KAUSAR AHMAD KULLIYYAH OF PHARMACY PHM3133 Dosage Design /11 1 Steam as a heating medium

Contents PHM3133 Dosage Design /11 2 Steam generation and use Water treatment Adverse effects of air in steam Heat content of steam Effect of pressure on steam properties

Requirement of a heating medium PHM3133 Dosage Design /11 3 High specific heat capacity Inert

Why is steam popular? PHM3133 Dosage Design /11 4 Cheap Abundance No residue (compare with water) Easy to clean

Equipment to produce steam PHM3133 Dosage Design /11 5 BOILER

Boiler System PHM3133 Dosage Design /11 6 Deaerator tank Ion-exchanger

BOILER PHM3133 Dosage Design /11 7 Type: water-tube OR fire-tube Fired by fossil fuel or electricity Specified by the capacity e.g. 5 barg or 20 barg Requirement Maintenance system Water treatment system Corrosion control

Components of a boiler PHM3133 Dosage Design /11 8 Boiler feedwater Ion exchanger Feedwater Deaerator STEAM Chemicals Heat transfer applications: Heating of water Drying of solids Blowdown (- TDS*) Brine (NaCl) * Total Dissolved Solids BOILER

Boiler Room PHM3133 Dosage Design /11 9 Would this be good enough for a steam bath? deaerator

Feedwater treatment PHM3133 Dosage Design / Removal of scale-producing elements such as calcium, magnesium & silica 2. Removal of dissolved oxygen and carbon dioxide that can cause corrosion in the boiler, piping and other components.

Type of feedwater treatment PHM3133 Dosage Design / Mechanical treatment Deaerator: a certain amount of oxygen and carbon dioxide are removed by introducing steam into the tank. 2. Chemical treatment Addition of chemicals Prevent scaling Reduce hardness: Ca 2+, Mg 2+ Scale acts as insulator

Mechanical treatment: Function of deaerator PHM3133 Dosage Design /11 12 To remove oxygen How? The solubility of oxygen in water decreases with increasing temperature Steam is introduced into the deaerator to increase the temperature of the deaerator to e.g. ca. 50ºC.

Chemical treatment programs PHM3133 Dosage Design /11 13 Coagulation - obsolete Add sodium carbonate Phosphate program - cheap Add sodium phosphate Require addition of dispersant Chelant program - expensive EDTA Complexation/dispersion polymers

Chemical Treatment PHM3133 Dosage Design /11 14 precipitates Ca 2+, Mg 2+, SiO2 sodium phosphate bridging flocculation polymer (polyacrylic acid) remove oxygen: 2SO O 2 = 2SO 4 2- sodium sulfite control alkalinity maintains solids in suspension (high ζ-potential) caustic soda (NaOH)

Maintenance PHM3133 Dosage Design / General maintenance due to corrosion e.g. tube replacement condensate pumps steam traps 2. Water treatment equipment 3. Ion-exchange resin

Disadvantages of steam boiler PHM3133 Dosage Design /11 16 Need water treatment to minimise corrosion Regular maintenance to maintain heat transfer efficiency blowdown water pre-treatment facilities

Effect of scale on heat transfer PHM3133 Dosage Design /11 17

Equipment failure PHM3133 Dosage Design /11 18

Adverse effects of air in steam PHM3133 Dosage Design /11 19 Corrosion How long can the boiler last? Lower heat transfer efficiency Air is an insulator Knocking Bad for structure of the boiler system Quality May affect product if in direct contact

How to calculate amount of heat transfer PHM3133 Dosage Design /11 20 PROBLEM: To heat 50 litres of water at 30ºC, how much energy is required? How much steam is required? Q = mc T Q: energy required (J) m: mass (kg) c: specific heat capacity (J/kg.ºC) T: change in temperature

Types of Steam PHM3133 Dosage Design /11 21 AUTOCLAVE Saturated steam (good for sterilisation) Superheated steam (not desirable) BOILER Wet steam (not desirable) dry steam (good for sterilisation) Separator to remove moisture

Exercise PHM3133 Dosage Design / What is the heat content of steam? 2. What is the effect of pressure on steam properties?

Conclusion: Steam as a choice PHM3133 Dosage Design /11 23 Cheap Non-hazardous Well-researched Simple operation Easy to maintain if proper procedures are followed

Reference PHM3133 Dosage Design /11 24 Aulton, M. (1988). Pharmaceutics. London: Churchill Livingstone. Rawlins, EA (1977). Bentleys Textbook of Pharmaceutics. East Sussex: Bailliere Tindall