Use of braiser for frying In our large commercial kitchen, which is seldom used, how long can we keep the oil in the large tilt braiser that is used for French fries and fried fish? 
Can this oil then be disposed of in the floor grease trap?
Uh...NO!

While running some 'minor spillage' down the floor trap is not a big deal washing a large amount of oil down the drain would be BAD. As the oil cools it will form a solid clog that would be very difficult (and probably expensive) to clear. 

(there is no information about where you are from, so this may or may not apply to you...)

[In the U.S.] 
Local fire departments will allow for the disposal of waste petroleum products (like this or motor oil). 
Most restaurants which do a serious amount of frying have oil disposal services that come by and collect used fryer oil.