Dec 27, 2016 - This experimental investigation focuses on the optimization of the reverse osmosis membrane filtration process for the production of ultrapure ...
REVERSE OSMOSIS OPTIMIZATION | Student ID: 012181
REVERSE OSMOSIS OPTIMIZATION Evaluating Temperature and Pressure Manipulation to Optimize the Reverse Osmosis Membrane Filtration Process in Ultrapure Water Production for Usage in the Electronics and Semiconductor Industry RO Optimization of UPW Production from Influent Municipal Water Supply Studying the Effect on Conductivity, Total Dissolved Solids, pH, and Product Volume.
SOR:
PROF.
Module Convenor: Dr. Faye Siew Hui Chong
CHONG MEI F
Supervisor: Prof. Chong Mei Fong Student ID: 012181 Group: B3 Laboratory Equipment: Membrane Filtration Unit Submission Date: 27th December 2016
ONGSTUDENT ID: 012181GROUP: B3EQUIPMENT: ME
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REVERSE OSMOSIS OPTIMIZATION | Student ID: 012181 Table of Contents 1.0 Executive Summary ...................................................................................... 3 2.0 Introduction ................................................................................................. 4 2.1 Aim .......................................................................................................... 4 2.2 Objectives ................................................................................................. 4 2.3 Hypothesis ................................................................................................ 5 3.0 Literature Review .......................................................................................... 6 4.0 Experimental Approach .................................................................................. 9 4.1 Equipment, Apparatus and Materials ............................................................. 9 4.2 Experimental Procedures ............................................................................. 9 4.2.1 Membrane Filtration Operation ..............................................................10 4.2.2 Water Quality Testing ...........................................................................11 4.2.3 Sample Storage and Disposal ................................................................12 5.0 Data Analysis and Interpretation ....................................................................13 6.0 Conclusion ..................................................................................................20 7.0 Appendices..................................................................................................21 7.1 Safety Assessment ....................................................................................21 7.2 Appendix: Module Planning .........................................................................28 7.3 Abbreviations............................................................................................29 7.4 ASTM Standards for UPW Water ..................................................................29 7.5 Schematic Process Diagram ........................................................................32 7.6 Excel Datasheet, Calculations and Additional Graphs .....................................33 8.0 References ..................................................................................................40 9.0 Acknowledgements ......................................................................................41
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REVERSE OSMOSIS OPTIMIZATION | Student ID: 012181 1.0 Executive Summary This experimental investigation focuses on the optimization of the reverse osmosis membrane filtration process for the production of ultrapure water that is to be utilized in the semiconductor industry. The optimization parameters being studied are temperature and pressure since the twin aims of this study are to provide the highest flux of ultrapure water at the lowest possible financial cost without compromising on ultrapure water quality specifications. Ultrapure water is crucial for the water usage intensive semiconductor manufacturing processes because the water used during the manufacturing process for semiconductor washing and rinsing must be sufficiently free of contaminants to ensure that defects are not produced in the wafer. The role of RO (Reverse Osmosis) in the production of UPW (ultrapure water) is strictly defined for the feed water and permeate specifications. RO as a single water treatment process cannot efficiently deliver UPW, therefore the reverse osmosis unit in the UPW production plant will be fed with water after the pre-treatment stage. Since the RO unit at an UPW production plant is in the intermediate stage (right after pre-treatment, but before polishing) it has certain requirements for the RO feed water. To reach the high specifications of UPW it is best to use water that has been purified and filtered to a certain degree, thereby reducing the need for higher pressurizing due to the system having to overcome the higher osmotic pressure if a less “pure” water feed is utilized. The pre-treatment steps (e.g. multimedia filtration, activated carbon and ion exchange) are usually provided to prolong the RO membrane service life and enhance the water purification effect. However, due to limits of the equipment and chemicals available in Chemical Engineering Laboratory, filtered tap water was used as the RO feed to conduct the experimental investigation. Therefore, the data obtained will need to be considered in light of the feed water quality being lower than what is required. The experimental data findings hold true to the hypothesis with some exceptions which are taken as data anomalies. The permeate volume, flowrate, flux and quality (TDS, conductivity and pH) all responded appropriately while tending towards higher permeate volume and cleaner permeate quality overall. Over the course of the experimental investigation it has been determined that the optimum temperature and pressure will be approximately at 30 oC and 15 bar since pressure has a larger effect than temperature on the desired results. Furthermore, Type E4 is the highest achievable grade of ultrapure water that can be produced in a laboratory setting by utilizing influent municipal tap water. To achieve Type E.1, the feed water should be of a higher specification, having undergone the necessary pre-treatment steps and be in a multiple-pass reverse osmosis system. The major limitation of this study is that the experiments were conducted without pretreatment for RO feed which could have impacted the RO membranes negatively resulting in lower permeate flux and the expected water quality not being achieved. There are several solutions which can help improve the existing RO system. However, detailed feed water analysis is required before determining which pre-treatment process is required. To further optimize the RO process in a comprehensive manner, all the affecting parameters of the membrane filtration and UPW production plant have to be considered alongside a matrix that gives financial estimates for each experiment set. Page 3 of 41
REVERSE OSMOSIS OPTIMIZATION | Student ID: 012181 2.0 Introduction The SOLTEQ Membrane Filtration Unit (Model TR16-1) will be utilized for the purpose of this experimental investigation. The membrane filtration module in the unit consists of two RO filters which provide a single pass series filtration and have the following characteristics; Tubular Polyamide Film for Reverse Osmosis having a 99% rejection percentage for NaCl. The major challenges for optimizing reverse osmosis is that RO systems are energy intensive and labour intensive. Also they are highly susceptible to fouling, scaling, chemical attack and mechanical damage resulting in high capital costs due to the need for regular maintenance (cleaning) and relatively fast replacement. Therefore, the main challenges in UPW production are maximizing yield for mass production flow rate and maintaining stringent quality control. With regards to solving the energy intensive factor of an RO system, heating/cooling and pressurizing are two of the main high energy consumption parameters at a semiconductor fab and therefore to reduce the energy consumption of the plant these will have to be decreased while still producing UPW at the same specification. This means bringing them down to an acceptable level which would imply that original energy consumption was not efficient or did not have heat integration or more energy than was necessary was used. While reverse osmosis is a non-thermal process minor temperature manipulation towards either cooling or heating are usually feasible and mostly required. For the purpose of this investigation, the specifications below have been identified; Table 2. Selected Water Quality Specifications Water Quality Units Parameter1
Approximate Influent Required Ultra-Pure Municipal Water Supply Water Specifications
Conductivity2
250
5.0
—
Resistivity, 25°C (On-line)
18.1
18.2
18.2
18.2
16.5
12
0.5
TOC (μg/L) (on-line for 0.05 μm
500
0.05–0.1
1000
200
N/A
—
—
—
0.1–0.2
1000
350
