Juice purification and juice evaporation in sugar production

In juice purification a lime kiln is used to decompose limestone, making lime and carbon dioxide, which are added sequentially to the raw juice to bind and precipitate out the non-sugar impurities. The resulting liquid is a clear, thin juice with a sugar content of about sixteen percent. The next stage is a filter thickener, where the sugar juice is separated from the carbonisation lime. The resulting liquid separated off is a clear, thin juice with a sugar content of about sixteen percent. The "Carbokalk" (carbolination lime) separated and rejected by the filter thickener, is a valuable by-product, as it is an excellent fertiliser. After this purification, the clear juice goes through several stages of vacuum evaporation to remove most of the water, and concentrate the sugar. In this process, multiple vacuum-boiling cells are arranged in series, with each succeeding cell having a higher vacuum. The vapours from one cell can thus boil the juice in the next one, a method called multiple-effect evaporation. The result is a thick golden brown juice with a sugar content increased to about sixtyseven percent.

Precise lime milk dosing is achieved using an OPTIFLUX 4300 which is particularly suited to measuring flow in difficult slurry applications. The flow and consumption of both carbon dioxide gas and steam is controlled using the OPTISWIRL 4200 vortex flowmeter. By monitoring the steam flow, pressure and temperature the OPTISWIRL flowmeter can also monitor the amount of net heat which is used in these stages. The differential pressure transmitter OPTIBAR DP 7060 is used to measure the pressure drop across the filters to manage their operation and efficiency.