A simple model for desulphurisation of flue gas using reactive filters

Abstract

Desulphurisation of flue gas is essential before it can be released safely into the atmosphere. One way of removing sulphur dioxide is to use a purification device incorporating a reactive filter, in which the flue gas stream passes in front of a porous-catalyst-filled structure which converts the gaseous sulphur dioxide into liquid sulphuric acid. In this paper, we build and solve a simple mathematical model to describe the operation of a paradigm reactive filter. Our model captures the transport of sulphur dioxide through the device via advection in the main “outer” flow and diffusion through the catalyst structure along with the production of sulphuric acid. This sulphuric acid gradually accumulates in the filter rendering it less efficient. We determine the clogging time for an individual channel (that is, the time at which the entrance to the channel becomes completely filled with liquid) and explore how the concentrations of sulphur dioxide and oxygen and the thickness of the sulphuric acid layer change as the key dimensionless parameters are varied, comparing numerical and asymptotic results where appropriate. We then turn our attention to the device scale and solve our model numerically to determine the overall lifetime of the device. We vary the key dimensionless parameters and explore how they affect the efficiency of the device. In the physically relevant parameter regime, we find an explicit solution to the outer flow problem which agrees well with numerical solutions and provides a formula for the lifetime of the device. Finally, we propose a formula for determining the catalyst reaction rate, given data on the concentration of sulphur dioxide exiting the device.

The role of adsorbent microstructure and itspacking arrangement in optimising theperformance of an adsorption column

“…The modelling of adsorption processes usually consists of an advection-diffusion equation, with concentrations averaged across the cross-section of the column, coupled with a sink term that accounts for either the average mass adsorbed inside the pellets [10][11][12][13][14][15], or the mass that diffuses through the boundary between the inner pores of the pellet and the region where the fluid is flowing. In the latter case, the concentration inside the pores might be volume averaged [16,17] or a diffusion-reaction equation is also added to model the mass transport through the pores [7,18,19]. The adsorption kinetics are also highly dependent on the type of adsorption occurring.…”

“…The adsorption kinetics are also highly dependent on the type of adsorption occurring. Although the Linear Driving Force approach [10][11][12] and Langmuir kinetics [13][14][15][16] are commonly used in the literature, some works use higher-order kinetic laws related to the type of adsorbate-adsorbent bonding [10,13,18,19]. Although the velocity is usually assumed to be spatially uniform, some authors account for variable velocity when high concentrations, and thus volumes, of contaminant are being removed [12,15].…”

Converter inlet temperature control in flue gas acid‐making process based on equivalent input disturbance and model prediction

“…Meanwhile, flue gas acid production is also an important sulfuric acid production method in industry. This method of acid production not only reduces air pollution and soil acidification caused by the emission of large amounts of sulfur‐containing flue gas, but also reduces the waste of resources and increases the profitability of metal smelters 5,6 . The flue gas acid production mainly includes four processes: purification section, conversion section, dry suction section and waste acid treatment section.…”

“…This method of acid production not only reduces air pollution and soil acidification caused by the emission of large amounts of sulfur-containing flue gas, but also reduces the waste of resources and increases the profitability of metal smelters. 5,6 The flue gas acid production mainly includes four processes: purification section, conversion section, dry suction section and waste acid treatment section. The conversion section is the core link of the flue gas acid production process, and the core equipment of this stage is the converter.…”