Conclusions

Steam network optimization is done through replacing biomass and solar energies in Tehran oil refinery. To achieve this aim, a steam network model is introduced. This model allows interactions between the steam sources and consumers to be explored. Having considered solar and biomass energies for generating steam the model is further improved. Three scenarios are investigated to achieve minimum total cost and payback period. In the suggested scenarios, different opportunities for integrating purposes are considered and the optimum case is selected. From this study we can extract the following remarks:

• The results of steam network optimization have indicated 10.25% energy saving and approximately $10 million operating cost saving per year.

• Application of integrating alternatives in refinery resulted in ecological benefits. High emission reduction of CO2 and SO2 is achieved.

• For making decision of the best case, existing trade-off between payback period and emission reduction should be considered.

The investigation of the discussed scenarios reveals that considering the economical aspect, the SGB scenario has achieved minimum payback period. However, on the basis of environmental issue, the SGDBS scenario has accomplished minimum

emission.

Nomenclature

A

minimum steam flow rate, kg/s

B

maximum steam flow rate, kg/s

Cp

specific heat, J/kg°C

E

turbine output power, W

hi

enthalpy of boiler inlet water, kJ/kg

h2

enthalpy of steam raised by boiler, kJ/kg

H

Enthalpy, kJ/kg

HP

high pressure

LP

low pressure

M

Incremental steam flow rate, s2/m2

M

flow rate, kg/s

MP

medium pressure

MSW

Municipal solid waste

N

inverse incremental steam flow rate, m2/s2

Q

specific heat load of steam, kJ/kg

Q

heat load, W

SGB

steam generation by biomass

SGDBS

Steam Generation at Different levels via Biomass and Solar

SGSBS

Steam Generation at Same level by Biomass and Solar

T

temperature, °C

Greek Letters A difference

H efficiency, %

Subscripts

B boiler

T turbine

F fuel gas

Sat saturated

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