粉煤灰固化处理生活垃圾焚烧飞灰效果研究

The Effect on Immobilization of MSWI Fly Ash with Coal Fly Ash

为了减少生活垃圾焚烧飞灰中重金属等污染物对环境的危害,以粉煤灰和脱硫石膏为原料对生活垃圾焚烧飞灰中重金属进行安全处理。采用机械力化学法探究了脱硫石膏与垃圾焚烧飞灰掺加比、(脱硫石膏+垃圾焚烧飞灰)与粉煤灰掺加比、球磨频率、球磨时间和养护温度参数对固化体性能的影响。并通过XRD和FTIR手段对垃圾焚烧飞灰中重金属的固化机制进行了研究。研究结果表明,采用机械力化学法能够显著提升粉煤灰的活性,并使制备出的固化体具有较高的抗压强度。当脱硫石膏与垃圾焚烧飞灰掺加比为1∶4,(脱硫石膏+垃圾焚烧飞灰)与粉煤灰为2∶3,球磨频率30 Hz,球磨时间2 h,养护温度60℃时,固化体28 d抗压强度达到22.3 MPa,并采用AAS测得固化体浸出液中Cd和Zn重金属的浸出量分别仅为0.015 mg/L和0.008 mg/L,均远低于GB 5085.3-2007规定限值。XRD和FTIR表征结果表明,固化体水化过程中生成了水化硅酸钙(C—S—H)和钙矾石(AFt)并分别主要以物理包裹和化学吸附的形式实现了垃圾焚烧飞灰中重金属的稳定化。

In order to reduce hazard of municipal solid waste incineration （MSWI） fly ash, coal fly ash and desulfurization gypsum were successfully used as raw materials to immobilize heavy metals from MSWI fly ash. The present research ex- plored the role played by mechanochemical method on immobilization of the MSWI fly ash. And the most important influ- encing parameters including desulphurization gypsum/MSWI fly ash ratios, （desulpburization gypsum and MSWI fly ash）/coal fly ash ratios, ball-milling frequency and time, curing temperature on the performance of the solidified wastes were investigated. And the immobilization mechanism of heavy metals from MSWI fly ash was characterized by XRD and FTIR. As results indicated, the mechanochemical method substantially promoted pozzolanic activity of coal fly ash and resulted in a high- er compressive strength to the solidified wastes. Under the optimized conditions that desulphurization gypsum/MSWI fly ash was 1：4, （desulphurization gypsum and MSWI fly ash）/coal fly ash was 2：3, milling frequency was 30 Hz, milling time was 2 h, the compressive strength of solidified waste was 22.3 MPa by cured after 28 d at 60℃. Meanwhile, the leaching amount of Cd and Zn which were detected by AAS were 0.015 mg/L and 0.008 mg/L respectively, much lower than the national standard value （GB 5085.3-2007）. Furthermore, XRD and PTIR analysis showed that the main hydration products of solidified waste were the calcium silicate hydrate （C--S--H） and ettringite（AFt）. And the heavy metals from MSWI fly ash mainly were physically encapsulated in C--S--H and chemically absorbed in the structure of AFt respectively.