Package 2. Oil refining Refineries, Oil Refining Processes, Crude Oil Distillation Chemical Conversion Processes of Crude Oil Distillates Catalytic Cracking Hydrodesulphurisation Hydrotreating Isomerisation Reforming Hydrocracking Residue Conversion Processes Gasoline Upgrading
Refineries, Oil Refining Processes, Crude Oil Distillation
Chemical Conversion Processes of Crude Oil Distillates
Residue Conversion Processes
Integrated Refinery Structures
Environmental Protection in Refineries, BAT (Best Available Technique) and BREF (BAT Reference Documents) of Refineries
a) Crude desalter;
b) Crude heater;
c) Main fractionator;
d) Overhead accumulator;
e) Kerosene stripper;
f ) Light gas oil stripper;
g) Heavy gas oil stripper;
h) Vacuum heater;
i) Vacuum flasher
c) Regenerator; d) Riser; e1) Regenerator standpipe; e2) Stripper standpipe;
f) Cyclone vessel; g) Air blower; h) Flue gas expander; i) Waste-heat boiler;
j) Fractionator; k) Absorber;
l) Debutanizer; m) DepropanizerCatalytic cracking
Task: lowering molecular weight and boiling point
Co Mo Ni W
Active form: sulfided
Task: eliminating sufur content
a) Process heater; b) Reactor; c) High-pressure separator; d) Low-pressure separator; e) Stabilizer; f ) Gasoline splitter
a) Process heater; b) Reactor; c) High-pressure separator; d) Low-pressure separator; e) Gas oil stripper; f ) Gas oil dryer; g) Stripper overhead drum
Task: decreasing sulfur content
Task: stabilising the product, desulfurisation
a) First stage reactor; b) First stage separator; c) Depentanizer; d) Gasoline (heart cut) column; e) Second stage reactor; f ) Second stage separator; g) Debutanizer
Tasks: increase octane number, production of aromatics
Catalyst: Pt on alumina (alloyed with Sn)
Reactions during catalytic reforming:
Task: produce better quality distillates Catalysts: Co-Mo, Ni-W, sulfided
a) Hydrogen heater; b) First-stage reactor (hydrotreating); c) Second-stage reactor (hydrocracking); d) High-pressure separator; e) Hydrogen compressor; f ) Low-pressure separator; g) Fractionator
Task: increase the yield of high value products
„H-in” and „C-out” processes
a) Fractionator; b) Furnace; c) Coke drums; d) Gas oil stripper; e) Overhead accumulator
In most advanced refinery structures:
hydroprocessing + [ coking, deasphalting, hydrocracking ] + partial oxidation
The atmospheric residue feed is introduced to the fractionator (a) where it condenses some of the cracked vapors. The fractionator bottom product is heated in a tube furnace (b) to ca. 490 °C, and the cracked furnace effluent flows through one of the coke drums (c) in which coke is being formed and deposited. The cracked vapors from the coke drum are separated further in the fractionator. In a 24 h cycle, one of the coke drums is in use while the other is emptied by means of a hydraulic coke removal procedure.
The introduction of the fluid coking process brought the advantage of continuous operation, thus avoiding alternate use of the coke drums. The cracking reactions occur at 500 – 550 °C in the reactor in a fluid bed of coke particles into which the residue feed is injected. Coke fines are removed from the cracked vapors in cyclone separators before fractionation. The coke formed in the reactor flows continuously to the heater, where it is heated up to 600 – 650 °C by partial combustion in a fluid bed. The heated coke particles are returned to the reactor, from where the net coke production is withdrawn.
Task: producing better fuel, high octane number, no health risk, environmentally more friendly
Processes: alkylation, polymerisation, isomerisation
) Reactor; b) Settler; c) Isostripper; d) Depropanizer; e) HF stripper
The term light crude processing‘best available techniques’BAT is defined in Article 2(11) of the Directive as “the most effective and advanced stage in the development of activities and their methods of operation which indicate the practical suitability of particular techniques for providing in principle the basis for emission limit values designed to prevent and, where that is not practicable, generally to reduce emissions and the impact on the environment as a whole.”
Article 2(11) goes on to clarify further this definition as follows:
· “techniques” includes both the technology used and the way in which the installation is designed, built, maintained, operated and decommissioned;
“available” techniques are those developed on a scale which allows implementation in the relevant industrial sector, under economically and technically viable conditions, taking into consideration the costs and advantages, whether or not the techniques are used or produced inside the Member State in question, as long as they are reasonably accessible to the operator;
· “best” means most effective in achieving a high general level of protection of the
environment as a whole.
Techniques to consider in the determination of BAT light crude processing
Close to 600 techniques have been considered in the determination of BAT. Those techniques have been analysed following a consistent scheme. That analysis is reported for each technique with a brief description, the environmental benefits, the cross-media effects, the operational data, the applicability and economics.
BREF document for each industrial sector.
Amongst the many environmental issues addressed in the BREF, the five that are dealt with below are probably the most important:
· increase the energy efficiency
· reduce the nitrogen oxide emissions
· reduce the sulphur oxide emissions
· reduce the volatile organic compounds emissions
· reduce the contamination of water
The light crude processingbubble concept usually refers to air emissions of SO2, but can also be applied to NOx, dust,
CO and metals (Ni, V). The bubble concept is a regulatory tool applied in several EU countries.
As represented in the picture, the bubble approach for emissions to air reflects a “virtual
single stack” for the whole refinery.
If the bubble concept is to be used as an instrument to enforce the application of BAT in the refinery, then the emission values defined in the refinery bubble should be such that they indeed reflect BAT performance for the refinery as a whole. The most important notion is then to:
identify the total fuel use of the refinery;
assess the contribution of each of the fuels to the total fuel consumption of the refinery;
quantify the emissions from process units implicated in such emissions (e.g. FCC, SRU);
review the applicability of BAT to each of these fuels and/or the process units
combine this information with the technical and economical constraints in using these techniques.
BAT is to: implement and adhere to an Environmental Management System (EMS). A good EMS could include:
The preparation and publication of an annual environmental performance report. A report will also enable the dissemination of performance improvements to others,
and will be a vehicle for information exchange. External verifications may enhance the credibility of the report.
The delivery to stakeholders on an annual basis of an environmental performance
improvement plan. Continuous improvement is assured by such a plan.
The practice of benchmarking on a continuous basis, including energy efficiency and
energy conservation activities, emissions to air (SO2, NOx, VOC, and particulates),
discharges to water and generation of waste. Benchmarking for energy efficiency
should involve an internal system of energy efficiency improvements, or intra- and
inter-company energy efficiency benchmarking exercises, aiming for continuous
improvements and learning lessons.
An annual report of the mass balance data on sulphur input and output via emissions
and products (including low-grade and off-spec products and further use and fate).
Improve stability of unit operation by applying advanced process control and limiting
plant upsets, thereby minimising times with elevated emissions (e.g. shutdowns and startups)
Apply good practices for maintenance and cleaning.
Implement environmental awareness and include it in training programmes. Implement a monitoring system that allows adequate processing and emission control.
a) Storage tank with floating roof; b) Exhaust gas washes (gasoline); c) Fine purification (adsorption); d) Low-temperature cooling (to – 40 °C)
A) Vapor recovery at the service station;
B) Large carbon filter in the motor vehicle
a) Gas displacement pipe;
b) Vent; c) Gas venting valve
actuated by filling nozzle;
d) Gas – liquid separator; e) Gas
line; f ) Magnetic valve and
regeneration control orifice;
g) Standard gas vent and
overturn protection; h) Outlet;
i) Fuel tank; j) Liquid seal in
filling tube (reduces escape of
gases); k) Activated carbon filter
with 4.5 L capacity (traps gases)
Example of specific emissions and consumptions found in European refineries