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30 June 2023, 6:53 PM

The first main topic that I learnt from the subject mass balance are the Chemical process and Process variables. As an engineer, we should able to design a process, that is the reason we should learn mass balance. Before entering this subject, we did learn some basic calculation such as the conversion unit from the ITE in Year 1 Semester 1. This made me easier to understand when the Dr is teaching the topic of process variable and become more clearer due to the detail explanation from Dr. After that, we enter the topic of Introduction of Chemical process which a lot of new things for us. From this topic, we should able to describe the overall schematic of chemical plant and explain the general function of each component. We also need to identify each separation process and elaborate the concept of each separation process and differentiate between them such as evaporation, liquid-liquid extraction, absorption, adsorption and so on. When I first touching this chapter, it’s a bit stressful for me since everything is new for me and there are lot of unit process should be memorised. Even this is just the first chapter, but I did put a lot of afford on it such as doing the assignment that given by Dr. to make myself have the deep understanding to each process unit and improve my problem-solving skill. Every time done a chapter, Dr. will give us a quiz to make sure that we are able to solve it and its also a training for me to make sure that I am able to solve the question on time. This helps me in saving lot of time in doing the Test since we just have only 2 hours to solve three questions.

The next main topic is the Material balance calculation. In this chapter, it is divided into two parts which are the single unit process and multiple unit process. In this chapter, we learnt to draw the process flow diagram, the symbol, the ways to write basis and the important of basis in a calculation. We need to utilize the knowledges that we learnt from the previous topic and used it in this chapter. For example, we are given a question, we need to analyse which unit process is fit to this question and how many stream should occur in this unit system and the component that will come out in that specific stream. We should use the material balance equation to calculate the composition of each component and also the amount of each stream. Before carry out the calculation, there is a very important thing should do which is analysis the Degree of Freedom (DoF). This DoF is a very important step because it can be told whether the question can be solved or not. There is a zero when the question is able to solve. In multiple unit processes,  there might be occur the process of recycle and by pass. These processes are to recovering unconsumed reactants and control the compositions of the product respectively. Besides, we should identify the overall boundary and the boundaries to each unit processes when there is a multiple unit process to ease us in calculation. The DoF should be carry out to each boundary to identify which boundary is suitable to use as the first calculation. The big challenge for me in this chapter is the words or the sentences given in the question is difficult to be understand. It makes me put a lot of time in just to understand what the question wants us to do and I even do the wrong things after putting lot of afford to understand the words. I’m a person who often doing the careless mistake so I will be nervous every time I see the long question, I’m scared that I will lose some important information and cause me unable to get the correct answer. This concern can be proved in my assignment, quiz and also my Test 1. I have been deducting a lot of marks in this chapter due to some careless mistake and also my weak understanding skill. I have a bad experience in my Test 1 because I received a bad result in Test 1. I did compare the calculation steps with my teammate and I noticed that lot of careless mistakes is done and I have misunderstood the question and carry out the wrong calculation in the first step. I feel disappointed to myself but at the same time I notice my weakness. To repair this weakness, I start to train myself to improve my analysis skill. I did a lot of past year question and try to analysis the question until I able to receive the correct answer. When I met the problem, I will seek help from my teammates and we will discuss it together. This action helps us to improve our communication skill and also the teamwork. I am appreciating that my teammates and course mate that help me in solving the problem.

Furthermore, we also learnt the material balance calculations for reactive systems. This chapter is a bit different from the previous material balance because it is involving the chemical reaction. In a chemical reaction, there is limiting reactant and excess reactant. We need to classify which reactant is limit and which is excess hence calculate the fractional excess of that reactant and the fractional conversion of the reacted component. There is three ways to calculate the composition of a reactive system which are extent of reaction, molecular species balances, and atomic species balances. Each methods have their own DoF analysis. For example, the DoF analysis using the molecular species balance is number of unknowns plus number of independent chemical reactions and minus the number of independent molecular species balances and minus the number of other equations relating unknown variables. The general balance at steady state of this method is input plus output equals to output plus consumption. From these three methods, I more prefer using the extent of reaction since it is the easiest method to use and it use the least of time in the calculation. However, I still need to familiar myself with other two methods to make sure that I can solve the question when asking to use the method other than the extent of reaction. As regular, Dr. will give us the assignment to help us have a deep understanding to this chapter and also the quiz for us to make sure we are able to solve it. Since this course is come to the middle of the process, we are almost familiar ourself in the mass balance calculation. So, this chapter will be easier for us since the calculation steps are almost the same. Our Test 2 is cover to this chapter and I have received a better result compare to my Test 1. This meant that all my efforts have paid off.

There is a team mini project that assigned to each of the team. The team mini project is related to the material balance calculation of  multiple unit processes and reactive system. In this mini project, we need to solve the question using the information given and the knowledges we learnt hence perform it using Microsoft Excel. Me and my teammates are first analysis the problem and all of us have drafted out the process flow diagram based on the given process description and then we compare our answers until we get the best diagram we want. After that, we start our discussion and calculation. We first draw all the boundaries and do the DoF analysis to classify which boundary is suitable be use in  the first calculation. After a strong discussion, the first boundary use for calculation is the reactor. Since this is a reactive system, our team need to decide one of the three methods to calculate the composition in the reactor. We decide to use the extent of reaction in this calculation since all of us agree that this method is the simplest method and the method with least time in calculation. After done all the calculation, we start to key in the answer in the Microsoft Excel. First of all, me and my teammates are refusing to take this part of job since all of us do not have this knowledge. To prevent my teammates being stress, I take this part of job even though I have no experience in doing the Microsoft Excel. I kept searching the technique from internet and YouTube, I notice that Microsoft Excel is just a simple work and it is really bringing lot of convenience to us in complete our job. We just need to key in the formula and all the answers will come out directly. After I learnt the formula that might be use in our mini project, I did teach my teammates and telling them it is just a simple work. After my teammates seeing how it work,  they also can work well using Microsoft Excel. Then, we start assign the task such as drawing the PFD, draw the table, doing the calculation and so on. With this task distribution, we did complete our work in time and efficiently. After submit our project, there is a presentation section that held by our Dr. in class to train our presentation skill. This is a good chance for me to train my presentation skill and problem-solving skill because there is a question-and-answer part after we done our presentation in the class. From this activity, I did learnt lot of precious skill such as teaching skill, problem solving skill, communication skill, exploring skill, cooperation skill, Microsoft Excel skill such as data interconnection technique that will be useful to mu future working life. I am happy with this experience since I have the most cooperative teammates, we face the problems, solve the problem, and learn from the mistake together. We help each other to become better.

The last main topic are single phase system and multiphase system. In single phase system, the problem often arise that call for determining the value of one of the variables from P, T, V, and n. If the given gas is an ideal gas, the ideal equation can be used directly where PV=nRT. However, if the provided gas is not an ideal gas, there are three equations of state for the calculation which are virial equation of state, cubic equations of state, and the compressibility factor equation of state. T basis of the generalized compressibility charts is the law of corresponding states, an empirical rule stating that the compressibility factor of a species at given temperature and pressure depends primarily on the reduced temperature and reduced pressure. After the quantities have been determined, we need to use the chart to determine the z hence substitute the value into the compressibility factor equation to solve the unknows. For non-ideal gas mixtures, Kay’s rule is used. The pseudocritical constants should be determined by weighing the critical constants for each mixture component by the mole fraction of the component in the mixture. In multiphase system, two phases in contact with each other are said to be equilibrium when the temperature, pressure, composition, and all other variables that characterize each phase do not change with time. Different from the previous chapter we learnt, the Gibbs phase rule give the DoF of a multiphase system in equilibrium. For a gas at temperature T and pressure P containing a single condensable vapor with mole fraction y and vapor pressure, Raoult's law provides the basis for a number of definitions. If Raoult's law is satisfied, the vapor is saturated, if the vapor pressure less than saturation vapor, the vapor is superheated. If A is saturated and either the temperature is decreased or the pressure is increased, A will begin to condense. The bubble-point temperature of a liquid mixture is the temperature at which the first vapor bubble forms if the mixture is heated at constant pressure. The dew-point temperature of a vapor mixture is the temperature at which the first liquid droplet forms if the mixture is cooled at constant pressure. For the single-phase system, it is simpler to be understand than that multiphase system since it just need to substitute the value into the equation and hence get the answer. However, for the multiphase system, it is more complicated and I still need time to digest it since it is another new thing for me. Sometimes it still makes me confuse when I am doing the revision to this chapter. So, to make myself more familiar with this chapter, I will do a lot of research and exercises and getting a good result in my final exam.

In conclusion, Dr. and the topic of mass balance have taught me a lot of new information. From every angle, both directly and indirectly, it aids in my improvement.  I am grateful and overjoyed to have learned things that will help me in my future career. Even if the road may be difficult, everything will be doable.