Evaluation and testing of fine mesh sieve technologies for primary treatment of municipal wastewater.

Fine mesh sieve technologies were tested in full scale at several municipal wastewater treatment plants. A screening test was used to characterize wastewater and establish the design criteria for the sieves. To achieve high removal efficiencies it was crucial to operate the sieves with a filter mat. Rotating belt sieves performed best in the full-scale tests. A small dose of cationic polymer and a static flocculator ahead of a rotating belt sieve achieved excellent results on a wastewater that was originally found unsuitable for primary treatment with fine mesh sieves. Simple screw presses dewatered the sludge from the sieves to typically 25-30% total solids. Using fine mesh sieves with <500 microns openings was found to normally be the most economical process for primary treatment.     

A study of film thickness and hydrodynamic entrance length in liquid laminar film flow along a vertical tube

The liquid film thickness and hydrodynamic entrance length in a vertical tube was studied experimentally and numerically. Measurements using distilled water, 30 wt % MEA and 40 wt % sugar solutions were carried out to investigate the effects of liquid flow rate on the formation of the liquid film. The experimental results validate the new Navier‐Stokes based equation in cylindrical coordinates (Eq. 16) and the volume of fluid (VOF) model giving a competitively high prediction of the liquid film thickness especially in the low Reynolds number region. In addition, a new empirical model and an improved minimal surface model have been first proposed for calculation of the hydrodynamic entrance length, with a relatively reasonable average absolute relative deviation (AARD) of 3.03% and 6.83%, respectively. Furthermore, the effects of the hydrodynamic entry length on the gas–liquid interfacial area calculated by the improved minimal surface model were comprehensively studied, and can be ignored if the ratio of the liquid film length (y) and the hydrodynamic entrance length (λ_E) is lower than 10. However, it should be noted that the hydrodynamic entrance length cannot be ignored in packed columns in which the liquid flow is very complex due to the packings with different structures and materials. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2078–2088, 2018     

Kinetics of CO2 absorption by aqueous 3‐(methylamino)propylamine solutions: Experimental results and modeling

Experimental data and a model for the initial kinetics of CO₂ into 3‐(methylamino)propylamine (MAPA) solutions are presented in work. MAPA has been tested as an activator for tertiary amines with encouraging results. The measurements were performed in a string of discs contactor and, as no initial kinetics data are available in literature, additional measurements were carried out and in a wetted wall column. The obtained overall mass‐transfer coefficients from both apparatuses are in reasonable agreement. To obtain values for the observed kinetic constant, , the experimental results were interpreted using a two‐film mass‐transfer model and invoking the pseudo‐first order assumption. Needed experimental values for density, viscosity, and Henry's law coefficient for CO₂ were measured and are given. The results indicate that MAPA is almost twice as fast as piperazine, eight times faster than 2‐(2‐aminoethyl‐amino)ethanol (AEEA), and 15 times faster than monoethanolamine, when comparing unloaded 1 M solutions at 25°C. The observed kinetic constant was modeled using the direct mechanism. The final expression for can be applied for any concentration and temperature within the experimental data range, and, together with the presented physical data, comprises a complete model for calculating absorption fluxes. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3792–3803, 2014     

CO2 capture into aqueous solutions of piperazine activated 2-amino-2-methyl-1-propanol

In this work, experimental data and a simplified vapor–liquid equilibrium (VLE) model for the absorption of CO₂ into aqueous solutions of piperazine (PZ) activated 2-amino-2-methyl-1-propanol (AMP) are reported. The purpose of the work was to find the AMP/PZ system with the highest concentration and cyclic capacity, which could be used in the industry without forming solid precipitations at operational temperatures. The effect of the AMP/PZ ratio and the total concentration level of amine was studied. The highest possible ratio of AMP/PZ, which does not form solid precipitates during the absorption of CO₂ at 40 °C (40 wt% amine), was identified. Considering the maximum loading found in the screening tests for AMP/PZ (3+1.5 M) and for 30 wt% MEA systems, the AMP/PZ system has about 128% higher specific cyclic capacity if operating between 40 and 80 °C, and almost twice the CO₂ partial pressure at 120 °C compared to MEA.     

Degradation of MMEA at absorber and stripper conditions

This study examines the degradation of N-methylethanolamine (MMEA) under different experimental conditions. Thermal degradation with and without CO₂, and oxidative degradation are investigated. Samples of the degraded solution were taken at regular intervals and analyzed. The percentage of amine loss was determined by Liquid Chromatography–Mass Spectrometry (LC–MS) while the degradation compounds were identified and quantified by Gas Chromatography–Mass Spectrometry (GC–MS). MMEA degradation at absorber and stripper conditions is compared with previous work on 2-ethanolamine (MEA). Degradation mechanisms are proposed and discussed in order to understand the differences compared to MEA.     

Operation and dynamic behavior of wire mesh pads

Holdup distribution, pressure drop, separation efficiencies and droplet separation characteristics of six different wire mesh pads were investigated experimentally. One of the mesh pads was tested with and without a small gas bypass at the wall. The liquid holdup was recorded at minimum five locations inside the pads. The holdup distribution in the mesh pads were tested for time dependency. Separation efficiencies and droplet size distribution for the empty column was also investigated. The results show variations in the holdup profile of the pads depending on running time, pad geometry, gas velocity and measuring position. A new equation was derived and a new parameter proposed to describe the characteristics of mesh pad operations.     

Vapor–liquid equilibrium in the sodium carbonate–sodium bicarbonate–water–CO2-system

Vapor–liquid equilibria of the carbon dioxide loaded sodium carbonate–water system were measured in the temperature range 40–80 °C and for sodium carbonate concentrations 8–12 wt%. In addition the vapor pressure of water over 10–30 wt% sodium carbonate solutions for the temperature range 27–100 °C was measured in an ebulliometer. The system was modeled using the electrolyte-NRTL model. Experimental vapor–liquid data from this study as well as data available in the literature from 25 to 195 °C and for sodium carbonate concentrations from 0.5 to 12 wt% were used for parameter fitting. The average deviation of the model predictions compared to all experimental data found is 9.8% for the partial pressure of CO₂. For vapor pressure of water the standard deviation is 0.6% up to 100 °C and 30 wt% sodium carbonate solutions.