Retrofits to improve desalination plants

Operation of the RO Kinetic ® energy recovery system: Description and real experiences

Orders & Contracts

Waste energy recovery in seawater reverse osmosis desalination plants. Part 1: Review

SWRO process simulator

A comprehensive review of energy consumption of seawater reverse osmosis desalination plants

Seawater reverse osmosis with isobaric energy recovery devices

Mixing phenomena in an isobaric energy recovery device (ERD) of a seawater reverse osmosis (SWRO) desalination system are investigated experimentally and numerically using Particle Image Velocimetry (PIV) and Computational Fluid Dynamics (CFD). The ERD, which recovers energy from high-pressure brine discharged from RO membranes, is one of the most important mechanical devices in a SWRO desalination system. In this ERD, seawater is introduced into a vertical chamber from the top, and then high-pressure brine is introduced into the chamber from the bottom. The high-pressure brine pressurizes the seawater through direct liquid-to-liquid contact, transferring high-pressure energy of the brine to the seawater. This enables a sharp reduction in the electric energy consumption, typically 50%, of high-pressure pumps used to elevate seawater pressure for RO membranes. The energy recovery efficiency of the present ERD is over 98%, which is extremely high compared to a conventional turbine-type energy recovery device, such as a Pelton turbine, which has a system energy recovery efficiency of 60 to 80%. The possible weakness of the present ERD is the amount of mixing between brine and seawater around the direct contact surface, because mixing phenomena increase the salinity of seawater supplied to RO membranes. A higher pressure is required to keep the same amount of permeate from the membrane, which results in an energy loss in the system. To minimize mixing, a set of unique flow distributors was invented and placed at both ends of the pressure exchange chamber, which stabilizes the contact surfaces and suppresses excessive mixing. Mixing phenomena in the pressure-exchange chamber are investigated experimentally in detail with PIV and numerically with CFD, and the effectiveness of the flow distributors is clarified.

Energy optimisation of existing SWRO (seawater reverse osmosis) plants with ERT (energy recovery turbines): Technical and thermoeconomic assessment

Objectives The production cost of reverse osmosis (RO) seawater desalination plant is determined by the CAPEX (Capital expenditure) and OPEX (Operating expenditure). In detail, CAPEX and OPEX are composed of direct cost, overhead cost, electricity cost, and other O&M costs. However, CAPEX and OPEX may vary by country and region. Therefore, this study tries to estimate the production cost by calculating the construction and maintenance costs depending on production capacities based on the operation results such as TDS concentration and the energy consumption from a seawater desalination plant in Korea. Methods A two-stage RO based seawater desalination plant with a capacity of 10 MIGD (45,000 m3/d) was used in this study. The plant consists of a 2 MIGD (9,000 m3/d) unit having DABF (Dissolved air bio-ball filter) and UF (Ultrafiltration) as pretreatment processes, and another 8 MIGD (36,000 m3/d) unit having DABF and DMF (Dual media filtration) as pretreatment processes. To estimate the production cost, construction and maintenance costs were calculated by using GWI's Desaldata cost estimator. CAPEX (Capital expenditure) was calculated based on production capacity, recovery rate, TDS concentration and temperature of seawater, while OPEX (Operating expenditure) was calculated based on production capacity, country, energy consumption, and electricity unit price. Results and Discussion The energy consumptions from EMS (Energy Management System) were 5.48 kWh/m3 at SLC (9,000 m3/d) and 3.4 kWh/m3 at MLC (45,000 m3/d), respectively. In the CAPEX, MLC was reduced by 395,954 ￦/m3 compared to SLC, and the LLC was lower by 192,019 ￦/m3 than MLC. Overall, CAPEX decreased as the production capacity increased. The CAPEX of small plants with production capacity between 10,000 and 50,000 m3/d was significantly different; however, there was no significant difference in larger plants having a capacity above 100,000 m3/d. The OPEX for the annual production capacity showed a sizable difference with 742.3 ￦/m3, 636.5 ￦/m3 and 580.3 ￦/m3 for SLC, MLC, and LLC, respectively. The electricity cost was a substantial portion of OPEX. Also, the production costs based on the interest rates (3% and 5%) were 1,326-1,384 ￦/m3, 1,163-1,209 ￦/m3, and 1,023-1,070 ￦/m3 for SLC, MLC, and LLC, respectively. The results were consistent with 1.0 US$/m3, which is the average production costs presented from other references. Conclusions The production cost estimated using the Desaldata cost estimator based on the CAPEX and OPEX tends to decrease as the capacity increases. However, when the capacity increased over 50,000 m3/d, the production cost decreased by an average of 40 ￦/m3. Thus the decrement of production cost reduced. From these results, the production cost of tap water through seawater desalination was estimated between 1,023 ￦/m3 and 1,070 ￦/m3 above 100,000 m3/d. Therefore, it is difficult to introduce a large-scale desalination plant in Korea, because the average tap water price was 834.6 ￦ in Korea in 2017. However, It is expected that the seawater desalination will be introduced as an alternative water source whenever drinking water price rises, or when the quantity of available drinking water sources reduce due to climate change and water pollution, or whenever energy consumption is reduced as a result of the steady development of the component technologies such as the reverse osmosis membrane, high-pressure pump, and energy recovery device. Key words: Reverse osmosis seawater desalination plant, Water price, Capital expenditure, Operating expenditure, Energy consumption

Analysis of the influence of the configuration in ERD retrofit in two-stage SWRO trains

Development and experimental studies on a fully-rotary valve energy recovery device for SWRO desalination system

Reverse osmosis (RO) technology requires high energy input in order to extract freshwater from seawater. Improvements in RO technology have led to seawater RO (SWRO) becoming the dominant form of large scale desalination around the world. However, the specific energy consumption (SEC) of SWRO remains substantially higher than that for surface water treatment and indirect potable recycling, making SWRO less cost effective than other alternatives for producing potable water. Furthermore, where non-renewable energy sources are used to supply SWRO energy demand, higher levels of greenhouse gas are emitted compared with lower energy alternatives. The purpose of this paper is to review the RO process configurations currently available and their impact on reducing SWRO energy consumption. This paper highlights the main factors contributing to SWRO energy consumption and presents some of the commonly adopted approaches to reducing SEC in SWRO plants. The use of energy recovery devices (ERDs) in SWRO is explored and the relative effectiveness of the various types of ERDs in reducing SEC presented.

Reduction of energy consumption in seawater reverse osmosis desalination pilot plant by using energy recovery devices

The availability and security of water production using reliable energy recovery technologies

Comparative study on stand-alone and parallel operating schemes of energy recovery device for SWRO system