Abstract: Process and a plant to extract and concentrate tannins from wood and from other solid natural products containing it characterized in that the solid products are subjected to an extraction (1) by percolation with water and/or steam and the thus obtained tannin solution is subjected to nanofiltration (5).

Abstract: A reversible heat pump providing a generator of refrigerant fluid in a vapor state produced by a rectifying column having perforated plates, with a hydrostatic head on the plate assured by the surface tension of the liquid, a reboiler of the generator heated indirectly, a storage tank of the condensed refrigerant fluid which contributes to controlling the cycle pressure for optimizing the efficiency under partial load conditions, expansion valve for the condensed refrigerant which changes the flow section as a function of the pressure and controls the flow rate of the refrigerant for draining any impurity, electro valve reducing the load loss of the expansion valve during summer, a plate absorber with swirl grid providing a microdrop flow between poor solution and refrigerant, and a multi-way valve which allows the heat pump to be coupled with a split-exchanger by deviating the flows of the operating fluids according to the requirements so as to cause the split-exchanger to perform the function of a cold sour