Nitrogen is being used in different types of cargo operations in chemical tankers such as,
> Making inert atmosphere in tank above cargo
> Drying tanks before loading
> Pre -purging tanks
> Line blowing
> Inerting tanks during tank cleaning operations.
Regulation
> Capable of delivering inert gas with an oxygen content in the inert gas main of not more than 5% by volume at any required rate of flow
> system should have the capacity to maintain the positive pressure on cargo tanks at all times with an atmosphere having an oxygen content of not more than 8%
> system should have the capacity to maintain the positive pressure on cargo tanks at all times with an atmosphere having an oxygen content of not more than 8%
Different Types of Nitrogen Inerting Systems
> Nitrogen generators
> Nitrogen cylinders
> Liquid nitrogen
> Nitrogen cylinders
> Liquid nitrogen
Nitrogen Generators
Nitrogen generators are those types that generate nitrogen on board which can be directly supplied to the tanks or can be stored in the buffer tank. Usually nitrogen Generators are of two types; Membrane separation type and Pressure swing adsorption model.
Liquid Nitrogen
Liquid nitrogen is manufactured in a typical nitrogen plant with a purity of 99.9%. Liquid nitrogen is supplied from a specialised tanker directly to the ship. Nitrogen is stored on board at a temperature of below -190 °c in liquid form.
Nitrogen cylinders
In some ships nitrogen cylinders are provided for inerting purposes. These cylinders may be from shore or vessel that normally have generators to fill the bottles. Cylinders are connected in parallel to the central main line which leads the nitrogen in to the tank. Each cylinder has isolation valves and each branch from the main is also capable of isolation.
Why Inert gas is not used in chemical tankers for inerting?
On certain chemicals, inert gas make some hazardous reactions which may affect the quality of the cargo also. Inert gas is usually associated with oil tankers, sometimes it is used in chemical tankers also, provided ship have appropriate equipments.
Questions that You Can Answer.
> Use of nitrogen in chemical tankers
> Why Inert gas is not used in chemical tankers?
> Different types of nitrogen inerting systems on ship
> Different types of nitrogen Generators