Petroleum coke (pet coke) is one of the many products manufactured during the oil refining process. During the refining process, a number of fractions including gasoline, diesel fuel, jet fuel, lubricating oils and waxes are separated leaving behind reduced or heavy crude that cannot be recovered without further processing. The residue crude may be refined using a delayed coker to break large carbon molecules to produce petroleum coke. Pet coke is typically used as a source of energy, or as a source of carbon for industrial application. There is an increasing demand of pet coke in coal industry (due to its high calorific value) which could be mixed with low to medium grade coals to get coals with desired (high) calorific value. Therefore, the composition of the volatile matter of pet coke (which contributes to the calorific value) is of utmost importance in order to judge its burning properties. We carried out this study in order to gain some insight into the composition of volatile matter of pet coke. The volatile matter of pet coke generally consists of aliphatic and aromatic hydrocarbons in addition to methane, hydrogen, carbon dioxide and carbon monoxide.
Experimental and Results
Previous literature study on the determination of volatile matter composition of pet coke revealed the release of methane, carbon dioxide and hydrogen gases when heated at 300°C whereas aliphatic hydrocarbons were liberated above 400°C.1 The gravimetric heat losses were measured from 200-1000°C without taking into account the volatiles which could be liberated below 200°C as they considered the heat loss upto 300°C was due to entrapped air. However, in this present work, heating pet coke upto 210°C revealed the presence of low volatile aromatic hydrocarbons which were not accounted for in the previous literature study. Gradual heating of the sample upto 210°C in Headspace and measuring the volatile matter content using GC-MS revealed the following compounds:
- Ortho, meta and para-xylenes
- Other aromatic hydrocarbons
This work gives insights into the volatile matter composition of pet coke below 210°C which, to the best of our knowledge, was not documented previously in the literature. The volatile matter composition obtained after heating the pet coke sample at 210°C revealed primarily low volatile aromatic compounds which contributes to the calorific value. Liberation of other constituents of volatile matter like aliphatic hydrocarbons, methane, carbon dioxide and hydrogen take place at a much higher temperature and is well documented in literature.
- K Dawat and L.R Duara, Characterisation of volatile matter in raw petroleum coke and possibilities of in situ utilization of better yield and properties of calcined product.
Contributed by : Satirtha Sengupta