5 research outputs found
Multifunctional Two-Stage Riser Catalytic Cracking of Heavy Oil
The continuous deterioration of feedstocks, the increasing
demand
of diesel, and the increasingly strict environmental regulations on
gasoline call for the development of fluid catalytic cracking (FCC)
technology. To increase the feed conversion and the diesel yield as
well as produce low-olefin gasoline, the multifunctional two-stage
riser (MFT) FCC process was proposed. Experiments were carried out
in a pilot-scale riser FCC apparatus. Results show that a higher reaction
temperature is appropriate for heavy cycle oil (HCO) conversion, and
the semispent catalyst can also be used to upgrade light FCC gasoline
(LCG). The synergistic process of cracking HCO and upgrading LCG in
the second-stage riser can significantly enhance the conversion of
HCO while reducing the olefin content of gasoline at less expense
of gasoline yield. Furthermore, the novel structure riser reactor
can increase the conversion of olefins in gasoline. Because of the
significant increase of HCO conversion, the fresh feedstock can be
cracked under mild conditions for producing more diesel without negative
effects on the feed conversion. Compared with the TSR FCC process,
in the MFT FCC process, the increased feed conversion, diesel and
light oil yields can be achieved, at the same time, the olefin content
of gasoline decreased by approximately 17 wt %
In Situ Upgrading of Light Fluid Catalytic Cracking Naphtha for Minimum Loss
The key to reducing the olefin content
in fluid catalytic cracking (FCC) gasoline is to upgrade the olefin-rich
light FCC naphtha (LCN). To minimize the naphtha loss, several parameters
were investigated in a pilot-scale riser FCC apparatus. The results
indicate that, besides the reaction temperature, the catalyst-to-oil
ratio, and the catalyst type, the boiling range and the olefin content
of LCNs also have significant influence on the upgrading effect. Moreover,
a relatively short residence time is beneficial for efficiently upgrading
LCNs. In addition, the influence of the reactor structure should be
brought to our attention. When a novel structurally changed reactor
with a multinozzle feed system was used, significantly increased olefin
conversion and decreased naphtha loss can be achieved. The calculation
of hydrogen balance indicates that, because of the decrease of dry
gas and coke yields, more hydrogen in the feed can be distributed
into the desired products
Fluid Catalytic Cracking Study of Coker Gas Oil: Effects of Processing Parameters on Sulfur and Nitrogen Distributions
To
investigate the effects of operating conditions and the catalyst
activity on the transfer regularity of sulfur and nitrogen during
the cracking process of coker gas oil (CGO), the CGO was catalytically
cracked in a pilot-scale riser fluid catalytic cracking (FCC) apparatus
at different test environments. Then the cracked liquid products were
analyzed for sulfur and nitrogen distributions with boiling point,
from which the sulfur and nitrogen concentrations of gasoline, light
cycle oil (LCO), and heavy cycle oil (HCO) fractions were determined.
The sulfur and nitrogen compounds in each product cut, and their possible
reaction pathways were reviewed and discussed. The results show that
sulfur-containing species are easier to crack but more difficult to
be removed from the liquid product, while nitrogen compounds are easier
to form coke, then be removed from the liquid product. The sulfur
distribution of CGO is different from that of conventional feedstocks.
Different processing parameters can significantly affect the sulfur
and nitrogen distribution yields and concentrations in liquid products.
Increasing the reaction temperature and the catalyst-to-oil ratio
as well as shortening the residence time cannot only increase the
light oil yield but also improve the product quality and reduce the
SO<sub><i>x</i></sub> and NO<sub><i>x</i></sub> emissions in the regenerator
Vacuum Residue Thermal Cracking: Product Yield Determination and Characterization Using Thermogravimetry–Fourier Transform Infrared Spectrometry and a Fluidized Bed Reactor
To make full use
of heavy oil by thermochemical conversion, the
thermal behaviors of vacuum residue (VR) were investigated first by
thermogravimetry–Fourier transform infrared spectrometry (TG–FTIR)
and then via a laboratory-scale fluidized bed reactor (FBR). The TG–FTIR
results showed that the changes in the absorbance of volatiles during
thermal cracking were consistent with the weight loss in the derivative
thermogravimetric curve. The dynamic information about the release
profiles of the typical gaseous products such as CO, CO<sub>2</sub>, CH<sub>4</sub>, C<sub>2</sub>H<sub>4</sub>, light aromatics, and
aliphatic olefins revealed the cleavage of varied structures and functional
groups of VR at different temperatures. Moreover, the peaks for the
maximum releasing rate on the evolving profiles of gaseous products
became narrower and sharper, and the yield at maximum releasing rate
for the gaseous species increased with increasing the heating rate.
The pyrolysis experiments in a FBR with silica sand as a heat carrier
showed that alkenes were the dominant gaseous products, with light
olefin selectivity higher than 53%. The coke/Conradson carbon residue
ratio was lower than that in the delay coking process. Furthermore,
analysis of liquid oil using gas chromatography/time-of-flight mass
spectrometry showed that 1-alkenes was the most abundant decomposition
product and the selectivity of total olefins from C<sub>6</sub> to
C<sub>22</sub> was 62.74%
Synergistic Process for Coker Gas Oil Catalytic Cracking and Gasoline Reformation
The most critical problem of processing coker gas oil
(CGO) is
its high nitrogen content, especially the basic nitrogen compounds,
which limits its cracking performance in the fluid catalytic cracking
(FCC) process. For enhancing the conversion of CGO, three processing
schemes were evaluated in a pilot-scale riser FCC unit. Four indexes
(thermal cracking index, dehydrogenation index, hydrogen transfer
coefficient, and isomerization reaction index) were used to investigate
the effects of operating conditions on the reactions of CGO cracking.
Results show that the optimal operating conditions for CGO cracking
are high reaction temperature and large catalyst-to-oil ratio with
a short residence time. Therefore, we proposed a synergistic process
by selectively recycling light FCC gasoline (LCG) from the upper position
of the riser reactor, which can provide a high-severity reaction zone
for CGO cracking and a low-severity reaction zone for gasoline upgrading.
To further investigate the mutual effect of the two feeds, different
recycle ratios of LCG were tested. Results indicate that the conversion
of CGO significantly increased with the LCG recycle ratio. When the
recycle ratio reached 50 wt %, the gasoline could be upgraded at a
higher efficiency. To ensure the optimal recycle ratio and improve
the gasoline quality, a two-stage synergistic (TSS) process was proposed.
The simulated experiments of the TSS process show that the higher
conversion and more desired products can be achieved, even though
under a high processing ratio of CGO to conventional feeds