1975 and beyond (continued)

APPM had initially considered soda-oxygen pulping for its pulp mill expansion, but with the discovery of the benefits of soda-anthraquinone pulping decided to use this process instead, applying it successfully to mixed radiata pine and eucalypt chips in a continuous countercurrent digester. This enabled APPM to replace imported long fibre chemical pulp on a one for one basis over the full range of its printing and writing papers without deterioration in machine runnability or paper quality -and without the need to instal major new plant.[101] SCI introduced NSSC pine pulping on a small scale in 1973 and later also found it could upgrade this process in terms of both pulp quality and pulping rate by the addition of anthraquinone.

Although it had been pulping radiata pine by the kraft process since the early 1940s, APM still relied heavily on imports, mainly from New Zealand, for most of its long fibre pulp needs. With its extensive Victorian plantations starting to reach maturity, however, it added to its Maryvale operations in late 1983 a large new pine kraft pulp mill with a capacity of 140 000 tonne/yr. The heart of the mill is a state-of-the-art two-vessel vapour phase continuous digester system developed in Sweden and the mill design has emphasized emission avoidance and integrated computer control.[102]

12 AMP's pulp and paper mill at Maryvale, Victoria, in 1985 -Australia's largest. About half of its wood supply is radiata pine, mainly from its own plantations.

The pulp and paper industry has always been conscious of its environmental responsibilities and recycling of water, chemicals, fibre and paper and the recovery of energy from spent pulping liquor and other wastes have long been part of the technology. On the other hand the extent to which these practices have been economically feasible has depended on scale. As a result, not all these practices were carried out in the smaller mills operating in the earlier years of the industry to the extent which today is regarded as acceptable. This situation has progressively changed as the mills have become larger and, since the early 1970s, tighter environmental controls imposed by governments.

Overseas improvements in chemical recovery technology have now enabled large mills using sulphur-based pulping processes to meet quite stringent limits for gaseous sulphur emissions. One such improvement -black liquor oxidation -was introduced by APM at Maryvale in 1976 and in 1983 a new low-odour recovery furnace was in stalled as part of its pulp mill expansion. In the case of smaller mills using sulphur-based pulping processes it is generally not economical to install chemical recovery systems and so the gaseous emission problem is converted into one of disposing of a liquid effluent with a high sodium and sulphur content. Where the small mill was located close to the sea, such as APM's Port Huon, Tas., NSSC mill or KCA's Apcel sodium bisulphite mill, this did not present a major problem. With SCI's Brooklyn NSSC mill near Melbourne, however, it was necessary to use a combination of municipal sewer disposal and chemical recovery based on a novel overseas NSSC chemical recovery process (Sonoco process) installed in 1976.[103]

Australian Academy of Technological Sciences and Engineering