Can I handle-tie two 120V CH breakers for a 240V load?
It may not provide a legal breaker for a 30-A 240-V circuit such as for a dryer that uses 240 V and 120 V because the tie bar only works for manual shut-off. If one breaker trips due to over-current, it is not assured to pull off the other breaker unless that is an explicitly stated property of this model breaker.

I think the only use of tied 1-pole breakers is for powering circuits from two breakers with a shared neutral, an arrangement which I think is called a multi-wire branch circuit. But that would probably be with 20-A or 15-A breakers. I think you should return the extra 1-pole 30-A breakers.