Pilot-scale Test Results Research Articles

Evaluating the potential of CNT-supported Co catalyst used for gas pollution removal in the incineration flue gas

This study investigated the use of Cu/Al 2O 3, Co/Al 2O 3, Fe/Al 2O 3, and Ni/Al 2O 3 catalysts for the growth of carbon nanotubes (CNTs). These CNTs were used as support for Co catalyst preparation and Co/CNT catalysts were applied to a catalytic reaction to remove BTEX, PAHs, SO 2, NO, and CO simultaneously in a pilot-scale incineration system. The analyzed results of EDS and XRD showed low metal content and good dispersion characteristics of the Al 2O 3-supported catalysts by excess-solution impregnation. FESEM analyzed results showed that the CNTs that were synthesized from Co, Fe, and Ni catalysts had a diameter of 20 nm, whereas those synthesized from Cu/Al 2O 3 had a diameter of 50 nm. Pilot-scale test results demonstrated that the Co/CNT catalyst effectively removed air pollutants in the catalytic reaction and that there was no obvious deactivation by Pb, water vapor, and coke deposited in the process. The thermal stabilization at 250 °C and hydrophobicity properties of CNTs enhanced the application of CNT catalysts in flue gas.

Particle imaging of ignition and devolatilization of pulverized coal during oxy-fuel combustion

Oxy-fuel combustion of coal is a promising technology for cost-effective power production with carbon capture and sequestration that has ancillary benefits of emission reductions and lower flue gas cleanup costs. To fully understand the results of pilot-scale tests of oxy-fuel combustion and to accurately predict scale-up performance through CFD modeling, fundamental data are needed concerning coal and coal char combustion properties under these unconventional conditions. In the work reported here, the ignition and devolatilization characteristics of both a high-volatile bituminous coal and a Powder River Basin subbituminous coal were analyzed in detail through single-particle imaging at a gas temperature of 1700 K over a range of 12–36 vol % O 2 in both N 2 and CO 2 diluent gases. The bituminous coal images show large, hot soot cloud radiation whose size and shape vary with oxygen concentration and, to a lesser extent, with the use of N 2 versus CO 2 diluent gas. Subbituminous coal images show cooler, smaller emission signals during devolatilization that have the same characteristic size as the coal particles introduced into the flow (nominally 100 μm). The measurements also demonstrate that the use of CO 2 diluent retards the onset of ignition and increases the duration of devolatilization, once initiated. For a given diluent gas, a higher oxygen concentration yields shorter ignition delay and devolatilization times. The effect of CO 2 on coal particle ignition is explained by its higher molar specific heat and its tendency to reduce the local radical pool. The effect of O 2 on coal particle ignition results from its effect on the local mixture reactivity. CO 2 decreases the rate of devolatilization because of the lower mass diffusivity of volatiles in CO 2 mixtures, whereas higher O 2 concentrations increase the mass flux of oxygen to the volatiles flame and thereby increase the rate of devolatilization.

Mercury removal from coal combustion by Fenton reactions. Paper B: Pilot-scale tests

This second paper in a series describes results of pilot-scale testing for mercury (Hg) removal from coal combustion flue gas using a scrubbing solution based on the Fenton reactions. The selected reagents contain hydrogen peroxide and iron salts. The mercury scrubbing was performed in a condensing heat exchanger (CHX) with flue gas generated by coal combustion in CANMET’s vertical combustor research facility (VCRF). Both the Ontario Hydro method and a Hg CEM were used for Hg sampling and speciation. The results, obtained with the combustion of three different pulverized coals – bituminous, sub-bituminous and lignite – showed that the CHX was very effective in removing oxidized mercury (Hg(II)). Concerning the performance of the scrubbing solutions, 30–40% of elemental mercury (Hg(0)) oxidation was achieved for the lignite coal, with the solution being preferably composed of FeCl 3 and H 2O 2 and with pH value between 1 and 3. Results also showed that better Hg removal results were achieved by combining sulphur removal and Hg removal in the same stage of the CHX. An additional test done on the pilot-scale research boiler with a conventional wet scrubber showed that the Hg removal capability using the Fenton reactions was not dependent on the configuration of the wet scrubber. Although the Hg(0) oxidation ratio was not particularly high compared to the achievements from bench-scale tests, considering the economic and non-toxic nature of the scrubbing solution and the readily available equipment, the current results are encouraging and deserve further work to develop a better understanding of the chemistry in order to determine if the method can be further optimized.

Combustion kinetics of coal chars in oxygen-enriched environments

Oxygen-enhanced and oxygen-fired pulverized coal combustion is actively being investigated to achieve emission reductions and reductions in flue gas cleanup costs, as well as for coal-bed methane and enhanced oil recovery applications. To fully understand the results of pilot scale tests and to accurately predict scale-up performance through CFD modeling, accurate rate expressions are needed to describe coal char combustion under these unconventional combustion conditions. In the work reported here, the combustion rates of two pulverized coal chars have been measured in both conventional and oxygen-enriched atmospheres. A combustion-driven entrained flow reactor equipped with an optical particle-sizing pyrometry diagnostic and a rapid-quench sampling probe has been used for this investigation. Highvale subbituminous coal and a high-volatile eastern United States bituminous coal have been investigated, over oxygen concentrations ranging from 6 to 36 mol% and gas temperatures of 1320–1800 K. The results from these experiments demonstrate that pulverized coal char particles burn under increasing kinetic control in elevated oxygen environments, despite their higher burning rates in these environments. Empirical fits to the data have been successfully performed over the entire range of oxygen concentrations using a single-film oxidation model. Both a simple nth-order Arrhenius expression and an nth-order Langmuir–Hinshelwood kinetic equation provide good fits to the data. Local fits of the nth-order Arrhenius expression to the oxygen-enriched and oxygen-depleted data produce lower residuals in comparison to fits of the entire dataset. These fits demonstrate that the apparent reaction order varies from 0.1 under near-diffusion-limit oxygen-depleted conditions to 0.5 under oxygen-enriched conditions. Burnout predictions show good agreement with measurements. Predicted char particle temperatures tend to be low for combustion in oxygen-depleted environments.

Surface aeration and a small footprint can be combined

In densely populated areas new WWTPs will need to be designed on a relatively small area. This paper describes a deep Carrousel (oxidation ditch) concept resulting in a "small footprint" for the aeration basin combined with an efficient and flexible oxygen input. To enable surface aeration in a deep Carrousel system, the basin was provided with so-called draft tubes, vertical cylinders located underneath aerators, almost extending down to the bottom. A draft tube enables the aerator to draw sludge/water mixture from the bottom of the tank, thereby ensuring proper oxygenation of the tank contents over the entire tank depth. The results of pilot-scale tests for verification of the performance of an aerator equipped with a draft tube are presented. The full scale WWTP Leidsche Rijn, a compact "wrapped-around" Carrousel-3000 system where the draft tube technology is applied in a 7.5 metre deep basin, is described. Before the plant was put into operation a verification test for the aeration efficiency with clean water was carried out. The test showed that the draft tubes have no negative impact on the aeration efficiency of the surface aerators and justified the chosen design concept.

Coarse particle concentration using the HydroFloat Separator

A new separator, known as the HydroFloat cell, was developed to overcome the limitations of traditional flotation cells in recovering coarse particles. The HydroFloat cell separates particles based on differences in mass after the selective attachment of air bubbles to the hydrophobic component of the feed stream. Proof-of-concept testing, utilizing phosphate matrix, heavy mineral sands and anthracite slag, indicated that significant improvements in separation efficiency can be achieved using this air-assisted teeter-bed system. Based on the encouraging laboratory results, a pilot-scale HydroFloat cell was fabricated and installed at a central Florida phosphate plant. Test data collected using the pilot-scale unit suggest that the BPL recovery of the +35-mesh plant feed can be increased by more than 40% through the application of this new technology. This improvement is particularly beneficial due to the very high grade (≈73% BPL) of the +16-mesh particles in the HydroFloat concentrate. This article describes the theoretical basis for the development of the HydroFloat cell and provides an overview of recent laboratory and pilot-scale test results.

PH measurement and control in solvent extraction using column contractors

pH measurement and control in a solvent extraction process using column extractors is a considerable challenge. This paper summarises the progress of WMT's understanding of the emulsion characteristics, hydraulic and kinetic regimes existing in the column extractors and their effects on pH measurement and control. Three sets of pilot scale test results are provided for a case study of nickel solvent extraction using Versatic 10 in a column extractor, with ammonia solution as the pH modifier. Initially the pH in extraction columns was controlled by directly dosing ammonia into the column to achieve the pH set point. The pH was measured in-situ by a pH meter inserted directly into the column. It was found that the ammonia tended to flow upwards with the organic rather than downwards with the aqueous flow, as would be expected, in an organic continuous operation. In the second test, the barren organic was pre-equilibrated with ammonia via an in-line mixer prior to entering the column. The pre-equilibrating ratio was proportional to the nickel pregnant liquor solution (PLS) tenor and the flowrate of the various phases. The final aqueous pH was used to tune the ratio. This resulted in a significant improvement in control of the pH in the column. In the third test, a combination of pre-equilibration and direct ammonia injection was used. The pH control in the column was very stable and a desirable pH profile in the column was achieved to maximise nickel recovery and reduce impurity co-extraction.

Construction Use of Vitrified Chromium-Contaminated Soils

This paper describes the test results of a demonstration study on the use of vitrified soils as highway construction aggregates. It is based on a bench- and pilot-scale feasibility study of the remediation of chromium-contaminated soil through cold top ex situ vitrification, making glass from wastes. Based on bench- scale tests, approximately six tons of chromium-contaminated soil from two different sites were vitrified. To determine the suitability as construction aggregate, vitrified soils were subjected to several tests. The bench- and pilot-scale test results were compared with New Jersey Department of Transportation (NJDOT) and ASTM specifications for construction aggregates. The results showed that the vitrified soils could be accepted as an aggregate material. Then the vitrified chromium-contaminated soils were used as aggregate in hot mix asphalt (HMA). Mix designs were performed to determine the maximum amount of vitrified chromium-contaminated soils that can be added to make satisfactory hot mix asphalt concrete mixes. The test showed that it is possible to include up to 58.8% of vitrified chromium-contaminated soils from both sites in HMA mixes. In order to evaluate the performance of HMA made with vitrified chromium-contaminated soils, the Marshall test, the durability test, and the hydraulic conductivity test were performed. The hot mix asphalt concrete mixes made with vitrified soil performed very well, suggesting the suitability of using vitrified chromium-contaminated soils in construction.

Classification and froth flotation of fly ash for producing high-quality pozzolan

The combination of froth flotation and hydraulic classification can facilitate the production of a high-quality pozzolan that meets or exceeds ASTM specifications. This combination has been rigorously evaluated and results of pilot-scale testing are presented. Pilot-scale testing was conducted on fly ash from two active electric utility storage ponds. The tests demonstrated that a high-quality and consistent pozzolan could be produced using Advanced Pozzolan Technologies’ Fast Float™ Process. Along with the pozzolan, the additional production of aggregate for masonry mortar and the production of a low sulfur, medium-Btu fuel were also demonstrated. The Fast Float™ Process incorporates several simple unit processes to ensure pozzolan consistency. Classification controls the particle size distribution, which is critical for achieving early strength; flotation controls the grade with respect to L.O.I.; and dewatering controls the moisture content.

Membrane filtration of textile dyehouse wastewater for technological water reuse

Polish textile industry demands big amounts of water and produces wastewater having high load of contaminants. The continued increase in the costs of chemicals, energy and water makes their recovery more important today than it was years ago when separation techniques by membrane filtration were first introduced to the textile industry. The aim of introducing membrane filtration is not only to reduce water consumption and wastewater streams. Membrane filtration also reduces the consumption of energy as the warm water can be recovered. While the filtration techniques applied for textile wastewater treatment and water recovery have been used at only few installations, these installations have been reported as successful and have been able to save enough to repay the recovery process in one to two years [1]. The paper describes the results of research works and implementation project concerning cleaner technology and water reuse in textile dyehouse. The goal of the research was application of membrane filtration to reuse water after dyeing of cotton and polyester fabrics. The Textile Research Institute in Lodz, Poland, together with the Danish partners, the Technical University of Denmark, the Institute for Product Development and RINSE has carried out this research. The research was sponsored by Danish Environmental Protection Agency DEPA. Membrane filtration has been tested in lab and pilot scale. The experiments were done with selected two membranes for nanofiltration and one for reverse osmosis. All membranes were manufactured by Desalination Systems and made of proprietary polysulphone. The lab tests investigated membrane performance using chemicals selected from real process wastewater. The pilot scale tests were done to prove membrane performance in industrial use and determine dimensioning parameters for full-scale system. The results of lab and pilot scale tests have shown that membranes can be used with the rinsing water from dyeing of cotton and polyester fabrics. As the result of the pilot scale tests two full scale systems were proposed: nanofiltration system producing permeate which can be used in limited technological processes and reverse osmosis system producing permeate of the same quality as technological water.

NOx Removal with Combined Selective Catalytic Reduction and Selective Noncatalytic Reduction: Pilot-Scale Test Results

Pilot-scale tests were conducted to develop a combined nitrogen oxide (NOx) reduction technology using both selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR). A commercially available vanadium- and titanium-based composite honeycomb catalyst and enhanced urea (NH2CONH2) were used with a natural-gas-fired furnace at a NOx concentration of 110 ppm. Changes in SNCR chemical injection temperature and stoichiometry led to varying levels of post-furnace ammonia (NH3), which acts as the reductant feed to the downstream SCR catalyst. The urea-based chemical could routinely achieve SNCR plus SCR total NOx reductions of 85 percent with less than 3 ppm NH3 slip at reductant/NOx stoichiometries ranging from about 1.5 to 2.5 and SCR space velocities of 18,000 to 32,000 h−1. This pilot-scale research has shown that SNCR and SCR can be integrated to achieve high NOx removal. SNCR provides high temperature reduction of NOx followed by further removal of NOx and minimization of NH3 slip by a significantly downsized (high-space velocity) SCR.

ADVANCED TREATMENT OF PAPER MILL EFFLUENTS BY A TWO-STAGE ACTIVATED SLUDGE PROCESS

The work presented in this paper concerns the application of a two-stage aerobic activated sludge process for treatment of effluents from paper mills in Denmark. The paper describes both pilot-scale test results and fullscale experience with the process. The treatment process is characterised by a bigh-load first stage (2-4 kg COD/kg MLSSxd) followed by a low-load second stage to secure full nitrification and denitrification of remaining nitrogen compounds. The results of continuous pilot-scale tests show that it is possible to obtain a reduction of more than 85% of the incoming COD,01 and a 99% reduction of the incoming BOD5, resulting in an effluent quality of 230 mg CODsol/l and less than 10 mg BOD5/l. As indicated, practically all the biodegradable organic substances are removed by the process. The remaining fraction of soluble organics measured as COD is considered to be non-biodegradable by conventional biological treatment systems. The results produced in the pilot-scale tests are confirmed by the effluent qualities obtained in a full-scale treatment plant at another paper mill, involving an identical process concept. During the pilot-scale tests, special attention bas been paid to the removal of organic compounds, organic nitrogen as well as nutrients and nitrification. In addition, the sludge characteristics and the oxygen requirements have been considered.

The SRRL Integrated System for Opening and Cleaning Cotton—the Carding Cleaner and the Integrated Unit

The changes made in a conventional one-process picker to convert the unit into a com mercial size Carding Cleaner are described. The results of pilot scale tests of the machine in an experimental line are compared with those of a control line composed of conven tionat textile mill equipment. The data presented show that the carding cleaner line achieved an average cleaning efficiency of about 59% at a production rate of 435 lb. hr., as compared with the control line which achieved 35% cleaning at 356 lb. hr. Lint losses are 1 3 to 12of those observed in the control line. Also presented are data obtained in preliminary tests of a tentative integrated clean ing system comprised of the SRRL Opener-Cleaner and the SRRL Carding Cleaner. Nearly 82% cleaning with a lint loss of 0.70% was achieved in the integrated system as compared w ith 52% cleaning and 1 14% lint loss for the control line.