Удалить NAN и создать поле значения в виде строки?

Используйте Series.bfill для заполнения пропущенных значений для групп совокупной пользовательской лямбда-функции с помощью join и удаления пропущенных значений:

out = (df.groupby(df.pop('Business Name').bfill())
         .agg(lambda x: ' '.join(x.dropna()))
         .reset_index())
print (out)
        Business Name Case Number                                          Violation                                      Regulation(s)  Payments Unnamed: 6
0    CHI OPERATING CO    CP17‐085  Business knowingly or willfully sales months J...  30 CFR 1241.60(b)(1) 30 CFR  Part 1218,Subpart...  $142,310           
1  CROWHEARTENERGYLLC    CP19‐050  Business failed to report production Reports(F...        30 CFR Part 1210, Subpart C 30CFR1241.50‐52    $5,544   

Решение следует изменить, если необходимо объединить каждое непропущенное значение отдельно (строки 3,4 и строки 5,6):

print (df)
        Business Name Case Number                                Violation                   Regulation(s)  Payments 
        
0                 NaN         NaN                                      NaN    30 CFR 1241.60(b)(1) 30 CFR        NaN 
1                 NaN         NaN          Business knowingly or willfully  Part 1218,Subparts B, D, E and       NaN
2    CHI OPERATING CO    CP17‐085                sales months January 2011               30 CFR 1241.50‐52  $142,310
3                 NaN         NaN     Business failed to report production     30 CFR Part 1210, Subpart C       NaN         
4  CROWHEARTENERGYLLC    CP19‐050  Reports(Forms ONRR‐4054)for22production                 30CFR1241.50‐52    $5,544
5                 NaN         NaN     Business failed to report production     30 CFR Part 1210, Subpart C       NaN 
6  CROWHEARTENERGYLLC    CP19‐050  Reports(Forms ONRR‐4054)for22production                 30CFR1241.50‐52    $5,544

out = (df.groupby(df['Business Name'].notna().iloc[::-1].cumsum().iloc[::-1], sort=False)
          .agg(lambda x: ' '.join(x.dropna()))
          .reset_index(drop=True))

print (out)
        Business Name Case Number                                          Violation                                      Regulation(s)  Payments Unnamed: 6
0    CHI OPERATING CO    CP17‐085  Business knowingly or willfully sales months J...  30 CFR 1241.60(b)(1) 30 CFR  Part 1218,Subpart...  $142,310           
1  CROWHEARTENERGYLLC    CP19‐050  Business failed to report production Reports(F...        30 CFR Part 1210, Subpart C 30CFR1241.50‐52    $5,544           
2  CROWHEARTENERGYLLC    CP19‐050  Business failed to report production Reports(F...        30 CFR Part 1210, Subpart C 30CFR1241.50‐52    $5,544    

Если в реальных данных используются комбинированные строки и числовые столбцы, можно использовать:

print (df)
        Business Name Case Number                                Violation                   Regulation(s)  Payments  col
                                                                                                                         
0                 NaN         NaN                                      NaN    30 CFR 1241.60(b)(1) 30 CFR        NaN    4
1                 NaN         NaN          Business knowingly or willfully  Part 1218,Subparts B, D, E and       NaN    1
2    CHI OPERATING CO    CP17‐085                sales months January 2011               30 CFR 1241.50‐52  $142,310    0
3                 NaN         NaN     Business failed to report production     30 CFR Part 1210, Subpart C       NaN    1
4  CROWHEARTENERGYLLC    CP19‐050  Reports(Forms ONRR‐4054)for22production                 30CFR1241.50‐52    $5,544    7
5                 NaN         NaN     Business failed to report production     30 CFR Part 1210, Subpart C       NaN    1
6  CROWHEARTENERGYLLC    CP19‐050  Reports(Forms ONRR‐4054)for22production                 30CFR1241.50‐52    $5,544    2

out = (df.groupby(df['Business Name'].notna().iloc[::-1].cumsum().iloc[::-1], sort=False)
          .agg(lambda x: x.sum() if np.issubdtype(x.dtype, np.number) else ' '.join(x.dropna()))
          .reset_index(drop=True))

print (out)
        Business Name Case Number                                          Violation                                      Regulation(s)  Payments  col
0    CHI OPERATING CO    CP17‐085  Business knowingly or willfully sales months J...  30 CFR 1241.60(b)(1) 30 CFR  Part 1218,Subpart...  $142,310    5
1  CROWHEARTENERGYLLC    CP19‐050  Business failed to report production Reports(F...        30 CFR Part 1210, Subpart C 30CFR1241.50‐52    $5,544    8
2  CROWHEARTENERGYLLC    CP19‐050  Business failed to report production Reports(F...        30 CFR Part 1210, Subpart C 30CFR1241.50‐52    $5,544    3