Sulfites for Oxygen Control

The sulfite/oxygen reaction is known to be inhibited by some alcohols, phenols, amines, and thiosulfate. Other contaminants or organic treatment chemical such as corrosion inhibitors, scale inhibitors, and biocides may also slow down reaction time. A slow reaction can present a problem at early phases in a system and require the use of catalysts or feeding techniques that provide maximum time for the reaction to occur. The reaction rate for sulfite appears to be the fastest of all of the scavengers, followed by erythorbic acid and DEHA. Slower rates, in general, have been reported for hydroquinone, carbohydrazide, and hydrazine. View full article →

Industrial Water Analysis

Boiler water analysis

If you supervise a limited-attendance or unattended boiler then Lenntech can assist you with your water testing requirements.

Boiler water tests available

The specific method of chemical treatment used varies with the type of boiler and the specific properties of the water from which the boiler feed is derived. This is very site specific but Lenntech has the testing capability to cover all your requirements.

A boiler requires testing of three different water types as shown below:

Feedwater

Boiler feedwater is sourced from many different places. Some supplies come from industry owned bores and treatment plants, while others come directly from a council supply, however all feedwater should be analysed in order to correctly determine dose rates of treatment chemicals.

Water quality can change as it passes through a delivery or reticulation system, so it is important to check for various parameters at point of use - ie where it enters the boiler or pre-treatment system.

Boiler feedwater is usually a combination of returned condensate plus pre-treated makeup water from a softener, reverse osmosis, or other purification system. Typical tests used for boiler feedwater include:

  • Chloride or salinity
  • Conductivity
  • Dissolved Oxygen
  • Hardness
  • Iron and Manganese  
  • pH
  • Silica
  • Sulphide
  • Suspended Solids
  • Total Dissolved Solids
  • Turbidity

Not all water supplies will require all the tests shown here, and if the supply is constant the tests will not need to be repeated very often.

Boiler Water

The boiler water itself must be dosed in order for the boiler to run efficiently and safely. A chemical imbalance can lead to corrosion and damage to the system and this damage can ultimately lead to boiler failure and injury.

Boiler water analyses are basically aimed at keeping the parameters within established limits.

Tests include

  • Chloride
  • Hydroxide P2 Alkalinity
  • Nitrate
  • pH
  • Phenolphthalein P1 Alkalinity
  • Phosphate
  • Silica
  • Sulphite
  • Total Alkalinity
  • Total Dissolved Solids

Condensate

Good condensate is the best quality, least expensive water most systems can generate. You do not want to lose it, or contaminate it unnecessarily.

Steam condensate analysis should include

  • Ammonia
  • Conductivity
  • Copper
  • Iron
  • pH

Test

Description

Make-up, Raw Water pH, P/M-Alkalinity, Conductivity, Total Hardness, Total Calcium, Total Magnesium, Total Iron, Total Copper, Sodium, Silicate, Sulphur, Chloride, Ortho-Phosphate, Total Inorganic Phosphate
Clarifier, Softener, Filter-Alum pH, P/M-Alkalinity, Conductivity, Total Aluminium, Total Hardness, Total Calcium, Total Magnesium, Total Iron, Total Copper, Sodium, Silicate, Sulphur, Chloride
Clarifier, Softener, Filter-Lime pH, P/M-Alkalinity, Conductivity, Total Hardness, Filtered Hardness, Total Calcium, Total Magnesium, Total Iron, Total Copper, Sodium, Silicate, Sulphur, Chloride, Total Inorganic Phosphate
Sodium Zeolite, Dealkalizer, Desilicizer, Softened Make-up pH, P/M-Alkalinity, Conductivity, Total Hardness, Total Calcium, Total Magnesium, Total Iron, Total Copper, Sodium, Silicate, Sulphur, Chloride
Hydrogen Zeolite, Strong Acid Cation pH, P/M-Alkalinity, Conductivity, Total Hardness, Total Calcium, Total Magnesium, Total Iron, Total Copper, Sodium, Silicate, Sulphur, Chloride
Mixed Bed Exchanger, Degasifier, Anion Exchanger, Demineralizer Conductivity, Filtered Hardness, Total Hardness, Total Calcium, Total Magnesium, Total Iron, Total Copper, Sodium, Silicate, Reactive Silicate, Sulphur, Chloride
Deaerating Heater, Feedwater, Condensate Polisher pH, P/M-Alkalinity, Conductivity, Total Hardness, Total Calcium, Total Magnesium, Total Iron, Total Copper, Sodium, Silicate, Reactive Silicate, Sulphur, Chloride, Total Phosphate.
Blowdown – Expected Conductance >300 µS/cm pH, P/M-Alkalinity, Conductivity, Total Hardness, Total Calcium, Total Magnesium, Total Iron, Total Copper, Sodium, Silicate, Sulphur, Chloride, Nitrate, Ortho-Phosphate
Blowdown – Expected Conductance >300 µS/cm pH, P/M-Alkalinity, Conductivity, Total Hardness, Total Calcium, Total Magnesium, Total Iron, Total Copper, Sodium, Silicate, Silica Reactive, Sulphur, Chloride, Nitrate, Ortho-Phosphate
Steam Condensate Conductivity, Total Hardness, Total Calcium, Total Magnesium, Total Iron, Total Copper, Sodium, Silicate, Reactive Silica, Sulphur, Chloride

Cooling water analysis

Cooling tower is a heat removal devices used to eliminate waste heat of air released to atmosphere. This process allows airborne contaminants, organic matters and particles to become deposited into the cooling water. This, combined with the contaminants in the feed water, creates an environment for microorganism growth, solid deposits and scaling.

Improper treated cooling tower water could be an amplifier of biological hazardous agent. The warm and moist environment of a cooling tower favors the growth of Legionella bacteria which causes the outbreak of the deathly Legionnaires' disease. Thus, cooling tower water quality must be monitored in a regular basis to prevent spreading of diseases to users.

Test

Description

Make-up, Raw Water pH, P/M-Alkalinity, Conductivity, Total Hardness, Total Calcium, Total Magnesium, Total Iron, Total Copper, Total Manganese, Sodium, Total Silica, Sulphur, Chloride, Ortho-Phosphate, Total Inorganic Phosphate, Total Zinc
Cooling Tower, Air Washer pH, P/M-Alkalinity, Conductivity, Total Hardness, Total Calcium, Total Magnesium, Total Iron, Total Copper, Total Manganese, Sodium, Total Silica, Sulphur, Chloride, Ortho-Phosphate, Total Zinc
Sea water/Brine pH, P/M-Alkalinity, Conductivity, Total Hardness, Total Calcium, Total Magnesium, Total Manganese, Total Iron, Total Copper, Total Silica, Sulphur, Ortho-Phosphate, Total Zinc
High Cycle Tower, Jacket, Brine pH, P/M-Alkalinity, Conductivity, Total Hardness, Total Calcium, Total Magnesium, Total Manganese, Total Iron, Total Copper, Total Silica, Sulphur, Ortho-Phosphate, Total Zinc
Closed System, Glycol pH, Specific Gravity, Total Hardness, Total Calcium, Total Magnesium, Total Iron, Total Copper, Sodium, Total Silica, Sulphur, Chloride
Closed System, Non-Glycol pH, P/M-Alkalinity, Conductivity, Total Hardness, Total Calcium, Total Magnesium, Total Iron, Total Copper, Sodium, Total Silica, Sulphur, Chloride



Read more: https://www.lenntech.com/products/boiler-water-analysis.htm#ixzz4x5ZX3UHF

Ortofosfatos versus polifosfatos

La selección de un tratamiento de agua aditivo químico de fosfato puede ser una de las decisiones de tratamiento químico más difíciles que muchos de los sistemas públicos de agua harán. Esto es particularmente cierto porque la química de aditivos químicos de ortofosfato y polifosfato es complejo, y aditivos químicos de tratamiento de agua de fosfato están disponibles comercialmente en un número abrumador de mezclas químicas. Ortofosfatos y polifosfatos son sales derivadas de dos formas diferentes de ácido fosfórico. Ortofosfatos son moléculas pequeñas, formadas a partir de la forma más pequeña y la más básica de ácido fosfórico. Los polifosfatos son moléculas más grandes, formados a partir de una versión de cadena más larga de ácido fosfórico. A pesar de que las palabras de ortofosfato y polifosfato contienen la palabra "fosfato", estos dos compuestos químicos sirven radicalmente diferentes propósitos de tratamiento de agua. La falta de un sistema de servicio público a entender las diferencias significativas entre estos dos compuestos de tratamiento podría dar lugar a graves problemas de calidad del agua y las posibles violaciónes MCL. Una selección incorrecta de las mezclas químicas de fosfato mediante un sistema de servicios públicos podría incluso crear graves problemas de salud pública. En los sistemas públicos de agua, ortofosfatos se utilizan para fines de plomo y cobre la corrosión de control. Ortofosfatos reaccionan químicamente con los átomos de plomo y cobre que han lixiviado fuera de la tubería y han entrado en el agua circundante. Esta reacción química de ortofosfatos con átomos de plomo y cobre formas plomo y fosfato de cobre. El plomo y cobre fosfato es entonces electroquímicamente extrae de nuevo sobre la superficie de la tubería, donde se forma un revestimiento duro, resistente al agua en la tubería. Este revestimiento duro, resistente al agua ayuda a prevenir más lixiviación fuera de átomos de plomo y cobre en el agua circundante. La mayoría de los sistemas de servicios públicos han experimentado un éxito mucho mayor con el control de la corrosión de plomo ortofosfato de lo que han experimentado con el control de la corrosión del cobre ortofosfato. Los polifosfatos son agentes que son prácticamente ineficaces contra el plomo y la corrosión del cobre secuestrante. Cuando se secuestra un jurado en un juicio penal, que el jurado se "mantiene en reclusión." Un agente secuestrante químico es un agente químico que rodea otra molécula o átomo y sostiene que otra molécula o átomo "en reclusión." Al rodear la otra molécula o átomo y manteniéndolo en su aislamiento, el agente secuestrante química oculta la molécula o átomo de la vista y evita que entren en diversas reacciones químicas. Como un agente secuestrante, polifosfatos sólo secuestrar metales solubles "invisibles-en-agua" que no se han oxidado en sus formas insolubles. Polifosfato aplica al agua antes de que el agua se clora evitará hierro invisible y manganeso de convertirse en visible después de que el agua es clorada. Como un agente secuestrante, polifosfato de tratamiento de agua se utiliza para secuestrar átomos de hierro solubles que permanecen en agua sedimentada antes de que sea clorado o que de lixiviación fuera de la tubería de hierro en sistemas de distribución de agua. Por circundante y el secuestro de estos átomos de hierro solubles, se les impide la visualización de los colores rojizos típicos asociados con óxidos de hierro e hidróxidos de hierro. polifosfatos de tratamiento de agua también interfieren con la cristalización de y formación de escamas de calcio y carbonato de magnesio, pero no con la cystallization de y formación de escamas de hidróxido de magnesio. Si cualquiera de los átomos de manganeso solubles todavía están presentes en el agua después de que el flóculo se ha asentado fuera, polifosfatos también servirán para secuestrar estos átomos de manganeso solubles, evitando que se presentan el color típico de dióxido de manganeso oscuro. Un error bruto sobre polifosfato es la creencia de que el uso de secuestrantes de polifosfato para ocultar hierro y manganeso es una técnica de tratamiento casual, de rutina para la eliminación del exceso de hierro y manganeso que no se elimina durante los procesos de sedimentación y filtración de una planta de tratamiento de agua. En realidad, el uso de polifosfato para secuestrar hierro y manganeso que una planta no pudo eliminar durante los procesos de sedimentación y filtración es una maniobra desesperación. los quantites adversas de hierro y manganeso en el agua cruda deben estar debidamente oxidados por aireación, permanganato, o el ozono y deben ser depositados en depósitos de sedimentación como parte del floc. Polifosfatos, que secuestran hierro y manganeso por sólo un período limitado de tiempo, no son el ideal o la solución preferida para el hierro de cualquier planta de tratamiento de agua y problemas de manganeso. Los polifosfatos sólo deben utilizarse para atrapar las pocas partículas de hierro y manganeso que se perdieron durante el proceso de aireación y oxidación inicial. La mayoría de los compuestos de tratamiento de fosfato utilizados por los sistemas de tratamiento de agua públicos son en realidad mezclas de polifosfatos y ortofosfatos. Los polifosfatos se añaden habitualmente en su forma polifosfato de sodio o potasio. Ortofosfatos se añaden en forma de ortofosfato de sodio o de potasio o en una forma de ortofosfato que se mezcla con cloruro de zinc o sulfato de zinc. El zinc en la mezcla no juega ningún papel en la formación de los revestimientos que impiden plomo y cobre la corrosión. En cambio, el zinc juega un papel importante en la protección de superficies galvinized (medios galvanizado "recubierto de zinc") y en la prevención de las fibras de asbesto de la erosión fuera de las tuberías de amianto-cemento. Sin embargo, debe tenerse en cuenta, algunas mezclas de fosfato también pueden contener polifosfatos de zinc, pero las formulaciones de ortofosfato de zinc se utilizan mucho más comúnmente en las operaciones de tratamiento de agua pública. mezclas de tratamiento de agua de fosfato están disponibles en diferentes mezclas de decenas. No hay una mezcla perfecta que es de uso universal en todas las situaciones. Si un sistema de tratamiento de agua utiliza una mezcla con más polifosfato de que sus necesidades del sistema, los recubrimientos establecidos por el ortofosfato, se pueden quitar. Si un sistema de tratamiento de agua utiliza una mezcla de fosfato con más ortofosfato de que sus necesidades del sistema, el hierro puede ser despojado de distancia de las tuberías de hierro. plantas de tratamiento de agua deben evaluar regularmente los plomo, cobre, hierro, manganeso, y los niveles de asbesto en su agua y consultar con un especialista fosfato profesional siempre que un cambio en las mezclas de fosfato parece estar justificado. Sales de polifosfato COMUNES: pirofosfato de sodio ácido, pirofosfato de tetrasodio, pirofosfato de tetrapotasio, tripolifosfato de sodio, tripolifosfato de potasio, trimetafosfato de sodio, hexametafosfato de sodio (vítreo) COMUNES SALES ortofosfato: ortofosfato monosódico, monopotásico ortofosfato, ortofosfato de disodio, dipotasio ortofosfato trisódico ortofosfato, ortofosfato tripotásico, ortofosfato de zinc

post original por Bradley C. Williams en http://water-treatment-training.blogspot.com/2010/02/polyphosphates-and-orthophosphates.html

Orthophosphates versus Polyphosphates

The selection of a phosphate water treatment chemical additive can be one of the most difficult chemical treatment decisions that many public water systems will make. This is particularly true because the chemistry of orthophosphate and polyphosphate chemical additives is complex, and phosphate water treatment chemical additives are commercially available in an overwhelming number of chemical blends.

Orthophosphates and polyphosphates are salts derived from two different forms of phosphoric acid. Orthophosphates are small molecules, formed from the smallest and most basic form of phosphoric acid. Polyphosphates are larger molecules, formed from a longer chain version of phosphoric acid.

Even though the words orthophosphate and polyphosphate contain the word "phosphate," these two chemical compounds serve radically different water treatment purposes. A public utility system's failure to understand the significant differences between these two treatment compounds could result in serious water-quality problems and possible MCL violations. An incorrect selection of phosphate chemical blends by a public utility system could even create serious public health problems.

In public water systems, orthophosphates are used for lead and copper corrosion-control purposes. Orthophosphates chemically react with lead and copper atoms that have leached off of piping and have entered into the surrounding water. This chemical reaction of orthophosphates with lead and copper atoms forms lead and copper phosphate. The lead and copper phosphate is then electrochemically drawn back down onto the piping surface, where it forms a tough, water-resistant coating on the piping. This tough, water-resistant coating helps prevent further leaching off of lead and copper atoms into the surrounding water. Most public utility systems have experienced far greater success with orthophosphate lead corrosion control than they have experienced with orthophosphate copper corrosion control.

Polyphosphates are sequestering agents that are virtually ineffective against lead and copper corrosion. When a jury in a criminal trial is sequestered, that jury is "held in seclusion." A chemical sequestering agent is a chemical agent that surrounds another molecule or atom and holds that other molecule or atom "in seclusion." By surrounding the other molecule or atom and holding it in seclusion, the chemical sequestering agent hides the molecule or atom from sight and prevents it from entering into various chemical reactions. As a sequestering agent, polyphosphates will only sequester soluble "invisible-in-water" metals that have not been oxidized into their insoluble forms. Polyphosphate applied to water before the water is chlorinated will prevent invisible iron and manganese from becoming visible after the water is chlorinated.

As a sequestering agent, water treatment polyphosphate is used to sequester soluble iron atoms that remain in settled water before it is chlorinated or that leach off of iron piping in water distribution systems. By surrounding and sequestering these soluble iron atoms, they are prevented from displaying the typical reddish colors associated with iron oxides and iron hydroxides. Water treatment polyphosphates also interfere with the crystallization of and formation of calcium and magnesium carbonate scales, but not with the cystallization of and formation of magnesium hydroxide scales. If any soluble manganese atoms are still present in water after the floc has settled out, polyphosphates will also serve to sequester these soluble manganese atoms, preventing them from displaying the typical dark manganese dioxide color.

A gross misconception about polyphosphate is the belief that the use of polyphosphate sequestrants to hide iron and manganese is a casual, routine treatment technique for the removal of excess iron and manganese that was not removed during a water treatment plant's sedimentation and filtration processes. In reality, the use of polyphosphate to sequester iron and manganese that a plant failed to remove during the sedimentation and filtration processes is a desperation maneuver. Undesirable quantites of iron and manganese in raw water should be properly oxidized by aeration, permanganate, or ozone and should be deposited in sedimentation basins as part of the floc. Polyphosphates, which sequester iron and manganese for only a limited period of time, are not the ideal or the preferred solution for any water treatment plant's iron and manganese problems. Polyphosphates should only be used to catch the few particles of iron and manganese that were missed during the initial aeration and oxidation process.

Most phosphate treatment compounds used by public water treatment systems are actually blends of polyphosphates and orthophosphates. Polyphosphates are usually added in their sodium or potassium polyphosphate form. Orthophosphates are added in the sodium or potassium orthophosphate form or in an orthophosphate form that is mixed with zinc chloride or zinc sulfate. The zinc in the mixture plays no role in forming the coatings that prevent lead and copper corrosion. Instead, the zinc plays a significant role in protecting galvinized surfaces (galvanized means "zinc-coated") and in preventing asbestos fibers from eroding off of asbestos-cement piping. It should however be noted, some phosphate blends may also contain zinc polyphosphates, but zinc orthophosphate formulations are much more commonly used in public water treatment operations.

Phosphate water treatment mixtures are available in dozens of different blends. There is no perfect blend that is universally usable in all situations. If a water treatment system uses a blend with more polyphosphate than their system needs, the coatings laid down by the orthophosphate can be stripped away. If a water treatment system uses a phosphate blend with more orthophosphate than their system needs, iron can be stripped away from iron piping. Water treatment plants need to regularly assess the lead, copper, iron, manganese, and asbestos levels in their water and consult with a professional phosphate specialist whenever a change in phosphate blends seems to be warranted.

COMMON POLYPHOSPHATE SALTS: Sodium acid pyrophosphate, Tetrasodium pyrophosphate, Tetrapotassium pyrophosphate, Sodium tripolyphosphate, Potassium tripolyphosphate, Sodium trimetaphosphate, Sodium hexametaphosphate (glassy)

COMMON ORTHOPHOSPHATE SALTS: Monosodium orthophosphate, Monopotassium orthophosphate, Disodium orthophosphate, Dipotassium orthophosphate, Trisodium orthophosphate, Tripotassium orthophosphate, Zinc orthophosphate

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Cooling Product Testing and Control

With the extremely high cost of molybdenum in recent years, its use as a corrosion inhibitor or tracing agent in cooling water products, where product consumption is significant, has become essentially cost prohibitive. Other corrosion inhibitors such as phosphates, zinc, silicates, and organo- phosphorous compounds are now used largely in the absence of molybdates. Also, the use of molybdenum has been restricted in some areas because of environmental concerns, mostly centered around concentration limitations in municipally generated sludges.

Phosphates

Where orthophosphate or polyphosphates are in use, testing for the phosphate is a good and accurate test. There are a number of phosphate procedures, but all tests determine orthophosphate. Other forms of phosphate such as polyphosphate or organo-phosphates must first be converted to orthophosphate to determine their concentrations with a phosphate test procedure.

Control can become more complicated when there is phosphate in the makeup water. The form of the phosphate (orthophosphate, polyphosphate, or both) and the concentration range needs to be known so that it is accounted for in the cycled cooling water.

Example

Makeup water contains 0.5 ppm of orthophosphate and 0.4 ppm of polyphosphate as PO4. The cooling tower is operated at five cycles of concentration and a cooling water product that contains 4 % of orthophosphate is being applied. The desired inhibitor product dosage is 100 ppm.

At five cycles, there will be 2.5 ppm of orthophosphate from the makeup water orthophosphate, and 2.0 ppm of polyphosphate applied from the makeup water, but some of it will have reverted to orthophosphate. You should test for polyphosphate in the tower water initially and then periodically to determine the reversion rate for your system. Typically, we assume about a 50% reversion rate. The actual reversion rate will depend upon pH and retention time, and the specific type of polyphosphate.

If when tested the polyphosphate showed to be 1 ppm in the cycled tower water, then the total orthophosphate from the makeup would be 3.5 ppm. 100 ppm of the inhibitor product would add 4 ppm orthophosphate, so a tested residual of 7.5 ppm or orthophosphate would indicate that 100 ppm of the product was in the system.

Table 1: Phosphate Summary

Phosphate Concentrations

Orthophosphate (ppm)

Polyphosphate (ppm)

Makeup Water

0.5

0.4 as PO4

Tower Water,
5 Cycles Before Reversion

2.5

2.0

Tower Water, 5 Cycles After Reversion

3.5

1.0

Orthophosphate From Product

4.0

Total in Cycled Tower Water

7.5

1.0

 

Phosphonates

Most all cooling tower products contain one or more phosphonates that are used for scale inhibition, corrosion inhibition, or both. Phosphonate testing is not as accurate as phosphate testing, but they can be used for controlling product feed. Phosphonates are subject to oxidation to orthophosphate by chlorine or bromine and are lost to precipitation with cations such as calcium. If the system is chlorinated or brominated, assume a 20 – 30% degradation to phosphate. The actual amount can be determined by testing for residual phosphonates and phosphate.

There are several phosphonates tests that can be used:

Hach UV digestion, then phosphate test.
Boiling with acid and persulfate, followed by phosphate test. Palintest drop test.
Taylor drop test.

UV Digestion

The test procedure is the most accurate and has a reproducibility of about ± 10%. A persulfate reagent is used along with a UV light to decompose the organo-phosphate (phosphonate) to orthophosphate. An orthophosphate test procedure then determines the amount of phosphate contributed by the phosphonates. Any orthophosphate already present before the digestion is subtracted from the total orthophosphate after digestion. This can be done by adding reagent to the tower water that has not had the digestion and use this as the blank, or actually determine orthophosphate in the tower water and subtract it from the total orthophosphate determined after the persulfate digestion.

The amount of phosphorus in each specific phosphonate molecule varies, so there is a specific conversion factor from orthophosphate to phosphonate. Each ppm of orthophosphate created by HEDP digestion = 1.085 ppm HEDP. The phosphorus content of PBTC is much lower. Each ppm of orthophosphate created from the digestion of PBTC = 2.84 ppm of the PBTC molecule.

Phosphonate Test Example:

The cycled tower water has 6 ppm orthophosphate and a cooling water product that contains 2.5% PBTC and 1.8% HEDP is being applied at a desired dosage of 120 ppm.

Assuming all of the phosphonates remain as phosphonates and have not been oxidized in the cooling tower by bromine or chlorine and assuming it has not been lost to precipitation, you should get 3.05 ppm of orthophosphate from the phosphonates after a persulfate / UV digestion.

Table 2: Phosphate Summary

From PBTC: 120 ppm x 2.5% = 3 ppm
3 ppm PBTC
÷ 2.84 ppm PBTC per ppm PO4 =

1.06 ppm orthophosphate

From HEDP: 120 ppm x 1.8% = 2.16 ppm

2.16 HEDP ÷ 1.085 ppm HEDP per ppm PO4 =

1.99 ppm orthophosphate

From orthophosphate in the tower water:

6 ppm

Total orthophosphate in sample after digestion:

9.05 ppm

Orthophosphate from phosphonate digestion:

3.05 ppm

 

Boiling With Acid and Persulfate

A digestion can also be accomplished by adding acid and persulfate, then boiling for about 30 minutes. If just acid were used, only polyphosphate would be hydrolyzed or reverted to orthophosphate. It persulfate is also added, the organo-phosphates and polyphosphates will be digested to orthophosphate. This test would be more applicable for samples that do not have polyphosphates, since the test will not distinguish between orthophosphate developed from phosphonates or polyphosphates.

Phosphonate Drop Counts

We recommend the Palintest procedure. This procedure is less accurate and subject to interferences. It is best to determine the number of drops on a known product concentration and relate the number of drops to that concentration. It is advisable to also compare these results initially and periodically to the digestion method.

Where PBTC is in use, the Palintest method is preferred. The procedure buffers the pH to around 3.0 and is more effective at detecting the PBTC along with the HEDP and AMP.

On the Palintest method, each 0.7 ppm of HEDP or AMP in the water should require one drop of titrant, and each 2.0 ppm of PBTC should require one drop.

Polyphosphate and some organics will interfere with the test and show up as phosphonates. To account for this, a blank is run on the makeup water. If it takes two drops for the color change on the blank, then those two drops are subtracted from the test results of the treated water. Note that the blank results are not cycled up by the tower cycles. Polyphosphates revert to orthophosphate which does not interfere and experience has shown that cycling the blank should not be done. If the product contains polyphosphate and a residual in the cycled water, it will increase the number of drops required.

If fluorides are in the cycled tested water at > 1.0 ppm, this causes a substantial interference that may disqualify the drop test procedure from being usable. It is advisable to check with the city supplier to see if they add fluorides and at what level. If high fluorides are present, an idea that may work is to first run the drop test procedure on the tower water to get a baseline number. Then take a sample of the cycled tower water and add 100 ppm of product and see how many drops are required. Subtract the number of drops used for the baseline from the drops required for the 100 ppm sample to determine how many drops represent 100 ppm of product as a basis for setting control limits.

The Palintest end point is the drop when the color change from green/gray to blue/purple first occurs.

Palintest Phosphonate Drop Count Example:

The cooling water is treated with 140 ppm of a product that contains 2.5% PBTC and 1.8% HEDP. The product has a specific gravity of 1.16. There is no fluoride in the water.

First, determine the interferences in the makeup water by running the test procedure on an untreated sample. On this example assume it took two drops.

Next, make a 100 ppm solution. To do this add 1 gram or 0.86 mL (1mL/1.16 gram/mL) of the chemical product to 99 grams (99 mL) of makeup water. Mix this up well, then add 1 gram (1 mL) of this 1% solution to 99 grams (99 mLs) of makeup water. This is now a 0.01% solution or 100 ppm of the product. This would place 1.8 ppm of HEDP and 2.5 ppm of PBTC in the solution. Run the phosphonates test on this solution, and for this example it required the theoretical number of drops of about 6.

Table 3: Theoretical Phosphonate Titrant Usage

From HEDP: 1.8 ppm ÷ 0.7 ppm HEDP / Drop

2.5 Drops

From PBTC: 2.5 ppm ÷ 2.0 ppm PBTC / Drop

1.25 Drops

From Blank:

2 Drops

Total Drops:

5.75 drops, which will require 6 drops to see the color change.

140 ppm of product would be about (140 ÷ 100) x 4 drops = 5.6 drops or 5-6 drops + 2 drops for the blank = 8 drops. This can be confirmed by making a 140 ppm solution and testing it.

Azole, Zinc, or Silica Tests

The Hach test procedures for azole, zinc, or silica can be used to check product dosage if the specific ingredient is in the applied product. Remember, as with phosphonates, the applied concentrations and actual residuals can be different. Azole residuals decrease as they film with copper. Zinc is lost as it precipitates at the cathode or in the bulk water. Silica is lost as it films metal surfaces. In establishing control ranges and dosages, take into account some of this loss. For example, we may apply azole at 2 ppm, but have a desired residual in the water of only 1 ppm.

Mass Balance

Chemical dosages should be confirmed by mass balances and compared to chemical testing. Mechanisms should be set up on each system to conveniently determine water makeup, cycles, water loss, and chemical consumption. The concentration in the recirculating water should be calculated from the actual product usage and blowdown or water loss.

Mass Balance Example:

The cooling tower is operating at five cycles of concentration. The makeup meter shows 120,000 gpd makeup. At five cycles, this is a water loss of 24,000 gpd. The product being fed contains 1.8% HEDP, 2.5% PBTC, 1.5% BZT, and 1% zinc; and the desired dosage is 100 ppm.

Daily product use determined by drum level and confirmed with drawdown cylinder testing is 28 lbs per day. This is a calculated applied dosage of 140 ppm of product in the cycled cooling tower water (140/120 x 24,000/1000 = 28 lbs).

Chemical testing showed 4 drops of phosphonates (6 drops from the test – 2 drops for the blank), which was previously determined to represent 100 ppm product. Testing also revealed 1.5 ppm BZT and 0.8 ppm of zinc residuals in the water. All of the chemical tests show that some portion of the active component has been consumed or residuals would have been higher at 140 ppm of applied product.

Product Component

Expected Residuals with No Loss When Applied at 140 ppm

Calculated Dosage Based on Actual Residual

Product Loss to System Reactions

Phosphonate

8 drops

6 drops

= 100 ppm Product

40 ppm Product

BZT

2.1 ppm

1.5 ppm BZT

= 100 ppm Product

40 ppm product

Zinc

1.4 ppm

0.8 ppm Zinc

= 80 ppm Product

60 ppm Product

 

Conclusion

Mass balance is the most accurate way to determine applied dosage. If the product dosage was projected to be effective at 100 ppm, it is likely that this product is being overfed by 40%. Chemical testing suggests that there is more than sufficient residual of active components even after some loss to the system, so product dosage can be lowered and results monitored to confirm that desired results are maintained. There is expected to be some loss of active components as they react with the materials in the system and the impurities in the water.

Where molybdate is used or has been used as a monitoring method for product control and consumption, generally its loss to the system is minimal. That means that if the product shown above contained 1% molybdate as Mo,

it is likely that the test results would have been very close to 1.4 ppm Mo and the product dosage would have been decreased to 100 ppm to lower Mo to 1.0 ppm. Molybdate used as a tracer, then, would commonly yield a lower product usage rate because the other active components would not ordinarily be used to control the dosage.

Reduccion del uso de agua en torres de enfriamiento con automatización

Con la iniciativa del Estado para reducir el consumo de agua en un 20 por ciento para el año 2020, muchas plantas en California están tratando de ser más respetuosos con el medio ambiente. Una de esas instalaciones incluye un hospital líder en California, que trató de reducir los costos de tratamiento de agua para su sistema de climatización. El hospital cuenta con tres sistemas de torres de enfriamiento individuales que dan servicio a tres enfriadores centrífugos, con un total combinado de 2.800 toneladas de capacidad.

El programa de tratamiento de agua actualmente en uso en la instalación estaba operando a 2,8 ciclos de concentración, resultando en 35,7 por ciento de la composición agua de la torre se sangró a la alcantarilla por el proveedor de tratamiento actual. Teniendo en cuenta la calidad del agua en la zona, estos eran los ciclos máximos de concentración que podrían lograrse sin emplear el uso de reblandecimiento ácido o agua. El ahorro que el hospital solicitó se realizaron mediante la revisión de varias formas de optimizar el programa de tratamiento de agua. Trabajando en estrecha colaboración con el Departamento de Agua y Energía (LADWP) Los Ángeles, se reveló que mediante la introducción de un programa de conservación de agua para reducir el uso del agua a través de mayores ciclos de concentración, la instalación realidad ahorraría más dinero que se gastaría para alterar el programa , por lo que el proyecto propuesto sostenible.

A través de pruebas y análisis de laboratorio, el equipo fue capaz de concluir que seis ciclos de concentración podrían alcanzarse, resultando en sólo el 16,7 por ciento del agua de maquillaje torre siendo desangrado en el sistema de tratamiento de alcantarillado. Esto se podría lograr mediante la introducción de un sistema de alimentación de ácido seguro que minimizaría escala, la corrosión y el ensuciamiento microbiológico para permitir el aumento de ciclos de concentración al mismo tiempo proteger personal de la instalación entre en contacto con los productos químicos.

La evaporación de la torre de refrigeración sigue siendo el mismo, pero el agua de Estados Unidos fue capaz de reducir la purga, cortando el consumo de agua en un estimado de 3.6 millones de galones por año y la disminución de los costos de agua y alcantarillado. La planta fue capaz de ahorrar más de $ 76.000 (ver Fig. 1).

química en cualquier momento en la torre de refrigeración está estresado por la adición de más ciclos, se requiere un control estricto de la química para evitar la formación de incrustaciones. Esto llevó a la introducción de controles de automatización avanzada de agua de Estados Unidos. El programa de automatización avanzada incluye notificaciones de vigilancia y alarmas inalámbricas para gestionar el rendimiento general del programa, y ​​el equipo de conductividad, pH, los niveles de inhibidor de incrustaciones, el uso de la torre de maquillaje, y la utilización de la torre de purga monitoreado.

En un momento dado, el personal del hospital y los representantes designados de agua de Estados Unidos, utilizando varios niveles de seguridad de la contraseña-protegida indicado por la instalación, se puede acceder de forma segura los datos para la revisión y ajuste en línea. Si los parámetros designados cayeron encima o por debajo del intervalo especificado, un representante de aguas US fue alertado para una respuesta rápida (véase Fig. 3).

Segundo para riego, torres de enfriamiento ofrecen el mayor potencial de ahorro de agua en California. Como un incentivo adicional, el estado de California ha puesto en marcha programas para rebajar la instalaciones para el coste de la automatización de sus sistemas. LADWP y el Distrito Metropolitano de Agua (MWD), por ejemplo, ofrecen tres programas que financian la automatización de las torres de enfriamiento debido a su capacidad para aumentar ciclos de concentración, lo que reduce el consumo de agua.

 

Esta permitido la financiación de agua de Estados Unidos para implementar el programa de automatización avanzada $ 34.000 a monitorear y controlar el programa de tratamiento de agua para este hospital sin costo alguno para el hospital.

Los resultados hasta la fecha para la instalación incluyen la reducción significativa en el consumo de agua, el agua baja y las facturas de aguas residuales y un control más eficiente debido a la automatización de software instalado para proteger los bienes de equipo.

You will find this article here: http://www.waterworld.com/articles/iww/print/volume-14/issue-5/columns/case-study/hospital-reduces-water-usage-in-cooling-towers-with-automation.html

HOSPITAL REDUCES WATER USAGE IN COOLING TOWERS WITH AUTOMATION

With the state's initiative to reduce water usage by 20 percent by the year 2020, many plants in California are striving to become more environmentally friendly. One such facility includes a leading California hospital that sought to reduce water treatment costs for its HVAC system. The hospital has three individual cooling tower systems that service three centrifugal chillers, with a combined total of 2,800 tons of capacity.

The water treatment program currently in use at the facility was operating at 2.8 cycles of concentration, resulting in 35.7 percent of the tower water makeup being bled to the sewer by the current treatment provider. Given the water quality in the area, this was the maximum cycles of concentration that could be achieved without employing the use of acid or water softening.

The savings that the hospital sought were realized by reconsidering various ways to optimize the water treatment program. Working closely with the Los Angeles Department of Water and Power (LADWP), it was revealed that by introducing a water conservation program to reduce water use through increased cycles of concentration, the facility would actually save more money than it would spend to alter the program, making the proposed project sustainable.

Through testing and lab analysis, the team was able to conclude that six cycles of concentration could be attained, resulting in only 16.7 percent of the tower makeup water being bled into the sewer treatment system. This could be achieved through the introduction of a safe acid feed system that would minimize scale, corrosion and microbiological fouling to enable the increase in cycles of concentration while also protecting facility staff from coming into contact with the chemicals.

The evaporation of the cooling tower remained the same, but U.S. Water was able to reduce blowdown, cutting water usage by an estimated 3.6 million gallons per year and decreasing water and sewage costs. The plant was able to save over $76,000 (see Fig. 1).

Anytime chemistry in the cooling tower is stressed by adding more cycles, tight control of the chemistry is required to prevent scale formation. This led to the introduction of U.S. Water's advanced automation controls. The advanced automation program included wireless monitoring and alarm notifications to manage the overall program performance, and the equipment monitored conductivity, pH, scale inhibitor levels, tower makeup usage, and tower bleed usage.

At any given time, designated hospital personnel and U.S. Water representatives, using various levels of password-protected security outlined by the facility, can securely access the data for review and online adjustment. If designated parameters fell above or below the specified range, a U.S. Water representative was alerted for quick response (see Fig. 3).

Second to irrigation, cooling towers offer the largest potential for water savings in California. As an added incentive, the state of California has put programs in place to rebate facilities for the cost of automating their systems. LADWP and the Metropolitan Water District (MWD), for example, offer three programs that finance automation for cooling towers due to their ability to increase cycles of concentration, which reduces water use.

This financing allowed U.S. Water to implement the $34,000 advanced automation program to monitor and control the water treatment program for this hospital at no cost to the hospital.

Results to date for the facility include significant reduction in water usage, lower water and sewage bills and more efficient monitoring due to the installed automation software to protect the equipment assets.

You will find the article at: http://www.waterworld.com/articles/iww/print/volume-14/issue-5/columns/case-study/hospital-reduces-water-usage-in-cooling-towers-with-automation.html

Cooling Tower Molybdate Disapearence

A customer had a cooling tower system with pH control, a molybdate traced scale/corrosion inhibitor, and bleach-based biocide program. The operators contacted their water management specialist with concerns about why their tested molybdate levels were so low. Their results did not correspond with the amount of scale/corrosion inhibitor being feeding into the system.

What factors could affect the tested molybdate levels in a cooling tower system? Take a few moments to consider the system diagram below and think of what could cause this.

City Makeup

Cooling Tower Blowdown Process

3005NSS Feed

Citric Acid Feed

Bleach Feed

Cooling Towers 279

 

Problems such as this can be very perplexing and can have several causes. Sometimes, you have to go the extra mile to get the answer. This is exactly what the Associate in charge of this account did.

Applied Chemistry

The chemistry applied to the cooling tower system was:

  • 3005NSS - a molybdate-containing scale and corrosion inhibitor
  • Citric acid - pH control
  • Bleach - an oxidizing biocide used for microbiological control

 

Possible Causes of Low Molybdate Readings

  • Low Cooling Tower Cycles: Running the cooling tower are lower cycles of concentration will result in lower molybdate levels even though the 3005NSS feedrate was the same. This was not the case in this situation.
  • 3005NSS Underfeed: Underfeeding the 3005NSS would directly affect the tested molybdate residuals; however, the theoretical feed rate and actual feed rate compared closely to one another.
  • Chemical Line Leak: A leak in the 3005NSS chemical line would obviously reduce the amount of chemical fed to the cooling tower, but no leak was found.
  • Improper Product Blend: It is rare, but not impossible to get a product that has been blended improperly. Being able to do a dilution to test product concentrations is a skill all professional water treatment experts should possess. A sample of 3005NSS was diluted and tested for molybdate concentration. The tested molybdate level was very close to the theoretical level expected.
  • Loss of Chemical Component in System: Some chemistries are naturally lost in the system due to evaporation or consumption.

Molybdate is nonvolatile and consumption to form a protective passivated layer on the metal surfaces should be minimal once the chemistry has been established. Molybdate was not being lost in the system.

  • Test interference: An expert water treater should be aware of possible interferences to the tests he runs. The analysis procedures manuals for the colorimeters and spectrophotometers do a great job listing these interferences. An initial review of these interferences showed nothing in the system that should be interfering with the molybdate testing. Both the bleach feed and citric acid feed were Cooling Towers 280 new additions to the treatment program and corresponded to the approximate time that the operators started having problems with their molybdate testing. The analysis interference chart showed that it would take a chlorine reading of 7.5 ppm to cause interference. The free chlorine levels had never been anywhere near that high in the system. The analysis interference chart did not specifically list citric acid; however just because something isn't listed does not mean it is not an interference.

Checking for Citric Acid Interference

The water management associate telephoned the water analysis manyfacturer to ask if citric acid interfered with molybdate testing. They were unsure but recommended a test be conducted to determine if it did.

A dilution of 3005NSS was prepared. This dilution was divided into several containers and the pH was adjusted to various levels using citric acid and sulfuric acid (as a control). The results were as follows:

Table 1 - Citric Acid Interference Determination

Acid Used                   Sample pH                  Molybdate (ppm)

Citric                           6.7                              0.7

Citric                           6.3                              0.3

Citric                           4.9                              0.0

Sulfuric                       7.0                              1.6

Sulfuric                       6.2                               1.5

 

As Table 1 shows, the citric acid was indeed an interference.

Conclusion

Through the detective work of the water management associate, citric acid was determined to be the interference with the low range molybdate testing.

The next steps required were to:

  • Ensure the theoretical 3005NSS dosage was being fed on a daily basis while citric acid was still being fed to the cooling tower.
  • Discuss the pros and cons of sulfuric acid feed with the customer so the inhibitor levels can be properly measured

Boiler Carryover – Cause, Effect and Prevention

Mechanisms

carryover or primingCarryover also known as priming is any solid, liquid or vaporous contaminant that leaves a boiler with the steam. In low/medium pressure boilers (<100 bar) entrained boiler water is the most common cause of steam contamination.

Both mechanical factors such as boiler design, high water levels, load characteristics and chemical factors such as high solids concentration, excessive alkalinity, presence of contaminants contribute to the creation of carryover.

Two of the most common mechanical causes of carryover are operation in excess of design load and sudden increases in load.

Foaming is one of the mechanisms of chemical carryover. Foaming tendencies are increased with increases in alkalinity and solids content. Stable foam bubbles contain boiler solids and are carried forward with the steam giving rise to carryover.

Oil and other organic contaminants can react with boiler water alkalinity to give crude surface active materials which cause foaming and carryover.

Effects

Boiler water solids carried over with steam will form deposits in non-return and other control valves. Process streams can be contaminated by carryover affecting product quality.

Deposition in superheaters can lead to failure due to overheating and corrosion.

Steam turbines are potentially prone to damage by carryover as deposits on turbine blades creates imbalance reducing efficiency and capacity. Solid particles in steam can lead to erosion and corrosion in both turbines and other equipment.

 

Prevention of Carryover

The prime means of preventing carryover is to have good mechanical steam separation devices. For low/medium pressure fire tube boilers where steam purity is not stringent, gravity separation is normally satisfactory. (At least 14 bar and saturation conditions the density of water is 115 times greater than that of steam). As steam pressure rises the difference in density reduces (at 69 bar water is only 20 times more dense than steam) making gravity separation less effective. Steam separators are then used to improve purity and are usually installed in the steam drum of water tube boilers.

Primary separators utilise the difference in density as the means of separation bypassing steam through a series of baffles which reduces turbulence or centrifugal (cyclone) separators.

Secondary separators, where steam is directed in a frequently reversing pattern through a large contact surface. A mist of boiler water collects on the surface and is drained from the unit.

Control of boiler water chemistry is essential to minimise carryover and allow mechanical separation to work effectively. The parameters that must be controlled are:

  • Total dissolved solids
  • Alkalinity
  • Silica
  • Organic contamination.

These should be maintained within the boiler manufacturer guidelines or those of BS 2486.

Whenever carryover is being caused by excessive boiler water concentrations an increase in boiler blowdown rate is normally the simplest and most expedient solution. If carryover is still occurring and increasing blowdown is uneconomic then the addition of antifoam agents can economically reduce carryover. Use of an antifoam may allow the boiler to operate at higher water concentrations, Feedwater offer a product called Defoamer C which is suitable for this job, for more information visit the product page for product usage guidance.

Read more at https://feedwater.co.uk/boiler-carryover-cause-effect-prevention/

 

Prueba de biocidas en el fracturamiento hidráulico

Resumen

Fractura hidráulica o 'fracking' es un proceso utilizado en la industria de petróleo y gas para mejorar la productividad de un aceite o de gas bien. Implica la fracturación de roca con agua (mezclada con arena y algunos productos químicos) inyectado en un pozo bajo alta presión y se utiliza comúnmente en shale gas y otras fuentes 'no convencionales' de petróleo y gas.

No convencionales de petróleo y Gas fuentes

Fracturamiento hidráulico se utiliza generalmente en camas de gas de esquisto, gas de aceite apretado camas o camas de gas de carbón. Todos son fuentes de petróleo o de gas que se encuentran en diferentes tipos de formación rocosa y son por lo general difícil para una empresa hacer económico sin fracturación hidráulica de perforación de gas o petróleo. Por esta razón que se conoce como una técnica de 'estimulación bien'. Aunque el proceso ha sido utilizado en los últimos 50 años, recientemente es prominente en el debate público debido a la expansión de la técnica en los Estados Unidos y las preocupaciones sobre las consecuencias de su uso generalizado.

Agua utilizada en el 'Fracking'

El proceso de 'fracking' implica la perforación de que un pozo agujero subterráneo profundo, a menudo con una etapa horizontal cuando un lecho de roca es particularmente bajo. La roca es fracturada luego utilizando explosivos que crean pequeñas fisuras en la roca que ayudan el flujo de petróleo y gas fuera de la cama en el pozo. Es la baja porosidad de la roca que requiere el fracturamiento hidráulico para hacer un bien económico. Sin fracturación hidráulica, el pozo no produciría suficiente petróleo y gas a hacer vale la pena hacer.

Agua, arena y algunos productos químicos son inyectados al pozo bajo presión para garantizar estas fisuras que abren bajo la enorme presión causada por las formaciones de roca por encima de la cama de roca blanco. Es la arena que sostiene las fisuras abiertas a menudo unos pocos milímetros de ancho. Una gran cantidad de agua (millones de galones) se utiliza en una sola frack y el agua puede provenir de muchas fuentes diferentes, por ejemplo, agua dulce, agua saladas o reciclado de agua de un anterior proceso de fracturamiento hidráulico.

 

Los productos químicos que pueden agregarse al agua y el propósito detrás de su adición se enumeran en el Apéndice E del informe de la EPA en el fracturamiento hidráulico de 2011. Puede encontrar una versión resumida en el cuadro 4.

 

 

Figura 6 se tiene el informe de la EPA en fracturamiento hidráulico, página 13.

 

 

Figura 7 se tiene el informe de la EPA en fracturamiento hidráulico, página 13

 

La mayoría de los productos químicos agregados son los normalmente utilizados en otros procesos industriales que utilizan agua y se añaden para mantener la integridad del pozo, por ejemplo, tensioactivos, inhibidores de corrosión, reguladores de pH y reductores de fricción.

Los biocidas se añaden al agua para evitar la acumulación de bacterias en el agua que puede llevar a la corrosión ácida o la creación de compuestos de sulfuro en. Crecimiento bacteriano puede afectar la producción de pozos de petróleo y gas y puede ser introducido en el fluido de fracturamiento hidráulico de diversas fuentes como la fuente de agua y el apuntalante. Apuntalante es que el término usado para la arena (o de otros compuestos) espera que abren las fisuras.

                                   

La tabla 4 se enumeran los tipos de productos químicos agregados al agua y su propósito. Se toma del informe de la EPA, página 29.

  

Prueba de agua dulce utilizado en el fracturamiento hidráulico

De los productos químicos añadidos al agua, el analito principal que se debe probar en el sitio antes de la inyección es el biocida. Ellos son probados en sitio debido a su volatilidad inherente que hace muestreo y fuera del sitio de prueba inadecuado.

Biocidas que se utilizan incluyen isotiazolona, glutaraldehído, cloro y dióxido de cloro. Otra vez estas son biocidas de uso frecuente en otros procesos industriales utilizando agua como torres de refrigeración.

La tasa de dosificación de biocidas es a menudo automatizada usando un método amperométrico en línea que añade el biocida en cantidades controladas, dependiendo de la velocidad de flujo del agua a introducirse al pozo de la fuente de agua. Secundario de método se realiza generalmente para calibrar la línea en la punta de prueba y como cheque aguas abajo del punto de inyección para biocida está presente en la concentración correcta en el líquido antes de que finalmente se inyecta en el pozo.

 

Pruebas de biocidas en el agua la puede ser difícil debido en parte a la tendencia creciente del uso de agua reciclada para núcleos de frack. Más tradicionales métodos colorimétricos de la prueba (como el método DPD para la cuantificación de cloro o concentraciones de dióxido de cloro) pueden ser desperdiciador de tiempo y difícil para los ingenieros; no pueden dar resultados consistentes donde el agua es alto en sólidos disueltos/suspendido. Otros métodos como ORP (potencial de oxidación-reducción) son fácil de usar pero sufren de una falta de selectividad y a menudo no se puede utilizar como una herramienta cuantitativa.

Ha habido una tendencia creciente dentro de las empresas de tratamiento de agua (que tienden a ser subcontratado por la empresa de perforación para administrar la dosificación de biocidas en el agua) a utilizar nuevos métodos como los sensores amperométricos desechables ya utilizados por el ChlordioXense. Estos métodos tienen la ventaja de ser fácil de utilizar y no son susceptibles a resultados inexactos, como se ha visto con métodos colorimétricos.

Prueba de agua 'Producidos' en el fracturamiento hidráulico

Reflujo de agua es el agua que fluye a la superficie durante y después de la terminación de fracturamiento hidráulico. Consiste en el fluido utilizado para fracturar la pizarra y contiene arcillas, aditivos químicos, los iones metálicos disueltos y sólidos totales disueltos (TDS). El agua tiene un aspecto turbio de altos niveles de partículas en suspensión. La mayor parte del reflujo se produce en las etapas iniciales del proceso de fracturamiento hidráulico mientras que el resto puede ocurrir más de una semana tres periodo de tiempo. El volumen de recuperación es generalmente menos de la mitad del volumen que se inyectó inicialmente en el pozo. El resto del líquido sigue siendo absorbido en la formación de la pizarra.

En cambio, ' agua ' es producida naturalmente agua que se encuentra en formaciones de esquisto que fluye a la superficie durante toda la vida entera del gas bien. Esta agua tiene altos niveles de TDS e iones metálicos como el calcio, hierro y magnesio. También contiene hidrocarburos disueltos junto con el natural materiales radiactivos (norma).

Históricamente, esta aguas residuales del proceso de fracturamiento hidráulico fue eliminada en estanques de evaporación grande. Esto sin embargo se ha convertido en socialmente inaceptable y las aguas residuales deben ser tratadas como residuos industriales de la misma manera que se trata el agua de otros procesos industriales. Las opciones disponibles para empresas de tratamiento de agua la industria del petróleo y el gas son bien 'inyección directa' en el suelo a profundidades por debajo de la mesa de agua y entre las capas de roca impermeable, o el tratamiento y la disposición del agua en la superficie del agua. Ambos métodos a menudo emplean tratamiento de agua con biocidas.

Prueba de concentración de biocidas en las aguas residuales puede ser imposible sin filtrar el agua que generalmente conduce a una reducción en el biocida para determinar la verdadera concentración en el líquido es difícil. La demanda de biocida del líquido también es muy alta debido a la cantidad de metales disueltos presentes. Por lo tanto, biocidas como el dióxido de cloro son generalmente mezclados con agua en concentraciones de hasta 20 mg/l y dosificados en el agua producido o reflujo. Como con el tratamiento de agua dulce que se describe en la página anterior, un método de sonda amperométrica en línea se utiliza para controlar la tasa de dosificación y un método secundario tales como el Palintest ChlordioXense utilizado para calibrar la sonda y proporcionar un método de comprobación secundaria.

Hay una tendencia creciente dentro de la industria de tratamiento de agua para recuperar el hydocarbons que están presentes en el agua de producción y venderlos en el mercado abierto. El uso de biocidas como el dióxido de cloro ayuda a aumentar la tasa de recuperación de aceite como tratamiento hace que los sólidos a precipitado fuera de solución y los hidrocarburos para instalarse en la parte superior del líquido tratado.

El dióxido de cloro actúa como un Desemulsificante para romper emulsiones a través de oxidación química, permitiendo que el agua separar hidrocarburos residuales, productos químicos y la materia particulada presente.


El agua suele ser de una buena calidad suficiente para ser reutilizada en otro sitio de frack o eliminarse mediante inyección directa. Los hidrocarburos pueden despumados y vendidos a las compañías petroleras, mientras que el lodo sólido es retirado y transportado a una planta de aguas residuales estándar.

La imagen de agua de producción (a la derecha) tratados con dióxido de cloro (a la izquierda).

 

Resumen

El uso de fracturamiento hidráulico como un proceso para incrementar los rendimientos de los núcleos de gas y petróleo está aumentando, especialmente en los Estados Unidos, y su uso casi con toda seguridad se extenderá a otros países.

Los biocidas son parte fundamental del fluido de fracturamiento hidráulico sí mismo y el tratamiento de las aguas residuales del proceso.

Principalmente se han adoptado métodos de prueba para la cuantificación de las concentraciones de biocida en el agua dulce y las aguas residuales de la industria de agua potable donde la matriz de agua es de una composición mucho 'más limpia'. Métodos colorimétricos y ORP, aunque útiles, tienen sus inconvenientes y así nuevos métodos como la ChlordioXense son ser fácilmente adoptados por la industria de petróleo y gas.

      

 

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