Successful Start-up For New Soda Recovery Boiler At Skoghall Mill

Skoghall, Sweden — At 11:45 am on Wednesday, September 29, waste liquor was fed to the new soda recovery boiler at Skoghall Mill for the first time. As expected, the start-up of the new unit was a major success!

Months of intensive fine-tuning lie ahead, during which the emphasis will be on meeting energy and environmental parameters and ensuring the boiler performs its role as a chemical reactor to recover sulfate. When the fine-tuning stage has been completed, a series of warranty runs will be conducted to guarantee that the unit meets the demands contained in the mill's contracts with the various equipment suppliers.

Flying start
In our type of forest products company, with a kraft pulp plant, a CTMP plant and two large board machines in an integrated process, all of the various parts affect each other. We therefore assigned ourselves a tough task when we established our objectives, which were to start-up the new facilities with minimal disruption to the rest of the plant. We needed to make a flying transition from the old to the new, at the same time as pulp supply and the operations of KM7 and KM8 had to be maintained. Naturally, this required considerable coordination and planning over both the short and long term.

To date, however, we have been extremely successful! The start-up of evaporation operations in August was achieved without any problems and after just a day or so we could produce combustible liquor for our old soda recovery boiler. Simultaneously, we started up the gas-fired furnace for the incineration of malodorous gases. We have experienced minor start-up problems in this area, but these have now been resolved.

The old No 4 soda recovery boiler from 1969 was shut down the night before Thursday, September 29 and unit No 3 (from 1957) was shut down the night before Friday, September 30. This means that one of Europe's oldest soda recovery boilers was in operation for half a day in parallel with what is definitely the world's most modern soda recovery boiler!

Plants that remain to be started up include a digester house for tall oil, a by-product of the kraft pulp production process and a modified turbine (TG) for the generation of electricity.

Equipment checks
Start up was preceded by intensive program of equipment and materials checks in all areas, for example, pipes, insulation, mechanical parts, electricity, instrumentations and all control systems. This latter area in particular is an extensive task, especially bearing in mind today's computer-based and highly complex instrument systems. Small faults can easily become major problems unless discovered in time.

Many personnel from Skoghall Mill and all of the suppliers involved have devoted several months of very extensive effort to ensure that the start up was as successful as it now seems to have been.

Next stage
The second stage of Energy 2005 covers conversion of the oil-fired boiler to solid fuel, a solid-fuel plant and increased bio-based electricity production. The solid-fuel plant and the new solid-fuel-fired boiler will be commissioned in spring and summer 2006.

SOURCE: Stora Enso