DETERMINACIÓN DE LA DENSIDAD Y FLAMABILIDAD DEL MATERIAL COMPUESTO FORMULADO

The ash disposal system at Loy Yang is via hydraulic pumping as a slurry to the ash pond where the slurry is deposited sub-aqueously (refer to Figure 2.1, page 13). It was highlighted in the literature review that earlier SECV research had shown that such pumping leaches a significant proportion of soluble salts from the ash (Bone and Schaap, 1980). Their work was conducted at the Hazelwood power station. No comparable study has yet been undertaken at Loy Yang. In order to ascertain the effect of slurry pumping on ash leaching at Loy Yang, a sampling and analysis program was undertaken in late February and early March 1996.

A total of five series of samples were obtained, four samples from Loy Yang Power (LYA) and one sample from Edison Mission Energy (LYB). Each sampling run included a sample of ash and slurry water from within the power station complex (ie - relatively fresh ash and before the leaching effect of pumping, labelled the “Inlet”) and a sample of ash and slurry water from the discharge pipes at the ash pond, labelled the “Outlet”. The ash was separated by on site filtering through a 75 µm filter. The slurry water samples were analysed for major elements and a suite of trace elements. The ash samples were only tested for SO4 and Cl concentrations, as these comprise most of the leachable ash mass. All results are presented in Tables 4.11 to 4.13.

Samples of unleached (dry) precipitator ash and coal quality were obtained during this work. There is no access to sample dry fly ash from the electrostatic precipitators before mixing with water at Loy Yang A, although the slightly newer precipitator design at Loy Yang B allowed access to dry ash before mixing with water through a maintenance port. One sample of unleached precipitator ash was obtained from an electrostatic precipitator unit at Loy Yang A undergoing cleaning and maintenance during this period. Two samples of Loy Yang B dry precipitator ash were obtained. The quality of the coal supplied to each utility is essentially the same, since it is supplied by the coal preparation plant adjacent to the Loy Yang open cut. Any differences in ash morphology relate to the minor design differences between each utility. The coal quality data was supplied courtesy of Loy Yang Power. All results are in Tables 4.14 to 4.16.

Table 4.11 - Slurry Water Chemistry (Early 1996) : Major Elements (mg/L) 29-02-96 05-03-96 07-03-961 12-03-96 15-03-96 I O I O I O I O I O pH 9.2 9.2 11.0 11.1 10.8 10.6 11.6 9.6 10.2 10.1 Eh2 - - 280 300 300 300 320 330 310 300 TDS 7,800 7,500 5,900 4,600 12,000 10,000 7,300 7,300 8,400 7,800 EC2 1,145 1,125 822 701 1,790 1,430 1,295 961 1,138 1,056 Na 1,900 1,800 1,600 1,100 2,900 2,700 1,800 1,800 2,200 2,000 K 89 89 77 59 140 120 82 85 0.3 93 Ca 370 370 240 560 480 460 440 440 460 410 Mg 73 66 0.13 110 110 120 150 160 5.3 6.2 SO4 4,500 4,300 3,200 2,400 6,500 5,600 4,000 4,000 4,850 4,500 Cl 745 720 500 370 1,000 750 635 630 595 560 CO3 70 57 110 130 190 200 68 58 150 140 HCO3 45 60 - - 48 120 64 60 65 52

I - initial ash slurry within power station; O - output ash slurry at the ash pond.

1 _{- Loy Yang B sample;} 2 _{- Eh (redox) in mV and EC in mS/m.}

Table 4.12 - Slurry Water Chemistry (Early 1996) : Trace Elements (µg/L) 29-02-96 05-03-96 07-03-961 12-03-96 15-03-96 I O I O I O I O I O As - - 3 <1 1 <1 8 9 16 18 Ba 60 50 70 110 110 70 60 50 90 70 B 4,100 4,000 2,400 3,600 5,400 4,500 3,500 3,400 3,700 3,300 Cd <5 <5 <2 <2 <2 <2 <10 <10 <10 <10 Cr <30 <30 <30 <30 <30 <30 <30 <30 <30 <30 Co <30 <30 <30 <30 <30 <30 <30 <30 <30 <30 Cu 60 60 <30 50 110 30 150 170 <30 <30 Pb 30 <30 40 90 90 100 130 120 <30 <30 Hg <0.5 <0.5 <0.5 <0.5 <0.5 2 2.3 2.8 0.6 2 Mo <50 <50 90 70 90 70 90 90 80 70 Ni 40 40 <30 <30 <30 <30 <30 <30 <30 <30 Sn <50 <50 <50 <50 <50 <50 <50 <50 <50 <50 Se 240 240 225 36 65 61 420 420 390 340 Zn 50 40 <30 50 60 30 170 500 <30 60

Table 4.13 - Leachable Mass (Early 1996) : Sulfate and Chloride (mg/kg) (dry basis)

Sulfate Chloride

Date Inlet Outlet %Diff.1 Inlet Outlet %Diff. 29-02-96 12,000 7,300 -39.2 2,000 960 -52

05-03-96 5,500 10,000 81.8 540 620 14.8

07-03-96 22,000 23,000 4.5 2,200 1,400 -36.4 12-03-96 18,000 6,300 -65 1,100 510 -53.6

15-03-96 9,000 8,100 -10 840 960 14.3

1 _{- Calculated from the percentage increase (+) / decrease (-).}

Table 4.14 - Precipitator Ash Quality at Loy Yang (Early 1996) : Major Elements Exp.1 Black Loy Yang A Loy Yang B

(%) Furnace (1988) 20-03-962 7-03-96 7-05-963 SiO2 2.5 41.6 55.9 6.6 6.56 SO3 1.9 5.6 5.39 19.3 25.6 CaO 2.3 3.5 3.45 10.3 14.82 MgO 7 7.9 4.84 10.2 15.17 Na2O 3.3 7.8 6.7 12.7 13.45 K2O 0.17 0.43 0.23 0.69 0.32 Al2O3 22.8 17.6 6.92 11.6 3.24 Fe2O3 14.9 7.5 7.81 5.3 7.13 Cl <0.1 1.4 0.33 0.31 2.09 TiO2 <0.1 0.76 1.3 0.2 MnO 0.04 0.16 0.05 CO3 5.2 0.88 P2O5 0.03 0.05 0.01 LOI 9.2 5.66 21.1 11.77 Sum 102.53 98.06 104.81 101.29

1 _{- Loy Yang Experimental Furnace samples from Bone & Schaap (1980);} 2 _{- Sample}

provided by Loy Yang Power during cleaning and maintenance of a precipitator at Loy

Yang A; 3 - Further bulk sample provided by Edison Mission Energy.

Table 4.15 - Coal Quality at Loy Yang (Early 1996) (%)

Date Location Moisture1 Ash2 Na2 Al2 Ca2 SiO21 29-02 AM Stage 2, LYA 65.0 1.7 0.05 0.01 0.02 1.01 5-03 AM Stage 1, LYA 61.0 1.7 0.13 0.00 0.00 0.75

7-03 AM Stage 14, LYB 61.5 1.5 0.17 - - -

12-03 AM Stage 2, LYA 62.8 1.0 0.21 0.08 0.08 0.00 15-03 AM Stage 2, LYA 64.1 1.7 0.08 0.01 0.03 0.00

Table 4.16 - Precipitator Ash Quality at Loy Yang (Early 1996) : Trace Elements mg/kg As Ba B Cd Cr Co Cu Pb Hg Mo Ni Se Sn Zn

LYA1 4.1 120.8 49.3 <0.5 13.5 8.8 13 2.5 0.23 <5 11.8 <5 <5 23 LYB2 7.9 33 630 <0.5 8.0 4.0 28.5 5.0 1.45 <5 10 18.5 <5 86.5 19803 71 1,800 190 3.9 310 74 140 220 3.2 69 130 26 - 140

1 _{- Loy Yang A, Sampled 20-3-96;} 2 _{- Loy Yang A, Sampled 7-5-96;} 3 _{- Data from Loy Yang}

Experimental Furnace (Bone & Schaap, 1980).

The coal quality data is generally uniform, showing the effects of blending at the coal preparation plant adjacent to the open cut, undertaken to minimise fouling of the boilers and thereby optimise station performance (Waring et al., 1996). The influence of Ca on the alkaline strength of the ash slurry water quality can be seen by comparing the data in Tables 4.11, 4.14 and 4.15. The high calcium oxide (lime) content of the ash, particularly at Loy Yang B, allows the pH to reach up to 11. Importantly, the proportion of soluble species in the dry precipitator ash samples appears to be higher than the ash samples obtained by filtering slurry water. The concentration of trace elements within the precipitator ash samples is generally low, especially compared to the early studies in 1980 at the Loy Yang Experimental Furnace. The coal quality and precipitator ash data demonstrate the need to consider ash and slurry water quality as a function of the coal quality over time.

The concentrations of SO4 and Cl in the slurry water and the slurry ash appear to correlate some degree, as shown in Figure 4.1. This would be expected as the SO4 and Cl are generally present in relatively soluble mineral forms in the ash and would dissolve into solution quite rapidly. There is wide variability in the measured concentrations of SO4 and Cl within the filtered ash. This may be due to the expected variability of the ash or the residence time of the slurry within the hydraulic transport system. The average residence time within the hydraulic slurry system is approximately 15 to 30 minutes on average, although it can reach up to an hour or more if the internal pumps in the power station are temporarily turned off (Pentland, 1995). This time corresponded to the time taken to move from sampling the inlet within the power station to the discharge outlet at the ash pond.

Figure 4.1 - Correlation of Sulfate and Chloride in Ash and Slurry Water

There is an average decrease in SO4 concentration in the filtered ash from the inlet to the outlet of approximately 5.6%, although excluding the value of 81.8% as a statistical outlier the average becomes much greater at 27.4%. The average decrease in Cl concentration from the inlet to the outlet was 22.6%. The data on ash and slurry water quality demonstrates that there is leaching occurring within the hydraulic transport system at Loy Yang, although a degree of caution is necessary in extrapolation based on the limited data set obtained.

This initial leaching appears to help the leaching of the ash once it has been deposited into the disposal pond. The previous section, 4.2, demonstrated that ash excavated from the ash pond delta after 6 to 12 months deposition had a soluble mass about one order of magnitude lower than precipitator ash, consistent with the analytical data obtained on precipitator ash in Table 4.14. The decrease in SO4 and Cl concentration in the ash between the inlet inside the Loy Yang power station and the outlet (discharge) at the ash pond ranges from about 6% to 27%. Given the fact that a significant proportion of the soluble mass in the ash is due to soluble SO4 and Cl salts, this decrease caused by the hydraulic slurry system is therefore significant.