Coal Proximate Analysis PDF

**PROXIMATE ANALYSIS OF COAL** ============================== #### **Aim:** To conduct the proximate analysis of a coal sample. #### **Apparatus:** Alumina crucible, weighing balance, oven, muffle furnace, desiccators and coal samples. #### **Theory:** Coal is a highly carboneous matter that h...

**PROXIMATE ANALYSIS OF COAL** ============================== #### **Aim:** To conduct the proximate analysis of a coal sample. #### **Apparatus:** Alumina crucible, weighing balance, oven, muffle furnace, desiccators and coal samples. #### **Theory:** Coal is a highly carboneous matter that has been formed as a result of transformation of biological matter (dead plants and animals) under conditions of heat and pressure for millions of years. It is mainly composed of C, H, N & O, besides noncombustible matter such as silica and alumina. The following properties determine the selection of coal for any particular purpose. #### **Calorific Value** Calorific value of a fuel (J/kg) is the quantity of heat liberated (J) per unit quantity of fuel (kg), burnt completely. The carbon and hydrogen content of the fuel converted to CO~2~ and H~2~O, respectively, are the *products of combustion*. If the combustion products are cooled down to 25 ^o^C, then the total heat released (chemical heat + sensible heat) is called the *gross calorific value*. Presence of components other carbon and hydrogen in the fuel, decreases its calorific value and hence its quality. #### **Moisture Content** This increases the weight of coal and increases the cost of its transportation. Presence of excessive moisture may quench the fire in the furnace. #### **Volatile Matter** In the pyrolysis of coal, i.e. heating of coal in the oxygen-free atmosphere, several components bonded to coal are released as volatile product. The volatile components are H~2~, CH~4~, CO, CO~2~, N2, NH~3~, H~2~S, higher hydrocarbons, tar and chlorides. Although some of these components have calorific value, they are not directly useful for a metallurgical reactor and therefore their presence decreases the rank of the coal. #### **Ash Content** Coal is associated with certain inorganic matter, which gets deposited along with vegetable matter or gets into coal by subsequent infiltration (during the formation of coal over millions of years). The ash consists mainly of silica, alumina, iron oxide and lime. Higher ash content decreases the efficiency of all furnaces. #### **Fixed Carbon** Fixed carbon content increases with the coal rank, in the order of peat lignite bituminous anthracite. ***Coal Analyses*** The *rank* (quality) of a coal is decreased due to the presence of (i) moisture content, (ii) volatile matter and (iii) ash content; the estimation of the mass fraction of these three components is called the *proximate analysis* of coal. In contrast, performing the chemical analysis of coal to determine the mass fractions of C, H, O, N, S, Cl, *etc*., is known as the *ultimate analysis*. Proximate analysis of Indian Coal (mass fraction) Moisture 14% ----------------- ----- Volatile matter 21% Ash 42% Fixed carbon 31% #### **Procedure:** ###### The following procedure is common to determination of moisture, volatile matter and ash content. 1. Weigh the empty crucible. 2. Take around one gram of coal sample in the crucible and weigh it. 3. Place the crucible in the furnace. In the case of volatile matter analysis, the crucible is closed with a lid to prevent the oxidation of coal by air in the furnace. The furnace temperature and certain dwell time for each case is given below. Component analyzed Furnace temperature, ^o^C Dwell time, minutes -------------------- --------------------------- --------------------- Moisture 100 60 Volatile matter 900 10 Ash 700 60 4. Remove the crucible with the help of tongs, place it in a desiccator and allow it to cool. 5. Weigh the crucible with the residue in it. Fig. Open and closed crucibles, the latter one is for analysis of volatile matter. #### **Observations** **Expt. No.** **Experiment** **Crucible mass, g** **(Crucible + Sample) mass, g** **Sample mass, g** **(Crucible + Residue) mass, g** **Residue mass, g** --------------- ----------------- ---------------------- --------------------------------- -------------------- ---------------------------------- --------------------- 1 Moisture 2 Volatile matter 3 Fixed Carbon **\ ** **Let the mass fractions of moisture, volatile matter, fixed carbon and ash content be denoted by** *Y~M~*, *Y~VM~*, *Y~FC~* and *Y~A~*, respectively. Then the mass fractions are deduced from the following. *Y~M~* = 1 -- (residue mass)~Expt\_1~ / (sample mass) ~Expt\_1~ *Y~VM~* = 1 -- (residue mass)~Expt\_2~ / (sample mass) ~Expt\_2~ -- *Y~M~* *Y~FC~* = 1 -- (residue mass)~Expt\_3~ / (sample mass) ~Expt\_3~ -- *Y~M~* -- *Y~VM~* *Y~A~* = 1 -- *Y~M~* -- *Y~VM~* -- *Y~FC~* **Results** The proximate analysis of coal yields the following: 1. Moisture content \_\_\_\_% 2. Volatile Matter \_\_\_\_% 3. Fixed Carbon \_\_\_\_% 4. Ash content \_\_\_\_%