Method for drying sludge

A method of drying a sludge containing organic substances and obtained subsequent to the dewatering of a suspension, comprising the steps of:

• providing a fluidized bed dryer having a sand layer which is fluidizable by means of a gas stream;
• indirectly heating the sand layer by means of stationary heat-exchanger bodies which are immersed in the sand layer;
• continuously feeding under pressure the sludge in pumpable condition into the fluidized bed dryer and from above onto the sand layer in counter-current flow to the fluidizing gas stream;
• coagulating the sludge to form sludge lumps in the heated fluidized sand layer;
• successively drying the sludge lumps in the sand layer;
• said step of successively drying the sludge lumps comprising transferring moisture from the sludge lumps to the fluidizing gas stream and successively abrading already dried layers of the sludge lumps by the fluidized sand of the sand layer, so that dry matter of the sludge is pulverized;
• continuously discharging the pulverized dry matter from the sand layer together with an exhaust-gas stream out of the fluidized bed dryer;
• and
• after departure of the pulverized dry matter with the exhaust-gas stream from the fluidized bed dryer, continuously separating the pulverized dry matter as a product from the exhaust-gas stream.