CMA

51 The pre-treatment process involves three rounds of washing-dewatering to maximize the removal of soluble salts from the FA. After the washing process, the HMs dissolved in washing water are precipitated in the chemical depositing tank, and the clean salt solution on the surface goes through the mechanical vapor recompression (MVR) tower, in which the industrial salt is crystalized, and the condensate water is recirculated into the washing tank. The deposited HM sludge is pumped into the 3rd washing tank, and then join with washed FA in the 3rd mechanical drying process to obtain WFA. The WFA is further dried by hot air from the clinker cooler to form DWFA. The DWFA is stored in a silo until it is fed into the ue gas chamber at the inlet of the rotary kiln. The testing comprised one blank test (test 0) and two tests (tests 1 and 2) under co-processing conditions. Test 0 was conducted on the rst day with no DWFA co-processing to determine the baseline conditions. Test 1 was conducted on the second day when the water washing pre-treatment facility was in operation, and DWFA was fed into the ue gas chamber at the kiln inlet at a rate of 3.1 t/h. Test 2 was conducted at a lower DWFA feeding rate of 1.7 t/h. Operating parameters for the pre-treatment and cement kiln line are provided in Table 10. To measure the transfer of HMs and PCDD/Fs in the pre-treatment process, samples of the FA, WFA, HM sludge in the inlet and outlet of the HM homogenizing tank (HM-in, HM-out), clean water (water), crystallized salt (salt), and drying ue (DF) were analysed for HMs and PCDD/Fs. For all tests, samples of the raw meal (RM), coal, cement clinker (CK), cement kiln dust (CKD), and ue gas from the Figure 3. Sampling points in Pre-treatment process and cement kiln system (Yan et al, 2018) FA Silo of MSWI fly ash Chemical reaction Tank Homogenizing Tank Stack at kiln back end HM-Out HM-In Chemical depositing Tank Filtering Tank MVR evaporating and crystallizing tower Industrial salt Salt DWFA DF Bag filter after Dryer WFA Dryer Water Stack after Dryer To flue gas chamber at back end of cement kiln Stack at kiln head Coal silo Humidifier tower RM CKD Bag filter at kiln back end Raw mill Material flow (B) Cement kiln system Flue gas flow Sampling point for gas sample Sampling point for soild sample Clinker cooler Bag filter at kiln head CK Coal Water washing Tank No.1 Horizontal decanter centrifuge No.1 Horizontal decanter centrifuge No.3 Water washing Tank No.2 Water washing Tank No.3 (A) Pretreatment system Fly ash flow Water flow Sampling point for soild sample Sampling point for gas sample Sampling point for water sample Flue gas flow Horizontal decanter centrifuge No.2 Flue Clean water tank Silo of Pretreated MSWI fly ash (DWFA) Feeding point of pretreated MSWI fly ash (DWFA)