You may have heard of products like lime dust, lime powder, or hydrated lime before But what exactly are these materials and what are they used for? This article provides an overview of what lime dust is along with its many industrial, agricultural, and domestic applications.
What is Lime Dust?
Lime dust, lime powder, hydrated lime, and slaked lime are all different names for the same chemical compound – calcium hydroxide (Ca(OH)2).
Calcium hydroxide is a white powder produced by combining calcium oxide (CaO), also known as quicklime or burnt lime, with water This process is called slaking or hydration, which is where the name “hydrated lime” comes from
The hydration reaction occurs as follows:
CaO (quicklime) + H2O (water) → Ca(OH)2 (hydrated lime)
The hydration process releases a significant amount of heat, allowing the dry calcium hydroxide powder to be used for various purposes.
Major Industrial Uses of Lime Dust
Lime dust has a number of important industrial uses:
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Steel manufacturing – Lime is used to remove impurities like silica, phosphorus, and sulfur from iron ore during steel production. The lime chemically combines with these elements, allowing them to be separated from the iron.
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Sewage and waste treatment – Hydrated lime can help remove contaminants and odors from sewage. It’s also used to process and detoxify industrial effluents and petroleum waste.
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Flue gas treatment – Lime dust can be used to remove sulfur dioxide from the flue gases of power plants. This helps reduce air pollution.
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Mining – Lime is utilized in mining operations to treat wastewater and regenerate process solutions.
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Construction – Hydrated lime is a key ingredient in mortar, plaster, and cement. It improves workability and plasticity.
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Chemical production – Lime is used to manufacture important chemicals like calcium carbide, sodium carbonate, and calcium chloride.
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Paper production – Lime is used in the sulfite pulping process to extract lignin from wood pulp. It increases brightness and absorbs impurities.
Agricultural Uses of Lime Dust
In agriculture, lime dust has an important use – it can reduce soil acidity and raise pH levels. Lime is spread on fields in a process called liming. Benefits include:
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Allowing plants to better access soil nutrients
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Improving soil structure and friability
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Increasing microbial activity in the soil
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Providing calcium and magnesium to plants
Liming improves soil conditions for crops like legumes, grasses, and vegetables that prefer slightly alkaline soil.
Domestic and Commercial Applications
Around the home and in commercial settings, lime dust has uses such as:
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Gardening – Lime raises pH in acidic soils and provides calcium for plants. Dolomitic lime also provides magnesium.
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Pest control – Lime dust can deter snails and slugs. A lime barrier around gardens stops insects.
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Odor elimination – Lime absorbs odors and ammonia. It’s used in cat litter, compost piles, and garbage cans.
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Water treatment – Lime softens hard water by removing calcium and magnesium carbonate. It also disinfects drinking water.
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Cleaning – Due to its alkalinity, lime can be used as a cleaning agent for metals, masonry, glass, and more.
Safety Precautions When Handling Lime Dust
While lime dust has many uses, it can pose some safety hazards:
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Lime is alkaline and corrosive to skin and eyes. Protective equipment like gloves, goggles, and masks should be worn.
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Inhaling lime dust can irritate lungs and cause breathing difficulties. Ensure proper ventilation.
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Lime dust is caustic if ingested. Keep it locked away from children and pets.
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Contact with moisture produces an exothermic reaction. Keep lime in sealed containers in a dry area.
With proper handling, lime dust can be used safely and effectively in many different industrial and domestic applications due to its versatile chemical properties.
Focus on the construction industry
The high alkalinity of lime in cement is an important factor in chemical hazards in the construction industry. Cement is a corrosive product with a high basic pH (12 to 13). Although a brief exposure causes little risk, exposure to dry or wet cement for a sufficient period of time may cause irreversible damage to the respiratory tract, skin and eyes. 
Lime use in the EU was mainly in the construction industry in 2012, but emergency and burn services say that cement is responsible for a large number of chemical injury victims. People who work with cement are often exposed to it due to the lack of adequate protection.
The lime dust got in between the pants and the worker’s boot. He did not notice it. As a result, no washing was done. After 2 days, a burn as shown in the picture appeared.
The worker feels pain right away when lime gets in their eyes, either from the dust or from the chemical reaction that takes place. When it hits the skin, it doesn’t hurt right away, so the worker doesn’t pay as much attention. However, it is important to wash off the chemical right away because lime, which is corrosive or irritating, will definitely burn. The longer the contact time, the deeper and more serious the burn will be.
There are different families of lime:
Calcium oxide, also known as quicklime, is a white or grayish granular powder with the chemical formula CaO. It is made by heating limestone (CaCO3) to about 900°C and breaking it down in a process called calcination.
Quicklime can react violently with strong acids, especially boron trifluoride (BF3) and hydrofluoric acid (HF).
It is possible to react it with water to create slaked lime. The reaction will be as follows: CaO +H2O —> Ca(OH)2 + 1 155 kJ·kg-1CaO.
When a large volume of quicklime reacts with water, high heat is released (exothermic reaction). Because of this, the water can boil, splash lime on you, and burn you with heat or chemicals. To avoid splashing, it is best to slowly pour the quicklime into the water (rather than the other way around), and the mixture should be stirred throughout the process so that the heat is spread out evenly.
Calcium hydroxide, also known as slaked lime, is a white or grayish solid that is made when quicklime reacts with water. Its chemical formula is Ca(OH)2. Slaked lime can decompose into quicklime at a temperature of 580°C.
Slaked lime is a strong base with low water solubility (1. 56g/l at 20°C) and the saturated solution has a pH value of 12. 4.
Reminder of the pH scale:
- the product is acidic between 0 and 5.5
- it is basic between 9 and 14
- between 5. The physiological pH zone is between 5 and 9. This is the range of pH levels where acids and bases won’t hurt human tissues.
Other types of lime (NHL-Z grade lime, HL artificial hydraulic lime, dolomitic lime…)
Quicklime or slaked lime is widely used in various industrial sectors. We can find them for example in:
- agriculture (soil liming…)
- chemistry (pH adjustment…)
- construction (bleaching, soil stabilization…)
- water treatment (pH adjustment…)
- steel industry (iron conversion, impurity removal…
In the construction industry, lime and cement represent traditional masonry materials.
Lime is a disinfectant material that emits no pollutants. It can be used inside as well as outside while promoting hygrometric exchanges. A frontage with an exterior lime will be impermeable to rain. Lime also has a high tensile strength of adhesion. Because it has many useful properties, lime is being used more and more to make cements, adhesive mortars, and other things.
It is important to follow the directions on how to wear PPE (personal protective equipment) like masks, gloves, or helmets when working with lime.
In contrast to thermal burns, which are just the transfer of calories through radiation and conduction, chemical burns are caused by real molecular reactions. The chemical burn happens when parts of the eye, skin, or mucous membranes react with a chemical aggressor that is corrosive or irritating. There is a donor-acceptor exchange between two simple entities. This exchange corresponds to redox, acid-base, chelation, addition-substitution or solvation reactions. In the case of lime, the exchange will be of acid-base type.
The formation of the chemical burn consists in 3 steps:
- contact between the tissue and the chemical
- diffusion of the chemical in the tissue
- reaction between the product and the target biological compounds
How bad the injury is will depend on the type of product, how concentrated it is, how hot it is, and most importantly, how long it was on the skin, in the eyes, or on the mucous membranes.
Whatever the type of lime, this irritating or corrosive material is dangerous for humans. Because it is used so often and has certain chemical properties, lime is often to blame for serious burns to the eyes, skin, or lungs. Moreover, the types of exposure are varied because of its different possible physical forms (solid, dust or solution).
Hazard classification of quicklime and hydrated lime in the GHS (Globally Harmonized System):
- H315: Causes skin irritation
- H318: Causes serious eye damage
- In the case where slaked lime contains crystalline silica, H335: May irritate the lungs
- H350: May cause cancer (inhalation)
If quicklime or slaked lime gets in your eyes, it could cause mild eye irritation or chemical burns that are so bad they could mean you lose your sight. If you get the powder in your eyes and they are wet, it will be easier for the substance to get inside and cause a chemical burn.
Pain may appear hours after exposure when a significant injury has already occurred. As a result, victims may not be immediately aware of the hazardous exposure. Lime can burn you in many ways, from simple dryness or irritation to chemical burns that can’t be fixed and need medical help.
Inhaling large volumes of lime can cause chemical burns of the nose, throat or lungs.
3. Different types of Lime
FAQ
What does lime dust do to you?
Does lime dust keep bugs away?
Why do farmers sprinkle lime powder?
What is powdered lime used for?
What is garden lime used for?
Garden lime, also sometimes called agricultural lime, is a rock powder used to raise the pH level of soils high in acidity. An application of lime “sweetens” a soil. It can make a “sour” soil more alkaline, which can make a huge difference in the garden.
Is lime good for a garden?
For starters, it puts calcium back into your soil, which is an essential nutrient for growing just about everything and prevents things like blossom-end rot from occurring. In addition, garden lime makes your soil less acidic in terms of pH. It’s beneficial for your garden to be slightly acidic, but you never want it to be too acidic.
How do you use lime in a garden?
In addition, the freeze/thaw cycle helps mix lime into the soil. When adding lime to bare soil, such as a vegetable garden or new lawn, till it into the top 6 inches of soil. Use pelletized lime and a fertilizer spreader to add it to an established garden bed or a lawn. Water the garden or lawn well to move the lime into the soil.
What is lime used for in construction?
In construction, the dominant use of lime is in soil stabilization for roads, earthen dams, airfields, and building foundations. Lime can be combined with certain additives to produce other metals and is also a key ingredient in mortar and plaster in lime slurry form.