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Filtration: Filter bag replacement crucial for maximum life

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A properly selected filter bag in terms of its fit with cage, tubesheet and material of construction, can yield a longer life and give an good operating experience, provided the bags are installed carefully and the commissioning is done in proper manner, writes Rajendra Kumar Yadav.

The pulse jet bag filter (PJBH) is physical filtration equipment which uses filter elements made of woven/non- woven fabric to separate the suspended particulate matter from the air or from flue gases. These particulates can be dust from different processes used for manufacturing cement. PJBH is an equipment of choice for air pollution control or product recovery for various processes in a cement plant and has gained prominence over other equipment like ESP and RABH due to its high efficiency, competitive installation cost and ease in operation. Filter bags are a consumable part in the PJBH and need replacement at regular intervals to keep the equipment running smoothly and continuously.

In the last two decades of my association with air pollution control equipment, I have come across more than 1, 000 PJBH installations. Most of these installations were either non-performing or under-performing to the ever increasing expectations of the users. There are usually three major demands of the users of PJBH namely, Filtration Efficiency – The filter must not emit more than desired levels of suspended particulate matter. For a product collector, it is maximum collection of product, letting nothing out of the chimney.

Pressure Drop – The filter must run at the lowest possible pressure drop across the inlet and outlet of the filter unit. It is directly related to the power consumed/ throughput of the production equipment. The higher the DP, the more the power consumed. Similarly, the lower the DP, the more the possibility of throughput.

Life – running hours of the filter bag before it is discarded – There are two modes of the end of useful life for a filter bag. It has either lost its permeability to a level where the differential pressure drop is more than the acceptable limit or it is mechanically damaged.

Most of the users had a common observation. When they bought the unit new, the filter bags lasted longer than when they changed the filter bags. Most of the times the reasons attributed to shorter life were found to be as detailed below:

1. The duct work, filter housing and process connections develop holes over 24 or more months as they handle dust- laden gases. Normally this happens because the equipment is manufacturing using a lower thickness of the steel sheet. This results in a lot of undesirable leakage of atmospheric air at different locations. This air may cause localised cooling and condensation of the water vapour present in the flue gases, which ends up blinding the filter bags or the chemical degradation of fibres used for making these felts.

2. The cages are rusted during use with the first/previous set of bags. This results in increased roughness of the wire cage. Even when they are repainted or repaired, the roughness is not taken care of and it causes increased abrasion with the filter bag surface during each cleaning pulse, resulting in early failure.

3. Excessive pulsing of the filter bags is a very common phenomenon. Most of the units are not fitted with an on-demand kit. These units keep pulsing the filter bags at regular intervals irrespective of the pressure drop across the filters. Each filter has a flexural strength (resistance to failure due to flexing of filter materials in opposite directions) and it will fail earlier than expected if cleaned excessively. The pulsing air pressure being more than required/recommended also damages the filters prematurely.

4. The quality of the compressed air used plays its own role in a filter’s useful life. Compressed air expands from 4-5kg/cm2 to almost atmospheric pressure and all the water vapour carried in it will instantly condense. If the compressed air is not sufficiently dried before being introduced into the filter unit, it may get the filters wet and cause higher DP. It may also cause cementing/hardening of the interstitial dust, thereby blocking pores permanently.

5. Poor fitment of the filter bags with the cages is another prominent reason for early failure. This problem is more severe when brittle fibres like glass and PTFE are used for making filters. Pulsing more frequently or pulsing with higher intensity pressure results in premature failure of filter bags made of these fibres. And if the fitting is loose, the filter may fail within days. For other fibres too, loose fit results in the failure of the filter prematurely. Also, very tight fitting will result in inadequate cleaning.

6. Wrong selection of filter media for a given application results in premature failure. Some fibres offer temperature resistance, some are good against moist heat and yet others are good against abrasion. Any mismatch will result into a shorter bag life.

7. There are other faults like improper installation of bags with cages/tubesheet, improper length of filter vis-a-vis the cage. Inadequate cleaning system design, leaking rotary air lock valve, etc, are other factors that can cause premature failure of filters. Uncontrolled process parameters like flow, temperature, dust load and size of particles also impact filter life.

8. The start -up and shutdown procedures if found to be faulty will result in the process gases remaining trapped in the casing even after the process has been stopped and the water vapour/acid fumes condensed on the filter bag will causing blinding of pores or chemical degradation.

So, the question is, what do we do to extract maximum life out of the filters?

One of my overseas associate with more than 40 years experience in PJBH design, installation and commissioning, remarked that commissioning a new set of filter bags was like flying a plane. A big checklist of pre- flight activities and a smooth take- off are essential and then you can go on autopilot.

However, before we discuss the checklist we must understand a few things. What is the total number of filter bags installed in the bag filter unit? Should it be a single compartment or a multi-module bag filter? Whether it is online pulsing or offline pulsing? These are basic facts one must collect before working out any strategy.

The best strategy to change the bags in a PJBH is to change the whole set at one go. However, if changing the entire set of bags is not possible then at least 50 per cent should be changed at one time. If even that it not feasible, then all the bags in a single module must be changed. Never change a few bags in a single module of PJBH as these new bags with very high air permeability can handle the flue gases and usually fail very soon. Instead, install new bags and keep the old but good bags for a change later, in case of failure.

Once you have chosen from the above three options, what follows is:

1. Buying the filters from a reliable source. Find out correct dimensions (inner diameter * effective length) and the fitting method of the filter bag with the tubesheet. Your original equipment manufacturer (OEM) must provide you with this information. Insist on a spare parts drawing from your OEM when you are buying the PJBH.

2. Providing complete information to the vendor from whom you are buying the filters; this includes operating parameters like flow, temperature, dust load, dust type and filter life obtained from last set of bags. Concealing information or passing on wrong information only deprives you if there is any problem in your existing system. Sometimes OEMs do make mistakes in the selection of filter bags as they are not fibre technologists.

3. Seeking installation and operation procedures from the bag supplier or sharing your installation and operation procedures with them to reach a consensus. Many filter suppliers offer a warranty on filter life.

4. When the filter units are bought as composite equipment with other machineries, the focus is always on production machinery. This could result in the selection of inadequate equipment. Take advantage of a PJBH expert when you decide to change your set of bags as this is the most cost- effective time to make any modifications in the equipment.

5. Every day there are new technologies emerging in the field of fibre materials, felt manufacturing and surface treatments. They offer huge benefits over the conventional media in terms of operating pressure drops, better collection efficiency and useful life. Do enquire about these upgrades from your filter supplier.

6. Insisting on getting a sample bag from the filter manufacturer and checking it for a perfect fit with the tube sheet. If you are using a snap band type of fitting, check whether the filter can be rotated in the tube sheet using bare hands. It is not desirable to have a fitting where the bags are rotating in the tubesheet. Also check the fitting with the cage if you intend to use existing cages. Use the guidelines provided by your OEM about bagtocage fit. Ask for whatever is not provided already.

7. Checking the condition of the cage. A thorough inspection of cages can do a lot to save your filter from damage due to use of bad cages. Avoid cages which are corroded, bent, have become oval, have broken rings, have a vertical wire missing or a horizontal ring missing. Check if the top collar and bottom cup are in good condition. If it is fitted with a ventury, then the ventury must be in good shape and should not have holes. Check the wire surface and ascertain that it is not rough. Please note that often the cage is only a fraction of the cost of the filter but can damage the filter bags really fast. Act prudently, replace the cages with a new set if required.

8. Last but not the least, checking the filter bags once they arrive in bulk and obtaining the required documentation like inspection reports/ test certificates and packing lists to ensure that they are same as ordered by you in size and material of construction.

Now that the filter bags are with you, make a checklist of all you need to do when putting the filter bags in the unit. A general or specific list can be provided by your OEM /bag supplier if you ask for it. Planning the filter bag change before actually changing the filter bags helps you organise the essential resources before the unit is actually opened and saves the plant some expensive downtime. Unfortunately, most Indian industries are not in habit of changing filters during a regular shutdown but always work on a philosophy of `change when required.` Having planned and got ready your checklist, you can change the filter bags with a new set of filter bags for the entire unit or a compartment. When restarting the unit, take care to run it on partial load for a few hours before the bags have formed a primary cake on the filter surface. It usually takes about 2-12 hours for the formation of a primary cake on the filter surface. Since it is the primary cake which does most of the filtration throughout the life of filter bags, be careful that it is not formed at full load as that would be very packed and will have a higher residual pressure drop. A primary cake formed at gentle velocity is more permeable and enhances the filter’s life and lowers the operating pressure drop. You may also seek the help of a professional commissioning engineer who can help you in installation of filter bags, cages, pre-coating, pre-commissioning and actual commissioning and setting up the most efficacious cleaning cycle.

It is not only a good filter bag which gives a good useful life and trouble-free operation but the entire process of the procurement, inspection, installation and commissioning which ensures that your filters give you total value for money. Often, they are the heart of your production system and govern productivity. Environmental compliance is being implemented in a stricter manner and failure to contain emission may result in stiff penalties. The best strategy is to learn the finer aspects of filter bags change and reap benefits. There are organisations which specialise in these services and you can always avail their services.

Having worked out the most suitable strategy for changing the filter bags, you must monitor their life by recording the dates on which you changed the filter bags, when you had to induce extra cleaning and how much life you then attained. Sharing this information with your supplier will get you better results the next time you change the filters.

PJBH is increasingly being used for different applications in cement plants. The proper selection of a filter bag in terms of its fit with cage, tubesheet and material of construction can yield a longer life and give a good operating experience, provided the bags are installed carefully and the commissioning is done in a proper manner. Pre-coating the filter bags before commissioning may give good protection against condensation on them.

Rajendra Kumar Yadav, is Managing Director, Gulmohar Filtech. rajendra.yadav@gulmohargroup.com

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Economy & Market

Impactful Branding

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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.

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Concrete

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

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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.

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Concrete

NTPC selects Carbon Clean and Green Power for carbon capture facility

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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.

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