Väriainetiivistys

Väriainetiivistys refers to a process in the pulp and paper industry aimed at recovering valuable chemicals and heat from spent pulping liquors, particularly from chemical pulping processes like the kraft process. The primary goal is to increase the concentration of the dissolved solids in the black liquor before it is sent to the recovery boiler. This concentration step is crucial for efficient energy recovery and chemical recycling.

The black liquor, a byproduct of wood pulping, contains lignin, inorganic chemicals (such as sodium sulfate and sodium hydroxide), and other organic compounds. Evaporating water from this liquor increases its solids content. Typically, multi-effect evaporators are used in series, where the vapor from one effect is used to heat the next, leading to significant energy savings. Advanced evaporation technologies, such as mechanical vapor recompression (MVR) and thermal vapor recompression (TVR), further enhance energy efficiency by recycling and reusing the generated vapor.

The concentrated black liquor, often referred to as strong black liquor, has a higher heating value and lower water content, making the subsequent combustion in the recovery boiler more efficient. This improved efficiency leads to greater steam production for the mill's energy needs and more effective recovery of inorganic pulping chemicals. Proper väriainetiivistys is therefore a cornerstone of sustainable and economically viable pulp production, reducing both chemical consumption and environmental impact.