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 Inert Gas Generators

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The picture represents a standard Inert Gas Generator (FU type) complete with air fans, fuel pumps, deck water seal and P/V breaker.

Alfa Laval Smit Combustion is a saturated inert gas generator with low pressure, which produces inert gas by
combusting fuel oil with air controlled combustion chamber.
Smit inert gas generators are typically found on chemical tankers and product tankers. The inert gas generators produces inert gas by combusting fuel oil with air.
Monitored by a specially designed oxygen analyzer and indirectly cooled by seawater, the combustion process is soot-free, thanks to a unique Ultramizing system (blue flame) that ensures complete combustion even in practical-load conditions.
In a second stage, after-cooling and sulphur oxide washing are preformed directly in a specially developed spray and cooling system.

How it works

Fuel oil and air are combusted in the generator to produce hot inert gas with an oxygen content of 2-4%. The combustion process is soot-free thanks to the unique Smit Ultramizing system, which ensures complete combustion even in partial-load conditions down to 25%.
In the scrubber section of the generator, the inert gas is directly cooled by a  spray and cooling system, which at the same time washes out the sulphur oxides. The cooled inert gas then flows from the generator to the cargo tank through a deck water seal. This seal is a safety device that continuously prevents any backflow of gas from the cargo tank towards the inert gas system in the engine room. To prevent overpressure or vacuum in the cargo tank, a pressure/vacuum-breaker is installed.

Smit LNG

Alfa Laval Smit LNG/LPG is a dry inert gas generator with low pressure and low dew-point.

The most complex inert gas generators are installed on LNG carriers, where very dry inert gas is required and consist of four main components: generator, cooler, chiller and dryer unit.

The cooler, which has gas contact surfaces of SUS 316 for lifetime service, takes up minimal space due to the low-temperature output of the generator. Using water from the chiller, it stabilizes the heat radiation in all conditions.

The dryer unit is redundant and provides additional security. The entire installation is horizontal and allows easy maintenance, although maintenance is seldom required.

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How it works

For gas- and chemical transportation the inert gas needs to be of high purity. For many applications, oxygen levels of 0.5% or even 0.1% are required, in combination with a water dew-point of about -45 °C and sometimes lower (-65 °C). Also here, the burner is the heart of the system as the inert gas needs to be absolutely soot free in the first place. This is achieved with the Ultramizing Conbustion system.
When the gas leaves the generator, it has the right composition, but it is saturated with 100% water and has to be dried.
The drying process takes place in two steps. In the first step of the refrigerant cooler, the gas temperature is lowered to 5 °C which results in condensation of a great quantity of water.
In the second stage the inert gas is dehumidified further in a double vessel type drying unit using activated alumina or adsorbent. The whole process operates under a pressure of about 0.3 bar(g).

To learn more about the IGG system please go to:

http://www.alfalaval.com/products/process-solutions/safety-solutions/Combustion-type-inert-gas-system/