  After in quiescence for 49 years, 4U~1730--22 became active and had two
outbursts in 2021 \& 2022; ten thermonuclear X-ray bursts were detected with
Insight-HXMT. Among them, the faintest burst showed a double-peaked profile,
placing the source as the 5th accreting neutron star (NS) exhibiting
double/triple-peaked type-I X-ray bursts; the other bursts showed photospheric
radius expansion (PRE). The properties of double-peaked non-PRE burst indicate
that it could be related to a stalled burning front. For the five bright PRE
bursts, apart from the emission from the neutron star (NS) surface, we find the
residuals both in the soft ($<$3 keV) and hard ($>$10 keV) X-ray band.
Time-resolved spectroscopy reveals that the excess can be attributed to an
enhanced pre-burst/persistent emission or the Comptonization of the burst
emission by the corona/boundary-layer. We find, the burst emission shows a rise
until the photosphere touches down to the NS surface rather than the
theoretical predicted constant Eddington luminosity.
  The shortage of the burst emission in the early rising phase is beyond the
occlusion by the disk. We speculate that the findings above correspond to that
the obscured part (not only the lower part) of the NS surface is exposed to the
line of sight due to the evaporation of the obscured material by the burst
emission, or the burst emission is anisotropic ($\xi>1$) in the burst early
phase. In addition, based on the average flux of PRE bursts at their touch-down
time, we derive a distance estimation as 10.4 kpc.
