Why RO Membrane must be dechlorinated?
Dechlorination
When RO or NF membrane is used in the RO/NF process, the feed must be dechlorinated to prevent oxidation of the membrane. RO membranes have some chlorine tolerance before noticeable loss of salt rejection is observed. The first sign of chlorine attack on RO/NF membrane is loss of membrane flux followed by an increase in membrane flux and salt passage. Eventual degradation may occur after approximately 200–1,000 hours of exposure to 1 mg/L of free chlorine (200–1,000 ppm-h tolerance). The rate of chlorine attack depends on various feed water characteristics. Under alkaline pH conditions, chlorine attack is faster than at neutral or acidic pH. An acidic pH is preferred for better biocidal effect during chlorination. Chlorine attack is also faster at higher temperatures and higher concentrations of heavy metals (e.g., iron), that can catalyze membrane degradation. Since oxidation damage is not covered under warranty, Technical person always recommends removing residual free chlorine by pretreatment prior to exposure of the feed water to the membrane. Other oxidizing agents such as chlorine dioxide, hydrogen peroxide, ozone, and permanganate are capable of damaging RO/NF membranes also if not used properly.
Residual free chlorine can be reduced to harmless chlorides by activated carbon or chemical reducing agents. An activated carbon bed is very effective in the dechlorination of RO feed water according to following reaction:
C+2Cl2 +2H2O→4HCl+CO2
Sodium metabisulfite (SMBS) is commonly used for removal of free chlorine and as a biostatic. Other chemical reducing agents exist (e.g., sulfur dioxide), but they are not as cost-effective as SMBS.
When dissolved in water, sodium bisulfite (SBS) is formed from SMBS: Na2S2O5 + H2O → 2 NaHSO3
SBS then reduces hypochlorous acid according to: 2NaHSO3 + 2HOCl → H2SO4 + 2HCl + Na2SO4
In theory, 1.34 mg of sodium metabisulfite will remove 1.0 mg of free chlorine. In practice, however, 3.0 mg of sodium metabisulfite is normally used to remove 1.0 mg of chlorine.
The SMBS should be of food-grade quality and free of impurities. SMBS should not be cobalt-activated. Solid sodium metabisulfite has a typical shelf life of 4–6 months under cool, dry storage conditions. In aqueous solutions, however, sodium bisulfite can oxidize readily when exposed to air. A typical solution life can vary with concentration as follows:
Concentration (wt %) Solution life
10 1 week
20 1 month
30 6 months
Although the dechlorination itself is rapid, good mixing is required to ensure completion. Static mixers are recommended. The recommended injection point is downstream of the cartridge filters in order to protect the filters by chlorine. In this case, the SMBS solution should be filtered through a separate cartridge before being injected into the RO feed. Dechlorinated water must not be stored in tanks.
When RO/NF membranes are fouled with heavy metals such as Co and Cu, residual SBS (up to 30 ppm) partially converts to oxidants under the presence of excessive oxygen. When there is a heavy potential for metal fouling, SBS dosing amount control must be optimized and oxidation conditions of the concentrate must be monitored by an oxidation-reduction potential (ORP) meter.
The absence of chlorine should be monitored using an oxidation-reduction potential (ORP) electrode downstream of the mixing line. 175 - 200 mV threshold readings of the ORP have been typically applied. The electrode signal shuts down the high pressure pump when chlorine is detected.
We are keeping ready stock of Sodium metabisulfite, Hydrogen Peroxide, Hydrogen Floride HF, Potassium Permagnate, Hcl, Descaling compound and many more products for RO MEMBRANE cleaning and maintenance product in Mumbai, Kandla, Chennai, Kolkata, Fujairah.
Email : mail@rxmarine.com ( For INDIA SUPPLY )
mail@dubichem.com ( For UAE Middle East supply )
Sodium Sulfite reacts with hot water, steam or acids to produce corrosive material, Which is damaging PRECIOUS METAL PARTS. Scientifically its corrosiveness can be controlled by using CORROSION INHIBITOR and Catalyst.
RXSOL MARINE RESEARCH CENTRE Developed sodium sulfite based compound to neutralize CHLORINE content.
Sodium Sulphite (sulfite) with Catalyst Powder
Enviro Guard Sulfite
Email us to GET discounted price for MARINE CHEMICALS Ballast Water Treatment Chemicals : marinechemical@gmail.com
The whole idea of having this system is to produce as and when required to avoid vagaries . However the SANITISER liquid produced will last for a week (if stored in dark place in air tight container) after which it may start depleting.
A weak soln. ( 1.2 % ) is used. For purifying water
0.02 to 0 .2 % volumetric is sufficient for Potable Water Treatment
General formulation to calculate how much bleach is needed to add to a tank or a pipeline to disinfect it to a given chlorine residual using a given disinfectant. Usually someone wants to know how to meet an AWWA Standard (like C651-92, Disinfection of Water Mains). The equation below should be used to estimate the amount of sodium / Calcium hypochlorite (Chlorine Water is 6.00% sodium hypochlorite) needed to disinfect a given quantity of water to a desired chlorine concentration.
req'd residual in ppm
Valume of hypo = volume of water x ( ----------------------------- )
1,000,000 x hypo %
For example , say you had installed a new 5,000 gallon tank and wanted to make sure that you had at least a 100 ppm solution of chlorine in it.
How much 6.00% Hypochlorite would you need to add ?
- (5,000 gal x 100 ppm) / (1,000,000 x .06) = 8.33 gallons
How much 12% Hypochlorite solution would you need ?
- (5,000 gal x 100 ppm) / (1,000,000 x .12) = 4.17 gallons
If you use calcium hypochlorite (the white, powder version of chlorine, like HTH pool cleaner), the equation becomes:
req'd residual in PPM
Wgt. of Calcium Hypo (lbs)= gal of water x 8.33 lb / gal m x ( ----------------------------- )
1,000,000 x hypo %
- This is simply the previous equation multiplied by the conversion factor of 8.33 pounds per gallon of water.
Let's assume that we still need to disinfect 5,000 gallons at 100 ppm.
How many pounds of 65% calcium hypochlorite (HTH pool cleaner) are needed?
- (8.33 lbs/ gal. x 5,000 gal x 100 ppm) / (1,000,000 x .65) = 6.4 pounds
Why slip barrier coat required before loading of cargo like salt / Urea.
White cargo like salt, urea directly affected by rusty brown colour. Rust formation on the hold will discolor the white cargo salt when it comes into contact. Hence before loading of such cargo proper treatment of hold which makes entire surface rust free must required. Uses of slip barrier coat Hold block on entire loading area of hold and bulkheads can prevent the salt / urea from coming in contact with the rusty surface.
Stock and direct supply point of Slip barrier coat is Visakhapatnam - Gangavaram, Kandla - Deendayal port, Mumbai, Chennai - Ennore, kolkata - Haldia, Fujairah - Dubai.
Available packing : 25, 50, 210 Ltr DRUM
Approximate requirement of Slip barrier coat : only 2 Drums of 210 Ltr can cover 5 Hold area. For salt cargo, slip barrier coat can be applied after dilution. 1 drum can be diluted with 400 Ltr of water.
Capt. ravi.prakash 4:54 PM (3rd JAN'19)
to RX MARINE INTERNATIONAL
Dear Sir,
Ref our telcon, please find attached Hold photos after discharging of Australian Coal and cleaning (without applying any chemicals) in oct 2018 . Then vsl loaded Indonesian Coal and will be discharging same in abt a week. Next voyage is getting fixed to load Urea from Saudi. Basis the photos, which chemical would you suggest to be used. We were thinking of RXSOL PCS along with Aquatuff. Fyi, Owners have supplied 1200 Ltrs of Aquatuff HF last month.
Thanks & best regards,
Capt. ravi.prakash
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Dear Sir,
In image we can observe that BOTTOM line of hold is rusted, And your plan to load CLEAN CARGO like urea which is ammonia-ted product can result further heavy rusting. So here our suggestion is to go with PCS with Aquatuff HF. And after cleaning hold rust can be treated with RUST CONVERTOR by the ratio of 1:100 Ltr with water, this will change free iron rust content to orginal metal colour. ( For treatment of rust Each Hold maximum 50 Ltr RUST CONVERTOR REQUIRED ) and Finally HOLD can be treat with SLIP BARRIER COAT polymer, with dilution ration of 1:100 Ltr with Water. ( For Each Hold polymer coating maximum 50 Ltr Slip Barrier Coat REQUIRED )
Refer this link to get IMAGE of CARGO HOLD. http://rxmarine.com/sites/default/files/CARGO HOLD CONDITION REPORT 12.10.2018(1).xlsx
USES of slip barrier coat provide transparent POLYMER layer in between UREA and HOLD surface.
Application of SLIP BARRIER COAT is always be wise decision, this will not only protect hold metal surface from UREA contact, but also helps to release cargo without adhesion on cargo.
Thanking you
WBRGDS
Silvi
http://rxmarine.com/sites/default/files/CARGO HOLD CONDITION REPORT 12.10.2018(1).xlsx
Hi Silvi / Aaron 01-04-2018
Good day
Just to make sure, please confirm the supplied hold block are suitable for loading “cargo - bulk formed and/or granular sulphur – group c”
Pleased to hear
Thank you
Regards
::::::::::::::::::::::::::::::::::::
Reply
Dear Sir,
GD DAY.
Hold block is polymer emulsion, Which is unreactive towards most of the corrosive materials including Sulphur compound. Its application on hold surface will give protection for HOLD METAL surface.
when SULPHUR comes in contact with moisture - Water, releasing ACIDIC solution. Which is very corrosive, Its time to time neutralization also helpful to keep hold surface damage free.
For After application of HoldBlock on surface area, When matter comes to load sulphur then uses of Sulphur ACID neutralizer is also a wise decesion ...
Bilge Coat (Sulphur Acid Neutralizer)
RXSOL Bilge Coat is highly effective chemicals and an alkaline Solution for the Bilge Line and well during the carry of cargo as like Sulphur. This Product act as a neutrilizer for the collection of Acidic Bilge Water. Bilge coat is more safer and effective in use compare than other alkaline Materials.
Acts as Acid Neutralizer formed during sulphur voyages.
SKU: RXSOL-22-2209-025
Application:
Dose and Using Procedure
• Use a clean Drum or any plastic tank. Fill the water up to 190 Ltrs and add the RXSOL concentrated Bilge coat 2-4 Ltrs. Stir well and now it is ready RXSOL BILGE COAT SOLUTION to use.
• Pour 15 to 20 litres of RXSOL BILGE COAT SOLUTION directly into each hold sounding pipe from on deck. Replenish each time after the bilge water is pumped out.
For more details... Pl. refer this link http://rxmarine.com/bilge-coat-sulphur-resistance-alkaline
Thanking you
WBRGDS
Silvi
Why slip barrier coat required before loading of cargo like salt / Urea.
White cargo like salt, urea directly affected by rusty brown colour. Rust formation on the hold will discolor the white cargo salt when it comes into contact. Hence before loading of such cargo proper treatment of hold which makes entire surface rust free must required. Uses of slip barrier coat Hold block on entire loading area of hold and bulkheads can prevent the salt / urea from coming in contact with the rusty surface.
Stock and direct supply point of Slip barrier coat is Visakhapatnam - Gangavaram, Kandla - Deendayal port, Mumbai, Chennai - Ennore, kolkata - Haldia, Fujairah - Dubai.
Available packing : 25, 50, 210 Ltr DRUM
Approximate requirement of Slip barrier coat : only 2 Drums of 210 Ltr can cover 5 Hold area. For salt cargo, slip barrier coat can be applied after dilution. 1 drum can be diluted with 400 Ltr of water.
Holdwash is more effective then Lime wash :
1. Lime wash always be applied to a dampened surface (use a small hand-pumped spray) rather than directly to a dry substrate. It should not be applied in very cold, hot or wet conditions. It is also essential to wear protective gloves and goggles. While Slip barrier coat - hold block can be apply on dry as well as wet surface and for its application no any special precaution required.
2. Lime wash does not stop the acid attack on steel plates. Hard sulphur easily penetrates the soft lime wash and is not suitable for sulphur. While Slip barrier coat resulting polymeric barrier film which can't be punctured by any hard edge of sulphur.
Cost comparision : Slip barrier coat can be diluted with water before application. Only 4 - 5 drums of 210 Ltr Slip barrier coat is more then sufficient to cover 6 HOLD. And polymer coating last for more time then lime. Its application is also very simple compare to lime wash, simply dilute with water and spray on whole area. while for lime wash more manpower required with special precaution and care. Finally SLIP BARRIER COAT will cost less then Lime wash.
ALKAATUFF high foam is absolutely free along with the purchase of slip barrier polycoat - Hold block ( Pre load ) materials. ALKAATUFF High foam Free 1000 Ltr with the purchase of 1000 ltrs Ship PolyCoat Plus is available at Mumbai, Visakhapatnam, Ennore, Kolkata, Kandla - Gandhidham, Fujairah - Gulf
The largest supplier of ALKAATUFF high foam in Asia ( India and Middle East). More details of ALKAATUFF High Foam like MSDS and Using procedure of will be available through this link:
ALKAATUFF High Foam feature?
ALKAATUFF High Foam - Acts as an Acid Neutralizer - Useful for coal, Sulfur, Salt as its residue when in contact with water, is acidic in nature which directly damages the painted and metal surfaces.
ALKAATUFF High Foam - Acts as an Oil residue Emulsifier - Useful for removal of coal and oily residue.
ALKAATUFF High Foam - Results in Dense foam - Can be applied on the vertical surface for long duration.
ALKAATUFF Free sale offer.