Tunnel-redesigned O2-tolerant CO dehydrogenase for removal of CO in real flue gas

Carbon monoxide dehydrogenase (CODH)-catalyzed oxidation of CO to CO2 provides a promising means of removal of toxic and waste CO from industrial flue gas despite of the lack of active and stable enzymes in the atmosphere. Herein we present rationally and selectively redesigned ChCODH-II (Carboxydothermus hydrogenoformans) variants by engineering gas tunnels in order for O2-tolerant CODHs to catalyze efficient CO oxidation under oxygen (O2). Using the redesigned ChCODH-II A559W and A559H variants showing 42- and 128-fold elevation of O2 tolerance, respectively, complete CO removal was achieved under a near-atmospheric condition. Moreover, these variants efficiently removed CO from industrial flue gas (Linz–Donawiz converter Gas: LDG) discharged from a steel mill despite the high O2 level (13.4%) during successful and repeated reuse after immobilized on Ni-NTA agarose beads. Our study will provide insights into redesigning the transformation of O2-sensitive CODHs into tolerant enzymes for use as workhorses for conversion of toxic or waste gases into safe or value-added chemicals.

MATHEMATICAL MODEL AND ALGORITHM FOR CALCULATION OF THERMAL STATE OF A REGENERATOR ACCUMULATING CONVERTER GAS HEAT OF COMBUSTION AND HEATING AIR FOR A RECOVERY BOILER

The heat of combustion of the converter gas, which is periodically formed in the oxygen-converter production at the metallurgical plant, is proposed to be used for alternate heating of the checkerwork of two regenerators (such as сowpers), and their alternate cooling by a continuous flow of air heated to a high temperature, and directed to the recovery boiler to generate steam. A mathematical model is presented that allows evaluating the thermal state of the regenerator, the temperatures of the heating gases and the heated air in the modes of heating and cooling the regenerator checkerwork. An algorithm for numerical calculation of the temperature fields of the regenerator checkerwork, gases and air is presented.

A Mixed Integer Linear Programming Model for the Optimization of Steel Waste Gases in Cogeneration: A Combined Coke Oven and Converter Gas Case Study

Off-gas is one of the by-products of the steelmaking process. Its potential energy can be transformed into heat and electricity by means of cogeneration. A case study using a coke oven and Linz–Donawitz converter gas is presented. This work addresses the gas allocation problem for a cogeneration system producing steam and electricity. In the studied facility, located in northern Spain, the annual production of the plant requires 95,000 MWh of electrical energy and 525,000 MWh of thermal energy. The installed electrical and thermal power is 20.4 MW and 81 MW, respectively. A mixed integer linear programming model is built to optimize gas allocation, thus maximizing its benefits. This model is applied to a 24-h scenario with real data from the plant, where gas allocation decision-making was performed by the plant operators. Application of the model generated profit in a scenario where there were losses, increasing benefits by 16.9%. A sensitivity analysis is also performed. The proposed model is useful not only from the perspective of daily plant operation but also as a tool to simulate different design scenarios, such as the capacity of gasholders.