How Ships Convert Sea Water to Fresh Water | Chief MAKOi Study Call Ep 04

Summary

In this episode of Study Hall, Chief McCoy explains how ships produce fresh water from seawater using distillation, a process of evaporation and condensation. Ships on coastal voyages can get fresh water from suppliers, but ocean-going vessels must generate their own. Distillation plants aboard ships can produce 15 to 50 tons of fresh water daily. The process involves heating seawater to create steam, which then condenses into fresh water when cooled, leaving behind salt and minerals. Key components of the distillation plant include the evaporator, condenser, ejector pump, and Solano meter, which ensures the purity of the fresh water produced.

Takeaways

• 🚢 Ships require fresh water for various purposes, which cannot be met by seawater alone.
• 🌊 For coastal voyages, ships can easily obtain fresh water from suppliers, but ocean-going vessels must produce their own.
• 💧 Fresh water generators on ships use either distillation or reverse osmosis, with distillation being more common in commercial shipping.
• 🔥 Distillation involves purifying liquid through evaporation and condensation, leaving behind heavier minerals like salt.
• 🌡️ Distillation plants on ships are designed to operate efficiently when the main engine is running, utilizing waste heat from the engine.
• 🏺 The distillation process on ships involves an airtight casing with separate sections for evaporation and condensation.
• 💧 Seawater is heated in the evaporator, turning into steam, which then condenses into fresh water in the condenser.
• 🔬 The purity of the fresh water is checked using a Solano meter, which measures electrical conductivity to determine salt content.
• 🔄 If the fresh water's salinity is above 10 ppm, it is recycled back into the evaporator; if below, it's stored for use.
• 🔧 Distillation plants can be of two types: tube type or plate type, both operating on the same principle of heat exchange and vacuum creation.

Q & A

How does a ship obtain fresh water for use during coastal voyages?

For ships doing exclusively coastal voyages, fresh water is usually supplied when they are in port. They place an order, and a supplier comes to connect a hose and fill up the water tanks.

What is the primary method used by ocean-going vessels to produce fresh water during long voyages?

Ocean-going vessels produce fresh water using a freshwater generator, which typically operates on the principle of distillation or, less commonly, reverse osmosis.

What is the basic principle behind the distillation process used to produce fresh water on ships?

Distillation is the process of purifying a liquid through evaporation and condensation. Seawater is heated to create steam, which leaves behind heavier minerals like salt. The steam is then cooled and condenses back into liquid form, now free of salt, to produce fresh water.

What is the typical daily fresh water production capacity of a distillation plant on a ship?

Distillation plants on board ships are typically designed to produce between 15 to 50 tons of fresh water per day, depending on the ship type and fresh water requirements.

What are the two main types of distillation plant designs used on ships?

Distillation plants on ships are either of the tube type or plate type designs, with the principle of operation being the same for both.

Why are distillation plants used when the ship is underway, and how does this relate to the seawater quality?

Distillation plants are used when the ship is underway because seawater is cleaner in the deep and open sea compared to near land where it might contain mud and other contaminants. Additionally, the heating medium for the evaporator comes from the main engine jacket water, which is more readily available when the ship is in motion.

How does the ejector pump contribute to the distillation process on a ship?

The ejector pump creates a vacuum inside the distillation plant's shell by using the venturi effect. This vacuum lowers the atmospheric pressure inside the shell, allowing seawater to boil at temperatures lower than 100 degrees Celsius.

What is the role of the condenser in the distillation process aboard a ship?

The condenser in the distillation process cools the steam produced by the evaporator, causing it to condense back into liquid form, now as fresh water, which is collected in the liquid receiver.

How is the purity of the fresh water produced by the distillation plant measured?

The purity of the fresh water is measured using a Solano meter, which determines water purity in terms of salt content by measuring electrical conductivity. Pure water has high resistance to electrical flow, while salt water conducts electricity well.

What happens to the fresh water if the salinity measured by the Solano meter is above 10 ppm?

If the salinity of the fresh water is above 10 ppm, a magnetic valve activates, diverting the flow of fresh water back into the evaporator for further processing.

Outlines

00:00

🚢 Freshwater Production on Ships

This paragraph introduces the topic of how ships produce fresh water from seawater, a necessity for long ocean voyages. It explains that while coastal ships can easily replenish their fresh water supply, ocean-going vessels must generate it onboard. The freshwater generator, which can be of two types - distillation or reverse osmosis - is the focus of this episode. Distillation is the more common method in commercial shipping and involves the process of evaporation and condensation to separate fresh water from salt and other minerals. The paragraph also outlines the basic principles of distillation and mentions that the process is typically carried out on a large scale, with distillation plants on ships designed to produce up to 50 tons of fresh water per day.

05:05

🔬 Detailed Operation of Distillation Plants

This paragraph delves into the specifics of how distillation plants operate on ships. It explains that the process is most efficient when the ship is underway, utilizing cleaner seawater from the deep sea and waste heat from the main engine. The paragraph describes the components of the distillation plant, including the shell, evaporator, condenser, ejector pump, inductor nozzle, distillate pump, and Solano meter. It outlines the process of seawater being sucked into the evaporator, heated, and evaporated, leaving behind heavier minerals. The steam then condenses back into fresh water in the condenser, which is collected and checked for purity before being stored. The paragraph also discusses the creation of a vacuum inside the shell to lower the boiling point of water, allowing it to evaporate at temperatures below 100 degrees Celsius.

10:08

📚 Conclusion and Future Topics

In the final paragraph, the narrator wraps up the discussion on distillation plants used for fresh water production on ships. It summarizes the key points covered in the episode and hints at future episodes that will explore other methods of fresh water production, such as reverse osmosis. The paragraph serves as a conclusion, reinforcing the educational value of the video and setting the stage for further exploration of related topics.

Keywords

💡Distillation

Distillation is a process of purifying a liquid through evaporation and condensation. In the context of the video, it is used to transform seawater into freshwater by boiling it to produce steam, which then condenses back into liquid form, leaving behind impurities like salt. This process is crucial for ships to produce their own freshwater supply during long voyages, as it allows them to separate the freshwater from the salt and other minerals present in seawater.

💡Seawater

Seawater is the water found in seas and oceans, containing a high concentration of salt and other minerals. In the video, seawater is the raw material that ships use to produce freshwater through distillation. Seawater is abundant at sea, making it a convenient resource for ships, but it is not suitable for many uses on board without being processed first.

💡Freshwater

Freshwater refers to water with low concentrations of salts and other minerals, as opposed to seawater. The video discusses the importance of freshwater for various uses on ships, such as drinking and cleaning, which cannot be met by seawater. Freshwater is produced on ships through distillation, which is essential for ocean-going vessels that do not have regular access to coastal freshwater supplies.

💡Evaporation

Evaporation is the process by which a liquid turns into a gas. In the video, evaporation is a key step in the distillation process, where seawater is heated until it turns into steam. This is how the freshwater is separated from the salt and other minerals, as these heavier components are left behind when the water evaporates.

💡Condensation

Condensation is the process by which a gas turns back into a liquid. In the context of the video, condensation occurs when the steam produced from evaporated seawater is cooled, turning it back into liquid freshwater. This is a critical step in the distillation process, as it results in the collection of freshwater that can be used on the ship.

💡Heat Exchangers

Heat exchangers are devices used to transfer heat between two fluids. In the video, they play a crucial role in the distillation process by heating the seawater to induce evaporation and then cooling the steam to cause condensation. The efficiency of heat exchangers is essential for the effective operation of the distillation plant on board ships.

💡Ejector Pump

An ejector pump is a type of pump that uses the venturi effect to create suction. In the video, the ejector pump is used to create a vacuum inside the distillation plant's shell, which helps lower the atmospheric pressure and allows seawater to boil at temperatures below 100 degrees Celsius. This is essential for the efficient operation of the distillation process on ships.

💡Salinity

Salinity refers to the salt content in water, measured in parts per million (ppm). In the video, salinity is used to determine the purity of the freshwater produced by the distillation process. The salano meter measures the electrical conductivity of the water, which is inversely related to salinity, to ensure that the freshwater meets the required standards before being stored for use on the ship.

💡Solano Meter

The Solano meter is a device used to measure the purity of water by determining its salinity. In the video, it is used to analyze the freshwater produced by the distillation process. If the salinity is below 10 ppm, the water is considered pure enough for use on the ship and is stored in the freshwater tanks. The Solano meter plays a critical role in ensuring the quality of the freshwater produced.

💡Vacuum

A vacuum is a space where the gas pressure is much lower than atmospheric pressure. In the video, creating a vacuum inside the distillation plant's shell is essential for the distillation process. The vacuum allows the seawater to boil at temperatures lower than the normal boiling point of 100 degrees Celsius, which is necessary for the efficient operation of the distillation plant on ships.

💡Reverse Osmosis

Reverse osmosis is a water purification technology that involves forcing water through a semi-permeable membrane to remove ions, unwanted molecules, and larger particles. Although not the main focus of this video, it is mentioned as an alternative method to distillation for producing freshwater on ships. Reverse osmosis is particularly effective in removing salt and other impurities from seawater.

Highlights

Ships require fresh water for various purposes, which cannot be met by seawater alone.

For coastal voyages, ships can easily obtain fresh water from suppliers.

Ocean-going vessels produce their own fresh water using a freshwater generator.

There are two types of freshwater generators: distillation and reverse osmosis.

Distillation is the more common method used in commercial shipping.

Distillation purifies liquid through evaporation and condensation.

Seawater is a mixture of fresh water, salt, and minerals.

Heating seawater causes it to evaporate, leaving behind heavier minerals like salt.

Cooling the steam condenses it into distilled water, which is theoretically pure H2O.

Distillation plants on ships are designed to produce 15 to 50 tons of fresh water per day.

The distillation plant consists of an evaporator, condenser, and other components.

The shell of the distillation plant is an airtight casing divided into an evaporator and condenser.

The ejector pump creates a vacuum inside the shell, lowering the boiling point of water.

Seawater is heated by the main engine's jacket water, which is around 80 to 85 degrees Celsius.

The adductor pump uses the venturi effect to create suction and draw in seawater.

The steam produced in the evaporator is filtered and condensed in the condenser tubes.

The condensate is collected and analyzed for salt content using a Solano meter.

If salt content is below 10 ppm, the fresh water is stored; otherwise, it's redirected to the evaporator.

Distillation plants are used when the ship is underway to ensure cleaner seawater and efficient heat recovery.

The distillation process involves complex interactions between the plant's components.

The distillation plant's design allows for the recovery of waste heat from the main engine.

Transcripts

hello everyone welcome to another

episode of study hall with chief McCoy

in today's video we will discuss how

ships transform seawater into fresh

water in the previous episodes I've

shown you the fresh water cooling system

and how heat exchangers work we know

that ships utilize sea water s it is

very abundant at sea but apparently

ships still require fresh water for a

lot of things wherein sea water will be

unsuitable for use so where do ships get

their fresh water for ships doing

exclusively coastal voyages it's quite

easy as fresh water is usually supplied

when they are important they simply

place an order then the supplier comes

connects the host and fill us up the

water tanks but for ocean-going vessels

which go on voyages for weeks or even

months without calling into port the

only option is to produce their own

fresh water they do this by using what

we call a freshwater generator

there are two popular types of fresh

water generators

the first type utilizes the process of

distillation and the other is by reverse

osmosis now for this episode we will

only discuss distillation as it is by

far more commonly used in commercial

shipping we will touch on reverse

osmosis in another episode let's go back

to basics for a bit distillation is the

action of purifying a liquid through the

process of evaporation and condensation

on that note evaporation is when liquid

turns into gas and condensation is when

gas turns into liquid to put things

simply sea water is basically a mixture

of fresh water and salt and a few other

minerals like calcium and other stuff

now if we apply heat to sea water it

will eventually boil and evaporate and

turn into steam when it does the heavier

minerals like salt will be left behind

now if we cool down steam it will

condense and turn into distilled water

which theoretically should be pure h2o

otherwise known as fresh water obviously

ships need to do this on a large scale

and distillation plants on board carbon

ships are typically designed to produce

somewhere between 15 to 50 tons of fresh

water per day sometimes more depending

on the ship type and fresh water

requirements distillation plans are

basically heat exchangers and similar to

other types of heat exchangers they come

either as to type or plate type designs

either way the principle of operation is

basically the same the most prominent

feature of the distillation plant is the

shell which is an airtight casing

the inside of the shell is divided

between the evaporator and the condenser

other important components include the

ejector pump the inductor nozzle the

distillate pump and the Solano meter so

how does the distillation plant work

let's go through the simple explanation

first the flow operation begins when the

sea water enters the evaporator from

there it absorbs heat and evaporates

passes through a baffle screen to filter

out remaining impurities and then comes

into contact with the condenser tubes

where it is cooled down and eventually

condenses back into liquid but this time

without the salt content

now this condensate is collected in the

liquid receiver which is directly below

the condenser tubes where it is then

suctioned by the condensate pump the

condensate pumps function is to deliver

the fresh water into the freshwater

tanks but before it could go there it is

sampled and analyzed by the salon owner

if the remaining salt content is below

10 parts per million the fresh water is

delivered into the tanks if it's higher

than 10 ppm it is diverted to go back to

the evaporator sounds simple right well

not exactly

for us to fully understand how the

distillation plant works we need to dive

in to a few more details and learn the

function of each major component and see

how the fluid reacts when passing

through each of them now let's dive into

the detailed explanation first of all

for optimal performance distillation

plants are used when the ship is

underway that is to say when the main

engine is running at navigation speed

this is mainly because the seawater is

cleaner in the deep and open sea as

compared to near land where the water is

shallow and might contain mud and other

contaminants and also the heating medium

used by the evaporator to boil the

seawater comes from the main engine

jacket water which has a temperature of

around 80 to 85 degrees Celsius weight

the boiling point of water is 100

degrees Celsius right so how could we

boil it at 80 degrees well it's true

water boils at 100 degrees Celsius at

sea level atmospheric pressure which is

around one bar but if we apply the

combined gas law which is the

combination of Boyle's Charles and gay

lussac's law the boiling point will

decrease if the atmospheric pressure

will also decrease but how exactly will

we be able to decrease the atmospheric

pressure earlier I mentioned that the

shell is an airtight casing which gives

us the potential to create a vacuum

inside the shell now just for clarity's

sake when we say vacuum it means that

the gas pressure inside the shell is

much lower than the atmospheric pressure

at sea level

so basically much lower than one bar so

during operation the ejector pump

suctions water from the main seawater

line and from there it will pass through

the adductor an adductor is a type of

pump which utilizes the venturi effect

which in simple terms only requires a

fluid moving at high velocity as the

driving medium going past a nozzle to

generate suction now the adductor

suction line is tapped into the shell so

when the fast-moving seawater goes

through the adaptor it will generate a

drop in pressure which will suction the

air and other fluid particles and create

a vacuum effectively lowering the

atmospheric pressure inside

so the shell vacuum eventually becomes

slow enough to allow the seawater to

boil at temperatures lower than 80

degrees Celsius on a side note as you

can see the distillation plant is

designed to allow the ship's power plant

to recover waste heat from the main

engine jacket water and utilize that

heat energy instead of just throwing it

out at sea now from the adductor the

seawater will pass through the

condensers cooling tubes as the cooling

medium in there it absorbs the heat from

the steam produced by the evaporator

upon leaving the condenser some of the

sea water goes into the evaporator area

as feed water now inside the evaporator

it will pass through the tubes heated by

the jacket water until it evaporates and

leaves behind the salt and other heavier

particles which will be discarded by the

adductor now the steam will arise and

will pass through a wire mesh baffle for

filtration and comes into contact with

the condenser tubes the cooling effect

will cause the steam to condense and the

resulting liquid will be collected in

the liquid receiver and then suction by

the distillate pump from there the fresh

water will be sampled and analyzed by

the solano meter the Celaeno meter is a

device which determines water purity in

terms of absence of salt by measuring

electrical conductivity the concept is

basically pure water has a high

resistance to electrical flow as

compared to salt water which has a high

electrical conductivity therefore the

higher the current flow means more salt

content so if the measured salinity is

above 10 ppm a magnetic valve activates

and diverts the flow of fresh water back

into the evaporator but if the water

salinity is below 10 ppm it is then

delivered into the ship's fresh water

storage tanks

as I mentioned earlier this relation

plants are either to type or plate type

designs I showed the to type in my

visual aids but the principle of

operation is exactly the same I hope you

enjoyed and learned something from this

episode we will have more topics to

discuss in the future but for now class

dismissed