NOVELTY - An apparatus for continuous preparation of disintegrated biomass sludge, comprises: first positive displacement pump (2), first piping (6, 12) connecting outlet of first pump to inlet of first pump so as to form closed loop, first disintegration device (20) which is provided in first piping and configured to disintegrate biomass sludge supplied to it, second pump (14), and third pump (16); where outlet of second pump is connected to first piping and inlet of third pump is connected to first piping upstream of position where outlet of second pump is connected to first piping.    USE - As apparatus for continuous preparation of disintegrated biomass sludge (claimed).    ADVANTAGE - The apparatus and method provide continuous preparation of high solid content pumpable biomass sludges. The second pump acts as feed pump for feeding biomass sludge to be disintegrated into first piping. The third pump acts as discharge pump for discharging disintegrated biomass sludge from first piping. In this way, apparatus can be operated in fully continuous manner. The serial arrangement of two pumps having different flow rates, in operation of apparatus, results in reduced pressure in first piping between first and second pump. The amount of pressure reduction can be controlled by setting difference in flow rates of two pumps. The reduced pressure in first piping leads to sucking in of steam or steam containing gas from steam source through steam mixing device. In this regard, pump arrangement acts as vacuum pump, pumping steam or steam containing gas into first piping, where sludge itself provides sealing for two pumps. Therefore, no separate injection devices are required for injecting steam or steam containing gas into first piping. Further, due to vacuum suction effect, steam or gas to be injected does not have to be provided at high pressure. Hence, apparatus can be particularly advantageously used with condensing gases such as low pressure steam. When condensing gases come into direct contact with sludge in first piping; reduced pressure in piping causes condensation in highly effective manner. In this way, suction capacity of pump arrangement for condensing gases such as low pressure steam is multiplied. The apparatus allows for forming very high solid content of resulting sludge because disintegration device is always fed with mixture of pre-cut material with only some previously untreated material added by feed pump(s). The condensation of steam e.g. low pressure steam; also provides part of water required for many input materials to reach intended solid content of produced sludge. Further steam heating of sludge, in particular sludge containing biomass fibers, by first steam mixing device aids in mechanical disintegration of sludge.    DETAILED DESCRIPTION - An apparatus for continuous preparation of disintegrated biomass sludge, comprises: first positive displacement pump (2), first piping (6, 12) connecting outlet of first positive displacement pump to inlet of first positive displacement pump so as to form closed loop, first disintegration device (20) which is provided in first piping and configured to disintegrate biomass sludge supplied to it, second pump (14), and third pump (16); where outlet of second pump is connected to first piping and inlet of third pump is connected to first piping upstream of position where outlet of second pump is connected to first piping. The apparatus further comprises fourth positive displacement pump (4) provided in first piping downstream of first positive displacement pump, first steam mixing device (8) provided in first piping between first positive displacement pump and fourth positive displacement pump, and first steam source (10) which is in fluid communication with first steam mixing device and configured to supply steam or steam containing gas to first steam mixing device, where first positive displacement pump and fourth positive displacement pump are configured, so that in operation of apparatus, flow rate of first positive displacement pump is smaller than flow rate of fourth positive displacement pump, and first steam mixing device is configured to mix steam or steam containing gas supplied by first steam source with biomass sludge in first piping. The apparatus further comprises second piping (24) connected to outlet of third pump and second disintegration device (20') which is provided in second piping downstream of third pump and configured to disintegrate biomass sludge supplied to it. The apparatus further comprises fifth pump (22), where inlet of fifth pump is connected to second piping, second steam mixing device (8') provided in second piping between third pump and fifth pump, and second steam source (10') which is in fluid communication with second steam mixing device and configured to supply steam or steam containing gas to second steam mixing device, where third pump and fifth pump are configured so that, in operation of apparatus, flow rate of third pump is smaller than flow rate of fifth pump. Further third pump and fifth pump are configured so that third pump is operating as booster pump for fifth pump, maintaining pressure level in second piping that is above that in first piping, and second steam mixing device is configured to mix steam or steam containing gas supplied by second steam source, which is providing steam at pressure level above that maintained in second piping by third pump and fifth pump, with biomass sludge in second piping. The apparatus further comprises buffer vessel (18) provided in first piping and capable of accommodating part of biomass sludges. An INDEPENDENT CLAIM is included for method for continuously preparing disintegrated biomass sludge using the apparatus.    DESCRIPTION OF DRAWING(S) - The figure shows schematic view of the apparatus for heating and disintegrating biomass sludge or slurry.    First positive displacement pump (2)    Fourth positive displacement pump (4)    First piping (6, 12)    First steam mixing device (8)    Second steam mixing device (8')    First steam source (10)    Second steam source (10')    Second pump (14)    Third pump (16)    Buffer vessel (18)    First disintegration device (20)    Second disintegration device (20')    Fifth pump (22)    Second piping (24)