CRUDE ASSAY ANALYSIS

Distillation characteristics of a crude are assessed by performing a preliminary distillation

called ‘True Boiling Point’(TBP) analysis, which enlightens the refiners with all possible

information regarding the percentage quantum of fractions, base of crude and the possible

difficulties during treatment operations.

PROPERTIES OF PETROLEUM FRACTIONS

Distillation of petroleum products boiling below 370 °C (IP 123/58)

Distillation, process of heating a liquid until its more volatile constituents pass into the vapor phase,

and then cooling the vapor to recover such constituents in liquid form by condensation. The main

purpose of distillation is to separate a mixture of several components by taking advantage of their

different volatilities, or the separation of volatile materials from nonvolatile materials

Octane number

Cloud and Pour Points

KINEMATIC VISCOSITY BY RED WOOD I and REDWOOD II VISCOMETERs

Redwood viscometer I is used for low viscosity oils whereas Redwood viscometer II is used for

highly viscous oils. The flow port diameters of I and II types are different. No. of sec. required for

flow of fixed quantity of oil (usually 50 cc ) is a measure of viscosity.

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ANILINE POINT OF LIQUID PETROLEUM FRACTION

This is an approximate measure of the aromatic content of a hydrocarbon fuel.

It is defined as the lowest temperature at which a fuel oil is completely miscible with an equal volume

of aniline. Aniline is an aromatic compound and aromatics are more miscible in aniline than are

paraffins.

Hence, the lower the aniline point, the higher the aromatics content in the fuel oil.

The higher the aromatics content, the lower the cetane number of the fuel.

The aniline point can thus be used to indicate the probable ignition behavior of a diesel fuel.

Diesel Index, Cetane Rating:

Ignition quality order among the constituents of diesel engine

fuels in order of decreasing cetane no, is as follows:

n-alkanes> naphthenes > alkenes > branched alkanes >

aromatics

BIODIESEL EFFICACY:

• Bio-diesel blending in Diesel improves most of the

Fuel properties

• Engine & Vehicle performance found comparable

except the cold flow properties in sub-zero conditions

• Mass emissions of carbon monoxide and particulates

found lower with Biodiesel blends, but NOx

increased, which can, however, be converted to non

toxic components by using catalytic converter

• Catalytic converter along with Biodiesel helps

further reductions of CO & particulates

• Small size suspended particles and PAH found lower

in engine exhaust with Biodiesel blends, reducing

carcinogenicity.

Determination of carbon residue (Conradson/

Ramsbottom):

It is the percentage of carbonaceous residue left after

distillation/thermal cracking (heated at a specified rate) of

crude oil or its products in absence of air.

Determined by Conradson (fuel oil) and Ramsbottom

(lubricating oil) apparatus.

3.8C=R2 +4.25R - 0.35

FLASH POINT(CLOSED) BY PENSKY-MARTENS

APPARATUS

Flash Point : The flash point of a flammable liquid is the

lowest temperature at which it can form an ignitable

mixture in air. At this temperature the vapor may cease to

burn when the source of ignition is removed.

Fire Point: A slightly higher temperature, is defined as the

temperature at which the vapor continues to burn after

being ignited.

Cleveland open cup apparatus. This test method is

applicable to all petroleum products with flash points

above 79C (175F) and below 400C (752F).

Determination of the flash point of petroleum products in

the temperature range from 40 to 360 C by Pensky-

Martens closed-cup apparatus.

SMOKE POINT

Purpose: Evaluation of kerosene in respect of its ability to

burn without producing smoke.

Definition: The smoke point is defined as the max. flame

height in mm at which a kerosene will burn without

smoking, when determined in the apparatus under

prescribed conditions.

Test sample is burned in a standard lamp in which flame

height can be varied against a background of a graduated

mm scale.

Significance: Higher aromatics lower smoke point

VAPOUR PRESSURE: REID METHOD

The test determines the vapor pressure of volatile, non-

viscous petroleum products.

The test sample, contained in the gasoline chamber, is

connected to an air chamber fitted with pressure gauge. The

apparatus is kept at 37.8 °C, shaken periodically until constant

pressure is recorded.

Also study other tests for petroleum fuels as listed in my

previous communication

Lower Limit of inflammability (Lower explosion limit) is

the smallest quantity of a combustible gas which, when mixed

with a given quantity of air(or oxygen) will just support a

self-propagating flame.

Upper limit of inflammability (Upper explosion limit) is

the highest quantity of a combustible gas which, when mixed

with a given quantity of air(or oxygen) will just support a

self-propagating flame.

ATMOSPHERIC OR AERATED GAS BURNERS

The kinetic energy of the gas is used to aspirate air from

the atmosphere into a mixing tube, which has a burner

head at its end. A Bunsen burner is a typical example.

1. Torch burner 2. Ring burner 3. Pipe burner

VAPORIZING TYPE OIL BURNERS

POT TYPE BURNER

The oil is supplied by an oil line & stored in reservoir. Oil

is heated by radiation from hot walls & flame & gets

vaporized. The vapor mix with primary air admitted

through central pillar and perforations in the pot wall.

The fuel-air mixture is too rich at the oil surface to support

combustion; further up, it is diluted with air & becomes

inflammable.

ATOMIZING TYPE OIL BURNERS

Atomization prepares the liquid fuel for combustion by

disintegrating it into droplets. Enormous surface area per unit

mass of the fuel is created & this helps the heterogeneous

combustion of the liquid oil and the gaseous oxidant.

Based on the principle of atomization , there are three types of

atomizing burners:

(i) pressure jet (ii) twin fluid, and(iii) Rotary.

TWIN- FLUID ATOMIZATION FOR OIL BURNERS

COAL BURNING EQUIPMENT

Coal may be burned in a fixed or an agitated bed on a

grate, in suspension in air, in pulverized fuel burners or

fluidized bed burners, in a slurry with water or in

suspension in oil in atomization burners.

TRAVELLING GRATE STOKER

Coal is fed from a hopper onto a grate , moving through

the combustion chamber. The grate consists of a number

of cast iron bars interlocked to form a grate. The coal

enters at one end and by the time it reaches the other end,

the combustion is complete(the rear firing arch helps in

the rapid ignition ) and the ash falls into the ash pit.

SPREADER STOKER

Spreader rotor continuously supplies coal from a hopper

into the furnace above the glowing fuel bed on a grate. The

fines are burned partly in suspension, while the lumps

form the fuel bed. The grate may be stationary or moving

(10 mm/min); the strongest caking coal can be burned. It

has remarkable adaptability to a wide range of coals and

load fluctuations. Typical burning rates: 300-450 kg/m2.h.

Calorific value (CV) by Dulong’s Formula

(check calculation) show the overall heat balance

including losses

Thermal efficiency of furnace 24.9%

WASTE HEAT RECOVERY: If some of the “ waste heat”

in a process could be recovered, a considerable amount of

primary fuel could be saved.

Waste Heat Recovery using Recuperator

In a recuperator, heat exchange takes place between the flue

gases and the air/fuel (if permitted) through metallic or

ceramic walls. Duct or tubes carry the air/fuel for combustion

to be pre-heated; the other side contains the waste heat stream.

Convective-Radiative Recuperator

Recuperator Burner

The recuperator is integrated with the burner system such

that the flue gases are drawn back through the combined

unit. The functions of a burner, , flue and recuperator are

combined in the recuperative burner in a single compact

unit which provides an economic means of waste heat

recovery.

(Refer O.P.Gupta” Fuels, Furnaces and Refractories” for

more details and figures)

Furnaces:

In case of boiler system, economizer can be provided to

utilize the flue gas heat for pre-heating the boiler feed

water. Whereas, in an air pre-heater (recuperator), the

waste heat is used to heat combustion air/fuel. In both the

cases, there is a corresponding reduction in the fuel

requirements of the boiler.

Economizer

Because the exhaust gases (Flue gases) are usually in the

medium temperature range and in order to conserve space, a

more compact boiler can be produced if the water tubes are

finned in order to increase the effective heat transfer area on

the gas side.

(For details: reference “Efficiency Comparison Between Circular and

Semicircular Fins Circumscribing Circular Pipes” by R.Chakraborty and

A.Sirkar, Journal of Heat Transfer; Copyright © 2011 by ASME APRIL 2011, Vol. 133 /

044501-1)

(For additional information, figures/description:Text

Books: Modern Petroleum Refining Processes

(B.K.BhaskarRao); Elements Of Fuels, Furnaces &

Refractories (O.P.Gupta) ; Fuels And Combustion (Samir

Sarkar)