Centrifuged high ammonia

Centrifuged high ammonia (HA) latex concentrate is the most common technically specified latex concentrate available in the market. A bank of... 

Materials High ammonia type centrifuged natural rubber latex from Pasir Waringin Rubber Plantation. FTP XI, West Jawa, lndone.sia was used (Table 1). Carbon tetrachloride and normal butil acrylate were used as sensitizer. Nocract 300 was used as antioxidant. All the chemicals were technical grade without further purification. 

A number of preservative systems are in use (Table 1). Evaporated latex may be preserved by ammonia or potassium hydroxide. Centrifuged latex is always preserved by ammonia, either on its own as in high ammonia (HA) latex or at a lower level in combination with a secondary preservative as in grades of low ammonia (LA) latex. The LA grades are typified by the type of secondary preservative, of which... 

Centrifugal machines can be built for industrial use with ammonia and other refrigerants, and these mayhave up to seven compression stages. With the high tip speeds in use, it is not practical to build a small machine, and the smallest available centrifugal compressor for refrigeration dutyhas a capacityof some 260 kW. Semi-hermetic compressors are made up to 7000 kW and open drive machines up to 21 000 kW capacity. 

In this process, ammonia solution flows countercurrent to the ascending stream of CO2. Crystals of ammonium bicarbonate precipitate out when the solution becomes sufficiently saturated. The crystals are filtered or centrifuged out of the mother liquor, washed, and air-dried. Pure product may be obtained by using high purity CO2. Alternatively, high purity ammonium bicarbonate may be obtained by subliming the product formed at relatively low temperatures. 

Some unusual flow reactors are shown in Figure 17.14. The residence times in the units for high temperature pyrolysis to make acetylene and ethylene and for the oxidation of ammonia are measured in fractions of a second acetic anhydride is made by mixing reactants quickly in a centrifugal pump NO is formed at very high temperature in an electric furnace and ethylene is polymerized at high or low pressures in the two units shown. 

Field latex is bulked in large tanks at a factory adjacent to the rubber estate. If a high-solids latex is desired, the field latex is strained, stabilized with ammonia or other chemicals, such as soap and bactericide, and either centrifuged or creamed to 62-68% total solids,... 

The ammonia-formaldehyde reaction is highly exothermic. Therefore the reactor is operated under a vacuum so that the heat of reaction can be used to evaporate some of the water of reaction. This helps concentrate and crystallize the hexamine in the water solution. If dry solids are desired, the hexamine-water solution is pumped through a crystals receiver and then separated in a centrifuge. The crystals pass through a rotary dryer and are packaged for shipment. In some cases a liquid solution may be shipped to customers125. 

---