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Jun 11, 2023 14 likes •218 views

Use of high-calcium ladle slag as a partial limestone substitute for clinker manufacturing with reduced CO 2 emissions M. Mancio, A.P. Kirchheim, A.B. Masuero NORIE UFRGS Brazil Paper #595, Toms Vzquez room, July 5th 16:50 Outline

SLIDE 1

Use of high-calcium ladle slag as a partial limestone substitute for clinker manufacturing with reduced CO2 emissions

M. Mancio, A.P. Kirchheim, A.B. Masuero

NORIE – UFRGS – Brazil Paper #595, Tomás Vázquez room, July 5th 16:50

SLIDE 2

Outline

Introduction Environmental impact of clinker production Ladle slag Generation process, main characteristics Clinker production tests

Partial replacement of limestone to reduce CO2

Results and discussion

Preview of industrial-scale tests

Final comments

SLIDE 3

Today climate change is a major global concern

CO2 concentration measured over the last 800,000 yrs

Introduction

Source: Karl, T.R. et al. June 2009. Available at: www.globalchange.gov/usimpacts

Note: current emissions are higher than the “higher emissions scenario” assumed in this projection

SLIDE 4

Cement production & CO2 emissions: business as usual is not an option!

Introduction

SLIDE 5

Typical rotary cement kiln equipped with preheater and precalciner.

Mass proportion

Lime

Introduction

SLIDE 6

Annual reductions of 5 to 7 billion tons in CO2 emissions are required in the next 10 years (in order to keep CO2 concentration below 450 ppm)

About 1 billion tons/year could be reduced by 2020 by replacing 50% of Portland cement by low-carbon alternatives.

Source: Gigaton Throwdown Initiative (http://www.gigatonthrowdown.org)

SLIDE 7

Large part of CO2 emissions in clinker production comes from the use of limestone Partially replacing CaCO3 by alternative sources of CaO can be an effective way of reducing CO2 emissions

Industrial by-products rich in CaO

One such alternative is ladle slag

By-product from steel production in electric-arc furnaces Favorable chemical composition: 44% CaO, 35% SiO2

Ladle slag

SLIDE 8

Ladle slag generation

SLIDE 9

Ladle furnace Ladle slag being poured

Ladle slag generation

SLIDE 10

Characterization of raw materials
Chemical compositions used for the calculations (XRF)
Evaluation of potential toxicity characteristics of Ladle

slag (TCLP tests)  non-hazardous waste

Proportioning of raw materials
Based on the desired clinker composition and specified

lime saturation factor (LSF), silica ratio (SR) and alumina ratio (AR) parameters

Clinker production tests

Ladle slag Limestone meal Rice husk ash Fly ash CaO 43.7% 71.0% 1.8% 0.7% SiO2 35.5% 14.2% 93.2% 70.0% Al2O3 3.3% 2.9% 0.7% 14.6% MgO 6.6% 5.0% 0.4% 1.0% Fe2O3 3.5% 4.7% 0.2% 6.5%

SLIDE 11

Mixtures used for the laboratory clinker production experiments

Clinker production tests

Mix 1 Mix 2 Mix 3 Mix 4 Limestone-based meal 90% 83% 83% 65% Ladle slag 0% 9% 9% 35% Rice husk ash 10% 8% – – Fly ash – – 8% – Total 100% 100% 100% 100% Limestone replacement 0% 7,8% 7,8% 27,8% CO2 reduction 0% 5,9% 5,9% 23,1%

SLIDE 12

Clinker production in the lab

SLIDE 13

Chemical composition of lab clinkers

X-ray fluorescence tests

Results

Control Clinker 1 Clinker 2 Clinker 3 Clinker 4 CaO 60% to 62% 61,4% 60,1% 60,2% 58,0% SiO2 20% to 21% 23,3% 23,6% 22,1% 22,7% Al2O3 4,0% 4,5% 4,0% 5,3% 4,8% MgO 7,3% 4,9% 5,6% 5,1% 6,1% Fe2O3 3,0% 5,0% 5,1% 5,4% 5,2% MnO – 0,3% 0,7% 0,6% 1,9% LSF 0,92 to 0,99 0,83 0,81 0,84 0,80 LSF (II) 1,08 to 1,16 0,93 0,92 0,95 0,93 SR 2,92 to 3,07 2,44 2,59 2,05 2,25 AR 1,33 0,90 0,79 0,98 0,93

SLIDE 14

Mineralogical composition

XRDs (qualitative analysis)

Position [°2Theta] 10 20 30 40 50 60 70 100 400 form_1a

Clinker 1

Raw mix = 83% RHA = 10% Main phases:

C2S
C3S
C3A
C4AF
MgO

Results

SLIDE 15

Mineralogical composition

Quantification of phases formed

SEM ATAQUE QUÍMICO MgSO4 - 5% EM ÁGUA - 10s HNO3 1% EM ÁLCOOL + 1/3 ÁGUA - 1s HNO3 0,1% EM ÁLCOOL - 10s + NH4Cl 0,1% EM ÁGUA - 10s

Analyses in optical microscope w/ pixel counting

Quantitative

analysis

Provides more

reliable data than Bogue estimates

Results

Figure source: M.A. Cincotto

SLIDE 16

Main phases formed

CaO 1.0% Alita 9.3% Belita 75.6% MgO 3.4% C4AF 9.1% C3A 1.6%

Results

Clinker 1 Clinker 2 Clinker 3 Clinker 4 Control (Bogue) Belite (C2S) 75,6% 83,1% 75,7% 75,7% 16,5% Alite (C3S) 9,3% 3,9% 7,3% 3,1% 69,0% C3A 1,6% 0,8% 2,4% 2,7% 5,1% C4AF 9,1% 7,8% 9,8% 13,5% 9,0% CaOfree 1,0% 0,6% 0,1% 0,7% 1% to 5% Periclase 3,4% 3,8% 4,7% 4,2% 7,3% C3S + C2S 85,7% 87,0% 83,0% 78,8% 85,5% C3A + C4AF 9,8% 8,7% 12,2% 16,3% 14,1%

SLIDE 17

Partnership with local steel and cement producers

Industrial-scale tests

SLIDE 18

Quality control one day before, during and after the industrial-scale tests

10 20 30 40 50 60 70 80

C3S C2S C3A C4AF

Industrial-scale tests

SLIDE 19

Ladle slag is a byproduct from steel production in electric mills that is routinely treated as waste and disposed off in landfills It presents high levels of CaO and SiO2, in addition to low Fe content, a very favorable composition for incorporation into clinker manufacturing This study evaluated, for the first time, the technical and environmental feasibility of using this slag for clinker production The material is classified as a non-hazardous waste, and can be safely used as a raw material in cement production

Final comments

SLIDE 20

It was possible to produce lab-made experimental clinkers with Ladle slag as a partial limestone substitute, thus enabling considerable reductions in CO2 emissions related to the calcination reaction The chemical composition of the produced clinkers closely resembled the reference industrial clinker, and the total content of calcium silicates (C2S + C3S) formed was satisfactory However, the relative quantity of C2S was higher than expected, which is likely due to the elevated silica content, a short sintering time, and a fast cooling rate in the lab