Soldering station - sensor fault protection
There is sensor-open protection in the form of that 100K resistor. The current is unnecessarily high so you will get excessive error due to the resistance. All you have to do is overcome the leakage current of the capacitor at some tens of mV, so it could probably be 10M if you use a ceramic 10uF capacitor. Note that the bias current for this particular op-amp flows out of the inputs. I would use a 1uF or 10uF ceramic, move it to the non-inverting input and reduce the 10K to 1K ohms.  

You don't have protection against a short (eg. thermocouple shorted away from the junction, between the leads or to ground), but that's relatively difficult to do without a microcontroller or a second sensor. 

As far as the MOC3xxx goes, the zero crossing MOC3041 is not designed for 24V use, so it will reduce the maximum power somewhat. 

The op-amp has a typical drift in the 5uV/°C range, a large offset and the circuit has no cold-junction compensation so you'll get an unknown offset to begin with and the tip temperature will drift upward about 1:1 with the temperature at the connections 1 &amp; 2. In other words if those connections heat by 20°C your tip temperature might go from 340°C to 360°C.