reflection on reaction engineering
Chapter 1 : Introduction To Mole Balance
For this week, we did a recap on chapter one which is the mole balance. We developed mole balance equation for each reactor that we learnt which were batch reactor, CSTR, PFR, and PBR. Then, we were asked to do an activity of relating daily life reaction occurred into these four reactors and illustrated it in a mah-jong paper and recorded it in a video.
I felt the activity is nice because it help students to relate the theories we learnt in class can be applicable to real life. It is good to have that experience instead of relating the reaction occurred around us but also enhance our presentation skill throughout the video making. So, that’s all. Thank you.
Chapter 2 : Conversion and Reactor Sizing
DIY! Do it yourself. The activity was awesome. We could do our own reactor by recycling bottles and also strengthen bonding between group mates. In addition, this activity gave the real picture what the variables that affecting the rate of reaction between the coke and milk in different reactors.
For batch reactor, the variable that changing the rate of reaction is the duration of time (the rate of reaction increases with time) , for CSTR, the variable that need to be consider is the size of reactor ( as the bigger it is, the more the reaction ), for PBR, the weight of catalyst is the variable need to be considered, and lastly, for PFR, the length of the reactor is the variable need to be considered (the rate of reaction increases along the length of reactor).
Thus, as my opinion, this activity was very helpful to enhance my understanding on the types of reactor and how those variables work on the reactors. I am looking forward for the upcoming activities. Thank you :)
Chapter 3 : Rate Law and Stoichiometry
For this week, we had covered chapter 3 which is rate law and stoichiometric. It explained about the how to relate changes of moles of component to its conversion and set a basis which the limiting reactant. Besides, it covered the reaction order (determine the reaction is elementary or non- elementary), activation energy, the stoichiometric table in order to highlight the changes of moles of component after time t. Expansion factor is explained about the gas phase reaction changing the pressure inside the reactor by reacting or producing not in same amount which could be influence the volume of the reactor although the volume should be constant.
We have done a mind mapping session of each home group and we were asked to evaluate and observed the points on other’s mind map to know what points were missing in ours.
Thus, the mind map session really help me on memorizing the important points in chapter 3 and I really enjoyed it. Thank you.
Chapter 4 : Isothermal Reactor Design
Last week, we have learn about chapter 4 which is the isothermal reaction design. At first, in order to obtain rate constant, k we conduct experiment in a batch reactor. This is because we want to avoid limitation of mass transfer and energy distribution hence the value of k is reliable. Then we have learnt about designing the arrangement of cstr in series and parallel. From calculation, the cstr in parallel will get the same conversion as we conduct in a cstr reactor, assumes that the size and flowrate is the same. However, cstr in series will get higher conversion. Thus, it is more preferable. Next, we were introduced the damköhler number,Da, which the faster way to obtain the conversion of reaction. besides, we have learnt about the turbular reactor in how to design an isothermal pfr.
In class, we had done some exercise given by dr tazli and we had an activity which was doing mind maps and being explained by 4 representatives of class.
overall of chapter 4 activities were okay but at exercises part most of us can not get the real solutions.
That's all. Thank you
Chapter 5 : Collection & Analysis of Rate Data
Last week, we have learnt about analysing data using several methods. Methods used such as differential method, integral method, using initial rates and half-lives. In first class, we had an exercise how to used differential method in finding the order of reaction and its rate constant which were needed two graphs or using Finite Difference Method in order to find the order and rate constant; graph 1, and graph 2, . Based on graph 2, the slope is the order while interception on y-axis is to get rate constant. Integral method is a try and error method where we were needed to draw 3 graphs which were zero order, first order and second order graph. If the plot shows linear line, hence automatically it shows the order of reaction hence we find the k value by the graph’s slope.
Besides, we were also learnt about differential reactor by using flow reactor. In order to do that, we need to assume that change of concentration in reactor along the catalyst bed is small, low conversion which behaving isothermally- free from heat and mass limitation. The second class, we were had an activity which was called as fish-bowl activity where every groups need a representative to discuss on some exercises given in class before. Throughout this activity, we can observed and discuss what others findings and opinion in this type of questions and got some ideas to improve the data given.
The activity is good as students need to be more observant to find what was wrong in data given. Next, we were given an assignment which was constructing our own questions based on this chapter. And from that assignment, we can know what questions might come out in exams. That’s all. Thank you ;)
Chapter 6 : Multiple Reactions
In this chapter, we considering there are multiple reactions occur at the same time inside the reactor. We divided the reactions into desired reaction and undesired reaction. Desired reaction is the one we interested of its reaction and the products of it while undesired reaction is the reaction we want to avoid because it might produce the wrong product that we want in the desired reaction. Types of multiple reactions are parallel reaction – occurring at the same time, series reaction- occurring after first reaction, and independent reaction. Then, we learnt about the yield and selectivity as we need to calculate the yield and selectivity of desired over the whole reaction and the desired over the undesired reaction. Next, in this chapter, we need to know the case evaluation of the chemical reaction in order to come out with strategy to maximising the desired reaction and minimising the undesired reaction. There are two case evaluations which are when reaction order of desired is larger than undesired and the other one is when the order of undesired is bigger than the desired order. For case 1, we better used in high concentration of reactant, carry without inert and high temperature- gas phase, keep the inert dilute-liquid phase, used batch reactor or PBR reactor because initial reactor is high. For case 2, we need to keep the concentration of reactant low, using CSTR as it reduce the initial concentration into final concentration immediately and using recycle reactor.
Multiple reactions also depending on the reaction temperature where if the activation energy of desired is larger than Ea,U high temperature is preferable and vice versa. If the multiple reactions occurring in series reaction, the important term is residence time for the distribution for flow reaction and real time for batch reactor and also the concentration profile of the reaction.
The activities for chapter 6 are it was covered in PBL, problem based learning and we did some tutorial in class conducted by Mr Afiq. This topic encourages us to consider what the possibilities reactions occur for a chemical reaction are which actually happen in real life instead of knowing there is no other side reaction. So, we will come out with some strategies to get the maximum production of desired reaction. Thank you.
Chapter 8 : Steady State Non Isothermal Reactor Design
In this chapter, we do assuming that the reactor is an adiabatic where the net of heat transfer is equal to zero. Before that, we did some derivations of mole balance, rate law and Arrhenius equation and form energy balance equation where we found out that for non-isothermal operation, rate constant depends on temperature and affects the conversion and the temperature varies with volume of reactor. From general energy balance equation: accumulation= heat flow rate – flow work rate + rate of energy added into system + rate of energy leaving the system, we did derived another equation by combining the equations of reaction enthalpy and heat capacity components in the reaction to form energy balance equation in terms of conversion, flow rate, enthalpy and heat capacity. Then, we did an exercise in class to calculate the heat of reaction.in conclusion, chapter 8 is the derivations of equations of energy balance for adiabatic reactor. Thank you.