there are various problems with that design:
- there is no need for a pre-regulator (L7815cp) as opamp plus power device are enough to provide both current and voltage regulation
- the filter capacitor (C1) may be too small while the output capacitor is too large (C4)
BTW you should provide some information about the transformer: (no load output voltage and rated VA) and required feature (min-max V and I) to get helpful advice
- a switching mosfet is unsuitable as pass device both because it is not specified for linear operation and because, as source follower, it would require a gate voltage around 4-5V higher than the maximum output voltage.
Besides that LM324 is not a rail-to-rail output opamp, so with 15V input voltage (opamp supply and drain voltage) at 1A load and taking into account the drop through R2||R4 you would hardly get more than 7-8V of maximum output voltage.
You should take care of opamp max supply voltage, min-max input range, min-max output capability at various load, proper transformer derating, power device SOA, feedback compensation, etc...
TIP31C might be ok, but you should drive it through another BJT like BD135 or similar. IMHO you should take inspiration from
this Jaycee's design (read the whole thread).