Resource consumption in cement production - Simplified. Formation, release and control of dioxins in cement kilns co-processing wastes

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1 Formation, release and control of dioxins in cement kilns co-processing wastes Production of cement Raw material Raw meal blending basin quarry ESP kiln Dr. Kåre Helge Karstensen Foundation for Scientific and Industrial Research, Norway Asian Institute of Technology, Thailand inker Rohmühle Cement storage bin Cement mill storage bin dispatch Regional Capacity Building Workshop on the Practical Use of the Guidelines on BAT and BEP and Environmentally Sound Management of POPs Wastes and PCBs. Beijing, China, November 2009 gas solid Temperatures and residence time for materials and gases in the cement production process Resource consumption in cement production - Simplified Temperatures and retention time «De-Novo-Synthesis» in a preheater cement kiln Range [ C] 25 [sec] 350 [ C] 30 [ C] 550 [ C] 720 [ C] 2000 [ C] 800 [ C] 1200 [ C] 850 [ C] inker Cooler Cyclone Rotary Kiln Preheater 1450 [ C] 0 [sec] 8 [sec] 900 [ C] Material Flow Gas Flow 1

2 Cement kilns have been used for co-processing of organic hazardous wastes in Norway for 25 years and is the only treatment option Sino-Norwegian project Environmentally sound management of industrial and hazardous wastes in cement kilns in China MEP SINTEF China generate >1 billion ton industrial waste, 150 million ton municipal solid waste, 30 million ton of sludge and 30 million ton of hazardous waste/y. Waste treatment is insufficient and ineffective China produced >50% of the world cement, 1.4 billion tons in

3 ...in approximately 5000 cement kilns which consumes ~ 150 million tonnes of coal and ~1500 million MWh of electricity.....and consume ~2.4 billion tonnes of virgin raw materials.....which emits approx. 1.4 billion tonne of carbon dioxide, millions of tons of dust and about 5 % of all SO 2 emissions... Guangzhou Zhujiang/Heidelberg Cement Plant, Guangdong Province, 2007 Shang Hai Jin Shan Cement Guangzhou Zhujiang/Heidelberg Cement Plant, Guangdong Province,

4 Hubei, China Air canon for feeding plastic bags with solid waste at Shang Hai Jin Shan Cement The Chinese Government ordered a complete disposal of approx. 300 tons of Obsolete Pesticides Source category Cement kilns firing hazardous waste are explicitly mentioned in the Stockholm Convention, Annex C part II, as industrial source having the potential for comparatively high formation and release of dioxins to the environment The main goal of the Sino-Norwegian project Is to strengthen the compliance with the Stockholm and the Basel Convention. 4

5 Training of local Environmental Protection Bureaus, Chengdu and Du Jiang Yan, November 2009 The Toolkit data is based on previous experiences on concentration levels from various source categories. The document is under continuous development and must be used with caution. Source categories 1. Waste Incineration 2. Ferrous and non-ferrous metal production 3. Power generation 4. Production of mineral products 5. Transport 6. Uncontrolled combustion 7. Production and use of chemicals (release to land) 8. Miscellaneous 9. Landfill 10. Hot spots Sub categories of the main category 1, Waste incineration Screening Matrix Summing up the release from all matrixes No. Main Source Categories Air Water Land Product Residue 1 Waste Incineration X X 2 Ferrous/Non-Ferrous Metal Production X X 3 Power Generation and Heating X X X 4 Production of Mineral Products X 5 Transport X 6 Uncontrolled Combustion Processes X X X X 7 Production and Use of Chemicals and Consumer Goods X X X 8 Miscellaneous X X X X 9 Disposal X X X X 10 Identification of Potential Hot-Spots Probably registration only to be followed by site-specific evaluation 5

6 The unit of the emission factor is g g TEQ per ton of feed material or product. ass 1 refers to low technology (with no APC system) ass 2 refers to newer technology/controlled combustion (with minimal APC system) ass 3 and 4 refers to latest technology (with sophisticated APC system) Emission factors for source category ,1 Waste Incineration g TEQ per ton of feed material or product Municipal solid waste incineration 1 Municipal solid waste incineration 2 Municipal solid waste incineration 3 Municipal solid waste incineration 4 Hazardous waste incineration 1 Hazardous waste incineration 2 Hazardous waste incineration 3 Hazardous waste incineration 4 Medical waste incineration 1 Medical waste incineration 2 Medical waste incineration 3 Medical waste incineration 4 Shredder waste incineration 1 Shredder waste incineration 2 Shredder waste incineration 3 Sewage sludge incineration 1 Sewage sludge incineration 2 Sewage sludge incineration 3 Waste wood incineration 1 Waste wood incineration 2 Waste wood incineration 3 Animal carcasses burning 1 Animal carcasses burning 2 Animal carcasses burning Emission factors for source category 4 Production of mineral products Cement kilns g TEQ per ton of feed material or product Release of dioxins in China All 62 subcategories within the 10 main categories of dioxin release sources listed in the Toolkit exist in China Shaft kilns Old w et kilns, ESP temperature >300 C Wet kilns, ESP/FF temperature 200 to 300 C Wet kilns, ESP/FF temperature <200 C and all types of dry kilns w ith preheater/precalciner, T<200 C According to some actual measurement and estimation, China had about 10 kilograms- TEQ dioxin release in 2004 and is one of the countries with the largest amount of dioxin releases. Estimated dioxin releases to air by industry sources in 2004 Estimated dioxin releases by residues by industries in

7 Estimated dioxin contribution by industries in 2004 (percentage) High temperature incinerator China s Incinerators Loom as a Global Hazard, August 12, 2009 The Chinese government is struggling to cope with the rapidly rising mountains of trash generated as the world s most populated country has raced from poverty to rampant consumerism. Beijing officials warned in June that all of the city s landfills would run out of space within five years. The governments of several cities with especially affluent, well-educated citizens, including Beijing and Shanghai, are setting pollution standards as strict as Europe s. Despite those standards, protests against planned incinerators broke out this spring in Beijing and Shanghai as well as Shenzhen. Modern cement kiln CO 2 reduction potential in the Chinese cement industry With a cement production of 1,4 billion t/y and a thermal substitution rate of 40% with wastes, China could reduce the CO 2 emissions with 100 million tonnes per year or more, compared with incinerating or landfilling the wastes. Substitution of clinker by mineral additions may be even more effective as both thermal CO 2 from fossil fuels and CO 2 from the decarbonation of raw materials is reduced. 7

8 D/F emission Policy elements vs. Cement Kilns Cement kilns shall primarily be used for recovering alternative fuels and raw materials which can substitute fossil fuel and virgin raw materials; In lack of available treatment options, a feasible cement kiln can be used for treatment of organic hazardous constituents provided that this is done under strict Government control and guidance. /bat_bep/2nd_session/egb2_followup/ Approximately 2200 PCDD/F measurements, many PCB and some HCB measurements were compiled from cement companies around the world. The data represents emission levels from both wet and dry kilns, performed under normal and worst case operating conditions, with and without the co-processing of a wide range alternative fuel and raw materials. 230 Measurements in 110 kilns and 11 European countries 106 PCDD/F emission measurements from 37 German Cement Kilns in 2001 Australia Results of repeated measurements over a decade show that levels of dioxin emissions from Australian cement plants are consistently below 0.1 ng I-TEQ/mI 3. Australia No significant difference in dioxin emissions due to use of waste derived fuels was observed within plants (Environment Australia, 2002). 8

9 160 German Cement Kiln measurements Emissions in ng I-TEQ/m 3 0,14 0,12 0,10 0,08 0,06 0,04 0,02 (0,29) 0, Measurement No. regular fuel with secondary fuel with secondary raw material Concentration in ng ITEQ/m 3 PCDD/F emission Germany PCDD/F 1999: substitution level 23% 2002: substitution level 35% Measurement Heidelberg kilns using more than 40% alternative fuel compared with kilns using fossil fuel only UNEP dioxin inventory in Thailand In 1997 the Pollution Control Department (PCD) of the Government of Thailand initiated a dioxin program together with UNEP Among the 7 industrial sectors investigated, cement kilns had the lowest PCDD/F emissions... results clearly revealed that the addition of tyres and/or liquid hazardous waste had no effect on the emission results The means measured were ng I-TEQ/m 3 and ng I-TEQ/m 3 for the normal operation conditions and ng I-TEQ/m 3 and ng I- TEQ/m 3 for the test performed with substitute secondary fuels, respectively. Dioxin-Like Compounds O O 2,3,7,8-Tetrachlorodibenzo-p-dioxin Dioxins 75 congeners 7 toxic 2,3,7,8-TCDD 1,2,3,7,8-PeCDD 1,2,3,4,7,8-HxCDD 1,2,3,6,7,8-HxCDD 1,2,3,7,8,9-HxCDD 1,2,3,4,6,7,8-HpCDD 1,2,3,4,6,7,8,9-OCDD O 2,3,7,8-Tetrachlorodibenzofuran Furans 135 congeners 10 toxic 2,3,7,8-TCDF 1,2,3,7,8-PeCDF 2,3,4,7,8-PeCDF 1,2,3,4,7,8-HxCDF 1,2,3,6,7,8-HxCDF 1,2,3,7,8,9-HxCDF 2,3,4,6,7,8-HxCDF 1,2,3,4,6,7,8-HpCDF 1,2,3,4,7,8,9-HpCDF 1,2,3,4,6,7,8,9-OCDF PCBs 209 congeners 12 toxic 3,3',4,4'-TeCB 3,3',4,4',5-PeCB 3,3',4,4',5,5'-HxCB 3,3',4,4',5,5'-Hexachlorobiphenyl 9

10 PCDD/PCDF formation in thermal processes and subsequent emission can result from a combination of formation mechanisms, depending on kiln and process configuration, process and combustion conditions, feed characteristics, and type and operation of the APCD. PCDD/PCDF formation requires the simultaneous presence of the following factors (considered to be most important): A temperature C (350 0 C); Time; Catalysts / particulate surfaces; Organics (precursors, HCs,, C); Chlorine (H, 2, *, HC-,, - ). Temperature, time and particulate surfaces o C Main sources of organics o C Organics from raw materials, fuel & wastes o C Precursors formed as PICs in the PH Input of fuels and raw meal Cement production involves heating of crushed limestone, quarts, iron & alumina in large kilns Main Flame: Fuel in liquid or pulverized form Secondary firing: Liquid, pulverized or lump fuel Raw Meal: (ground raw material) Rotary Kiln Cyclone Preheater inker Cooler 10

11 Behaviour of raw meal Natural Raw Meal Concentration CH4 C2H4 C6H6 Relative Mass [%] [%] 10 5 C2H Temperature [ C] CH4 C2Hx C3Hx C4Hx C5Hx C6H6 Aromates Expulsion between 250 and 550 [ C] Methane between 250 and 700 [ C] Generally not a problem! Typical case: 85 [%] Aliphatic structures 15 [%] Aromatic structures Organics cannot survive the main flame! Measurements of CO, VOC and benzene (C 6 H 6 ) at kiln inlet 200 < CO < 1250 [ppm] VOC and benzene not detectable! No influence from main flame Waste feeding to a preheater/ precalciner kiln Rotary Kiln Cyclone Preheater inker Cooler Kiln without secondary firing Vietnam 11

12 C H 3 NH F 3 C O C O CH 3 N N NH 2 CN S O CF 3 CHCH 2 CH 3 Several BAT cement kilns in Vietnam 12

13 39,500 litres of two toxic insecticides were safely destroyed in less than 20 hours DRE & DE % > > No PCDD/Fs, PCBs & HCB were detected The toxic insecticide also reduced the coal consumption with 2.5 t coal/h Sri Lanka, August

14 PCB in Colombo Test Burn with PCBs in Puttalam Cement Kiln, Sri Lanka August

15 Result of Test Burn in Sri Lanka Feeding l/h PCB conc. mg/l %DRE (corrected for background) Test Burn , Test Burn , No HCB was detected and no influence on the PCDD/PCDF emissions could be established (<0.018 ng I- EQ/m 3 under Baseline conditions). Venezuela Nov >6000 tonnes of POPs contaminated soil (Aldrin, Endrin and Dieldrin) 15

16 Three day test for determining the DRE/DE 2 t/h to the kiln inlet Test Burn in Venezuela Test Burn 1 Test Burn 2 Test Burn 3 Feeding kg/h Dieldrin conc. mg/kg % DRE No HCB was detected and no influence on the PCDD/PCDF emissions could be established (< ng I- TEQ/m 3 ; Baseline < ng I- TEQ/m 3 ). 16

17 Source category Cement kilns firing hazardous waste are explicitly mentioned in the Stockholm Convention, Annex C part II, as industrial source having the potential for comparatively high formation and release of dioxins to the environment Were does this information come from? Basically from testing of wet kilns co-processing hazardous waste in the US in the 1980s and the 1990s. The US regulation requires testing under worst case scenario conditions, which at that time meant for example high temperature in the APCD conditions known today to stimulate dioxin formation. Tested under worst case scenario conditions as high temp in ESP. US raw materials also contain high amounts of organics, which can be stripped of (precursor) Volumes of Hazardous Waste Burned for Energy Recovery in U.S. Cement Kilns Tons (in thousands) dioxin/2k-update/ Dry kilns were tested under normal conditions g TEQ/y US EPA revised PCDD/F release estimates for cement kilns was reduced by 97% in 7 years HWC cement kilns D/F emission reduction 431 EPA first estimate for EPA revised estimate 1990 for ,1 EPA estimate for 1996 EPA estimate for 1997 In the development of the Hazardous Waste Combustor (HWC) Maximum Achievable Control Technology (MACT) rule, EPA noted that hazardous waste burning in cement kilns does not have an impact on dioxin/furan formation, dioxin/furan is formed postcombustion (Federal Register, 64 FR 52876, September 30, 1999). 17

18 UNEP Standardized Toolkit for Identification and Quantification of Dioxin and Furan Releases In the USA, earlier tests indicated that higher emissions were found for some wet kilns where hazardous wastes were fired. More detailed investigation suggested that provided combustion is good - the main controlling factor is the temperature of the dust collection device in the gas cleaning system. The plants equipped with low temperature electrostatic precipitators appear to have well controlled emissions with or without waste fuels Emission factors for cement production No differentiation on firing hazardous wastes; only on technology and the temperature in the APCD! The main factors influencing the formation of PCDD/PCDFs in cement production: Temperature in the APCD Organics in the raw material Process mode & operation Process technology Chlorine is not a limiting factor The following primary measures are considered to be most critical l in reducing/controlling the emissions of PCDD/PCDF from cement kilns Quick cooling of kiln exhaust gases to lower than 200 o C in wet and long dry kiln; Characterize good operation and identify changes when feeding waste; Monitoring and stabilisation of critical process parameters, i.e. homogenous raw mix and fuel feed, regular dosage and excess oxygen, stable kiln operation and monitoring of CO; Pre-treat waste to make it more homogenous and create stable combustion and lower emissions; The following primary measures are considered to be most critical l in reducing/controlling the emissions of PCDD/PCDF from cement kilns Careful selection and control of substances entering the kiln; Appropriate storage, handling and feeding of waste; No waste feed as part of raw-material-mix if it includes organics; No alternative fuel feed during start-up and shut down; Feeding trough the main or secondary burner (>900 o C); Dust should be fed back to the kiln as much as possible. C o n c l u s i o n More than 2200 PCDD/PCDF measurements show that most modern cement kilns can meet an emission level of 0.1 ng TEQ/Nm 3, also when co-processing wastes and hazardous wastes. Only a few percent of the measurements were slightly above this level; the average of all measurements was approximately 0.02 ng TEQ/Nm 3. Studies indicates that the formation and release of PCDD/PCDFs from cement kilns co-processing hazardous wastes are not due to the hazardous waste as such but rather a result of site specific process conditions, like organics in the raw material, the temperature regime in the APCD, the operation mode and the process technology. Responsible and proper co-processing of hazardous wastes in cement kilns is however important to avoid formation of PCDD/PCDFs. 18

19 T h a n k y o u! 19