Fuels & Combustion(MEE322)

9 Feb 2016

by

Dr. Thangaraja J

Assoc. Prof. SMBS

Main Building 235C

Recap...

Composition of Petroleum

Paraffins, Olefins, Napthenes & Aromatics

Rating of Petroleum Fuels

Octane & Cetane Numbers

Crude Oil Classifications

Quiz I (15.2.16) 20 marks

Petroleum Utilization

A large number of different products is obtained from the petroleum refinery

Most of them are used as fuels A small fraction is used as the basis for the (petro)chemical industry which gives us

such indispensable products as plastics, pharmaceuticals and textiles.

Petroleum Recovery

After geologists have located the general area in which petroleum is thought tooccur, a well is drilled

Selecting the site for drilling requires detailed knowledge of the geologicfeatures under the earth's surface

Drilling is also done to determine the extent of the reserves

Cable Tool Method

The older cable-tool method used extensively until 1900, involves raising and dropping a heavy bit and drill stem attached by cable to a cantilever arm at the surface

It pulverizes the rock and earth, gradually forming the hole.

This method is generally employed for penetrating hard rocks at shallow depths

Drill bits have many

designs

Well Completion

Completing a well and preparing for oil production involves insertion of a casing,which comprises one or more strings of tubing

The casing provides a permanent wall to the borehole to prevent cave-ins and inflow ofunwanted water

a return passage for the mud stream and

control of the well during production

An assembly of valves, known as Christmas tree is installed above a mastervalve at the casing head if oil is expected to flow naturally (Liquid expansion,evolution of dissolved gases from oil, influx of natural water, gravity orcombination of these effects )

If mechanical lift or by gas or airlift is anticipated, the Christmas tree assembly isnot anticipated

The first oil well in US, drilled by Edwin Drake was only

21 metres deep

Today it is common to drill oil wells several thousands of feet deep, in some cases to an extreme of 25,000 feet

(almost 7.6 km!)

Enhanced Recovery

Tertiary recoverySecondary recovery

When it is no longer possible to pump the oil with conventional techniques

In Secondary recovery, conditions similar to flush production are created.Instead of relying on naturally occurring water or gas to force the oil out, the oilfield is flooded with water pumped down into wells to force the oil out, or gas ispumped down a well to create an artificial version of gas cap drive.

Secondary recovery methods extract an additional 10 to 20% of

the available oil from a well

In general, it is usually necessary to decrease the viscosity of the oil to achieve further recovery.

Tertiary recovery often involves heating the oil underground, such as by injecting steam into the wells.

Tertiary recovery is

more expensive

Steam methods have been

mostly applied In relatively

thick reservoirs containing viscous oils

Transportation

Ships oil tankersPipelines

Once the oil has been pumped out of the ground, it must then be transported to the users

The best known is the Trans-Alaskan pipeline, which runs for 1287 km

The tankers are and carries 50 million barrels of oil across the

oceans, equivalent to about a three-day oil consumption in the U.S.

Diesel Composition [ Windom et al (2012) ]It contains many

n-alkanes,

cycloalkanes,

polyaromatics,

alkylbenzenes

Diesel property

Kuwait crude

Nigerian crude

Density 852 878

Cetanenumber

54 41

Petroleum Refining

In general, refinery processes can be divided into three different types

Separation: Division of the feedstock into variousfractions depending on the nature of crude material

Conversion: Production of salable materials by alterationof the chemical type of the feedstock constituents

Finishing: Purification of various product streams byvariety of processes which essentially remove impuritiesfrom the product

The Separation and finishing processes may involve Distillation or treatmentwith a wash solution

While the conversion processes usually involves change in the number of carbon atoms per molecule, alter the molecularhydrogen/carbon ratio

even change the molecular structure (Isomerization) without affectingthe number of carbon atoms per molecule

If salt water is not removed, the materials of construction of the heater tubes andcolumn intervals will be exposed to chloride ion attack and to the corrosive actionof hydrogen chloride

Pre-treatment

Simple brine suspensionsmay be removed from crude oilby heating under pressuresufficient to prevent vapor loss(90 150C) then allowing thematerial to settle in a largevessel

Emulsions may also bebroken by addition of treatingagents such as soaps, fattyacids, sulfonates and longchain alcohols

Fractions Approx. Boiling range (C)

Applications

Fuel gas -162 to -42 Contains methane, ethane and some propane refinery fuel

Propane -42 LPG

Butane -12 to -0.5 LPG component of gasolines in cold climate

Light Naphtha -1 to 150 Straight run gasoline, solvents

Heavy Naphtha

150 to 205 Catalytic reformer feed, component of jet fuels and solvents

Kerosene 205 to 260 Illuminant, Fuel

Stove oil 205 to 290 Fuel

Light gas oil 205 to 315 Fuel oil, Diesel fuel, absorbent

Heavy gas oil 315 to 430 Catalytic cracking feed

Vacuum gas oil 430 to 540 Catalytic cracking feed, suitable crudes yield lubricating oil

Residue 595 and above Bitumen, Petroleum coke making

Petroleum Distillation

The initial fractionation of crude oil essentially involves

distillation of the material into various fractions

Distillation has remained a major refinery process

It is the first step in crude oil refining, Crude oil which is contaminated by saltwater

must first be treated to remove the emulsion.

Cast iron vessel

Continuous Distillation or Battery Still

Number of stills coupled together in a row (battery) Stills were arranged so that oil flowed by gravity from the first to last