CHAPTER 4: FUNDAMENTALS OF MATERIAL BALANCE Prepared By: Waleed Alanazi Contact me: s201920270@kfupm.edu.sa Twitter: @wvpo17 4-1: PROCESS CLASSIFICATION ◦ Chemical processes may be classified as: ◦ Batch processes ◦ Continuous processes ◦ Semi-batch processes ◦ Also, the processes can be either: ◦ Steady-state: ◦ Does not change with time (remine constant) ◦ Unsteady-state (Transient) ◦ Change with time (at different time different value) ◦ The next slides will describe each process. PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 ◦ Batch Process: ◦ A batch process is a type of chemical process in which a fixed amount of reactants are fed into a reactor and then converted into products. ◦ The products are then removed from the reactor and the process is repeated with a new batch of reactants. Batch processes are often used for small-scale production, specialty chemicals, or when the reaction conditions need to be changed frequently. Step 1: input Step 2: mix or react Step 3: output PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 ◦ Continuous Process: ◦ A continuous process is a type of chemical process in which the input materials are constantly fed and the output products are continuously removed. ◦ Unlike a batch process, which operates in discrete cycles, a continuous process runs uninterrupted for long periods of time. Continuous processes have many advantages, such as higher productivity, lower operating costs, and consistent product quality. mix or react Input All at the same time Output PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 ◦ Semi-Batch Process: ◦ A semi-batch process in chemical engineering is a type of operation that combines features of batch and continuous processes. In a semi-batch process, some reactants are added or some products are removed during the reaction time, while the rest of the reactants are initially charged in a single stirred tank. Semi-batch processes can offer advantages such as improved selectivity, better control of exothermic reactions, and product removal to minimize reversibility. Step 1: input Step 2: mix or react at same time output is taking out Output PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 4-2: BALANCES ◦ The General Balance Equation: ◦ mathematical expression that describes how mass or energy changes in a system. It is based on the principles of conservation of mass and energy, which state that matter and energy cannot be created or destroyed, only transformed. 𝑖𝑛𝑝𝑢𝑡 + 𝑔𝑒𝑛𝑒𝑟𝑎𝑡𝑖𝑜𝑛 − 𝑜𝑢𝑡𝑝𝑢𝑡 − 𝑐𝑜𝑛𝑠𝑢𝑚𝑝𝑡𝑖𝑜𝑛 = 𝑎𝑐𝑐𝑢𝑚𝑢𝑙𝑎𝑡𝑖𝑜𝑛 Anything enters the system through the boundaries Anything produced within the system Anything leaves the system through the boundaries Anything consumed within the system Anything Build up within the system PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 ◦ Type of balances: ◦ Differential balances: ◦ are used to analyze the behavior of a chemical process in a small region or over a short time interval. They are based on the principle of conservation of mass, energy and momentum, and they involve the use of partial differential equations. Differential balances can be applied to various types of systems, such as batch, continuous, steady-state or transient processes. ◦ Integral balances: ◦ that apply to a whole system or process, without considering the spatial or temporal variations within it. They are useful for calculating the overall input and output of mass, energy, or other quantities in a chemical process. PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 ◦ Rules to simplify the material balance which can be combined: ◦ If the balance quantity is total mass, then: ◦ Generation = 0 , Consumption = 0 ◦ 𝑖𝑛𝑝𝑢𝑡 − 𝑜𝑢𝑡𝑝𝑢𝑡 = 𝑎𝑐𝑐𝑢𝑚𝑢𝑙𝑎𝑡𝑖𝑜𝑛 ◦ If the balance substance is nonreactive species, then: ◦ Generation = 0 , Consumption = 0 ◦ 𝑖𝑛𝑝𝑢𝑡 − 𝑜𝑢𝑡𝑝𝑢𝑡 = 𝑎𝑐𝑐𝑢𝑚𝑢𝑙𝑎𝑡𝑖𝑜𝑛 ◦ If the system is steady state, then: ◦ Accumulation = 0 ◦ 𝑖𝑛𝑝𝑢𝑡 + 𝑔𝑒𝑛𝑒𝑟𝑎𝑡𝑖𝑜𝑛 − 𝑜𝑢𝑡𝑝𝑢𝑡 − 𝑐𝑜𝑛𝑠𝑢𝑚𝑝𝑡𝑖𝑜𝑛 = 0 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 ◦ Balances on continues & steady state process: ◦ 𝑖𝑛𝑝𝑢𝑡 + 𝑔𝑒𝑛𝑒𝑟𝑎𝑡𝑖𝑜𝑛 − 𝑜𝑢𝑡𝑝𝑢𝑡 − 𝑐𝑜𝑛𝑠𝑢𝑚𝑝𝑡𝑖𝑜𝑛 = 0 ◦ If the balance contain nonreactive species or total mass then, ◦ 𝑖𝑛𝑝𝑢𝑡 − 𝑜𝑢𝑡𝑝𝑢𝑡 = 0 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 EXAMPLE PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 You need to know how to draw this diagram it makes everything easier PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 4-3: MATERIAL BALANCE CALCULATIONS ◦ The best way to do material balance calculation is to draw a Flowchart. ◦ Steps to Draw Flowchart: ◦ Write the values and units of all given (known) stream variable at the location of the streams on the chart. ◦ EXAMPLE: ◦ Assign symbols to unknown stream variable and write these variable names and their associated units on the chart. ◦ EXAMPLE: PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 ◦ Degree of freedom analysis (DOF): ◦ is a method to determine the number of independent variables that can be varied in a system without violating any constraints. It is useful for solving problems involving equilibrium, kinetics, thermodynamics, and other fields of engineering and science. The degree of freedom of a system is equal to the difference between the number of variables and the number of equations or relations that describe the system. ◦ To perform DOF: ◦ Draw and completely label flowchart ◦ count the unknown variables. ◦ Count the independent variables. ◦ DOF = number of unknown – number of independent variables. ◦ If DOF = 0 then the problem, can be solved ! ◦ If DOF > 0 then underspecified, more information need to solve the problem. ◦ If DOF <0 then the problem is overspecified. PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 ◦ Sources of equations relating to unknown process stream variables: 1. Material balance 2. Energy balance 3. Process specification 4. Physical properties and laws 5. Physical constrains 6. Stoichiometric relation. PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 EXAMPLE PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 4-4: BALANCE ON MULTIPLE UNIT PROCESSES 4-5: RECYCLE & BYBASS 4-5: RECYCLE & BYPASS 4-6: CHEMICAL REACTION STOICHIOMETRY 4-7: BALANCES ON REACTIVE PROCESSES 4-8: COMBUSTION REACTIONS 4-8: COMBUSTION REACTIONS ◦ بالطريق PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 SELECTED QUESTIONS Solved by: Zaher Alshayeb PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or twitter: @wvpo17 PREPARED BY: WALEED ALANAZI , FOR CONTACT: S201920270@kfupm.edu.sa Or 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