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.
Vacuum Cleaners
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.”
Road Sweepers
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
Systems adopted globally
Two issues determine the size and capacity of the vacuuming machine: one, the area susceptible to spillage, either spread over large areas or concentrated areas and second, the amount of spillage to be collected at a time. Hence, the system varies from plant to plant.
Says Sumeet Khurana of Dulevo India: “In most cement plants in India, spillage is being removed manually by contract labourers who physically pick up spillages on tractor trolleys and then carry it to the collection unit. Spillage in the initial stage of manufacturing may not be that important to some cement industries as in the later processes like in the crushing area of the quarry, under the conveyor belt, storage and milling areas of the heating section, clinker crusher in the grinding section and in the packaging area.
“There is heavy spillage as
“In the larger units, since the entire cement processing system extend to several meters with the conveyor belts running over half a kilometre, it is necessary to have a flexible vacuuming system. These flexible systems can run on diesel engine tractor or truck that can move easily from one area of the plant to another. This machine will play the role of collection by way of vacuuming.”
This solution from Sibilia is most suitable for heavy engineering plants. Dulevo India is distributor for Sibilia machines in India.
Further, it should be suitably designed. “Many sweeping machines use water spray for sweeping and such machines are not suitable for industries like cement or steel where water creates a problem. If water is sprayed, it cannot pick up cement as it will harden. Hence the sweeping machine should have special high filtration systems that are designed to handle fine dust without the use of water.
Further, the sweeping machines should also be so designed that its engines are well protected, as working in such high levels of dust, the engine could give way in just three months. Thus, sweeping machines applied for municipal use are much different from those designed specially for the cement or steel industry.”
The Dulevo machines are deployed in the Rajasthan plant of JK White cement and in four plants of Dalmia Cement.
Combating Challenges
The cement industry is continuously adopting upgraded technology to meet better cleanliness and standards. Most of the cement industries today are making serious efforts to minimise pollution and its effect on the environment by installing equipment at various processing stages.
Air pollution
- To reduce dust emission and arrest the dust, most of the companies have Dust Collectors and ESPs at raw mill, coal mill, clinker cooler and cement mill. High efficiency pulse jet dust collectors have been installed in place of old shaking type bag dust collector in different sections of the plant including the crusher, raw mills, cement mills and packing plant.
- To ensure smokeless chimneys in cement mills, manufacturers are installing Reverse Air Bag House replacing the stacks of Bag houses, by which emission can be completely controlled.
- Another area is the clinker cooler, where Electro Static Precipitator can be installed.
- Dust collectors, the insertable type, at the transfer points of limestone belt and coal belt conveyors helps arrest dust emission during transfer of material from one belt to another.
- Water spray arrangements over the hoppers of primary crusher and secondary crusher, multiple limestone belts and clinker belt control fugitive emission generated locally.
- Sprinklers on the roads inside the plant help minimize the fugitive emission generated due to movement of vehicles.
Depletion of natural resources
Earlier, some plants were using Chemical Gypsum, a waste product from the fertilizer plant, in place of mineral gypsum. Now, to produce Portland Pozzolana Cement, using fly ash (waste from thermal power plants) is common with many cement plants. Portland Slag Cement is produced using blast furnace slag, a waste product from steel plants.
Priority is given to production of blended cement over ordinary or high grade Portland Cement using maximum quantities of fly ash and slag, thus resulting in power saving, mineral conservation and coal saving. At the
same time, it helps other industries (viz. fertilizer plants, thermal power plants & steel plants) to reduce the environmental pollution.
The entire quantity of fly ash generated in some of the captive thermal power plants is conveyed through dense phase conveying system to the plant for cement production.
To further promote the fly ash consumption, many companies have installed a dry fly ash handling system to unload fly ash from closed tankers directly to the steel hopper without generating any dust in the environment. This ensures totally dust free handling of fly ash in the plant.
Green house gas
Cement making is highly energy intensive and is closely coupled with global warming mainly due to its process characteristics that involves burning of fossil fuel besides high electrical energy consumption. Cement manufacturing process creates CO2 in two ways, one during dissociation of carbonates of limestone and second from burning of large quantities of fossil fuel inside the kiln to generate heat, necessary for calcinations of raw material and clinker formation.
Mechanised cleaning at Ambuja Cement
Scope for cleaning in Cement Industry
All floors and roads require daily cleaning / sweeping. When there is heavy wind malfunctioning of any equipment, the cleaning of surrounding area is a challenging job.
In a plant, the areas to be clean are limestone crushing section, raw mill, kiln section, coal mill, cement mill, packing plant, CCR building, bulk loading area, personnel department area and inside road. Outside the plant, the areas include, the street from the main highway to the plant, and the colony. About 60,000 sq. mt and 36,000 sq. mt of the plants area and 23,000 sq. mt of the port terminal is covered by road sweeping machines.
Tennant machines at Ambuja Cement
We have four of the Tennant 800D machines in three of the cement manufacturing units, Hako machine for the Muldwarka port terminal and TPS VAC 750 D road sweeping machine for the outside main road and mines.
Housekeeping is managed by the civil department. There are 15 contract workers for operating Tennat and TPS machines in two shifts.
The general air pollution is controlled by providing baghouse, ESP and bagfilter.
Eco-friendly practices…
Of the several initiatives taken by Ambuja Cement to adopt eco-friendly practices, one of them is using biomass at its captive power plant. The plant is presently using 24 types of biomass collected from villages of Ropar, Ludhiana, Hoshiarpur, Phagwara, Fatehgarh Sahib, Patiala and other districts. It includes biomass, rice husk, cow dung cakes, sunflower stems, maize cobs, sugar mills waste, etc.
Use of biomass has brought respite for villagers around, who find it difficult to manage agriculture waste and stock it.
Ambuja started using biomass for its captive plant in 2004. During four months of 2005, the plant drew 100% power from the biomass and utilised around 75,000 tonnes of biomass. The company aims at replicating this model at its other plants in the country as well.
Vallabh Tank Head-Works Ambuja Cement, Kodinar