What problem can arise from injecting too much phosphate into the boiler?

Injecting too much phosphate into the boiler can lead to phosphate sludge formation, which is the correct answer. Phosphates are used in boiler water treatment to prevent scale formation and to bind calcium and magnesium ions, which are responsible for hardness. However, when excessive phosphate is introduced, it can react with calcium and magnesium in the water beyond what is needed for treatment, leading to the formation of insoluble phosphate compounds. These compounds can aggregate to form sludge, which can settle in the boiler and create a number of operational issues.

The accumulation of phosphate sludge can restrict water flow, reduce heat transfer efficiency, and cause localized overheating due to the insulating properties of the sludge. This can ultimately lead to costly maintenance and operational challenges, including potential damage to the boiler.

In contrast to this, increased fuel efficiency, reduced steam production, and chemical corrosion are not direct consequences of excessive phosphate injection. Injecting the appropriate amount of phosphate is essential for optimal boiler operation, but exceeding this limit disrupts the balance, resulting in the specific issue of sludge formation.