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Testimonial

"...we have found IRmadillo to be stable, robust, precise and well suited for industrial on-line applications”

Senior Development Engineer International Forest Products Company

The IRmadillo for Monitoring Pulp and Paper Manufacturing

Pulp and paper manufacturing is a chain of complex chemical processes involving hazardous chemicals, different temperature profiles and variable natural materials. This can make process monitoring and control difficult, and traditional approaches have significant drawbacks and issues. Paper mills use substantial amounts of chemicals, water and energy, and require effective recycling of these resources to be financially viable. Real-time process analytics can dramatically improve the efficiency of this process, so how can this be achieved with the hazardous chemicals and complicated processes present in mills?

Taking samples off-line to a lab is one method, but by the time the results are available the process may well have already changed dramatically. There are some instruments designed for monitoring specific elements of the manufacturing process, but they either require sample conditioning (such as filtering or cooling), they may struggle with suspended solids or are not compatible with fluctuating temperatures. All this changes with the introduction of the IRmadillo FTIR Spectrometer.

Keit’s IRmadillo has been specifically designed for harsh, unforgiving and caustic environments, and is ideally suited for monitoring pulp and paper manufacture. Its design is an innovation in process technology – installed directly in-line to manufacturing lines and vessels and with the ability to connect to your DCS, the IRmadillo provides continuous, in-depth chemical concentration information of your processes to enable real-time control and improved efficiency. Knowing what your process is doing without off-line sampling means maximizing your chemical recovery, saving energy and increasing the automation of your manufacturing processes.

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Pulp and Paper:
The Kraft Process, Paper Bleaching and the IRmadillo

The Kraft process is the dominant method of pulp manufacture globally, which consists of treating wood chips with steam, sodium sulfide (Na2S) and caustic soda (sodium hydroxide – NaOH). This produces pulp and a by-product known as black liquor a stream that contains a host of organic compounds (dissolved lignin, sugars and hemicellulose) and a wide range of inorganic compounds (NaOH, Na2CO3, Na2S and Na2SO4 being the highest concentration). This stream is concentrated and then burned in a recovery boiler to produce green liquor (primarily Na2CO3 and Na2S) and is then causticized converting the Na2CO3 to NaOH in the white liquor. But there are many other organic and inorganic chemicals present that can play a deleterious role in the process. More details are shown below.

Pulp&Paper - Kraft process schematic & Keits IRmadillo

The washed pulp can either be used directly to make board or packaging, or after bleaching can be used to make paper or tissue. Bleaching involves a range of chemicals such as NaOH, chlorine dioxide (ClO2) and hydrogen peroxide (H2O2). Lastly, the bleached pulp is mixed with chemical additives (for example cellulose derivatives or polymer additives) to achieve the desired properties in the finished product before rolling into paper. The waste white water from the paper making machine is recycled and topped up with additional chemical additives. An overview of the Kraft process is shown above, with recommended installation points for the IRmadillo.

The IRmadillo can easily monitor the following applications:

  • Reduction Efficiency
  • Residual Effective Alkali
  • Effective Alkali
  • Active Alkali
  • Tall Oil and Tall Soaps
  • Black Liquor Chemical Composition
  • Recausticizing Control
  • Wet Strength Additives
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Optimize your chemical recovery with real-time monitoring

The Kraft process relies on being able to efficiently recover the inorganic chemicals from the black liquor for reuse in the digester and this is done by converting first to green liquor and then to white liquor in the recovery circuit, also recovering energy in the process. Because of the wide variety of chemical reactions involved, this opens up multiple opportunities for the process to go wrong and quickly drift away from effective and efficient conditions. Understanding exactly what is happening inside the boiler and the causticizers is a key driver for cost savings and process improvement.

Chemicals are added during the paper manufacturing process to achieve the desired end product (for example, wet strength additives for tissue products). These can be expensive chemicals, and measuring their concentration in white water can ensure that the minimum amount of chemicals required are being used, dramatically reducing costs for the mill. The IRmadillo helps you optimize every stage in the process, improving efficiency and saving money.

What about other instruments – Raman, near infrared (NIR), & refractive index monitors?

Raman spectroscopy is similar to the FTIR that drives the IRmadillo’s process monitoring, but it can be very strongly and negatively affected by particles and bubbles in the solution, as well as showing strong fluorescence in many cases.

Near infrared (NIR) technologies provides much less specific information than FTIR – they’re very good in some industries, but not up to the demanding job of pulp and paper production monitoring.

Refractive index monitors are cost effective instruments for simple systems, but they cannot cope with complicated mixtures such as those present in pulp and paper production.

Raman, near infrared and refractive index monitors have been around for many years prior to the IRmadillo – put frankly, if they were the right tool wouldn’t you have one already?

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The IRmadillo for
Pulp and Paper Manufacturing

Scaling, or softer fouling, can occur in many stages of the Kraft process. In collaboration with some of the major pulp mill operators, Keit has developed a descaler system compatible with both flow cell and process line installation. We strongly recommend that this descaler is specified with any Kraft liquor install. In addition, it is possible for the IRmadillo to detect the formation of scale and thus trigger remedial action when required.

The IRmadillo was developed to install directly into your process, with no need for filters, sample conditioning systems or anything else. During installation scoping conversations, our engineers will discuss how best to seal the instrument into your process (such as an ANSI or DIN flange). If your process operates at a very high temperature then we may need to bring the temperature down to a manageable level.

The IRmadillo is based on FTIR technology meaning it continuously measures everything that’s present in the mixture – all the time, every time. For you, this means it can look for organic chemicals (such as cellulose and polymers), inorganic salts (such as sulfate) and the physical properties (such as effective alkali and total dissolved solids) all at the same time. It provides a reading every 2 minutes, giving you the tools you need to make changes in real time.

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