Product development

Advanced fuel burning technologies in cement production

Published

3 years ago

October 19, 2021

admin

In the recent climate summit at Paris, the cement sector has backed a plan to shift toward the use of de-carbonisation technologies. Notwithstanding to the commitment given over there in the summit, use of waste materials as fuel is a very significant step to reduce consumption of fossil fuels and it is going to increase in our country in the coming years. Prof JD Bapat takes stock of the design of the burners for effective use of waste or alternate fuels with less gaseous pollution.

The high cost of energy has increased focus on energy efficiency in cement production. The concern for GHG emission has lead to greater preparedness for increased utilisation of alternative fuels in the Indian cement industry. The modern multi-channel burners satisfy both the requirements of energy efficiency and GHG reduction. While the modern cement plants have multi-channel burners, the older plants are gradually shifting from uni-flow (or mono-channel) burners to multi-channel burners.

The alternative fuel utilisation is still low in India. The average thermal substitution rate (TSR) is less than 1 per cent. The multi-channel burners effectively manage the variety and complexity of alternative fuel burning. Compared to a conventional burner, modern multi-channel burner offers much better possibilities for flame shape control, high momentum and the flexibility to use different types of fuels, such as hazardous chemicals or solid biomass. The advanced burners reduce the loss in production during kiln disturbances and also reduce NOx in the burning zone as the primary air ratio is low. The NOx emissions can be reduced as much as 30-35 per cent over emissions from a typical direct fired, uni-flow burner. Better flame properties with the multi-channel burner improve combustion efficiency and eliminate flame impingement on refractory.

While multi-channel burners are becoming increasingly common in the Indian cement industry today, they might need further innovation and better design to suit the requirements of an increased TSR of 30 per cent or more; latest research on plasma burners, for example. The anticipated benefits with advanced burning technologies are: thermal savings: 3 to 5 kcal/kg clinker, electrical savings: 0 to 0.5 kWh/t clinker and CO2 reduction: 2 to 4 kg/t cement.

Modern Burners
The Fig 1 and Fig 2 illustrate the combustion air flow and its distribution in a cement kiln burner. Primary air is defined as air passing through the burner. It consists of axial-air, radial-air and fuel-conveying air. The percentage of primary air in the required combustion-air is called primary air ratio. Low heat value of fuel increases fuel consumption and the requirement of air for combustion. The effective air for combustion is composed of primary air, hot secondary air from the clinker cooler (supplied through the rotary kiln hood) and false air infiltrating through openings and sealing. Almost all equipment installed for surveillance or operational purposes give rise to false air. Primary air should be low and false air completely avoided, from thermal efficiency point of view. Excess air (above the stoichiometric requirement, expressed as ratio) is required to ensure complete combustion. A high excess air ratio reduces the energy efficiency and the increased exhaust gas amounts may limit the production capacity.

Evolution of modern burner
The purpose of the rotary kiln burner is to produce flame to provide the thermal energy to the raw materials enabling a temperature increase from about 900 to 1,450 ?C, to facilitate liquid phase formation and clinkerisation reactions, in the burning zone. The ideal characteristics of the rotary kiln burner are: (a) to provide a short, narrow, highly radiant flame to enable efficient heat transfer to the clinker bed, (b) to ensure complete burning of solid fuels while suspended in the flame, (c) to produce minimum of CO and NOx, (d) to ensure a stable coating formation in the burning zone, (e) to operate with a minimum of primary and transport air, (f) to operate with a minimum of excess air and (g) to be able to handle a flexible choice of both conventional fossil fuels and alternative fuels.

The flame properties are of importance for the clinker quality and for the pyro-system stability and efficiency. Inefficient heat transfer to the clinker bed can result in high amounts of free lime in the clinker, hence lower alite (C3S) content and a lower strength of the cement product. Long, high temperature flame may cause unwanted crystal growth of the clinker minerals which reduces the clinker grindability and increases the energy consumption for grinding. Too wide flame can cause impingement on the clinker bed increasing sulphur evaporation and flame impingement on the kiln walls may lead to coating breakdown which may shorten the lifetime of the kiln refractory. The modern rotary kiln burner has evolved through several stages; the Fig 3 gives a summary illustration.

Burner design parameters
The burner momentum (Ia, N/MW) describes how well the hot secondary air, at about 100, is mixed with the cold (ambient) primary air. The primary air is added to the process at high pressure and velocity (150 to 250 m/s). There is a difference between radial and axial momentum but when momentum is mentioned it normally refers to the total momentum. The most useful and easiest definition for the momentum includes the product of primary air mass flow (ma, kg/s) and velocity (va, m/s) at the burner tip, divided by the thermal energy input (H, MW).

Ia = ma . va / H
The thermal energy (H) input from burner for kiln capacity of 3,000 to 12,000 t/d ranges between 63 to 250 MW (5.4 to 21.5×107 kcal/h). The lower and upper limits may vary substantially depending upon the burner design and efficiency. A typical 1,200 t/d rotary kiln, burning mineral coal, required burner momentum of 6 N/MW, which was increased to 10 N/MW, to burn plastic pellets.

The momentum formula is useful and makes it possible to compare different burners. Higher momentum is not always better; it is necessary to find optimum momentum.

Keeping the burning zone in the right temperature range and maintaining the flame position is crucial and requires a high burner momentum, adapted to the conditions in the kiln system. High burner momentum has several advantages:

Stable kiln operation and improved fuel efficiency
Short burning zone and improved clinker reactivity
Consistent clinker granulometry leads to efficient cooler operation
Low volatility and recirculation of sulphur leading to overall improvement of the kiln condition
Decreased tendency to form build-ups and rings
Increased kiln capacity due to better operation

Burning alternative fuels
The introduction of alternative fuels may influence emissions, cement product quality, process stability and process efficiency. Worldwide the alternative fuel usage in cement production in 2010 constituted about 12.5 per cent of the thermal energy of which about 77 per cent was from waste derived fuels and 23 per cent is from biomass. In some European countries, the alternative fuel substitution in the calciner unit has reached close to 100 per cent.

In some cement plants, the alternative fuel firing also takes place at the rotary kiln materials inlet-end or at a mid-kiln position or in a separate combustion unit where large-size solid fuel is injected, substituting a fraction of the calciner firing.

Challenges and solutions for alternative fuel firing
Alternative fuels may differ from conventional fossil fuels in combustion behavior, due to differences in physical and chemical properties and reaction kinetics.

Particle size and moisture content: Alternative fuels are ground coarser, to save the cost of comminution. While solid fossil fuel (mineral coal) introduced in the burner typically has a size of 5 per cent retained on 90 micron sieve, ground alternative fuels may have size ranging in millimeters. Dried sewage sludge and municipal solid waste may be available with moisture contents from a few to more than 50 per cent mass percentage. Large local and seasonal variations may also occur. Excess air ratio and applying Oxygen enrichment is required for full conversion of the large fuel particles.

Circulation of chlorine and sulphur compounds in pyro-system: Alternative fuels may contain high proportion of chloride and sulphur compounds, which get volatilised at high kiln temperature. Installing kiln bypass is commonly applied to reduce the process challenges related to volatile circulation in the pyrosystem. The bypass for kiln gases is located immediately after the kiln gas outlet and acts as a valve. The extracted gas is quenched to condense the chlorine compounds and to a lesser extent sulphur compounds. The dust may be reused in the cement production or may require disposal. Bypass increases the specific energy consumption by 1.5 to 3 kcal/kg clinker per percentage removal of kiln gas. Typically up to 15 per cent kiln gas may be bypassed to obtain an effective chloride removal, whereas sulphur removal may require higher exhaust gas amounts removed and will require subsequent scrubbing to avoid SO2 emissions.

Conclusions
1.The multi-channel burners effectively manage the variety and complexity of alternative fuel burning. The anticipated benefits with advanced burning technologies are: thermal savings: 3 to 5 kcal/kg clinker, electrical savings: 0 to 0.5 kWh/t clinker and CO2 reduction: 2 to 4 kg/t cement
2.Keeping the burning zone in the right temperature range and maintaining the flame position is crucial and requires a high burner momentum, adapted to the conditions in the kiln system.
3.In some cement plants, the alternative fuel firing also takes place at the rotary kiln materials inlet-end or at a mid-kiln position or in a separate combustion unit where large-size solid fuel is injected, substituting a fraction of the calciner firing.
4.The most important challenges of alternate fuel firing are: particle size and moisture content, circulation of chlorine and sulphur compounds in pyro-system.

References

Existing and Potential Technologies for Carbon Emissions Reductions in the Indian Cement Industry, Cement Sustainability Initiative (CSI), World Business Council for Sustainable Development (WBCSD), January 2013
European Cement Research Academy (ECRA) Newsletter, 2/2010
Gronwall, F., ?Optimization of Burner Kiln 7, Cementa Slite?, SLU, Swedish University of Agricultural Sciences, Department of Energy and Technology, Uppsala 2010
?Combustion of solid alternative fuels in the cement kiln burner?, Linda Kaare Norskov, Industrial PhD thesis, Department of Chemical and Biochemical Engineering, Technical University of Denmark (DTU)

Fig 2: Typical combustion-air distribution

Effective combustion-air
Required combustion-air 100%	Excess air10%	False air 1%
Primary air 12-14%	Secondary air 96-98%	False air 1%

Economy & Market

Impactful Branding

Published

1 year ago

July 17, 2023

admin

Advertising or branding is never about driving sales. It’s about creating brand awareness and recall. It’s about conveying the core values of your brand to your consumers. In this context, why is branding important for cement companies? As far as the customers are concerned cement is simply cement. It is precisely for this reason that branding, marketing and advertising of cement becomes crucial. Since the customer is unable to differentiate between the shades of grey, the onus of creating this awareness is carried by the brands. That explains the heavy marketing budgets, celebrity-centric commercials, emotion-invoking taglines and campaigns enunciating the many benefits of their offerings.
Marketing strategies of cement companies have undergone gradual transformation owing to the change in consumer behaviour. While TV commercials are high on humour and emotions to establish a fast connect with the customer, social media campaigns are focussed more on capturing the consumer’s attention in an over-crowded virtual world. Branding for cement companies has become a holistic growth strategy with quantifiable results. This has made brands opt for a mix package of traditional and new-age tools, such as social media. However, the hero of every marketing communication is the message, which encapsulates the unique selling points of the product. That after all is crux of the matter here.
While cement companies are effectively using marketing tools to reach out to the consumers, they need to strengthen the four Cs of the branding process – Consumer, Cost, Communication and Convenience. Putting up the right message, at the right time and at the right place for the right kind of customer demographic is of utmost importance in the long run. It is precisely for this reason that regional players are likely to have an upper hand as they rely on local language and cultural references to drive home the point. But modern marketing and branding domain is exponentially growing and it would be an interesting exercise to tabulate and analyse its impact on branding for cement.

Concrete

Indian cement industry is well known for its energy and natural resource efficiency

Published

2 years ago

November 18, 2022

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Dr Hitesh Sukhwal, Deputy General Manager – Environment, Udaipur Cement Works Limited (UCWL) takes us through the multifaceted efforts that the company has undertaken to keep emissions in check with the use of alternative sources of energy and carbon capture technology.

Tell us about the policies of your organisation for the betterment of the environment.
Caring for people is one of the core values of our JK Lakshmi Cement Limited. We strongly believe that we all together can make a difference. In all our units, we have taken measures to reduce carbon footprint, emissions and minimise the use of natural resources. Climate change and sustainable development are major global concerns. As a responsible corporate, we are committed with and doing consistent effort small or big to preserve and enrich the environment in and around our area of operations.
As far as environmental policies are concerned, we are committed to comply with all applicable laws, standards and regulations of regulatory bodies pertaining to the environment. We are consistently making efforts to integrate the environmental concerns into the mainstream of the operations. We are giving thrust upon natural resource conservation like limestone, gypsum, water and energy. We are utilising different kinds of alternative fuels and raw materials. Awareness among the employees and local people on environmental concerns is an integral part of our company. We are adopting best environmental practices aligned with sustainable development goals.
Udaipur Cement Works Limited is a subsidiary of the JK Lakshmi Cement Limited. Since its inception, the company is committed towards boosting sustainability through adopting the latest art of technology designs, resource efficient equipment and various in-house innovations. We are giving thrust upon renewable and clean energy sources for our cement manufacturing. Solar Power and Waste Heat Recovery based power are our key ingredients for total power mix.

What impact does cement production have on the environment? Elaborate the major areas affected.
The major environmental concern areas during cement production are air emissions through point and nonpoint sources due to plant operation and emissions from mining operation, from material transport, carbon emissions through process, transit, noise pollution, vibration during mining, natural resource depletion, loss of biodiversity and change in landscape.
India is the second largest cement producer in the world. The Indian cement industry is well known for its energy and natural resource efficiency worldwide. The Indian cement industry is a frontrunner for implementing significant technology measures to ensure a greener future.
The cement industry is an energy intensive and significant contributor to climate change. Cement production contributes greenhouse gases directly and indirectly into the atmosphere through calcination and use of fossil fuels in an energy form. The industry believes in a circular economy by utilising alternative fuels for making cement. Cement companies are focusing on major areas of energy efficiency by adoption of technology measures, clinker substitution by alternative raw material for cement making, alternative fuels and green and clean energy resources. These all efforts are being done towards environment protection and sustainable future.
Nowadays, almost all cement units have a dry manufacturing process for cement production, only a few exceptions where wet manufacturing processes are in operation. In the dry manufacturing process, water is used only for the purpose of machinery cooling, which is recirculated in a closed loop, thus, no polluted water is generated during the dry manufacturing process.
We should also accept the fact that modern life is impossible without cement. However, through state-of-the-art technology and innovations, it is possible to mitigate all kinds of pollution without harm to the environment and human beings.

Tell us about the impact blended cement creates on the environment and emission rate.
Our country started cement production in 1914. However, it was introduced in the year 1904 at a small scale, earlier. Initially, the manufacturing of cement was only for Ordinary Portland Cement (OPC). In the 1980s, the production of blended cement was introduced by replacing fly ash and blast furnace slag. The production of blended cement increased in the growth period and crossed the 50 per cent in the year 2004.
The manufacturing of blended cement results in substantial savings in the thermal and electrical energy consumption as well as saving of natural resources. The overall consumption of raw materials, fossil fuel such as coal, efficient burning and state-of-the-art technology in cement plants have resulted in the gradual reduction of emission of carbon dioxide (CO2). Later, the production of blended cement was increased in manifolds.
If we think about the growth of blended cement in the past few decades, we can understand how much quantity of , (fly ash and slag) consumed and saved natural resources like limestone and fossil fuel, which were anyhow disposed of and harmed the environment. This is the reason it is called green cement. Reduction in the clinker to cement ratio has the second highest emission reduction potential i.e., 37 per cent. The low carbon roadmap for cement industries can be achieved from blended cement. Portland Pozzolana Cement (PPC), Portland Slag Cement (PSC) and Composite Cement are already approved by the National Agency BIS.
As far as kilogram CO2 per ton of cement emission concerns, Portland Slag Cement (PSC) has a larger potential, other than PPC, Composite Cement etc. for carbon emission reduction. BIS approved 60 per cent slag and 35 per cent clinker in composition of PSC. Thus, clinker per centage is quite less in PSC composition compared to other blended cement. The manufacturing of blended cement directly reduces thermal and process emissions, which contribute high in overall emissions from the cement industry, and this cannot be addressed through adoption of energy efficiency measures.
In the coming times, the cement industry must relook for other blended cement options to achieve a low carbon emissions road map. In near future, availability of fly ash and slag in terms of quality and quantity will be reduced due to various government schemes for low carbon initiatives viz. enhance renewable energy sources, waste to energy plants etc.
Further, it is required to increase awareness among consumers, like individual home builders or large infrastructure projects, to adopt greener alternatives viz. PPC and PSC for more sustainable
resource utilisation.

What are the decarbonising efforts taken by your organisation?
India is the world’s second largest cement producer. Rapid growth of big infrastructure, low-cost housing (Pradhan Mantri Awas Yojna), smart cities project and urbanisation will create cement demand in future. Being an energy intensive industry, we are also focusing upon alternative and renewable energy sources for long-term sustainable business growth for cement production.
Presently, our focus is to improve efficiency of zero carbon electricity generation technology such as waste heat recovery power through process optimisation and by adopting technological innovations in WHR power systems. We are also increasing our capacity for WHR based power and solar power in the near future. Right now, we are sourcing about 50 per cent of our power requirement from clean and renewable energy sources i.e., zero carbon electricity generation technology. Usage of alternative fuel during co-processing in the cement manufacturing process is a viable and sustainable option. In our unit, we are utilising alternative raw material and fuel for reducing carbon emissions. We are also looking forward to green logistics for our product transport in nearby areas.
By reducing clinker – cement ratio, increasing production of PPC and PSC cement, utilisation of alternative raw materials like synthetic gypsum/chemical gypsum, Jarosite generated from other process industries, we can reduce carbon emissions from cement manufacturing process. Further, we are looking forward to generating onsite fossil free electricity generation facilities by increasing the capacity of WHR based power and ground mounted solar energy plants.
We can say energy is the prime requirement of the cement industry and renewable energy is one of the major sources, which provides an opportunity to make a clean, safe and infinite source of power which is affordable for the cement industry.

What are the current programmes run by your organisation for re-building the environment and reducing pollution?
We are working in different ways for environmental aspects. As I said, we strongly believe that we all together can make a difference. We focus on every environmental aspect directly / indirectly related to our operation and surroundings.
If we talk about air pollution in operation, every section of the operational unit is well equipped with state-of-the-art technology-based air pollution control equipment (BagHouse and ESP) to mitigate the dust pollution beyond the compliance standard. We use high class standard PTFE glass fibre filter bags in our bag houses. UCWL has installed the DeNOx system (SNCR) for abatement of NOx pollution within norms. The company has installed a 6 MW capacity Waste Heat Recovery based power plant that utilises waste heat of kiln i.e., green and clean energy source. Also, installed a 14.6 MW capacity solar power system in the form of a renewable energy source.
All material transfer points are equipped with a dust extraction system. Material is stored under a covered shed to avoid secondary fugitive dust emission sources. Finished product is stored in silos. Water spraying system are mounted with material handling point. Road vacuum sweeping machine deployed for housekeeping of paved area.
In mining, have deployed wet drill machine for drilling bore holes. Controlled blasting is carried out with optimum charge using Air Decking Technique with wooden spacers and non-electric detonator (NONEL) for control of noise, fly rock, vibration, and dust emission. No secondary blasting is being done. The boulders are broken by hydraulic rock breaker. Moreover, instead of road transport, we installed Overland Belt Conveying system for crushed limestone transport from mine lease area to cement plant. Thus omit an insignificant amount of greenhouse gas emissions due to material transport, which is otherwise emitted from combustion of fossil fuel in the transport system. All point emission sources (stacks) are well equipped with online continuous emission monitoring system (OCEMS) for measuring parameters like PM, SO2 and NOx for 24×7. OCEMS data are interfaced with SPCB and CPCB servers.
The company has done considerable work upon water conservation and certified at 2.76 times water positive. We installed a digital water flow metre for each abstraction point and digital ground water level recorder for measuring ground water level 24×7. All digital metres and level recorders are monitored by an in-house designed IoT based dashboard. Through this live dashboard, we can assess the impact of rainwater harvesting (RWH) and ground water monitoring.
All points of domestic sewage are well connected with Sewage Treatment Plant (STP) and treated water is being utilised in industrial cooling purposes, green belt development and in dust suppression. Effluent Treatment Plant (ETP) installed for mine’s workshop. Treated water is reused in washing activity. The unit maintains Zero Liquid Discharge (ZLD).
Our unit has done extensive plantations of native and pollution tolerant species in industrial premises and mine lease areas. Moreover, we are not confined to our industrial boundary for plantation. We organised seedling distribution camps in our surrounding areas. We involve our stakeholders, too, for our plantation drive. UCWL has also extended its services under Corporate Social Responsibility for betterment of the environment in its surrounding. We conduct awareness programs for employees and stakeholders. We have banned Single Use Plastic (SUP) in our premises. In our industrial township, we have implemented a solid waste management system for our all households, guest house and bachelor hostel. A complete process of segregated waste (dry and wet) door to door collection systems is well established.

Tell us about the efforts taken by your organisation to better the environment in and around the manufacturing unit.
UCWL has invested capital in various environmental management and protection projects like installed DeNOx (SNCR) system, strengthening green belt development in and out of industrial premises, installed high class pollution control equipment, ground-mounted solar power plant etc.
The company has taken up various energy conservation projects like, installed VFD to reduce power consumption, improve efficiency of WHR power generation by installing additional economiser tubes and AI-based process optimisation systems. Further, we are going to increase WHR power generation capacity under our upcoming expansion project. UCWL promotes rainwater harvesting for augmentation of the ground water resource. Various scientifically based WHR structures are installed in plant premises and mine lease areas. About 80 per cent of present water requirement is being fulfilled by harvested rainwater sourced from Mine’s Pit. We are also looking forward towards green transport (CNG/LNG based), which will drastically reduce carbon footprint.
We are proud to say that JK Lakshmi Cement Limited has a strong leadership and vision for developing an eco-conscious and sustainable role model of our cement business. The company was a pioneer among cement industries of India, which had installed the DeNOx (SNCR) system in its cement plant.

Concrete

NTPC selects Carbon Clean and Green Power for carbon capture facility

Published

2 years ago

October 12, 2022

admin

Carbon Clean and Green Power International Pvt. Ltd has been chosen by NTPC Energy Technology Research Alliance (NETRA) to establish the carbon capture facility at NTPC Vindhyachal. This facility, which will use a modified tertiary amine to absorb CO2 from the power plant’s flue gas, is intended to capture 20 tonnes of CO2) per day. A catalytic hydrogenation method will eventually be used to mix the CO2 with hydrogen to create 10 tonnes of methanol each day. For NTPC, capturing CO2 from coal-fired power plant flue gas and turning it into methanol is a key area that has the potential to open up new business prospects and revenue streams.