I) Due to high solubility of ${\mathrm{KHCO}}_3$, it cannot be precipitated. Hence ${\mathrm{K}}_2{\mathrm{CO}}_3$  cannot be prepared by Solvay – ammonia process;
II) In Ammonia – recovery tower of the process

$2{\mathrm{NH}}_4\mathrm{Cl}+\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\to {\mathrm{CaCl}}_2+2{\mathrm{H}}_2\mathrm{O}+2{\mathrm{NH}}_3$
${\mathrm{NH}}_3$   is recycled, ${\mathrm{CaCl}}_2$ is the by product