NOVELTY - A biomass was gasified by subjecting a discharge stream of a first stage to an intermediate stage for 1 second in a separate space at 700-900, in order to separate the tar present in the first stage.    USE - For gasifying biomass.    ADVANTAGE - The invention enables tar emissions to be greatly restricted and the efficiency of the gasification of biomass to be increased considerably, and the health risks can be limited since there is no need to handle various types of tar which are released. The nitrogen present in the air introduced at inlet is discharged via the outlet for flue gas. Thus, the calorific value of the product gas obtained at outlet does not decrease, and the possible applications are widened. As compared to product gas obtained with a conventional gasifier, i.e., a gasifier which is not indirect, the calorific value is approximately twice as high (approximately 15 MJ/m3. It has been found that the invention makes it easy to achieve a stable equilibrium.    DETAILED DESCRIPTION - Gasification of biomass involves (a) in a first stage, mixing the biomass with an auxiliary medium; (b) gasifying the resulting mixture; (c) discharging the gasification products comprising tar and the auxiliary medium; (d) separating the discharge stream into a stream of solid particle and a gaseous stream comprising product gas; (e) discharging the gaseous stream; (f) feeding the solid particles to a second stage; (g) burning the solid gasification products in the second stage; and (h) feeding the auxiliary medium to the first stage. Between the first and second stages, the discharge stream of the first stage is subjected to an intermediate stage for 1 second in a separate space at 700-900degreesC, in order to separate tar.    An INDEPENDENT CLAIM is included for a device for gasifying biomass comprising:    (1) a first reactor chamber (3) provided with a feed (9) for biomass;    (2) a feed (11) for auxiliary medium and a discharge (10) for the first product stream;    (3) a second reactor chamber (4) provided with inlet (12) for the solid particles from the first product stream and auxiliary medium;    (4) a discharge (13) for combustion gases and a discharge for auxiliary medium connected to the feed for auxiliary medium leading into the first reactor chamber;and    (5) a separation device for gases comprising a discharge (6) for product gas being arranged between the first and second reactor chambers.    The separation chamber is designed in such a manner that the mean residence time of the first product stream is at least 1 second.    DESCRIPTION OF DRAWING(S) - The figure shows a device used to carry out the invention.    Housing (2)    First reactor chamber (3)    Second reactor chamber (4)    Product gas discharge (6)    Biomass feed (9)    First product stream discharge (10)    Auxiliary medium feed (11)    Solid particle inlet (12)    Combustion gas discharge (13)