Waste Incineration Flue Gas Research Articles

Numerical Study on Separation Performance of Cyclone Flue Used in Grate Waste Incinerator

The traditional treatment of waste incineration flue gas is mostly carried out in low temperatures, but there are some problems such as corrosion of the heating surface at high and low temperatures, re-synthesis of dioxins, and low efficiency. Therefore, it is necessary to remove the pollutants at high temperatures. For the grate waste incinerator, this study proposes an adiabatic cyclone flue arranged at the exit of the first-stage furnace of the grate waste incinerator to pre-remove the fly ash at high temperatures, so as to alleviate the abrasion and corrosion of the tail heating surface. In this paper, computational fluid dynamics (CFD) method is applied to study the performance of a cyclone flue under different structural parameters, and the comprehensive performance of the cyclone flue is evaluated by the technique for order preference by similarity to an ideal solution (TOPSIS) method. The results show that particle separation efficiency increases at first and then decreases with the increase of the vortex finder length, the vortex finder diameter, and the distance between vortex finder and gas outlet tube, while it decreases with the increase of the gas outlet tube diameter. The pressure drop increases with the increase of the vortex finder length, and the vortex finder diameter, while decreases with the increase of the distance between the vortex finder, the gas outlet tube, and the gas outlet tube diameter. In the scope of this study, when h1/a = 1.1, D1/A = 0.33, h2/A = 1.5, and D2/A = 0.50, the comprehensive performance of the cyclone flue is much better.

A sulfur-resistant CuS-modified active coke for mercury removal from municipal solid waste incineration flue gas.

Adsorption is a typical method for air pollutant removal from flue gas. A CuS-modified active coke (CuS/AC) sorbent was developed to improve the elemental mercury removal efficiency from municipal solid waste incineration (MSWI) flue gas. The influences of the loading amount of CuS, reaction temperature, and flue gas components including O2, SO2, H2O, and HCl on Hg0 removal efficiency were investigated, respectively. The results showed that the mercury adsorption capacity of CuS/AC(20%) sorbent was about 7.17 mg/g with 50% breakthrough threshold, which is much higher than that of virgin active coke. The analysis of XPS indicated that HgS was the main species of mercury on spent CuS/AC, which implied that adsorption and oxidation were both included in Hg0 removal. S22- played a vital role in the oxidation of physically adsorbed Hg0. Meanwhile, the common components of MSWI flue gas exhibited no significant inhibition effect on Hg0 removal by CuS/AC sorbent. CuS/AC sorbent is a promising sorbent for the mercury removal from MSWI flue gas.

Assessment of cation chemistry of groundwater near hospital wastes dumpsites in Umuahia Nigeria using multivariate and analytical index approach

Abstract This study looked at the effects of hospital waste dumpsite on the water quality of selected boreholes near a hospital located in a densely populated area in South Eastern Nigeria. Multivariate and Index analytical approaches were used to differentiate and group the influence of hospital wastes on cations in groundwater resources in the study area. Results revealed significant concentrations of cations: Zn 2 + , Mn 2 + , Cr2＋ and Cd 2 + in the selected boreholes at P>0.05 level of significance. The mean cations (mg/l) ranged between 2.15 ± 0.09; 2.72 ± 0.05; 4.20 ± 0.00; 1.15 ± 0.00; 0.014 ± 0.00; 0.56 ± 0.00 for Cu 2 + , Zn 2 + , Mn 2 + , Cr2＋ , Cd 2 + , and Pb 2 + , respectively. Distribution pattern of mean values of cations in the selected boreholes were in decreasing order : Mn 2 + > Zn 2 + > Cu 2 + > Cr2＋ > Pb 2 + > Cd 2 + . The mean values of Cu 2+ Cd 2 + , Mn 2 + , and Cr2＋ were above the WHO standard for drinking water in boreholes. Significant correlations existed between Zn 2 + and Cu 2 + , Pb 2 + and Mn 2 + , Pb 2 + and Cr2＋, Cd 2 + and Zn 2 + and Cr2＋ and Mn 2 + in boreholes. On, principal component analysis (PCA), factor 1 was positively loaded with Cd 2 + , and Zn 2 + originating from hospital waste dumpsite and incinerator flue gas, while factor 2 with negatively loaded Cd 2 + and Zn 2 + originated from basement complex. Contamination index (CPI) indicated that cations in boreholes varied between slight to severely contaminated status. Geo-accumulation (Igeo) of cations of sampled water varied between uncontaminated to moderately contaminated status.

Environmental and economic performance assessment of alternative acid gas removal technologies for waste-to-energy plants

Removal of acid pollutants (HCl and SO2) is an important stage in waste incineration flue gas cleaning. Several technological options for acid gas neutralisation are currently available in order to comply with the increasingly stringent emission limit values and the choice of the best solution for a specific plant should be based on the economic and environmental considerations implied in the concept of Best Available Technique.The present study analyses and compares state-of-the-art dry, semi-dry and wet process configurations for acid gas removal in waste-to-energy plants. The performance of five representative process schemes was analysed: the streams associated with acid gas emission control were quantified via mass and energy balances and a life cycle perspective was applied in order to evaluate the inputs and outputs of the supply and disposal chains. The analysis pinpoints the key issues in terms of environmental and economic performance of the presented alternatives. Benefits and limits of the alternative technologies are discussed in view of different waste composition. The energy penalty associated with flue gas reheat appears to be the main environmental drawback of wet methods, while the main contribution to the environmental footprint of dry methods is given by the production of solid reactants. Multi-stage treatment systems systematically show lower environmental impacts than the single stage counterparts, but their cost-effectiveness is limited by the disposal cost for the generated solid residues. The provided insights can contribute to a more effective implementation of the strategies of circular economy and cleaner production in the operation of a waste-to-energy plant.

Simulation on deacidification performance of waste incinerator flue gas by rotating spray drying

The models describing the mass transfer and chemical reaction of flue-gas−slurry drops in the deacidification tower of waste incineration plants are established. The internal dynamics are simulated and the effects of flue-gas inlet velocity, stoichiometric ratio, drop size and water spray rate, on deacidification performance, are evaluated. Results show that simulated desulphurisation and dechlorination rates are 58.97% and 99.99% and the removal rate of HCl is greater than SO2. A high-temperature zone is found in the upper part of central axis, whereas low-temperature zones are observed at the right wall and bottom. Flow field is characterized with complex recirculation zones, wherein the recirculation zone emerged on the upper-right entrains a small part of drops towards the right wall. Approximately 60% of the total removal amount of SO2 and 90% of HCl are absorbed in the upper part. Slurry drops completely evaporate in 5 s after entering the deacidification tower. The deacidification performance is improved with the increase in stoichiometric ratio and water spray rate, as well as the decrease in inlet gas velocity and drop size. Excellent deacidification performance is expected under flue-gas inlet velocity of 7.1 m/s, drop size of 50–70 μm, and water spray rate of 600 L/h.

Adsorption of Dioxin by Bag Filter + Powdered Activated Carbon

A novel bag filter + powdered activated carbon technique is here proposed to address the low utilization rate of powdered activated carbon and the low dioxin removal rate associated with the conventional activated carbon injection + bag filter technique, better known as the fly ash + activated carbon + bag technique. In this method, dibenzofuran serves as a dioxin simulant. The effect of the adsorption temperature and dibenzofuran inlet concentration on the adsorption performance of activated carbon was studied using a filter cloth adsorption device with an inner diameter of 25 mm, and the adsorption performances of fly ash, activated carbon, and fly ash +5% activated carbon were compared. The results showed that activated carbon exhibited a higher adsorption efficiency and remained highly efficient longer than fly ash +5% activated carbon. When the dibenzofuran inlet concentration was 0.0956 g/m3 (about one million times the concentration of dioxin in the flue gas of incinerated waste), the duration of the high-efficiency (>90%) adsorption of the powdered activated carbon (thickness 1.2 mm) on the filter cloth was over 7 h. These results prove that the replacement of fly ash + activated carbon + filter bag with powdered activated carbon + bag filter can significantly improve the removal efficiency of the dioxin in waste incineration flue gas and the utilization rate of activated carbon.

Calcium and organic matter removal by carbonation process with waste incineration flue gas towards improvement of leachate biotreatment performance

Municipal solid wastes incineration (MSWI) flue gas was employed as the carbon source for in-situ calcium removal from MSWI leachate. Calcium removal efficiency was 95–97% with pH of 10.0–11.0 over 100min of flue gas aeration, with both bound Ca and free Ca being removed effectively. The fluorescence intensity of tryptophan, protein-like and humic acid-like compounds increased after carbonation process. The decrease of bound Ca with the increase of precipitate indicated that calcium was mainly converted to calcium carbonate precipitate. It suggested that the interaction between dissolved organic matter and Ca2+ was weakened. Moreover, 10–16% of chemical oxygen demand removal and the decrease of ultraviolet absorption at 254nm indicated that some organics, especially aromatic compound decreased via adsorption onto the surface of calcium carbonate. The results indicate that introduce of waste incineration flue gas could be a feasible way for calcium removal from leachate.

HCl removal characteristics of calcium hydroxide at the dry-type sorbent reaction accelerator using municipal waste incinerator flue gas at a real site

A dry-type reactor was used to reduce the HCl emitted from a municipal waste incinerator. A real-scale reactor was installed downstream of the existing semi-dry reactor (SDR) as part of D local incineration plant, whose HCl removal efficiency was investigated by applying calcium hydroxide (Ca(OH)2). A test dry-type sorbent reaction accelerator (SRx) was designed, and the stoichiometric ratio (SR) of the sorbent and the secondary reaction characteristics of unreacted Ca(OH)2 in a baghouse were analyzed. For the results, the SRx showed higher HCl removal efficiency and more economic benefits than the other existing flue gas treatment facilities of the incinerator plant. Furthermore, the highest reduction efficiency of HCl was obtained when the differential pressure in the baghouse was maintained at 150mmH2O. This is because as the unreacted sorbent attached to the filter surface layer became thicker and the secondary reaction of the HCl removal increased.

Pilot-scale evaluation of a novel TiO2-supported V2O5 catalyst for DeNOx at low temperatures at a waste incinerator

The removal of NOx by catalytic technology at low temperatures is significant for treatment of flue gas in waste incineration plants, especially at temperatures below 200°C. A novel highly active TiO2-supported vanadium oxide catalyst at low temperatures (200–250°C) has been developed for the selective catalytic reduction (SCR) de-NOx process with ammonia. The catalyst was evaluated in a pilot-scale equipment, and the results were compared with those obtained in our previous work using laboratory scale (small volume test) equipment as well as bench-scale laboratory equipment. In the present work, we have performed our experiments in pilot scale equipment using a part of effluent flue gas that was obtained from flue gas cleaning equipment in a full-scale waste incineration plant in South Korea. Based on our previous work, we have prepared a TiO2-supported V2O5 catalyst coated (with a loading of 7wt% of impregnated V2O5) on a honeycomb cordierite monolith to remove NOx from a waste incinerator flue gas at low temperatures. The NOx (nitrogen oxides) removal efficiency of the SCR catalyst bed was measured in a catalyst fixed-bed reactor (flow rate: 100m3h−1) using real exhaust gas from the waste incinerator. The experimental results showed that the V2O5/TiO2 SCR catalyst exhibited good DeNOx performance (over 98% conversion at an operating temperature of 300°C, 95% at 250°C, and 70% at 200°C), and was much better than the performance of commercial SCR catalysts (as low as 55% conversion at 250°C) under the same operating conditions.

Removal and speciation of mercury compounds in flue gas from a waste incinerator

ABSTRACTThe management and control of mercury emissions from waste incinerators have become more significant, because waste incinerators are sinks to treat mercury-containing consumer products. This study investigated the effects of mercury concentrations and waste incineration temperatures on mercury speciation using a lab-scale experimental instrument. The removal characteristics of different mercury species were also investigated using an apparatus to simulate the fabric filter with a thin layer of additives such as Ca(OH)2 and NaHCO3, activated carbon (AC), and fly ash. HgCl2 generation rates peaked at 800°C for initial Hg0 concentrations of 0.08−3.61 mg/Nm3 in the presence of 400 ppm HCl. A linear relationship was established between the generation rate of HgCl2 and the logarithmic value of initial mercury concentration. Fly ash proved highly efficient in mercury removal, being equal or superior to AC. On the other hand, Ca(OH)2 and NaHCO3 were shown to have no effects on mercury removal. In the dry-scrubbing process, alkali agent is often sprayed in amounts beyond those stoichiometrically required to aid acidic gas removal. The research suggests, however, that this may hinder mercury removal from the flue gas of solid waste incinerators.

Role of surface vanadium oxide coverage support on titania for the simultaneous removal of o-dichlorobenzene and NOx from waste incinerator flue gas

The catalytic activity of VOx species supported on TiO2 was investigated in the simultaneous destruction of NO and 1,2-dichlorobenzene (o-DCB), as typical pollutants molecules in the off-gases from municipal waste incinerator (MWI) plants. Catalysts with different vanadium loading were prepared in order to obtain different VOx species and characterized by ICP-AES, XPS, N2 adsorption at −196°C, XRD, H2-TPR, Raman and UV–vis–NIR DRS spectroscopy. The characterization results show that molecularly dispersed isolated and polymeric vanadia species form below the dispersion limit loading (“monolayer coverage”), while crystalline species form above it. We used moderate HNO3 treatment to partially leach vanadium oxide species, creating a series of catalysts with variable vanadia loading. The catalytic activity of the VOx/TiO2 catalyst shows that it is able to catalyze the destruction of both pollutants, although higher temperature is required for o-DCB oxidation than for NO reduction. Surface vanadia coverage has a clear effect on TOF and activation energy values, which underline that isolated vanadia species are more efficient for o-DCB oxidation, while the polymeric ones are more efficient for NO reduction.

Pilot Plant Studies for CO2Capture from Waste Incinerator Flue Gas Using MEA Based Solvent

Experimental study of carbon dioxide (CO2 ) capture from waste incinerator flue gas is presented. A specific pilot plant has been achieved based on absorption/desorption process using MonoEthanolAmine (MEA) solvent. Several experiments have been carried out at laboratory and industrial site. The pilot is fully instrumented to establish precise balances. Laboratory experiments allow to measure overall mass transfer coefficient K G a w for several pilot operating conditions. Long laboratory and industrial runs provide an estimation of MEA chemical resistance against waste incinerator flue gas. The experiments also allowed the analysis of NO2 and SO2 absorption through the solvent as well as the accumulation of Heat Stable Salts (HSS) for a full scale CO2 capture unit fed by a waste incinerator flue gas.

Memory Effects of Polychlorinated Dibenzo-p-dioxin and Furan Emissions in a Laboratory Waste Incinerator

Laboratory wastes are discharged from experimental, testing, or analysis processes, and contain various toxic chemical compounds with a high heating-value and a high chlorine content (＞ 9%). Elevated PCDD/F (polychlorinated dibenzo-pdioxin and furan) emissions during start-up stages are caused by combustion of waste with high chlorine contents, incomplete combustion, and so called ”memory effects”. Even though the duration of cold start-up is short compared with the hours of continuous steady operation in a waste incinerator, its negative effects with regard to PCDD/F emissions on both human health and the environment cannot be neglected. A full-scale laboratory-waste incinerator which is operated for 10 days in each run and has 15 to 20 runs annually was investigated in this study. Eleven PCDD/F samples of stack flue gas were collected during the cold start-up periods (for 60.5 hrs). The gas temperature of the primary combustion chamber was above 850°C, and was maintained at between 850 and 900°C by injecting diesel fuel without waste feed. For first 1.5-7.5 hours, the PCDD/F concentration in the stack flue gas was as high as 0.656-1.15 ng I-TEQ/Nm^3. Afterward, during hours 10.5-35.5 and 54.5-60.5, this reduced to 0.159-0.459 and 0.218-0.254 ng I-TEQ/Nm^3, respectively. Based on principal component analysis (PCA) and the L/H ratio, the results revealed a higher L/H ratio (1.23) before hour 32, indicating that less chlorinated PCDD/F homologues (tetra and penta) dominated, while after hour 32 more chlorinated PCDD/F homologues (hexa, hepta and Octa) had a higher mass concentration and the L/H ratio fell to 0.42. These results indicate that the PCDD/F emissions during cold start-up were caused by memory effects and thermal desorption. Therefore, in order to reduce the PCDD/F emissions from the stack flue gas of waste incinerators, is highly recommended that a higher amount of activated carbon injection is used in front of the bag filters.

Study on the decomposition of trace benzene over V2O5–WO3/TiO2-based catalysts in simulated flue gas

Catalytic decomposition of benzene was studied by using oxides of vanadium and tungsten supported on titanium oxide (TiO2) catalysts for effective reduction of emissions of toxic organic compounds from waste incineration. Experiments were conducted to evaluate the effects of the catalyst's composition, and operating conditions on benzene decomposition, and the relationship between molecular structures of catalysts and their activity was also investigated through replacing the conventional TiO2 catalyst support by nano-sized TiO2. Trace levels (1 and 10ppm) of gaseous benzene were catalytically decomposed in a fixed-bed catalytic reactor with monolithic oxides of vanadium and tungsten supported on titanium oxide (V2O5–WO3/TiO2) catalysts under conditions simulating the cooling of waste incineration flue gas. On-line monitoring of trace benzene concentrations before and after the catalyst was achieved by means of resonance enhanced multiphoton ionization-time of flight mass spectrometry (REMPI-TOFMS). Catalysts were characterized by nitrogen adsorption, X-ray diffraction, energy dispersive X-ray spectroscopy, temperature-programmed reduction, and Raman spectroscopy. The effects of several parameters, including catalyst operating temperature, space velocity (SV) and initial benzene concentration, on catalytic oxidation of benzene were investigated. Experimental results indicate that reduction of the initial benzene concentration from 10 to 1ppm either enhances or decreases the catalytic removal efficiency depending on the adsorption capability as well as the oxidation ability of the catalyst tested. The catalytic activity for benzene oxidation not simply relies on the vanadium content of the catalyst; the molecular structure of vanadium oxide, which is known to be influenced by both vanadium oxide loading and the type of support, is very important. Nano-sized TiO2 supported vanadium oxide catalyst (VWNT) with lowest V loading (0.75wt.%) provides higher catalytic activity than those of the catalysts with higher V contents (1.31 and 2.92wt.%) but supported by conventional TiO2 (VWT1 and VWT2). The relatively higher catalytic activity of VWNT may be attributed to: (a) the presence of monomeric VOx species, with one terminal VO bond as indicated by Raman spectra; (b) fewer impurities confounding active catalytic constituents (V, W and Ti); (c) pure anatase phase of TiO2 rather than a mixture phase of anatase and rutile servicing as catalyst support besides its nano-scale particle size; (d) larger specific surface area, smaller average pore diameter, and narrower pore size distribution contribute higher adsorption ability for benzene. No obvious competition effect between NOx removal and benzene oxidation was observed in this study. Reaction rate constants and activation energies for benzene catalytic oxidation tested by the catalysts were calculated. Lower activation energy obtained from VWNT than those of the two catalysts further confirming the higher catalytic activity of VWNT.

Activated carbon production from RDF and its use for dioxin removal from flue gas of waste incinerators

Aims: The aims of this study were to produce activated carbon from refuse derived fuel (RDF) and to examine its efficiency in dioxins and furans (PCDD/F) removal for application in the adsorptive processes of waste incineration. Materials and Methods: In the present study the RDF was carbonized at 600°C to produce char and the char was then steam activated at 900°C to generate activated carbon (AC). The efficiency of the produced AC in PCDD/F removal from simulated flue gas was investigated using a bench scale static-bed reactor. Experiments were conducted under flue gas stream at 275°C using a standard flyash (BCR-490) as a source of PCDD/F. The PCDD/F content of the exhaust gas was trapped by XAD-II resin, and after extraction and clean-up processes, were analyzed using a GC coupled with a triple quadrupole mass spectrophotometer (MS). Results: The results showed an overall reduction of 85% and 43% in the flue gas concentration of PCDD and PCDF, respectively, which compared favourably with a commercial AC. In addition, reduction was varied throughout the congener groups of these compounds. Conclusions: The AC derived from the pyrolysis of RDF therefore shows potential as a control material for dioxins and furans in waste combustion process.

Activated carbon treatment of municipal solid waste incineration flue gas

Activated carbon injection is widely used to control dioxins and mercury emissions. Surprisingly little attention has been paid to its modelling. This paper proposes an expansion of the classical Everaerts-Baeyens model, introducing the expression of fraction of free adsorption sites, f (s), and asserting the significant contribution of fly ash to dioxins removal. Moreover, the model monitors dioxins partitioning between vapour and particulate phase, as well as removal efficiency for each congener separately. The effects of the principal parameters affecting adsorption are analysed according to a semi-analytical, semi-empirical model. These parameters include temperature, contact time during entrained-flow, characteristics (grain-size, pore structure, specific surface area) and dosage of activated carbon, lignite cokes or mineral adsorbent, fly ash characteristics and concentration, and type of incinerator plant.

Research on Flue Gas Cleaning of Waste Incineration by Rotating Spray Drying

An experimental system of rotating spray drying for cleaning the waste incineration flue gas has been set up on account of the particular fact, that the flue gas quantity is small and contains relatively little SO2,but relatively much HCl. The influence, of the main parameters which could be control during design and operation, on the efficiency of desulphurization and dechlorination has been tested determined. It was showed that this method resulted in higher dechlorination efficiency and lower desulphurization efficiency. Nevertheless, considering the particularities of the waste incineration flue gas, the discharged flue gas which had been cleaned by this method can meet the restrictive demands of discharging standard of SO2, and at the same time can warrant a higher efficiency of dechlorination. The efficiency of flue gas cleaning can be enhanced by increasing stoichiometric ratio, by injecting more water, by increasing the rotating speed of atomizer and by decreasing flue gas velocity. The efficiency of desulphurization and dechlorination could reach 78％ and 90％ at stoichiometric ratio 1.8, the amount of injection water 15L/h, rotating speed of atomizer 13500r/min and flue gas velocity 0.7m/s.

Effectiveness of operation of sewerage system of mobile complex of thermocatalytic waste treatment

The design and functionality of basic units of a mobile waste processing complex of MPK type is described. Experimental data on the catalytic purification of gases are presented. It is determined that concentrations of toxic compounds in waste incineration flue gas of the MPK complex are much smaller than the values allowed by regulations for emissions.

Polychlorinated Biphenyl Congeners in River Sediments: Distribution and Source Identification Using Multivariate Factor Analysis

To assess the level of polychlorinated biphenyl (PCB) contamination and identify their sources, surface sediments were collected from selected locations along Nakdong River, Korea, and analyzed for 209 PCB congeners using high-resolution gas chromatography/high-resolution mass spectroscopy. PCB levels ranged from 0.124 to 79.2ng/g dry weight (coplanar PCBs 0.295 to 5720pg/g dry), which were similar to those of three other major rivers (Han, Geum, and Youngsan rivers) in Korea but slightly lower than those in neighboring countries. Regarding homologue composition, tetra-CBs were most abundant in most samples, but some samples with much higher PCBs concentrations had relatively lower proportions of tetra-CBs and higher proportions of penta- to hepta-CBs. To identify the sources of PCBs in sediment samples, principal component analysis/absolute principal component scores (PCA/APCS), positive matrix factorization (PMF), and multiple linear regression (MLR) were used with the congener composition of aroclors (1242, 1248, 1254, and 1260) and the flue gas of waste incinerators (data obtained from a previous article) as source profiles. Results showed that the three models showed similar source apportionments. Most sediment samples with lower PCB concentrations had higher proportions of incineration-derived materials, and some sediment samples with much higher PCB concentrations had higher proportions of aroclor 1260. This occurred because many industrial facilities, such as landfill leachate-treatment facilities, were gathered around sampling points with high PCB concentrations, and high-chlorinated PCBs are more stable in the elution process of landfill leachate than the incineration process. PCB concentrations estimated by APCS, PMF, and MLR were similar to the measured values with coefficients of determination ranging from 0.77 to 0.99.

Effects of Na, Cu, Ni and Co Modifications on the Activity and Characteristics of Rh/Al2O3 Catalysts for NO Reduction

This study used different metals to modify Rh/Al2O3 catalysts for NO reduction in a simulated waste incineration flue gas containing 6% O2. The characteristics of the modified catalysts were analyzed using BET, TEM and XRD. The results of the experiment reveal that Na addition can significantly affect the properties of Rh/Al2O3 catalysts on the BET surface area and Rh metal dispersion. Furthermore, Na addition was found to significantly enhance the NO conversion of Rh/Al2O3 at 250–350 °C. On the contrary, Cu, Ni, and Co addition was found to have slight suppression effects.