Crystallization spray

For applications where waste heat at very low temperature is available and where the product will not be contaminated by atmospheric 

---

Although spray-crystallized dextrose-maltose (EMDEX , J. Rettenmaier Sohne GmbH Co. KG, Germany) and compressible sugars are coprocessed, they are commonly considered as single components and are listed as such in the United States Pharmacopeia, while the third edition of the Handbook of Pharmaceutical Excipients has listed SMCC as a separate excipient (58). 

Alternatively, ammonium nitrate (AN, QCq2 = 20.0 %, begins decomposition at m.p. = 169.9 °C, complete decomposition at 210 °C) has been discussed, however this compound has severe burn rate issues. Furthermore, AN is hygroscopic and shows phase transitions from one polymorph to another at 125.2 °C, 84.2 °C, 32.3 °C and -16.9 °C. Phase stabilized ammonium nitrate (PSAN) and spray crystallized AN (SCAN) are special qualities provided by ICT. 

Dextrates comprises white spray-crystallized free-flowing porous spheres. It is odorless with a sweet taste (about half as sweet as sucrose). 

Dextrates is produced by controlled enzymatic hydrolysis of starch. The product is spray-crystallized, and may be dried to produce an anhydrous form. 

Phase Stabilized Ammonium Nitrate PSAN and Spray Crystallized Ammonium Nitrate SCAN are special qualities provided by ICT. 

The name prilling is given to a melt-spray crystallization process that results in the formation of solid spherical granules. It is employed widely in the manufacture of fertilizer chemicals such as ammonium nitrate, potassium nitrate, sodium nitrate and urea. 

The term spray crystallization is really a misnomer strictly speaking, individual crystals are not grown by this method - solid is simply deposited from a very concentrated solution by a technique similar to that used in spray drying. Size and shape of the solid particles depend to a large extent on those of the spray droplets. The spray method is often employed when difficulties are encountered in the conventional crystallization techniques, or if a product with better storage and handling properties can be produced. 

Anhydrous sodium sulphate can be manufactured by spray crystallization. Below 32.4 °C sodium sulphate crystallizes from solution in the form of the decahydrate above this temperature the anhydrous salt is formed. However, anhydrous sodium sulphate has an inverted temperature-solubility characteristic (see Figure 3.1b), and trouble is encountered with scale formation on the heat transfer surfaces of conventional evaporating crystallizers when operating temperatures in excess of 32.4 °C are used. In a plant described by Holland (1951) a concentrated solution of sodium sulphate was sprayed, or splashed, in the form of tiny droplets into a chamber through which hot gases flowed. The gases entered at about 900 °C. The continuously operated unit produced a powdered anhydrous product. 

The spray crystallization of a solution has some features in common with prilling, the melt crystallization technique described in section 8.2.2. 

It is obtained from almost complete acid hydrolysis of starch (- hydrolysis, glucosidic linkages), followed by desludging, decoloring, concentration and solidification. The latter is performed either by bulk crystallization and shredding or by spray crystallization. 

Industrial production is based on 50% solutions of D-glucose (dextrose). The yield of s. depends strictly on the purity of the sugar. Hydrogenation is performed continuously under high pressure on fixed-bed Cu-oxide or Ni-oxide catalysts. After refining, the reaction fluid is evaporated to 70% d.s. (main commercial product). S. powder may be prepared by (spray)crystallization of highest-purity s. 

---