Suspension preheater

Suspension preheater for heat exchange between gas and fines before a kiln (5), containing

• (a) a plurality of cyclone separators (1 to 4) lying one above another with their axes arranged approximately vertically and each having
• (a.sub.1) an essentially straight upper part with a flat cyclone cover wall (9, 9.sub.1),
• (a.sub.2) a lower part (10) which is axially connected to the upper part,
• (a.sub.3) an inlet pipe connection (1a, 11) which opens approximately tangentially into the upper part for a gas-material mixture,
• (a.sub.4) a gas outlet pipe (12) leading upwards from the region of the cyclone cover wall (9, 9.sub.1) and
• (a.sub.5) a gas outlet pipe (13) connected to the lower end of the lower part (10),
• (b) gas and material pipes (14 to 16, 17 to 19) which connect the cyclone separators (1 to 4) one below another and which for their part are connected to the corresponding inlet pipe connections as well as gas and material outlet pipes of the cyclones,
• (c) a kiln exhaust gas pipe (7) which connects at least the lowest cyclone separator (1) to the kiln (5) and is at the same time constructed as a calciner, the upper section of the said pipe (7) being bent in a loop and opening into the gas inlet pipe connection (1a) of the lowest cyclone separator,
• characterised in that the cyclone cover wall (9, 9.sub.1) and the inlet pipe connection (1a, 11) of each cyclone separator (1 to 4) are inclined at an acute angle (.alpha.) with respect to the horizontal (H), and the mouth end (7a') of the loop-shaped section (7a) of the kiln exhaust gas pipe (7) as well as the inlet pipe connection (1a) and the cyclone cover wall (9.sub.1) of the lowest cyclone separator (1) have an inclination (.alpha.) which falls in the gas flow direction, whereas the inlet pipe connections (11) and the cyclone cover walls (9) of all the other cyclone separators (2 to 4) have an inclination (.alpha.) rising in the gas flow direction.