Each dangerous goods class is represented by a placard - a distinctive and specific class label in the shape of a diamond. For example:

White liquor is produced in slaker where sodium carbonate (Na2CO3) reacts with reburned lime (CaO) forming white liquor (NaOH) and calcium carbonate CaCO3, which is separated in lime mud washers and burned in lime kiln back to CaO.

In the slaker feed – the second control is placed inline for active slaker control, ensuring that the green liquor for slaking has a consistent TTA. The real-time density/TTA measurement is in the slaker feed and then a control loop ensures the automatic and quick trimming of green liquor to counter disturbances. This increases causticizing efficiency while also avoiding overliming, improving the quality of white liquor and lime mud. It also ensures the safe operation of the slaker.

Green liquorname

Density measurement technologies, on the other hand, raise several challenges, including continuous scaling, drifting and measurement insensitivity, unreliable control requiring manual input, and an unstable process that leads to efficiency and production losses.

In the dissolving tank – inline measurement of density/TTA in the dissolving tank helps to maintain the target value of the green liquor and avoid deviations. This is a hugely important control for the stability of the entire line – sometimes said to be the point at which pulp making really starts. Measurements in the transfer lines are paired with a control loop to the weak wash liquor, giving automatic control based on density/TTA. The measurement device reads target values, avoids deviations, and is completely automatic, enabling stable TTA levels and safe operation of the dissolving tank.

Dangerous goods are substances and articles that have explosive, flammable, toxic, infectious or corrosive properties. They pose a risk to public safety, property or the environment.

Green liquorBrands

Effective causticizing control improves the quality and stability of white liquor, decreases operating costs, and increases pulping efficiency. Effective lime dosage control reduces the recirculation flow of lime in the process, leading to less lime reburning in the lime kiln and decreased energy consumption. Real-time, accurate, and reliable inline measurement with a process refractometer is the easiest way to achieve these goals.

Green liquorBottle

The Vaisala Polaris™ PR53SD Process Refractometer can be used to measure the density or TTA concentration of green liquor at both stages where control is needed: after the green liquor dissolving tank, and after the green liquor clarifier at the slaker feed.

The refractometer’s sensor is mounted directly in the pipelines for inline measurement, allowing real-time and active control to achieve the target TTA. The digital measurement is unaffected by bubbles, suspended particles, or color changes to the green liquor. The refractometer provides highly accurate measurement with no drift, and with an additional prism wash system it also supports scaling conditions.

Some dangerous goods fall into one of 3 packing groups depending on the degree of danger they present to people and equipment:

Class 4: Flammable solids; substances liable to spontaneous combustion; substances which, on contact with water, emit flammable gases

In the causticizing process, passive chemicals are converted into active cooking chemicals to make white liquor. This is used in the digester as a cooking chemical and needs to be of a high and consistent quality to maximize mill productivity. Accurate and continuous measurement of green liquor density or total titratable alkali (TTA) is essential to ensure this high quality is maintained.

Green liquorabsinthe

Dangerous goods substances and articles are allocated to one of 9 classes. Some of these classes are subdivided into divisions:

The Australian Dangerous Goods Code provides more information about the classifications and divisions of dangerous goods, and if they are assigned to a packing group.

Keijo Pyörälä has been working at Vaisala (K-Patents) Liquid Measurements for over 25 years in different positions from Product Management to Regional Sales Management and Global Business Development. Keijo has a Master’s Degree in Chemical Engineering from Lappeenranta University of Technology and an Executive Management Degree from Aalto University. He has been involved in a number of global product and business development projects in different industry segments from food & beverages, pulp & paper, sugar & sweeteners to chemical & polymer and oil & gas all over the world. His specialty is process optimization with in-line process measurements, process efficiency, and energy savings as well as quality improvement projects.

There are several different methods to measure and control green liquor density/TTA in the causticizing process, but the most effective are inline, real time, and can be used for automatic control. Process refractometers offer several important several benefits:

We pay our respects to the Aboriginal and Torres Strait Islander ancestors of this land, their spirits and their legacy. The foundations laid by these ancestors—our First Nations peoples—give strength, inspiration and courage to current and future generations towards creating a better Queensland.

Green liquorpregnancy

The process starts when the smelt from the recovery boiler is dissolved in weak wash in the dissolving tank to produce green liquor. The raw green liquor, which consists mostly of sodium carbonate and sodium sulfide, is then pumped into a stabilization tank to even out fluctuations in density and temperature, and to ensure a more constant liquor composition to the causticizing process.

Green liquor density or TTA must be measured accurately to achieve high-quality white liquor. Real-time measurement and control of density/TTA during the causticizing process has several notable benefits:

Depending on its properties, each type of dangerous goods is assigned a number known as its UN number*; for example, petrol is UN 1203. The UN number can be found on the label, transport document or safety data sheet. Otherwise the manufacturer or supplier of the goods can tell you this. You can also check if the goods are listed in the Australian Dangerous Goods Code.

Contact an interstate competent authority for information on dangerous goods regulations, licensing and classifications outside of Queensland.

The clarifier aims to obtain a well-clarified green liquor for the slaker. It also reduces dregs carryover, which causes problems in downstream equipment. In the slaker, the clarified green liquor is brought into contact with reburned lime. This slaking reaction converts the green liquor into white liquor by converting sodium carbonate into sodium hydroxide, an active pulping chemical. Impurities, known as grits, are also separated at this stage.

*The United Nations number (UN number) is a 4-digit numbering system developed by the United Nations Committee of Experts on the Transport of Dangerous Goods for the quick identification of dangerous goods.