The retention agents group is very extensive.The paper machine retention systems are very important parts of overall PM chemicalization and a proper attention must be paid to their choice so that the required results are achieved.

The retention systems used in practice are:

• Single component
• Two component
• Three component

PAPCEL offers technological equipment for all the above mentioned systems. In practice, usually a polymer combination from the polyacrylamide (PAM) group is used, either a single one or in a two component system with bentonite, cationic starch or silica (silicon dioxide).

The substantial point is that the retention systems are able to work with both liquid PAM-based commercial agents and with powder ones. In both cases the needed stations are designed with regards to a maximum operation reliability so that the parameters on the equipment dosing side and above all on the powder solving side were always constant and without fluctuations to avoid subsequent PM operation troubles. Above all, the PAM solution preparation is designed as a fully automated process.

The powder products are exactly dosed by means of precise worm devices fluently controlled by means of frequency converters. Dissolving water is measured by means of inductive flowmeters. The stirring time, the a work concentration, level scanning in a work tank, the other parameters in a dissolving tank and the quantity of product in the hopper are either controlled by a sophisticated control system or the station is delivered without a control system and controlled by the PM control system. An integral part of the station delivery is also a logics description needed to compile software for an existing control system.

The precise worm dosing devices are able to cover usual PM capacities in the production range from 1 to 50 tph. The subsequent station parts are designed according to the retention agent offtake. Thus the station design can be very variable.

For lower PM capacities (up to approx. 10 to 15 tph), a compact solution is sufficient with all the components installed in a support frame and constituting a compact unit; otherwise, with respect to the necessary volumes, the dissolving and storage tanks stand outside the frame containing only the powder polymer dosage unit and dosing pumps incl. dilution circuits; alternatively, the station concept is conformed to the customer’s request with regards to the built-up conditions.

The bentonite preparation plant design presumes purchasing bentonite in “Big-Bag” type packs. Therefore, the station consists of a “Big-Bag” tower with a lifting device (or an existing crane is utilised), a hopper, a precise worm dosing device, a dispersing tank, a storage tank and necessary dosing screw (Mohno) pumps using the method of the ratio dilution down to the work concentration.

Pure filtrate or thin stock (drawn from the stock pipeline close before the paper machine headbox) is used for the dilution.Such solution is significant for high performance paper machines or generally wherever water consumption must be significantly reduced. The bentonite plant control system is designed similarly as the one in polymer plants. Thus, the equipment is delivered with a control system or an existing paper machine control system is utilised.

The machinery design and safety comply with the EU and EAC industrial standards.

Parameters

• PAM dosed quantity range 100 – 500 g/ton
• Outlet dose according to the paper machine output
• Stored solution concentration 0.3 %
• Work solution concentration 0.3 %
• Inlet concentration at dosing point 0.03 %

Main parts of the retention polymer preparation device

• Powder product hopper
• Powder product precise worm dosing device
• Pump dosing commercial liquid product into storage tank
• Storage tank with agitator and dilution water inlet
• Pumping stored solution over to work tank
• Diluted product work tank with agitator
• Diluted product dosing pump
• On-line dilution circuit with outlet distributor depending on dosing point number
• Measuring and control elements
• Electric switchboard with control system
• Device support frame