How to control proportional valve (pvq13-5l-03-m5-a) with arduino
I think if you use the circuit in my answer here it will work for you.
Replace R1 with 2.7 ohms and replace the S8050 with a TIP122 with a small heatsink.
Of course the 3.7V becomes 12V and the 68 ohms represents your valve. Put a diode across the valve, such as 1N4148.