Thermax’s Cinder Recovery System Helped Reduce Loss of Ignition at a Cement Plant in Karnataka

Customer Background and Thermax Partnership: Since 2009, Thermax has been a trusted partner to a reputed cement manufacturer in Karnataka for its 6000 TPD unit, providing Operation and Maintenance (O&M) services for the 2×25 MW captive power plant. The plant has two AFBC (Atmospheric Fluidised Bed Combustion) boilers of 110 TPH capacity each generating steam at 88 ata, 520ºC. 

Problem: The customer had a challenging requirement of optimising the reuse of their hazardous waste viz. fly ash by reducing its carbon content. As a standard practice, the fly ash generated from the boiler is utilised in the cement mill. However, only the fly ash with a Loss of Ignition (LOI- the amount of carbon left in fly ash which has a potential heat value) less than 8% can be utilised, and the rest needs to be disposed of which has several constraints, considering its hazardous nature. 

Further, a high level of carbon content in ash due to Loss of Ignition is undesirable for power plants as it leads to boiler efficiency loss and higher specific fuel consumption.

Approach: To counter this situation, the team conducted an analytical study on factors affecting the increase in LOI. It was identified that LOI was increasing due to insufficient burning of fuel in the secondary part of the boiler. Change in fuel properties also had a significant contribution to the problem.

Solution: Thermax recommended the installation of a Cinder Recovery System to counter the factors leading to a higher LOI in the boiler. This system utilises unburnt carbon in the fly ash by re-firing it in the boiler, which is conveyed through the primary air.

The team made a detailed proposal with a cost benefit analysis of the Cinder Recovery System to the customer. As the system was designed by Thermax’s in-house engineering and commissioning team, the customer was relieved of any risks associated with its performance. The team also modified the intermediate storage of ash, which was resulting in a drop in the temperature of ash. 

This modification, along with the installation of the Cinder Recovery System resulted in a reduction of the LOI from 15-17% to 6-8%, while eliminating the need for disposing of hazardous waste.


  • Reduction of LOI to 6-8% benefited the customer in many ways – they were able to utilise the fly ash in cement mill and saved on the cost of fly ash disposal 
  • Boiler efficiency was improved by 0.5%
  • Heat rate reduced by 45-50 kcal/kWh
  • Fuel saving of approximately 2,250 tons/year was achieved
  • Overall fuel saving resulted in a reduction of carbon footprint by 7,321 tCO2e/year


Thermax Enviro Solutions empowers the oldest Cement Company of Egypt

About Tourah Cement

The Tourah Portland cement Plant, Egypt’s first cement company, was established in 1927. It is owned by Suez Cement company (66.12%). The company consists of two plants located in an area of 10,000,000 m2 in Tourah district with 9 production lines.

The Changing Business Scenario

Driver of the Change: Emission Standards

As global awareness and concerns grew about the Air Pollution and its hazards, Egypt also decided to upgrade the emission standards that a cement plant must meet in order to ensure a cleaner and healthier environment.

As per the changes in the law, any cement company in Egypt must meet the new emission standards of SPM < 20 Mg/NM3 from earlier acceptable limits of SPM< 100 Mg/NM3 resulting into a complete change in the business scenario for Tourah Cement.

Affected Applications, Utilities and Challenges

Application Existing APC
Raw Mill x 2 ESP x 2
Clinker Cooler GBF
Alkali By Pass & Gas Cooling Tower ESP

APC: Air Pollution Control Equipment
ESP: Electrostatic Precipitator
GBF: Gravel Bed Filter

Challenges Associated with Rehabilitation

1. Efficiently meet the expected new emission standards.
2. Minimize capex and downtime of the plant and without disturbing the other operations much.
3. Modifications and additions within the little space available posing as a significant constraint

Solution Offered by Thermax

Thermax studied the requirements of the customer and associated challenges. Based on its years of experience, Thermax Retrofit and Revamp Design team came out with a solution to be executed within 45 days planned shutdown for all the three applications. In order to reduce the Capex, Thermax used its engineering skills so that the existing structures, casing, hoppers etc can be utilized to maximum in the new solution.

Raw Mills (Both) – ESP for replaced with Pulse Jet Bag Filter

Existing Casing was repaired and partition was created to accommodate the new 2 chamber Bag House.
Existing building was strengthened and used.

Clinker Cooler – Gravel Bed Filter replaced with Heat Exchanger & Pulse Jet Bag Filter

Heat Exchanger was provided for Clinker Cooler Gases prior to entering the Bag Filter Chamber.
The Bag filter with six compartments was constructed on the structures of the existing Gravel Bed Filter New Ducting connecting to old discharge system was only used.

Alkali By-Pass & GCT -ESP replaced with Pulse Jet Bag Filter

Existing ESP Support structures & Hoppers were used to construct the New Bag Filter The existing GCT was upgraded to handle dual fuel.

Final Process Parameters

Application Offered Solution Volume(M3/Hr) Temperature(C) Inlet Dust Load(gm/NM3) Outlet Emission Achieved(mg/NM3)
Raw Mill x 2 Pulse Jet Bag Filter 630,000 200 200 < 20
Clinker Cooler Pulse Jet Bag Filter 450,000 120 20 < 20
Alkali By Pass & Gas Cooling Tower Pulse Jet Bag Filter 195,000 200 80 < 20


1. Execution of project covering all the 3 applications completed in the planned shutdown of only 45 days.
2. Equipment handed over after commissioning in just 15 days.
3. CAPEX reduced as per customers expectations by utilizing existing structures to maximum possible.

Project in Pictures

Raw Mill

Clinker Cooler

Alkali By Pass & Gas Cooling Tower

Reduction of Auxiliary Power Consumption for a Cement Plant in Rajasthan

Customer Background and Thermax Partnership: At one of the leading cement manufacturer’s unit at Rajasthan, Thermax is providing Operation and Maintenance (O&M) services for its captive power plant of capacity 21 MW and WHR power plant of capacity 13 MW since 2008. The plant has an 89 TPH AFBC (Atmospheric Fluidised Bed Combustion) boiler and 5 WHR (Waste Heat Recovery) boilers of 72 TPH combined (both boilers are made by Thermax).  

Project Background: Auxiliary power consumption is one of the key performance indicators for a power plant. As a part of the customer’s ‘energy efficiency’ drive, the Thermax team took a target of reducing the auxiliary power consumption to enhance the net power generation. 

Approach: Thermax team conducted a detailed analysis of the equipment data using advanced proprietary tools. They also organised workshops to drill down on the key parameters driving higher auxiliary power consumption.

Specific teams were formed to study:  

  1. Power consumption pattern equipment-wise and area wise 
  2. All possible ideas for improvement

Solution: Thermax team presented a comprehensive plan to the customer for reducing auxiliary power consumption for captive and WHR power plants. The plan included actions with and without capital investments. Over the span of the last two years, various opex initiatives such as ‘auto control logics for flow optimisation’ and capex initiatives such as ‘VFD installation’ were implemented. The customer also agreed for capex investment after being apprised by the Thermax team about the long term savings and lifecycle cost reduction. 


  • For the captive power plant72.4 lakhs of unit cost saved through capex and 18.8 lakhs unit cost saved through opex 
  • For WHR unit 8.7 lakhs of unit cost saved through capex and 1.9 lakhs unit cost saved through opex
  • The total auxiliary power consumption was reduced by 1% for captive power plant and 2.2% for WHR unit 
  • Carbon footprints reduced by 1,200 tCO2e/year for captive unit and 1,300 tCO2e/year for WHR unit





The shrinking profit margins and fierce competition coupled with increased taxes and higher logistics cost has compelled the cement manufacturers to reduce operating expenses and increase throughput without allocating considerable CAPEX.

This has led the Cement Manufacturers as well as Equipment Suppliers to look out for solutions which will yield maximum equipment efficiency enabling higher throughput of the existing plant. Thermax has acknowledged the market requirement and introduced a patented pulsing system that improves the bag filter performance in an innovative way. The success story of Thermax’s innovative solution to address the needs of the cement industry is presented below:


Myhome Cement, Hyderabad approached Thermax for a solution to upgrade its existing cement mill bag house to increase its mill feed capacity from 175TPH to 220TPH. However, increasing its capacity in as is condition was notpossible since the existing Induced Draft (will be referred to as ID henceforth) Fan of Cement Mill had flow & static pressure limitations due to higher pressure drop/ losses in system. The data in Table 1 presents the input parameters for existing operation and future enhancement:

Sr. No. Description Slag/Clinker Grinding Mill Bag Filter – Existing (Design Data) Slag/Clinker Grinding Mill Bag Filter – Enhanced (Design Data)
1. Cement Mill Bag filter Online Online
2. Quantity 1 1
3. Industry Cement Cement
4. Application Slag/Clinker Mill Filter Slag/Clinker Mill Filter
5. Mill Feed, TPH 175 220 (21% increase desired after Mill upgrade)
6. Volumetric flow 5,95,000 Am3/hr 7,00,000 Am3/hr (15% increase, desired)
7. Gas temperature continuous 90°C 90°C
8. Max Gas temperature Bags can Withstand 130°C 130°C
9. Bag Filter Design Pressure +/- 1500 mmwg +/- 1500 mmwg
10. Static pressure at Bag Filter inlet (max) (-)450mmwg (-)450mmwg
11. Dust to be handled Slag / Clinker Dust Slag / Clinker Dust
12. Dust properties Abrasive, Free Flowing Abrasive, Free Flowing
13. Dust concentration in the gas at Inlet of bag filter (slag only) 248 gms/m3 257 gms/m3 300 gms/m3(max)
14. Outlet Emission 30 mg/Nm3 30mg/Nm3
15. Bulk density of dust for Power 1,200 kg/m3 1,200 kg/m3
16. Particle Size Analysis 4,200 Blains 4,200 Blains
17. Moisture content in the gas Upto 8% Upto 8%
18. Moisture dew point of gas 59°C max 59°C max


Higher CAPEX
  • Generally, this kind of bag filter upgrade calls for an increase in the number of filter bags/ modules, to maintain air-to-cloth ratio (will be referred to as ACR henceforth) by increasing the fabric collection area and to maintain the Differential Pressure (will be referred to as DP
    henceforth) across the system
  • Any rework in an existing plant requires a lot of re-routing of existing facilities, in order to accommodate extra filter bags/modules. This results in increased expenditure for the customer
Space constraints

Space constraint was a challenge due to a compact plant layout and hence no space to accommodate additional bag filter modules.

Revenue loss due to downtime

Longer downtime required for addition of the bags/module resulting in loss of production and revenue accordingly



Thermax’s state-of-the-art Research, Technology and Innovation center (RTIC) has developed an innovative bag filter pulsing system which can effectively dislodge dust from bags at low pressures resulting in effective control of bag filter DP and ensure higher bag life. In fact, this also addresses the challenge of effective cleaning of long bags. The system generates low pressure pulses which travel right up to the bottom of the bag causing ripple effect on the bags and effectively dislodging dust, a panacea for cement
manufacturer’s plant operations woes.

The picture below represents the Computational Fluid Dynamics (CFD) pattern for Pulse Cleaning System; Type C is Thermax’s Intellectual Property (IP).


Sr. No. Parameters for 100% Slag Grinding Case 1 With Old Pulsing System Case 2 With Improved Pulsing System Case 3 With Improved Pulsing System
1. Mill Feed 175 – 180 175 – 180 185 – 190
2. Flow, m3/hr 5,65,000 – 5,80,000 5,65,000 – 5,80,000 7,05,000 – 7,15,000
3. Fan, RPM 800 – 810 800 – 810 980, Full RPM
4. Fan Power, KW 1,180 – 1,190 1,175 – 1,185 2,120 – 2,150
5. Pulsing Pressure, Bar 5 – 6 3.8 – 4.2 3.8 – 4.5
6. DP across Bag Filter, mmwg 90 – 100 70 – 80 115 – 120
7. Emission 30 mg/Nm3 30 mg/Nm3 30 mg/Nm3
8. Bag House Inlet/outlet Temp., °C 117 / 103 117 / 105 118 / 99

(*) Enhanced mill feed capacity of 220TPH was not achieved with old pulsing system due to very high DP across
bag house.

Thermax innovative pulsing system achieved 24% to 30% drop in pulsing pressure and 20% to 22% drop in DP
across bag filter (as in Case 2, Table 2)

The Mill Feed throughput was increased to 190 tph, but desired figure of 220 tph is yet to happen. However, the air flow in the bag filter was increased to 7,00,000 m3 /hr equivalent to 220 tph for couple of hours to observe the DP value under full load. The DP was around 115 – 120 mmwg while the original Bag Filter DP (design value) = 150 mmwg.

The above case clearly illustrates the benefits of the improved pulsing system i.e., reduced DP, reduced compressed air requirements, increased throughputs and higher bag life.

The set of benefits realised by customer (Myhome Cement) due to innovative pulsing system in an existing cement mill bag filter:

1. Savings in electric power consumption of ID fan:

Reduction of 20mmwg in dp across Bag Filter (Table 2, Case-1 & 2) would convert to 5KWH which would mean a yearly saving of 5KWH x 8,000 x Rs.5* per KWH = Rs. 2,00,000 (Rs.5 per KWH – Ave. India Industrial Unit Rate)

2.Savings in compressed air power consumption:

Reduction in pulse pressure from 5 – 6 kg/cm2 to 3.8 – 4.2 kg/cm2 , means a net reduction by 24% to 30% in air compressor operating expenses

3.Saving due to extended bag life:

Apart from other governing factors, compressed air pulse pressure and pulse frequency plays an important role in the life cycle of bag house. The innovation in the pulsing system technology by Thermax has controlled these vital parameters to safeguard the cement manufacturers from frequent purchase of bags translating into lower operating expenses

4.Saving due to pulsing system up gradation vis-à- vis additional module integration:

Conventional approach for DP reduction is reduction in ACR which would mean increase in module size. As against this, upgrading to new pulsing system would mean savings to the tune of 80 – 85% of capital cost. In addition, there is downtime reduction and intangible saving in terms of space.


Thermax was referred for studying the possibility to control higher DP across the bag house, during change in operation of bag house fan from 810-820 RPM (Results: Case 1) to higher speed of 960-980 RPM (Results: Case 3), for improving the mill throughput.
Instead of increasing the modules in the bag house, Thermax Team has modified pulsing system to reduce the DP in higher ID fan RPM operation. The modified pulsing system was installed and observed for the DP reduction from 85 – 95 mmwg to 65 – 75 mmwg and pulse air pressure reduced from 5 – 6 kg/cm2 to 3.8 – 4.2 kg/cm2.

“We appreciate Thermax for their support for solving the DP problem and overall savings in power cost in terms of DP reduction & Compressor Air Pressure reduction,” said Mr. Narang, MyHome Cement, Hyderabad.

Authored by

Mr. Arijit Dutta

Head of Innovation and Service Business Group

Thermax Limited | Air Pollution Control

Download Case Study

Raw Mill – Kiln Application in Cement Industry


M/s. Chettinad Cement Corporation Limited (CCCL), An Indian Rs 8.5 Billion business group is into Manufacturing (Cement, Silica, Quartz, Grits) & Services (Construction, Transports, Ship Management, Clearing & Forwarding), is one of the major cement manufacturers in Southern India with total cement production capacity of 3 MTPA having manufacturing units at Puliyur, Karur and Karikkali, Dindigul in Tamil Nadu.


The rotary kiln is the heart of a cement manufacturing plant. Cement kilns have all chemical ingredients. These
ingredients are at a broad range of gas temperatures from 100° to 1650°C.
The emissions contain:

  • High concentrations of alkaline solids, including sodium and potassium oxides;
  • High concentrations of freshly created Calcium Oxide
  • Volatiles; and
  • Organic gases

At CCCL, the kiln gases are at around 900 deg C. Pyroprocessing consists of five stages. Preheater exit gases are distributed based on requirement of Vertical Roller Mills for Raw Material Grinding and Vertical Roller Mill for Coal grinding. M/s CCCL has installed gas cooling system in the Preheater down-comer to bring the outlet gas temperature to about 310 deg C. In existing GCT, this temperature is further brought down to about 220 deg C and they are polished through the Air Pollution Control Equipment.


The Plant at Puliyur, Karur was operating at a capacity of 2,800 TPD clinker production. For the operation of the Raw Mill (Vertical Roller Mill), existing system was 2-fan circuit. The existing system consisted of Gas Conditioning Tower (GCT) followed by Electrostatic Precipitator (ESP) for the control of particulate emissions from the kiln and raw mill. Since the existing circuit was designed in early 90’s for lower capacity of Kiln, CCCL wanted to look at the various alternatives to reduce the emissions going out of the stack. CCCL decided after the initial scrutiny to award the work to m/s Thermax for suggesting various alternatives to meet the above objective. After much deliberation, Thermax and CCCL jointly decided that the best solution was to design a Bag House System in series with the existing ESP, (ESP – considered as a pre-collector). The system was guaranteed to give 25 mg/nm3 outlet emission with higher plant capacity.The system was converted from 2-fan circuit to 3- fan circuit. The major challenges handled by Thermax in designing the Bag House System in series with ESP were following:

  • Handling very fine dust at the inlet for Bag House coming out after ESP
  • Handling gases with higher moisture content coming out of the existing GCT.

Like in any cement plant, the Bag House operates in two basic modes of operation:

  1. Direct Mode Of Operation – All the Preheater exit gases shall be routed directly to bag house since the raw mill is not operating
  2. Compound Mode Of Operation – Here the Raw Mill is in running condition, therefore major part of Preheater exit gases will be routed through the Raw Mill circuit( including Raw mill , ESP and ESP fan) before going through the baghouse.


The Reverse Air Bag House (RABH) was installed after ESP to handle the exit gases from Preheater / RawMill. After conducting thorough analysis on world wide similar reference installations for the suitability of filter media for achieving lower emissions, filter media / bags made up of Fibre Glass woven fabric along with Poly Tetra Fluro Ethylene (PTFE) laminate was selected for this installation. The chosen woven glass fabric posses the following characteristics:

  • PTFE laminate is a micro porous membrane which collects even sub-micron sized particles
  • It has excellent dust cake release property
  • Due to its non-stick nature, it ensures low differential pressure across the fabric
  • Also, PTFE laminate is moisture resistant and protects the woven glass fabric from effects of moisture.
  • Mainly suitable for this application because of its inert nature, compatibility with the kiln gases and the
    temperature resistance.

Bags of more than 10 meter length were used for optimum floor space usage. As an operating principle of RABH, periodically the bags are cleaned using the recirculation of the cleaned air from the outlet of the RABH. The dust collected from the bag house is transported to Silo / preheater feeding elevator.
Having rich experience & expertise of more than 25 years in product line of ESP, Thermax recommended to charge only one out of three fields of this ESP which ensured the inlet dust load of bag house up to 50 mg/Am3 (from inlet dust load of 200 gm/Am3) and also maintained the outlet dust particle size from ESP in range of 10-15 microns which is good for the agglomeration. It was decided to conduct Computational Fluid Dynamics
to analyze before hand, the fluid mechanics of gases with higher moisture content. Numerical methods and algorithms were extensively deployed to arrive at the proper and uniform distribution. CFD was used for the components at the development stage itself to optimize the effectiveness of the component before actual installation The outputs of the analysis were presented as color plots of velocities (arrow / contour) and pressure (contour) at




Thermax was able to handle this complex issue of dust emission, through its extensive knowledge base of GCT, ESP and RABH technologies under one roof with requisite knowledge of the cement manufacturing process. As always, Thermax has once again delivered as per customer’s expectations in all respects and the emission levels are less than 25 mg/Nm3!!!!!

Air cooled condensers to save water for cement units

Thermax SPX Energy Technologies Ltd, the joint venture, bagged an order for seven air cooled steam condensers from the cement conglomerate, Nuvoco Vistas Corporation (formerly Lafarge). The condensers will be installed at cement plants in Rajasthan, Chattisgarh and Jharkhand – three for waste heat recovery systems (WHRS) and four for captive power plants (CPP).

Air Cooled Condensers (ACCs) utilise ambient air for cooling – an effective alternative to the wet cooling towers used earlier by captive power plants in the cement industry. ACCs are environment friendly in many ways. They save water in water-scarce areas since no water is required for cooling. They reduce the use of chemicals for water treatment, bring down corrosion in auxiliaries, and eliminate plume, blowdown and treatment of associated discharge water. 

The scope of the project includes design, engineering, manufacturing, construction and commissioning at site as well as performance guarantee testing before handing over. The commissioning of the WHRS and CPP units will take place over the next 12 months. This is the JV’s largest order from a single customer, bagged against stiff competition.

A significant leap in the Middle East

The Power division of Thermax recently commissioned a 40 MW coal-based captive power plant for Sharjah Cement Factory, a leading cement and clinker manufacturer in the UAE. 

This is the first full-fledged EPC project to be executed by the division in the region. It comprises two CFBC boilers of 90 TPH capacity each that are capable of firing multiple varieties of coal along with a first-of-a-kind 30% wood chip firing. 

The project scope involved the supply and commissioning of Thermax DM plant, bag filters and dust extraction system along with other Balance of Plant equipment. The plant was conceptualised and synchronised within a record time of 18 months. Commencing 25th March, the plant is operating on stable load and generating power till date.

Helping a cement company in MP to generate power from waste heat

Cement plants in India are aiming for higher efficiency and profitability in their operations. One of the ways to achieve this is to use waste heat from operations for power generation. A pioneer in waste heat recovery based power plants, Thermax has begun work on a captive power plant at Maihar, Madhya Pradesh for a cement manufacturer, a group company of Birla Corporation Limited. The Rs. 98 crore project will harness waste heat of the cement plant to generate 12.25 MW power. The scope of the project includes boilers, turbine, air cool condenser, ducting, civil, electrical control and instrumentation, and other accessories. For this EPC project, Thermax will install a space-saving vertical preheater boiler. The project is expected to be commissioned by the end of 2018.

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