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, maybe 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, the steam loss is a worrying corner for an energy auditor. Let us observe an energy system in the sulphuric acid production plant. The 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 buildings when we focus on machinery section, they are much lesser in quantity. Due to exothermic nature, the process is the main concern for an energy auditor.
The sulphuric acid plant is a steam generator. The heat from the flue gas of its roaster transferred to water network converting it into superheated steam approximately about 7-9 kg/sec. Similarly, in nitric acid preparation when ammonia is burned, it produces flue gas capable of generating steam. However, the phosphoric acid plant is a consumer of steam. The 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 an 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 types of equipment involved in the cooling circuit loop
- Evaporative cooling tower
- Absorber acid cooling
- Main acid cooler
- Product acid cooler
- Electricity generation turbine surface condenser
Process equipments involved in the heating circuit
- Oven/ Roaster
- Waste heat boiler
- Plate heat exchanger