NOVELTY - Apparatus comprises: a first positive displacement pump (2); a second positive displacement pump (4); a first piping (6) connecting an outlet of the first positive displacement pump to an inlet of the second positive displacement pump; a steam mixing device (8) provided in the first piping between the first positive displacement pump and the second positive displacement pump; and a steam source (10) which is in fluid communication with the steam mixing device and configured to supply steam or a steam containing gas to the steam mixing device.    USE - The apparatus is useful: for heating of a biomass sludge (claimed) including manure (dung), night soil and sewage sludge, continuous preparation of a disintegrated biomass sludge using a disintegration device, hydrothermal carbonization processes or other hydrothermal or sludge hygienization processes, which is useful for manufacturing coal or coal-like materials recently attracted increasing attention, and for increasing the effectiveness of the evaporation cooling by the application of a vacuum; and as a gas scrubber and a vacuum pump.    ADVANTAGE - The apparatus prepares sludges with high solid contents tends to lead to a clogging of conventional disintegration devices. The apparatus can be operated in a continuous manner or in a batch-wise manner.    DETAILED DESCRIPTION - Apparatus comprises: a first positive displacement pump (2); a second positive displacement pump (4); a first piping (6) connecting an outlet of the first positive displacement pump to an inlet of the second positive displacement pump; a steam mixing device (8) provided in the first piping between the first positive displacement pump and the second positive displacement pump; and a steam source (10) which is in fluid communication with the steam mixing device and configured to supply steam or a steam containing gas to the steam mixing device, where the first positive displacement pump and the second positive displacement pump are configured so that, in operation of the apparatus, the flow rate of the first positive displacement pump is smaller than the flow rate of the second positive displacement pump, and the steam mixing device is configured to mix the steam or steam containing gas supplied by the steam source with a biomass sludge in the first piping.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of an apparatus.    First positive displacement pump (2)    Second positive displacement pump (4)    First piping (6)    Steam mixing device (8)    Steam source. (10)