is not an environmental friendly method as this method causes contamination of ground water. To minimize generation of hazardous wastes, (Malekian, Salehi and Biria, 2019), the amount of spent hydroprocessing catalyst could be minimized if the life of catalyst prior to disposal can be extended for longer period of time. It can be done in the following ways
Catalysts deactivates with deposition of coke. To regenerate it, combustion is used to remove deposited coke). Catalyst activity recovers after repetitive combustion until desired activity is achieved. The temperature and oxygen concentration should be carefully controlled during coke burning.
A material flow analysis of fluid catalytic cracking unit is performed in attached excel sheet. A modern FCC consists of these three major units as shown in figure 1
The correlations given in table 3 are used to find product quantities in Fluid Catalytic Cracking unit (Abdalla, Elnour and Fayez Syed, 2016)
Table 3: Correlations to find quantity of products in Fluid Catalytic Cracking Units
Coke (wt%) |
0.0536 ×conv-0.18598×API+5.966975 |
LCO (light cycle oil) (LV%) |
0.0047×conv2-0.8564×conv+53.576 |
Gases (wt%) |
0.0552 ×conv+0.597 |
Gasoline (LV%) |
0.7754×conv-0.7778 |
iC4 (LV%) |
0.0007 ×conv2+0.0047×conv+1.40524 |
nC4 (LV%) |
0.0002 ×conv2+0.019×conv+0.0476 |
C4 olefin (LV%) |
0.0993 ×conv-0.1566 |
C3 (LV%) |
0.0436 ×conv-0.8714 |
C3 olefin (LV%) |
0.0003 ×conv2+0.0633×conv+0.0143 |
HCO (heavy cycle oil) |
100-conv-(LCO LV%) |
Wt % of S in Gases |
3.9678×(Wt% of S in feed)×+0.2238 |
Wt% of S in LCO |
1.04994×(Wt% of S in feed)×+0.00013 |
Wt% of S in HCO |
1.88525×(Wt% of S in feed)×+0.0135 |
S in coke (wt%) |
Wt% of S in feed-wt% of S in gases-wt% of S in LCO-wt% of S in HCO |
Gasoline API |
-0.19028×conv+0.02772×gasoline LV%+64.08 |
LCO API |
-0.34661×conv+1.725715×feed API |
Source: (Abdalla, Elnour and Fayez Syed, 2016)
Abdalla, A., Elnour, H. and Fayez Syed, K., 2016. MODELING AND DESIGN OF FLUIDIZED CATALYTIC CRACKING RISER. Graduation. Sudan University of Science & Technology.
Chiranjeevi, T., Pragya, R., Gupta, S., Gokak, D. and Bhargava, S., 2016. Minimization of Waste Spent Catalyst in Refineries. Procedia Environmental Sciences, 35, pp.610-617.
Kim, S. and Kim, S., 2018. Void Properties in Dense Bed of Cold-Flow Fluid Catalytic Cracking Regenerator. Processes, 6(7), p.80.
Malekian, H., Salehi, M. and Biria, D., 2019. Investigation of platinum recovery from a spent refinery catalyst with a hybrid of oxalic acid produced by Aspergillus niger and mineral acids. Waste Management, 85, pp.264-271.
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