To make sludge useful as a fertilizer without disposing of it inefficiently.

An exhaust G2 is extracted partly from a flue gas flowing in a kiln exhaust gas duct connecting an end 2a of a cement kiln 2 and the lowest cyclone 5. Dust in the exhaust gas is scrubbed with water in a wet dust collector 12 and a filter 15. An apparatus 1 for manufacturing a fertilizer includes a spray dryer 18 for drying a filtrate L2 obtained by scrubbing using an exhaust gas G3, a crushing flash dryer 10 for drying sludge W1 using the exhaust gas G3, and a granulator 19 for mixing a dried product P of the spray dryer 18 and a dried product W1 of the crushing flash dryer 10 to granulate them. A fertilizer M manufactured in the apparatus 1 for manufacturing a fertilizer includes potassium chloride (KCl) in addition to nitrogen (N) and phosphoric acid (P) contained in the dried products of the sludge, which are three elements of a fertilizer, and thus can be effectively used for growing plants.

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