The Indian cement industry, the second largest in the world after China, has an installed capacity of 200 million tonnes per annum. It is one of the major air polluting industries with dust emanating from 132 large plants and 365 small plants spread across India. It is also the second largest emitter of CO2 in the industrial sector. This accounts for 5% of global manmade CO2 emissions, of which 60% is from the chemical process and 40% from burning fuel. Consuming energy from fossil fuels, such as oil and coal creates carbon dioxide (CO2), the most important greenhouse gas (GHG) causing climate change. The methods employed for fugitive dust control in cement industry at the least include exhaust ventilation system and water spray system. Proper housekeeping aspects essentially include control of dust levels and keeping the surrounding areas clean and dust free.
A cement plant is usually a township located in far off places with self sustained facilities, including hospitals, residential facilities, eateries and schools. Thus, housekeeping requirements in cement plants are not just restricted to the plant area but also to the surrounding areas, the townships and other facilities spread over at least 50,000 to 100,000 acres of land.
In smaller plants, housekeeping is normally done manually while in large plants, high capacity cleaning equipment with advanced filtration systems in larger capacities are deployed to ensure proper cleaning standards.
The production of cement creates a lot of dust from quarrying to grinding, kilns and packaging; debris from spillage and airborne dust are generated frequently. Most of the plants are attached to mines from where the raw material is sourced. Housekeeping, which is more an in house affair, begins with those mines, where workers in charge of housekeeping ensure clean work area by clearing spillage constantly. Most plants observe safety and cleanliness programmes and competitions to encourage and motivate workers to maintain clean environment.
From the mines the raw material is transferred to the processing plant where it is subjected to heating and grinding in separate sections connected through conveyor belts. The finished product then goes to the packaging section before it is transported out. At every stage of processing, there is need for cleaning – there is heavy spillage of raw material and flying dust like in the grinding section; air pollution in the heating section where fossil fuel or coal is used; and spillage again of the clinker at the finishing stage. Cement plants constantly keep record of spillage recovery to ensure nothing goes to waste.
At the same time, the cement industry also holds immense promise in terms of utilizing wastes from other industries – fly ash (from the power sector), blast furnace slang (from the iron and steel industry) and phosphor-gypsum (from fertilizer plant). These are used to manufacture blended cement, without sacrificing the quality of cement. Today, about 12% of total fly ash generated in India is used by the cement industry.
The cleaning requirements of cement industry need special handling, as fine dust can stick or form a cake, causing serious health problems and also prove detrimental to the cleaning equipment and electricals, for the abrasive and fine powder could damage the machine.
The main cleaning equipment deployed at various sections is industrial vacuum cleaners that are used for cleaning elevator pits and surrounding area of packing plant. At Cement Mills, ultra heavy duty vacuum cleaner designed for continuous duty applications with high filtration efficiency and automatic filter cleaning, with pre separator for large capacity hoppers works more efficiently and has a good life. High capacity exhaust fans at different sections like Crusher, Raw Mills, Cement Mills and Packing Plant ensure good ventilation.
Says Arun Thapar of Inventa Cleantec Pvt. Ltd, “Our vacuum cleaners (with European collaboration) have options of single phase and three phase operation, highly efficient vacuum motors or vacuum turbines and provide 50 to 100 litres collection/disposal tank in epoxy painted or stainless steel finish. The performance is enhanced with cyclonic filters with extra large filtration surface in polyester. The filtration system has a patented Pulse Jet filter cleaning system which manages to maintain continuous operation and high efficiency of the filtration system and vacuuming.”
The sweeping machines required for the dusty atmosphere around the plants and roads should have large filtration. The hopper capacity can be medium size as the density of dust to be picked up is very heavy. Medium size hopper also provides good manoeuverability to diesel engine operated machines with extra inlet cleaners for the engine air filtration. It is recommended for increased life of the engine and improved performance. The sweeping machines can be provided with cabin for the driver to make it comfortable to work in the dusty and sunny environment.
A road sweeper /vacuum sweeper will be highly beneficial for any cement plant to maintain cleanliness inside the plant, housing colonies, packing areas, etc., and at mines and jetty.
Some of the special features, says Venu Madhavan of Roots Multiclean Ltd, to be evaluated for a road sweeper/vacuum sweeper for cement industrial applications will be as follows:
- Dust-free sweeping of larger area with good speed.
- Good hopper capacity with adequate hopper-weight carrying ratio to have longer life on hydraulics.
- Robust steel frame for tough environments with advanced body suspension for extremely smooth operation.
- Powerful climbing ability for 25% or more.
- Easy, comfortable handling, ideal for long shift work.
- Easy access to all major components, hydraulic testing points keep service cost down.
- Highly sealed with pre-filter system for heavy dusty applications will have longer engine life as compared to sweeper machine with automobile engine system used by some manufacturers.
The Hako/PowerBoss vacuum sweepers marketed by RMCL that are running at various cement factories have proved successful with consistent working for several decades
The Gujarat-based Ambuja Cement, now under the Holcim umbrella, deployed Tennant Dust Controlled Power Sweepers machine in 1994. It is one of the first cement companies to go mechanised. Four of the Tennant machines are now operating in three manufacturing units of Ambuja Cement. Minneapolis-based Tennant Company introduced this machine way back in 1940. It has now partnered with Godrej for distribution of its machines in India. “It controls the environment ensuring high air quality by containing debris and dust within the machine,” says Dennis Tan, General Manager-Emerging Markets.
These sweepers also have multi-stage dust control systems that trap dust of various sizes at different stages to maximise efficiency and life of the filtration system while allowing it to increase the volume of dust it can control. An improvised version of this sweeper, model S30, uses Maintenance Free PermaTM Filter and Counter Rotating Cyclonic Filters removing 90% of dust; and the balance 10% of dust is trapped by a Nano-Fibre Filter down to 0.5 microns @99% efficiency (human hair is 70-100 microns). All this is done while the Nano-Fibre Filter outlasts regular dust filter by five times. The unique weaving technology of Nano-Fibres allows dust to fall off easily compared to traditional cellulose filters.
Says Tan: “Most of the time the machine will be used to sweep outdoor areas near conveyor belts, quarries, shipping docks and some indoor places like packaging areas. Therefore, when picking a suitable piece of equipment, you need to consider their power source (a well known diesel engine is preferred with raised air-intake), the structural integrity of its frame such as the thickness of the steel and type of material of its dirt hopper (stainless steel preferred). Usually the un-laden weight of the machine tells you if it will stand up to the abuse. The filtration capability of the machine should also rank very high on the list and do look out for how efficient they are. Some have 100% of the dust going through one filter, this not only means high replacement cost, it will also mean frequent dusting during operation due to choked filter. The number of equipment required depends on the size and frequency of cleaning for each facility. As a rule of thumb, each machine should have a continuous run time per day of four to six hours. It is also wise to get references from other users for their feedback on the machine’s performance, reliability and after sales service to increase your chances of getting the best value.”
High Pressure Cleaners
Other area of concern to cement plants is washing of trucks, dumpers and loaders. Says Sunil Kapoor of Manmachine India: “Karcher High Pressure Cleaners have been deployed at different cement plants across the country. The right high pressure in cold water category would be a machine with at least 250 bar pressure and water flow of 500-1000lt/hr and in hot water, the pressure could be ranging between 150-180 bar and water flow of up to 1000lt/hr. The hot water machine also has provision of cleaning the Engine Compartment of these vehicles using steam. Karcher has a range of petrol and diesel operated High Pressure Cleaners as well which can be used where power supply is a problem.”