Influence of chlorine, sulfur and phosphorus on the volatilization behavior of heavy metals during sewage sludge thermal treatment

Abstract

Chlorine, sulfur and phosphorus were selected as element donators to investigate their effect on the volatilization behavior of heavy metals in sludge sewage incineration. Principal component analysis indicated that the promotive effect on the volatilization of heavy metals was followed by chlorine, sulfur and phosphorus. This result was proved to be correct by total release of heavy metals in sewage sludge incineration using different element donators. The release of heavy metals was very chlorine dependent, especially cadmium (Cd), lead (Pb) and nickel (Ni). When chlorine content was in the range of 0.1-0.5wt%, the increase of the volatilization rate was 44.9% for Cd, 6.8% for Pb and 4.6% for Ni, respectively. Although sulfur contributed to the promotion of the volatilization of heavy metals, excess oxygen impaired the promotive effect of sulfur on the release of heavy metals from the condensed phase. For phosphorus, solidifying heavy metals was dominant. Energy analysis showed that metal chlorides and sulfides were prone to volatilize or to be decomposed at elevated temperature compared with sulfates and phosphates owing to low binding energy in absolute value (VLFA). It was the difference of binding energy that led to the different volatilization behavior of metal compounds in a high temperature, oxygen-enriched atmosphere.

Cations and Anions in Sewage Sludge from Gaza Waste Water Treatment Plant

“…Under pH value 6.78, phosphate ion tends to precipitate from the solution. Similar observations were given recently by [25].…”

Trace element partitioning in ashes from boilers firing pure wood or mixtures of solid waste with respect to fuel composition, chlorine content and temperature

“…It is clear that highly volatile (Hg, Cd) and medium volatile (Pb, Zn, As) elements showed an increased distribution to fly ash with an increase of chlorine from 1% at Umeå to 2% at Söderenergi waste fuel. These results are in agreement with previously reported values (Wang et al, 1999;Chiang et al, 2007;Luan et al, 2013). The primary reason for an increased partition to fly ash could be the formation and vaporization of metal chlorides owing to high chlorine content in input waste of Söderenergi (Chiang et al, 1997).…”

“…Resulting wood product is sold to district heating plants (Andersson and Tullin, 1999). Both chlorine and sulfur are critical elements in the waste fuel with respect to element speciation, partitioning to various combustion fractions and corrosion in the boilers (Sorell, 1997;Luan et al, 2013). Speciation of trace elements is believed to be influenced by the type of chlorine bond because organic chlorine (PVC, C 2 Cl 4 ) is expected to be released as HCl in gas phase and reacts more eagerly with trace elements in comparison to inorganic (NaCl, KCl) chlorine .…”

“…Increasing feed chlorine causes an increase in the partitioning of trace elements to the fly ash and flue gases due to the formation of stable and highly volatile metal chlorides (Chiang et al, 1997;Tomoda et al, 2006). Sulfur has been reported to have an opposite effect on trace elements distribution by forming condensed sulfate phases (Luan et al, 2013). In the present study, grate fired facilities at Umeå and Söderenergi can be coupled (section a) for the discussion of trace elements distribution in residues with respect to chlorine and would offer a good comparison since input waste contains 1% and 2% chlorine, respectively, and both are using a grate (Table 1).…”

Effect of different sulfides on cadmium distribution during sludge combustion based on experimental and thermodynamic calculation approaches

“…Previous studies (Luan et al 2013;Jiao et al 2011;Zhang et al 2008) have indicated that the partitioning behavior of heavy metals during waste incineration is influenced by the composition of the gas stream, incineration temperature, concentration of metals in the waste, and concentration of chlorine (Cl), sulfur (S), H 2 O, and so on. Because both raw sludge and dewatered sludge have high moisture levels and a low heating value, adding auxiliary fuel is necessary for the independent incineration of sludge or co-combustion of the sludge with MSW and coal.…”