New Zealand Journal of Agricultural Research abstracts

---

Chemical properties of fluidised bed boiler ash relevant to its use as a liming material and fertiliser

H. L. WANG
M. J. HEDLEY
N. S. BOLAN

Soil Science Department
Massey University
Palmerston North, New Zealand

Abstract  A by-product from the New Zealand Dairy Corporation (NZDC) factory at Te Awamutu, fluidised bed boiler ash (FBA), contains agronomically useful amounts of lime and sulphur (S). The FBA is produced from injection of limestone into the combustion chamber to absorb and reduce sulphur dioxide (SO2) emission from burning high S coal. NZDC FBA, an alkaline material (pH in water = 12.4, 51.8% calcium carbonate (CaCO3) equivalent), contained 6.2% S, 25.4% calcium (Ca), and negligible amounts of phosphorus (P), potassium (K), and magnesium (Mg). Approximately 50% of the S in the slaked FBA was water-soluble (gypsum, CaSO4.2H2O) with the remainder being ettringite [Ca6Al2(SO4)3(OH)12.26H2O] which has low solubility in water. The soluble fraction had release characteristics similar to the gypsum in single superphosphate. The "lime" in FBA is mainly in hydroxide form and it is a quicker-acting, more caustic liming material than limestone. The concentrations of heavy metals were low in NZDC FBA (<= 6.5 mg/kg) and are unlikely to cause toxic problems at normal rates of S fertiliser application and lime requirement.

Keywords  aqueous extraction; calcium; fluidised bed boiler ash; gypsum; lime; sulphur; single superphosphate

New Zealand Journal of Agricultural Research, 1995, Vol. 38: 249-256

0028-8233/95/3802-0249 $2.50/0 (c) The Royal Society of New Zealand 1995

PDF file of entire paper: medium quality (624K); (scanned from paper original: notes about this process)

---

This year's abstracts | Journal home page | All abstracts | Publishing home page