The HELP pre-steaming system is designed for use in the following applications:
- Chemical pulping (Continuous cooking)
- Mechanical pulping (CTMP/TMP/NSSC)
- Sawdust digester (M&D digester)
- MDF production
- Pellet production
An ANDRITZ HELP discharger is used in chip pre-steaming systems and bulk material storage bins.
The HELP pre-steaming system consists of a storage and pre-steaming bin with discharger that delivers an accurate and stable chip flow regardless of the process. Uniform moisture content and air removal prepare the chips for the next process step.
The HELP storage bin can store and discharge bulk materials with varying mixtures and densities, such as chips, fines, pulp, sawdust, pin chips, and knots. It is not suitable for bark, sludge, dust, or coal. The bin is round with a circular stoker discharger on a flat bottom. The stoker is driven by hydraulic cylinders allowing an 80° sweep for each of the stoker arms. The reciprocating action of the discharger covers the entire bottom of the bin, ensuring uniform plug flow.
The discharger feeds the material to a variable pitch discharge screw that meters the material to the process. If the material contains a significant amount of liquid (e.g. black liquor in a knot bin), the trough for the discharge screw can be equipped with screen plates to remove excess liquid. Multiple metering screws can be installed under the bin to allow material to be fed to several discharge points.
Optional steaming zones allow chips to be heated with steam at atmospheric pressure to raise the temperature of the chips and promote air removal. This improves liquor penetration of the chips during the cooking process. Pre-steaming also reduces variations in temperature and the moisture profile of incoming chips, permitting easier control of the pulping process throughout seasonal variations.