Trusted gateway connections allow for system growth, efficiency and consistent maintenance at Swedish paper mill.
by Matthias Borutta, Phoenix Contact
August 1, 2014

Paper production requires large amounts of power. The Smurfit Kappa plant in Piteå, Sweden, uses its own biomass boilers to meet part of its energy needs. The cleaning system in place for the high-performance steam generator includes a specialized motor management solution to ensure uninterrupted motor operation.

At the Smurfit Kappa Kraftliner Piteå paper plant in northeast Sweden, 520 employees produce about 700,000 metric tons of Kraftliner paper per year. Kraftliner is a special type of raw paper made of fresh fibers and serves as the base material for manufacturing high-quality corrugated cardboard packaging. The Swedish plant’s annual power consumption is about 520,000 megawatt hours (MWh). Biomass boilers—which burn organic material such as wood— generate 58 percent of that power, creating added value through efficiency and sustainability.

The Piteå production site consists of a pulp mill with two soft-pulp digesters and one hardwood digester and a paper mill with two paper machines. Two boilers produce the energy needed for the mill. One recovery boiler combusts the black liqueur from the process, and a biomass boiler uses mostly the bark from the wood-handling system. The steam from the boiler passes across two steam turbines that generate more than half the electricity required by the mill. This self-produced electricity is a green option because fossil fuel is only required during the startup process.

Lower Costs for Cleaning Routines

Smurfit Kappa Kraftliner Piteå in northeast SwedenSmurfit Kappa Kraftliner Piteå in northeast Sweden is one of the Smurfit Kappa group’s 350 production sites. (Article images and graphics courtesy of Phoenix Contact.)

A special steam cleansing technology boosts the efficiency of the power generation system. A high-performance boiler must be kept clean, ensuring high-efficiency degrees, high availability and minimal ash corrosion. Pressurized steam dissipates the soot, increasing the efficiency compared with conventional methods.

The cleansing technology also permits cheap, aggressive fuels for natural, efficient powering. The boilers are cleaned with automatic motorized 8-meter-long cleaning lances that spray pressurized steam onto the boilers’ heat surfaces. A specialized motor management program controls and monitors the motors during this cleansing process.

Efficiency & Maintenance Challenges

The previous electrical drives in Smurfit Kappa’s high-performance boiler were complex and difficult to use. The system required mechanical contactors for reversing the rotational direction of the steam cleansing system’s motors and digital outputs for clockwise and counterclockwise control.

Analog inputs handled the power input, and digital inputs analyzed the return signals. Wire connected all the devices and individual switching cabinets.

Documentation and controller programming were time-consuming with the existing system. Adding drives to the setup was a major undertaking that required expert project management.

Piteå siteThe Piteå site produces about 700,000 metric tons of Kraftliner paper per year.

In addition, the switching cabinets left little room for new additions. Consistent maintenance was not effective because of multiple components—such as drives, input/output (I/O) modules, measuring sensors, terminal blocks and contactors.

The existing system’s drives were three-phase asynchronous motors. A screw conveyor moved the lance in and out of the boiler to blow the soot off surfaces.

Each screw conveyor was fitted with two mechanical or inductive limit switches. When the screw conveyor reached the end or start position, the rotational direction had to reverse.

The limit switches were prone to dirt build-up, which made their signal information for reversing the rotational direction less reliable. Inadequate cleaning could, in a worst-case scenario, damage or destroy the motor. 3.

Fewer Wires, More Space

The new motor management system provided several advantages to the steam cleansing system. The program, which included motor management, hybrid motor starters and a fieldbus gateway, detected worn sootblowers before failure.

Fewer I/O modules were required, reducing wiring and documentation, and the compact device dimensions opened more installation space.

Bus gateways allowed for system expansion during system operation. The gateway forwarded the process data from multiple motor management modules to the control unit, while electronic motor management units (EMMs) handled monitoring and drive protection with active power monitoring.

The solution also included hybrid motor starters, which provided non-wearing motor switching. Relays and the system cabling solution quickly and reliably coupled the field devices to the controller.

Motor management unit’s compact dimensionsThe motor management unit’s compact dimensions save considerable space compared with similar components.

No Need for More Sensors

The 22.5-millimeter electronic motor management unit has built-in current transformers to directly read input currents up to 16 amperes.

If the applications’ output is higher currents, other EMM modules read them in combination with external current transformers. The range of available components works for all power ratings.