Remediation of mining legacy sites: Chinese Practices

Transcription

1 Remediation of mining legacy sites: Chinese Practices Qingshan Zhu Institute of Process Engineering Chinese Academy of Sciences 1

2 Outlines 1. Introduction 2. Use of mining legacy sites 3. Utilization of gangue and tailings 2 2

3 Outlines 1. Introduction 2. Use of mining legacy sites 3. Utilization of gangue and tailings 3 3

4 Background (1) Chinese minerals: low grade Coal: 50% are low-rank coal 1t coal discharges t coal gangue 4

5 (1) Chinese minerals: low grade Iron ore Background 70 billion tons, 95% low grade iron ore Average Fe 33%, 11% lower than world average 4036 mines, large mine 28, medium mine 61, 97.8% are small scale mines Need beneficiation before use 1t iron ore concentrate: 2t waste rock+2t tailings 5

6 Background (2) Large population, huge mineral consumption Unit: billion ton Consumption Domestic production waste/tailings Iron ore Coal Total iron ore gangue/tailings: >10 billion tons, over 4000 iron ore waste rock piles or tailings dams Total coal gangue:>5 billion tons, over 1600 coal gangue piles Occupied 4 million hectares land increased 40,000 hectares per year 6

7 Background (3) Small agricultural land per capital Land area: 9.6 million km 2 ; 0.78 hectare per capital, 1/3 of world average Agricultural land: 0.11 hectare per capital, 43% of world average 7

8 History of mined land reclamation (1) First stage ( s) Almost no land reclamation (2) Second stage ( ) Land reclamation provision (1988) : government promotes land reclamation; State investment on research and demonstration (3) Third stage (1998-present) Land management act (1998): all damaged land must be remediated Regulations on land reclamation monitoring (2007): report on land damage and reclamation plan Regulations on land reclamation (2011): detailed requirements on the implementation 8

9 National strategy on land reclamation All the damaged land must be remediated (1) New mines Licence can be obtained before the land reclamation plan was approved by government Land reclamation fund must first be established before issuing the licence (2) Mines in use Land reclamation plan and fund need to be established before renewing the licence (3) Closed mines Government initiates to make land reclamation plan and establish the reclamation fund 9

10 Land reclamation in China (1) Overall mines 9000 large mines, 260,000 medium and small mines Over 7 billion tons of mining gangue Over 10 billion tons of tailings, stored on over 3000 tailings ponds (2) Overall land reclamation Land damage due to mining: 4 million hectares Land reclamation of mining legacy sites: 860,000 hectares, ~20% damaged land was remediated 100,000 hectares land reclamation every year 10

11 Land reclamation in China Change of agricultural land Agricultural land (million hectare) Year 2016 Decrease: 336 khm 2 due to construction, industrial and mining Increase: 293 khm 2 due to reclamation Decrease rate: from 500 khm 2 to 40 khm 2 per year 11

12 Outlines 1. Introduction 2. Use of mining legacy sites 3. Utilization of gangue and tailings 12 12

13 I. Mine park (1) Huangshi national mine park Daye iron ore: high grade 54-60% Start at 254 AC in Han dynasty; Restart in 1890 for iron ore for Hanyang Iron factory, provide 3000 t/m iron ore for the first modern iron company Up to 1938, produce 6.1 million tons of iron ore : 9.2 million tons of iron ore shipped to Japan 1960: 2.90 million t/a of iron ore 1971: 5.05 million t/a ofiron ore : million tons iron ore in total Daye iron ore mine 1930s Hanyang iron factory 1930s 13

14 444m I. Mine park (1) Huangshi national mine park Revegetation area: m 2 Total area: 30.2 km 2 Open at April 22, 2007 Closed in

15 (2) Maoming mine park Start in 1958, closed in 1992 Produce oil shale oil 100 million tons, which produce shale oil 2.92 million tons I. Mine park Mine area 6.8 km 2, depth 70 meters, ecological environment deterioration Ecological remediation started in

16 (2) Maoming mine park I. Mine park Plant 13,000 trees, over 100 hectares, new road 25.2 km; Capacity of reservoir 1600 million m 3, irrigating farmland 600 hectares 16

17 I. Mine park 61 national mine parks were established since April

18 II. Revegetation of mining site (1) Soil reconstruction Vegetation Topsoil leveling refilling Isolation layer Gangue 18

19 II. Revegetation of mining site (2) Plant selection Festuca arundinacea Clover Vetiver grass Lucerne Bermuda grass Erect milkvetch 19

20 II. Revegetation of mining site (3) Slop stabilization 20

21 II. Revegetation of mining site Example 1: iron ore mine (Anshan steel) Established in 1948, produce crude steel million tons in 2015 Has 6 iron ore mines, produce 65 million tons raw ore, get 18 million tons iron ore concentrate Formed 8 tailings dams (4 still in use) of 1669 hectares, and 8 waste rock fields of 2094 hectares 21

22 II. Revegetation of mining site Example 1: iron ore mine (Anshan steel) Reclamation and revegetation start in

23 II. Revegetation of mining site Example 1: iron ore mine (Anshan steel) Pant 6 million trees, 5.8 million bushes 23

24 II. Revegetation of mining site Example 1: iron ore mine (Anshan steel) Reclamation area: 3000 hectares, reclamation rate 90%; revegetation rate 95% 24

25 II. Revegetation of mining site Example 1: iron ore mine (Anshan steel) Established 3 reclamation demonstration park 25

26 II. Revegetation of mining site Example 1: iron ore mine (Anshan steel) Established 3 reclamation demonstration park 26

27 II. Revegetation of mining site Example 2: coal gangue hill (Luan coal Ltd.) 13 coal gangue hills (8 still in use), occupied land 67 hectares 5 coal gangue hills of 33.7 hectares revegetated Over 200 coal gangue hills of ~1500 hectares were revegetated all over China 27

28 III. Photovoltaic power generation (1)Xiaoyi subsided coal mine PV project Capacity 100 MW: Sept start to construction, capacity 30 MW, finished August 2015; second phase 70 MW finished Nov Subsided area: 200 hectares Investment 1 billion RMB, electricity output 140 million kwh 28

29 III. Photovoltaic power generation (2)Linxiang copper ore tailings pond PV project Capacity 20 MW: start in July 2015, connected to the grid in June 28, 2016 Covered area: 120 hectares Investment 180 million RMB, electricity output 19.5 million kwh 29

30 III. Photovoltaic power generation (3)Huainan coal mine subsided lake PV project Capacity 40 MW, PV module in total, connected to the grid in June 16, 2017 Subsided lake area: 400 hectares, PV module covered area: 87 hectares Investment 320 million RMB, electricity output 33 million kwh 30

31 III. Photovoltaic power generation (4)Others Other 10 mine PV projects finished with capacity of 220 MW Around 20 mine PV projects planned with capacity over 500 MW 31

32 Outlines 1. Introduction 2. Use of mining legacy sites 3. Utilization of gangue and tailings 32 32

33 I. Coal gangue utilization 1600 coal gangue hills, total amount 5 billion tons increased by million tons per year Land occupation: 13,700 hectares Utilization ratio increased year by year, currently utilization ratio ~70% 33

34 I. Coal gangue utilization Utilization technologies (1) Thermal utilization (power generation, combustion) carbon content >20%, calorific value >6200 kj/kg (2) Construction materials (bricks) calorific value kj/kg (3) Filling materials (mine, roads) calorific value <2100 kj/kg Construction materials (4) Pigments Special composition Filling materials Thermal utilization

35 I. Coal gangue utilization (1) Coal gangue power generation plants Huanglin mine Guolin power plant Over 250 coal gangue power plant with total capacity 35 GW, the largest capacity 330 MW Consume 150 million tons of coal gangue in 2013, 32% of the total coal gangue discharged in

36 I. Coal gangue utilization (2) Make construction materials Over 1000 coal gangue brick plants, produce 13 billion bricks Consume 56 million tons of coal gangue in 2013, 12% of the total coal gangue discharged in

37 (3) Filling materials I. Coal gangue utilization 260 million tons of coal gangue were used to filling and remediating mines and in 2013, 56% of the total coal gangue discharged in

38 I. Coal gangue utilization (4) White pigment from kaolinite coal gangue Roasting Mixing additives Hydrothermal product Established 30,000t/a kolin white pigment in 2013 Whiteness 95,particle size: m 38

39 II. Iron ore tailings utilization Over 2000 iron ore tailings dams, total amount 10 billion tons increased by million tons per year Iron content (TFe) 10-18% Low value utilization, most of them are not used New technology to recovery iron ore concentrate 39

40 II. Iron ore tailings utilization New utilization process Iron ore tailings Primary iron ore concentrate TFe: 10-18% high gradient magnetic separator TFe: 30-35% Magnetizing roasting Fe 2 O 3 +H 2 Fe 3 O 4 +H 2 O 40

41 II. Iron ore tailings utilization New utilization process Secondary tailings TFe 3.5% Primary iron ore concentrate after roasting Magnetic separation Recovery concentrate TFe 66.5% Bright phase: Fe 3 O 4 ; dark phase: silicates 41

42 II. Iron ore tailings utilization New utilization process Iron ore tailings Primary Iron ore concentrate TFe: 10-18% high gradient magnetic separator TFe: 30-35% TFe: 60-66% magnetic separator 42

43 II. Iron ore tailings utilization 100kt/a technology demonstration plant Fe 2 O 3 +H 2 Fe 3 O 4 +H 2 O Shaft FB (1966) FB (2009) FB (2013) capacity(10kt/a) T( C) Time(h) Fe recovery(%) Energy comsumption (kgce) Yunnan Province, China 43

44 II. Iron ore tailings utilization 6 million (4*1.5 million) t/a plant (Anshan Steel) 矿石 15.2 t/h 水 0.76t/h Nm3/h Fe2O3.1.5H2O 8.9t/h 脉石 6.3 t/h 水 0.76t/h 7 454K Nm3/h Nm3/h K 20 Fe2O3.H2O 8.5 t/h SiO2 6.3 t/h 923K Nm3/h Nm3/h, 823K 9 Fe2O3 7.6 t/h 脉石 6.63 t/h 矿石 1 2 空气 Nm3/h 矿石 15.2 t/h 水 0.76t/h K Nm3/h, 823K H2O 6 t/h 矿浆 K 23 24t H2O Fe3O4 7.4 t/h 脉石 6.3 t/h K Nm3/h Fe2O3 7.6 t/h 脉石 6.3 t/h 高炉煤气 Nm3/h 28.5 m tons of tailings processed to produce 6.2 m tons primary iron ore concentrate, after magnetizing roasting-magnetic separation, 2.5 m tons of iron ore concentrate with TFe 66.5% 44

45 45 Thank you for your attention!

46 II. Revegetation of mining site (1) Soil reconstruction Acidic gangue an isolation layer 46

47 II. Revegetation of mining site Example 3: red mud tailings pond (Pingguo Alumina) Area: 45 hectares, 5 million tons of red mud 47

48 II. Revegetation of mining site Example 3: red mud tailings pond (Pingguo Alumina) Revegetation area: 70 hectares 48

49 II. Revegetation of mining site Example 3: red mud tailings pond (Pingguo Alumina) Revegetation area: 70 hectares 49

50 III. Photovoltaic power generation (4)Chengde iron ore tailings pond PV project Capacity 20 MW: closed in 2014, start to install PV module in June 2016, PV module in total, connected to the grid in June 29, 2017 Land area: hectares 50