An efficient, low cost, and high power microwave generator is designed for the regeneration of the activated carbon that has been used for removing various organic solvents from filtering the water and the vented air, etc. Electric properties of the spent carbon such as the permittivity and the conductivity may be measured by using the transmission measurement through the rectangular waveguide filled with the spent carbon as a function of the moisture content and the mesh size of the spent carbon. A planar cavity heating the spent carbon inside the cavity uniformly up to its temperature 800 degrees in centigrade at 2.45GHz and regenerating about 3 tons per day is suggested. 40kW of the microwave output power is needed for this capacity and the skin depth of 4.6 cm calculated from the measurement of the conductivity of the spent carbon suggests the thickness to be 6 cm for the illumination of the microwave power from both the top and the bottom surfaces of the cavity. The commercial numerical program is used to check the uniformity of the heating, the minimization of the mutual coupling between the magnetrons, the impedance matching, and the shielding of the electromagnetic wave from the heating area inside the cavity. An experimental set supplying 5kW of the microwave power and having same dimensions of the thickness and the width except the length of the cavity is built.
