(DESALINATION EQUIPMENT)

Transcription

1 (DESALINATION EQUIPMENT) FOR FRESH AND POTABLE WATER PACKAGE Z 10/06/2014 As Built AB LM ES AFE 1 18/10/2013 Issued for project acceptance IFA AFE ES PR 0 19/09/2013 Issued for project acceptance IFA ES PR PR C 15/07/2013 Issued for revision IFR ES PR PR B 28/03/2013 Issued for revision IFR ES PR PR Rev. Revision Date Reason for issue Prepared Verified Approved (dd-mm-yyyy) by by by Supplier Name: Supplier Project No.: Supplier Doc. No.: GEMWATER 12D20 12D20-A04-01 T 5 D other than those for which it was supplied. Copyright TECHNIP France All rights reserved.

2 CONTENT 1. INTRODUCTION Raw Water Characteristics REFERENCE DOCUMENTS PROCESS DESCRIPTION AND PERFORMANCES Fresh water production unit (53-XX-0001) and chemical dosing package (53-XX-0007) Design conditions Permeate characteristics Fresh Water Production units operation philosophy Process Description Sand Filters (53-CA-0001 A/B) Cartridge Filters (53-CB-0001 A/B) Chemicals dosing units (53-XX-0007) Desalination Units (53-CZ-0001 A/B) Fresh Water Transfer Tank (53-TB-0001) & Pumps ( 53-PA-0002 A/B) Remineralization Filter (53-CA-0002) Cleaning in Place Skid (53-XX-0002) Package design conditions Cleaning Package process description Service Water Hydrophore Package (53-XX-0003) Package design conditions Service water hydrophore package process description Potable Water Hydrophore Package (53-XX-0004) Package design conditions Potable water hydrophore package process description Potable Water Distribution Package (53-XX-0005) Package design conditions Potable water distribution package process description Hot Water Distribution Package (53- XX-0006) Package design conditions Hot water distribution package process description UTILITY LIST START-UP OPERATION SHUTDOWN... 16

3 no.: No.: : PROCESS DESCRIPTION Page:3 of INTRODUCTION The purpose of this document is to define the process requirements for the design of the below packages for the offshore facilty for Dong Energy, North Sea, Denmark XX-0001 Fresh Water Production Package - 53-XX-0002 Cleaning in Place Package - 53-XX-0003 Service Water Hydrophore Package - 53-XX-0004 Potable Water Hydrophore Package - 53-XX-0005 Potable Water Distribution Package - 53-XX-0006 Hot Water Distribution Package - 53-XX-0007 Chemicals dosing units. 1.1 Raw Water Characteristics Package inlet flowrate: 15 m 3 /h during normal operation RO inlet flowrate: 7 to 10 m 3 /h 28 m 3 /h one filter operating/one in backwash Type of water: sea water Pretreatment (by Client): coarse filtration at 150 µm + chlorination Calcium: 408,1 mg/l Magnesium: 1.297,5 mg/l Potassium: 387,5 mg/l Sodium: ,8 mg/l Barium: 0 mg/l Chloride: ,5 mg/l Sulphate: 2.701,7 mg/l

4 Bicarbonate: 142,5 mg/l Fluoride: 1,3 mg/l Bromium: 65,9 mg/l Indium: 0,05 mg/l Silica: 2,4 mg/l ph: 8,26 Temperature: 4 to 12 C Feed pressure: 2,5 barg at battery limits Chlorine content: <1 to 2 mg/l in normal operation. e:process DESCRIPTION Page: 4 of 16 Up to 5 mg/l during shock chlorination. 2. REFERENCE DOCUMENTS The design of the system is based on the following data sheets: - C086-TECH-R-DS C086-TECH-R-DS C086-TECH-P-XB C086-TECH-P-XB C086-TECH-P-XB C086-TECH-P-XB C086-TECH-P-XB C086-TECH-P-XB C086-TECH-S-FD-0009

5 : PROCESS DESCRIPTION Page:5 of PROCESS DESCRIPTION AND PERFORMANCES 3.1 Fresh water production unit (53-XX-0001) and chemical dosing package (53-XX-0007) Design conditions Area classification: Classified Zone 2, IIA, T3 Design permeate flow rate: 2,5 m 3 /h Design temperature (mechanical): -7/+60 C Design pressure (mechanical): 7 barg for pressure vessels Design pressure (mechanical): static head + 0,5 m.w.c. for atmospheric vessels Operating temperature: +4/+12 C Permeate characteristics Flow rate: 2,5 m 3 /h ph: 6,5-7 approx (WHO guideline) Outlet operating pressure: 2 barg 25 C: > 30 µs (Ref. C086-TECH-S-FD-0009) Fresh Water Production units operation philosophy Two RO trains x 100% are supplied: production of 2,5 m 3 /h (design condition) is continuous, with one train operating and the other in standby mode. Production is based on 53-TB-0001 level: when the level on the tank is maximum, the production of fresh water is stopped. In this case, the working line will be stopped and maintained in continuous flushing. A continuous pretreatment, independent from which RO train is in operation, is guaranteed dosing necessary chemicals (biocide, flocculant, antiscalant and sodium metabisulphite SMBS - ) on the common lines, while filtrations steps are interconnected (automatically for sand filters and manually for cartridge filters).

6 : PROCESS DESCRIPTION Page:6 of 16 Normally, both sand filters are working together, treating 7,5 m 3 /h each. In case of backwash of one sand filter, for example 53-CA-0001 B, inlet/outlet valves 53-HV-5005 B and 53-HV-5011 B will be closed and backwash valves 53-HV-5006 B and 53-HV-5007 B will be opened, while inlet/outlet valves 53-HV-5005A and 53-HV-5011A will remain opened to maintain in operation sand filter 53-CA-0001 A (backwash valves 53-HV-5006A and 53-HV-5007A will remain closed) that will treat the entire flow rate (15 m 3 /h). In this way, the RO train 53-CZ-0001 A will continue the production without any interruption. In case of need of cartridges replacement, cartridge filter 53-CB-0001 A will be isolated closing related isolation manual valves. Isolation manual valves of filter 53-CB-0001 B will be opened together with manual valve 53-WB-5022 on the interchange line. In this way, RO train 53-CZ-0001 A will continue the production without any interruption. The RO train 53-CZ-0001 B in standby must be in preservation (following manufacturer instructions) or in continuous flushing using sea water; in case of preservation, the displacement of the preservation agent is required before the production of fresh water. In case of high level in the 53-TB-0001 tank the sand filters will remain in operation mode and the RO train will be in continuous flushing: the high pressure pumps will not run and the treated water downstream the sand filters will be drained through the RO brine (concentrate) line Process Description The first package 53-XX-0001 is dedicated to fresh water production. The fresh water is produced from seawater pre-filtered (150 µm filtration rate) and chlorinated by Client (2 ppm of residual free chlorine during normal operation, 5 ppm of residual free chlorine during shock dosage, as per project datasheet doc. N. C086-TECH-R-DS-0077) and used to supply service water, potable water (after remineralization) and hot water to users. Here following is the description of the process and operation of the main equipments included in our scope Sand Filters (53-CA-0001 A/B) Feed water is filtered by sand filter (53- CA-0001 A/B). The two filters are designed to work in parallel, but each of them is also able to treat the entire flow rate: in that way, in case of maintenance or failure, the working filter can be replaced by the second one without stopping the RO unit. The sand filters are filled with fine sand at single size, from 0,8 to 1,2 mm diameter, height bed (1 m) having the capability to remove the particle present in the sea water.

7 : PROCESS DESCRIPTION Page:7 of 16 Time to time the filter needs to be backwashed. Beginning of backwash phase depends on 3 causes: a pre-set value of differential pressure (max 0,5 barg during normal operating condition, when both filters are in operation) or a defined number of working hours or a defined quantity of water produced, whichever came first. The sea water is used as backwash fluid at the end of the filtration cycle. In this phase the normal feed water flow rate is increased of the quantity necessary for backwash and backwash flow rate is regulated from the orifice 53- FO-5000 A/B installed on the backwash inlet line, while the flow rate of water feeding the second filter depends on the high pressure pump request. Backwash duration is 30 minutes and approximately 10 minutes for the pre-service phase. At this point the filter is ready to operate for another filtration cycle. During the pre-service phase the sea water is fed on the filter at design conditions diverting the filtered water at discharge using an appropriate valve (53-HV-5008 A/B). The phase length, normally 10 minutes, guarantee the displacement of all the sea water not filtered containing inlet solids. At the imposed time termination, the filtered water recovery is perfectly acceptable for the further desalination membranes. Filters are equipped with automatic valves and their operation is fully automatic. In normal condition backwash frequency is every hours, based on inlet suspended solids content (the average working time for 10 ppm of suspended solids on the sea water is 38 hours). Technical data about sand filters: - Filter diameter : 800 m 3 /h - Filtration velocity: 15 m/h 30 m 3 /h - Backwash water: sea water m 3 /h - Backwash flowrate: 13 - Backwash velocity: 26 m/h Cartridge Filters (53-CB-0001 A/B) The second filtration step is a fine filtration with cartridge filters having size poring of 5 microns to protect the RO membranes from clogging phenomena. The cartridge housing is designed at 7 barg pressure. Two cartridge filters are provided, one operating and one as standby. Cartridge filters are interchangeable by manual valve 53-WB Cartridge are not reusable type and the substitution is given from a p alarm (each filter is equipped with a differential pressure transmitter). Cartridge substitution is expected every 4-6 months, to be verified during start up, when the exact TSS content will be checked.

8 : PROCESS DESCRIPTION Page:8 of 16 Also cartridge filters, can be manually exchanged from one RO train to the other avoiding RO membrane system stop Chemicals dosing units (53-XX-0007) The sea water desalination unit needs some chemical dosages to operate safely and avoid scaling or malfunction. To optimize sand filtration efficiency, a flocculant agent is dosed on the inlet stream. Flocculant dosage data: Product name: MI-SWACO WT 1086 Product type: Flocculant Dosing rates: 2 ppm Dilution rate: 3 % Frequency: continuous Dosig pumps: 53-PC-0013 A/B Dosing flow rates: 0,7 l/h Storage tank: 53-VZ-0005 Storage tank capacity: 250 l net Then a non oxidizing biocide is dosed on the sea water common inlet before the sand filters in order to maintain a sterile condition avoiding bacteria growing. The non oxidizing biocide dosage have to be confirmed during the commissioning, normally the non oxidizing biocide dosage is intermittent. Biocide dosage data: Product name: MI-SWACO MB 5111 Product type: non-oxydizing biocide Dosing rates: 1000 ppm Dilution rate: pure product Frequency: once per week for 60 minutes Dosing pumps: 53-PC-0014 A/B Dosing flow rates: 15 l/h Storage tank: 53-VZ-0006 Storage tank capacity: 60 l An antiscalant chemical dosage is foreseen before the cartridge filters in order to avoid the precipitation in the brine compartment, for example carbonates, fluorides or calcium sulphates. Antiscalant dosage data:

9 Product name: MI-SWACO SI 4470 Product type: scale inhibitor Dosing rates: 5 ppm Dilution rate: pure product Frequency: continuous Dossing pumps: 53-PC-0011 A/B Dosing flow rates: 0,1 l/h Storage tank: 53-VZ-0003 Storage tank capacity: 60 l D : PROCESS DESCRIPTION Page: 9 of 16 Immediately before the high pressure pumps a reducing agent (SMBS, sodium metabisulphite) is dosed in order to avoid the presence of free chlorine (normally 2 ppm, 5 ppm in case of shock dosage before the package, based on data sheet C086-TECH-R-DS-0077) and oxygen that could damage the sea water desalination membranes. SMBS dosage will also decrease the ph on permeate to optimize remineralization process. SMBS dosage data: Product name: MI-SWACO OR 13 Product type: oxygen scavenger Dosing rates: 10 to 20 ppm Dilution rate: pure product Frequency: continuous Dosing pumps: 53-PC-0012 A/B Dosing flow rates: 0,1 to 0,2 l/h Storage tank: 53-VZ-0004 Storage tank capacity: 60 l Desalination Units (53-CZ-0001 A/B) The inlet water, filtered by sand filters and cartridge filter and chemically conditioned, feed the RO train. Normally only one train is operating, while the second is in standby mode (in preservation or flushed). Reverse osmosis will be used to provide the removal of dissolved solids and ions from the feed sea water. The designed system is composed of one single pass RO with two stages for each unit (units 53-CZ-0001 A/B are composed of 2 vessels per unit, containing 3 membranes each vessel) : this configuration is the one suitable to obtain permeate with requested characteristics (conductivity 500 µs/cm). In Reverse Osmosis, water under pressure is forced across a membrane element with a portion of the feed permeating the membrane and the balance of the feed water sweeping along the

10 C : P Page:10 of 16 membrane surface and exiting without passing through the membrane. The membrane freely passes water but rejects most of the dissolved minerals as well as any small particles. An illustration of an RO membrane element is given as Figure 1. The conditioned and filtered water will reach the suction side of the SWRO high pressure pumps and will be fed to the SWRO modules. The SWRO desalinated (permeate) water will be sent directly to the fresh water transfer tank (53-TB-0001), whereas the concentrated brine from sea water RO will be discharged. Permeate quality is checked by a conductivity meter on product (53-QT-5002 A/B): if conductivity exceeds the design product value, permeate is automatically discharged, else the treated water is automatically diverted at the fresh water transfer tank (53-TB-0001). Figure 1: RO Membrane Element The unit has been designed to guarantee a production of 2,5 m 3 /h at 4 C and 12 C. Feed water flow rate varies from 7 to 10 m 3 /h depending on the recovery of the RO unit (linked to operating temperature). Neverthless, to optimize working conditions of the high pressure pump, it is necessary to feed the package with a higher flow rate (15 m 3 /h): the excess of water is discharged before RO unit by 53-FV-5003 A/B valve, controlled by 53-FT-5003 A/B: this water is high pressurized water and for this reason it is discharged together with RO brine on the discharge line WS-53L5098-D51-0 and WS-53L5099-D51-0 (ANSI#600). The recovery of the system is 25% at 4 C and 35% at 12 C.

11 Level transmitter 53-LT-5002 is installed on the fresh water transfer tank 53-TB-0001: this instrument protects the fresh water pumps 53-PA-0002 A/B against cavitation in case of low level in the tank and in addition controls the start/stop of the fresh water production unit by controlling the high pressure pumps 53-PA-0001 A/B. When a minimum level set value is reached in the tank, high pressure pump start to fill it; while when the level on the tank exceeds a maximum set value, duty high pressure pump is stopped. This condition is usually verified when the request of fresh water on the potable distribution line is reduced. During this stop, the RO unit must be flushed, feeding the plant only using the inlet pressure at battery limit (2,5 barg). The water flowing on the RO vessels is totally discharged on

12 : PROCESS DESCRIPTION Page:11 of 16 concentration line WS-53L5017/33-D51-0, while valves 53-QV-5002 A/B, 53-QV-5003 A/B and 53-FV-5003 A/B are closed. During working RO train operation or flushing, the second train is in any case in preservation, following the instructions of membranes preservation instructions paragraph. With normal maintenance, the membranes lifetime is 3 years. MEMBRANES PRESERVATION INSTRUCTIONS In case of shutdown of an RO unit for more than a maximum of 48 h, elements must be preserved to prevent biological growth. If the membranes are known or assumed to be fouled (based on plant performances measured by conductivity meter 53- QT-5002 A/B or quality of feed water, that could be evaluated with frequency of sand filters backwash requirement), depending on their previous operational history, it will be necessary in almost all cases to clean (following cleaning procedure) the membranes prior to shutdown and preservation. After cleaning, the preservation should follow within the next 10 h as follows: 1. Totally immerse the elements in the pressure vessels in a solution of 1 to 1.5% SMBS, venting the air outside of the pressure vessels. Use the overflow technique: circulate the SMBS solution in such a way that the remaining air in the system is minimized after the recirculation is completed. 2. Separate the preservation solution from the air outside by closing all valves. Any contact with oxygen will oxidize the SMBS. 3. Check the ph once a week, taking a sample on site (using sample point at the outlet of RO vessels). When the ph becomes 3 or lower, change the preservation solution. 4. Change the preservation solution at least once a month. During the shutdown period, the plant must be kept frost- free flushing the unit, and the temperature must not exceed 113 F (45 C). A low temperature is desirable (4-10 C). In case of long period shutdown, the use of glycol as preservation solution is recommended: this solution is preferable also in case of very low temperature (4-10 C). In both cases short and long preservation period the system needs a cleaning (see 3.2.2) before restart in order to remove all chemical traces. When the train is restarted, valve 53-QV-5002 A (53- QV-5003 A) must remain closed, while valve 53-QV-5002 B (53-QV-5003 B) is opened until the conductivitymeter 53-QT-5002 A/B indicates the correct value. When this happens, valve 53-QV-5002 B (53-QV-5003 B) will be closed, while valve 53-QV-5002 A (53-QV-5003 A) will be opened Fresh Water Transfer Tank (53-TB-0001) & Pumps ( 53-PA-0002 A/B) The desalinated water is stored in the fresh water transfer tank 53-TB-0001 (material: GRP; volume: 3 m 3 ).

13 : PROCESS DESCRIPTION Page:12 of 16 The water level in the tank is controlled by a level transmitter (53-LT- 5002). This instrument controls both the 53-PA-0001A/B in order to start/stop the RO unit and the 53-PA-0002A/B in order to start/stop the fresh water transfer pumps according to the water level inside the tank. Different set- points are foreseen to enable/disable the running of RO unit pumps and fresh water transfer pumps. The level transmitter 53-LZT-5001 is installed as safety instrument: very low level trips the pumps (53-PA-0002 A/B), while very high level trip the RO unit (53-CZ-0001 A/B) Remineralization Filter (53-CA-0002) Permeate collected in fresh water transfer tank (53-TB-0001) is pumped to a remineralization filter capable to neutralize the desalinated water and increase the Hardness Alkalinity up to a value acceptable for the human consumption (7 to 8, in compliance with WHO guideline). Having no acid or carbon dioxide available, as per platform rules, the contact time of the water with the calcite is increased to minimum 20 minutes in order to obtain the complete reaction. Calcite refilling is expected after 6 months of operation and - in case of media filtration pressure drop increase - a manual backwashing is possible using the desalinated water as backwash fluid from the bottom to the top. Fresh water transfer pumps are used together for backwashing the remineralizer. Remineralized water quality: T = 4 C T = 12 C Total Hardness ppm CaCO 3 Alkalinity ppm HCO 3 Carbon Dioxide (CO 2 ) 0,6 0.5 ppm ph TDS ppm 3.2 Cleaning in Place Skid (53-XX-0002) Package design conditions Area classification: Classified Zone 2, IIA, T3 Design flow rate: 8 m 3 /h Design temperature (mechanical): -7/+60 C Design pressure (mechanical): 7 barg for pressure vessels Design pressure (mechanical): static head + 0,5 m.w.c. for atmospheric vessels Operating temperature: +4/+35 C

14 DONG Doc no.: No.: Doc. Title:PROCESS DESCRIPTION Page:13 of Cleaning Package process description The membrane cleaning system (CIP) is supplied in order to have an efficient system to maintain the desalination membrane at the design conditions. The supply includes a tank (53-TB-0004) of 640 l capacity equipped with an heating electrical resistance in which the fresh chemical solution is prepared; a centrifugal pump (8 m 3 /h) for the chemical solution recirculation and feeding; a cartridge filter to avoid to feed dirty material into the membranes. Chemical cleaning will be carried out every 4-6 months for each desalination unit. Manufacturer suggest a cleaning in two steps based on feed water characterictics. In this case, the suggestion is a first step with basic solution (0,1% NaOH) to remove organic fouling, followed by an acid step with 0,2% HCl solution to remove carbonates and other fouling products. In any case, final cleaning procedure is supplied by membranes supplier and included in Operation and Maintenance Manual (Doc. N. C086-TECH-Z-MB-4400). Different and specific cleaning are possible in case of particular presence for example biocide or detergent cleaning. In case of long membrane inactivity a preservation with sodium bisulphite is necessary and can be done with the supplied equipment.

15 no.: No.: e:process DESCRIPTION Page:14 of Service Water Hydrophore Package (53-XX-0003) Package design conditions Area classification: Classified Zone 2, IIA, T3 Design flow rate: 7,5 m 3 /h Design temperature (mechanical): -7/+60 C Design pressure (mechanical): 12 barg for pressure vessels Operating temperature: +4/+13 C Discharge operating pressure: 6,5 to 8 barg Service water hydrophore package process description The service water distribution package is designed to guarantee the presence of service water in the platform and includes service water feed pumps (53-PA-0003 A/B) and service water hydrophore tank (53-VZ-0001) in order to maintain the pressure. Service water (7,5 m 3 /h) is used for process and utility consommers and is distributed in a network at 7,5 barg. The pressure transmitter 53-PT-5016, installed at the hydrophore outlet, regulates the start/stop of pumps 53-PA-0003 A/B. Pumps start when the pressure get the minimum value of 6,5 barg and they stop when the pressure increases over 8 barg. 3.4 Potable Water Hydrophore Package (53-XX-0004) Package design conditions Area classification: Classified Zone 2, IIA, T3 Design flow rate: 15 m 3 /h Design temperature (mechanical): -7/+60 C Design pressure (mechanical): 12 barg for pressure vessels Operating temperature: +4/+13 C Discharge operating pressure: 6,5 to 8 barg

16 : PROCESS DESCRIPTION Page:15 of Potable water hydrophore package process description The potable water hydrophore package is designed to guarantee the presence of potable water in the platform and includes potable water feed pumps (53-PA A/B) and potable water hydrophore tanks (53-VZ-0002 A/B, working in parallel) in order to maintain the pressure. Potable water (15 m 3 /h) is distributed in cold (53-XX-0005) and hot (53-XX-0006) distribution networks. The pressure transmitter 53-PT-5018, installed at the hydrophores common outlet, regulates the start/stop of pumps 53-PA-0004 A/B. Pumps start when the pressure get the minimum value of 6,5 barg and they stop when the pressure increases over 8 barg. 3.5 Potable Water Distribution Package (53-XX-0005) Package design conditions Area classification: Classified Zone 2, IIA, T3 Design flow rate: 15 m 3 /h Design temperature (mechanical): -7/+60 C Design pressure (mechanical): 12 barg for pressure vessels Operating temperature: +4/+13 C Operating pressure. 6,5 to 8 barg Potable water distribution package process description Dedicated water sterilizer (53-CX-0001 A/B), using Ultra Violet lamps, are supplied in order to avoid bacterial growing. Main characteristics of UV lamps: - Number: 2 (one operating and one in standby mode) - Power: 200 W - UV Dosage: 40 mj/cm 2 Sterilized potable water is distributed to users or to hot water distribution package (53-XX-0006). To maintain a selected chlorine content on the treated water, a Sodium Hypochlorite injection point has been foreseen. NaOCl injection skid is designed by other.

17 : PROCESS DESCRIPTION Page:16 of Hot Water Distribution Package (53- XX-0006) Package design conditions Area classification: Classified Zone 2, IIA, T3 Design flow rate: 4 m 3 /h Design temperature (mechanical): -7/+80 C Design pressure (mechanical): 12 barg for pressure vessels Operating temperature: +4/+75 C Operating pressure: 6,5 to 8 barg Hot water distribution package process description The hot water distribution package is designed to guarantee the presence of hot water in dedicated point of the platform and includes hot water circulation pumps (53-PA-0005 A/B) and calorifiers (53-TA-0001 A/B) equipped with calorifier system in order to maintain the design temperature. Heaters are designed to maintain a temperature of 75 C (as per NORSOK H-003 requirement). Pressurized hot water, is cooled by mixing with cold potable water, before to be distributed. The distribution water temperature is 65 C. The water temperature inside the tanks is maintained by an electrical heater (60kW). The electrical heaters (53-FE-0002A/B) is controlled by an analog signal (4-20mA) generated according to the water temperature that is read by the transmitter 53-TT-5002A/B. Both calorifers are operated at the same time. Hot water is delivered to users and the return is recirculated to calorifiers (53-TA-0001 A/B) by hot water circulation pumps (53-PA-0005 A/B). 4. UTILITY LIST See document n. C086-TECH-P-DS-4409 Utilily Balance. 5. START-UP OPERATION See document n. C086-TECH-Z-MA-4400 Installation, start-up and commissioning manuals. 6. SHUTDOWN See document n. C086-TECH-Z-MB-4400 Operation and Maintenance manual.