Plants for fumes removal
Release of acid fumes inside the drums represents one of the most frequent situation of risk in tannery. Sulphide present in the limed pelts is released as gaseous hydrogen sulphide when the pH is reduced for deliming and pickling. The gas saturate the free volume in the drum and escapes through the door when opened. Hydrogen sulphide exerts a toxic effect on the nervous system whose effects depends on concentration and time of exposure. For this reason, laws and rules concerning safety of work impose the installation of systems suitable for sucking and removal of such acid gasses.

Technical features
The plants Tower consist of a suction main to which each drum is connected through an hollow axle. Fresh air flowing into the drum through the opposite axle removes continuously the acid gas and carries it to on scrubber (tower) where hydrogen sulphide is removed by counterflow absorption in a solution of caustic soda. The gas enters in the base of the tower and rises through the intermediate section filled up with plastic bodies. The basic solution drops from the top percolating through the filling bodies and is collected in the base tank from where is recyrculated over the adsorption section by means of a centrifugal pump. The plant is equipped with specific safety systems that put the operator in a condition to evaluate the level of risk before opening the drum’s door checking that:
• Sufficient time passed from the start of suction and so the gas has been already washed out from the drum;
• Enough air enters into the drum;
The measurement of the air flow is obtain by a detection device, the alerts are clearly displayed on switchboards located in correspondence of each drum and fitted with warning lights and/or acoustic:
• red: air suction not working properly;
• white: air suction running;
• acoustic alarm or flashing light: access to the drum happens before the time set.

The unpleasant odours diffused in the outside environment are certainly due to theemissions containing sulphuric gases deriving from waste liquids which go through the gridarea and the various adjacent waste collection pits.The companies concerned are the ones that discharge both basic waters containingsulphurs and acids into the waste liquid collection pit and grid during the processing cycle.As a consequence, it is possible that the waters and acids mix during discharge and thatsulphuric gases develop.To combat this problem we have created the MINITOWER system. The plant has the samecharacteristics and functions as the TOWER described above, only it is smaller in size.

LEGEND
1. Gas washing tower | 2. Fan | 3. Inspection hatch | 4. Check valve | 5. Detection device and flow control | 6. Panel control| 7. Valve “Clapet” | 8. Safety barrier | 9. Acoustic alarm | 10. Drift eliminaator | 11. Interception valves | 12. Output air | 13. Inlet air