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Gearless drives for high capacity belt conveyors



Gearless drives are expanding the service range of drives of belt conveyors. When it comes to maintenance and energy efficiency, gearless drives offer many advantages over the conventional electromechanical solutions.

Belt conveyors in hard rock mining determine the development of belt conveyor components at the high end of their performance spectrum. New requirements with regard to conveyor geometries and mass flows make it necessary to think about alternative drive concepts. When it comes to drive sizes exceeding 3,500 kW per individual drive, there are no conventional electromechanical drives with electric motors and helical bevel gears. Gearless drives, like those which are state-of-the-art for mine hoists implemented in underground mining operations, allow the use of larger drive units and are increasingly being utilised to drive belt conveyors.

Individual belt conveyors in hard rock mining operations all over the world can nowadays extend over distances of up to 16.8 km and overcome height differences of up to 500 m, while normally achieving outputs of approximately 12,000 tonnes/hr.

Such belt conveyors have had a significant impact on the development of individual components. Conveyor belts with strength of up to 7,800 N/mm are still in use today. Electromechanical drives, consisting of electrical motors (wound rotor or squirrel cage motor) and helical bevel gears with a capacity of up to 3,150 kW, are currently in use in South American copper mines.

The performance limits of belt conveyors are redefined by lower ore contents and deeper deposits. Nowadays conveyors are routed through the tunnel systems such that the maximum length available is required in order to reduce the number of underground transfer stations. This leads to new requirements on the quality of the conveyor belts.

The St 10.000 with strength of 10,000 N/mm of belt width is now available.

An alternative for continuously improving belt quality with ever-increasing drives located at both ends of the conveyor is to optimise the application of drive forces on the belt. Possible alternatives include:

  • Belt on belt drives (TT drives).
  • Intermediate drives in the top strand and/or bottom strand.
  • Driven carrying rollers1.

Unfortunately it is not always possible to implement such drive concepts. For drives carrying rollers there is still no cost-effective and reliable solution. That’s why the current development projects focus on adapting conveyors with the traditional head and/or tail pulley drive systems to new challenges and demands.

Takraf GmbH is currently involved in studies that focus on a belt conveyor system that utilises belts having a strength class of St 10,000. The limits of conventional drives with helical bevel gears are exceeded with the required drive capacity of 21,000 kW per individual conveyor.

Low-speed synchronous motors, like those frequently implemented as drive solution for mine hoists in underground mining operations, do permit larger drive capacities.

As part of the above-mentioned study, a conveyor is equipped with three gearless drives, each delivering an output of 7,000 kW.

Gearless drive systems for belt conveyors

The advantages of gearless drives compared to electromechanical drives cannot only be reduced to the possibility of installing larger drive units. The curve of the motor’s efficiency in relation to the motor’s torque shows over the entire spectrum values that are above the characteristics of traditional conveyor drives with wound rotor or squirrel cage motors completed with the gears (Fig. 1).

Belt conveyors do not always work at full load over the entire period of operation. Partial load conditions and even short-term idle periods are all part of a belt conveyor’s operating regime. While asynchronous motors perform at lower efficiency levels with lower utilisation ratios, the efficiency of synchronous motors increases in this range.

The higher efficiency of synchronous motors in general and especially in the partial load range and the fact that mechanical loads are eliminated during transfer of torque lead to lower operating costs for the conveyor.

The maintenance of the gear unit including oil change intervals can be omitted just like the maintenance of the high-speed coupling.

This is of particular interest wherever maintenance processes involve considerable effort. Prime examples of this would be operating conveyors in Canada at ambient temperatures of -45¦C or conveyor systems that set up at an altitude of 4,500 m and more above sea level.

Structure of gearless conveyor drives

A synchronous motor consists of a rotor that is connected with the drive pulley shaft and a stator that rests on a foundation or a corresponding steel structure (Fig. 2).

Compared to conventional belt conveyor drives, the drive unit with gear box and asynchronous motor is replaced with a synchronous motor.

The following conditions must be taken into consideration if gearless drives are used:

  • Deflection of the drive pulley shaft at the shaft end due to the various belt tensions at the different load and operating conditions.
  • Possible settling of foundations of the stator or deformation of structural steel used to support the stator.
  • Possibility for readjusting the entire drive in case of belt misalignment during the commissioning.

A prerequisite is the need to comply with the permissible deviations in the motor’s air gap. Since the design of the motor, motor mount, drive pulley and the associated structural steel are closely tied together; Takraf GmbH has formed a cooperation agreement with ABB. This approach makes it possible to select a joint motor concept during component planning considering client specifications and conditions present at the site.

The following systems are worth considering as a motor concept:

1. Bearingless motor:

The rotor is directly connected to the drive pulley shaft (by means of a flange connection). The stator is supported separately.

2. Bearing motor:

The motor has two bearings. The stator is secured to the foundation or steel structure. A flexible coupling is used to facilitate the transfer of torque between the rotor and the drive pulley.

3. Diaphragm coupling:

Compared to the bearing motor, the motor mount on the output shaft side and the flexible coupling is replaced by a diaphragm coupling.

Bearing-less motor

The rotor is rigidly connected to the drive pulley by means of a flange connection (Fig. 3 and 4).

Compared to the standard layout, an additional criterion is necessary for dimensioning the drive pulley. The deflection of the pulley shaft at the coupling flange may not exceed the narrow tolerances that result from the permissible deviations in the air gap between the rotor and stator. That leads to drive pulley structures with large shaft diameters (Fig. 5). Since the rigidness of the stator mount determines the tolerances in the motor’s air gap to the same extent, it is necessary to offer solutions with very limited deformations that also allow a subsequent alignment of the stator during commissioning of the conveyor. Drive realignment would be necessary if a proper belt alignment could to be reached by drive pulley readjustment only.

Bearing motor For the solution previously described, motor bearings are not needed. No special coupling is required for connecting the motor to the drive pulley. A rigid flange connection is sufficient.

Unfortunately, bearingless motors also have disadvantages, such as:

  • Special drive pulley design to decrease shaft deflection.
  • The motor must be assembled on site, since the rotor first has to be connected with the pulley shaft and the stator is then moved over the rotor. This means that the motor must be disassembled again after factory assembly and completion of test run. In case of damage, the motor cannot be disconnected quickly and/or replaced with a spare drive.
  • For the load case earthquakes, it is necessary to take into consideration the large (rotor) masses at the cantilevered drive shaft end.
  • The disadvantages described here with regard to bearingless motors have led to working with ABB to design a motor with separate bearings as an alternative.

Diaphragm coupling

With regard to the bearing motor previously described, the motor and drive pulley are connected by means of a flexible coupling (Fig. 6). A gear coupling was selected as suitable transfer element for the torque being transferred and the permissible angular deviation of both shafts.

For very large motors (6,000 kW to 8,000 kW of driving power), geared couplings reach their limits. The drive concept with bearingless motors has resulted in heavy and expensive drive pulleys due to the deflection of the pulley shaft in the area of very large drives.

Based on the disadvantages of a bearingless motor, a motor concept with a bearing at motor N-end and a diaphragm coupling to connect the rotor with the drive pulley was developed.

The diaphragm coupling combines the functions of the bearing at the motor D-End and the geared coupling between rotor and the pulley (Fig. 7).

To transport the motor, a support structure will be placed on the motor frame, which secures the rotor shaft on the side with the output shaft end. This also provides the option to quickly separate the motor and the drive pulley by opening the coupling in case of an emergency.


In 2012 Takraf GmbH was awarded a contract by Chilean mine operator Codelco to deliver conveyors with 12 gearless belt drives for the worldÆs largest underground copper mine, El Teniente.

During the final construction phase of these conveyors, approximately 12,000 tonnes/hr of copper ore will be transported over a total distance of 11.5 km.

The drive motors each have an output of 2,500 kW. As a result of extensive discussions with the customer, the principle of the bearing motor was implemented specifically for this contract. The commissioning of the first motor for this project is slated for the year 2014.


Gearless drives are expanding the service range of drives of belt conveyors. Individual drives with a driving power of up to 8,000 kW are possible.

Studies on the use of gearless drives of this performance class are currently being carried out in the current projects.

When it comes to maintenance and energy efficiency, gearless drives offer advantages compared to the conventional electromechanical solutions.

The drive motor can be designed as bearingless, with bearings or with diaphragm coupling. Motor size, site conditions and customer requirements form the basis for the solution that is to be implemented.

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




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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NTPC selects Carbon Clean and Green Power for carbon capture facility




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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Sustainable Mining for the Future




ICR presents a case for responsible reporting across the mining supply chain.

The importance of mining, in times of sustainability reporting, is rising in stature. The rise of mining output is not waning but growing and the share of construction mineral ore in all of this still remains close to 50% of the entire extractive output. 

It is estimated that the global combined extractive output in mining is going to grow to 167gt in 2060, from the 2019 statistics of 92 gt. Out of this 27% is biomass, 15% is fossil fuel, 9% is metal ores and the balance is non-metallic minerals, bulk of which goes to the construction industry. While sustainability considerations would be driving most of the future growth, most notably, metals will be needed for electric storage batteries (eg. for electric cars), which require aluminium, cobalt, iron, lead, lithium, manganese and nickel but also for other relevant technologies, including those used for the production of wind turbines and solar panels; far greater amounts of metals are needed for clean energy production than the traditional energy production from fossil fuels. Thus the growth in metals for sustainability will offset the drop in extraction that would stem from growth in recycling. 

An overview of the mining sector

Mining for non-metallic minerals, from where the construction industry sources all its inputs, perhaps falls under the ASM (artisanal and small-scale mining), which has still remained labour intensive and suffers from safety issues all across, the developed world and developing, all have the similar challenges to grapple with. Efforts to increase automation, mechanisation and digitisation also come with the fair share of demands from the local community, which can hardly be neglected. While Large Scale Mining (LSM) is moving towards mechanisation and automation with minimum labour resources, the focus is increasingly shifting towards partnerships on supply chains that connect local procurement partners and the community at large to the external markets. 

One of the significant developments has been the shift towards battery-electrification of mobile equipment in the mines to the complete automation of all mining equipment with Net zero targets in focus. There are man-less mines in existence already where underground operations are being orchestrated through battery-electric equipment remotely connected through control systems. The partnerships between mining companies and the mining equipment OEMs is ensuring a smooth transition in this area that will take the use of fossil fuels in mines to a negligible proportion (mostly as consumables) in the near future. This however calls for a skills inventory crossover, that would need larger hand holding with the local government and other institutions as well as the local communities.

Sustainability in mining

The goals of sustainable development in mining would include transparency as a key theme between a large pool of actors that constitute and connect the upstream to the downstream supply chain partners (supplier, trader, smelter refiner, component producer, contract manufacturer, end user, intermediaries, agents and transporters). This would also entail collaboration with governments and across the supply chain to support a circular economy to minimise inputs to waste from the mining process and to increase the reuse, recycling and repurposing of raw materials and products to improve sustainable consumption. The traceability systems also ensure that the level of information that is shared and disclosed along the value chain. They illustrate the chain of custody, which is the sequence of stages and custodians the product is transferred to through the supply chain.

The transparency of reporting across the entire supply chain is at the core of this and this has two parts:

  • Minimise resource use and waste (use of water, energy, land and chemicals and minimise production of effluent, waste and chemicals) and also purpose waste rock
  • Incorporate life cycle thinking (extend responsible sourcing to all suppliers and collaborate to connect the consumer with sustainable raw materials).

India-centric big picture

India as a country has progressed well in SDG Reporting and Sustainable Development in the mining sector that accounts for 2.5% of the country’s GDP. Many of the key companies of the sector are SOEs. India is abundant in natural mineral resources and the country is one of the world’s main producers of iron ore and bauxite. India is the third largest producer of coal, behind the US and China. In construction related extractive minerals, India is the world’s second largest producer. Section 135 of India’s Companies Act on CSR and Regulation for large public companies to produce Business Responsibility Reports, makes it imperative for Large Mining companies (both metallic and non-metallic extractive ones) to be part of the SDG reporting, that cover diverse range of sustainability areas including GHG gas emissions, energy use, stakeholder engagement and labour and human rights. 

In 2011, the Indian Ministry of Corporate Affairs issued the National Voluntary Guidelines on the Social, Environmental and Economic Responsibilities of Business (NVGs). Building on the NVGs, a new guidance entitled the National Guidelines on Responsible Business Conduct (NGRBC) was released in 2018. The new guidance integrates the ‘Respect’ pillar of the United Nations Guiding Principles and the UN Sustainable Development Goals. 

Following other countries, India is also on the path of developing sustainability guidelines for the end-to-end supply chains in the mining sector. This will only ensure stakeholder participation for safety and sustainability in all four stages: profiling, reservation, exploration and departure. For future growth in mining, that will entail coal, iron-ore, bauxite and limestone extraction as the top four mining categories, it is an absolute necessity that focus on SDG reporting is carried through beyond the voluntary reporting mandate to encompass the aspirations of the communities and investors who would be the major beneficiaries of such initiatives. Without their blessings, the growth in these sectors would be mired by distrust and lack of transparency, which remains to be one of the dampeners for sustainable growth in mining. 

Procyon Mukherjee

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