THE PROBLEM OF MECHANICAL RECOVERY EFFICIENCY (I)

Mechanical recovery is the most commonly used oil spill response technique and it’s accomplished by devices called "skimmer" which recover hydrocarbons and fats floating on the water surface.

Several types of skimmer exist among which weir skimmers and oleophilic skimmers are widespread.

The first ones, thanks to an onboard pump, create an inlet flow through a tared floating ring that floats on the water but not on lighter fluids, as most hydrocarbons are; so the incoming fluid is, in theory, the spilled oil.

The second ones make a more accurate recovery thanks to the adhesion of oil to a rotating surface, to which water does not adhere. Different contact surfaces may be used such as brushes, disc, drum, mop

In all cases, after recovery, oil is pumped into temporary tanks while cleaning operations are developed.

Despite manufacturers' efforts to improve the effectiveness of their equipments, the reality is that Recovery Efficiency (RE = Recovery Efficiency,%) of skimmers is very lower than 100%. (The recovery efficiency is defined as the ratio between the volume of oil recovered and the volume of total fluid recovered by the skimmer, expressed as a percentage)

There are different reasons that justify variable and imperfect performance of skimmers:

• Type: Weir skimmers RE is lower than on oleophilic skimmers. Among the oleophilic skimmers considerable differences exist depending on the type.
• Construction materials: In the case of oleophilic skimmers different studies show strong differences on skimmer performance depending on the material used in the construction of the contact material (polypropylene, polyethylene, aluminum, pvc, stainless steel, ...).
• Operational Speed: Each type of skimmer presents an ideal operational speed (depending on the viscosity of the fluid recovered) beyond which water content in the recovered substance increase, thereby decreasing by the RE.
• Viscosity of spilled oil at the moment of the cleaning operations
• Sea state and weather: The worse the state of the sea and the higher the waves, the lower skimmer RE.

In short, if existing skimmer Recovery Efficiency (RE) in ideal conditions ranges between 50% and 85-90%, we can say that in real conditions it will hardly exceed 50%. Ideal conditions can only be given in cases of calm sea and in the presence of a high concentration of hydrocarbons, as well as in industrial facilities.

The consequence is that the solution to the spill causes a further problem: the presence of equal parts of water in the recovered substance and the need to purify it so that water can be returned to sea with acceptable / legal hydrocarbon concentrations.

CURRENT STATE OF TECHNOLOGY

New technologies are based on energy saving and the use of "clean" energy. Process heat recovery is being implemented on industrial and domestic applications with great success. In the same way the use of renewable energy and energy sources existing in the place of exploitation produce significant economic savings and significant environmental benefits.

By sector:

• Automotive Sector: electric and hybrid vehicles. We are experiencing the boom in electric vehicles and industry around it: vehicle manufacturers, charging systems development, evolution in batteries,...

• Nautical Sector: The eclosion of electric vehicles and related technologies is pushing other sectors such as yachting to develop new products with fully electric motor. Renewables are gaining importance applied directly as the main power source or secondary power source on traditional boats.

• Construction sector: Heat recovery from the exhaust air  or flue gas boilers and generators are producing significant economic benefits for users and. Renewable energies play an increasingly important role in the energy autonomy of the buildings.

• Industrial sector: The economic crisis has led, contrary to what one might think, to increased investment in improved techniques involving energy savings and thus reducing production costs. Also more and more rules and regulations require a greater control of waste generated and the adoption of treatment systems.

All sectors have experiensed a great technological leap in the last few years as far as energy management and respect for the environment is concerned.

OIL SPILL EQUIPMENT CURRENT STATE

Oil Spill Response sector has not properly received, in general terms, the message of today's society. Technological developments and the tendency to reduce overall energy consumption don’t get reflected in the available equipment for pollution control.

• Highly inefficient and polluting engines.

• Ineffective management of power units and energy waste during use.
• Total absence of energy recovery methods.
• Minimal presence of the electric motors, absence of use of renewable energy.
• Total lack of energy planning.
• Minimum electronic management for fear of failure.

• Antediluvian designs.
• Minimum level of technology, and especially,

• Lack of attention to the real effectiveness of their processes.