Large Volume Inorganic Chemicals - Ammonia ... - ammk-rks.net

Chapter 6Cross-media effectsEnergy, water and, in the case of alkaline scrubbing, chemicals consumption.Operational dataThe equipment necessary for HF absorption is typically made of rubber lined steel or massivePVC, polypropylene or polyethylene (optionally it may be fibre glass reinforced).ApplicabilityGenerally applicable. Scrubbing with water or alkaline solution is a well established and proventechnique.Liquid phase alkaline absorption (single-stage) is sufficient for limited or intermittent HF flows.As neither HF nor alkali are recovered in this option, and as large quantities of NaF in the wastewater can be a problem, this solution is not recommended for large continuous amounts of HF.In this case, the solution developed in the combination of water and alkaline absorption ispreferred.Solid alkaline absorption in a fixed bed is an economic possibility for small effluent streams ofmoist gases containing HF.EconomicsSee also Table 6.10.The investment for a 100 m 3 /hour gas flow in a single-stage, once-through absorption is in therange of EUR 50000 – 80000 (data valid for new plants).For a double-stage gas treatment, the investment cost is in the range of EUR 150000 – 200000(new plants), or EUR 2000 – 4000 per 1000 m 3 /hour.A significant additional investment cost may arise if no alkaline solution is available on-site. Insuch a case, the installation of a tank, a transfer line and an unfilling station may be necessary.Operating costs mainly involve alkali consumption (if any), energy consumption, liquid effluentneutralisation and maintenance costs. For HF solution recovery, the alkali consumption is verylow (disregarding the SO 2 absorption). When HF is not recovered, an equivalent alkali flow isconsumed, either at the absorption step or at the effluent neutralisation step. This is not true if analkaline effluent is yielded by another production unit, with a mixing of the two flows in acommon effluent treatment. There the energy consumption basically corresponds to waterpumping and is usually not critical.Maintenance costs are usually around 5 % of the investment costs per year of operation.References to literature and example plants[22, CEFIC, 2000], [6, German UBA, 2000] three example plants listed in this reference.274 Large Volume Inorganic Chemicals – Ammonia, Acids and Fertilisers