Speedy samples

Figure 1. Industrial process water analysis.

Hundreds of samples make their way to in-house or contract petrochemical water quality testing laboratories every day, but traditional wet chemistry analysis is a slow process, only capable of handling 20 to 30 samples per hour. Even measuring just one sample can require multiple tests, carried out by specialist staff, involving up to 150 ml of samples per test and often creating litres of waste. These laborious, traditional methods create a bottleneck, preventing petrochemical companies from making fast decisions and responding to risks within their manufacturing process.

The most recent developments in discrete cell technology and advanced ion chromatography are changing the status quo. With desktop, automated solutions that produce multiparameter results in a fraction of the time – and with minimal reagents unlike traditional wet chemistry methods – water quality testing laboratories are becoming effective business protectors and optimisers.

Water quality testing: protector and optimiser

The dual purpose of the water quality testing laboratory is to protect and optimise industrial processes. By understanding the exact composition of water at every stage, intelligent decisions can be made and interventions actioned. Here, the key to success is accurate and timely measurement, but this is no easy feat.

High-purity water protects equipment from corrosion and scaling, but the production of this water requires costly deionisation resins, expensive regeneration chemicals and energy-intensive methods. As purified water moves through steam generators and cooling towers, its composition changes and it requires careful monitoring.

Regular, precise process water monitoring provides information to process engineers so that they can adjust the water composition as required: corrosion inhibitors can be added to protect downstream equipment or further deionisation can be used to remove corrosion-causing ions. To provide this level of intelligence, scientists in water quality testing laboratories must measure many parameters, including pH levels, conductivity, alkalinity, total hardness and corrosion indicators. This careful measurement ensures process water reaches the required standards, equipment is protected against corrosion, scaling, and safety and regulatory standards are met.

When engineers understand the precise composition of process water, deionisation technology can be optimised, saving costs and ensuring energy-efficient regeneration of the resin beds.

Traditional wet chemistry methods are preventing fast responses

For decades, water utilities and testing laboratories have been relying on traditional wet chemistry methods. With this approach, basic water analysis is carried out with pH and conductivity meters, whereas more detailed analysis of corrosive anions, and corrosion inhibitors and indicators, are carried out with a complex array of titration, spectrophotometry and flow injection analysers (FIA).

Each test requires a separate sample and often multiple sequential tests are needed to analyse one sample, which extends the testing process. Added to this, wet chemistry analysis often requires large water samples and substantial amounts of reagents, resulting in sizeable waste volumes. With slow processes and the need for specialist staff to run and monitor equipment, water quality testing is labour-intensive, time-consuming and inefficient.

Figure 2. Water utilities and testing laboratory challenges with limited laboratory resources.

Ultimately, these traditional methods create bottlenecks within water quality testing laboratories, meaning the tests that are designed to protect and optimise the business cannot deliver results in time to drive the most effective decisions. This results in intervention delays that allow corrosive ions to continue to flow and deionisation inefficiencies to escalate. Testing many samples for diverse parameters and concentrations can create a bottleneck with limited laboratory resources (Figure 2).

Making the shift to high throughput multiparameter testing

To realise the full benefits of water quality testing, speed is essential. Any delays in processing samples can result in safety issues. If delays are considerable, water quality can be significantly compromised, causing safety concerns and stopping regulatory standards from being met.

The latest developments in discrete cell technology and advanced ion chromatography offer a more effective solution compared to traditional wet chemistry techniques. These automated, desktop technologies can take water samples from anywhere in the petrochemical process and provide quick and detailed reports on all key testing criteria.

Discrete cell technology provides integrated photometric and electrochemical analysis for nearly all water streams, including incoming raw water, groundwater, seawater, rainwater, municipal water, drinking water and wastewater. Multiparameter testing includes:

• Basic water metrics, such as pH, conductivity, total hardness and alkalinity.
• Corrosive ions, such as fluoride, chloride and sulfate.
• Scale-forming ions, including calcium, magnesium and silica.
• Corrosion inhibitors, including ammonia, zinc, molybdenum and nitrite.
• Corrosion indicators, such as total iron, hexavalent chromium and zinc.
• Wastewater profiles, including total Kjeldahl nitrogen (TKN), total phosphate, nitrate, boron and aluminium (Figure 3).

Figure 3. Multiparameter testing enabled by discrete analyser and high-pressure ion chromatography.

Multiple water samples from different sources are loaded into the machine along with similarly small amounts of reagent. The technician can then walk away while the machine calibrates, creates aliquots, completes the analysis, and generates a report.

The real power of these systems comes in the speed and volume of reports that can be generated. Indeed, models, such as the Thermo ScientificTM GalleryTM Plus discrete analyser, can accommodate 108 samples and 42 reagents to run up to 350 tests/hr.

Discrete cell analysers require much lower sample and reagent volumes than wet chemistry methods and the volume of wastewater generated by each run is reduced from litres to millilitres. With a high degree of automation, these systems free senior analytical chemists to work on additional projects, bringing their knowledge and experience to other areas of the business.

In most cases, discrete cell technology is complemented by advanced ion chromatography, which can measure the precise sub parts per billion (ppb) levels of trace ions in ultra-pure process water streams, such as deionised water, make-up water and steam condensate. Modern high-pressure ion chromatography requires no reagents and generates high pure eluents from purified water, negating the need for hazardous chemical handling.

A broad range of analytes can be measured rapidly and accurately to the sub ppb level, even in complex matrices by the Thermo ScientificTM DionexTM ion chromatography system. This rapid measurement means that continuous online monitoring is possible, providing an almost real-time status on process water quality. With continual and reliable corrosive ions and corrosion indicators and inhibitors monitoring, process engineers can take remedial action sooner.

Using automation to drive agile water quality analysis

Traditional wet chemistry techniques are inefficient and wasteful, causing unnecessary costs and delays. These inefficiencies prevent petrochemical companies from taking full advantage of water quality testing to protect assets, deliver cost-effective deionisation and diagnose issues quickly.

By combining a discrete analyser with advanced high-pressure ion chromatography, water quality testing laboratories can reduce waste, decrease costs and increase capacity. Teams are fully enabled to realise their capability to drive efficiencies and safety in petrochemical processing.

With the information needed for data-driven decisions, safety and regulatory standards are met. But petrochemical companies are further empowered to react more quickly to changes in all water streams and better protect their valuable assets, such as steam generators and boilers. By accurately measuring pure water streams, deionisation processes are adjusted quickly, reducing the cost of these energy- and chemical-intensive processes.

Written by Hari Narayanan, Thermo Fisher Scientific, USA.

Read the article online at: https://www.hydrocarbonengineering.com/special-reports/04052021/speedy-samples/