Correct circuit breakers for 4-wire connected Maytag dryer?
Service panels have two poles of 120V each.  Most loads you are familiar with, draw from one pole and return the same current to neutral, which is "in the middle".  240V loads draw 30A from one pole, and return 30A to the other pole. 

Generally there are 3 possibilities here. 


A 2-pole breaker, which is a double-wide breaker with a factory handle tie.  This has both common trip and common maintenance shutoff.  Both are mandatory for a single 120/240V appliance wired with a neutral, such as a dryer or range. 


One thing about 2-pole breakers is that the "common trip" is actually an internal mechanism inside the breaker, it isn't the handle tie.  


Two 1-pole breakers with a handle-tie, which is a UL-listed device that is field-installed.  This has common maintenance shutoff only.  This is acceptable for 240V-only (no neutral) appliances like water heaters and air conditioning units.  It is also required for multi-wire branch circuits, but a 30A MWBC would be excessively rare unless you had two travel trailers. 
Two individual breakers with no tie.  These are only good at 30A for plain 120V circuits, such as ... um... gosh... small travel trailers that use a TT30 connection, and that's about all I can think of that uses single 30A.  However, two 30A breakers can be handle-tied for use on plain-240V loads as mentioned above. 


I have seen panels where a handle-tie was conspicuously missing, and then I look closer at the dust in the bottom of the panel, and there it is.  It had fallen off while someone was moving breakers around.   So check the bottom of your panel. 

I accidentally bought a bunch of 30A 1-pole breakers.  That's why I know so much about what they can and cannot do.