Chemical Properties Ultimate Analysis The ultimate analysis indicates the

Chemical properties ultimate analysis the ultimate

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Chemical Properties Ultimate Analysis: The ultimate analysis indicates the various elemental chemical constituents such as Carbon, Hydrogen, Oxygen, Sulphur, etc. It is useful in determining the quantity of air required for com- bustion and the volume and composition of the combustion gases. This information is required for the calculation of flame temperature and the flue duct design etc. Typical ultimate analyses of various coals are given in the Table 1.6. 1. Fuels and Combustion 9 Bureau of Energy Efficiency TABLE 1.6 TYPICAL ULTIMATE ANALYSIS OF COALS Parameter Indian Coal, % Indonesian Coal, % Moisture 5.98 9.43 Mineral Matter (1.1 × Ash) 38.63 13.99 Carbon 41.11 58.96 Hydrogen 2.76 4.16 Nitrogen 1.22 1.02 Sulphur 0.41 0.56 Oxygen 9.89 11.88 TABLE 1.7 RELATIONSHIP BETWEEN ULTIMATE ANALYSIS AND PROXIMATE ANALYSIS %C = 0.97C+ 0.7(VM - 0.1A) – M(0.6–0.01M) %H = 0.036C + 0.086 (VM–0.1xA) - 0.0035M 2 (1–0.02M) %N 2 = 2.10 – 0.020 VM where C = % of fixed carbon A = % of ash VM = % of volatile matter M = % of moisture Note: The above equation is valid for coal containing greater than 15% Moisture content.
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Storage, Handling and Preparation of Coal Uncertainty in the availability and transportation of fuel necessitates storage and subsequent handling. Stocking of coal has its own disadvantages like build-up of inventory, space constraints, deterioration in quality and potential fire hazards. Other minor losses associated with the storage of coal include oxidation, wind and carpet loss. A 1% oxidation of coal has the same effect as 1% ash in coal, wind losses may account for nearly 0.5 – 1.0% of the total loss. The main goal of good coal storage is to minimise carpet loss and the loss due to sponta- neous combustion. Formation of a soft carpet, comprising of coal, dust, and soil causes carpet loss. On the other hand, gradual temperature builds up in a coal heap, on account of oxidation may lead to spontaneous combustion of coal in storage. The measures that would help in reducing the carpet losses are as follows: 1. Preparing a hard ground for coal to be stacked upon. 2. Preparing standard storage bays out of concrete and brick. In process Industry, modes of coal handling range from manual to conveyor systems. It would be advisable to minimise the handling of coal so that further generation of fines and segregation effects are reduced. Preparation of Coal Preparation of coal prior to feeding into the boiler is an important step for achieving good combustion. Large and irregular lumps of coal may cause the following problems: 1. Poor combustion conditions and inadequate furnace temperature. 2. Higher excess air resulting in higher stack loss. 3. Increase of unburnts in the ash. 4. Low thermal efficiency. (a) Sizing of Coal Proper coal sizing is one of the key measures to ensure efficient combustion. Proper coal sizing, with specific relevance to the type of firing system, helps towards even burning, reduced ash losses and better combustion efficiency.
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  • Spring '17
  • Jerome Ramos

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