熱分解가스化 鎔融施設의 有害物質 排出特性에 關한 硏究

Abstract

The incineration process has commonly used for wastes amount reduction and thermal treatments of pollutants as the technologies accumulated. However, the process is getting negative public images owing to matter of hazardous pollutants emission. Specially dioxins became a main issue and is mostly emitted from municipal solid wastes incineration. In this reason, pyrolysis gasification melting furnace is presented as a alternative of incineration process. In this study, I selected three types(S,T,P) of pyrolysis-gasification-melting facilities with pilot scale, investigated emission behaviors of dioxin and hazardous materials having similar toxicity of dioxin, investigated an environmental review for melting slags from by-product of the facilities, and could obtain the following results.

1. In the case of S-type(stoker type pyrolysis-gasification-melting), domestic wastes with 39.81% of moisture content, 47.15% of combustible content , and 3.03% of ash content are used, and dioxin concentration at outlet of waste heat boiler(184℃) under low temperature zone is higher than that at outlet(878℃) of pyrolysis-gasification furnace or at outlet(650℃) of melting furnace of under high temperature zone. However, it was examined that dioxin concentration at the stack is 0.155 ng TEQ/Sm3 and lies below the emission standard(10 ng TEQ/Sm3) of dioxin concentration for small size incinerator. Also, average removal efficiency of dioxin is 93.23% in semi-dry-reactor/bag-filter(SDR) as a prevention facility. It is found that concentration of co-planar-PCB at outlet of pyrolysis-gasification chamber of S-type facility is 0.126 ng-WHO TEQ/Sm3 and ratios of gas-phase and particle-phase are 12.8% and 87.2%, respectively. It occurs that concentration of total co-planar-PCB at outlet of waste heat boiler is 0.101 ng-WHO TEQ/Sm3 and this concentration at outlet of waste heat boiler is about 20% less than that at outlet of pyrolysis-gasification chamber.

2. In the case of T-type(compression-pusher type pyrolysis-gasification-melting), domestic wastes with 52.82% of moisture content, 41.21% of combustible content, and 5.97% of ash content are used, and dioxin concentration at outlet(39℃) of water-jet-type cooling system under low temperature zone is higher than that at outlet(1,026℃) of gasification-melting burner under high temperature zone. Also, it is found that removal efficiency of gasification treatment facility as dioxin prevention facility are 0.217 ng-TEQ/Sm3 of dioxin at back-end of gasification-melting chamber and 0.046 ng-TEQ/Sm3 of dioxin at outlet of water-jet-type cooling facility. It occurs that dioxin concentration in gasification treatment facility is about 4.7 times less than that at outlet of gasification-melting chamber and this type facility satisfies the emission standard(10 ng TEQ/Sm3) of dioxin concentration for small size incinerator. It is found that concentrations of co-planar-PCB are 0.070 ng-WHO TEQ/Sm3 at outlet of gasification-melting chamber and 0.009 ng-WHO TEQ/Sm3 at the final outlet and removal efficiency of co-planar-PCB in gasification treatment facility is about 87%.

3. In the case of P-type(plasma pyrolysis-gasification-melting), contents of target wastes containing much vinyl are 8.83% of moisture, 83.62% of combustible, and 7.55% of ash, respectively. It occurs that dioxin concentration at outlet(250℃) of semi-dry-reactor/bag-filter(SDR) under low temperature condition is higher than that at outlet(893℃) of pyrolysis-gasification furnace. It occurs that dioxin concentrations of each process are 3.107 ng-TEQ/Sm3 at outlet of pyrolysis-gasification burner and 0.439 ng-TEQ/Sm3 at the final outlet and that average removal efficiency of dioxin in semi-dry-reactor/bag-filter is about 85.87%. However, it is found that the concentration at the final outlet satisfies the emission standard(10 ng TEQ/Sm3) of dioxin concentration for small size incinerator. It would be concluded that combination of bag-filters having excellent removal efficiency for micro-size particles might have advantage as dioxin prevention facility because ratio of particulate-phase dioxin is higher than that of gas-phase in flue gas of all of three type facilities.

4. While passing heat exchanger, waste heat cooling system, and semi-dry-reactor/bag-filter in P-type facility, concentration of particulate-phase chlorobenzenes decreases and that of gas-phase chlorobenzenes increases. Also, among six kinds of chlorobenzene isomers, concentrations of mono-chlorobenzene and hexa-chlorobenzene decrease, and concentrations of di-chlorobenzene, tri-chlorobenzene, tetra-chlorobenzene, and penta-chlorobenzene increase. While passing heat exchanger, cooling system,and semi-dry-reactor/bag-filter, concentration of particle-phase chlorophenols decreases and that of gas-phase chlorophenols increases. Also, among five kinds of chlorophenol isomers, concentrations of mono-chlorophenol and tetra-chlorophenol decrease, and concentrations of di-chlorophenol, tri-chlorophenol, penta-chlorophenol increase.

5. Observation result of scanning electron microscope about surface of melting slag from three pyrolysis-gasification-melting processes represents that melting slag cooling with water has smooth surface, on the other hand melting slag cooling with air has rough surface and small-sized bubbles. It is concluded that crystalline structure of slag is influenced by composition of domestic waste melted, melting condition, cooling condition of slag, and so on. In melting slag of three facilities, amount of dioxin existence is 2.92 pg-TEQ/g of S-type, 0.87 pg-TEQ/g of T-type, and 0.21 pg-TEQ/g of P-type, and lies below the Japanese emission standard(3 ng TEQ/Sm3) of dioxin concentration for burning materials. Also, it is investigated that almost no heavy metal flows out from slag of three facilities(S,T,P) and slag becomes stable passing through pyrolysis-gasification-melting processes.

6. Through a case study on domestic and foreign researches and a result of this study on pyrolysis-gasification-melting processes and emission behavior of hazardous materials, exhibition operation and political support for research and development would be required because of advantages of pyrolysis-gasification-melting technology that reduces toxic hazardous materials of dioxin, chlorobenzene, chlorophenol etc. as against existing incinerating facility and makes very stable and harmless melting slag