STORAGE Transport and Applications (

8/8/2019 STORAGE Transport and Applications (

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1.0 INTRODCTION

1.1 About LPG

LPG is an acronym for liquefied petroleum gas, which is (are) hydrocarbon compound(s) which are vapours at room

temperature and pressure but can be converted to liquids through application of pressure and lowering the temperatures

extremely.These gases/ vapours are either found as condensable products from natural gas at oil or gas fields (natural gas liquids) or

during the processing of crude oil particularly at the stabilization stage when there is need to reduce the vapour pressure of

the oil before shipping it. Another source of LPG is from the refining activities of crude oil. The quantity here depends on the

quality of crude feed stock and also on the refining process.

The liquid formed by a particular amount of vapour occupies much less space as the vapour would. This makes it advantageous

to store and transport LPG as liquid but not necessarily cheaper because of the cost involved in building special pressurised

containers and systems to keep the LPG in its liquid state. The liquid is vaporised whenever it is needed and put to use.

Fig A showing expansion of LPG vapour

LPG is a very useful compound with a wide variety of domestic and industrial applications.

1.2 Composition of LPG

LPG comprises mainly of C3 and C4 gases. These are hydrocarbons having three and four carbon atoms per molecule. These

hydrocarbons have the unique property of turning into liquid when compressed moderately at ambient temperatures. The

compounds usually found in LPG are Propane C3H8, Propylene C3H6, Butane C4H10 and Butylene C4H8. However, depending on the

source, LPG may contain some elements in trace quantities such as ethane C2H6, ethylene C2H4 and some impurities.

It is not easy to determine the properties of LPG because LPG from different sources have different compositions making up

the mixture. For instance, LPG from distillation processes are usually made up of saturated hydrocarbons Propane and Butane

(both normal and isobutene).

On the other hand, LPG from cracking processes usually contains unsaturated C3 and C4 hydrocarbons in their mixture i.e.

Propylene C3H6, normal and iso-butylenes, Cis and trans Butylenes. Because of this, what is usually available is an average ortypical values of the properties of the substance.

However, certain standards have been laid down for which commercial LPG must meet. In the UK, commercial LPG standards

are covered by BS4250. These Standards state that for commercial Propane it must:

-be a hydrocarbon mixture containing propane and propylene predominantly and must be free from water and toxic substances-not contain more than 5 mole percent of C 2 gas and not more than 1 mole percent of ethylene.-not contain more than 10 mole percent of C 4 gases and not more than 2 mole percent C 5 gases.

1 litre

Liquid

233 litres

vapour

7281 litres

gas/air mixture

understoichiometric


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-have a vapour pressure of not more than 17kgfcm-2 at 45oC as determined by methods described in BS3324 codes.-be stenched and afterwards not contain more than 0.02 percent by weight of Sulphur, 92mg/m 3 at STP of mercaptan sulphur

and the hydrogen sulphide content must be below that which could be detected by Lead Sulphide stain detection method.

-not contain more than 2mole percent of acetylene and must have a distinct and unpleasant odour which could be perceivedfor quantities of gas as low as 0.4% volume in air (this is for easy detection of a leakage by smell).

These standards also state that for commercial Butane, it must:

-be a hydrocarbon mixture containing butane and butylene predominantly and must be free from water and toxic substances.-have a vapour pressure of not more than 5.0Kgfcm-2 at 22oC when stored and not more than 4.92 Kgfcm-2 when transported.-have more than 10 mole percent of dienes.-be stenched and afterwards not contain more than 0.02 percent by weight of Sulphur, 92mg/m 3 at STP of mercaptan sulphur

and the hydrogen sulphide content must be below that which could be detected by Lead Sulphide stain detection method.

-not contain more than 2mole percent of acetylene and must have a distinct and unpleasant odour which could be perceivedfor quantities of gas as low as 0.9% volume in air (this is for easy detection of a leakage by smell).

LPG could also be used for specialised applications and would require the substance to conform to standards outside those

set for commercial LPG. The LPG for such specialised applications are usually odourless and must have a high degree of purity.

Some of these applications include:

Food processing: LPG does not remain in a nutrient so it is not poisonous when in contact with human food. However, there is

need for it to have a high degree of purity, not containing any substances that could be harmful when eaten.

For Use as aerosol Propellant and in cigarette lighters: for use as aerosol propellant an in cigarette lighters, LPG must beodourless and free from residues and unsaturated hydrocarbons and have regulated vapour pressures.

2.0 PROPERTIES OF LPG

2.1 Chemical Properties

Combustion of LPG: The complete combustion of LPG is governed by the equation CxHy + (x+0.25y) O2 XCO2+0.5y

H2O + Heat.

The combustion is usually associated with the increase in volume of products plus expansion due to heat produced. Combustion

of LPG requires large volume of air (about 24vol. of air/vol. of Propane and 30vol. of air/vol. of Butane), and forms about 75%

volume of C02 per volume of LPG. This is why it is very essential that enough ventilation be provided when burning LPG to avoid

suffocation from lack of O2 and presence of excess CO2 n the air.

Calorific Value:This refers to the quality of heat released when a unit volume of fuel is combusted under given conditions in a

calorimeter. The calorific values for LPG (Propane and Butane) are very high. Typically for propane, the CV is 50.24MJ/Kg and

for Butane is 49.45 MJ/Kg.


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Effect on Materials: LPG does not react with metals used for piping or storage but usually as a precaution, the use of

aluminium is employed in vapour system components. This is because sometimes caustic soda carried over from the refining

process is present and may affect the pipes. But where very tight measures are taken to remove the caustic soda, then it

would not be necessary to use Aluminium in such systems.

For some non-metallic compounds however, the case is different. Natural rubber reacts with LPG to become spongy whileplastics become softer and brittle. For this reason, these materials must never be used in systems for processing, storage and

transport of LPG.

2.2 Physical Properties

Boiling Point and Critical Temperature: The constituent gases found in commercial LPG mixtures all have very low boiling

points. This is why they exist as vapour under atmospheric conditions unless they have been liquefied or refrigerated. The

typical boiling points for LPG components at 1 atmosphere are:

Propane -42.1o

C n-Butane -0.5o

C Mixtures Butane -2o

CCommercial Propane -45oC iso-Butane -11.7oC ethylene -103.7oC

When LPG is kept at ambient temperature or at temperatures lower than its boiling point, its vapour pressure will be equal to

or less than atmospheric pressure. When kept at temperatures higher than ambient temperatures, the vapour pressure of LPG

increases with increasing temperature and in order to liquefy the vapour, more pressure has to be applied. At a certain

temperature, it will not be possible to liquefy the vapour, no matter how much pressure is applied. Such a temperature is

known as the critical temperature. LOOK for table

Dew Point:Simply put, it is the temperature at which vapour LPG will condense. It is very essential to keep the temperatures

of all the LPG systems and units in the system at temperatures above the dew point of the gases so as to avoid condensation of

the gases. For propane, the dew point is very low so condensation is not really a problem as it does not occur. For Butane

however, there is usually a need to lag the pipes carrying it especially if low ambient temperatures are expected if

condensation is to be avoided.

Flash Point: The temperature at which sufficient vapour that could mix with air and ignite heat is applied is formed. For LPG,

the flash point is about -76oF. The flash point of a fuel helps in assessing the risk of a fire for any fuel during storage or

transport. Fuels with Flash Point less than 73oF are regarded as highly flammable for transport while those with a Flash Point

of higher than 150oF are regarded as safe.

Latent heat ofVaporization: The quantity of heat required or absorbed by LPG molecules to enable vaporisation to occur.

When LPG vaporises naturally, the latent heat required is gotten from the surrounding and the body of the liquid. This causes

the liquid to cool down extremely. This process is called auto refrigeration. For LPG, Latent heat is very important because a

good knowledge of it is required in designing the systems for vaporising and cooling of the gases.

Vapour pressure:This is the pressure which LPG can develop in a closed container. It is a measure of the volatility of LPG.

Vapour pressure increases with temperature and is usually equal to atmospheric pressure at the boiling point of the liquid. The


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lower the boiling point of a liquid, the greater the vapour pressure it will exert compared to another liquid with a higher boiling

point under the same conditions. This is why a vessel designed for Propane which has a lower boiling point than Butane can be

used comfortably for storing Butane but one designed for butane must never be used for Propane.

Adequate information about the Vapour pressure of LPG enables for proper design of pressurised systems such as tanks and

cylinders.

RelativeDensity:in liquid form, LPG is lighter than water and other petroleum gases (about 0.5 to 0.52 for Propane and 0.57

to 0.58 for Butane). In the vapour phase, LPG is heavier than air (about 1.5 to 2 times heavier). This makes it difficult to

disperse compared to other lighter gases. LPG will always seek to cling to ground surfaces and enter drains, trenches and

other low areas.

Co-efficientofcubicexpansion:This refers to the increase in volume per unit volume per unit degree rise in temperature of

a substance. LPG expands considerably with temperature change (Propane has a cubic expansion co-efficient of 0.0016 at 15oC

and Butane has 0.0011), about four times greater than that of fuel oil and ten times greater than that of water. For this reason,

it is essential that enough space be provided for expansion of LPG contents in transport and storage vessels and that the

temperature of products in these vessels be accurately measured at all times to avoid losses.

Flammability Limits: Gaseous fuels will only burn when mixed air proportions which lie between two well defined limits called

limits of flammability. The lower limit of flammability refers to the smallest quantity of gas that will need to be present in a gas

air mixture so that the mixture becomes flammable when ignited.

When 1m3 of liquid LPG leaks, it expands to about 270m3 of vapour LPG which mixes with air. For this mixture to become

flammable the ratio of the LPG to air must be 1/10. This is the lower flammability limit of the gas. The gas air mixture will

continue to be flammable until the ratio of the LPG vapour to that of air is 1/50 when it becomes inflammable. This is known as

the upper flammability limit.

Viscosity:LPG in both its liquefied and gaseous state has a very low viscosity of about 15 cp at 15OC and flows with ease like

water, petrol. This makes it easy for LPG to penetrate any break or weakness in the installation. It is therefore necessary to

employ special jointing compounds for LPG installations. Viscosity is an important parameter for choosing pumps for liquid

transfer and for predicting pressure drop along flow lines.

Appendix 1 gives a summary of the properties of LPG Propane and Butane.


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3.0 PRODUCTION OF LPG

3.1 Some backgroundinformation.

The use of petroleum products dates back as far as 5000 years ago when the ancient Mesopotamians used petroleum derived

Tar like compounds for many applications like caulking, masonry and as adhesives for jewellery. However, the basic principle of

separating petroleum into various fractions based on their boiling points and other distinctive properties was only discoveredabout 2000 years ago by some Arab scientists. In modern times, petroleum refining is considered to have begun in 1859 with

the discovery and drilling of oil in Pennsylvania by Sennaca Company, producing about 305 metric tonnes of oil from the well.

In 1910, a car owner in Pittsburgh asked a chemist by the name of Dr. Walter Snelling why the gasoline he purchases for his c ar

was always disappearing so fast. Dr. Snelling discovered that a large part of the Gasoline was composed of LPG. He then

separated, using a still and other equipment, gasoline into its liquid and gaseous components, hence LPG was produces. Since

then, other methods have been developed for producing LPG and today LPG production is an industry worth more than 12

Billion world over.

3.2 Raw Materials:There are no raw materials used to produce LPG, rather, they are found in petroleum chemical mixtures deep

under the earth surface. These petroleum mixtures are rock oil, combinations of different hydrocarbon rich fluids which

accumulate in reservoirs built of porous layers of sandstone and carbonate rocks.

3.3 The Production Process:LPG production simply involves separation and collection of the gas from its petroleum sources. The

two methods of extracting LPG from petrochemical mixtures are by separation from the natural gas phase during drilling of

petroleum and secondly by refinement of crude oil. The following outline the process involved in LPG production.

LPG from Refinement of crude:

- when underground oil fields are tapped, the gasoil mixture is piped out of the well and into a gas trap to separate the

mixture into crude oil and wet gas(comprises natural gasoline LPG and natural gas).

- Crude being the heavier sinks to the bottom of the trap and is pumped into oil storage tanks for refining processes during

which it undergoes a lot of complex chemical processes like crude distillation, catalytic cracking, etc. LPG is produced during

refinement of crude by distillation of the crude. The LPG produced is then sent to a gas sweetening unit where DEA is used to

sweeten the gas before it is cooled and sent to storage. The LPG produced from refining crude oil is small compared to that

isolated from the wet gas mixture.

LPG from WET GAS mixture

- wet gas from the gas trap is sent into a gasoline absorption plant which employs the use of absorption oil to remove to

remove natural gasoline and LPGs after cooling the wet gas. The remaining product is known as dry gas and is about 90%

Methane. It is usually piped to gas utility companies for distribution to towns and cities.

- the absorbing oil (saturated with hydrocarbons) is distilled to remove the mixture of hydrocarbons (known as wild gasoline).

The absorption liquid is then sent back to the absorber for reuse. The wild gasoline is then sent to a stabilizer column where

the liquid gasoline is removed from the bottom and the mixture of LPGs is drawn of the top. LPG makes up about 10% of the

total gas mixture.


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3.4

od cts/waste:When pr d cingL G avariety of byprod ct thatare economically usefulare also produced So it would

be more appropriate to think ofthese products as co- products ratherthan as by- products. These co-products could be solids

or semi solids such as Bitumen, orgases such as methane, orliquids such as crude oil. Crude oilis the mostvaluable ofthese

co-products as it could be refined further to give a variety ofproducts. Otherco-products of L G production are useful in

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4.0 STORAGE

The main advantage LPG has over most other fuels is that it can be used a gaseous fuel with all the advantages (low emissions,

high calorific value, low corrosive action on pipes etc) and be stored as liquid with high energy density. However, at ambient

temperature, the natural vapour pressure is high and thus creates the need for specialised storage systems that can

withstand such high pressures. These vessels are usually in the form of pressure vessels or refrigerated storage. In the caseof refrigerated storage, the liquid is cooled so that its vapour pressure is only slightly above atmospheric. Economics show

that it is only profitable to store LPG using this technique if the quantity is 5000 tonnes and above.

For pressure vessels, whether storage is at consumers place or at large storage depots, the same principle apply when

designing the vessels to store LPG.

For all kinds of storage systems, the integrity of the vessel is key, especially when used by consumers. For this reason, various

codes of practice have been produced in different regions of the world which cover LPG storage. Theses codes whether from

the UK (such as LPGITA, IGE, ROSPA) or from the US (such as ASME, NFPA), give recommendations covering the following areas

in LPG storage.

i) Vessel design and fittings, ii) Sitting and Installations, iii) Electrical installations, iv) Fire protection.

i) Vessel design and fittings: when designing vessels for LPG storage, the most important thing to consider is the pressure to

which they will be subjected by the LPG they will store. The pressure in LPG vessels is usually governed by the LPG liquid

surface temperature which is in turn governed by the ambient temperature. Various codes of practice exist to govern vessel

design for different regions. These codes are usually developed based on the historical data for ambient temperature of that

region. For the UK, LPPGITA recommends that bulk storage and transport vessels be designed using 55oC as reference

temperature, but in other regions such as America or Middle East where there are higher ambient temperatures, this

recommendation cannot be used.

Perhaps the most important fitting for any LPG storage vessel is the pressure relief valve. It helps prevent excess pressure

caused by over filling, thermal expansion of the liquid or excessive heating of the vessel due to external fire. This relief valve

must be able to discharge LPG vapour at a rate that can match that of vaporization during the scenarios mentioned above.

LPGITA, NFPA58 and IPC9 suggest that all pressure relief valves must be able to discharge vapour at a rate Q= 53.632 x A.

Where A is vessel external area in square feet. For buried vessels, the rate is required to be 0.3Q

Another important fitting is the Fixed maximum liquid level gauge. This fitting helps to prevent storage vessels from getting

over filled. Because of thermal expansion, it is required that 3% of the vessel volume be left empty. This fitting helps in

achieving this requirement. Other fitting such as drain point for draining out liquid, earthing for protection against electricity,

and bunds are also used in vessels storing LPG

ii) Sitting and Installations: Leakage from LPG pressure storage always results in a vapour release and in vapour form, LPG is

heavier than air so catch pit or bund used for this liquid is undesirable. Maximum ventilation is the aim, this is why it is

preferred that storage tank locations be selected so as to minimise the potential hazards from and to d sorroundings.


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When sitting an LPG storage facility, the following should be put into consideration.

- The storage shall be in open air to allow for good ventilation.

- Distance from residential areas: preferably, the larger the storage, the greater their distance should be from any fixed

source of ignition or residential areas. This is so because possibility of a fire depends on how far the leaked vapour will

have to travel before it gets to a source of ignition and in the event that a fire does occur, there is a greater threat to the

residential areas.

- Availability of Space for future expans ion and addition of storage installations.

- Easy access ibility for fire fighting team and their equipmen t

- Contour of the ground: Storage facilities/ installations should be uphill of a process, a source of ignition or residential area;

they should not be sited in natural depressions so as not to encourage formation of gas pockets heavier than air.

- Trenches and Drainages system: any trenches leading outside the storage area should have walls or bunds at the boundary

between the storage area and the surrounding environment and should be built with vented gas traps so as to stop any for

from spreading via the drained content of the environment and to prevent the discharge of the products into other

drainage systems.

- Prevailing wind: any escaping gas would travel or be carried by the wind blowing in a directed. So it is safe practice to

consider the direction the wind travels so that escaping gas wouldnt get carried to an ignition course.

iii) Electrical Equipment: static electricity could be a source of ignition for many hydrocarbon vapours, LPG vapours being one

of them. It is thus very essential for LPG storage vessels to be earthed an all pipe works should have electrical continuity.

Static from electrically charged transport vehicles could also be a source of ignition of LPG vapour. This is why it is

essential that transport vehicles be connected to a vessels earthing point before a hose is connected from the vehicle to

the storage vessel while transferring LPG from the vessel to the vehicle.

iv) Fire protection: certain measures have to be put in place to help control the spread of a fire in the event that a fire does

occur. These measures include water spray cooling system (simple water hose could be employed for small vessels) which

helps in cooling down the vessel surface so that excess heat from the fire does not cause the integrity of the vessel to fail.

Another of such measures is the use of insulations to reduce the rate at which the vessel is heated up by surrounding fire

thereby reducing rate of vaporization which in turn reduces the rate at which gas is vetted out of the storage vessel by the

relief valve. Insulations can only be used for large storage vessels which employ liquid withdrawal, and must able to protect

the vessel from fire for at least one hour before fire fighters arrive, it must protect the vessel from corrosion due tomoisture and dew from the atmosphere and must not retain any moisture, it must allow for inspection of the vessels shell

integrity and the insulation must not be dislodged by water streams from water sprayers and must not obstruct such

streams.


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Fixed

foot

4.

Types Of Storage And Storage Vesse s: Basically, there are two ways of storing L G in vessels; Ambient temperature

storage and refrigerated storage. To store L Gat ambient temperatures, the storage vesselmust be pressurised to avoid

vapori ation ofthe liquidL G. The fabrication of such vessels, whethermobile orfixedtype is covered by Codes of Practice,

such as LPGA Health and Safety! (HS-G"

34).

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temperature well below the boiling point of the liquid andprevent vapori ation. The table below shows the various kinds of

vessels thatare usedforAmbienttemperature and Refrigerated storage.

4.#

.#

Pressurestoragevesse$ s.

Forpressurised storage ofLPG, the followingtypes ofvessels are employed.

CYLIN % RICAL STORAG& VESSELS:These storage tanks also called Bullet-shapedvessels, are designedfor use with low operating

pressure andrelatively low storage capacity between 0.5 100 tonnes. The vessel has hemispherical ordished ends can be

mounted hori ontally orverticallydepending on the availabilityof space.

Fig C1 A cylindrical vessel. Fig C2 Pipingof acylindrical vesel

SPHERICAL STORAGE VESSELS: These are normally usedfor large s torage capacities between 100-200 tons. Construction of

such vessels is usually on site. In accordance with safetyregulations, these tanks must be equippedwith the necessaryfittings

such as pressure relief valves, coolingand fire fighting systems, etc. Figures below show a spherical tank. They are widely

usedin refineries andlarge inlanddepotandconsideredto be most economicalLPG storage vessel.

FigD1 Spherical Storage vessel (11) FigD2 Pipingof a Spherical Vessel

Va our return lineRelief valve

Maximum level

slope

One valve to be

remote operated

Max 2ft

slope

Vapour

return lineRelief valve

One valve to

be remoteslope

Sliding foot

Max 2ft


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4.1.2 Refrigerated storage

This type of storage is used when a very large storage capacity is required. The tanks storage capacity is in excess of 2000

tons. The tanks could either be single-skinned dome roof tanks with external insulation, cylindrical or spherical as used in

pressurised storage when storage is at moderately low temperature and near atmospheric pressure. For high storage

pressure and moderately low temperature, double-skinned dome roof tanks are popularly employed. They are mounted either

above or below ground.

ABOVE GROUND DOUBLE-SKINNED CYLINDRICAL TANKS: When storing a large volume of LPG at atmospheric or slightly above

atmospheric pressure, double skinned cylindrical tank with dome roof is the most suitable option. This tank is available in

various capacities from 80,000 m3 up to 105,000 m3. Typical construction of the double skinned cylindrical tanks is in appendix

2. Similar to spherical tanks, the double-skinned cylindrical tanks are also equipped with necessary safety appurtenances such

as pressure relief valves, foam system, and the likes. In addition, the dike or bund wall sufficient to contain spillage of the

largest tank must be constructed around the tank.

4.1.3 Caverns.

Under suitable ground conditions, underground LPG storage offers an alternative to vessel storage. It is considered as safe

and most economical way of oil and gas preservation. The gas storage design relies on the principles that hydrostatic pressure

in surrounding rock is more than the escape pressure of the stored gas.

MINED CAVERNS are caverns created by blasting a suitable quality rock formation. The rock must not permit the entry of water

or leak out of gas. The cavern must be purged first before LPG is pumped into it.

SALT DOME CAVERNS are naturally occurring. A well is drilled into high purity natural salt formation and water is then injected

into it to dissolve the surrounding salt up to a desired volume. A huge excavated overhead water curtain gallery is built to

maintain the gas storage pressure. Access into the cavern is via a waterproofed shaft.

Fig E salt domecavern (10)


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5. ' TRANSPORTATION OFL( G.

LPGcould be transportedfromits production pointto bulk distribution terminals usingavariety ofmodes oftransport such as

pipelines, railroad, barge, andtruck ortanker ship.

5.1 Pipelines:Pipelines are convenientmeans oftransfer ofmassive quantities ofLPGfromthe refineries eitherto the secondarybulk supplyplants locatedin highlyindustriali) edlocation orto averylarge customer organi) ation like powerplant.Pipelines

must be fitted with appropriate laggingand earthingfor safetyandloss prevention purposes.

5.2 Rail andRoad Trucks:In the late 1920s Railcars were introducedas ameans oftransportinglarge LPGquantities which are

too smallto be moved bypipelines. Bulk shipmentis done in a specialpressure vessel with 40-50 tonnes capacities. The

vessels are fitted with necessary uploadingfacilities based on safety specification. Supplyviarailtransport was however

limitedto areas aroundthe train terminals. Roadtrucks were later usedfordistribution ofrelatively smallquantities ofabout

33,000 to 41,600 Litres ofLPGfromthe refinery or secondary supplyto the locallyplacedcustomers orto the retailfuelling

station. These trucks usuallycarrytheir own on board unloading systemto facilitate quick unloading ofthe product.

FigF1 L0 Gtransporttruck (7)

2 Vapor Eliminator

3 Meter

4Differential Regulator

5 Manual Shut-off Valve

6 Bypass Valve

7 Tachometer

8 Power Take-Off Control

9 Throttle Control

10 Tank Outlet Valve Control11 HydrostaticRelief Valve

13LiquidDelivery Hose

14 Vapor Return Hose

15 Thermometer

17 Rotary LiquidLevel Gage

FigF2 showing unloadingsystem on boardatruck (7)

Unloadingsystem


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5.3 Sea Transport:in ships, LPGis transportedin liquidformandatpressures higherthan atmospheric orattemperatures

lowerthan ambienttemperatures oracombination of both. LPGcarrier ships are dividedinto Pressurised, Semipressurised,

Semirefrigerated Semipressurised- Fullyrefrigerated Fully-refrigeratedandInsulated. The table below outlines the features

as wellas advantages anddisadvantages of each category.

Table 1 Showing featuresof varioustypesof L1 Gcargoships.

FigG An L1 Gcargoship (9)

Vessel/carrier

Type

Capacity Design Pressure

and Temperature

Advantages Disadvantages

Pressurised 2000 m3 17.5kgcm-2, 45oC -Needs no re-liquefaction plant.-Simple and easy operations-No insulation is requiredas cargo iscarriedatambienttemperature

-Very heavy because oftheirthick tank

wall.

Cannotcarryas much LPGas a

refrigeratedvessel of similar si2 e

Un optimi2 ed utili2 ation of ship space.

Fully Refrigerated 101000m3 0.28kgcm-2, -50oC Can transportverylarge quantities of

LPG, with good utili2 ation of ship 3 s

available hold space.

Costs more to buildcomparedto other

vessels.

Insulated Lightin weight so itcan carrymore

LPG

Storage tanks have little strength

Semipressuri2 ed,

semirefrigerated

and semi

pressurisedfully

refrigerated

Between

5000 to

12000 m3

5-8 kgcm-2,

-10 to -48oC

Can carrymore cargo than

Pressurised ships,

Relativelylighterin weight

Quite complex on board operations.

Requires on boardre-Liquefaction plant

Requires Insulation


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6.0 CYLINDERFILLING PLANT:

LPGfor small scale industrial use andfordomestic use is normally storedin either steelcylinders or small bulk fixed storage

tanks readyfor use. The filling ofthese smallcylinders is carried outin special smallfillingplants calledcylinder or bottle

fillingplants. These plants needto be equipped with special units to carry outthis task. Cylinders or bottles are usuallyfilled by

weight. Scales with automatictrip-valves, such as those shown in Figure below are widely used. Forlarger operations, the

pump si4 e depends on the number of bottles to be filledatany one time. The design ofthe plants varies accordingto levels of

automation andcomplexity, buttheirprinciple of operation is the same.

Basically, acylinderfillingplantconsists ofa storage tank(s) with capacityrange accordingto customerdemand, pumps for

fillingthe cylinders atfillingpoints, a supervision Systemforreading oflevels of Temperature, pressure andliquidlevel

readingin the tank(s), pumproomcomposed ofcompressors andpumps forproducttransfer, transferpoints with complete

off-loadingarms forliquidandvapourphase, acylinderrequalification unitforcylinders maintenance (complete with devices

forpall

etising, sho

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optionalLPG evacuation unitfromcylinders.

Figure H1 and H2 Cylinder filling Machine (7)

To ensure safety, the plantmust be fully equipped with fire fightingequipment. The fire fighting equipmentrequiredinclude:

waterinjection pumps, hydrant, etc, an effective and sensitive Gas andtemperature alarm system with field sensors connected

to main alarm board.


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7.0 APPLICATIONS OF LPG7.1 Industrial Application:LPG is a pure, clean energy source, which provides even and controllable heat. This makes it the ideal

heat and power source for a wide range of industrial uses. Such as fuel for furnace, fire heaters etc.

7.2 Agriculture/ Horticulture:Clean burning LPG is particularly useful where livestock or food crops are involved and because

it can be supplied in bulk for tank storage, LPG is invaluable in rural areas - often far from the source of traditional fuels and

meets the needs of Agriculturists and Horticulturists who are always looking for dependable energy solutions to increase

output and improve the quality of their produce.

7.3 LPG as an automobile fuel:LPG is known to have lower emission levels than any other fuel, has a high octane rating (between

90 and 110) and very high energy content. It is widely known as auto gas and is widely used for internal combustion engines.

LPG vehicles are quicker to fill and LPG tanks are both lighter and give more miles between refuelling than Natural Gas.

7.4 Domestic Uses:Because of its High calorific value (94 MJ/m), higher than natural gas (methane) (38 MJ/m) LPG is greatly

utilized as a cooking fuel and for central heating. It is also used in umbrella-style terrace heaters in fancy restaurants and

inns as it provides a greater opportunity for outside dining.

Elevated Flaming Torch lights with the LPG supply housed at the base of the light are now replacing conventional street lights.

7.5 For refrigeration and Air-conditioning:Highly refined LPG with very high level of purity and properly stenched (usually

propane) can be effectively employed as a replacement refrigerant in systems designed to use CFC-12, R-22 and R-134a as

refrigerants. LPG is instrumental in providing off-the-grid refrigeration, usually by means of a gas absorption refrigerator.

Blends of pure, dry "isopropane" (refrigerant designator R-290a ) and isobutane (R-600a) have negligible Ozone depletion

potential and very low Global Warming Potential However, because of its high flammability, such substitution is widely

prohibited or discouraged in motor vehicle airconditioning systems so as to avoid the risk of fire or explosion.

8.0 SAFETY CONSIDERATIONS

8.1 LPGs are extremely flammable and for this reason there is an inherent risk of fire when handling the substance. It is thus

very essential that Personnel who handle or use LPGs be informed of the potential hazards and the necessary safe handling

procedures and precautions. Also, because of their low boiling points, LPGs can cause cold burns. Propane (boiling point -

42C) presents a greater hazard than the butanes. Various codes of practice describe the safe sampling of LPG. However the

following are very important things to know when handling LPG:


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- In order to prevent cold burns, contact with liquid and with containers or delivery lines from which LPG has just been

drawn, should be avoided except with the use of suitable protective clothing,

- Where there is a risk of exposure to high vapour concentrations either from leakage or during a process, respiratory

protection breathing apparatus should be worn to avoid inhalation of LPG vapours.

- Use of suitable eye protection such as goggles and/or face-shield should be employed to protect the eyes when handling the

liquid.

-Sometimes LPG remains trapped in the fibres of clothing when it spills on it and may be ignited later, for example, when the

wearer enters a warm room or by static, giving rise to a fire hazard. So clothing which has had liquid LPG spilt on it should be

removed as soon as possible

-The use of protective clothing such as impervious gloves, overalls or apron and face-shield and/or goggles, protective

footwear hearing protection should be worn when in cylinder filling plants and when handling cylinders..

-LPG has a dissolving effect on petroleum and rubber products and as such, these products must not be used in LPG systems

so that do not adversely deteriorate under operating conditions.

- In the event of a liquid spillage, efforts should be made, for example with water fog sprays, to direct the flow of vapour to a

safe location. Because of fire and explosion hazards, persons should be evacuated and not be allowed to re-enter the area until

it has been declared safe by a competent person. The possible accumulation of potentially explosive/flammable atmospheres

and of high concentrations which could lead to asphyxiation, occurring in confined spaces or low lying areas must be

recognized.

- Storage of LPG should be outdoors or in adequately ventilated storerooms. Some situations might warrant for the cylinders

to be kept inside a building such as in use for space heating. In such situations, only the cylinder in use should be kept inside

the building. Sources of ignition should be kept well away from the LPG cylinders in storage.

- LPG cylinders should not be stored close to pressurised oxygen cylinders.

- Emergency response plans should be developed for each depot and filling plant.

Disposal of LPG: There is often very little need to dispose of LPG this is because:

- LPG is highly volatile under normal ambient temperature and pressure conditions.

- End uses for LPGs result in their combustion, when used as fuels, incorporation into other chemical structures when used as

chemical feedstock or their dispersion into the atmosphere, when used as aerosol propellants. For these reasons, there are no

specific recommendations regarding disposal. Uncontrolled combustion should however be avoided.


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REFERENCES

1. Connor, N.E. LPG: Module 1 Lecture note. School of Computing, Science & Engineering, University of Salford. GreaterManchester. UK. 2007

2. Williams A.F, and Lom W.L., LIQUEFIED PETROLEUM GASES. Guide to Properties, Application and Uses: 2nd Ed. - Revisedand Extended. Ellis Horwood. Chichester. 1982

3. Glennon E., Gas service technology 1, Basic science and practice of gas service. Benn Technical Books, Croydon. 1994.4. http://shelbygas.com/shelbygas/history.html (Accessed on 21st November 2009)5. http://en.wikiepedia.com/LPG (Accessed on 2 1st November 2009)6. http://www.brighthub.com/engineering/marine/articles/41077.aspx?image=18390(Accessed 16th November 2009)7. Blackmer Dover Company, Liquefied gas Handbook, 2008 edition8. http://www.madehow.com (Accessed 10th November, 2009)9. http://www.maritime-connector.com/Administration/_Upload/LargeImages/lng1.jpg (Accessed on 21st November

2009)

10. http://www.aglresources.net/about/gt/SaltDomeStorage.jpg (Accessed on 21st

November 2009)11. http://upload.wikimedia.org/wikipedia/commons/thumb/4/40/Gaskessel_gr.jpg/140px-Gaskessel_gr.jpg (Accessed

10th November, 2009)


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APPENDIX 1

SUMMARY OFL 6 G PROPERTIES

PROPERTY PROPANE n-BUTANE

Documents

STORAGE Transport and Applications (