Material And Energy Balance

Material And Energy BalancePresented By: Ahmed NawazRoll No: 13CH153Supervised by:Professor Dr. Aziza AftaabWhy we study material and energy balance: Material and energy balances are very important in an industry. Material balances are fundamental to the control of processing, particularly in the control of yields of the products. The first material balances are determined in the exploratory stages of a new process, improved during pilot plant experiments when the process is being planned and tested, checked out when the plant is commissioned and then refined and maintained as a control instrument as production continues. When any changes occur in the process, the material balances need to be determined again.

The increasing cost of energy has caused the industries to examine means of reducing energy consumption in processing. Energy balances are used in the examination of the various stages of a process, over the whole process and even extending over the total production system from the raw material to the finished product.

Mass BalanceAmass balance, also called amaterial balance, is an application ofconservation of massto the analysis of physical systems. By accounting for material entering and leaving a system,mass flowscan be identified which might have been unknown, or difficult to measure without this technique. The exactconservation lawused in the analysis of the system depends on the context of the problem, but all revolve around mass conservation, i.e. thatmattercannot disappear or be created spontaneouslyEquation Of Material Balance

Types Of Mass Balance1.Differential BalanceDifferential balance focuses on the mechanism within the system.It is taken at one particular instant at a time.If the process is steady state, then the differential mass balance is same at any time.Differential mass balance represents a process stream and the mass flow rate of material.2. Integral BalanceIntegral material balance is taken at two instant at specific time. It describes how transference of material occurs over the time period between two intervals.

An integral balance is a black box approach which focus on the overall behaviour of system. It is generally applied to the beginning and end of batch process.Each Integral Balance represents a process stream and mass of material means it uses the amount of material no the rate of materials flowing.

Material Balance PlanningMaterial balancesare a method ofeconomic planningwhere material supplies are accounted for in natural units (as opposed to using monetary accounting) and used to balance the supply of available inputs with targeted outputs. Material balancing involves taking a survey of the available inputs and raw materials in an economy and then using a balance sheet to balance the inputs with output targets specified by industry to achieve a balance between supply and demand. This balance is used to formulate a plan for resource allocation and investment in a national economy.The method of material balances is contrasted with the method ofinput-output planningdeveloped byWassillie Leontief.

Steps for Material Balance:Draw a flow chart: a boundary must be established so that the material input and output can be determined.

Define Basis And Units : In order to determine the material balance, a basis of calculation must be defined and the uniformity of Units is mandatory.

Do the degree of freedom analysis: it provides the mechanism to check whether the material balance equation is solvable or not. Typically equations are soluble if the degree of freedom is 1.

Write the material balance equation:

Energy balance:Energy balance is basically the application of First Law of Thermodynamics that:Energy can neither be created nor destroyed, But It can change from one form to another.The main form of Energy is heat. Therefore practical applications of energy balances tend to focus on particular dominant aspects and so a heat balance, for example, can be a useful description of important cost and quality aspects of process situation. Heat Balances The most common important energy form is heat energy and the conservation of this can be illustrated by considering operations such as heating and drying. In these, enthalpy (total heat) is conserved and as with the mass balances so enthalpy balances can be written round the various items of equipment. or process stages, or round the whole plant, and it is assumed that no appreciable heat is converted to other forms of energy such as work.

Use Of energy balance In IndustriesEnergy Balance use as a facility in the energy system of Industry. There are various energy systems/utility services provides the required type of secondary energy such as steam, compressed air, chilled water etc. to the production facility in the manufacturing plant.

The Sankey Diagram and its Use

The Sankey diagram is very useful tool to represent an entire input and output energy flow in any energy equipment or system such as boiler generation, fired heaters, furnaces after carrying out energy balance calculation. This diagram represents visually various outputs and losses so that energy managers can focus on finding improvements in a prioritized manner.

Guidelines for the system involving both material and energy balance:Clearly identify the problem to be studied. Define a boundary that encloses the entire system or sub-system to be analysed. Entering and leaving mass and energy flows must be measured at the boundary. The boundary must be chosen in such a way that: a) All relevant flows must cross it, all non-relevant flows being within the boundary. b) Measurements at the boundary must be possible in an easy and accurate manner. Select an appropriate test period depending on the type of process and product. Carry out the measurements. Calculate the energy and mass flow. Verify an energy and mass balance. If the balances are outside acceptable limits, then repeat the measurements. The energy release or use in endothermic and exothermic processes should be taken into consideration in the energy balance.