The Infinite chemreactor is a quest reward item. It generates 75 chemfuel every 10 days as long as it is powered by 300W. When it is done producing chemfuel, it will drop a stack of 75 onto an empty adjacent tile.
It is a slow way of obtaining chemfuel, especially in the mid-game stage where you're most likely to get this item. It generates 7.5 chemfuel a day, compared to 35 for every batch made at a refinery or 6 per day extracted from a boomalope.
It generates more chemfuel per day than a single chemfuel powered generator consumes. The Infinite Chemreactor consumes 300W, while a single chemfuel powered generator produces 1000W, resulting in a generated power surplus of 700W and a chemfuel surplus of 3 per day. This makes the Infinite chemreactor a slow but sustainable tool for passively generating both free energy and chemfuel, if you can get your hands on one.
Eight infinite chemreactors can generate enough fuel to power 15 chemfuel powered generators, for a total generated power surplus of 12600W.
Given the description of how it works, the infinite chemfuel reactor may possibly be a late-midworld technology rather than glitterworld or even transcendent in origin like the other quest items.