🔍 Key Concepts

• Viscosity and temperature relationship for fuels and oily sludge • Effect of water content on the ability of sludge to burn on its own • Purpose of auxiliary fuel in sludge incinerators

💭 Think About

• Think about what happens to thick, heavy sludge when you heat it versus when you cool it — which action makes it easier to pump and burn? • Consider whether high water content makes burning easier or harder, and how that would affect the need for extra (auxiliary) fuel. • Identify which option correctly pairs: (1) how to get proper viscosity, and (2) when extra fuel is needed based on water content.

✅ Before You Answer

• Confirm whether increased temperature generally increases or decreases viscosity of heavy oils/sludge. • Decide if excess water in sludge makes it more or less able to sustain combustion by itself. • Match the correct combination of temperature treatment (heating vs cooling) and water-content effect (too high vs too low) before choosing an answer.