For nitrogen blanketing of an activated carbon filter in a chemical park Mankenberg Armaturen GmbH uses a combination of a pressure reducing valve and a back pressure regulator.

A special chemicals company based in southern Germany produces semi-finished and finished products with a typical nitrogen-carbon-nitrogen (NCN) sequence. These are used in a variety of industries, for ex. fine chemicals, automotive engineering, renewable energies or agro-industry.

Back pressure regulator for milibar control

The chemical park produces, among other things, lime-nitrogen and calcium carbide, the production of which also generates hydrogen sulphides. These are highly flammable and very reactive. They are pre-dried and filtered through an activated carbon filter to prevent the formation of sulphuric acid. What remains is purified gas, which is then burnt in an exhaust gas incinerator and discharged into the environment.

Nitrogen inertisation of activated carbon chambers

The cleaning of hydrogen sulphide in the filter bunker is basically necessary to operate the downstream exhaust gas catalytic converter. The previously dried gas flows through the chamber of the vertically arranged activated carbon filter from bottom to top before it is passed on for combustion.

Since the exothermic adsorption process can lead to overheating in the filter bunker and thus considerably increase the risk of explosion, the activated carbon filter is flushed with nitrogen.

Combination of two valves

A combination of the DM 762 pressure reducing valve and the UV 3.0 back pressure regulator from Mankenberg is used for this purpose. The inerting ensures a slight overpressure in the chamber and the risk of ignition of the activated carbon is avoided.

The Mankenberg valves absorb fluctuating pressures and keep the pressure of the inert gas constant. The pressure reducing valve DM 762 reduces the system pressure to 0.01 bar during inerting. It has an outlet pressure control range of 0.05 to 0.28 bar and is arranged in the line upstream of the UV 3.0. The back pressure regulator UV 3.0 is used to protect the process.

The diaphragm-controlled, spring-loaded back pressure regulator is a single-seated straightway valve with a soft-seated plug. Its construction completely from deep-drawn stainless steel provides corrosion resistance in the critical atmosphere of the activated carbon bunker.