(462f) Graphic Synthesis Method for Multi-Technique Integration Separation Sequences of Multitudinous Refinery Gases

Graphic Synthesis Method for
Multi-technique Integration Separation Sequences of Multitudinous Refinery
Gases

Xuehua
Ruan, Hongyan Xiao, Xiaobin Jiang, Xiaoming Yan, Yan Dai, Gaohong He

School of Petroleum and Chemical Engineering, State Key
Laboratory of Fine Chemicals, Dalian University of Technology, Panjin,
Liaoning, P.R. China, 124221

Corresponding
Author Email: hgaohong@dlut.edu.cn

In petroleum and
chemical industries, considerable crude oil, i.e., 3~8 %, is converted into
refinery gases and used as furnace fuels. Many valuable species in the refinery
gases, e.g., H₂, C₂H₆, C₂H₄,
C₃H₈ and C₄H₁₀, are depleted.
Currently, this wastage is going on increasing because more and more
hydro-processes are built up for refining heavy sour crude oils to high quality
products. Accordingly, the effective separation of valuable species from
refinery gases has been one of the most potential approach to improve crude oil
utilization percentage.

Nowadays,
some separation unit operations have been attempted to fractionate and reclaim
refinery gases, e.g., pressure swing adsorption, glassy polymer membrane
permeation and cryogenic condensation for recovering H₂, shallow
condensation, gasoline absorption and rubbery polymer membrane permeation for
concentrating light hydrocarbons, and distillation for further separating
hydrocarbons. Nevertheless, any simplex technique cannot fractionate all the
valuable components efficiently and sufficiently from multitudinous refinery
gases. It is necessary to integrate various techniques together as the hybrid
processes to achieve the recovery task. In this instance, a shortcut method is
established in this work to construct the multi-technique integration
processes, in which highly efficient separation unit operations are coupled
together within an optimal sequence to improve efficiency.

This
shortcut synthesis method is a graphic means based on expressing separation
units by vectors in composition space. Three supporting technical measures are
summarized:

1.  After
ranking components with their separation characteristics and belongings in
products, refinery gases are reduced to be pseudo-ternary mixtures of H₂,
light hydrocarbons and fuel gases, meanwhile the composition space is
visualized into triangular coordinate system.

2.  Based
on the efficiency analysis, dominant feed ranges for adsorption, condensation,
glassy and rubbery membrane separation are determined, in which the represented
technique could be more efficient than the others for the composition matched
refinery gases.

3.  Separation
operations, usually acting with the selectivity unique to a certain species
group, are estimated quickly by the shortcut calculations and then represented
with vectors in the triangular coordinate system.

The shortcut synthesis
method and its application for construct multi-technique integration systems
are sketched out in Figure 1.

The synthesis is launched by positioning the feedstock in the triangular coordinate system
according to the composition. According to the location of the feed stream, the
separation unit suitable to deal with this stream can be determined facilely by
matching with the dominant ranges. Afterwards, the shortcut calculations are
conducted by vector analysis to orientate the residue from a separation unit
and select the next separation unit.

Thanks
to running the separation unit operations in their preferred ranges and avoiding
the stream mixing with great composition difference, the multi-technique
systems designed by the expert synthesis approach can reclaim refinery gases
sufficiently and efficiently. For multitudinous refinery gases in large-scale
petrochemical complex, the overall recovery ratio for valuable species is
higher than 95 %, while the specific energy consumption is usually lower than
0.50 kWh/Nm³ refinery gases. The integration processes designed by
this means have been successfully industrialized in Sinopec and PetroChina.

Acknowledgement:

The
authors are grateful to the financial support from National Natural Science
Foundation of China (No. 21606035, U1663223, 21527812), Education Department of
the Liaoning Province of China (LT2015007), and Changjiang Scholars Program
(T2012049).