INDUSTRIAL GAS STORAGE TANKS

 

INDUSTRIAL GAS STORAGE TANKS

·         Most materials which are in gaseous state at ambient pressure and temperature are supplied in the form of compressed gas.

·         The gas is compressed into pressure vessels for storage (like tube trailers, gas cylinders, or gas canisters) using a gas compressor through piping systems.

·         Gas cylinders are most commonly used for gas storage, with large numbers being produced at “cylinder fill” facilities.

·         However, all of the industrial gases are not supplied in gaseous phase.

·         Some gases are vapours, liquification for which can be done under pressure alone at ambient temperature, so these gases can be supplied in the form of a liquid too in a suitable container.

·         These gases are useful in the form of ambient refrigerants owing to this phase change.

·         The well-known industrial gases having this property are – sulfur dioxide, butane, propane, and ammonia.

Delivery of Gas

·         The important industrial gases are bulk produced and delivered by pipeline to customers.

·         However, they can be packaged and then transported too.

·         Most of the gases are sold inside gas cylinders and a few gases are sold in the form of liquid inside suitable containers or in the form of bulk liquid that’s delivered by truck.

·         Originally, the industry supplied gases within cylinders to prevent any necessity for generation of gas locally.

·         However, for large customers like oil refineries or steelworks, a large-sized gas production plant can be built nearby (known as “on-site” facility) for avoiding the use of cylinders in large numbers manifold together.

TYPES OF INDUSTRIAL GAS STORAGE TANKS

·         There are different types of storage tanks in industries available.

·         The type of industrial gas storage tank required by a plant depends on several factors including the holding capacity, measurement, and shape of the container.

·         The most common types of industrial tanks are as follows:

Internal Floating Roof

·         Internal floating roof storage tank, popularly known as IFR, is employed for liquids having lower melting points like Gasoline and Ethanol.

·         These tanks have a cone shape with a floating roof within, hence its name is floating roof tank.

·         The roof suspended within the storage tank moves along the level of the fluid, i.e., with the increase of the liquid, the roof moves up and with the lowering of the liquid, the roof goes down.

·         If the tank has no liquid, the roof of the tank is held by the legs on which it is placed.

Bullet Tanks

·         Bullet tanks are sphere and flat-shaped industrial storage tanks used mostly in large plants.

·         These types of tanks are usually preferred over the other types to store liquefied gases like Butane and Ammonia for which the melting point is very low.

·         Its name derived from the tank’s long cylindrical form, the tank stores these liquids at a temperature below -148 degrees Fahrenheit.

·         These types of tanks mostly have the ability to hold huge amounts of gases that range from 5,000 to 30,000 gallons.

·         Additionally, they can be installed horizontally as well as vertically.

·         A unique characteristic of bullet tanks is that they have the ability to hold fuel as well as other additives required for the operation of the plant.

LNG Storage Tank

·         LNG storage tank or liquefied natural gas storage tank is specially used to store Liquefied Natural Gas.

·         These types of storage tanks in industries are available in LNG carriers, in ground, or above ground.

·         LNG storage tanks have the special characteristic of being able to hold LNG at the extremely low temperature -162 °C.

·         These tanks consist of double containers – the inner container holds LNG whereas the outer one holds insulation materials.

·         The full containment storage tank makes the most common type of tank.

·         Roughly, the diameter of such a tank is 75 m and the height is 55 m (180 ft.).

·         If the LNG vapours aren’t released in such tanks, the temperature and pressure inside the tank would keep on rising.

·         Being a cryogen, Liquefied Natural Gas is stored in its liquid form at extremely low temperatures.

·         The temperature inside these tanks would stay constant in case the pressure is maintained as constant by releasing the boil off gas from the tank.

·         Such phenomenon is referred to as auto-refrigeration.

DIFFERENCE BETWEEN COMPRESSED NATURAL GAS & LIQUEFIED NATURAL GAS

·         Compressed Natural Gas (CNG) and Liquefied Natural Gas (LNG) are often confused with each other.

·         Both are natural gas in stored form.

·         The chief difference between the two is that Compressed Natural Gas is stored at high pressure and ambient temperature.

·         Whereas Liquefied Natural Gas is stored at ambient pressure and low temperature.

·         Under their respective conditions of storage, CNG is supercritical fluid and LNG is liquid.

·         The cost of storage and production is lower for CNG than LNG since it doesn’t need cryogenic tanks and a costly cooling process.

·         However, for CNG, much larger volume is required for storing an energy equivalent of petrol or gasoline as well as extremely high pressures (205 to 275 bar, or 3000 to 4000 psi).

·         Due to this Liquefied Natural Gas is often employed for the transportation of natural gas over long distances, in pipelines, trains, or ships, where conversion of the gas into CNG is done before distributing to end user.

SAFETY MEASURES TO PREVENT TANK FAILURES

·         Several catastrophic storage tank failures have occurred in the past, one of them being the failure that happened on January 14, 1919 at Boston in Massachusetts.

·         This Boston molasses disaster occurred due to poor construction and design.

·         The wall was too thin to withstand loads repeatedly from the contents.

·         Testing of the tank had not been done before use by water fill up.

·         The tank was poorly riveted also.

·         Several other accidents have been caused by tanks, often resulting from sub-standard steel or faulty welding.

·         Some more common problems around the seal of tanks have been resolved to some extent by new inventions.

·         However, when empty, another problem is presented by storage tanks.

·         If the tanks have been used for holding oil products or oil, like gasoline, the tank atmosphere may become highly explosive since the space is filled up with hydrocarbons.

·         In such a situation, if welding operations are carried out, the contents can easily get ignited by the sparks, leading to catastrophic results for welders.

·         This problem is quite like that of the empty bunkers over tanker ships, which now need to use inert gas blanket for preventing the building up of explosive atmospheres from the residues.

·         So, industrial storage tank of any type should be efficiently designed and constructed, adhering to all safety standards, and following all safety rules and regulations.

·         They should also be maintained well, with quality and safety checks and inspections being conducted at regular intervals.