FAQ on Process Calculation
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This document provides definitions and explanations of key concepts in process calculation: - Gram mole is the ratio of substance weight in grams to its molecular weight. Normality is moles of solute per liter of solution. Molarity is moles of solute per liter of solution. Molality is moles of solute per kilogram of solvent. - A stoichiometric equation shows theoretical moles of reactants and products. The limiting reactant is the first to be used up. Excess reactant remains after the reaction. - Conversion is reacted reactant over initial reactant. Yield is product from desired reaction over total reacted. Selectivity is desired over undesired product. - Recycle and bypass
FAQ on Process Calculation
- 1. FAQ on PROCESS CALCULATION Prepared by- Mr. Vishal B. Thakare (M.Tech Chemical, SVNIT Surat) Assistant Professor, PARUL UNIVERSITY Vadodara vishalbt88@gmail.com
- 2. Gram mole- It is the ratio of weight in gram of substance to molecular weight of substance. Weight in gram of substance B Molecular weight of substance B Normality- It is defined as the number of gram equivalent of solute dissolved in one liter of solution. gram equivalent of solute Volume of solution in liter Mass in gram of substance Equivalent weight of substance Gram moles of compound B = Normality (N) = gram equivalent of solute =
- 3. Molarity- It is defined as the number of gram moles of solute dissolved in one liter of solution. gram moles of solute Volume of solution in liter Molality- It is defined as the number of gram moles of solute dissolved in one kilogram of solvent. gram moles of solute mass of solvent in Kg Molarity = Molality =
- 4. Stoichiometric Equation- It indicate theoretical moles of reactant and product. Ex. CO + 2H2 CH3OH From Stoichiometry of reaction 1 Kmol CO = 1Kmol CH3OH = 2Kmol H2 28 Kg CO = 32 Kg CH3OH = 2 Kg H2 Limiting Reactant- It is reactant that disappear first during course of reaction. It is always present in less than its stoichiometric proportion.
- 5. Excess Reactant- It is defined as the reactant which present in excess of its theoretical or stoichiometric requirement. It is specified in terms of % excess. Moles of B fed – Moles of B theoretically required * 100 Moles of B theoretically required Ex. Consider the reaction SO2 + O.5 O2 SO3 If 100 mol SO2/hr. and 75 mol O2/hr. are fed to reactor then 75-50 50 = 50 % excess of B = % excess of O2 = *100
- 6. Conversion- It is the ratio of amount of reactant reacted to the amount of reactant charged or fed to the reactor. moles of A reacted moles of A charged or fed to reactor Yield- It is the ratio of moles of reactant reacted to produce desired product to the total moles of reactant reacted. Consider the reaction A C (desired product) A D (undesired product) % conversion of A = *100
- 7. moles of A reacted to produce C Total moles of A reacted Selectivity – Selectivity is the ratio of moles of desired product formed to the moles of undesired product formed. moles of desired product formed (C) moles of undesired product formed (D) * 100 Yield of C = Selectivity =
- 8. Recycle Operation- To obtain desired concentration product, product stream again recycled to the feed stream. Recycle ratio = R/F
- 9. Ex. In distillation operations, a part of the distillate is fed back to column to enrich the product, so that almost pure product can be obtained. In drying operations, a major portion of the hot air leaving the dryer is recirculated to conserve heat to utilize the heat being lost in the exit air.
- 10. By Pass Operation- To obtain desired concentration product, some of feed is directly connect to product stream. Purge Stream- Presence of impurities in mixed feed beyond certain limit may lead to decrease in conversion or may favor side reaction. In such cases accumulation of inerts or impurities can be avoided by blending off/ purging fraction of recycle feed. By pass stream Process Unit Product Feed
- 11. Recycle Feed R Fresh Feed F Mixed Feed M Purge P Product SeparatorReactor Purge ration = P/R Purge ratio based on any component ‘A’ = ‘A’ in purge/ ‘A’ in recycle feed
- 12. Combustion- The rapid reaction of fuel with oxygen is called combustion. When fuel burned, the carbon in the fuel reacts to form CO2 or CO, hydrogen reacts to form H2O and Sulphur reacts to form SO2. A combustion reaction in which CO is formed is referred as partial or incomplete combustion.
- 13. EXERCISE 1) Define a) Heat capacity b) Heat of formation c) Heat of combustion d) Proximate analysis of coal e) Ultimate analysis of coal 2) State the Ideal gas law.