Mass transfer is often the rate limiting step in gas-liquid reactions, and novel reactor designs that increase mass transfer can reduce reactor size and also improve process yields. As an example (Koestler 1992), an organic material was originally chlorinated in a glass-lined batch stirred tank reactor, with chlorine fed through a dip pipe. | . INTENSIFICATION 13 REACTOR STORAGE TANK SEVERAL THOUSAND GALLONS Figure 2-3. A tubular reactor to manufacture the product of Figure 2-2. Figure 2-2. A large batch reactor to manufacture a product elements to replace the batch process. The new reactor was so much smaller that when a group of people who had seen the original plant toured the new manufacturing facility they looked for a large reactor and finally mistook the final product storage tank for the reactor. Paul 1988 emphasizes the importance of a thorough study of the chemical reaction mechanisms and kinetics in several examples from the pharmaceutical industry allowing the process designers to identify optimal reactor configurations using novel designs including tubular reactors with static mixing elements. Gas-Uquid Reactions Mass transfer is often the rate limiting step in gas-liquid reactions and novel reactor designs that increase mass transfer can reduce reactor size and also improve process yields. As an example Koestler 1992 an organic material was originally chlorinated in a glass-lined batch stirred tank reactor with chlorine fed through a dip pipe. Replacement of the stirred tank reactor with a loop reactor with chlorine fed to the recirculating liquid stream through an eductor reduced reactor size increased productivity and reduced chlorine usage as summarized in Table 2-3. 14 2. INHERENTLY SAFER PLANTS Table 2-3 Effect of Reactor Design on Size and Productivity for a Gas-Liquid Reaction Reactor Type Batch Stirred Tank Reactor Loop Reactor Reactor Size liters 8000 2500 Chlorination lime hr 16 4 Productivity kg hr 370 530 Chlorine Usage kg 100 kg product 33 22 Caustic Usage in Vent Scrubber 31 5 a Koes tier 1992 Some Additional Examples of Intensification Nitroglycerine formerly was manufactured in batch reactors containing more than one ton of material. Newer CSTR processes significantly reduce the inventory and the Nobel AB process uses a mixing eductor reactor to reduce .
