Transcript for: Natural Gas Usage and LNG Overview
The United States uses
80 to 85 billion cubic feet of natural gas per day. That's about 30,000 billion
cubic feet per year. We use it for cooking,
heating, electricity generation and manufacturing many modern products such as fertilizers and pharmaceuticals, and on a national scale it can be used as a power leverage. So come along and join me in a guest subject matter
expert speaker today as we overview on why and how we process, liquefy, stored and transport natural gas. (upbeat music) So liquefied natural gas or LNG is the natural gas predominantly
consistent of methane. And it's not to be
confused with LPG or NGL. LFI petroleum gas is a condensate composed primarily of propane with
small quantities of butane, and natural gas liquid is a general term for the liquid heavy
hydrocarbons that are separated from the natural gas. So by liquefying the natural gas we can reduce the volume
by at least 600 times. This number comes from dividing the specific volume of natural gas at ambient temperatures
by the specific volume when it is at negative
260 degrees Fahrenheit for the same atmospheric pressure. Methane also has the high heating value and hydrogen to carbon ratio
compared to other alcanes which contributes to its
combustion efficiency. So this is an overview of a
typical LNG chain of processes. So the natural gas from
the oil well is separated from the crude oils,
purified and dehydrated through upstream fuel processing before it gets delivered to the end users. We first pretreat the gas
by removing impurities such as hydrogen sulfide. We then pretrial the natural gas to remove heavy
hydrocarbons, which are sent to a fractionation facility for separation to ethane, LPG, and gasoline. Finally, we show the natural gas to liquid form through a
series of heat exchangers that are known as cold boxes. This P&ID shows the
processes from the feed gas through pretreatment, liquefaction and then storage and export. As you can see, are the
heart of all these processes at the liquifaction section, which falls the general
refrigeration cycle and facilitated by Joule Thompson medium such as the control valve
expander or turbine. These refrigerator and
systems can either be pure, mixed, precooled mixed or cascade design in order to cut the
power of the compressor. In the following example, Mr. Train, is gonna walk through an example of a cascade refrigeration system. - [Instructor] We have
multistage cold box, not only that each complexion
system system methane, ethylene and propane is
a multistage composure at least three stages in order to improve efficiency
on each refrigeration system. But we also employ heat
integration in the system in such a way that detect
the liquid propane, you flash out to JT
control valve to cool down the ethylene gas to condense it. So once ethylene becomes the liquid, in turn you can even use
ethylene liquid to condense the methane, and you can even
use part of the liquid propane to condense or at least cool
down the methane vapor liquid. At this point, methane
is the verbal liquid until it cool down on the
last part of the ethylene to become liquid. So now with the heat equation, a multistage compression
system and multistage cold box, you can imagine how
efficient the system is to cool down the natural gas
from 90 even 100 degree F in the summer, all the
way down to minus 260 ready store into the LNG storage tank. Now, the reason this system
is very popular out there because they've have efficiency
of 100% or 93% at least, and compared to the
rest of other technology with lower less than 93%
or some even less than 90%. So that's why ConocoPhillips
multistage cascade is just so popular. - [Host] Now, all these
cryogenic processing happens in LNG trains which be
classified as two basic types. There are large units on the
waterways with carrier ships providing a continuous supply of LNG and smaller peak shaving
plants that store and regasify the LNG when fuel demands
increase in the winter months, has the term peak shaving. They ensure uninterrupted
supply to end users during a short period of peak demand operating only on selected
portions of the year and are located near the point of usage which makes them very
capitally efficient to operate. Now, one big safety difference to know between natural gas and its
solidified counterpart is that while the natural gas will rise when it leaks to the atmosphere, NLG's vapors are initially
heavier than the air and then it spreads along
the ground when it leaks. This leak in open to a
potential ignition source and flashback resulting
into great explosion. This is also another reason
why the LNG terminals are located along the waterways. It's both with convenience of exporting and for safety reasons. Now some of these are
located completely offshore like the Adriatic Terminal
while some are docked in land. Process safety and risk
assessment along with economics are evaluated to determine
these exact locations. Now, the us production of natural gas has been significantly high
since the Sell gas discovery. So there have been several
proposals over the past years to convert the regasification terminals which were originally built
for importing natural gas into exporting terminals. It's an expensive propositions since it cost money to
electrify the natural gas, but the United States is currently set to potentially become the
world's biggest exporter of LNG. So when it comes to the
storage of natural gas, protection and installation are key, thus a full containment tank is used with both outer and inter tanks being capable of
independently storing the LNG. Material of construction accounts
for cryogenic temperatures that are lowest negative
450 degrees Fahrenheit. Full containment LNG tanks designs are based on 9% nickel steel inner tank in a pre-stressed concrete outer wall with the reinforced
concrete roof and base slab. So the nickel steel inner tank has normal operating conditions. The carbon steel outer tank
which is three to feet distant from the inner tank
supports the outer roof, it is also prepared to contain
the refrigerator liquid and control the venting of the
vapor in case of a leakage. Both inner and outer tanks
have insulation between them to help maintain initial
cryogenic temperatures. There's also a bottom heating system in order to avoid frosting. So the question is, what
are the safety concerns of storage and how do we mitigate them? - [Instructor] Well, is the
potential answer phenomenon that can happen when you
have a stratification in the tank because of
different layers of LNG, because of different density. Now, the less dense at the
bottom is gonna rise up and the more dense layer
on the top gonna sink down in the rollable fashion. So it can happen during the unloading of LNG at the import terminal
in a tank container LNG with the different
composition and density. So it is a very dense
phenomenon that can lead to overpressure and gas
release from the tank unless you have a very good
pressure relieve system to handle the over pressure and protect the system
against such a scenario. Now, the second scenario that
very dangerous is the ball of gas of LNG because
the tanks receiving heat during the shipping,
loading and unloading, and that can generate natural
gas vapor due to heat leakage into tank preinsulation. So the gas compression
facility need to be properly and adequately designed to
recover and handle ball of gas. And that you can either
recompress that natural gas back to the system, could recondenser
by changing heat with LNG, or you can send out to the downstream. So this picture down here, you can see the dotted line
represent the ball of gas from the two tank and to
the compressor section and that compress to
the revaporizer system and sent to the downstream facility. Now, in order to revaporize the LNG we have a two method that
commonly used out there. The first one we call the
submerge compress and vaporizer or a CV, which the LNG
pass through tubes immersed in water bath and being
hit by much burner. And the other type is
the open rack vaporizer, in which the LNG can pass
through the tube with water. And that you can use either
sea water, river water that runs down on the
outside of vaporizer tube as thin layers. So the picture you see here, basically, typical open rack vaporizer. You can see this sea
water coming down to tube on the outside and LNG energy
inside the tube rise up in countercurrent, and then
it's go to downstream facility. And the picture down here you
can see there's a typical size of the open rack vaporizer. Now the other type basically, the submerged combustion vaporizer, it's just the furnace that's
immersed in the bath of water, heat the water, and the heated water, which in turn to vaporize the LNG again go through the tube and
then aggregate revaporized and sent out the downstream facility. The pictures you see
the typical fire furnace at the terminal that to
regasify the LNG from the tank before sent to the downstream facility - LNG ships are specifically
designed to handle LNG as opposed to other products like oil. They are typically 250
to 350 meters in length and they're well equipped with leak detection technology to ensure a safe and secure,
uncompromised transport. As I mentioned before,
technical and challenges include insulation, managing
ball of gas for liquefaction and economy of scale. This schematic visualizes what
happens when LNG is unloaded. Once the LNGs return at an import and regasification terminal they're pumped to the required pressure
and then vaporized to a high pressure gas
sales pipeline where they go to various homes and commercial businesses in the form of CNG or
compressed natural gas, which is stored up to a few thousand PSI. Because LNG is much dense
than compressed natural gas, higher amounts of gas are
able to be transported for the same amount of volumetric flow. Thus LNG pipelines are
costly because they account for the maintenance of
low pressure and assurance of preventing regasification
through mechanical insulation. While on the other hand,
compressed natural gas requires much less capital
intensive equipment. So in this video, we
cover what natural gas is, as well as why and how we liquefy, store and transport natural
gas in a cost effective and responsible manner. As EQT CEO Toby Rice states, "The best way to combat climate change is a dramatic increase
in liquified natural gas, which would supersede coal
and electricity generation." With the trend and decrease
in global emissions, natural gas will continue to be the bridge towards
sustainable future. Thank you so much for watching. I hope you'll learn
something for this video, make sure to follow and subscribe for more content like these. Feel free to reach out with any questions and comments and feedback
that y'all might have. And as always, never stop learning. (upbeat music)