Optimization of the
thermal substitution rate – Part 1

1 Kiln burner

2 Tertiary air joining the calciner

3 Illustration of air-through precalciner riser duct [dimensions in mm]

4 Grid arrangements used for calciner
MI-CFD model

5 Lower petcoke burner location and its orientation

6 Velocity vectors and upward component of velocity

7 Illustration of the flow inside the riser duct

8 Petcoke particle and hot meal particle trajectories – colours indicate residence times in seconds

9 Mixing of CO₂ released by char combustion

10 Oxygen concentration [kg/kg] (cut off at 6 % O₂)

11 Temperature distribution inside the precalciner riser duct chamber [in C°]

12 Increased height of an inclined in-line precalciner by 3 m

13 Petcoke particles’ residence time in the riser duct (a = Base case, b = extended riser duct with lower burner location)
[in sec.]

14 Higher momentum burner’s petcoke particle trajectories

15 Kiln hood, kiln burner and kiln layout [dimensions in mm]

16 Kiln burner configuration

17 Computational domain of kiln, kiln hood and kiln burner

18 Temperature profile [in °C] (Temperature at oven exit = 1077°C)

19 Oxygen concentrations [in mass %] (O₂ concentration at oven exit = 5,75%)

20 Velocity vector field with magnitude
[in m/s]

Cement plant

21 Kiln bed temperature along the kiln length [in °C/m]

22 Major species of formed clinker

23 Typical temperature profile of gas phase

24 Burner injection locations of biosolids and SRF

25 Particle trajectories of a simulation with an achieved fuel mix of 90% TSR (SRF 45%, BS 45% and natural gas 10%)

26 Particle trajectories of a simulation with an achieved fuel mix of 75% TSR (SRF 75%, natural gas 25%)

27 Predicted clinker composition of its major constituents (SRF 45%, BS 45% and natural gas 10%)

28 Predicted clinker composition of its major constituents (SRF 75%, natural gas 25%)

By means of MI-CFD modeling, improvements to AFR thermal substitution rates (TSR) can be easily validated. Two case studies are presented where coal and natural gas were replaced with petcoke and AFR (SRF and BS).

Introduction

In a drive to reduce production costs and improve the environment, the cement industry is using more and more inexpensive fuels and raw materials, such as AFR and petcoke. Some successful examples show thermal substitution rate (TSR) as high as 90 % for AFR and 100 % for petcoke with up to 7 % sulphur content. A quick fix in the absence of well-structured strategy, either a lower TSR is achieved or plant would suffer from loss in output and/or increase in emissions, unless a step by step approach is carried out with the help of detailed process knowledge and experience. Cinar has...