# US 12,768,595 B2 · Method and system of predicting safe time of operation for a rotary kiln

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- Number: US 12,768,595 B2
- Document ID: US12768595B2
- Status: Granted
- Kind: B2
- Application number: 18/799,311
- Filed: 2024-08-09
- Published: 2025-03-13
- Granted: 2026-10-20
- Earliest claimed: 2023-09-08
- Assignees: Tata Consultancy Services Limited
- Applicants: Tata Consultancy Services Limited
- Inventors: Akanksha Dhayal; Sivakumar Subramanian; Venkataramana Runkana; Mohammed Suhail
- Web page: https://patentgrep.com/patent/US12768595B2

## CPC

- F27B 7/42: Arrangement of controlling, monitoring, alarm or like devices
- F27D 21/00: Arrangement of monitoring devices; Arrangement of safety devices
- F27B: FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27D: DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE

## Abstract

This disclosure relates generally to a method and system for predicting safe time of operation for a rotary kiln. Over the period of time, the rotary kiln develops a ring within the inner walls of the kiln and suffers sudden shut down due to choking of the kiln. State-of-the-art methods provide the various methods of predicting safe time of operation, but the prediction is based on limited features and hence suffers accuracy. The disclosed method predicts safe time of operation for a rotary kiln based on mathematical model that estimates size of ring by estimating plurality of derived parameters based on operational parameters and design parameters. The derived parameters are the estimations provided by a solid bed height variation model, a gas stream model, a solid stream, a melt model, an agglomeration model, a volatile model, and a ring formation model.

## Claims

### Claim 1

A processor implemented method of monitoring performance of a rotary kiln by predicting safe time of operation, the method comprising:
receiving, via one or more hardware processors, a plurality of operational parameters and a plurality of design parameters of the rotary kiln,
obtaining, via the one or more hardware processors, a plurality of derived parameters by processing one or more operational and design parameters using, a set of models executed by the one or more hardware processors, the set of models comprising
a solid bed height variation model to estimate a height parameters of the solid bed along the kiln length,
a gas stream model to estimate a gaseous phase parameters associated with a plurality of gaseous components in the gas stream introduced through the discharge end of the rotary kiln,
a solid stream model to simultaneously estimate (i) reaction kinetics of the solid bed associated with a plurality of components formed in the rotary kiln as a result of plurality of reactions occurring within various components of the solid bed and a molten phase formed within the rotary kiln, and (ii) temperature parameters of the solid bed and the kiln walls by aggregating the obtained reaction kinetics and heat balance in the rotary kiln,
a melt model to estimate rate of formation of molten phase by calculating energy parameter associated with the total available solid material along the length of the kiln,
an aggregation model to calculate rate of interaction among particles of the solid bed and molten phase forming an aggregate by obtaining interaction parameters, and
a volatile model by simultaneously estimating the flow rate of volatile compounds circulating in the rotary kiln; and the deposition rate of the volatile compounds at the inner walls of the rotary kiln forming a ring, wherein the volatile compounds iteratively experience change in state parameters along the length of the rotary kiln causing deposition and re-circulation; and
aggregating, via the one or more hardware processors, by a ring model executed by the one or more hardware processors, the set of height parameters, the gaseous phase parameters, the temperature parameter, the energy parameter, the interaction parameters, and the state parameters to estimate ring thickness, net ring growth and strength of the deposited material in the rotary kiln to predict safe time of operation of the rotary kiln.

### Claim 2 (depends on 1)

The method of claim 1, wherein plurality of design parameters comprises of kiln tilt angle, angle of repose for solid material, the radius of the rotary kiln and rotational speed of the kiln and wherein operational parameters comprises of solid feed rate, solid particle size distribution, solid chemical composition, temperature of kiln at the feed end, discharge end, at the middle, within the lumen of the kiln and near the walls of the rotary kiln.

### Claim 3 (depends on 1)

The method of claim 1, wherein the solid bed height variation model estimates the height of the solid bed by assuming a certain bed height at the discharge end as an initial condition and subsequently calculating the solid bed height parameters along the length that varies from the discharge end to the feed end, and wherein the solid bed height parameters predicts cross-section area of the solid stream, gas stream and available interfacial heat transfer area in between solids, gases and kiln walls.

### Claim 4 (depends on 1)

The method of claim 1, wherein the gas stream model calculates reaction kinetics of the plurality of gaseous components of the gas stream to obtain overall heat balance, wherein a part of gaseous components is introduced through a fuel injected from the discharge end and a part of gaseous components are obtained through the reactions of the solid bed triggered by high kiln temperature.

### Claim 5 (depends on 1)

The method of claim 1, wherein the melt model estimates the rate of formation of the molten phase as the solid feed travels towards discharge end wherein a rate of molten phase formation is calculated by:
d
⁢
L
d
⁢
t
=
K
c
⁢
o
⁢
r
⁢
r
⁢
N
0
(
4
⁢
π
⁢
R
m
⁢
e
⁢
a
⁢
n
2
)
⁢
K
l
(
T
b
-
T
s
)
λ
⁢
Q
s
and wherein, numerator term represents the total energy received by the solid bed having solidus temperature and the denominator represents the total energy required by the total available solid material in the kiln along the length.

### Claim 6 (depends on 1)

The method of claim 1, wherein the aggregation model estimates the particle size distribution of a continuous system preserving the solid volume utilizing a coalescence kernel given by:
coalescence kernel (βi,j)=amount of melt fraction×kg
wherein, kg is the calibration factor.

### Claim 7 (depends on 1)

The method of claim 1, wherein the gaseous component of the gas stream is a fuel introduced to the rotary kiln from the discharge end or is a gas mixture introduced to the kiln or the volatile compounds and other gaseous components present in the solid bed and released in the temperature triggered solid bed reaction or a mixture of above three,
and wherein, the net flow rate of the volatile compounds inside the rotary kiln is calculated by adding (i) net deposition rate of volatile compounds at the inner walls of the rotary kiln, (ii) circulation rate of low melting volatile compounds evaporating with the increasing temperature of the solid bed along the length of the kiln and re-circulating with gas stream in the kiln, and (iii) the high boiling volatile compounds remained trapped in the solid bed and exiting along with the discharged product,
and wherein the solid bed height variation model, the solid stream model, the melt model, the aggregation model and the volatile model perform estimations along the length of the rotary kiln, from the feed end towards the discharge end, and the gas stream model perform estimations along the length of the rotary kiln, from the discharge end towards the feed end.

### Claim 8

A system, comprising:
a memory storing instructions;
one or more communication interfaces; and
one or more hardware processors coupled to the memory via the one or more communication interfaces, wherein the one or more hardware processors are configured by the instructions to:
receive a plurality of operational parameters and a plurality of design parameters of the rotary kiln;
obtain a plurality of derived parameters by processing one or more operational and design parameters using, a set of models, the set of models executed by the one or more hardware processors comprising
a solid bed height variation model to estimate a height parameters of the solid bed along the kiln length,
a gas stream model to estimate a gaseous phase parameters associated with a plurality of gaseous components in the gas stream introduced through the discharge end of the rotary kiln,
a solid stream model to simultaneously estimate (i) reaction kinetics of the solid bed associated with a plurality of components formed in the rotary kiln as a result of plurality of reactions occurring within various components of the solid bed and a molten phase formed within the rotary kiln, and (ii) temperature parameters of the solid bed and the kiln walls by aggregating the obtained reaction kinetics and heat balance in the rotary kiln,
a melt model to estimate rate of formation of molten phase by calculating energy parameter associated with the total available solid material along the length of the kiln,
an aggregation model to calculate rate of interaction among particles of the solid bed and molten phase forming an aggregate by obtaining interaction parameters,
a volatile model to simultaneously estimate, the flow rate of volatile compounds circulating in the rotary kiln, and the deposition rate of the volatile compounds at the inner walls of the rotary kiln forming a ring, wherein the volatile compounds iteratively experience change in state parameters along the length of the rotary kiln causing deposition and re-circulation; and
aggregate by a ring model the set of height parameters, the gaseous phase parameters, the temperature parameter, the energy parameter, the interaction parameters and the state parameters to estimate ring thickness, net ring growth and strength of the deposited material in the rotary kiln to predict safe time of operation of the rotary kiln.

### Claim 9 (depends on 8)

The system of claim 8, wherein plurality of design parameters comprises of kiln tilt angle, angle of repose for solid material, the radius of the rotary kiln and rotational speed of the kiln and wherein operational parameters comprises of solid feed rate, solid particle size distribution, solid chemical composition, temperature of kiln at the feed end, discharge end, at the middle, within the lumen of the kiln and near the walls of the rotary kiln.

### Claim 10 (depends on 8)

The system of claim 8, wherein the solid bed height variation model estimates the height of the solid bed by assuming a certain bed height at the discharge end as an initial condition and subsequently calculating the solid bed height parameters along the length that varies from the discharge end to the feed end, and wherein the solid bed height parameters predicts cross-section area of the solid stream, gas stream and available interfacial heat transfer area in between solids, gases and kiln walls.

### Claim 11 (depends on 8)

The system of claim 8, wherein the gas stream model calculates reaction kinetics of the plurality of gaseous components of the gas stream to obtain overall heat balance, wherein a part of gaseous components is introduced through a fuel injected from the discharge end and a part of gaseous components are obtained through the reactions of the solid bed triggered by high kiln temperature.

### Claim 12 (depends on 8)

The system as claimed in claim 8, wherein the melt model estimates the rate of formation of the molten phase as the solid feed travels towards discharge end wherein a rate of molten phase formation is calculated by:
d
⁢
L
d
⁢
t
=
K
c
⁢
o
⁢
r
⁢
r
⁢
N
0
(
4
⁢
π
⁢
R
m
⁢
e
⁢
a
⁢
n
2
)
⁢
K
l
(
T
b
-
T
s
)
λ
⁢
Q
s
and wherein, numerator term represents the total energy received by the solid bed having solidus temperature and the denominator represents the total energy required by the total available solid material in the kiln along the length.

### Claim 13 (depends on 8)

The system as claimed in claim 8, wherein the aggregation model estimates the particle size distribution of a continuous system preserving the solid volume utilizing a coalescence kernel given by:
coalescence kernel (βi,j)=amount of melt fraction×kg
wherein, kg is the calibration factor.

### Claim 14 (depends on 8)

The system as claimed in claim 8, wherein the gaseous component of the gas stream is a fuel introduced to the rotary kiln from the discharge end or is a gas mixture introduced to the kiln or the volatile compounds and other gaseous components present in the solid bed and released by temperature triggered solid bed reaction or a mixture of above three,
and wherein the net flow rate of the volatile compounds inside the rotary kiln is calculated by adding (i) net deposition rate of volatile compounds at the inner walls of the rotary kiln, (ii) circulation rate of low melting volatile compounds evaporating with the increasing temperature of the solid bed along the length of the kiln and re-circulating with gas stream in the kiln, and (iii) the high boiling volatile compounds remained trapped in the solid bed and exiting along with the discharged product,
and wherein the solid bed height variation model, the solid stream model, the melt model, the aggregation model and the volatile model perform estimations along the length of the rotary kiln, from the feed end towards the discharge end; and the gas stream model perform estimations along the length of the rotary kiln, from the discharge end towards the feed end.

### Claim 15

One or more non-transitory machine-readable information storage mediums comprising one or more instructions which when executed by one or more hardware processors cause:
receiving a plurality of operational parameters and a plurality of design parameters of the rotary kiln,
obtaining a plurality of derived parameters by processing one or more operational and design parameters using, a set of models executed by the one or more hardware processors, the set of models comprising
a solid bed height variation model to estimate a height parameters of the solid bed along the kiln length,
a gas stream model to estimate a gaseous phase parameters associated with a plurality of gaseous components in the gas stream introduced through the discharge end of the rotary kiln,
a solid stream model to simultaneously estimate (i) reaction kinetics of the solid bed associated with a plurality of components formed in the rotary kiln as a result of plurality of reactions occurring within various components of the solid bed and a molten phase formed within the rotary kiln, and (ii) temperature parameters of the solid bed and the kiln walls by aggregating the obtained reaction kinetics and heat balance in the rotary kiln,
a melt model to estimate rate of formation of molten phase by calculating energy parameter associated with the total available solid material along the length of the kiln,
an aggregation model to calculate rate of interaction among particles of the solid bed and molten phase forming an aggregate by obtaining interaction parameters, and
a volatile model by simultaneously estimating the flow rate of volatile compounds circulating in the rotary kiln; and the deposition rate of the volatile compounds at the inner walls of the rotary kiln forming a ring, wherein the volatile compounds iteratively experience change in state parameters along the length of the rotary kiln causing deposition and re-circulation; and
aggregating, via the one or more hardware processors, by a ring model executed by the one or more hardware processors, the set of height parameters, the gaseous phase parameters, the temperature parameter, the energy parameter, the interaction parameters, and the state parameters to estimate ring thickness, net ring growth and strength of the deposited material in the rotary kiln to predict safe time of operation of the rotary kiln.

### Claim 16 (depends on 15)

The one or more non-transitory machine-readable information storage mediums of claim 15, wherein plurality of design parameters comprises of kiln tilt angle, angle of repose for solid material, the radius of the rotary kiln and rotational speed of the kiln and wherein operational parameters comprises of solid feed rate, solid particle size distribution, solid chemical composition, temperature of kiln at the feed end, discharge end, at the middle, within the lumen of the kiln and near the walls of the rotary kiln.

### Claim 17 (depends on 15)

The one or more non-transitory machine-readable information storage mediums of claim 15, wherein the solid bed height variation model estimates the height of the solid bed by assuming a certain bed height at the discharge end as an initial condition and subsequently calculating the solid bed height parameters along the length that varies from the discharge end to the feed end, and wherein the solid bed height parameters predicts cross-section area of the solid stream, gas stream and available interfacial heat transfer area in between solids, gases and kiln walls.

### Claim 18 (depends on 15)

The one or more non-transitory machine-readable information storage mediums of claim 15, wherein the gas stream model calculates reaction kinetics of the plurality of gaseous components of the gas stream to obtain overall heat balance, wherein a part of gaseous components is introduced through a fuel injected from the discharge end and a part of gaseous components are obtained through the reactions of the solid bed triggered by high kiln temperature.

### Claim 19 (depends on 15)

The one or more non-transitory machine-readable information storage mediums of claim 15, wherein the melt model estimates the rate of formation of the molten phase as the solid feed travels towards discharge end wherein a rate of molten phase formation is calculated by:
d
⁢
L
d
⁢
t
=
K
c
⁢
o
⁢
r
⁢
r
⁢
N
0
(
4
⁢
π
⁢
R
m
⁢
e
⁢
a
⁢
n
2
)
⁢
K
l
(
T
b
-
T
s
)
λ
⁢
Q
s
and wherein, numerator term represents the total energy received by the solid bed having solidus temperature and the denominator represents the total energy required by the total available solid material in the kiln along the length,
and wherein the aggregation model estimates the particle size distribution of a continuous system preserving the solid volume utilizing a coalescence kernel given by:
coalescence
⁢
kernel
⁢
(
β
i
,
j
)
=
amount
⁢
of
⁢
melt
⁢
fraction
×
k
g
wherein
,
k
g
⁢
is
⁢
the
⁢
calibration
⁢
factor
.

### Claim 20 (depends on 15)

The one or more non-transitory machine-readable information storage mediums of claim 15, wherein the gaseous component of the gas stream is a fuel introduced to the rotary kiln from the discharge end or is a gas mixture introduced to the kiln or the volatile compounds and other gaseous components present in the solid bed and released in the temperature triggered solid bed reaction or a mixture of above three,
and wherein, the net flow rate of the volatile compounds inside the rotary kiln is calculated by adding (i) net deposition rate of volatile compounds at the inner walls of the rotary kiln, (ii) circulation rate of low melting volatile compounds evaporating with the increasing temperature of the solid bed along the length of the kiln and re-circulating with gas stream in the kiln, and (iii) the high boiling volatile compounds remained trapped in the solid bed and exiting along with the discharged product,
and wherein the solid bed height variation model, the solid stream model, the melt model, the aggregation model and the volatile model perform estimations along the length of the rotary kiln, from the feed end towards the discharge end; and the gas stream model perform estimations along the length of the rotary kiln, from the discharge end towards the feed end.