Concrete
Can the Cement Industry Take the Lead?
Going green on lubrication is one of the most crucial and investment-centric parameters in heavy industries. Cement manufacturing in India is equipped to take the lead in the area of sustainable production. ICR explores the possibility of cement leading the world to a greener future.
Lubrication remains a dirty word when it comes to the environmental impacts of the elements that go into lubricant-making and at the end of life but it need not be so. After all, the purpose of lubrication is to reduce energy wastes that otherwise would have ensued had lubricants not been used, resulting in wear and tear, abrasion and finally failure due to excessive vibration or breakage. Thus, lubricants are actually environmentally positive materials as they help to reduce friction, resulting in a reduction of energy consumption and increased equipment life. A properly formulated lubricant lasts longer, therefore generating less waste. However, the expectation is to extend the environmental positivity to include environmental release of emission as well. This is where the focus is slowly shifting. Lubricants today can be formulated using high-performance biobased materials and meet the more traditional definitions of environmentally friendly, such as being biodegradable, low toxicity and non-bioaccumulative.
The procurement fraternity in cement must look for ways that allow development of lubricants that would be both environmentally friendly and net positive in terms of impact, that includes scope 1, 2 and 3 emissions as well. Let us first have a look at the different types of lubricants in use in the cement industry.
Lubricants in Raw Material Conveying
Even if raw material is brought into the cement plant from a source some distance away, there will still be numerous conveyors throughout the plant.
These conveyors usually are driven by electric motors, some of which will be large due to the power required to pull the belts. The larger types have grease nipples that require infrequent greasing. There will also be greased bearings on both the drive end and non-drive end as well as on tension rolls in between.
Many different types of greases are used successfully in these applications. The specific grease employed is not as important as the frequency of the greasing, which can help to keep dust out of the races and prevent rapid wear rates. Since conveyors are often outside and open to all weather conditions, it is not uncommon to choose a water-resistant grease to inhibit water ingress. The use of greasing systems in which a centrally located reservoir feeds numerous points through piping may be considered. However, the pipe runs could potentially be quite long, requiring a number of these types of systems.
The other alternative would be a single-point grease lubricator that attaches directly to each bearing. These lubricators can be set to expel grease over variable amounts of time to suit the application and bearing size.
They can also significantly reduce the amount of labour required to individually grease the bearings as well as help to alleviate the ingress of contaminants by applying constant pressure on the bearing.
Of course, the total cost of utilising these types of lubricators throughout a plant must be
weighed against the amount of labour involved. In addition, keep in mind that these systems must be inspected on a regular schedule to ensure they are working properly. No automatic lubrication system should ever be implemented on a ‘fit and
forget’ approach.
Gearbox Lubrication (Open and Closed Type)
Conveyors typically are driven by different types of reduction gearboxes, including worm gearboxes, to allow the electric motor to sit adjacent to the conveyor and not protrude excessively. In these instances, a simple oil with the appropriate viscosity can be used. The lubricant does not necessarily need to possess extreme-pressure properties.
Gearboxes and bearings are also found in numerous crushers within the infeed section of the quarry. These components must cope with the same issues as conveyors in terms of dust. Centralised greasing systems are commonly used here, since the bearings are located close to each other, ensuring that the pipe runs are not too long and the grease reservoir can easily be housed inside. These gearboxes generally are quite large and have a substantial oil capacity. The gear teeth often experience high shock loading, so extreme-pressure gear oil is frequently used for this reason.
Crusher gearboxes benefit greatly from regular oil analysis and condition monitoring. The small oil sample required does not affect the overall oil level, and the information gained from the subsequent analysis can save a considerable amount of money in avoiding unplanned downtime and the associated costs of lost production.
There are many different types of open gears associated with cement plants, along with different lubricants and application methods. The main requirement for these open gears is that the lubricant be able to adhere for the entire revolution of the driven gear in order to offer the needed protection. This lubrication requirement occurs when the driving pinion is mating. Therefore, the best lubricants for these applications are sprayed onto the teeth just before the pinion and driven gear mate. The spray pattern is critical for the coverage of the mating teeth to be sufficient.
Normally, the lubricant is sprayed directly from a barrel due to the quantity required. The lubricant may also need a certain degree of heat resistance and must not melt away.
Lubrication Systems in Rotary Kilns
Rotary kilns have their own lubrication challenges for both bearings and gearboxes due to their slow rotation, high loads and thermal transfer of process heat. It is common for gearbox oil to be used in a circulation system utilising both heat transfer systems and filtration. The oil is often synthetic, but this is not always necessary if the flow rate is adequate and the heat transfer system is efficient. The inherent frictional properties of certain types of synthetic lubricants may be advantageous, as might the high viscosity index. However, the selection of a synthetic grease likely will be more important than the selection of a synthetic oil for the gearbox, as greased bearings will not provide the same cooling effects.
In most cement plants, slow-moving conveyors, sometimes called clinker conveyors, transport
material directly from the kilns. These conveyors typically are constructed of metal and consist
of a series of buckets that are hinged together. They are often carried by wheels on guide rails with a grease nipple in the centre. Because of the adverse operating conditions, i.e., dusty, and hot, they will require frequent greasing.
Centralised greasing systems will not work in this type of application due to the constant movement of the wheels. A system must be installed that travels with the buckets for a short distance, with greasing probes automatically projected into the grease nipple. This type of automatic system works well, but it must be checked on a regular basis because of the many moving parts and associated sensors. Although every cement plant operates differently and will have its own existing lubrication strategies, preferences, historical problems, maintenance requirements, management structure and available workforce, optimum solutions can be identified regarding the lubricants selected, the equipment used to apply those lubricants and the maintenance regime.
All of these elements can then be combined with appropriate condition monitoring techniques. By coordinating both lubrication and condition monitoring strategies with your maintenance regimes, you can ensure that your cement plant operates more efficiently and cost effectively.
Making Lubrication Systems Greener
Traditionally, when a lubricant was formulated, it contained a mixture of two main ingredients: oil and additives. For grease, a third ingredient was added—a thickener. In modern times, formulation still follows this basic mixture, but the options have expanded dramatically, as many types of natural and synthetic base fluids can be used as the base of a lubricant, not just petroleum oil. Additives are included to impart beneficial performance attributes, such as reduced friction (wear prevention), corrosion protection, heat removal (oxidation resistance), foam and air release, and water separation or emulsion, just to name a few.
There are four key areas that formulators must consider when formulating products: environmental, performance, physical and commercial. The primary lubricant attribute desired by most end users is protection of assets from wear, increasing reliability and useful lifespan. For many regulators, the primary concern is that the lubricant be environmentally friendly. For these agencies, lubricating properties are secondary, if considered at all. But lubricants can be green in many ways that still consider performance, more in line with companies’ aims in pursuit of sustainability.
The traditional environmental lubricant has either been proven to be biodegradable or formulated from biobased materials. Yet, from a more holistic standpoint, lubricants have been environmentally friendly in another way for years. If the proper product is chosen for a given application, it can improve equipment efficiency. As compared to the lubricants even 50 years ago, today’s lubricants can be formulated to provide a much higher level of equipment protection and performance. If the sustainability model of green is considered, they can be more environmentally friendly, provide better performance and improve the economic bottom line.
Ways to Make Lubricants Green
Crude oil has long been thought of as a non-renewable natural resource. Petroleum oil took millions of years to form in the ground. Renewable products grow, are harvested and turned into products within a relatively short time. Most oils taken directly from animal and vegetable sources do not yield stable lubricants. It is this instability that makes them highly biodegradable, an environmental advantage. Much research has been conducted on renewable oils since the late 1980s through genetic modifications and chemical processing, and some of their insufficiencies are being overcome. Unfortunately, this usually
results in base fluids that can be more expensive than mineral oils.
Early environmentally acceptable lubricants were made from biobased materials or were biodegradable, most formulated using vegetable oil-based fluids. Concessions often had to be made by the users when putting these products into service. They typically become jelly-like at low temperatures and oxidised rapidly at operating temperatures. They were also more expensive. This meant that for a user to employ green lubricants, they had to pay more for a product that didn’t perform as well. There were not many laws in place forcing users to buy them, so only hardcore environmentalists used them. Governments are beginning to put more emphasis on environmentally acceptable lubricants (EALs) by enacting laws making it more difficult for companies to avoid using them. Fortunately, many options are available today through genetically improved vegetable oils or high-performance synthetic fluids, so that higher performing products can be formulated to overcome the low- and high-temperature concerns of the early products. Along with biodegradability, toxicology has become part of the requirement for a lubricant to be green, meaning that formulators now must also consider ecotoxicity and bioaccumulation.
Any effort to reuse or recycle lubricants is green. Some lubricant packaging, such as steel drums and bulk transfer tanks, can be emptied, sent back, refurbished and refilled with new lubricants or other chemicals. Most lubricants, however, cannot be reused because of degradation and contamination, though some end users have tried with limited success. For example, used lubricants are sometimes applied to moving chains. This is not considered a best lubrication practice, but success varies depending upon the condition of the used lubricant. Another reuse for lubricants is that they are collected and burned as heating fuel oil. The fuel is needed as an energy source, so this approach is greener than dumping into a landfill or pouring into the environment.
An entire new segment of the lubricants industry exists called re-refiners. In the infancy of re-refining, waste oil collectors took spent lubricant back to their facility, removed the water, filtered out the solids, and resold it for various lubrication uses. Modern re-refiners do the same, but then, unlike their predecessors, they introduce it into a refinery process just like crude oil. After processing, new high-quality base oils are produced that have been found to be of equal or better quality to virgin base oils. These can be used to produce new lubricants, restarting the closed-loop process.
-Procyon Mukherjee
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