Chemical-looping combustion (CLC), which is a promising technique that includes an inherent separation of CO 2 may reduce the generation of dioxins in municipal solid waste (MSW) disposal because in a CLC system, no free oxygen is available for incineration process. Polyvinylchloride (PVC) and kitchen garbage are the main chlorine substances in MSW. The reaction between PVC pyrolysis gas and a calcium (Ca)based oxygen carrier was investigated in a two-stage reactor in this study. The thermal decomposition and reduction/oxidation cycle behaviors of the oxygen carrier were investigated by analyzing methane (CH 4 ) using a thermogravimetric analyzer (TGA). The characteristics of CaSO 4 /Fe 2 O 3 oxygen carrier were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the addition of Fe 2 O 3 into CaSO 4 can enhance the reaction rate, and also that the CaSO 4 /Fe 2 O 3 oxygen carrier showed a good heat stability at the temperature of 900 C. The reduction/oxidation cycles confirmed that the decomposition of the CaSO 4 /Fe 2 O 3 oxygen carrier is usually accompanied by some side reactions. These side reactions could cause the loss of their regeneration ability. The CaSO 4 /Fe 2 O 3 oxygen carrier successfully reacted with PVC pyrolysis gas in a two-stage reactor and the complete reaction ratio of m PVC to m oxygen carrier is 8. The research documented herein provides a useful reference for the utilization of MSWs.

CaSO4 oxygen carriers with silica sol were prepared and their reaction performances with CH4, CO and H2 were experimentally investigated. The formation characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in PVC combustion by means of chemical looping combustion (CLC) based on CaSO4 oxygen carrier and air were studied in a tube furnace system. The results show that CaSO4 oxygen carriers with silica sol can be completely reduced by CH4, CO and H2. The reaction time of CH4 and H2 is much shorter than CO. The chemical looping combustion of PVC can effectively inhibit the formation of PCDD/Fs.The yield and International Toxicity Equivalent Quantity (I-TEQ) of PCDD/Fs produced in CLC are 2270.9 pg/g and 290.2 pg(I-TEQ)/g, much lower than those in air combustion which are 34172.5 pg/g and 732.8 pg(I-TEQ)/g. It is mainly because fuel doesn't directly contact with O2 in CLC, the oxidative cleavage of large carbon molecule and the conversion from HCl to Cl2 are significantly reduced which will inhibit the low temperature de novo synthesis and precursors reaction of PCDD/Fs. The disposal of combustible solid waste (CSW) is one of the severely environmental problems in the world [1] . Composting, landfill and incineration are the common treatment methods of MSW. Incineration is the main developing direction in combustible solid waste management because of its small occupation area, stable and reliable operation and good reduction [2] . But incineration of CSW is easy to produce PCDD/Fs and other toxic substances, which is harmful to human health. So its development is controversially [3] . Hutzinger et al [4] found that de novo synthesis and precursor reaction are the main generating ways of PCDD/Fs in CSW incineration. O 2 plays an important role in the two reactions [5] . Therefore, avoiding the direct contact of O 2 and fuel is one of the feasible approaches to inhibit PCDD/Fs generation in combustion.Chemical looping combustion (CLC) is a new combustion technology. The oxygen is transferred from air to fuel by means of the circulation of oxygen carriers between air reactor and fuel reactor, which realize the non-contact combustion of fuel and air [6] . The formation of PCDD/Fs may be greatly inhibited by use of CLC to dispose CSW, because there is no direct contact between free oxygen and CSW.Oxygen carriers are the key element in CLC. The metal oxides such as Ni, Cu, and Fe are mainly studied at present [7] . However, metal oxides have strong catalysis on the formation of PCDD/Fs [8] , which may aggravate its generation. By contrast, CaSO 4 oxygen carrier is more suitable to dispose high chlorine CSW because of its high oxygen transport capacity, low cost, environmental friendliness and small catalysis on the formation of PCDD/Fs [9] .Based on this, CaSO 4 oxygen carrier with silica sol is prepared and its reaction characteristics with different fuel gas were experimentally investigated. Finally, the influence of CLC and air combustion on the formation of PCDD/Fs is investigated b...