In plants where multiple boilers are used to meet the steam demand, at part loads the most efficient boilers should be used.
In many industrial facilities steam is generated by employing a battery of boilers. This may either be a scheme where both the boilers run continuously at part loads or the scheme consists of a ‘lead’ boiler and a ‘follow on’ boiler. In the second case the lead boiler caters to the average steam demand of the plant and the follow on comes into operation to meet the peak steam demands.
In the case of a lead and follow on boiler, using the most efficient boiler as the lead boiler will save fuel. For this it is essential to know the operating efficiencies of the boilers on a regular basis.
With such an arrangement the most efficient boiler will be in operation continuously, while the boiler with lesser efficiency will operate only for a short period of time, when the peak demand occurs.
Consider a battery of two FO fired boilers, where the average steam demand is 4.5TPH and peak demand is 9TPH which occurs for 3 hrs in every 24hrs. In the table below we present two cases: first, where boiler A is used as the lead boiler and second, where boiler B is used as the lead boiler.
Thus if we use boiler A as the lead boiler and B as follow on, instead of vice versa, we save close to Rs.30 lakhs annually!