Material balance with chemical reaction

material balance

1. Material balance with chemical reaction. Under the guidance of prof.karne madam AKSHAY GUNJAL (66) PAYAL KHANDAGALE (67) ARJUN PHAD (68) JAY JAWALGE (69) SHASHIKANT GAIKWAD (70)

2. Introduction Material balances are important first step when designing a new process or analyzing an existing one . Material balances are nothing more than the application of the law of conservation of mass, which states that mass can neither be created nor destroyed . They are used in industry to calculate mass flow rates of different streams entering or leaving chemical or physical processes

3. The General Balance Equation Suppose propane is a component of both the input and output streams of a continuous process unit shown below, these flow rates of the input and output are measured and found to be different . Process unit q in (kg propane/h) q out (kg propane/h ) Input + generation − output − consumption = accumulation

4. Procedure for Material Balance Calculations. Draw and label the process flow chart (block diagram). When labeling, write the values of known streams and assign symbols to unknown stream variables. Use the minimum number possible of symbols . Select a basis of calculation. This is usually the given stream amounts or flow rates, if no given then assume an amount of a stream with known composition . Write material balance equations. Note in here the maximum number of independent equations you can write for each system is equal the number of species in the input and output streams of this system. Also note to first write balances that involve the fewest unknown variables .

5. Balances on Reactive Systems Theory of proportions in which chemical compounds react is called stoichiometry . A statement of the relative number of moles or molecules reacting to produce products is given by a chemical equation known as stoichiometric equation . For example, 2 moles of SO2 and one mole of O2 react to produce 2 moles of SO3. Then the stoichiometric equation will be 2SO2+O2 →2SO3. Numbers that precede the formulas are known as stoichiometric coefficients . In a stoichiometric equation, the number of atoms in both sides of the equation must be balanced. Ratio of stoichiometric coefficients of two species is known as stoichiometric ratio EXAMPLE: 2SO2+O2→ 2SO3. What is the stoichiometric ratio of SO2 to SO3? Solution stoichiometric ratio of SO2 to SO3 =2 mole of SO reacted/2 mole of SO produced 2/2 = 1

6. The chemical compound which is present less than its stoichiometric amount, will disappear first. This reactant will be the limiting reactant and all the others will be excess reactants.

7. YIELD, SELECTIVITY&CONVERSION YIELD ×STOICHIOMETRIC FACTOR SELECTIVITY C ONVERSION × 100  

8. EXAMPLE 1 : Monochloro acetic acid (MCA) is manf . In a semi batch reactor by action of acetic acid with chlorine gas at 100°C in presence of PCl3 catalyst. (MCA) thus form will further react with chlorine to form di- chloro acetic acid (DCA).To prevent formation of DCA excess acetic acid is use. A small scale unit which reduce 5000 kg/day (MCA) required 4536 kg/per chlorine gas also 263 kg/day DCA is separated in crystallizer to get almost pure MCA product find %conversion, %yield of MCA & selectivity. SOLUTION: Basis: one day operation. REACTIONS: CH3COOH+CL2 → CH2CLCOOH + HCL (MCA) CH2CLCOOH+CL2 → CHCL2COOH+HCL (DCA) AA MCA DCA HCL CL2 AA HERE CL2 is limiting component. Molar mass AA=60 CL2=71 MCA=94,5 DCA=129

9. CL2 in feed=4536Kg/day therefore In moles =4536/71=63,88 kmol /day in feed. MCA in product = 5000KG/day In moles = 5000/94,5=52,91kmol/day in product. 1 Kmol of MCA = 1 Kmol of CL2 Therefore 52.91 Kmol of MCA = x Kmol of CL2 Therefore CL2 required to produce MCA = 52.91 Kmol DCA in product = 263 kg/day In moles= 263/129= 2.038 Kmol 1 Kmol of DCA = 2 Kmol of CL2 2.038 Kmol of DCA = x Kmol of CL2 Therefore CL2 required to produce DCA = 4.077 Kmol Therefore total CL2 consumed = 56.987 Kmol

10. % Conversion = CL2 utilized×100 CL2 in feed = =89.2 % Yield = Moles of desired product formed × Stiochiometric coeff Moles of spc reactant consumed = × 1 = 92.84 % Selectivity = = 52.91/4.078 = 12.9 %  

11. Application: Material balances considering reactions are used to design reactors. Material balance can also be used to identify the most efficient operation of reactor. Material balance provide data for yield, conversion and selectivity for particular reaction.

12. conclusion Material balance provide important information for the design of the plant. Firstly, different assumptions could be made for each equipment and streams based on the material balance. Design implications is done based on the calculation too. Material balance is required to calculate energy balance for the entire process.

13. Thank you !