New technology of water purification of organic inclusions or solutes by using a filtration combustion recuperative reactor ("tube-in-tube" type) is investigated numerically. An acetone aqueous solution served as a model liquid. The model was verified on the basis of experimental temperature measurement data. The physical reason for the comparatively high energy consumption at the startup of the reactor has been revealed. The minimum concentration limit (MCL) for self-sustained operation as a function of the reactor length, size of a packed bed particle, and of the heat transfer coefficients was investigated. Thermal insulation has the strongest effect on MCL, which may be as low as c = 0.12 for the acetone aqueous solution and characteristic length of the reactor L = 0.5 m. Increase of the length of the reactor has a limited potential for reduction of the MCL. This is connected with the exponential saturation of the recuperated heat and simultaneous increase in the heat loss with the length of the reactor. In the case of proportional elongation of reactor, when the "dead end" area grows, not a decrease but an increase in the MCL value is observed. (C) 2010 Elsevier Ltd. All rights reserved.