Topic: Energy Balance Calculations | Process Calculations - Video Lectures

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  Course Summary:
  Quick Review of Theory and Solving Representative Problems on Chemical Process Calculations covering the undergraduate chemical engineering syllabus, and latest GATE-exam syllabus: Material balance without and with Chemical Reactions, Humidification and Saturation Calculations, Combustion Calculations, Energy Balance Calculations.
  
  Objective Type Questions and Problems with Detailed Solutions (70 nos.) as Video Lectures
  
  Topic-wise Interactive Self-Assessment Quizzes
  
  Questions from Past GATE Exams, and Standard Textbooks such as Felder, Himmelbalu, Bhatt & Vohra, etc.
  
  Videos: 13 hours of recorded lectures - 2.5 hours of Theory; 10.5 hours of Problem Solving
  
  This course is part of Chemical Engineering Video Lectures Bundle.
  
  Price of this course in Indian Rupees: 1,000 (6-months access from the date of purchase)
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Energy Balance Calculations

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Select activity Theory with Examples

Theory with Examples Page

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Select activity Condensation of Moisture from Air
Condensation of Moisture from Air Page

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Air at 38^oC and 97% relative humidity is cooled to 14^oC and fed into a plant area at a rate of 510 m³/min.

Calculate the rate at which water condenses _______ kg/min (round off to 1 decimal place)

Calculate the cooling requirement in tons (1 ton cooling = 12,000 BTU/h), assuming that the enthalpy of vapor is that of saturated steam at the same temperature and the enthalpy of dry air is given given by the expression: \(H \text{ (kJ/mol)} = 0.0291[T(^\circ)-25]\)
_________ ton of cooling (round off to 1 decimal place)

Vapor Pressure of Water: at 14^oC = 0.01597 bar; at 38^oC = 0.0662 bar.

Enthalpy of saturated steam (from steam table) at: 14^oC = 2527.2 kJ/kg; 38^oC = 2570.8 kJ/kg.
Enthalpy of water (from steam table) at 14^oC = 58.8 kJ/kg.
Select activity Steam Mixing

Steam Mixing Page

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Select activity Heat Released from Reaction

Heat Released from Reaction Page

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Select activity Adiabatic Flame Temperature of Natural Gas Combustion
Adiabatic Flame Temperature of Natural Gas Combustion Page
A natural gas containing 82 mole% \(\ce{CH4}\) and the balance \(\ce{C2H6}\) is burned with 20% excess air in a boiler furnace. The fuel gas enters the furnace at 298 K, and the air is preheated to 423 K.

The heat capacities of the stack gas components may be assumed to have the following constant values in J/(mol.K): \(\ce{CO2}\) = 50; \(\ce{H2O(g)}\) = 38.5; \(\ce{O2}\) = 33.1; \(\ce{N2}\) = 31.3.

Standard heat of formation values in kJ/mol are as follows: \(\ce{CH4}\) = \(-74.85\); \(\ce{C2H6}\) = \(-84.67\); \(\ce{CO2}\) = \(-393.50\); \(\ce{H2O(g)}\) = \(-241.83\).

Assuming complete combustion of the fuel, calculate the adiabatic flame temperature.

How would the flame temperature change if the percent excess air were increased?

How would the flame temperature change if the percent methane in the fuel were increased?
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Select activity Maximum Allowable Conversion of Exothermic Reaction

Maximum Allowable Conversion of Exothermic Reaction Page

2002-13-pc
Ammonia is produced by the following reaction\[ \text{N}_2 + 3\text{H}_2 \rightleftharpoons 2\text{NH}_3 \]In a commercial process for ammonia production, the feed to an adiabatic reactor contains 1 kmol/s of nitrogen and stoichiometric amount of hydrogen at 700 K. What is the maximum allowable conversion (in percentage) in the reactor, if the adiabatic temperature rise across the reactor should not exceed 100 K. Assume the feed and product streams to be ideal gas mixtures. The heat of reaction at 700 K for the above reaction is calculated to be -94.2 kJ/mol. Mean molar heat capacities (\(C_P\)), in the range 700 - 800 K, are 0.03, 0.0289 and 0.0492 kJ/mol.K for nitrogen, hydrogen and ammonia respectively.

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Select activity Heat Loss from the Combustion System

Heat Loss from the Combustion System Page

2014-42-pc

Carbon monoxide (CO) is burnt in presence of 200% excess pure oxygen and the flame temperature achieved is 2298 K. The inlet streams are at 25^oC. The standard heat of formation (at 25^oC) of CO and CO₂ are -110 kJ.mol^-1 and -390 kJ.mol^-1, respectively. The heat capacities (in J.mol^-1.K^-1) of the components are \[ C_{P_{\text{O}_2}}= 25 + 14\times10^{-3}T \qquad C_{P_{\text{CO}_2}} = 25 + 42\times10^{-3}T \] where, \(T\) is the temperature in K. The heat loss (in kJ) per mole of CO burnt is _______.

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Select activity Calorific Value of Fuels

Calorific Value of Fuels Page

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Select activity Adiabatic Mixing of Steam

Adiabatic Mixing of Steam Page

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Select activity Heat of Formation from Heat of Combustion Data

Heat of Formation from Heat of Combustion Data Page

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Select activity Heat Transferred from Reactor

Heat Transferred from Reactor Page

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Select activity Adiabatic Combustion of Methane

Adiabatic Combustion of Methane Page

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Isothermal Operation of Combustor to Convert Carbon and CO2 to CO Page

1997-13-pc

A feed at 1298 K, consisting of flue gas (\(\ce {CO2}\), \(\ce {O2}\) and \(\ce {N2}\)) and air, is passed through a bed of pure carbon. The reactions that occur both go to completion. \[ \begin {align*} \ce {CO2(g)} + \ce {C(s)} &\rightarrow 2\ce {CO(g)}, \quad \Delta H^\circ _R \text { at 298 K = 170 kJ/mol} \\
\ce {O2(g)} + 2\ce {C(s)} &\rightarrow 2\ce {CO(g)}, \quad \Delta H^\circ _R \text { at 298 K = \(-\)220.4 kJ/mol} \end {align*} \] The combustor is adiabatic and the product gases exit at 1298 K. Calculate the required moles of \(\ce {CO2}\) per mole of \(\ce {O2}\) in the feed stream, so that the net heat generated is zero and the bed temperature remains constant at 1298 K.
Data: Mean molar heat capacities, \(C_{Pm}\)

Substance	\(\ce{C}\)	\(\ce{O2}\)	\(\ce{CO}\)	\(\ce{CO2}\)
\(C_{Pm}\) (kJ/mol.K)	0.02	0.03	0.03	0.05

Select activity Heat Released from Combustion of CO

Heat Released from Combustion of CO Page

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Select activity Rate of Heat Removal from Ammonia Oxidizer

Rate of Heat Removal from Ammonia Oxidizer Page

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Heat Removed from Ammonia Oxidizer - Multiple Reactions Page

Ammonia is oxidized with air to form nitric oxide in the first step of the production of nitric acid. Tow principal reactions occur: \[ \begin{align*} \ce{4NH3} + \ce{5O2} &\rightarrow \ce{4NO} + \ce{6H2O} \\ \ce{2NH3} + \ce{2/3 O2} &\rightarrow \ce{N2} + \ce{3H2O} \end{align*}\]

A flowchart of the reactor follows.

Mean specific heat and standard heat of formation of components are given in the table:

Component	C_pm (25 to 150^oC) J/(mol.^oC)	C_pm (25 to 700^oC) J/(mol.^oC)	\(\Delta H_f^\circ\) kJ/mol
NH₃(g)	37.8	46.0	-46.19
NO(g)	30.2	32.0	90.37
H₂O(g)	34.1	36.9	-241.83
O₂(g)	30.1	32.4	-
N₂(g)	29.2	30.5	-

Calculate the required heat transfer to or from the reactor in kW.
Heat is to be ______ (removed from the reactor / added to the reactor)

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Select activity Temperature of Ammonia Oxidizer

Temperature of Ammonia Oxidizer Page

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Select activity Energy Balance for Production of Acetylene from Methane

Energy Balance for Production of Acetylene from Methane Page

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Select activity Exit Temperature of Flue Gas

Exit Temperature of Flue Gas Page

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Topic outline

General

Energy Balance Calculations