Accepta Newsletter #9: Membrane Technology, Boiler Water Oxygen Scavengers

Cost Effective Membrane Technologies for Minimising Wastes and Effluents: A Guide to Best Practice

Membrane Technologies: This Guide (a free copy of which can be obtained by contacting Accepta) focuses specifically on industrial-scale membrane separation technologies. These technologies are particularly effective for the recovery and re-use of both water and raw materials from process streams and can be an important component of any waste minimisation initiative.

Waste reduces a company's profitability, and many businesses are now altering their processes to minimise the impact of waste on their bottom line and on the environment. Annual cost savings of up to 1% of overall company turnover are proving to be typical results of waste minimization programmes.

There are technologies commercially available that can help businesses to do this. This Guide explains the basic principles of one of them, membrane technology. It examines the technologies, explaining the basic principles of operation, discussing appropriate applications and assessing their relative advantages and disadvantages. It also offers guidance to membrane selection and gives specific Industry Examples of companies that have reduced costs by installing membrane separation.

Membrane separation is mature technology that is commercially available in the UK from a number of equipment suppliers. The technology can be used to separate various mixtures of liquid materials in a growing range of applications. Units are generally compact, and their modular construction means that they can be scaled up or down easily.

There are three main types of membrane system commonly used in industry:

Correctly used membrane separation can provide financial savings and conserve resources. Maximum benefits are obtained when one or both the output streams from the membrane system are recycled or re-used, thereby reducing process materials requirement and minimising waste disposal costs.

The benefits of using membrane separations are only fully realised by selecting technology that is compatible with the application. This will involve consultation with technology suppliers, clear identification of the substances present in process streams, an understanding of the strengths and weaknesses of the membrane systems available and completion of a structured feasibility assessment.

The guide covers some of the following issues:

Boiler Water: Oxygen Associated Metallic Corrosion and the use of Oxygen Scavengers

Following last months introductory article on boiler water treatment, we now take a more detailed look at specific boiler water related problems; oxygen associated metallic corrosion and the accumulation of 'sludge' within a boiler system. We also consider how these problems can be overcome looking at specific solutions.

Oxygen is a significant factor in the corrosion of metals, so if you can remove the oxygen from water you can reduce the negative effects of corrosion. Oxygen scavengers do just that; they are products that can be added to the boiler water that help to remove oxygen and so reduce the problems associated with corrosion.

There are several types of oxygen scavenger: organic and inorganic, the difference being that inorganic products add dissolved solids to the water. This means that you have to increase the amount of 'blowdown' given to the boiler to maintain conditions free from boiler water carryover. Also, inorganic oxygen scavengers tend to be temperature dependent and so the lower the boiler feed water temperature the more chemical you need to add. An example of an inorganic oxygen scavenger is Sulphite, whereas examples of organic oxygen scavengers are Tannins, DEHA, and Carbohydrazide.

One method used to reduce the amount of oxygen in boiler feed water is to maintain as high a temperature as possible. This is because increasing the water temperature can drive off the oxygen in gaseous form. It is therefore essential to ensure good feed tank design, and that as much condensate as possible is returned to the system. The use of condensate is preferable for heating the feed tank rather than a steam sparge or external heat source, because it is a recycled heat source and so helps to conserve energy and reduce operating costs.

Advantages to the use of sulphite are that the higher the feed water temperature the less sulphite is required, its low cost and it is colourless as a product. One disadvantage is that sulphite adds to the 'dissolved solids' and so leads to more system 'blowdowns'.

Tannins, DEHA and Carbohydrazide are not temperature dependent and do not add to the 'dissolved solids' and hence blowdown is reduced relative to a sulphite treated boiler, however, these products are slightly more expensive than sulphite.

It is important to calculate the dosage rate for all types of product and to examine the overall system design before choosing the most suitable oxygen scavenger.

Accepta have a number of excellent oxygen scavengers that act to absorb oxygen from boiler water and so help prevent oxygen associated corrosion:

Accepta 2011 - Sulphite; a cost effective catalysed oxygen scavenger. For best results use a proportional dosing pump based on feed-water use. Can also be used to remove Chlorine from water (NOT potable/drinking water).

Accepta 2072 - Sulphite; an efficient catalysed sodium sulphite product used to absorb oxygen in steam boiler systems. Dose ideally to feed tank to allow time for the oxygen to be absorbed before entering the steam boiler.

Accepta 2012 - Tannin based oxygen scavenger. It is not dependant on the feed-water temperature and being organic it does not add to the boiler water conductivity so reducing the need for blowdown (compared with Sulphite).

Accepta 2061 - DEHA based oxygen scavenger, provides outstanding protection from oxygen corrosion along with excellent feed-water and boiler system passivation. It can be used as a replacement for hydrazine in any boiler up to 125 bar without the associated safety hazards and handling precautions. Accepta 2061 is volatile and alkaline, contributing no dissolved solids or ammonia to the boiler system.

Accepta 2065 - Carbohydrazide, an organic corrosion inhibitor used for scavenging oxygen and passivating metal surfaces. It can be used as a direct replacement for hydrazine in any boiler without the associated safety hazards and handling precautions. It can be used in boilers of any pressure, up to and including supercritical (220 bar g), and can be fed into feed-waters used for spray attemperation.

For more information please email Accepta, visit our web site www.accepta.com or simply call on +44 (0) 1625 267 581.

As you use a steam boiler you introduce small quantities of hardness salts together with traces of suspended matter into the feed-water. Over time the concentrations of these salts and suspended matter builds up and if not treated properly they can settle on to heat transfer surfaces, eventually 'baking' on to form a hard crystalline scale. Certain types of water treatment chemicals (phosphates for example), if added incorrectly could also precipitate and add to this scale problem. To avoid such situations, you should consider using polymers to prevent the suspended solids from settling and 'baking' on. The polymer products do this by keeping the unwanted matter in solution, which can then be removed via the boiler blowdown.

Polymers that are specifically designed to assist with the removal of iron are also available. These should be used to remove corrosion by-products from the boiler. If these by-products are not removed they can settle on other metal surfaces causing bi-metallic corrosion or even under deposit corrosion.

Accepta have a number of very effective 'sludge' conditioners that help prevent suspended solids baking onto heat transfer surfaces causing loss of heat transfer, inefficiencies etc;

Accepta 2014 - Polymer; steam boiler scale inhibitor and internal metal passivator. Use in softened water make-up systems (max 3ppm hardness). Can also be used in systems up to 70 bar g.(1000psi). Accepta 2014 complies with FDA regulations. It is best to use this product on clean boilers as it may remove existing scale deposits.

Accepta 2016 - Combined phosphate and polymer treatment for steam boiler systems up to 1500psi g. Used as a scale inhibitor and suspended solids control agent. Best for softened and low hardness water. The Phosphate reacts with the hardness whilst the polymer provides transport of the Calcium, Magnesium, Iron, Phosphate and Silica through the boiler, preventing scales adhering to the metal surfaces. Use direct from the drum or mixed with soft water or cool condensate in a dosing tank.

For more information please email Accepta, visit our web site www.accepta.com or simply call on +44 (0) 1625 267 581.

Businesses are starting to realise that reducing all forms of waste, whether it is energy, raw materials or other resources, cuts costs and results in improved profits. However, many look upon water bills as a fixed cost, outside of their control. This is far from true. 'Envirowise' suggest most companies can save between 20-50% on their water and effluent charges by reducing water use. All water used must eventually be discharged as effluent, incurring a charge from the water company based on its volume, chemical oxygen demand (COD) and total suspended solids (TSS). This is especially so in the textile and leather industries due to the large amounts of water used.

Before introducing any measures to save water, it is essential to know the current level of water use and to have the means of measuring future consumption. It is important to identify where water currently enters and leaves the building, and also how it is used. This will help you to detect leaks and identify areas with the potential for the greatest savings. Doing this should also help to highlight the true costs associated with water use. These include not only the purchase and disposal prices, but also the costs of pumping, treatment, loss of valuable materials in effluent, and the costs of maintaining the distribution network.

Having identified where potential water savings can be made, the next step is to introduce appropriate water-saving measures. This may involve installing devices such as sensors and cut-off controls for pumps, or counter-current rinse systems. It will involve a range of good 'housekeeping' practices and training to raise staff awareness. Few employees will be aware that one washroom tap left trickling, instead of being properly turned off, could cost £42 per year in water and effluent charges. A 25 mm hose, left running at 66 litres per minute, wastes 4000 litres per hour and could add over £45,000 to the annual water services bill.

An important area for textile and leather producers to consider is the re-use of water, for example, in cleaning or cooling operations. It may be possible to introduce counter-current rinsing to the process. This consists of rinsing the product in a series of tanks or stages, each using progressively cleaner water. The rinse water is re-used by moving it progressively from the last rinse tank towards the first. Wash water may also be suitable for re-use elsewhere on site, such as for floor washing, rinsing containers or making up raw materials slurries. If used water is treated to remove impurities or recover lost raw materials, it may open up other possibilities for re-using it.

Cutting water and wastewater costs needs to be approached systematically and should:

Information supplied by Groundwork, for further details contact +44 (0) 870 241 5886.

For more information please email Accepta, visit our web site www.accepta.com or simply call on +44 (0) 1625 267 581.

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	Accepta Newsletter: Issue # 9 Welcome to issue # 9 of Accepta's popular newsletter, I hope you find the articles we've included this month informative and helpful. If there are any specific topics or issues you'd like to see covered please let me know, 'click here'.
	Articles in issue # 9: Cost Effective Membrane Technologies for Minimising Wastes and Effluents: A Guide to Best Practice. Boiler Water: Oxygen Associated Metallic Corrosion and the use of Oxygen Scavengers. Boiler Water: 'Sludge' and the use of Sludge Conditioners. Water Efficiency in the Textile Industry. ********************
	Cost Effective Membrane Technologies for Minimising Wastes and Effluents: A Guide to Best Practice Membrane Technologies: This Guide (a free copy of which can be obtained by contacting Accepta) focuses specifically on industrial-scale membrane separation technologies. These technologies are particularly effective for the recovery and re-use of both water and raw materials from process streams and can be an important component of any waste minimisation initiative. Waste reduces a company's profitability, and many businesses are now altering their processes to minimise the impact of waste on their bottom line and on the environment. Annual cost savings of up to 1% of overall company turnover are proving to be typical results of waste minimization programmes. There are technologies commercially available that can help businesses to do this. This Guide explains the basic principles of one of them, membrane technology. It examines the technologies, explaining the basic principles of operation, discussing appropriate applications and assessing their relative advantages and disadvantages. It also offers guidance to membrane selection and gives specific Industry Examples of companies that have reduced costs by installing membrane separation. Membrane separation is mature technology that is commercially available in the UK from a number of equipment suppliers. The technology can be used to separate various mixtures of liquid materials in a growing range of applications. Units are generally compact, and their modular construction means that they can be scaled up or down easily. There are three main types of membrane system commonly used in industry: Ultrafiltration is widely used for: oil, water and emulsion separations; paint recovery; and the separation of fats, oils or greases in the food industry. Reverse osmosis and nanofiltration are used extensively for water purification, desalination and disinfection. Microfiltration is applied to maintain degreasing process solutions for metal particle recovery/removal or to concentrate other particulate materials from liquids or slurries. Correctly used membrane separation can provide financial savings and conserve resources. Maximum benefits are obtained when one or both the output streams from the membrane system are recycled or re-used, thereby reducing process materials requirement and minimising waste disposal costs. The benefits of using membrane separations are only fully realised by selecting technology that is compatible with the application. This will involve consultation with technology suppliers, clear identification of the substances present in process streams, an understanding of the strengths and weaknesses of the membrane systems available and completion of a structured feasibility assessment. The guide covers some of the following issues: Why minimise waste? Why install a membrane separation system? Membrane technology How to select a membrane process Ultrafiltration Reverse osmosis and nanofiltration Microfiltration Other commercially available technologies To obtain your full copy of the guide For your free copy of the full guide please e-mail Accepta or call us on +44 (0) 1625 267 581. Boiler Water: Oxygen Associated Metallic Corrosion and the use of Oxygen Scavengers Following last months introductory article on boiler water treatment, we now take a more detailed look at specific boiler water related problems; oxygen associated metallic corrosion and the accumulation of 'sludge' within a boiler system. We also consider how these problems can be overcome looking at specific solutions. Why should you worry about oxygen in boiler water? Oxygen is a significant factor in the corrosion of metals, so if you can remove the oxygen from water you can reduce the negative effects of corrosion. Oxygen scavengers do just that; they are products that can be added to the boiler water that help to remove oxygen and so reduce the problems associated with corrosion. Oxygen scavengers There are several types of oxygen scavenger: organic and inorganic, the difference being that inorganic products add dissolved solids to the water. This means that you have to increase the amount of 'blowdown' given to the boiler to maintain conditions free from boiler water carryover. Also, inorganic oxygen scavengers tend to be temperature dependent and so the lower the boiler feed water temperature the more chemical you need to add. An example of an inorganic oxygen scavenger is Sulphite, whereas examples of organic oxygen scavengers are Tannins, DEHA, and Carbohydrazide. Reducing oxygen One method used to reduce the amount of oxygen in boiler feed water is to maintain as high a temperature as possible. This is because increasing the water temperature can drive off the oxygen in gaseous form. It is therefore essential to ensure good feed tank design, and that as much condensate as possible is returned to the system. The use of condensate is preferable for heating the feed tank rather than a steam sparge or external heat source, because it is a recycled heat source and so helps to conserve energy and reduce operating costs. Sulphite Advantages to the use of sulphite are that the higher the feed water temperature the less sulphite is required, its low cost and it is colourless as a product. One disadvantage is that sulphite adds to the 'dissolved solids' and so leads to more system 'blowdowns'. Tannins, DEHA & Carbohydrazide Tannins, DEHA and Carbohydrazide are not temperature dependent and do not add to the 'dissolved solids' and hence blowdown is reduced relative to a sulphite treated boiler, however, these products are slightly more expensive than sulphite. Product selection It is important to calculate the dosage rate for all types of product and to examine the overall system design before choosing the most suitable oxygen scavenger. Accepta have a number of excellent oxygen scavengers that act to absorb oxygen from boiler water and so help prevent oxygen associated corrosion: Accepta 2011 - Sulphite; a cost effective catalysed oxygen scavenger. For best results use a proportional dosing pump based on feed-water use. Can also be used to remove Chlorine from water (NOT potable/drinking water). Accepta 2072 - Sulphite; an efficient catalysed sodium sulphite product used to absorb oxygen in steam boiler systems. Dose ideally to feed tank to allow time for the oxygen to be absorbed before entering the steam boiler. Accepta 2012 - Tannin based oxygen scavenger. It is not dependant on the feed-water temperature and being organic it does not add to the boiler water conductivity so reducing the need for blowdown (compared with Sulphite). Accepta 2061 - DEHA based oxygen scavenger, provides outstanding protection from oxygen corrosion along with excellent feed-water and boiler system passivation. It can be used as a replacement for hydrazine in any boiler up to 125 bar without the associated safety hazards and handling precautions. Accepta 2061 is volatile and alkaline, contributing no dissolved solids or ammonia to the boiler system. Accepta 2065 - Carbohydrazide, an organic corrosion inhibitor used for scavenging oxygen and passivating metal surfaces. It can be used as a direct replacement for hydrazine in any boiler without the associated safety hazards and handling precautions. It can be used in boilers of any pressure, up to and including supercritical (220 bar g), and can be fed into feed-waters used for spray attemperation. Additional Information For more information please email Accepta, visit our web site www.accepta.com or simply call on +44 (0) 1625 267 581. Boiler Water: 'Sludge' and the use of Sludge Conditioners As you use a steam boiler you introduce small quantities of hardness salts together with traces of suspended matter into the feed-water. Over time the concentrations of these salts and suspended matter builds up and if not treated properly they can settle on to heat transfer surfaces, eventually 'baking' on to form a hard crystalline scale. Certain types of water treatment chemicals (phosphates for example), if added incorrectly could also precipitate and add to this scale problem. To avoid such situations, you should consider using polymers to prevent the suspended solids from settling and 'baking' on. The polymer products do this by keeping the unwanted matter in solution, which can then be removed via the boiler blowdown. Iron removal Polymers that are specifically designed to assist with the removal of iron are also available. These should be used to remove corrosion by-products from the boiler. If these by-products are not removed they can settle on other metal surfaces causing bi-metallic corrosion or even under deposit corrosion. Products Accepta have a number of very effective 'sludge' conditioners that help prevent suspended solids baking onto heat transfer surfaces causing loss of heat transfer, inefficiencies etc; Accepta 2014 - Polymer; steam boiler scale inhibitor and internal metal passivator. Use in softened water make-up systems (max 3ppm hardness). Can also be used in systems up to 70 bar g.(1000psi). Accepta 2014 complies with FDA regulations. It is best to use this product on clean boilers as it may remove existing scale deposits. Accepta 2016 - Combined phosphate and polymer treatment for steam boiler systems up to 1500psi g. Used as a scale inhibitor and suspended solids control agent. Best for softened and low hardness water. The Phosphate reacts with the hardness whilst the polymer provides transport of the Calcium, Magnesium, Iron, Phosphate and Silica through the boiler, preventing scales adhering to the metal surfaces. Use direct from the drum or mixed with soft water or cool condensate in a dosing tank. Further Information For more information please email Accepta, visit our web site www.accepta.com or simply call on +44 (0) 1625 267 581. Water Efficiency in the Textile Industry Businesses are starting to realise that reducing all forms of waste, whether it is energy, raw materials or other resources, cuts costs and results in improved profits. However, many look upon water bills as a fixed cost, outside of their control. This is far from true. 'Envirowise' suggest most companies can save between 20-50% on their water and effluent charges by reducing water use. All water used must eventually be discharged as effluent, incurring a charge from the water company based on its volume, chemical oxygen demand (COD) and total suspended solids (TSS). This is especially so in the textile and leather industries due to the large amounts of water used. Before introducing any measures to save water, it is essential to know the current level of water use and to have the means of measuring future consumption. It is important to identify where water currently enters and leaves the building, and also how it is used. This will help you to detect leaks and identify areas with the potential for the greatest savings. Doing this should also help to highlight the true costs associated with water use. These include not only the purchase and disposal prices, but also the costs of pumping, treatment, loss of valuable materials in effluent, and the costs of maintaining the distribution network. Having identified where potential water savings can be made, the next step is to introduce appropriate water-saving measures. This may involve installing devices such as sensors and cut-off controls for pumps, or counter-current rinse systems. It will involve a range of good 'housekeeping' practices and training to raise staff awareness. Few employees will be aware that one washroom tap left trickling, instead of being properly turned off, could cost £42 per year in water and effluent charges. A 25 mm hose, left running at 66 litres per minute, wastes 4000 litres per hour and could add over £45,000 to the annual water services bill. An important area for textile and leather producers to consider is the re-use of water, for example, in cleaning or cooling operations. It may be possible to introduce counter-current rinsing to the process. This consists of rinsing the product in a series of tanks or stages, each using progressively cleaner water. The rinse water is re-used by moving it progressively from the last rinse tank towards the first. Wash water may also be suitable for re-use elsewhere on site, such as for floor washing, rinsing containers or making up raw materials slurries. If used water is treated to remove impurities or recover lost raw materials, it may open up other possibilities for re-using it. Cutting water and wastewater costs needs to be approached systematically and should: Involve all members of staff. Develop a clear, understandable plan. Establish the true costs of water and wastewater. Identify all water inputs and outputs. Allocate annual water consumption between major users. Implement all feasible water-saving options. Information supplied by Groundwork, for further details contact +44 (0) 870 241 5886. Further Information For more information please email Accepta, visit our web site www.accepta.com or simply call on +44 (0) 1625 267 581.







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