THE DIFFUSION PEOCESS. 



Comparison between Milling and Diffusion. The diffusion 

 process as applied to the cane sugar industry first came into prominence about 

 1884, and since that date it has received extended trials ; amongst the plants 

 that have been erected may be cited those at Non Pareil in Demerara, at 

 Britannia in Mauritius, at Makaweli and Kealia in the Hawaiian Islands, and 

 at Wonopringo in Java ; these factories, all of which were worked under 

 expert supervision, have nevertheless reverted to milling, and the same is true 

 of the majority of diffusion plants that have been erected. However, 

 diffusion cannot be considered as dead, as several of the older plants remain in 

 successful operation, and a few others have been erected in recent years. The 

 causes that contributed to the non-success of the earlier diffusion plants were : 



1. Faulty design on the part of the engineering firms responsible for the 

 machinery ; this was especially pronounced in connection with the cane 

 cutting machinery. 



2. Difficulty in maintaining a constant supply of cane for day and night 

 work. In a diffusion process, it is essential that the work be continuous ; 

 with milling this is not the case as the process of extraction is limited to the 

 very small amount of material actually being crushed at any moment ; it is 

 this point, as much as any other, that tells against the diffusion process, as it 

 is often impossible to maintain a continuous supply of cane ; in the beet sugar 

 industry the raw material is stored in silos without deterioration, thus affording 

 a continuous supply, but such a process is not possible with the cane. 



3. Greater elasticity of the milling process. The amount of cane treated 

 in mills can be varied within wide limits without affecting the efficiency of the 

 work, and with poor canes the economic limits of exhaustion can be controlled 

 more reauily than is the case in a diffusion process. 



4. Excessive fuel consumption. In Demerara, a consumption of a ton of 

 coal to a ton of sugar was common with the diffusion process ; when it is 

 recalled that at the present time there are beet factories working with a coal 

 consumption of only seven per cent, on the weight of the beets, equal to half a 

 ton of coal per ton of sugar, it is at once apparent that this enormous 

 consumption was due, not to faults inherent in the diffusion process, but 

 rather to the design of particular factories. 



In ' Sugar and the Sugar Cane ' (1904) the writer quoted 93'5 per cent, 

 extraction as the highest figure recorded for mill work with a dilution of 

 21-65 per cent, on a normal juice. At the present moment (1909) in Hawaii 

 there are quadruple crushing plants at work, obtaining an extraction averaging 

 95 per cent, without fuel consumption other than that afforded by the megass. 

 The best work claimed for diffusion is an extraction of 96 per cent, to 98 per 

 cent, but in no case is this obtained without a considerable consumption of 

 extra fuel, and with a dilution higher than that found in milling processes. 



Mixed Extraction Processes. Below are given brief descriptions 

 of combined milling and diffusion processes that have attracted attention. 



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