Oxygen content of coal

Using Dulong s formula, calculate the Gross and Net calorific value of the coal. 

When a fuel is burnt in air, the carbon and hydrogen of the fuel are converted into CO2 and H2O as per the following equation  

Hence for efficient utilization of heat available from a fuel, an optimum amount of air should be supplied. This amount caiuiot be theoretically computed. Other factors that affect efficient combustion are intimate mixing (or contact) of 

Whether efficient combustion is taking place or tiot is detenu itted by the actual amounts of CO, O2 or hydrocarbons present in the flue gas. Hence the analysis of the flue gas is of prime importance. 

A large excess of CO in the flue gas indicates incomplete combustion, which means amount of air supplied is not sufficient. A large excess of O2 in the flue gas indicates that air supply is much in excess. If both CO and O2 are sitnultaneously present in the flue gas in appreciable amounts, combustion is incomplete, irregular and non-uniform, and improvement in the design of the combustion chamber, furnace or engine is required. 

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Chlorine data are used in ultimate analysis to improve the estimate of oxygen by difference. The chlorine value is included in the sum of the items determined, which, when subtracted from 100, gives an estimate of the oxygen content of coal. 

The risk of spontaneous combustion during final preparation such as in silos/bunkers and mills also presents concerns in some cases. Properties that influence the propensity of coal to self-heat include volatile content, coal particle size, rank, heat capacity, heat of reaction, the oxygen content of coal, and pyrite content. The propensity of coal to self-heat and spontaneously combust tends to increase with decreasing rank. Thus, lignites and subbituminous coals are more prone to spontaneous combustion than bituminous coals and anthracites. 

Solid fuels, unlike gases and liquids, are entirely characterized by their composition. For example, coal can be characterized by its carbon, hydrogen, oxygen, sulfur, and nitrogen content. The water and mineral content of coal are also important means of differentiating coals from various sources. 

Figure 2 Activation energy for conversion to toluene solubles vs. total oxygen content of Argonne Premium Coal sample bank bituminous coals.

The oxygen content of the solid residue recovered from hydrogenation experiments of Phalen Seam coal at various hydrogen pressures are given in Table IV. The oxygen content was found to decrease from 6.63% for coal samples hydrogenated at 1.5 MPa to 2.54% for coal samples hydrogenated at 13.9 MPa. 

OXYGEN CONTENT OF PHALEN SEAM COAL HYDROGENATED AT 4500C FOR 3 HOURS AT DIFFERENT HYDROGEN PRESSURES... 

The sulphur content of coals, oils, tars, asphalts, etc., may be determined by combustion in an oxygen bomh, a little ammonium nitrate being added to the charge to ensure complete oxidation to sulphuric acid (see p. 136).5 After washing out the bomb the sulphur is determined as barium sulphate. 

Some coal analyzers use several gamma-ray detectors and operate by the use of neutron pulses. Such analyzers can measure the density and sulfur content of coal along with its heating value, moisture, and volatile matter content. This pulsed fast/thermal neutron analyzer can be self-calibrating and can determine such elements as carbon, oxygen, and sodium. 

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