Present challenges for modern Cement Plants. Arturo Abarca, REFRATECHNIK México S.A. de C.V. XXVII Technical Congress FICEM-APCAC

Transcription

1 Present challenges for modern Cement Plants Arturo Abarca, REFRATECHNIK México S.A. de C.V. XXVII Technical Congress FICEM-APCAC

2 Agenda Energy-Efficiency CO 2 -Emissions Clinker Cement Summary / Discussion

3 source: vdz

4 source: vdz

5 Targets for Decrease in Energy Intensity, (World Business Council for Sustainable Development) 4 3,9 3,9 3,8 3,7 3,6 3,5 3,4 Gj/Tonne 3,6 3,4 3,3 3,2 3,2 3,

6 Change of circumstances for Cement Production (I) 30 years before 100 % fuel or coal 1 fuel simple power supply 1 major product (CEM I) CO 2? Today 5 and more combustibles spot quantities possible peak-/off-peak-e-supply special E-net-rates for atypical power consumption large variety of composite cements emission trading CO 2 monitoring

7 CO 2 -emissions in the cement industry 1. Raw material related emissions: clinker: cement: 0,53 t CO2/ t clinker 0,40 t CO2/ t cement Decarbonation of limestone 2. Fuel related emissions: 0,34 t CO2/ t cement Combustion of fossil fuels 3. Energy related emissions from electricity consumption: 0,29 t CO2/ t cement Grinding, cooling air etc.

8 Targets for CO 2 total emissions, Gtonne (World Business Council for Sustainable Development) 2,50 2,00 Baseline emissions 1,88 2,33 2,20 2,22 1,86 2,34 1,50 1,55 1,00 0,50 Gtonne CO 2 Blue emissions 0,

9 Cost optimization in the cement industry Alternative Fuels + lower costs +/- process - logistics - investments - surveillance Lower clinker content + lower CO 2 costs - higher grade clinker - logistics/storage - investments? - quality control - lower production costs?

10 Change of circumstances for Cement Production 30 years before 1 major product (CEM I) Today large variety of composite cements HPC also with composite cements 42,5 R and 52,5 R extreme fine grinding combo grinding high performing Clinkers required

11 Early strength Higher fineness: CEM II/A-S (15 20 % S) CEM II/A-V (15-20 % V) CEM II/A-LL (15-20 % LL) to 500 Blaine to 1000 Blaine to 1200 Blaine Activating grinding aids: Possible gain of early strength 2 4 N/mm² (after 1 or 2 d)

12 Composite Cements Grindability of different main constituents acc. Zeisel for 4000 Blaine Clinker Fly ash > 45 µm Limestone Slag kwh/t kwh/t 5 15 kwh/t kwh/t

13 Targets for cement to clinker ratio, (World Business Council for Sustainable Development) 78% 77% 77% 76% 75% 74% 73% 72% Clinker % 74% 73% 71% 71% 70%

14 Alternative Fuels

15 Targets for alternative fuels use, (World Business Council for Sustainable Development) 80% 70% 60% 50% 40% 30% 20% 10% 0% % AF 37% 23% 12% 5%

16 Alternative fuel utilization in German cement plants ,1 7,4 10,2 10,8 13,4 15,8 18, ,7 30,3 34,9 38,4 42,1 0 47, ,5 54, Source: VDZ 2006 Target for 2050 (WBCSD) 37% Substitutionsrate in %

17 Petcoke an Alternativ fuel Secondary fuel from oil refinery coker units Petroleum coke or Petcoke High Carbon content High calorific value (~ 30GJ/t) Low volatiles (<11%) Low ash content Very low ash content <1% High Sulfur content 2-6% (price strongly depending on the S-content)

18 Going from coal to petcoke: What changes? Raw coal Uniform blending petcoke/raw coal (if petcoke < 100%) Coal mill Requires higher fineness (due to less volatiles) Affects mill capacity (different grindability and higher fineness, evaluate by trial) Kiln Low ash and high CV Low reactive fuel, ignition delayed High sulfur causing more plugging (kiln inlet/preheater) Stable and controlled kiln process to minimize sulfur cycles Clinker quality More SO 3 in clinker (better strength development, red. gypsum addition)

19 Rules: Basic potential & supply Alkali/sulfur For a first conservative approach, go for following total inputs : SO 3 inputs < 1.5 % (clinker basis) Molar A/S > 0.8 On precalciner kilns even better result are achievable, under ideal conditions : Petcoke supply SO 3 inputs < 2.5 % Molar A/S down to 0.4 Top grade (2%S, HGI>55) High grade (4%S, HGI>55) Low grade (6/7% S, HGI 40)

20 Petcoke : Mixing & Grinding Raw coal/petcoke preparation Controlled mixing from two feed hoppers Coal mill Recommended fineness for 100 % petcoke R 90 µ < 5 % R 200 µ < 1% Determine mill output by trial (HGI can be misleading) depending on the shot -amount

21 Inside the Kiln Curcuits inside rotary kilns

22 Hot meal Indication of process stability Risk of coating due to SO 3 and Cl concentration in hot meal Hot meal analysis Adequate frequency, usually once per shift Monitor LOI (decarbonation), SO 3, K 2 O SO 3 < 5 % (if chlorine < 0.5%)

23 Preheater care Preheater cleaning Add poking possibilities and air cannons (can be up to 100) where coatings occur Removing of heavy blockages can also be done with CARDOX blasting on demand. Anti coating SiC-refractories in the riser duct Observation of the Temperature-profile inside the inlet/rising duct

24 Clinker chemistry Alkalisulfate on Alit

25 Clinker chemistry K 2 SO 4 has a melting point at 1069 C evaporation/condensation-circuits will develop low alkali/sulfate ratio may have an impact on setting high alkali/sulfate ratio K 2 SO 4 - High solubility in water - much quicker than Hemihydrates or Anhydrite - may help the workability

26 Reaction of Volatile Elements with Refractory Materials Sulfates Chlorides Alkalis (sulfides) Basic bricks reaction infiltration infiltration, reaction (C 2 S, C 3 MS 2, CMS, KFeS 2 ) (KFeS 2 ) Alumina bricks reaction infiltration reaction (C 4 A 3 SO 3 ) (KAS 4, KAS 6 ) Castables reaction infiltration reaction (C 4 A 3 SO 3 ) (KAS 4, KAS 6 ) Kiln shell, reaction catalytic reaction reaction Metallic anchors (NiS, Cr 2 S 3 ) (chromate formation)

27 Essential Chemical Reactions of Kiln Atmosphere Compounds with Basic B Brick Compounds Oxidizing Atmosphere 2 C 2 S + MgO +SO 3 CaSO 4 + C 3 MS 2 C 3 MS 2 + MgO +SO 3 CaSO CMS CMS + MgO +SO 3 CaSO 4 + M 2 S 2 CaSO 4 + K 2 SO 4 2 CaSO 4.K 2 SO 4 3 MgO.Al 2 O CaO + SO 3 4CaO.3Al 2 O 3.SO MgO

28 Essential Chemical Reactions of Kiln Atmosphere Compounds with Basic B Brick Compounds Reducing Atmosphere 4 MgO + 2 K 2 O + 4 FeO.Al 2 O SO 2 4 KFeS MgO.Al 2 O O 2 MgFe 2 O 4 + K 2 O + 4 SO 2 2 KFeS 2 + MgO + 6 O 2 red. (1) 2 KFeS O 2 K 2 SO 4 + Fe 2 (SO 4 ) 3 ox. (2) PbO + SO 3 PbS + 2 O 2 2 CO CO 2 + C (Boudouard s equilibrium)

29 Essential Chemical Reactions of Kiln Atmosphere Compounds with Alumina Brick Compounds A 3 S SiO 2 +3 K 2 O 3 KAS 6 (feldspar formation) A 3 S SiO 2 +3 K 2 O 3 KAS 4 (leucite formation) 2 A 3 S SiO 2 +6 K 2 O 6 KAS 2 (kalsilite formation) 11 Al 2 O 3 + K 2 O + Na 2 O (K,N)A 11 (ß-corundum formation) K 2 SO 4.2CaSO 4 + H 2 O CaSO 4.K 2 SO 4.H 2 O (syngenite formation) 2 CaSO 4 + K 2 SO 4 2CaSO 4.K 2 SO 4

30 Spalling of a basic brick caused by elasticity differences due to infiltrations hot face Corrosion by sulfates Crack formation due to elasticity differences Infiltration and condensation of chlorides cold face

31 Conflicting goals? POSIBLE MEASURES TO REACH GOAL CO2 reduction Reduction in energy intensity Use of fluxing agents? CONFLICT Changes in clinker chemistry Higher quality clinker Higher C 3 S content Lower clinker burnability Reduction in the clinker to cement ratio Higher energy consumption for clinker production

32 Conflicting goals? POSIBLE MEASURES TO REACH GOAL CO2 reduction Reduction in energy intensity Use of fluxing agents? CONFLICT Changes in clinker chemistry Higher quality clinker Higher C 3 S content Lower clinker burnability Reduction in the clinker to cement ratio Higher energy consumption for clinker production

33 Conflicting goals? POSIBLE MEASURES TO REACH GOAL CO2 reduction Reduction in energy intensity CONFLICT Increased wear of grinding media Increased energy consuption in cement grinding Finer Grinding Reduction in the clinker to cement ratio

34 Wherever in the world you are, the road ahead is full of new challenges. But you are not alone Refratechnik is there, to help you meet these challenges!

35 Thank you very much for your kind attention