Comparison Between Methods Of Synthetic Ammonia Separation And Primary Study On The Adsorption Separation

Synthetic ammonia is the product with high energy consumptions, and the one of reasons is the high pressure. Ammonia separation by condensation not only expends the much of refrigeration work, but also limits to decrease the pressure in ammonia synthesis. But the ammonia separation by absorption and adsorption can not be restricted by gas-liquid equilibrium of ammonia, and it is hoped that the good effect is obtained at low pressure. Ammonia separation processes from the mixture gases with condensation, absorption by lithium nitrate, and adsorption by alkaline-earth metals chloride were simulated. The effects of cooling-water temperature and heating temperature were focused on. The feasible temperature is 80℃in absorption separation by lithium nitrate, and the quantity of heat is least at this temperature; the quantity of heat is least at 106℃in adsorption separation by calcium chloride and 80℃by strontium chloride. Exergy consumptions were compared at the same conditions in condensation, absorption and adsorption separations. The exergy consumption was the most in condensation separation, and about 2003.5kW; the least in absorption separation by lithium nitrate; and about 1078.0kW, and about 1798.3 kW and about 1666.8 kW in adsorption separation by calcium chloride and strontium chloride respectively. Lower exergy consumptions in absorption and adsorption processes can show the advantages. At last adsorption was selected because of the effect of solution on the catalyzer and the solution pump at high pressure in absorption process. Pulverization and expansion were shown when adsorbed and desorbed with alkaline-earth metals chloride again and again, and so composite adsorbents were prepared from macro-pore silica gel and calcium chloride. The effect of baking temperature on ammonia adsorption capability was researched and the most adsorption capability of ammonia is about 1.16 ～1.20 gNH3/gCaCl2 when composite adsorbent is baked at 400~500℃. Effect of pressure on the ammonia adsorption capability of composite adsorbent is small. When the pressure is at 0.4~0.8MPa, the ammonia adsorption capability is about 1.206gNH3/gCaCl2, and is not changed almost at different pressure when adsorbed at 35℃. Ammonia adsorption capability is increased slowly with the pressure when adsorbed at 110℃. When the cooling-water temperature is respectively 25℃and 32℃, the ammonia separation capability is respectively 0.85gNH3/gCaCl2 and 0.84gNH3/gCaCl2 when adsorbed at 35℃and desorbed at 110℃. And the ammonia separation capacity of composite adsorbent is very high. It is suggested in the more work that the conditions for monolayer disperse of calcium chloride and strontium chloride on carriers should be more researched. The foundation is established for the development of ammonia composite adsorbents loaded with alkaline earth chloride.