I/O Module with optocouplers
The current through the relay coil is determined by the voltage across it, and the resistance of the coil. To turn the coil on, you'll need at least 33.3mA to actuate the coil. 

The voltage drop across the transistor is ~0.7V, the resistance of the coil is 360Ω
Assuming the transistor is fully on, there will be 64mA of current through the coil and 1.5W of power. To really know what the circuit is doing, the transistor part number is needed. 

1.5W of power is probably too much (there isn't any rating's on max power, but they recommend 400mW, so it would be best to limit the current to 33mA with a resistor in series or to use the appropriate relay. You should be using the ALQ124 with a 24V input.