Energy consumption of a process plant depends on the use and misuse of total energy supplied to it. When every input to the chemical process plant, may be in terms of power, water, raw materials or even exhaust will represent energy and money. For an existing plant production cost, depend highly on the energy consumption followed by raw material.
By the help of modelling and simulation tools the energy flow is monitored and the system is audited to obtain improvement in energy-saving. In most of the process plant, steam loss is a worrying corner for an energy auditor. Let us observe an energy system in sulphuric acid production plant . Optimum layout contains these section, roaster, sulphuric acid, phosphoric acid section, nitric acid, power section, and some include fertilizer section. Leaving out laboratory, administration and other electrical consumption builds when we focus on machinery section, they are much lesser in quantity. Due to exothermic nature, process is main concern for an energy auditor.
Sulphuric acid plant is a steam generator. The heat from flue gas of its roaster transferred to water network converting it into super heated steam approximately about 7-9 kg/sec. Similarly, in nitric acid preparation when ammonia is burned it produce flue gas capable of generating steam. However, phosphoric acid plant is a consumer of steam. Power plant uses the remaining steam energy to run the turbines to generate electricity for the plant.
Some of the remarks that affect the heat integration network are insufficient combustion of fuel due to error in stoichiometric air ratio, quality of water used for steam generation, and steam traps malfunctioning.
Main energy transfer systems in Sulphuric Acid Production
- Cooling system/ water recycle
- Steam generation system / condensate recycle
Process equipments involve in cooling circuit loop
- Evaporative cooling tower
- Absorber acid cooling
- Main acid cooler
- Product acid cooler
- Electricity generation turbine surface condenser
Process equipments involve in heating circuit
- Oven/ Roaster
- Waste heat boiler
- Super heater
- Plate heat exchanger