Process

Boosting Grinding Systems

Published

8 years ago

July 31, 2016

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Retrofitting of ball mills is very common to enhance grinding output. During the process, close attention has to be paid to the mill internals, the material of construction and the design aspect.

With focus on increasing productivity of existing grinding systems, modern cement plants are upgrading their mills to high throughput grinding [Ref. 1]. These upgradations or new grinding unit projects are increasingly prescribing pre-crushing of input materials using energy efficient pre-grinders (roller presses or VRMs in semi-finish mode) combined with single chamber ball mills in closed circuit with high efficiency dynamic separator to handle finish grinding.

The single chamber ball mills (mostly converted from previously available twin chamber mills) generally provide larger grinding volume and mainly drive power for high throughput finish grinding, essential to meet high Blaine requirements of additive cement. During this retrofitting exercise, not enough attention is given to optimising the ball mill internals despite significant change in granulometry and grinding characteristics of feed entering the ball mill.

Hence, when mill internals are conventionally designed based solely on ball mill operations alone without considering the changes in the complete grinding circuit, they fail to achieve optimised grinding efficiency, both physically and economically. "Aqua-Duo" shell liners supplied by Aqua Alloys Pvt Ltd are semi-classification type, thin corrugated liners specifically designed to suit grinding in high re-circulation ball mills receiving pre-ground fine material from roller press/re-circulation from separator. Apart from the basic purpose of mill shell protection, the new design ensures uniform mix of grinding media throughout the length to handle higher percentage of finer feed material, provides increased effective mill volume for higher throughput and corrugation for higher torque transmission.

Trials at different cement plants in India have provided insights into the possibility of enhancing ball mill throughput and optimisation of specific power consumption after installation of "Aqua-Duo" type shell liners and maintaining the previous percentage of media filling level. A 5 – 6 per cent increase in mill output is achieved for the same or better overall circuit specific power consumption and product quality after replacing the conventional classifying liners with custom design liners. This article describes the reasons for unconventional liner design, outlines conceptualisation of new liner design, lists the advantages over conventional liners and also summarises the results of trials at four different sites.

Justification for unconventional liner design
The following points provide insights for unconventional thinking as regard to holistic liner design considering changes taking place in modern grinding circuits. It also outlines why media segregation and hence classifying liner design (Ref. Figure 1) is not useful for finish grinding with higher degree of additives and high throughput mills.

Classifying liners are mainly designed for open circuit systems or low re-circulation closed circuit mills where the percentage of higher size material in feed is higher and media segregation was essential. The media classification concept loses its liner design advantage with mills being upgraded to handle higher throughput and higher percentage of additives, finer than clinker feed.
New mills can operate with re-circulation factor of nearly 2 to 2.5. Hence actual ball mill feed (pre-ground material from roller press circuit combined with finer reject material and additives) always has mixed granulometry. Only the higher size media near the inlet is sub-optimal for finer re-circulation material (80 per cent <200 micron) or finer additives (fly ash, slag) coming into the mill. Hence classification of media is of lesser relevance in such high re-circulation systems.
With increased production of high Blaine cement (due to higher percentage of additives) finish grinding is mainly governed by smaller size grinding media distribution (25 mm and below with 17or15 mm being the smallest size). The classification efficiency of conventional liners is severely affected due to smaller piece weight difference in these sizes.
Ball mills are designed to provide highest productivity at an average volumetric media filling of 25 to 27 per cent [Ref. 2]. Thicker classifying liners with slope profile reduce the mill effective volume and hence accommodate less grinding media charge for the same optimum loading. This limits not only the mill throughput but also the opportunity to harness additional drive loads available during retrofits.

Concept of thin, Semi-Classification, High Torque Transmission Liners
Figure 2 highlights different grinding mechanisms and media action with respect to mill % critical speed and grinding media filling. It shows how the new design contributes for higher productivity in the normal operating region of ball mills by shifting the curve down and increasing the cascading region (good for fine grinding). For the given mill (with fixed % critical speed) the overall thinner cross-section of Aqua-Duo liner design provides scope for higher media charge for same optimum volume filling level (near 25%). Additional grinding media draws higher load at better transmission efficiency (due to optimum filling level) allowing mill to handle higher throughput for same Blaine/residue improvement across the chamber. In between hump liners (used for larger media size distributions) partially contributes to media classification, though with less efficiency. If the same extra grinding media is added with conventional liners the overall mill efficiency will drop as the filling level exceeds optimum level and arm of gravity shifts towards center. The corrugated lining (specially designed to handle 17 to 30mm media) accentuates the tumbling motion increasing the attrition grinding action, The feature also provides higher friction between liner and media and line contact for grinding, enhance the torque transmission contributing more to fine particle breakage.

Field Trial Results
The new design has been implemented and tried in several single chamber cement mills with roller press as pregrinder. The overall performance is encouraging with improvements either in production or quality levels. The best performance improvements are obviously seen in the circuits with roller presses and single chamber mills. The results for four of such mills (before and after replacing the conventional classifying liners) are outlined in Table 2. All the four mill circuits had roller presses as pregrinder setup, single chamber ball mills (over 4 m ID and 25 to 15 mm media charge) in closed circuit with a dynamic separator.

Summary
Re-optimisation of mill liners is the need of the modern grinding systems design. Aqua-Duo design provides effective alternative combining mechanical and process requirements of such systems. The advantages over conventional liners are clearly seen. The field trials on large scale cement mills are positive for output, power efficiency and product quality improvements.

NOTE: Further technical data, detailed results can be shared/discussed on personal request to the author. (email: contact@aqualloys.com)

References
[1]"Innovations in Portland Cement Manufacturing", by J I Bhatty, FM Miller, SH Kosmatka, Portland Cement Association publication, 2004
[2]"Ball charge loading " Impact on specific power consumption and capacity", David S Fortsch, IEEE-IAS Cement Industry Committee, 2006.

This article has been authored by Dr Raghuraj K Rao, Aqua Alloys Pvt Ltd, Belgaum

Process

Price hikes, drop in input costs help cement industry to post positive margins: Care Ratings

Published

3 years ago

October 21, 2021

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Region-wise,the southern region comprises 35% of the total cement capacity, followed by thenorthern, eastern, western and central region comprising 20%, 18%, 14% and 13%of the capacity, respectively.

The cement industry is expected to post positive margins on decent price hikes over the months, falling raw material prices and marked drop in overall production costs, said an analysis of Care Ratings.

Wholesale and retail prices of cement have increased 11.9% and 12.4%, respectively, in the current financial year. As whole prices have remained elevated in most of the markets in the months of FY20, against the corresponding period of the previous year.

Similarly, electricity and fuel cost have declined 11.9% during 9M FY20 due to drop in crude oil prices. Logistics costs, the biggest cost for cement industry, has also dropped 7.7% (selling and distribution) as the Railways extended the benefit of exemption from busy season surcharge. Moreover, the cost of raw materials, too, declined 5.1% given the price of limestone had fallen 11.3% in the same aforementioned period, the analysis said.

According to Care Ratings, though the overall sales revenue has increased only 1.3%, against 16% growth in the year-ago period, the overall expenditure has declined 3.2% which has benefited the industry largely given the moderation in sales.

Even though FY20 has been subdued in terms of production and demand, the fall in cost of production has still supported the cement industry by clocking in positive margins, the rating agency said.

Cement demand is closely linked to the overall economic growth, particularly the housing and infrastructure sector. The cement sector will be seeing a sharp growth in volumes mainly due to increasing demand from affordable housing and other government infrastructure projects like roads, metros, airports, irrigation.

The government’s newly introduced National Infrastructure Pipeline (NIP), with its target of becoming a $5-trillion economy by 2025, is a detailed road map focused on economic revival through infrastructure development.

The NIP covers a gamut of sectors; rural and urban infrastructure and entails investments of Rs.102 lakh crore to be undertaken by the central government, state governments and the private sector. Of the total projects of the NIP, 42% are under implementation while 19% are under development, 31% are at the conceptual stage and 8% are yet to be classified.

The sectors that will be of focus will be roads, railways, power (renewable and conventional), irrigation and urban infrastructure. These sectors together account for 79% of the proposed investments in six years to 2025. Given the government’s thrust on infrastructure creation, it is likely to benefit the cement industry going forward.

Similarly, the Pradhan Mantri Awaas Yojana, aimed at providing affordable housing, will be a strong driver to lift cement demand. Prices have started correcting Q4 FY20 onwards due to revival in demand of the commodity, the agency said in its analysis.

Industry’s sales revenue has grown at a CAGR of 7.3% during FY15-19 but has grown only 1.3% in the current financial year. Tepid demand throughout the country in the first half of the year has led to the contraction of sales revenue. Fall in the total expenditure of cement firms had aided in improving the operating profit and net profit margins of the industry (OPM was 15.2 during 9M FY19 and NPM was 3.1 during 9M FY19). Interest coverage ratio, too, has improved on an overall basis (ICR was 3.3 during 9M FY19).

According to Cement Manufacturers Association, India accounts for over 8% of the overall global installed capacity. Region-wise, the southern region comprises 35% of the total cement capacity, followed by the northern, eastern, western and central region comprising 20%, 18%, 14% and 13% of the capacity, respectively.

Installed capacity of domestic cement makers has increased at a CAGR of 4.9% during FY16-20. Manufacturers have been able to maintain a capacity utilisation rate above 65% in the past quinquennium. In the current financial year due to the prolonged rains in many parts of the country, the capacity utilisation rate has fallen from 70% during FY19 to 66% currently (YTD).

Source:moneycontrol.com

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Wonder Cement shows journey of cement with new campaign

Published

3 years ago

October 21, 2021

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The campaign also marks Wonder Cement being the first ever cement brand to enter the world of IGTV…

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Cement manufacturing company Wonder Cement, has announced the launch of a digital campaign ‘Har Raah Mein Wonder Hai’. The campaign has been designed specifically to run on platforms such as Instagram, Facebook and YouTube.

#HarRaahMeinWonderHai is a one-minute video, designed and conceptualised by its digital media partner Triature Digital Marketing and Technologies Pvt Ltd. The entire journey of the cement brand from leaving the factory, going through various weather conditions and witnessing the beauty of nature and wonders through the way until it reaches the destination i.e., to the consumer is very intriguing and the brand has tried to showcase the same with the film.

Sanjay Joshi, executive director, Wonder Cement, said, "Cement as a product poses a unique marketing challenge. Most consumers will build their homes once and therefore buy cement once in a lifetime. It is critical for a cement company to connect with their consumers emotionally. As a part of our communication strategy, it is our endeavor to reach out to a large audience of this country through digital. Wonder Cement always a pioneer in digital, with the launch of our IGTV campaign #HarRahMeinWonderHai, is the first brand in the cement category to venture into this space. Through this campaign, we have captured the emotional journey of a cement bag through its own perspective and depicted what it takes to lay the foundation of one’s dreams and turn them into reality."

The story begins with a family performing the bhoomi poojan of their new plot. It is the place where they are investing their life-long earnings; and planning to build a dream house for the family and children. The family believes in the tradition of having a ‘perfect shuruaat’ (perfect beginning) for their future dream house. The video later highlights the process of construction and in sequence it is emphasising the value of ‘Perfect Shuruaat’ through the eyes of a cement bag.

Tarun Singh Chauhan, management advisor and brand consultant, Wonder Cement, said, "Our objective with this campaign was to show that the cement produced at the Wonder Cement plant speaks for itself, its quality, trust and most of all perfection. The only way this was possible was to take the perspective of a cement bag and showing its journey of perfection from beginning till the end."

According to the company, the campaign also marks Wonder Cement being the first ever cement brand to enter the world of IGTV. No other brand in this category has created content specific to the platform.

Process

In spite of company’s optimism, demand weakness in cement is seen in the 4% y-o-y drop in sales volume. (Reuters)

Published

3 years ago

October 21, 2021

admin

Cost cuts and better realizations save? the ?day ?for ?UltraTech Cement, Updated: 27 Jan 2020, Vatsala Kamat from Live Mint

Lower cost of energy and logistics helped Ebitda per tonne rise by about 29% in Q3
Premiumization of acquired brands, synergistic?operations hold promise for future profit growth Topics

UltraTech Cement
India’s largest cement producer UltraTech Cement Ltd turned out a bittersweet show in the December quarter. A sharp drop in fuel costs and higher realizations helped drive profit growth. But the inherent demand weakness was evident in the sales volumes drop during the quarter.

Better realizations during the December quarter, in spite of the 4% year-on-year volume decline, minimized the pain. Net stand-alone revenue fell by 2.6% to ?9,981.8 crore.

But as pointed out earlier, lower costs on most fronts helped profitability. The chart alongside shows the sharp drop in energy costs led by lower petcoke prices, lower fuel consumption and higher use of green power. Logistics costs, too, fell due to lower railway freight charges and synergies from the acquired assets. These savings helped offset the increase in raw material costs.

The upshot: Q3 Ebitda (earnings before interest, tax, depreciation and amortization) of about ?990 per tonne was 29% higher from a year ago. The jump in profit on a per tonne basis was more or less along expected lines, given the increase in realizations. "Besides, the reduction in net debt by about ?2,000 crore is a key positive," said Binod Modi, analyst at Reliance Securities Ltd.

Graphic by Santosh Sharma/Mint
What also impressed analysts is the nimble-footed integration of the recently merged cement assets of Nathdwara and Century, which was a concern on the Street.

Kunal Shah, analyst (institutional equities) at Yes Securities (India) Ltd, said: "The company has proved its ability of asset integration. Century’s cement assets were ramped up to 79% capacity utilization in December, even as they operated Nathdwara generating an Ebitda of ?1,500 per tonne."

Looks like the demand weakness mirrored in weak sales during the quarter was masked by the deft integration and synergies derived from these acquired assets. This drove UltraTech’s stock up by 2.6% to ?4,643 after the Q3 results were declared on Friday.

Brand transition from Century to UltraTech, which is 55% complete, is likely to touch 80% by September 2020. A report by Jefferies India Pvt. Ltd highlights that the Ebitda per tonne for premium brands is about ?5-10 higher per bag than the average (A cement bag weighs 50kg). Of course, with competition increasing in the arena, it remains to be seen how brand premiumization in the cement industry will pan out. UltraTech Cement scores well among peers here.

However, there are road bumps ahead for the cement sector and for UltraTech. Falling gross domestic product growth, fiscal slippages and lower budgetary allocation to infrastructure sector are making industry houses jittery on growth. Although UltraTech’s management is confident that cement demand is looking up, sustainability and pricing power remains a worry for the near term.