Meeting with Prof. Bill

Today the whole FYP team met up with Prof. Bill.

Presentation & ROSA:

From ROSA, we can see the trend of the % recovery and salt rejection.

Increase of pressure will cause an increase in permeate flow rate, decrease in permeate concentration etc.

Suggestions from Prof. Bill:

• type of membrane used for the experiment need to be found out
• conductivity VS concentration at each temperature should be compared with those in the handbooks
• the built up of salt on the membrane will cause the water molecule to have difficulty to pass through the membrane (salt built up will diffuse back to the main feed stream)
• increase in flow rate (keeping the other variables constant) will increase in shear; decreasing the thickness of the concentration boundary
• Material Balance must be performed to compare with our experimental results

Membrane Characterization System:

We are told that the membrane that we used are for microfiltration.

The pore size of the membranes are too big. Salt particles can pass through it.

Hence, osmosis is not achieved.

• Chemical Potential Difference causes mass transfer between the DI water and concentrate.
• Both the water and the concentrate level need not cover the whole membrane.

We concluded that we would use a RO membrane (which we will get from Dr. Chong) to test it out again.

Vendor's P&ID:

• 1 low pressure feed pump
• 1 high pressure booster pump
• Pressure Reducing Valve between RO and NF1 (cheap and easily available)

Membrane Characterization System Experiment

Today, some of us conducted the experiment on theMembrane Characterization System Experiment in W314 lab.

The objective of this experiment is to study the osmotic pressure and resistance of different types of membranes.

Theoretically, we can calculate the osmotic pressure using this formula:

π = MRT

π- Osmotic Pressure

M- Concentration

R- Universal Gas Constant

T- Temperature

We want to prove that the experimental results would tally with theoretical value that we have calculated.

However, we couldn't get any results due to the following problems:

• we couldn't measure any voltage because there wasn't any point for us to connect the multimeter to the electrode
• there isn't any significant change in the water level, hence we couldn't calculate the osmotic pressure
• we cannot measure the conductivity because the conductivity was out of range for the conductivity meter

These are the possible causes which might have caused the problems to occur:

• the membrane; wrong placing of the membrane
• the salt solution is too concentrated for the osmosis phenomena to occur

Mass update (August 2009)

After the visit to Dr. Ziggy SMTC lab in NTU, the design team improved on the previous P&ID. Here is the final P&ID design:

We had a meeting on 31st July with the other 9 members and Mr. Ting to research on soem patents and extract some of their ideas and industrial concepts. This will help us to familliarise with RO pilot plant designs, as well as to compare them with industrial standards and our vendors' designs.

Patent #1:

Some pointers of the patent:

-2 stage RO membrane

-high pressure and recovery

-prevent scale formation

-1st stage(low pressure)

-2nd stage(high pressure, hardness compound removed)

Patent #2:

Some pointers of the patent:

-Two stage seawater desalination system that includes first and second stage high performance

-NF membranes in series flow relationship

-First stage membrane being pumped with seawater pressurized sufficiently to produce a firs permeate and a first reject

-Second stage membrane being pumped with first permeate between 200-300 psi to produce potable water and second reject

Patent #3:

Some pointers of the patent:

-The supply of seawater at low pressure creates no/a little permeate flow through the RO

membranes

-The seawater flushes the feed side of the RO to the NF element where significant permeate flux

occurs

-NF permeate depleted in divalent ions and optionally depleted in monovalent ions

Before our examinations, we presented what we have done for the project (so far) to Professor Bill

when he visited us. After some dicussion with the professor and lecturers, we have encountered

new problems in out design and intend to improve on it before the final design is made by the

vendors.

6 - 17 July update

After the holidays and MST, we (Farhana and weilu) met Ms Yau to discuss on how we can further improve and model our design using pressure concepts on pipes, industrial designs of RO pilot plants, etc.

However, the other group members' have informed us on 10 July 2009 (according to their supervisors) that the design stage is over. The supervisors are now at the final stage of design and will (or might have already) be ordering the pilot plant for us. So tentatively, we do need to work on the design stage/run any tests.

Thus, our group will be focusing on our FYP report instead, concluding what we have done so far in our report for the first term by the end of July.

Week 5 of school (18 May 09 to 24 May 09):

Membrane Characterisation (Cheryl):

Here are some pictures taken when we cut up two spiral wound membranes so learn about how the inside of the membrane looks like. The first one has never been used before, thus it has dried up and can never be used. It has a 1-inch diameter.

The second membrane was previously used in W314 to run experiments. It was not used for a few years, so some brown substance was formed in the membrane. It is probably biofouling, although it may also be rust from the pipes before the membrane module. This membrane has a 2.5-inch diameter.

Week 6 of school (25 May 09 to 31 May 09):

We went to NTU's Singapore Membrane Technology Centre (SMTC) on Friday 29 May to learn more about RO systems and get an idea on what we are missing in our pilot plant. Dr Ziggy gave us a lot of details to work on.

From SMTC's pilot rig, we learned that water will increase in temperature after passing through the membrane. Thus, when recycled, we will need a chiller to reduce the temperature of the water as too high a temperature would be detrimental to the membrane modules, and performance would decrease.

For the design team, we had copy down the brand of equipments used in the membrane test kit so that we can do some research on it. Our design group has also asked Dr. Ziggy’s opinion regarding our current design (design is in the previous entry) and from his feedbacks we have to start again on our design.

First Phase

For the last two weeks, we have split up into our 3 groups (as mentioned earlier):

Design (Farhana):

On 8 May 2009, I had met with the members from other team to discuss on the design of the multistage RO/NF system for this project. I was not sure what I was supposed to do at first as I did not attend the briefing held on 24 April 2009 (1^st week). I knew that the design team has to design a 3 stage system with an ultimate aim to reduce the operating cost and the fixed capital through the modification of the conventional process.

Before this meeting, the design team leader had asked me to come up with my own design PFD with the necessary instruments in the design. While designing it, I missed out an important consideration in mind which is my design should be having different feed location because my group task is to find the optimum feed location using brackish water. On that day itself, I had to redesign my design. The design team, after much discussion, had come with the final design. We had shown Mr. Adrian and Ms. Ng the final design and they had given us their feedbacks. The feedback they give is that we should consider pressure required to the RO unit, putting the flow indicator on the low pressure side and they also shows us some configurations that we should have. There are quite a lot of amendments to be made. So the following day, the team had met up again to make changes with the design.

 

On 15 May 2009, the design team had presented the finalized design of the RO/NF system to Ms. Ng, one of the supervisors of the project, Dr. Adrian and Dr. Chong  from NTU. They commented that our design was too complicated as the instruments/equipments were not tagged plus there were missing streams or streams that had no purpose. Hence, Ms. Claire had asked the team to focus on three configurations first before we add our own configurations as well in the design. So currently, the design team is focusing on these three configurations. Here is the current design:

Design Team's P&ID

Membrane Characterisation (Cheryl):

My team met on 8 May 2009 with the intention of running one of the membrane pilot plants that we have in W314. However, the plant was not ready to run die to some technical diffuculties. Thus, we decided to make use of the time to design the new membrane characterisation plant's P&ID, as well as to come up with the procedures for it.

However, when we presented our proposal to Ms. Ng, Dr. Adrian and Dr. Chong on 15 May, they mentioned that we were missing some safety relief vales in our design, as well as other minor factors. In addition, the membrane modules and pumps provided by the vendor was quite costly, so we might need to come up with alternatives by the next meeting next Friday. Meanwhile, we have improved our design to this:

Modelling (Wei Lu):

Our group was supposed to meet up on 6th May to discuss. However, due to some problems, we did not hold the meeting. Hence, we went home and tried on the case studies given to us.

The next meeting was on 15th May. Our modeling group presented on the calculations we did and due to the misleading configuration, we had to redo everything. We tried to use the new design from the design group and state assumptions. After which, we started to find the unknown values (for the recovery and rejections) using the assumptions made. We all tried out and are still trying out to get the values correct if possible.

Initial Research

Week 1 & 2 of school (20 April 09 to 03 May 09) 

During these 2 weeks, we had been exploring on membrane technology using the guide that Ms Yau had given us. Ms Yau helped us to kickstart our FYP research by providing us with guidance on what topics we should explore, as well as what to focus on at this point of time. Since we were going to purchase DOW membranes, we read up and attained a basic understanding of Reverse Osmosis (RO).

We started by learning methods of research by the SP's Student Advisory Service by the school library. The librarian taught us how to use the school's catalogue, as well as searching e-book databases that were extremely useful in our research. We managed to obtain a lot of information thereafter.

Although we were unable to borrow one of the books that Ms Yau had recommended to us (Membrane Technology and Applications and Membrane Technology and Applications) as they were not available,We were unable to research on other types of membrane processes in depth. Hence, we focused on reverse osmosis and nanofiltration membrane processes only.

Then, we had divided different tasks among our group members such that each member will focus on different topics and provide the information to the other members.

Farhana would be in the design team, collaborating with the supervisors and doctors from NTU to design out pilot plant. Cheryl will be in the membrane characterisation team, running tests on modules to get an idea on how would the RO and NF modules would react with varying parameters for each run. Weilu was assigned to the modelling team, which would make use of calculations and microsoft excel to give us the theoretical yield, purity and other parameters of the products.

Introduction

This blog was created by Cheryl, Farhana and Weilu for our logbook entries for Final Year Project (FYP). Entries would be posted fortnightly about our project's progress. However, the first two entries would be posted by this weekend as it is for the first four weeks of school ( 20 April 2009 - 3 May 2009, as well as 4 May 2009 - 17 May 2009).

Please visit us fortnightly for updates. :D