Acrylonitrile reactor start-up procedure
A reactor, acrylonitrile technology, used in chemical instruments and methods, chemical/physical processes, hydrocarbon ammoxidation preparation, etc., can solve the problems of low concentration of combustible components, instability, unstable temperature and oxygen concentration, etc.
Active Publication Date: 2017-05-17
INEOS EURO LTD
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Problems solved by technology
[0013] However, the problem with this fuel limiting approach is that once the system reaches normal operating conditions, it prevents explosive mixtures in the effluent gas because the oxygen concentration in the gas is too low, not because the concentration of combustible components is too low
[0017] Yet another problem with this fuel-limited approach is that some of the products and by-products of the ammoxidation reaction (e.g., acrolein), although not explosive when present in sufficiently low concentrations, are encountered in the reactor effluent gas. It is still unstable at high temperature and oxygen concentration
This instability can lead to combustion reactions occurring in the effluent gas (known as "effluent afterburning"), which leads to undesirably high effluent temperatures
Method used
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[0032] Start-up of a commercial fluidized bed acrylonitrile reactor begins with the ammoxidation catalyst in a settled (non-fluidized) state resting on top of the reactor's air grid 14 . In one aspect a single reactor may be used, in another aspect more than one reactor may be used, in another aspect two reactors may be used. The reactor effluents can be combined at a later point in the process.
[0033] The first step of a typical reactor start-up procedure involves nitrogen purge of the feed sparger, ie, nitrogen is charged through the feed sparger at a flow rate sufficient to prevent fluidized ammoxidation catalyst from entering or clogging the sparger. Simultaneously or shortly thereafter, heated process air is fed to air inlet 22 at a flow rate sufficient to cause fluidization of the ammonia oxidation catalyst. This heating step continues until the temperature of the ammoxidation catalyst reaches or slightly exceeds its minimum ammoxidation reaction temperature, which ty...
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The formation of explosive mixtures during start-up of the acrylonitrile reactor is prevented by including ammonia in the gas charged into the reactor during catalyst preheating. In addition to generating heat, this oxidation of ammonia reduces the oxygen content of the gas inside the acrylonitrile reactor and in the reactor effluent gas, thereby reducing the risk that explosive mixtures will form in the effluent gas.
Description
technical field [0001] The present invention relates to acrylonitrile reactors, and in particular to preventing the formation of explosive mixtures during start-up of an acrylonitrile reactor. Background technique [0002] In the commercial manufacture of acrylonitrile, propylene, ammonia and oxygen react together according to the following reaction scheme: CH 2 =CH-CH 3 +NH 3 + 3 / 2 O 2 →CH 2 =CH-CN + 3H 2 o [0003] This process, commonly referred to as ammoxidation, is carried out in the gas phase at elevated temperature in the presence of a suitable fluidized bed ammoxidation catalyst. [0004] figure 1 A typical ammoxidation reactor for carrying out the process is shown. As shown here, the reactor 10 includes a reactor housing 12 , an air grid 14 , a feed sparger 16 , a cooling coil 18 and a cyclone 20 . During normal operation, process air is charged into reactor 10 via air inlet 22 while a mixture of propylene and ammonia is charged into reactor 10 via feed...
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IPC IPC(8): B01J8/24C07C255/08C07C253/26
CPCC07C253/26Y02P20/52C07C255/08
Inventor T.R.麦克唐奈J.R.库奇D.R.瓦纳P.T.瓦赫滕多夫
Owner INEOS EURO LTD