Definition of Problem
A client wished to build a new refinery. It had already executed a marketing survey
in the area and could specify quantity and quality, together with prices, of the
products which would meet its market requirements. Its management now had to
decide the economic optimum refinery configuration that would satisfy its crude
and product slate. At this stage, only one type of crude was intended for the refinery,
and to some extent, this simplified the problem. However, to satisfy other considerations, management required the solutions to the following premises:
• The refinery configurations, which would satisfy a minimum investment, when
producing a high volume of gasoline with and without a low sulfur content
limitation of the fuel oil. All other products were to meet quality and quantity
requirements.
• The refinery configurations which would give the maximum return on investment to satisfy a fixed crude throughput with no quantity restriction on the
product slate and then to satisfy a limited restriction on the product slate with
no limit to the crude throughput.
Such a problem lends itself readily to linear programming, and thus, a refinery
simulation model was developed to solve these two premises.
Process Consideration
The first step in constructing the model was to establish as many processing units as
could conceivably contribute to the solution of the problem. For instance, with such
large requirements of gasoline, there would obviously be required a cracking unit of
some kind. Thus, the model included a reformer, fluid cracker, hydrocracker, coker,
and visbreaker. Some combination of these processes must satisfy the premises of
the problem.
Similarly, the lower sulfur content of the fuel oil would probably require some form
of residue treating. Thus, two severity desulfurizers for both short and long residue,
respectively, were included together with a process for hydrocracking these residues.
The many process units now included were then defined in terms of feed streams,
product yields and quality, and operating costs, all based as a percentage on the feed
streams. This part of the study was the first important step which required the
expertise of specialists. This data forms the basis for the rational solution to the
problem, and therefore, it was necessary to be accurate and to augment prediction
and theory with realism and technical experience.
For instance, in arriving at the yields from the crude and vacuum units, the effect
of fractionation on the product yield was considered. Realistic ASTM distillation
gaps were used that could be met by a commercial distillation unit.
In the fluid catalytic cracking units, a more sophisticated approach was needed to
correlate the yields from the many feedstocks which would be independent of
Petroleum Refinery Planning and Economics
775
A client wished to build a new refinery. It had already executed a marketing survey
in the area and could specify quantity and quality, together with prices, of the
products which would meet its market requirements. Its management now had to
decide the economic optimum refinery configuration that would satisfy its crude
and product slate. At this stage, only one type of crude was intended for the refinery,
and to some extent, this simplified the problem. However, to satisfy other considerations, management required the solutions to the following premises:
• The refinery configurations, which would satisfy a minimum investment, when
producing a high volume of gasoline with and without a low sulfur content
limitation of the fuel oil. All other products were to meet quality and quantity
requirements.
• The refinery configurations which would give the maximum return on investment to satisfy a fixed crude throughput with no quantity restriction on the
product slate and then to satisfy a limited restriction on the product slate with
no limit to the crude throughput.
Such a problem lends itself readily to linear programming, and thus, a refinery
simulation model was developed to solve these two premises.
Process Consideration
The first step in constructing the model was to establish as many processing units as
could conceivably contribute to the solution of the problem. For instance, with such
large requirements of gasoline, there would obviously be required a cracking unit of
some kind. Thus, the model included a reformer, fluid cracker, hydrocracker, coker,
and visbreaker. Some combination of these processes must satisfy the premises of
the problem.
Similarly, the lower sulfur content of the fuel oil would probably require some form
of residue treating. Thus, two severity desulfurizers for both short and long residue,
respectively, were included together with a process for hydrocracking these residues.
The many process units now included were then defined in terms of feed streams,
product yields and quality, and operating costs, all based as a percentage on the feed
streams. This part of the study was the first important step which required the
expertise of specialists. This data forms the basis for the rational solution to the
problem, and therefore, it was necessary to be accurate and to augment prediction
and theory with realism and technical experience.
For instance, in arriving at the yields from the crude and vacuum units, the effect
of fractionation on the product yield was considered. Realistic ASTM distillation
gaps were used that could be met by a commercial distillation unit.
In the fluid catalytic cracking units, a more sophisticated approach was needed to
correlate the yields from the many feedstocks which would be independent of
Petroleum Refinery Planning and Economics
775