Pumps working principal- Affinity Laws

Chemical Files: Pumps - Affinity Laws: A ffinity laws allows engineers to estimate changes in critical performance parameters like Flow rate (Q) Head (H)** / Pressure (P) B...

Industrial Laundry Wastewater Treatment System Process Description

Uniforms worn by manufacturing personnel, hospital employees, and meat packers; shop towels used by service stations, printing companies, and bakers; and floor mats from offices, stores and schools are all items that are washed on a daily basis by industrial laundries.

The waste water generated from industrial washers contains sand and grit, lint, free and emulsified oil and grease, heavy metals and volatile organic compounds (VOC’s).

The treatment of these waste streams involves multiple stages. Lint removal is accomplished through screening, grit removal requires sedimentation, oils and greases are de-emulsified, coagulated and flocculated through chemical conditioning, solubilized metals are precipitated by pH adjustment, and VOC’s  can be removed with activated carbon treatment.

Stage 1 Emulsion Cracking/pH Adjustment:

pH is lowered (or raised) to ~3.5 with the pH controller using acid (or caustic).  A coagulant de-emulsifier is added to break any emulsion.

Stage 2 pH Adjustment/Precipitation and Coagulation:
pH is adjusted to ~8.5 using caustic and a coagulant is added such as Alum or PAC to cause further de-emulsification and precipitation of the solids. A “pin floc” is developed indicating the emulsion and the suspended solids are precipitated.

Stage 2  - Flash Mix:
The waste water with it’s precipitated pin floc is introduced to the flash mix zone where a polymer flocculent is added.  This stage maximizes flocculent dispersion throughout the coagulated wastewater.

Stage 3 - Flocculation:
The wastewater is now introduced to the slow mix zone to agglomerate the floc into larger particles suitable to be enmeshed with the air bubbles.

Clarifier, Dissolved Air Flotation (DAF):
The flocculated wastewater is introduced into the DAF inlet where the floc particles are comingled with a pressurized dissolved fine bubble recycle stream.  The floc particles attach to the bubbles and float to the surface where they are mechanically skimmed into the float scum sludge chamber.  The clarified treated water then exits the end of the DAF and flows downstream to sewer or further treatment if necessary.  The DAF system bubbles come from a Recycle Air Dissolving system that takes a portion of treated effluent, pressurizes it and introduces air to be dissolved.  The dissolved air comes out of solution and forms a fine bubble stream when the pressure is released at the DAF entrance in the presence of floc wastewater.

DAF Sludge Handling:
The resulting DAF waste scum/sludge is removed from the DAF automatically as the scum accumulates and is pumped to the sludge holding tank where it further thickens and accumulates a batch for disposal or processing in a filter press. The sludge is mixed and conditioned with a filter aid such as DE to improve porosity and filter ability.

Sludge De watering:
The thickened DAF scum/sludge is allowed to accumulate sufficiently to provide a full batch for the Filter Press.  First a precoat slurry is circulated thru the filter press to coat the cloths with DE to prevent blinding of the cloth and aid in easy cake removal.  The filter press is then pumped with sludge until it is full.  The press is emptied of the “cake” which is a semi solid of approximately 20-35 % solids.  Sludge cake is high in fats and greases and solids and should be disposed of according to environmental regulations.

NOTE:
These operations can be performed with screening, micro filtration, dissolved air flotation and/or clarification.  All of these treatments produce a thickened slurry or sludge that may require additional conditioning before being processed with a filter press.  Precoating of the filter cloth may be required to reduce cloth blinding and cleaning problems.

BASIC PRINCIPLES OF WATER TREATMENT

WATER & ITS IMPURITIES :

Water is never found in a pure state in nature because it is an extemely good solvent.  As it falls through the atmosphere in the form of rain, it dissolves gases, in particular oxygen, carbon dioxide, sulphur dioxide and other acid gases.  This means that when the rain reaches the ground, it is in fact a mixture of dilute acids.

At ground level the acids can have a dissolving action on the rocks, thus taking mineral matter into solution.  The amount and type of minerals dissolved depends upon the variety of the rock encountered.  In limestone or chalk areas the principal minerals are calcium and magnesium carbonates.  These are acted upon by the acids in the rain to produce principally calcium and magnesium bicarbonates and calcium and magnesium sulphates.  Lesser amounts of the chlorides and nitrates are also found.  Other minerals taken into solution include iron, aluminium, sodium and become alkaline.  In areas where the principal rock type is granite, the solvent action of the rain is much less.  The acids in the rain are only partially neutralised and thus the water remains on the acid side of neutrality.  The amount of mineral matter is then usually small.  Silica levels, however, can be similar to those found in waters from limestone areas.

Thus essentially the raw water essentially contains salts consisting of following ions :

            CATIONS                               ANIONS

            Calcium                                   Sulphates

            Magnesium                             Carbonates

            Sodium                                    Bicarbonates

            Iron                                          Chlorides

            Potassium                               Nitrates                                               

           Barium                                     Flourides

            Strontium                                Phosphates

            Manganese                             Carbondioxide

            Ammonia                                 Silica

Depending on the various application and use the water has to be essentially treated :

Various treatment process involve :

1)         Filtration

2)         Activated Carbon Filtration

3)         Chlorination

4)         Softening

5)         De-mineralisation

6)         Reverse Osmosis

7)         Ultraviolet Disinfection

FILTRATION

Water filtration essentially  consists of :

1)    Coagulation

2)    Clarification

3)    Filtration

Coagulation :

The suspended solids in water acquire a negative charge which prohibits these particles from coming together to form a large mass for easier settleability.  Coagulants such as Alum, Ferrous Sulphate, Ferric Chloride which have positive charged ions like Aluminum, Iron, etc. are then dosed into the water to hasten the settling of the suspended particles.  Suitable dosing systems  are employed for this purpose.  Coagulated particles are known as “Flocs”.

Clarification :

The purpose of clarification is to bring the flocs together to form a larger mass.  The larger the mass of flocs, the heavier the particles and easier settleability.

Operation :

Raw water is pumped to a chamber outside the flash-mixer tank.  Coagulant (Alum) is dosed into this chamber through a dosing pump.  Water then enters the flash mixing chamber.  Mixing of coagulant with water takes place with the help of motorised mixer and then it enters the flocculation chamber.  Slow speed agitator mounted on this chamber rotates at gentle speed, which coalesces the floc.  The overflow of flocculator tank passes into the clarifier chamber. Clear water moves up and is collected in the outlet launder.

PRESSURE QUARTZ FILTER :

The Pressure Quartz Filter is a rapid flow filter using very Fine Silex Quartz as Filter Media.  It is ideal for filtration of water having very fine suspended matters like mud, rust, particles, dirt, etc.

A Filter is a bed of granular material which physically removes suspended matter from the water passing through it. The only change in water quality resulting from filtration is the reduction of suspended solids. Raw Water flows downwards through the filter bed and the turbidity and suspended matter is retained on the quartz surface.  Filtered water is evenly collected by an under drain system in the bottom of the vessel and flows through the outlet to service.

When the pressure drop increases to a given level, the filter is clogged and requires cleaning by backwashing.The fine suspended impurities are removed from the filter bed by backwash at very high velocity..

CHLORINATION :

The use of chlorine is the oldest and most common disinfection method for private water supplies.  Chlorine is inexpensive and readily available, reliable, easy to use and monitor, and effective against most pathogenic bacteria, virus and cyst organisms.  It also kills non-pathogenic iron, manganese and sulfur bacteria.

Chlorine is also a strong oxidizing agent which causes a problem mineral such as soluble iron and manganese to change to an insoluble precipitate so it can be filtered from the water.

Chlorination may be done in many ways.  Chlorine may beused continously in the dry or liquid form that is dropped or injected into the well water using a chemical feed pump.  For periodic or shock water treatment, chlorine can also be poured in or fed in solution using a hose.

ACTIVATED CABON FILTRATION :

The  Activated Carbon Filter is used for effective removal of colour, odour and organic contamination in the water.  It also removes dissolved chlorine in the water.  It is a rapid flow filter using water treatment grade of activated carbon granules supported by very fine quartz filter media.  It is ideal for filteration of water from underground sources having either colour, odour or organic contamination which is not accepted for potable applications.

Regular backwashing is adequate to loosen up the bed and expose fresh surfaces of activated carbon granules to trap the dissolved impurities in the water.  When the carbon granules are exhausted, it is either replaced with new activated carbon granules or is thermally reactivated.

The water flows downwards through the carbon filter bed, the colour, odour and organic contamination is trapped by adsorption on the surface of activated carbon granules. Water is evenly collected by an under drain system in the bottom of the vessel and flows through the outlet to service.  It is highly recommended to feed filtered water to Activated Carbon filter to avoid fouling of activated carbon.

SOFTENER:

Hardness & Scale Formation :

Water containing susbtantial quantities of caclium and magnesium compounds is called hard water.

It is hardness which is largely responsible for scale and deposit formation in boilers and cooling water systems.  Hardness is often classified for convenience into temporary or alkaline hardness and permanent or non-alkaline hardness.  Temporary hardness arises from the presence of calcium and magnesium bicarbonates.  When water containing these substances is boiled, the soluble bicarbonates decompose to the insoluble carbonates which form scale.  This can be represented chemically as follows :

Softening offers a simple means of removing the undesirable calcium and magnesium scale forming salts from the water.  A diagramatic form of the plant is reproduced below :

The softening process may be simplified as indicated below :-

2NaR   +          CaSO₄                                       Na₂SO₄           +          CaR₂

2NaR   +          MgSO₄                                        Na₂SO₄           +          MgR₂

R = Resin

The calcium and magnesium cations have a strong affinity for the active sites incorporated into the resin structure and hence become associated to the resin at the expense of the sodium ions, which then pass freely into the flowing water at a rate in proportion to the removal rate of the calcium and magnesium cations.

When all the sodium sites on the resin have become occupied by hardness cations (a situation which in practice should not arise), the resin is termed “exhausted” and requires “regeneration”.  The regeneration cycle involves exposing the resin to a strong solution of brine whereby the sodium ions, due to the grossly excessive numbers, liberate the hardness cations off the resins and to waste.

Regeneration process :

CaR₂                                                               CaCl₂

            + 2 NaCl                       2 NaR   +

MgR₂                                                               MgCl₂

The base exchange softening process should be capable of producing a water quality containing 0 - 5 ppm of residual hardness.

DEMINERALISATION PLANT  :

The process of producing demineralised or deionised water by ion-exchange is basically a two stage process.  The raw water to be deionised passes through a two stage deioniser comprising of Cation Exchanger followed by an Anion Exchanger.

In the cation exchanger the water is passed through a column of cation exchange resin charged with mobile replaceable hydrogen ions.  The cations in the raw water essentially consisting of Ca, Mg and Na get adsorbed on the resin surface which in turn releases hydrogen ions in the water.  Hence, the water coming out of cation exchanger will contain acid salts such as Hydrochloric acid, Sulphuric acid, Carbonic acid.  The composition is as follows :          

                        CATIONS                                ANIONS

                                                                        Carbonates

                                                                        Bicarboantes

                        Hydrogen                                 Chlorides

                                                                        Sulphates

                                                                        Silica

Hence, the pH of Decationised water will be about 3 to 3.5.  This water will be fed to Anion exchanger, in which it will pass through a column of anion resins charged with mobile replaceable hydroxyl ions.  The anions in decationised water essentially consist of carbonates, bicarbonates, chlorides, sulphates and silica and get adsorbed on the anion resin surface, which in turn release hydroxylions in the water.  The composition of water after anion exchanger is as follows :

                        H + OH                         H₂O (Pure Water)

The absence of cations and anions in the water at the outlet of anion exchanger will be indicated by low electrical conductivity of DM water. 

After the hydrogen charge on the cation resin gets exhausted, a solution of hydrochloric acid is passed through the cation resin bed.  This process will regenerate the cation resin and restore the hydrogen charge and the cation exchanger will be ready for the next cycle of operation.

Similarly after the hydroxyl charge on the anion resins gets exhausted, a solution of Sodium Hydroxide (Caustic Soda) is passed through the anion resin bed.  This process will regenerate the anion resins and restore the hydroxyl charge and the anion exchanger will be ready for next cycle of operation.

Normally, the cation and anion exchanger columns will allow a small slippage of both cations and anions through the respective beds. Hence, the conductivity of D. M. Water at the outlet of anion exchanger will be upto 10 ms/cm equivalent to approximately upto 10 ppm of dissolved solids in D. M. Water.

This D. M. Water is further polished by passing through a Mixed Bed Polisher Unit, in which the remaining cations and anions are removed to get D. M. Water confirming to IP Standards for deionised water.

The Mixed Bed Unit consists of a mixture of both cation and anion exchange resins which remove the traces of remaining cations and anions from the D. M. Water.

REVERSE OSMOSIS:

Osmosis is a natural process involving fluid flow across a semipermeable membrane barrier.  It is selective in the sense that the solvent passes through the membrane at a faster rate than the dissolve solids.  The difference of passage rate results in solvent solids sparation.  The direction of solvent flow is determined by its chemical potential which is a function of pressure, temperature and concentration of dissolved solids.

Pure water in contact with both sides of an ideal semipermeable membrane at equal pressure and temperature has no net flow across the membrane because the chemical potential is equal on both sides.  If a soluble salt is added on one side, the chemical potential of this salt solution is reduced.  Osmotic flow from the pure water side across the membrane to the salt solution side will occur until the equilibrium of chemical potential is restored (Figure 1a).  Equilibrium occurs when the hydrostatic pressure differential resulting from the volume changes on both sides is equal to the osmotic pressure.  This is a solution property independent of the membrane.

Application of an external pressure to the salt solution side equal to the osmotic pressure will also cause equilibrium.  Additional pressure will raise the chemical potential of the water in the salt solution and cause a solvent flow to the pure water side, because it now has a lower chemical potential.  This phenomenon is called reverse Osmosis (Figure 1b).

A semi-permeable membrane is selective in that certain component of a solution, usually the solvent, can pass through it, while others, usually the solute (dissolved solids) cannot.  Osmotic flow from the pure water side to salt solution side will occur across the membrane until equilibrium is reached, at which chemical potential on both sides of membrane is equal (fig 1a & 1b).

Reverse Osmosis is a membrane separation process in which the solvent (water) molecules from a pressurised solution flow through appropriate semi-permeable membrane.  The mebrane acts as a barrier to the flow of solute (dissolved solids) molecules, thereby separating solvent from solute. RO process is generally used for desalination of water.  The permeate (the liquid flowing through the membrane or purified water) which generally emerges at near atmospheric pressure, is reduced in salt content, while the feed solution which is pressurised on the other side of the membrane increases in salt content.  The only other side of the membane increases in slat content.  The only energy input required is that for pressurising the feed.  Unlike thermal desalination, membrane desalination operates at ambient temperature and without phase change, and hence energy consumption for membrane desalination is lower than that for thermal desalination.  This process is at times also also referred as Hyperfiltration.

ULTRAVIOLET LIGHT DISINFECTION :

Ultraviolet light is a method of disinfecting private water systems.  Ultraviolet radiation adds nothing to the water and does not produce any taste or odour.  The UV light is produced by a low pressure mercury vapor lamp which produces a disinfecting dose rated in microwatt-seconds per square centimeter (Mws/cm²).  Values of 30,000 Mws/cm² will kill most types of pathogenic bacteria.  However, viruses are more resistant and variable and may need upto 45,000 Mws/cm².

An Ultraviolet water treatment device is quite simple.  The most common design consists of a stainless cylindrical chamber with a cylindrical mercury are lamp located in it.     Water enters one end of the chamber, flows through the chamber around the lamp and exits the other end within a few seconds.

To be effective as a disinfection treatment, ultraviolet radiation must pass through every particle of water.  The thinner the water film and the slower the water flow, the more effective the system will be.  Also, the water cannot have any turbidity, suspended soil particles, or organic matter.  As a consequence, ultraviolet light treatment should only be attempted on clear water.  A prefilter is recommended on ultraviolet systems as is periodic inspection and lamp cleaning.

DRINKING WATER - SPECIFICATION

AS PER IS 10500:91

Sr.No.	Particulars	Desirable Limit
	Essential Characterstics
1	Colour, Pt-Co	5
2	Odour	Unobjectionable
3	Taste	Agreeable
4	Turbidity, NTU	5
5	pH Value	6.5 to 8.5
6	Total Hardness (as CaCO3) mg/l	300
7	Iron (as Fe), mg/l	0.3
8	Chlorides (as Cl), mg/l	250
9	Residual free chlorine	0.20
	Desirable Characterstics
10	Dissolved solids, mg/l	500
11	Sulphates (as SO4), mg/l	200
12	Nitrate (as NO3), mg/l	45
13	Alkalinity, mg/l	200

7 steps for earning tax-free income

1. Use indexation to nullify tax

High inflation has been a curse for investors in the past few years, but for some, it has been a boon. Tax rules allow investors to adjust the cost of an asset to inflation during the holding period. The taxpayer has the option to pay a 10% flat tax on the long-term capital gains or pay 20% after indexation.

Though the rate is higher, the high inflation has made indexation the better option in the past few years.

The taxpayers who have availed of this inflation indexation benefit have been able to reduce their tax to nil. In fact, if you invested in a debt fund or a debt-oriented MIP scheme three years ago and earned annualised returns of 10%, your tax liability would be zero (see table).

2. Invest through a non-working spouse

A homemaker's work is never finished. From sending kids to school to shopping and managing the household, her day is fully packed. Now, add one more task to this long list—investing to earn tax-free money.

This is not as simple as it appears. If you gift money to your wife, there is no tax implication. However, if this money is invested, the taxman will club the earning with your income for the year.

The clubbing provision under Section 60 is meant to check tax evasion.

If you are taxed on the income, is there any point in investing in your wife's name? Yes, there is. The clubbing happens only at the first level of income.

If this money is reinvested and earns an income, it will be treated as your wife's, not yours. "The income from the reinvested income does not attract the clubbing provision," points out Sudhir Kaushik, chartered accountant and co-founder of tax filing portal Taxspanner.com.


Here's how you can make this rule work for you. Gift money to your wife and then get her to invest in any of the several tax-free investment options (see graphic).


The earning will be clubbed with your income, but since these investment options are tax-free, it won't push up your tax liability. Your wife can then reinvest that money, and this time, the income will not be clubbed.

There's another way to escape clubbing. Instead of gifting, give her a loan to buy property. Rental income from the property will be treated as her income as long as she pays you a nominal interest on the loan.

3. Avail of minor exemption

As mentioned earlier, if a parent invests in a minor child's name, the income is clubbed with that of the parent who earns more. In some cases, a minor child may have a personal income, such as a cash prize in a competition or payments for commercials and events. However, this is rare and mostly it's the parent who invests on behalf of the child. There is a small Rs 1,500 exemption per child per year for the income earned by such investments.

You can avail of this for a maximum of two children. This means, you can safely invest Rs 15,000 in a fixed deposit in your child's name. If you have two children, that's Rs 30,000 earning tax-free income every year. Opt for the annual payout option because the cumulative option will push up the earning beyond the tax-free limit in a couple of years as the compounding effect comes into play. Tax experts feel the Rs 1,500 exemption per child is too low and should be raised, but there are others who think this should be removed. A simpler tax structure will encourage greater compliance. The original DTC had proposed the removal of nearly all exemptions and deductions, but raised the basic exemption limit and tax slabs.

4. Take help of an adult child

Rebellious, obdurate, lackadaisical, wasteful ... parents have several adjectives for college-going children. Allow us to add 'tax-savers' to this list. You can save a neat sum by investing in the name of an adult child. After a person turns 18, he is treated as a separate individual for tax purposes. This means his earnings are no longer clubbed with his parent's income and he enjoys the same exemptions and deductions as any other adult taxpayer.

"Gifting money to a child above 18 and then investing it for taxfree gains is a perfectly legal strategy. You can gift any amount to your child without any tax liability," says Kaushik of Taxspanner. You don't have to wait for the child to turn 18 before you embark on this strategy. The rule is that if an individual turns 18 anytime during a financial year (even on 31 March), he gets the benefit for the entire year. Even those with children aged 16-17 years can use this strategy. Just invest in a 500-700 day FMP.

By the time the scheme matures, the child would have turned 18 and the income will be his own. A child over 18 also raises your investment limit in the PPF. You can separately invest up to Rs 1 lakh a year in his PPF account. In case of minors, contributions are clubbed with that of the parent and the combined total cannot exceed the annual limit of Rs 1 lakh. "This helps build a capital base for the child for future use," says Delhi-based chartered acountant Mahesh Agarwal.

By investing in your child's name you also set up an escape route in case the government brings in the inheritance tax in the future. If the asset is already in the child's name, there won't be any tax. Gifting money to an adult child and investing in his name is tax-efficient but won't be a great idea if the child is financially irresponsible. A gift is irrevocable, and once given, there is no looking back. In your attempt to save 10-30% tax, you could lose 100% of the principal. Being a legal adult, an 18-year-old can also invest in stocks andmutual funds on his own. The short-term capital gains will be tax-free till the basic exemption of Rs 2 lakh a year.

5. Parents can help too

Your parents can also help you avoid the tax net. If any or both of your parents do not have a high income, while you are in the highest 30% tax slab, you can invest in their name to earn taxfree income. Every adult enjoys a basic tax exemption of Rs 2 lakh a year. For senior citizens (above 60 years), the basic exemption is higher at Rs 2.4 lakh a year. Unlike the investments made in the name of a spouse or a minor child, there is no clubbing of income in the case of parents. So, a person above 60 can potentially earn Rs 2.5 lakh per year without any tax implication. If he invests in taxsaving schemes under Section 80C, the income can be as much as Rs 3.5 lakh a year. In the highest tax bracket, this saves you more than Rs 1 lakh in a year. It gets even better if you rope in a grandparent who is above 80. Very senior citizens have a basic exemption limit of Rs 5 lakh. The grey population has a wide range of investment options.

6.Revive your forgotten Ulip

In many ways, a Ulip is like a smart phone. It's costly and many people have bought one, but only a few understand and use all its features. Most of us have Ulips in our portfolios and many of us have stopped paying the premium. If you are part of this crowd, you can use your Ulip to earn tax-free income effectively. Pay all the pending premiums at one go. However, the policy should not have lapsed due to non-payment of premium. "As long as the policy is within the stipulated reinstatement period, the policyholder has the flexibility to pay all the pending premiums at one go and revive the policy," says TR Ramachandran, CEO and managing director of Aviva India.

7. Form an HUF with inherited wealth

A lot of taxpayers are clamouring for raising the Rs 2 lakh basic exemption limit and the Rs 1 lakh tax-saving limit in the forthcoming Budget. But very few know that they can double their exemption and savings limit simply by establishing a Hindu Undivided Family (HUF). The tax authorities treat the HUF as a separate entity. It is entitled to the same exemptions and deductions as any other individual taxpayer. This means the karta gets an additional basic tax exemption of Rs 2 lakh per year, an additional tax deduction under Sections 80C and 80D, plus the benefit of lower tax slabs. As our calculation shows, one can substantially reduce one's tax liability through this tax planning tool. Not everyone can avail of this benefit. This option is open only to a Hindu, Sikh, Jain or Buddhist male. Besides, he should be married. "A family comes into existence only when a person marries. So marriage is a prerequisite for forming an HUF," says chartered accountant Mahesh Agarwal. The HUF arrangement especially suits the taxpayers who also have income from ancestral property and expect to inherit financial assets. They will be able to divert the inheritance to the HUF, thus preventing their personal tax liability to shoot up.It may not be helpful for someone with low income. You may need the help of a professional to get you started. He might charge a fee, but it will be money well spent. A simple cost-benefit analysis will tell you that if spending Rs 8,000-10,000 can save you Rs 1-2 lakh in tax, it's not a bad deal. Remember not to take this route if you are not confident of compliance with the rules. As the karta of the HUF, you are responsible for its financial affairs. A lot of people find it tough to manage their own tax planning. Imagine what will happen if they are expected to do it for their HUF as well. But if you can, make use of this option to cut tax. ET Wealth spoke to tax experts and other professionals to identify seven such windows of opportunity to earn tax-free income. Some of these, such as distribution of income and investing through family members, are well known. Yet, there are intricacies that need to be kept in mind, such as the clubbing provisions when you invest in the name of your spouse or minor child. A word of caution. Not all of these strategies will work for all investors. Investing through your spouse will not be beneficial if she is in the same tax bracket as you. Gifting money to an adult child won't be a great idea if he is irresponsible with money. In some cases, indexation may not be the best option. If you sell gold ETFs bought five years ago, a 20% tax after indexation would be higher than a flat 10% tax on profit.

Note : Above reference use are only for understanding, please consult tax payer before using the provisions.

The gas platform that will be the world's biggest 'ship

Shell has unveiled plans to build the world's first floating liquefied natural gas (FLNG) platform. The 600,000-tonne behemoth - the world's biggest "ship" - will be sited off the coast of Australia. But how will it work?

Deep beneath the world's oceans are huge reservoirs of natural gas. Some are hundreds or thousands of miles from land, or from the nearest pipeline.

Tapping into these "stranded gas" resources has been impossible - until now.

At Samsung Heavy Industries' shipyard on Geoje Island in South Korea, work is about to start on a "ship" that, when finished and fully loaded, will weigh 600,000 tonnes.

That is six times as much as the biggest US aircraft carrier.

By 2017 the vessel should be anchored off the north coast of Australia, where it will be used to harvest natural gas from Shell's Prelude field.

Once the gas is on board, it will be cooled until it liquefies and stored in vast tanks at -161C.

Every six or seven days a huge tanker will dock beside the platform and load up enough fuel to heat a city the size of London for a week.

The tankers will then sail to Japan, China, Korea or Thailand to offload their cargo.

"The traditional way of producing gas offshore was through pipelines. You brought gas up to a platform and piped it to the 'beach'. That is the way it's done in the North Sea," said Scotsman Neil Gilmour, Shell's general manager for FLNG.

'Cyclone alley'

But the Prelude gas field is 200km (124 miles) from Western Australia's Kimberley Coast and there are no pipelines there to be used.

Johan Hedstrom, an energy analyst in Australia with Southern Cross Equities, told the BBC: "The FLNG concept is an elegant solution because you don't need so much fixed infrastructure.

"You don't need the pipeline or the onshore refinery and when you run out of gas you can just pull up stumps and go to the next field."

Mr Gilmour said Shell had to overcome a "raft of technical challenges", ensuring for example that the vast amount of equipment on board would work in choppy seas.

The Prelude field is in the middle of what is known as "cyclone alley", an area prone to extremely stormy weather.

But Mr Gilmour said the vessel had been built to withstand category-five cyclones and even a "one-in-10,000-years' storm" producing 300km/h (185mph) gusts and 20m-high (65ft) waves.

The double-hulled vessel is designed to last 50 years.

When the Prelude field is exhausted, in 25 years' time, it will be completely refurbished and packed off to start work on another field off the coast of Australia, Angola, Venezuela or wherever.

A liquefied-natural-gas ship tanker arrives at a gas storage station in Japan

Mr Hedstrom said: "FLNG is a neat way of going forward. The way that energy prices are going it does look like a good industry to be in and I think they could make a lot of money out of it."

The price of LNG has risen markedly as demand has increased.

LNG currently sells for $14 per one million British thermal units in Japan, where the price was boosted by the tsunami, which cut the production of nuclear power.

The project, estimated to cost between $8bn (£5bn) and $15bn (£9.5bn), could provide 3.6 million tonnes of gas a year.

Flaring off

Nick Campbell, an energy analyst with Inenco, said Shell's move into FLNG was a "smart move".

Continue reading the main story

The World's Biggest Ships

• The Seawise Giant was the biggest ship ever built. Fully laden it weighed 657,000 tonnes. It was scrapped in 2009
• Shell refers to its FLNG platform as a "facility" rather than a ship - fully loaded it will weigh 600,000 tonnes
• Daewoo are building 10 Triple-E container ships for Maersk. Weighing 165,000 tonnes, each can carry 18,000 containers
• The Titanic, in comparison, weighed a measly 52,000 tonnes. It sank on its maiden journey in 1912

"Shell are positioning themselves in an emerging market, not just in China - where gas usage has increased by 20% - but in India, which is also increasing its demand," he said.

The project is expected to generate 12 billion Australian dollars (£8bn) in tax revenues for the Australian federal government and could benefit their trade balance by 18 billion Australian dollars over the life of Prelude.

Australia's Minister for Resources and Energy has welcomed the Prelude project, drawing attention to the reduced environmental footprint as compared with a land-based scheme.

But there has been opposition from environmentalists. Martin Pritchard from Environs Kimberley says he is concerned about the potential for "oil leaks and spills".

WWF Western Australia, meanwhile, argues that the underwater wellheads and pipelines will harm the tropical marine environment, and estimates the project will emit more than two million tonnes of greenhouse gases per year.

But Mr Gilmour says the Prelude project could be the first of several. Shell has already identified the Sunrise gas field in the Timor Sea as having potential for FLNG.

The ship, whose first section will be laid in 2012, has no name. Shell normally refers to it merely as a "facility".

"There are only four or five dry docks globally which could have built this facility and there are certainly no yards in the UK large enough," says Mr Gilmour.

He has been to Geoje Island and, speaking in a broad Ayrshire accent, he said of Samsung's yard: "It's an extraordinary place.

"It's just a phenomenal yard. Samsung is very hi-tech, world class. There are going to be some very spectacular images coming out of there during the building process."