Dow Chemicals takes microwaves from the kitchen to the chlorinators
15 Jan 2000
Microwave ovens may be the best thing since sliced bread in the kitchen - especially for hurried devotees of jacket potatoes and frozen pizzas - but their use in the chemical industry has been somewhat more limited. Dow Chemical, working with Californian firm Communications and Power Industries, has now developed a new use for microwaves within its petrochemicals division.
Dow has installed microwave emitters, made by CPI, in two brick-lined chlorination reactors at its complex in Freeport, Texas. Exactly as in kitchens around the world, the microwaves function as an oven, heating the bricks while the reactor is starting up or shutting down. This, the company explains, is a clean technology, improving the plant's environmental performance.
Because the reaction taking place inside the reactor requires energy, the system only works when the reactor walls are hot. Under steady-state conditions, the reaction itself supplies this heat, but during start-up, extra heating is needed. Previously, this was done using heated nitrogen and by burning methane in chlorine, but Dow decided that this was both environmentally unacceptable and too expensive, as it required a scrubbing unit to remove volatile organics from the hot nitrogen.
The microwave emitters, by contrast, supply `clean' energy with no emissions. Producing 60kW of power at 2.45GHz, the units heat the bricks up much faster than the previous method and give a very uniform heat distribution, which in turn gives a much purer product. Moreover, the microwaves can keep the reactors hot during down-time, so they can be restarted faster. This, in turn, means that the temperature inside the reactor can be kept largely constant, and the elimination of the heat-up-cool-down cycle means that maintenance downtime is reduced. `Overall, throughput and yield are significantly improved,' says Dow.
Not just for pizzas: microwaves heat Dow Chemical's reactors
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