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Biopolymer Technology for Cooling Water Treatment Presentation at the Amsterdam International Water Week Conference I. Steemers-Rijkse, R.W. Witte Novochem Water Treatment, P.O. Box 390, 3430 AJ Nieuwegein, The Netherlands i.steemers@novochemgroup.com

Abstract: At industrial processing, water is being used for heat transport purposes. Heat exchangers and cooling

tower systems eliminate excessive heat, giving rise to corrosion, hardness deposition, pollution and

microbiological growth. To prevent blockage, leaks, loss of efficiency and as a result of that production problems,

a small amount of water treatment chemicals is being dosed. Toxic and non-biodegradable compounds, like zinc,

polyacrylate, phosphonate and phosphates additives are discharged with the water blow down and burden the

environment.

Novochem Water Treatment developed biodegradable, low phosphate water treatment products based on

biopolymers. The technology is unique in the international market for chemical water treatment and appeared

to outperform the traditional chemicals. The outcome is a higher efficiency and a decrease in maintenance

resulting in lower production costs.

The background of the biopolymer technology is being described as well as the conversion of three field

applications of traditional water treatment programs.

Keywords: antiscalant; biodegradable; biopolymer; cooling water; corrosion inhibitor; sustainable

Introduction

At industrial processing a huge amount of water is being used for heat transport purposes.

Excessive heat is transferred to the water by heat exchangers. To cool down the heated

water, most water systems are equipped with counter flow air cooling towers. This is

accompanied with evaporation of water, so the naturally present salts get concentrated. To

avoid infinite accumulation of salts, part of the cooling water is being discharged and

supplemented with fresh make-up water.

The conditions appearing in these kind of water systems give rise to corrosion, hardness

deposition, pollution and microbiological growth. To prevent blockage, leakage, loss of

efficiency and consequently production problems, a small amount of water treatment

chemicals is being dosed. For microbiological control biocides are used, while corrosion

inhibitors, antiscalants and dispersing agents are dosed to prevent corrosion and deposition.

Every year approximately 1800 tons of corrosion inhibitors, antiscalants and dispersing

agents are being discharged to the aquatic environment of just The Netherlands, due to the

blow down of water (Bloemkolk, 1995). Worldwide it is a multiple thereof. Currently the

additives are based on toxic and non-biodegradable compounds, like zinc, polyacrylates,

phosphonates and phosphates (IPPC, 2001), which accumulate and affect the environment.

Moreover they are from a non-sustainable fossil origin.

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With growing pressure and legislation on environmentally damaging compounds and its

mission statement to work on sustainable solutions, Novochem Water Treatment started in

1999 a research project on developing biodegradable alternatives. With a grant of the Dutch

Ministry of Economic Affairs in 2003 a breakthrough was made by using biopolymers from

agricultural origin having hardness stabilizing properties (Steemers-Rijkse et al., 2005).

Ongoing research resulted in a full product line of corrosion inhibitors, antiscalants and

dispersing agents.

With its biopolymer basis, low phosphorous content and the sole use of biodegradable

compounds, the technology is both on the source and discharge side an environmental

friendly solution that is unique in the international market for chemical water treatment.

In this paper three cases of cooling water applications with the biopolymer technology are

being presented, replacing a Polyphosphate, an All Organic and a Zinc based program.

Biodegradable water treatment technology

The historical development of cooling water treatment chemicals starts with the use of

polyphosphates, chromate and zinc compounds as corrosion inhibitors (Farooqi et al. 2000).

Acids are being dosed to prevent deposition of hardness salts.

With the discovery of phosphonates and polyacrylate structures [Figure 1], the deposit

control could be handled at a more alkaline pH of the cooling water (General Electric, 1997-

2012). Since the eighties this ‘all organic’ treatment program was the most environmental

friendly solution.

Serious problem of the all organic program (Gledhill et al., 1992) is the character not to be

broken down in the environment. But also the use of scarce fossil sources gave a pulse to

the development of carboxylated structures of e.g. saccharides (Verraest et al., 1996),

aspartate (Hasson et al., 2011) and chitosan (Zeng, 2013). Novochem Water Treatment

discovered a specific polymer of agricultural origin [Figure 2], which appeared to have

excellent properties in hardness and iron stabilization surpassing the performance of the

traditional polyacrylate structures.

Figure 1 polyacrylate (petrol source). Figure 2 biopolymer (renewable source).

The toxic and persistent corrosion inhibitors like zinc and phosphate are substituted by

environmental friendly ‘adsorption inhibitors’. By forming a hydrophobic film, the inhibitors

protect the metal surface against corrosion [Figure 3]. In contrast to a zinc, polyphosphate

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and all organic treatment, the efficiency of the adsorption inhibitor is independent of the

cooling water pH, leading to a wide application field.

Carrier

Inhibitor .

Figure 3 Adsorption Inhibitor mechanism.

Novochem Water Treatment developed a full range of biodegradable water treatment

products based on biopolymers and adsorption inhibitors. Surface active compounds have a

dual function; As carrier for the adsorption inhibitor molecules and as a biodispersant, thus

leading to an one drum treatment program. The biobased products with solely

biodegradable compounds are introduced into the market in 2005 as NovoPure and

registered under the brand name NovoTraqua® in 2011.

Case 1; Polyphosphate conversion to Biopolymer

A Chemical Company in the North of The Netherlands discharges cooling water of an open

evaporating cooling water system of 6MW indirectly into “De Waddenzee”. Make-up water

is tap water. Start situation: Treatment with a Stabilized Polyphosphate program (12 - 16

ppm phosphate) with pH control (pH 7.2) by sulphuric acid dosage. Microbiological control is

done by shot feed dosage of hypochlorite at a level of 1 ppm free chlorine and a dosage of a

biodispersant. Bad performance of the water treatment program resulted in corrosion and

blockage of the plate heat exchangers, followed by a restricted cooling capacity. Another

problem was the exceedance of sulphur and phosphate discharge limits.

At the beginning of 2013 a start-up was made with one of the NovoTraqua® biopolymer

programs to improve the corrosion control and to meet the discharge levels of the

authorities. No system cleaning was conducted. For microbiological control shot feed

dosage of hypochlorite at a level of 1 ppm free chlorine was unaltered, but the separate

biodispersant dosing was stopped. At the start-up the dosage of sulphuric acid was

immediately decreased towards a cooling water pH level of 8.3. After 10 weeks undisturbed

production, the sulphuric acid dosage was stopped completely and the pH raised to a level

of 8.8. In this situation the Langelier Saturation Index (Langelier, 1936) is +2.8 (at 50°C).

Results Case 1

Immediately after start-up the hardness stabilization came above 100% which was not

achieved with the polyphosphate treatment. Also iron and phosphate levels increased due

to the biopolymer ability of dispersing old deposits. After a couple of weeks the levels

diminished and stabilized at a normal, lower level. Ending the acid dosage the hardness

transport remained at a level of at least 100%, which indicates that no scale is being formed.

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Since the program change, the cooling water system shows a much better performance.

Old lime, phosphate an iron scale slowly disappeared. The system efficiency improved

significant and the discharge demands are met. With the hydrophobic layer of the

adsorption inhibitors the corrosion inhibition improved from < 3 mpy to < 1 mpy [Picture 4].

The production progress is no longer disturbed and total costs are greatly reduced [Table 5].

Picture 4 Corrosion result with NovoTraqua® before and after coupon cleaning.

Table 5 Results of the polyphosphate - versus the biopolymer program.

Stab. Polyphosphate treatment NovoTraqua® treatment

Scale formation Severe deposits due to corrosion; Hard

structure Hardly any scale; Soft structure

Corrosion < 3 mpy < 1 mpy

Safety Use of H2SO4 No acid dosage

Environment Non-biodegradable;

exceedance of P and S levels

Biodegradable;

P and S levels below limits

Cooling capacity Restricted No restriction

Production stops 2x per year; costs 2x M€ 0.5 >> 1 year

Case 2; All Organic conversion to Biopolymer

A 82 MW evaporating cooling water system in the South of the Netherlands is using

flocculated surface water as make-up. Discharge is back to river “De Maas”. For a long time

the system was treated with an all organic program. As a result of high temperatures,

process coherent blocking of cooling water and low water flows, deposition of lime (calcium

carbonate) wasn’t in control. The severe hardness deposition caused blockage in the heat

exchangers and a high frequency of necessary maintenance stops [Picture 6]. As a result of

this, the production capacity was limited and the costs of maintenance very high.

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Picture 6 Blockage of heat exchanger pipes due to lime scale (All Organic 2007).

To improve the cooling performance a start-up was made with a biopolymer program of

Novochem Water Treatment in 2010, after a maintenance stop whereat heat exchangers

were cleaned. Biocide regime is unaltered; Chlorine shock dosage at a level of 0.5 - 1 ppm

free chlorine.

Results Case 2

Initial problems with an extreme high Langelier Saturation Index (> 3.0), microbiological

explosion (due to a combination of process leakage and microbiological polluted make-up

water) and dosing pumps were all overcome. From the beginning of the biopolymer

treatment water analyses showed at least 100% hardness stabilization, resulting in an

increase of cooling capacity [Figure 7].

Figure 7 Increase in cooling capacity with NovoTraqua® treatment program.

In contrast to the all organic treatment, the biopolymer program keeps the performance

of the coolers a long time at the initial level after cleaning. The period between maintenance

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stops is stretched from every 6 months to at least 14 months. And even then the coolers are

hardly polluted and much less extensive cleaning operations is needed [Picture 8].

Picture 8 Open heat exchanger pipes (NovoTraqua® 2012).

The cooling towers show also a significant improvement in water flow and decrease in

hardness scale pollution. Production losses due to insufficient cooling capacity are history

and maintenance costs are diminished.

Case 3; Zinc conversion to Biopolymer

At an ethylene/propylene production plant in Azerbaijan the open evaporating cooling

water system of 290MW was treated with a zinc product and sulphuric acid for pH control.

Make-up is filtrated surface water and discharge is into the Caspian Sea. Change to a

biopolymer program was induced by problems with heat transfer because of insufficient

hardness stabilization. After three months of operation the tubes of the heat exchanger

were fully blocked. The desire to stop acid dosing because of the potential hazard to

employees and the wish to use a more environmental friendly type of water treatment

chemical, were also arguments for change.

Start-up with the biopolymer product was made in 2013 without prior system cleaning.

Objective was to reduce the acid dosage in steps to zero.

Results Case 3

Due to equipment failure, the acid dosage stopped immediately at start-up instead of slowly

decreasing the level. But after 1 week, when the NovoTraqua® concentration reached the

required amount of 50 ppm, the product was able to stabilise the hardness for at least

100% [Figure 9]. Since that moment the hardness transport through the system is in control.

Corrosion rates are at a level of 1 - 3 mpy, which is a good result [Figure 9].

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Figure 9 Analysing data NovoTraqua® treatment program.

As expected, at regular maintenance stops hardly any scale is seen in the heat exchanger

pipes and corrosion rate is low [Picture 10].

Picture 10 Heat exchanger (NovoTraqua® 2014).

Discussion

One of the arguments for expected failure on biopolymer application, is the probability of

premature decomposition. The presented cases however show that the potency of

biodegradation does not disturb the efficacy of the NovoTraqua® compounds. Sufficient

molecular stability guarantees undisturbed process operation.

Another aspect is the question if a biodegradable program causes an increase of the

biocide consumption. In all three cases this was not seen, neither in any other cases. On the

contrary, a decrease of microbiological pollution was observed due to the biodispersant

activity of the program.

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As most programs fail in hardness scale control in the presence of iron and general

pollution, the biopolymer technology proves its superiority by an undisturbed performance.

Important issue which emerges from all applications, is the property to disperse old (lime)

scale into the water. This means that pre-cleaning is not required a priori. It makes the

technology also very robust, because temporary exceedance of the application limits can be

handled without off-line cleaning.

Conclusions

In the course of the years of application, the NovoTraqua® technology showed not only to be

beneficial to the environment, but also to outperform the traditional water treatment

chemicals. The strong dispersing capacity of the biopolymers and the excellent corrosion

inhibition of the adsorption inhibitors result in cleaner systems. The outcome is a higher

efficiency, a decrease in maintenance and so production costs. For the industry the ultimate

focus, next to a green solution.

References

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