Notes

EFOM Documentation

October 2018
1 Introduction
This document is the description of the Ethylene Furnace Optimization Model
(EFOM) which is being used in PETKIM Ethylene Plant.
It consists of general methodology of the optimization, explanation of the
model code and mathematical formulation of the optimization model.
2 General Methodology
2.1 Ethylene Plant Process
Ethylene Plant in PETKIM processes Naphtha and LPG into several dierent
end products which mainly are:
 Ethylene
 Propylene
 C4
 Py-Gas
 Ethane
 Methane etc.
Each end product has dierent (and constantly changing based on the market
movements) nancial value and production capacity in the plant, therefore in
order to maximize the plant pro tability production trade-os between end
products should be considered.
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The complexity of the production trade-os arises from the fact that ratio
of the each product in end portfolio changes based on processed feed stock
speci cations and furnace operating conditions. In this project we could not
change the feed stock speci cations, therefore the focus was optimizing the
furnace operating conditions.
2.1.1 Ethylene Plant Furnace Operations
Ethylene plant in PETKIM has 10 furnaces (3 dierent kind) where the reaction
of processing feed stock into end products occur. Each furnace has 3 dierent
operating conditions which de ne what will be the end product portfolio coming
out of the furnace.
1. Feed Level: Refers to the level of feed stock processed in the furnace
2. Coil Outlet Temperature (COT): Refers to the operating temperature
of the furnace
3. Dilution Steam (DS): Refers to the ratio of steam / feed stock used in
process of cracking in the furnace
This study focuses on nding optimal operating conditions for the furnaces
which will maximize the total value generated in the plant.
2.1.2 Feed Stock Speci cations
Ethylene plant in PETKIM can process 3 dierent feed stocks which are:
1. Naphtha: Naphtha is the main feed stock of the ethylene plant which
consists of +95% of the total consumption. It has 10+ speci cations most
important of them being paran level, iso-paran level, boiling points,
etc.
2. LPG: Similar to naphtha LPG can also be cracked in the furnaces. It
also has 10+ dierent specs, some of the most important of them being
propane level, n-butane level.
3. Ethane: Dierent than naphtha and LPG, ethane is not procured and
fed into the system. Ethane is one of the output products of naphtha and
LPG cracking, but it never leaves the system and is recycled to the system
to be cracked again in the ethane furnace.
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2.1.3 Plant Bottlenecks
Apart from the furnaces, ethylene plant has production capacity for individual
or some group of materials. When maximizing the value generation, these limits
should be considered in order the maintain sustainable production. In this study
this is enabled with mathematical modeling which will be further explained in
the following sections.