Iron and steelmaking applications use a greater quantity of lime than any other market. Lime is principally used for removing impurities in both the basic oxygen process and electric arc furnaces. Dolime is also used in steelmaking as a repair material for the refractories used in steel furnaces and manufacturing equipment.
The manufacture of glass products including float glass, container glass, glass fibre filaments, fibreglass insulation and technical glass all require lime products. Dolime and lime are also used in glass manufacturing often as fluxing and stabilising additions. The use of lime and dolime improves the efficiency of glass furnaces and are used to provide desired qualities in glass products. Technical glass includes special products for phone and computer screens, glass for lamps and bulbs, laboratory glass containers and equipment as well as optical glass and high temperature cookware and oven glass.
The production of paper pulp in a process known as the Kraft (Sulfate) process uses lime to recover caustic soda from sodium carbonate that generates calcium carbonate and caustic soda. Lime is also the basis of the production of Precipitated Calcium Carbonate (PCC) which is used as a technical filler in paper production to deliver enhanced appearance and usability characteristics, including printability and texture in paper coatings.
Plastics and rubber, as well as other polymer products use lime a desiccant and additive to improve production characteristics and aspects including appearance of the final products. In addition other products manufactured with lime are used in the paints, adhesives, caulking agents, sealant industries and paints.
Pharmaceutical applications include lime being used as a calcium source and other products derived from lime, such as Precipitated Calcium Carbonate (PCC) are found in a larger number of pharmaceuticals, including dietary supplements, antacids, and other well-known medicines. Lime products are also used in the production of personal care products and can be found in toothpaste as well.
There are essential applications of lime products in the mining, extraction, refining and smelting of many non-ferrous metals, including aluminium, cobalt, copper, gold, lead, lithium, nickel, titanium, uranium and zinc, as well as key uses in the treatment of effluents and tailings from minerals processing and settling, dewatering and filtration of mine waters with lime are also important for environmental protection.
The production of oil additives for lubricants specifically sulphonates, phenates and salicylates require specialised lime products. The manufactured oil additives are used as detergents, to control acidity, and to improve the life of combustion engines in cars, ships and other vehicles.
Sintered dolime is used in the manufacture of refractory lining bricks and mortars as well as in granular repair products that can be applied to the hot refractories to restore them in situ and enable the heated vessel to remain at high temperature for longer, increasing efficiency.
In combination with silica sand, lime is used in the manufacture of calcium silicate fire protection boards and castings that are widely used in high fire risk situations to both replace combustible products and provide protection of critical parts of equipment that needs to continue to function in fire situations. Lime is also used as a component in fire extinguisher foam formulations for high intensity fires, including aviation fuels.
Across a range of chemistries, lime and dolime products are used as raw materials, as pH controllers and as chemical reagents in the production of numerous chemicals that are widely used in everyday life. Applications in include organic and inorganic chemicals as well as parachemistry including soaps, detergents, and paints.
Many industrial processes have gaseous emissions to atmosphere which is a highly controlled area of environmental protection. Lime is extensively used in the removal of acidic and other pollutants of emissions to air from power stations, energy from waste plants, kilns, furnaces and incinerators. Lime products are introduced into the flue gas streams that often contain sulfur dioxide, hydrochloric and hydrofluoric acids promoting a reaction to form insoluble calcium salts that can then be collected for recycling or disposal. This helps clean the air we breathe, reduces acid rain and lowers greenhouse gas emissions.
Manufacturing industries often have fluids that require pH control to either reduce acidity or provide alkalinity and lime products are often provided in solution as milk of lime to enable easy introduction into liquid systems and thorough mixing to deliver their effects. Acidic mine waters are pumped to surface and prior to release into the environment can be treated with lime to control their pH and precipitate out metals and other pollutants.
Across many industrial manufacturing applications, there are process and wastewater effluents that require treatment with lime and other reagents to enable re-use or discharge of the water.
Treatment of sewage sludges with lime can address dissolved organic matter, excess nutrients (e.g. phosphates) and heavy metals. As with effluent treatment, there are advantages for the local environment and in addition, lime disinfects and conditions the sludge by a rise in temperature and/or a rise in pH, so that it may be recovered for use in agriculture. A wide number of organic and inorganic sludges can be treated using lime to increase solids content.
Often referred to as Stabilisation/Solidification (S/S), lime is used for the remediation of land affected by contamination. S/S is a civil-engineering-based remediation technique in which contaminated soil is mixed with lime and cement to immobilise contaminants as well as improve its engineering properties (See Soil stabilisation). Many derelict and brownfield land sites are made up of poor land containing contaminants and so S/S provides a practical technique that provides cost-effective remediation that enhances resource efficiency as stabilised materials remain on site and so reduces the need for imported materials. This in turn minimises costs and carbon emissions.
The high alkalinity of hydrated lime products and the heat of hydration from a quicklime can both be used in animal sanitation. The alkalinity of hydrated lime can help to protect from a broad range of bacteria, viruses and parasites while careful use of the heat of hydration from a quicklime can extend the range of viruses that can be addressed. The application of milk of lime onto the fabric of the buildings in which animals live can also help improve animal hygiene.
Vital for the wellbeing of millions of people, drinking water treatment has become an essential aspect of modern life. Lime products are used to adjust pH, remove metals and precipitate solids and the treatment with lime is used to correct water hardness and lower the deposition of scale in pipes, boilers and other appliances. Lime treatment raises the pH and can kill bacteria and viruses whilst also limiting the undesirable reabsorption of metals such as copper, zinc and lead. Water that is too acidic, with a lower pH can lead to damage of pipework and equipment. Water that is too hard can lead to deposition of scale and can be decarbonised by lime slurry treatment.
Sugar manufacturers use lime to precipitate out impurities from beet and sugar cane extracts and, in the processing of the sugar juice, the carbon dioxide from the lime production can be used in a carbonation stage which produces a residual calcium rich sucronate which can go on to be used in the agricultural liming of soils. The harvested beet is cut into thin strips and then the sugar is extracted after mixing with hot water. The raw juice obtained is then purified by adding a milk of lime solution. The purified syrup is then filtered, heated and tiny sugar crystals are added which are allowed to grow to the required size for the desired product. The resulting sugar crystals are then washed, dried and cooled.
The calcium ions in lime products help to boost soil fertility, as well as adjusting pH, both of which can improve crop yields and thus can help to reduce the amount of fertilisers required by improving plant uptake that is a consequence of good pH balance. Ensuring adequate calcium in the soil also boosts micro-organisms and earth worm activity. The action of calcium products can also improve the soil structure which aids water and air exchange. An agricultural liming material has calcium and magnesium compounds capable of neutralising soil acidity and includes quicklime, hydrated lime, and dolomitic lime, as well as agricultural limes, such as limestones, chalks, marls and shells. Lime based by-products, such as slags from metal refining and residual limes from sugar manufacturing, are also used in agricultural liming.
Many animal feeds include lime products as an excellent source of calcium which can help animals to develop strong bones so that they can support greater muscle mass and hence increased meat yield. In chickens for example, the calcium addition in their feed provides calcium for egg shell production which again enables an increase in the yield of eggs for laying hens or stronger bones for carrying more muscle mass and again increasing meat yield.
Acting as a flocculant for clays, lime addition can be a periodic treatment of fish farming ponds to provide cleaner, healthier water for fish. Calcium can also be an additive in fish food pellets.
The shelf life of fruit in storage can be extended using lime. As fruits ripen they emit carbon dioxide, which lowers the level of oxygen in the atmosphere and accelerates the rate of deterioration of the fruit. By circulating air around the fruit and over exposed lime, the lime absorbs the carbon dioxide and the fruit remains fresher for longer. Residues from processing citrus fruits when mixed with lime can then be dried and used as cattle feed. In addition, lime can also be used to neutralise waste citric acid and to raise the pH of fruit juices to stabilise the flavour and colour.
Separation of cream from whole milk during butter production can include the addition of liquid lime to alter the pH before pasteurisation. To separate the casein, acid is added to the skimmed milk and the casein can be mixed with lime and sodium fluoride to produce calcium caseinate, which is a type of adhesive. When the remaining skimmed milk is fermented, lime can be added to form calcium lactate, which has medicinal properties or acid can be added to produce lactic acid.
Treatment of the waste materials from meat rendering plants with milk of lime causes the collagen to swell and this is known as alkaline hydrolysis. The process was developed when the use of rendering plant wastes in animal feed were banned. The treated waste is then cleansed, dried and the resulting product can be used as an adhesive or as gelatin in the manufacture of capsules, cosmetics and ointments.
The production of baking powder, monocalcium phosphate, is achieved using lime and phosphoric acid and produces a fast acting, raising agent used for example in pancake mixes.
The manufacture of many inorganic salts such as calcium citrate a food and drink additive, and calcium phosphate, a toothpaste additive rely on the use of lime.
Mortars are one of the earliest applications of lime dating back thousands of years thanks to the binding action of the lime with the fine aggregates and water in a mortar mix. The simplicity of building with stacked rectangular units and placing a deformable mortar that sets slowly enough to allow adjustment of the blocks and quickly enough to allow multiple layers to be built in a day, is at the core of the success of masonry, blockwork and brickwork, with the rectangular units working together with the mortar to form stable and durable structures. The beneficial characteristics of lime mortars include their resilience to water by the way in which they allow a degree of moisture movement that enables evaporation and absorption to take place and maintain a dynamic balance without leading to leakage of liquid water.
Using a similar mix to mortars, though with different proportions of the ingredients to provide different performance characteristics, lime renders, applied to the outer surfaces of buildings, need the ability to adhere well to a vertical surface while still in the unset state to allow for placement and smoothing. Then after setting, the render needs to retain the adhesion capability whilst also having characteristics that allow for the expansion and contraction deformations that occur due to ongoing temperature variations, as well as the resilience in being exposed to the weather and remaining intact and in place for many years in the life of the building, with a minimum of maintenance.
The finest of aggregates are used in the binder rich mix designs of lime plasters which are applied on the internal surfaces of buildings to provide the desired smooth finishes that are then able to be decorated as desired, or remain as applied. The more stable environment within buildings mean that less resilience than renders is required, enabling thinner layers of the more expensive plaster mix to be applied. The binder rich characteristics of lime plasters are often utilised to allow them to be formed into embossed decorative shapes with extremely fine detailing. asset management were adopted.
Mixing lime with cement, sand, water and aluminium powder in the right proportions and pouring the resulting slurry into a large mould, allows a reaction between the lime and the aluminium powder to create bubbles of gas dispersed through the mix. The gas bubbles form, grow and cause the setting slurry to expand, rising within the mould and forming a honeycomb, lightweight material. When the setting of the mixture is sufficient for demoulding, the next step is to introduce planes of weakness within the soft material by wire cutting before the whole block is then steam autoclaved at high pressure and temperature, causing the material to set hard. After removal from the autoclave, mechanical fracturing along the planes of weakness, then creates the structural blocks which have excellent thermal and sound insulation properties and are widely used throughout the building industry.
Made of sand, lime and water, the raw sand-lime brick mixture is matured in reactors before it is compressed under vapour pressure to form sand-lime bricks. During the process of pressure-hardening in autoclaves, the large proportion of available calcium oxide ensures that optimum calcium silicate hydrate crystals are formed to give the brick its high mechanical strength, density and stability.
Lime concrete or "limecrete" is made by mixing controlled amounts of sand, aggregate, binder, and water. Hydraulic lime or hydrated lime with additives are used as the concrete binder. This type of concrete is widely used in heritage and conservation construction and is increasingly popular in ‘eco’-buildings – for example – with underfloor heating systems.
One of the ingredients in the manufacture of high alumina cements is quicklime. The properties of high alumina cements with rapid hardening and high strength mean they are used in high stress environments including use in marine construction, drainage infrastructure and also in refractory concretes where strength at high temperatures is required.
Limewash is a traditional method of painting walls with a colour base that allows the masonry to breathe, providing both protection and aesthetic appeal. Limewash is also widely used in agricultural buildings due to its germicidal qualities coupled with its extreme ease of application and low cost.
Soil stabilisation with lime reduces the need to bring in aggregates and other materials to site and avoids removal of unmodified materials thereby significantly reducing transport costs and environmental impact. Although widely known as soil stabilisation, there are a number of distinct processes which can be carried out by the addition of lime to existing soils. Improvement is the first process step, where the heat generated by the reaction of the moisture in the soil with the lime reduces the moisture content. This is followed by modification, where the soil consistency changes through the reaction of the clay particles with lime. Over time, the soil becomes stabilised by long term chemical reactions that increase the soil strength. Using this process, it is possible to convert an unworkable site into a solid working platform providing a base for construction development or as the base layers for pavements, and foundations to earthworks.
There are various different applications of lime treatment of uncontaminated soils, for example the treatment of excavated soils from services trenches, to enable their use as a modified backfill into the same trench that they have been excavated from, thus enabling the re-use of site excavated material instead of removing the excavated material from site and importing materials excavated and transported from elsewhere. Soils that have become contaminated by industrial processes and require treatment can often require lime addition to modify their consistency to allow other treatments to be applied such as cement or other binders. The fully bound materials are then able to retain the contamination within them and prevent environmental harm from leaching of the contaminants into surrounding soils and water courses.
High performance foundations for transport routes such as road and rail and other uses, can be achieved using lime as an activator for hydraulic road binders that have pozzolanic reactions, such as cement, ashes from furnaces and ground slags from metal refining. The mix specifications and designs are approved and included in guidance manuals for utilisation of secondary materials from industrial processes to reduce the carbon footprint of construction.
The uses of lime in tunnelling include the treatment of the excavated materials from the tunnel by the addition of lime as a modifier for both improved handling characteristics for transport and improved characteristics for pressing in filter cakes or further re-use as fill material for other construction uses. Lime can also be used as an additive in the grouts used to fill the space between tunnel linings and the excavated soils which can extend the setting time of the grout, enabling longer pumping distances and reduce or even eliminate the quantities of high chemistry, expensive, additives used to achieve the same effect.
Quarrying activities can be enhanced by using lime products to help improve the quality and characteristics of excavated materials that do not fulfil the primary excavation purpose. This treatment of aggregates is commonly done to address higher than desired clay contents and can achieve improved value products for use in construction and other applications.
Addition of hydrated lime in asphalt has been shown to be beneficial thanks to the multi-functional characteristics of its effects. Lime is well known as an additive that helps prevent the phenomenon of stripping of aggregate from the surface of the asphalt which, not only deteriorates the qualities of the surfacing, also causes the presence of loose stones on the surface. Marshall asphalt specifications, that are used extensively in airport aprons, taxiways, and runways, include hydrated lime addition as the bond between the aggregates and the asphalt binder is enhanced and reduces the risks of loose aggregates on airport surfacing that can be catastrophic to aircraft engines. Lime has also been shown to significantly improve durability, providing up to 25% longer pavement life; increasing moisture resistance; increasing ageing resistance; and increasing mechanical properties of the asphalt. The failure of asphalt surfacing through poor quality design, materials, application or maintenance leading to potholes would be reduced if the use of hydrated lime in mix designs, the improvement of installation quality controls and the application of better asset management were adopted.
MPA Lime is part of the Mineral Products Association, the trade association for the aggregates, asphalt, cement, concrete, dimension stone, lime, mortar and industrial sand industries.
MPA Lime, 1st Floor, 297 Euston Road, London NW1 3AD
T: 0203 978 3400