Reverse Osmosis (RO) and RO Energy Recovery Devices. Steve Alt CH2M HILL November 2014

Transcription

1 Reverse Osmosis (RO) and RO Energy Recovery Devices Steve Alt CH2M HILL November 2014

2 Discussion Outline Reverse Osmosis (RO) Basics and energy consumption (SWRO) Introduction to RO Energy Recovery Devices (ERDs) Description of the ERD Tool Discussion OBJECTIVE: Crash course in RO and RO Energy Recovery Devices Awareness of ERD Tool 2

3 Reverse Osmosis Basics

4 THE FILTRATION SPECTRUM µ m Å MOLECULAR WEIGHT ,000 20, , ,000 Aqueos salts Carbon black Paint pigment RELATIVE SIZE OF Pyrogens Yest cells Beach sand COMMON Metal ions Virus Bacteria MATERIALS Colloidal silica Pollens Sugars Albumin protein Milled flour FILTRATION TECHNOLOGY Reverse Osmosis Nanofiltration Microfiltration Particle filtration Ultrafiltration

5 Dilute solution Concentrate solution membrane Applied pressure Osmosis Reverse Osmosis

6 Reverse Osmosis 6

7 Typical Single Stage Seawater RO System 7

8 Typical Two-Stage Brackish RO System 8

9 RO Energy Recovery Devices

10 Energy Recovery Devices To boost this pressure Use this pressure 10

11 RO Feed Pressure and Energy Consumption is a function of feed salinity psi Seawater RO Brackish RO NF UF MF

12 Evolution of SWRO Energy Consumption kwh/m

13 Technology Contribution to SWRO Energy Minimization 13

14 Centrifugal Turbocharger - Can be used in front of stage 1 (SWRO) or in between stages (BWRO) - Turbine connected directly to pump - Operation: 1. High pressure brine fed to the turbine 2. Turbine rotation turns shaft 3. Shaft turns pump impeller Selected Devices - ERI: HTC - FEDCO: HPB 3 2 1

15 Turbocharger for Feed Pump Pressure Reduction 25 psi 570 psi 840 psi Feed Pump Turbo - SWRO applications - Reduces TDH of feed pump 15

16 Two-Stage System with Interstage Turbocharger Turbo - BWRO applications - Provides interstage boost and flux balancing 16

17 Two-Stage System with Interstage Turbocharger 128 psi 152 psi 105 psi Turbo - BWRO applications - Provides interstage boost and flux balancing 17

18 Centrifugal Direct Coupled - Typically used for SWRO applications - Permits smaller HP pump motor - Operation: 1. High pressure brine fed to the turbine 2. Rotating power used to assist motor 3. HP Pump operates normally Selected Device - Flowserve: Pelton Wheel 3 High Pressure Turbine 1 2

19 Pelton Wheel for Feed Pump Motor Energy Reduction 25 psi 840 psi Feed Pump PW 925 hp 600 hp - SWRO applications - Reduces size of feed pump motor 19

20 Isobaric Device - Positive displacement ERD - Highest efficiency of ERD types - Operation: 1. Low pressure feed enters device piston to the right 2. Device rotates 3. High pressure brine enters device piston to the left 4. High pressure feed exits device 5. Device rotates Selected Devices - ERI: PX - Flowserve: DWEER

21 Isobaric Device for Feed Pump Flow Reduction 1400 gpm 700 gpm 700 gpm ERD Circulation pump - SWRO applications - Reduced flow to Feed Pump - Circulation Pump required 21

22 ERD Comparison - Isobaric has best efficiency - Turbocharger is least expensive and easiest to implement Efficiency Range Cost Range* ERD Type Low High Low High Turbocharger 55% 65% $ 55,000 $ 75,000 Pelton Wheel 65% 75% $ 120,000 $ 130,000 Isobaric 90% 96% $ 115,000 $ 170,000 *For 1,500 gpm brine flow application - Isobaric most common for SWRO - Turbocharger most common for BWRO 22

23 WRF Tool Tutorial

24 Introduction to ERD Tool Similar to vendor provided projections software Allows for comparison of different system configurations and different devices Isobaric vs. Centrifugal PX vs. DWEER Booster pump vs. throttling valve Estimates Present Worth cost ($/1,000 gal) and ERD payback period Enter Water Quality Data Enter RO System Design Information Calculate System Pressures and Water Quality Data Display Results 24

25 Sample Case Study 1-Stage SWRO System Permeate Flow = 1 mgd Recovery = 50% Flux = 10 gfd What is the best device and what is the payback period? 25

26 Tool: Inputs Page 26

27 Tool: Inputs Page 27

28 Tool: Inputs Page 28

29 Tool: Inputs Page 29

30 Tool: Inputs Page 30

31 Tool: Inputs Page 31

32 Tool: Inputs Page 32

33 Tool: Inputs Page 33

34 Tool: Cost Summary Page 34

35 Tool: Cost Summary Page 35

36 Tool: Cost Summary Page 36

37 Tool: Cost Summary Page 37

38 Actual Case Study Bonita Springs Retrofit Literature analysis performs 5 case study validations CH2M HILL performed a manual case study at Bonita Springs Utilities Groundwater desalter in Florida Four 1.5 mgd RO trains Feed TDS currently 4,700 mg/l and rising Power $0.08 Kwh Is an ERD suitable? If so, which type? 38

39 Bonita Springs Analysis Cost Summary

40 Bonita Springs Centrifugal devices offer better payback period Isobaric case has to consider reduced efficiency of HPP Reduced HPP flow by 25% Efficiency reduced from 74% to 68% Even though the device is more efficient, it is not the best for this application. If it was a new build, both centrifugal devices and the PX provide similar payback periods

41 High Pressure Pump Efficiency Calculation 41

42 Tool Application Valuable for anyone considering RO New Builds or Retrofits Use in conjunction with vendor provided programs Alternative evaluations Different ERDs Different manufacturers Different feed pumps Different system configurations Conceptual cost estimates Free to download from WateReuse Research Foundation 42