Analysis of the efficiency of the use thermal TSR based on the organic Rankine cycle in the production of nitric acid

Abstract

The paper shows an energy-saving effect based on on the organic Rankine cycle (ORC) when using thermal secondary energy resources (SER) for the production of non-concentrated nitric acid (NNA).The production of non-concentrated nitric acid in the Russian Federation is carried out on two types of aggregates: UKL-7 and AK-72. Each unit currently has upgraded versions: UKL-7M and AK-72M, in which the design production capacity has been increased. Nitric acid production at the UKL-7 unit is carried out at a uniform pressure of 0.716MPa at the stages of ammonia conversion and absorption of nitrous gases by water. Acid production on the AK-72 unit is carried out at different pressures at the stages of ammonia conversion and absorption. Ammonia conversion on the AK-72 unit proceeds at a pressure of 0.42 MPa, whereas the absorption process is carried out at a pressure of 1.1 MPa. In this paper, by way of example, the UKL-7 unit is considered. A useful use of SER based on the ORC is to use the heat of compressed air after the axial compressor, which is released into the environment. In this case, the heat of compressed air is used for heating and evaporation of freon in the evaporator of the cycle, heating feed water in front of the deaerator in order to reduce steam consumption. It is also proposed to use the heat of condensation of freon after the turboexpander to evaporate ammonia, which also leads to a reduction in steam consumption. It is proposed to use freon R600a in the ORC.The calculation results show that when using the heat of compressed air and the heat released in the EGU condenser, it is possible to generate about 2,613,600 kWh/ year of electricity, as well as save 39,630 tons of steam per year.