Thermal decomposition calcium carbonate

Consideration thus far has been on only balanced reactions which occur in one phase, that is, homogeneous reactions. There are, of course, a great many reactions which occur between substances in different phases, and these are known as heterogeneous reactions. Numerous reversible, heterogeneous reactions are known, and it is pertinent now to bestow consideration on how far the law of mass action can be applied to such cases. The familiar reaction of the decomposition of calcium carbonate thermally - a well-known example of a reversible reaction represented by the equation... 

Uranium can be prepared by reducing uranium halides with alkali or alkaline earth metals or by reducing uranium oxides by calcium, aluminum, or carbon at high temperatures. The metal can also be produced by electrolysis of KUF5 or UF4, dissolved in a molten mixture of CaCl2 and NaCl. High-purity uranium can be prepared by the thermal decomposition of uranium halides on a hot filament. 

Several methods are described for the production of tantalum and niobium metal. Metals can be obtained by reduction of pentachlorides with magnesium, sodium, hydrogen or by thermal decomposition in vacuum [24,28]. Oxides can be reduced using carbon, aluminum, calcium, magnesium [28, 537, 538] or alkali and rare earth metals [539]. 

The most common source is the supersaturation and subsequent scaling of minerals originating in the MU water. Insoluble calcium carbonate in the form of calcite (CaC03) resulting from the thermal decomposition of soluble calcium bicarbonate [Ca(HC03)2] is a classic example. Calcium carbonate quickly forms a white, friable deposit. In addition, the hydrolysis of excess bicarbonate increases... 

Where FW contains bicarbonate or carbonate alkalinity (as calcium, magnesium, or sodium salts), these salts undergo thermal decomposition in the boiler, and the steam-volatile contaminant gas carbon dioxide is introduced into the steam distribution system, as shown ... 

The production of steel begins when iron ore is fed into a blast furnace (Fig. 16.39). The furnace, which is approximately 40 m high, is continuously replenished from the top with a mixture of ore, coke, and limestone. Each kilogram of iron produced requires about 1.75 kg of ore, 0.75 kg of coke, and 0.25 kg of limestone. The limestone, which is primarily calcium carbonate, undergoes thermal decomposition to calcium oxide (lime) and carbon dioxide. The calcium oxide, which contains the Lewis base O2", helps to remove the acidic (nonmetal oxide) and amphoteric impurities from the ore ... 

Calcium oxide can be produced from extensive heating of limestone. Primarily composed of calcium carbonate, limestone is extracted from both underground and surface mines and heated to temperatures exceeding 180°F to convert the calcium carbonate into calcium oxide. This thermal decomposition reaction also generates carbon dioxide gas. 

Example Calculate the volume of carbon dioxide obtained, at room temperature and pressure, when 25 g of calcium carbonate undergo thermal decomposition (relative atomic masses Ca = 40, C = 12,... 

K. J. D. MacKenzie and R. H. Meinhold, Thermal decomposition of dolomite (calcium magnesium carbonate) studied by Mg solid-state nuclear magnetic resonance. Ther-mochim. Acta, 1993, 230,331-337. 

The lime is produced by the thermal decomposition of calcium carbonate in shells dredged up from the ocean floor. The precipitated magnesium hydroxide is filtered off and treated with hydrochloric acid ... 

Thus far we ve been discussing homogeneous equilibria, in which all reactants and products are in a single phase, usually either gaseous or solution. Heterogeneous equilibria, by contrast, are those in which reactants and products are present in more than one phase. Take, for example, the thermal decomposition of solid calcium carbonate, a reaction used in manufacturing cement ... 

FIGURE 13.3 Thermal decomposition of calcium carbonate CaC03(s) ... 

PROBLEM 17.10 Consider the thermal decomposition of calcium carbonate ... 

Quicklime (CaO) is produced by the thermal decomposition of calcium carbonate (CaC03). Calculate the volume of C02 produced at STP from the decomposition of 152 g of CaC03 according to the reaction... 

So far, we have discussed equilibria only for systems in the gas phase, where all reactants and products are gases. These situations represent homogeneous equilibria. However, many equilibria involve more than one phase and are called heterogeneous equilibria. For example, the thermal decomposition of calcium carbonate in the commercial preparation of lime occurs by a reaction involving both solid and gas phases ... 

Calcium oxide has the ancient name of quicklime. Most carbonates, when heated, undergo thermal decomposition to form the metal oxide and carbon dioxide. Sodium and potassium carbonate, on the other hand, don t decompose at all when heated, because sodium and potassium are very reactive metals, so their compounds are very stable. 

Introduction. Acetylene has the empirical formula C2Hs. It shows a greater unsaturation than ethylene, in that it can add four univalent groups to each carbon atom. This xmsaturation is indicated by a triple bond between the two carbon atoms HC=CH. Acetylene is produced in the thermal decomposition of many hydrocarbons. Of theoretical interest is its formation from hydrogen and carbon in the electric arc. It is prepared industrially by the pyrolysis of methane, and by the action of water on calcium carbide. The last method is employed for preparation of small quantities in the laboratory ... 

The thermal decomposition of the carbonate minerals in Green River shales is reflected in the DTG maximum at 730 to 760°C in Figure 2. TG of pure calcite and dolomite show carbonate decomposition at 800°C and 730 to 780°C, respectively. The principle volatile product found by TG-MS in this temperature range was (X. These results are in agreement with Campbell (15), who found shale carbonate minerals undergo three major types of reactions in this region (i) decomposition of dolomite to MgO, C02> and calcite (ii) decomposition of calcite to CaO and CO2 and (iii) reaction between calcite and silica to form calcium silicates. 

The thermal decomposition of calcium carbonate (limestone) and other carbonates produces two compounds, a metal oxide and carbon dioxide ... 

It is common practice to check the performance of a TGA system by running a sample of calcium oxalate monohydrate. This salt is known to thermally decompose in three stages over well-defined temperature ranges. The first step involves the loss of the single water of hydration molecule followed sequentially by the conversion of anhydrous calcium oxalate to calcium carbonate with the loss of carbon monoxide, and thence the decomposition of calcium carbonate to calcium oxide with the evolution of carbon dioxide. 

Ash particles are formed through the thermal decomposition or dehydration of inorganic minerals associated with the coal. Calcium carbonate and clay are the most abundant mineral impurities, with lesser amounts of sulfides, chlorides and oxides also present. The shape of the ash particle is dependent on many factors, two of which are the amount of time and temperature to which the coal is exposed in the combustion chamber (Fisher et al., 1978). The spherical shape, most commonly associated with fly ash particles, shows that complete melting of silicates occurs at high temperature. These spheres may be solid, hollow (cenospheres) or encapsulating spheres (plerospheres). 

---