... s; it can save the back-flush water more than 30-50%;3. High surface area, large pore volume, the ... resistance,%≤0.5- Compressive strength, N30-150- Water permeability,t/m2.h2-4- Gas permeability,m3/m2h.h1500-2000- Thermal ... resistance,≥1000- Acid resistance,99.5Mixed in 30% HCl+50% H2SO4 solution for 14 days Alkali resistance, ... 8-10,Φ10-12,Φ13-16,Φ16-20,Φ20-30. Ceramic Sand Filters