all the methods known hitherto for

all the methods known hitherto for the production of sall melts work batchwise. a batch procedure has some severe disadvasntages compared with a ontinuous production method.in the case of a batch change,the apparatus has to be opened.the product may then be contaminated by the oxygen form the ambient air,water and dust.the batch change results in down times of the plant and thus in a reduced space-time yield.for an effective discontinuous method, large apparatuses have to be used.the start-up process requires correspondingly more energy and time.it has been found that impurities are entrained into the process,in particular during start-up of plants.