Residue characteristics of sludge from a chemical industrial plant by microwave heating pyrolysis.

Sludge from biological wastewater treatment procedures was treated using microwave heating pyrolysis to reduce the environmental impact of a chemical plant. In this study, major elements, trace elements, PAHs and nitro-PAHs in raw sludge, and pyrolysis residues were investigated. The contents of major element from raw sludge were carbon 46.7 ± 5.9%, hydrogen 5.80 ± 0.58%, nitrogen 6.81 ± 0.59%, and sulfur 1.34 ± 0.27%. Trace elemental concentrations including Zn, Mn, Cr, Cd, As, and Sn were 0.410 ± 0.050, 0.338 ± 0.008, 0.063 ± 0.006, 0.019 ± 0.001, 0.004 ± 0.001, and 0.003 ± 0.002 mg/g, respectively. For various pyrolysis temperatures, Ca, Fe, Sr, Cr, and Sn contents remained at almost the same level as those in raw sludge. Results indicated that these elements did not easily volatilize. The content of 16 PAH species was about 4.78 µg/g in the raw sludge and 23-65 µg/g for pyrolysis residues associated with various temperatures. The content of ten nitro-PAHs was about 58 ng/g for the raw sludge and 141-744 ng/g for pyrolysis residues. The total nitro-PAH content was highest at 600 °C and then decreased when the temperature was over 600 °C. Total nitro-PAH content was about 247 ng/g at 800 °C.

Temperature influence on product distribution and characteristics of derived residue and oil in wet sludge pyrolysis using microwave heating.

Sludge taken from a wastewater treatment plant of the petrochemical industry was dewatered and pyrolyzed to produce liquid oil as an alternative fuel via microwave heating. Element contents of dried sludge were 45.9±3.85wt.% carbon, 7.70±1.43wt.% hydrogen, 4.30±0.77wt.% nitrogen and 3.89±0.52wt.% sulfur. Two major thermal degradation peaks of sludge were determined during the microwave pyrolysis process, one at 325-498K (most of the water was vaporized, and the weight loss was over 85wt.%) and the other at 548-898K for sludge constituent decomposition. Zn content was high in the dried raw material and residues. Other toxic elements such as Ni, Cr, Pb, As and Cd contents were 0.61-0.99, 0.18-0.46, 0.15-0.25, 0.018-0.034, and 0.006-0.017mg/g, respectively. About 14-20wt.% of oil was produced based on the dried sludge cake, and the oil major elements were C (69-72wt.%), H (5.7-6.7wt.%), N (1.9-2.2wt.%), and S (0.58-0.82wt.%). The heat values of liquid oils were 8700-9200kcal/kg at 400-800°C.

Element and PAH constituents in the residues and liquid oil from biosludge pyrolysis in an electrical thermal furnace.

Biosludge can be pyrolyzed to produce liquid oil as an alternative fuel. The content of five major elements, 22 trace elements and 16 PAHs was investigated in oven-dried raw material, pyrolysis residues and pyrolysis liquid products. Results indicated 39% carbon, 4.5% hydrogen, 4.2% nitrogen and 1.8% sulfur were in oven dried biosludge. Biosludge pyrolysis, carried out at temperatures from 400 to 800°C, corresponded to 34-14% weight in pyrolytic residues, 32-50% weight in liquid products and 31-40% weight in the gas phase. The carbon, hydrogen and nitrogen decreased and the sulfur content increased with an increase in the pyrolysis temperature at 400-800°C. NaP (2 rings) and AcPy (3 rings) were the major PAHs, contributing 86% of PAHs in oven-dried biosludge. After pyrolysis, the PAH content increased with the increase of pyrolysis temperature, which also results in a change in the PAH species profile. In pyrolysis liquid oil, NaP, AcPy, Flu and PA were the major species, and the content of the 16 PAHs ranged from 1.6 to 19 µg/ml at pyrolysis temperatures ranging from 400 to 800°C. Ca, Mg, Al, Fe and Zn were the dominant trace elements in the raw material and the pyrolysis residues. In addition, low toxic metal (Cd, V, Co, and Pb) content was found in the liquid oil, and its heat value was 7,800-9,500 kcal/kg, which means it can be considered as an alternative fuel.

Volatile organic compound constituents from an integrated iron and steel facility.

This study measured the volatile organic compound (VOC) constituents of four processes in an integrated iron and steel industry; cokemaking, sintering, hot forming, and cold forming. Toluene, 1,2,4-trimethylbenzene, isopentane, m,p-xylene, 1-butene, ethylbenzene, and benzene were the predominant VOC species in these processes. However, some of the chlorinated compounds were high (hundreds ppbv), i.e., trichloroethylene in all four processes, carbon tetrachloride in the hot forming process, chlorobenzene in the cold forming process, and bromomethane in the sintering process. In the sintering process, the emission factors of toluene, benzene, xylene, isopentane, 1,2,4-trimethylbenzene, and ethylbenzene were over 9 g/tonne-product. In the vicinity of the manufacturing plant, toluene, isopentane, 1,2,4-trimethylbenzene, xylene and ethylbenzene were high. Toluene, 1,2,4-trimethylbenzene, xylene, 1-butene and isopentane were the major ozone formation species. Aromatic compounds were the predominant VOC groups, constituting 45-70% of the VOC concentration and contributing >70% to the high ozone formation potential in the stack exhaust and workplace air. The sequence of VOC concentration and ozone formation potential was as follows: cold forming>sintering>hot forming>cokemaking. For the workplace air, cokemaking was the highest producer, which was attributed to the fugitive emissions of the coke oven and working process release.

Adsorption characteristics of benzene on biosolid adsorbent and commercial activated carbons.

This study selected biosolids from a petrochemical waste-water treatment plant as the raw material. The sludge was immersed in 0.5-5 M of zinc chloride (ZnCl2) solutions and pyrolyzed at different temperatures and times. Results indicated that the 1-M ZnCl2-immersed biosolids pyrolyzed at 500 degrees C for 30 min could be reused and were optimal biosolid adsorbents for benzene adsorption. Pore volume distribution analysis indicated that the mesopore contributed more than the macropore and micropore in the biosolid adsorbent. The benzene adsorption capacity of the biosolid adsorbent was 65 and 55% of the G206 (granular-activated carbon) and BPL (coal-based activated carbon; Calgon, Carbon Corp.) activated carbons, respectively. Data from the adsorption and desorption cycles indicated that the benzene adsorption capacity of the biosolid adsorbent was insignificantly reduced compared with the first-run capacity of the adsorbent; therefore, the biosolid adsorbent could be reused as a commercial adsorbent, although its production cost is high.