Simplified plantwide control structure for the diethyl oxalate process

The diethyl oxalate process features two reaction sections with two of the fresh feeds (oxygen and ethanol) and a recycle stream containing nitric oxide fed into the first reactor, which produces ethyl nitrite and water. Water is removed in a distillation column and the ethyl nitrite is fed to the second reactor along with the third fresh feed (carbon monoxide). Diethyl oxalate and nitric oxide are produced in this reactor. The product diethyl oxalate is recovered in a distillation column, and the nitric oxide is recycled back to the first reactor. The intermediate components (nitric oxide and ethyl nitrite) and inert nitrogen circulate between the two reaction sections. A recent paper proposed a plantwide control structure for this complex process that requires four on-line composition controllers to handle disturbances in throughput and the compositions of the three fresh feed streams. The purpose of this paper is to demonstrate that a less complex control structure with only one composition measurement can achieve stable regulatory control. (C) 2019 Elsevier Ltd. All rights reserved.