Abstract: Calcium carbonate residue is a waste residue discharged in the ammonium sulfate production from phosphogypsum.Its main mineral composition is calcium carbonate，which can be converted into high-activity lime by calcination process. This research used high solid/gas ratio suspended calcining technology to process calcium carbonate residue in a pilot scale test.Results showed that under suspension calcining process，the apparent decomposition rate of CaCO3 in product could reach more than 95% and also with high activity.On basis of that，an industrial scale active lime production line using suspended calcining-rapid cooling technology with high solid/gas ratio was built by cooperating with Guizhou Wengfu Phosphate Fertilizer Plant. The mass fraction of CaO in product was as high as 59%，the apparent decomposition rate of CaCO3 reached 97.7%，and also a high activity focused at 160~180 s.Comparing with the traditional firing device， suspended calcining had a better thermal efficiency (energy consumption: 4 402 kJ/kg) and product quality.

Key words: phosphogypsum, calcium carbonate residue, high solid/gas ratio, suspension calcining