Talk:Sulfite process

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Pictures of industrial sized Digestors to make Hardwood Sydney Australia
Link- Https://sydney-city.blogspot.com/2010/02/pyrmont-waterfront-park.html Article:- These three enormous rusted steel spheres have been installed in Waterfront Park, in the inner west suburb of Pyrmont. This area was once used by CSR Limited for a major sugar mill, sugar refinery and associated industries. Over the years, the company diversified operations into rum distillery, building products and eventually mining. This park is located on the site of the former CSR factory which was used for the production and storage of Caneite fibre board, a by-product from the crushing of sugar cane and Hardboard, made from eucalypt and other hardwood chips. These spheres were Digesters used to produce Hardboard. The wood chips were expanded using high pressure steam, releasing the natural lignins in the wood that turned them into fibre that were pressed into boards for use as building material. The spheres were salvaged from the factory before demolition and used as historical interpretive elements in the park. SMGinOZ (talk) 03:37, 19 March 2023 (UTC)

Comment from above article

I was the last Production Manager at the Cane-ite factory. The spheres were DIGESTERS used for making HARDBOARD, and were not used for Cane-ite or Sugar refining. Cane-ite production (wet-process low density fibre-board originally made from Cane bagasse then from Pine wood chips) ceased in 1991, and did not require Digesters, being made from mainly wood pulp (made from the chips) and water (in a process very much like paper manufacture).

However, originally the factory made both Hardboard (like Masonite or Hardiplank material – is a wet-process High density fibreboard made from eucalypt and other hardwood chips) and Cane-ite. These were made on different levels of the factory. From memory the Cane-ite was made on level 2 and the Hardboard on level 1, with the vats of “stock” (the wood pulp/water mixture) and white water (the waste water squeezed from the Cane-ite and hardboard) on the ground floor.

The Hardboard production stopped back in the 1950’s or 60’s, well before my time (or even before I was born). Hardboard doesn’t actually have any added glues – it uses the natural lignins that are in the wood, by processing a wet mulch (“mat”) of the wood fibre under very high pressure and temperature (the process is unchanged to this day – eg up at the Masonite plant at Raymond Terrace). The role of the Spherical Digesters was crucial in releasing the lignins from the hardwood chips and in converting the chips to fibre (Most “modern” hardboard technology doesn’t use this system any more, however – see below).

Chips were put into the Digesters, they were filled up with high pressure steam (hence the need for them to be spherical ie very strong pressure vessels) and then, suddenly, the pressure was released. This caused a massive and rapid expansion of the chips which pretty much “blew them up”, turning them into fibre and releasing the lignin into suspension in the water (that water had condensed come from the steam).

You can tell the spheres are very old by the fact they are riveted, not welded. I think this makes them from the 1940’s or even earlier. These days, I think hardboard is made using pressurized refiners (not digesters), which mechanically grind up the wood-chips to fibre under pressure. — Preceding unsigned comment added by SMGinOZ (talk • contribs) 04:02, 19 March 2023 (UTC)