Lime

Lime is among the chemicals used in the treatment of drinkable and industrial water resources. It’s Used by many municipalities to improve water quality, especially for water softening and arsenic removal

Softening

In water softening, the hydrated lime is used to remove carbonate hardness from water (caused by biocarbonates and calcium and magnesium carbonates). The hardness called non-carbonate hardness, which is caused by other calcium and magnesium salts, is generally treated by lime-soda treatment, which requires the precipitation of magnesium with lime. The co-produced calcium salt reacts with the soda ash to form a calcium carbonate precipitation. Lime softening can also be used to purify arsenic from water

pH Adjustment / Precipitation

The hydrated lime is widely used to adjust the pH of the water to prepare for further purification. Lime can also be used to neutralize acid water, thereby reducing corrosion of the main line pipes from acid water to prevent corrosion. Corrosive water contains excessive amounts of carbon dioxide (carbonic acid). The lime precipitates CO2 to form calcium carbonate, which provides a protective coating inside the water distribution pipes.

Lime is used in combination with alum or iron salts to remove the turbidity caused by suspended solids in raw water. It helps to maintain the appropriate pH for the most satisfactory coagulation conditions. In some water treatment plants, alum sludge is treated with lime to facilitate sludge thickening in pressure filters.

Effect on Pathogen Development
By adding lime, in 24 - 72 hours, the pH of water increases to 10.5 – 11, this will eliminate the necessary environment for the development of bacteria and certain viruses. This lime application is used in places where phenolic water is present because chlo rine application causes an unpleasant taste of water in the presence of phenol. This process so-called extreme alkalinity process also destroys heavy metals.

Removal of Trace Elements Causing Pollution
Lime is also used in the purification of manganese, fluoride, organic tannins and iron

LIME USAGE IN THE TREATMENT OF HAZARDOUS WASTES
Lime is widely used to treat hazardous wastes. Lime stabilizes most metals by converting them to more stable forms that are less likely to be chemically soluble. It can also be used to neutralize acidic substances.

LIME USAGE IN THE TREATMENT OF WASTE WATER
Lime is also used extensively in the purification of domestic waste water as well as the purification of industrial effluents.

Domestic Waste Water Treatment
In advanced wastewater treatment plants, it is used in tertiary processes where lime suspended solids and solids together with phosphorus precipitate as complex calcium phosphate. Due to the high pH of 10.5-11.0 formed by the lime, it is also facilitated to remove the other algae nutrient nitrogen. Thus, removal of phosphorus and Nitrogen helps to prevent the process of ossification (seaweed formation) in surface waters.

When alum and ferric chloride is used for precipitation, Lime is used to increase the pH value caused by these acid salts and to provide the basic environment necessary to remove the active nitrogen.

In sewage systems where sewage sludge is filtered by vacuum or by pressure filtration, lime and iron chloride are used to help sludge to stabilize the sludge and for final clarification of the active substance.

Industrial Waste Water
Limestone has numerous applications in the treatment of industrial wastewater, especially in which acidic wastes need to be neutralized. Sulfuric acid based waste pickling solutions are neutralized with lime in steel plants. Lime is also used to precipitate chromium, copper and heavy metals in the treatment of wastes of coating plants.

Lime is used to neutralize sulfuric acid wastes from artificial silk factories and to precipitate solids in solution.
Lime citrus helps in clearing waste water, clarifying waste water and processing by-products of citrus pulp.

The high degree of acidic drainage in working and abandoned mines is often neutralized with lime. Further clarification of waste is achieved by precipitating iron in the pyritic extractor. Coal washing plants use lime to neutralize acidic waste or reduce friction on steel equipment and to process the waste for reuse.

LIME USAGE IN TURKEY AGRICULTURAL LANDS

Limestone is used in agriculture directly by mixing to soil. Other important fields of application, is manufacturing composite fertilizer and animal feed production. the limestone is used to eliminate the damage caused by acid rain.

FORMATION OF ACID IN SOILS OCCURES WITH VARIOUS WAYS

CO2 and H ion released by root respiration combine with oxygen to form water. Water is combined with CO2 to form a weak acid, carbonic acid.

When CO2 in rain water enters the ground, it combines with water to form carbonic acid.

Organic acids can form in the decomposition process of the dead cover composed of the leaves and organic wastes of the vegetation.

The acids formed as a result of chemical fertilization (for example ammonium sulfate fertilizer)of the soil also play a role in the soil to gain an acidic character.

Calcium ion is washed away from the environment in high rainy areas and causes acidification of soil.

Excessive sulfur dioxide emission resulting from the formation of acid rain.

It provides the soil with an acidic character. The most effective of these is the precipitation. In places where there is not much rainfall, soils can take acidic character due to other effects.

LIME USAGE FOR SOIL STABILIZATION

In many cases, lime can be used to improve soil workability and load-bearing properties. Quicklime is often used to dry Age soils on construction sites and elsewhere, which reduces waiting time. A more significant use of lime is the stabilization of soil under road and similar construction projects. The use of lime can significantly increase the stability of the substrate, its load-bearing capacity. Both quicklime and Hydrated lime can be used for this purpose.
 

IMPROVEMENT OF SOIL PROPERTIES WITH LIME: Lime is a perfect material for the short-term replacement of soil properties. Lime can replace almost all well-ground soils, but the most striking development occurs in clay soils with medium to high plasticity. The change occurs because the calcium cations provided by the slaked lime supported by the high pH environment of the lime-water system normally replace the cations on the surface of the clay mineral. Thus, the clay surface mineralogy is modified by creating the following benefits:

• Reduction of plasticity

• Reduction of moisture-holding capacity (drying)

• Reduction of swelling

• Increased stability

• Creation of a dry work platform

SOIL STABILIZATION WITH LIME: Soil stabilization occurs when lime is added to the reactive soil to form long-term strength through pozzolanic reaction. Since calcium comes from lime reacts with soluble aluminates and silicates which comes from the clay, this reaction produces constant calcium silicate hydrates and calcium alumina hydrates. The Pozzolanic reaction can continue for a very long time, even for decades - as long as there is sufficient lime and the pH remains high (above 10). As a result, lime processing can provide high and long-term strength gains. The key of a good pozzolanic reaction is a reactive soil, a good mix and reliable construction applications.
 

The benefits of soil stabilization are as follows:

• Increases in the modulus of elasticity (in most cases 10-fold or higher)

• Severe improvements in breaking strength (in some cases 20 times or higher)

• Continuous power gain over time, even during periods of environmental or load damage (self-recovery)

• Long-term durability under decades of service and even under severe environmental conditions.

These performance benefits turn into short- and long-term economic benefits.

In addition to the stabilization of new materials, lime is an excellent choice for the recovery of road floors.

Lime stabilization is not a difficult process to perform. After a suitable mixture design and testing have been carried out, onsite mixing is often used to add an appropriate amount of lime at a depth appropriate to the soil. Spraying and mixing is used to combine lime and soil in a comprehensive manner. For heavy clays, the pre-mixing is continued for 24 to 48 hours (or more) of moisture improvement followed by final mixing. Appropriate compression is required to maximize strength and durability. Appropriate improvement is also important. If sulfur is present at levels above 0.3 percent, special procedures are required.

USAGE OF LIME IN IRON AND STEEL INDUSTRY

Quicklime - both high calcium and dolomitic - is used most commonly in the iron and steel industry to purify the steel in the electric arc furnace (EAF) and in blast furnaces. Lime is particularly effective in treating phosphorus, sulfur and silica and, to a lesser extent, manganese. Lime also has important uses in the secondary refining of steel and in the manufacture of steel products.

Electric Arc Furnaces

In electric arc furnaces, scrap iron and steel, pig iron, iron ore and enriched iron ore are placed in an oven and heated by the use of heat from electric current. A lime flux is added with a mixture of quicklime or slaked lime and dolomitic lime. The total amount of flux is used around 50 Kilograms per tonne of steel (up to 50% can be dolomitic lime).

The benefits of lime flux: The lime flux purifies impurities and forms a slag that can be separated from the steel and is removed from the oven as a liquid. It also reduces refractory wear and gassing and can provide foam slag for long arc operation. lime is used unless special product is required by special furnace injection applications.
 

Limestone Use in Blast Furnaces

Iron is generally produced by burning iron ore (Fe2O3, Fe3O4) in the blast furnace (more than 100 m) with coke and air in reducing environment.

Fe2O3  +  3 CO  ®  2 Fe  +  3 CO2 ­

Meanwhile, the combustion gases (CO, CO2, N2, ..) which are formed cannot find suitable ways to exit the fine and frequently grained surfaces of the iron ores (0-8 mm) and therefore the furnace is in danger of being blocked. In order to prevent this problem, the ore must be agglomerated before being fed into the furnace, thereby increasing the hardness and gas permeability, which is called agglomeration.
 

In order to agglomerate the iron ore, pulverized coal and lime products are placed in it and burned at high temperatures (1200 - 1400 ° C). According to applied process, it is called sintering, briquetting or pelletizing. As a result of this process ore in 0-8 mm is transformed into hard particles in 2-2.5 cm size.

Lime products have important contribution to agglomeration process. Milled limestone (CaCO3), which is added to 10-12% ore with coal dust, reacts with the silicon and aluminum in the ore and calcined at approx 1200 - 1400 ° C and forms the calcium silicate - aluminum ferrite system.

This compound binds the fine particles of iron ore and imparts a certain hardness.

Another important role of limestone in the mixture is to keep the molar ratio of CaO: SiO2 at certain intervals (1.5-1.7 which is required for slag formation in high furnace

Some producers add 1 to 2% or more grinded quicklime (CaO) to the ore.

Quicklime

1. It is hydrated in mixing and ensures adherence of small grains (0.5-2 mm) ores and increases the permeability of the beds.

2. The heat released during hydration (270 kcal / kg CaO) provides energy economy by reducing the sintering temperature from 1400 ° C to 1000 ° C.

3. It increases sintering capacity and mechanical strength of sinter pellets.

The role of dolomite in the mixture is to adjust the slag composition that will occur in the blast furnace and to protect the furnace refractories.

Analysis of a typical sintered iron ore is as follows:

Slaked lime, which is used in pellet and briquette production up to 5% ratio, allows the grains of grains to stick and form.

Pig Iron production (blast furnace process)

The liquid iron is obtained by burning the ore given to the blast furnace after curing.

Fe2O3  +  3 CO  ®   2 Fe  +  3 CO2 ­
FeO       +     CO  ®      Fe  +      CO2 ­

Limestone is used to remove impurities (such as sulfur, silicon, aluminum, manganese) from ore or coke during the reduction of iron ore to iron in blast furnaces; The impurities in the ore generally have high melting temperatures (E.Ex Al2O3: 1730°C; lime: 2570°C.) and are therefore very difficult to separate at furnace temperatures. However, as a chance, the lime compounds of these impurities can be removed from iron by melting at temperatures as low as 700 - 1400 ° C.

The limestone reacts effectively with impurities by turning into lime at high temperatures in the kiln and removes them as a low-density slag (approx. 250 - 400 kg slag / t-iron).

CaCO3  ®   CaO + CO2­
CaO + FeS  ®  CaS (curuf) +  FeO
CaO + SiO2  ® CaSiO3 (curuf)

Generally slag components

CaO - Al2O3 - SiO2 - MgO - S - Na2O
(%90)  like this.

The fluidity of the slag should be high and the melting point should be low. For this, it is preferable to have a basic structure of slag. The limestone given to the blast furnace increases the fluidity of the slag compound (low viscosity) and It forms compounds at low temperatures with impurities.

When the lime dosage given according to type and amount of impurities in the ore, is choosen to be ensure the degree of basicity (CaO / SiO2) as more than1.1, a slag is obtained from basic structure with good properties (viscosity viscosity optimal: 1 - 5)

The amount of limestone given to the furnace depends on the purity of the ore, but usually it is between 160 and 200 kg per ton of iron. Blast furnace slag is used in Portland cement.production.
 

Secondary treatment

Where purer steel is required, secondary refining is usually required. Many secondary refining processes use lime to perform important functions, such as adjusting the temperature or chemistry of the steel, removing additional impurities, and preventing impurities from being sucked back. In addition, it can be used in combination with other materials such as florspar or alumina to form synthetic slag that is used as the lime to remove the quicklime, sulfur and phosphorus.

Steel Products

The extinguished lime (whether dry or juicy) has a number of applications in the manufacture of steel products. Widely used in wire drawing from steel rods or used to prevent sticking on cast iron molds

Lime is used to neutralize the acid-based waste pickling solution in which the iron salts are also precipitated. Lime bath is usually used to neutralize the pickling acid remaining in steel products. In addition, the steel product may be coated with lime to protect temporary corrosion. Slaked lime is used to neutralize the acid in the coke by-products.

Kireç birçok hava kirleticilerin denetimi uygulamalarında kilit bir rol oynamaktadır. Kireç asitli gazları, özellikle uçucu gazlardan kükürt dioksidi (SO2) ve hidrojen kloridi (HCl) arıtmak için kullanılır. Kireç tabanlı teknoloji aynı zamanda cıvanın uzaklaştırılması için de kullanılır.

BACA GAZ ARITMA İÇİN KİRECİN KULLANIMI

Kireç birçok hava kirleticilerin denetimi uygulamalarında kilit bir rol oynamaktadır. Kireç asitli gazları, özellikle uçucu gazlardan kükürt dioksidi (SO2) ve hidrojen kloridi (HCl) arıtmak için kullanılır. Kireç tabanlı teknoloji aynı zamanda cıvanın uzaklaştırılması için de kullanılır. 

Kireç, kireç taşına göre daha reaktiftir, ve daha az ana teçhizata gereksinim duyar. Kireç kullanılarak SO2 arıtma verimi (Termik santrallarda) yüzde 95 ile 99 arası değişir. Kireç kullanarak HCl arıtma verimi (evsel atıktan enerji üreten tesisler) yüzde 95 ile 99 arası değişir. 

Asitli gazların arıtılması için iki ana yöntem bulunmaktadır: kuru arıtma ve yaş arıtma. Her iki yöntem de yaygınlıkla termik santrallarda  kömürün yanmasından doğan uçucu gazların temizlenmesi için kullanılır. Kuru arıtma aynı zamanda başlıca HCl denetimi için enerji fabrikalarına ve diğer endüstriyel tesislerde Evsel atıkta kullanılır. Kireç her iki sistemde de kullanılır.

Kuru Kireç Arıtımı(Scrubbing)

Kuru arıtmada, SO2 ve HCl arıtmak üzere kireç uçucu gaza püskürtülür. İki ana kuru süreç bulunmaktadır: “kuru enjeksiyon” sistemleri kuru sönmüş kireci uçucu gaz oluğuna besler ve “SPREY DRYER” Pulverize kireç bulamacını ayrı bir kaba besler. 

“SPREY DRYER” tipik olarak silindir bir üst kısımla ve konik diple silo şeklindedir. Sıcak uçucu gaz en üste akar. Kireç bulamacı atomizör (örn., memecik) yoluyla SO2 ve HCl emdiği en tepenin yakınındaki silindir içinden püskürtülür. Kireç bulamacındaki su daha sonra sıcak gazla buharlaştırılır. Arıtılmış uçucu gaz silindirik kesimin dibinden yatay bir oluk içinden akar. Kurutulmuş reaksiyona girmemiş kirecin ve reaksiyon ürünlerinin bir kısmı koninin en dibine düşer. Uçucu gaz daha sonra kirecin ve reaksiyon ürünlerinin kalanını ayırmak üzere filtre edilir.

Hem kuru enjeksiyon hem de “SPREY DRAYER”, özel denetim cihazlarında toplanmış kuru nihai ürün oluşturur. Termik santralarda, kuru arıtma başlıca düşük-kükürt yakıtları için kullanılır. Evsel atıktan-enerji Üreten tesislerde, kuru arıtma SO2 ve HCl arıtmak için kullanılır. Kuru arıtma HCl arıtımı için aynı zamanda diğer endüstriyel tesislerde de kullanılır. Kuru arıtma yöntemleri geçtiğimiz yıllarda mükemmel arıtma verimi ile ciddi biçimde gelişme göstermiştir. 

Yaş Kireç Arıtma(Scrubbing)

Kireç Yaş arıtmada, kireç bulamacı uçucu gaz arıtıcıya püskürtülür. Tipik bir sistemde, temizlenecek olan gaz silindir benzeri kulenin dibine girer ve kireç bulamacı duşu yoluyla yukarı doğru çıkar. Kükürt dioksit püskürtücünün içine emilir ve daha sonra Yaş kalsiyum sülfit olarak çöktürülür. Sülfit, satılabilir bir yan ürün olan alçıtaşına dönüştürülebilir. Yaş arıtma başlıca yüksek-kükürt yakıtları ve yüksek-verimlilikte kükürt dioksit arıtmanın gerektiği bazı düşük-kükürt yakıtları için kullanılır. Yaş arıtma, SO2 arıtma kapasitesini artıran ve ekonomik bir teknolojidir.  

HCl Arıtma

Kireç aynı zamanda HCl gibi diğer asit gazlarla hızla reaksiyona girdiği için, kireç arıtma diğer evsel ve endüstriyel tesis türlerinde HCl nötüreştirmek için kullanılır:  

•    Evsel atıktan-enerji üreten tesislerde, kuru kireç(scrubbing) arıtma dünyada çok yaygın olarak kullanılmaktadır. Kireç kullanılarak HCl arıtmanın etkinliği 95 ile 99 arası değişmektedir.
•    Dünyada sekonder  alüminyum fabrikalarında, örneğin,  kireç arıtma yöntemi HCl için en iyi arıtma teknolojisi olarak bilinmektedir. Arıtma verimi yüzde 99’dan daha yüksek olarak gerçekleşmektedir.

Cıva Arıtımı

Dünyada  cıva arıtımı için birçok farklı yöntem değerlendirilmektedir. Uygulanan  bir arıtma  teknolojisi olarakta sönmüş kirecin aktif karbonla birlikte kullanılmaktadır. Bu yöntem yüzde 95-97 kireç ve yüzde 3-5 aktif karbon içermektedir.