Page 12 - Bosch Modernisation of Boiler Systems

12 | Modernisation of boiler systems

Example of an application: Switching from oil

to gas at a medium-sized German company

A typical medium-sized German company with a 6-day week and double-shift operation is the basis for

the following calculation example. The steam boiler is 15 years old and is mostly operated at partial load.
Due to the extension of the gas supply network, the company can switch their boiler to natural gas.

Load profile of industrial operation Key data
Steam boiler with an output of 10 t/h and an
Boiler load in % operational pressure of 10 bar, using light fuel oil and
Annual operating hours a burner with mechanical linkage, without an
economizer and with a condensate rate of 2,000 kg/h:
4,000 h 6 % oxygen-free, 50 % with oxygen, average load
3,500 h 3,900 kg/h, 5,000 operating hours per year following
3,000 h the shown load profile.
2,500 h 5,000 h of boiler operation
2,000 h Fuel and power prices
1,500 h ▶ Light fuel oil: 0.44 euro per kg (0.375 euro per l)
1,000 h ▶ Natural gas H: 0.30 euro per m3N
500 h
▶ Power: 0.16 euro per kWh
0 h ▶ Water price: 2 euro per m3
0 % 20 % 40 % 60 % 80 % 100 %
▶ Waste water price: 2 euro per m3

The conclusion
The customer undertakes extensive modernisation of the There is a total saving of 5 million euros over the predicted
system, including integration of heat recovery units. The remaining lifespan of the boiler of 15 years – a significant
renewal of the burner is amortised in just four months contribution to increasing competitiveness and profitability.
and the entire investment in less than seven months.

Modernisation measure* Cost saving CO2 reduction Investment Amortisation
in euros in tons in euros time in months
Switching to natural gas 244,000 2,000 80,000 4
Economizer 55,000 370 50,000 11
Condensing heat exchanger 46,000 310 60,000 16
Fan speed control 6,000 20 10,000 19
O2 and CO control 5,000 30 15,000 40

Heat recovery from desalting 18,000 120 10,000 6
Total 374,000 2,850 225,000 7

* Depending on load behaviour and condensate parameters, other measures such as air preheaters, feed water coolers, vapour heat
exchangers or condensate heat exchangers may be financially justifiable.