Low NOx,High Efficiency Multistaged Burner: Fuel Oil Results

A multistaged combustion burner designed for in-furnace NO_x control and high combustion efficiency is being evaluated for high nitrogen content fuel and waste incineration application in a 0.6 MW package boiler simulator. A low NO_x precombustion chamber burner has been reduced in size by approximately a factor of two (from 600 to 250 ms first-stage residence time) and coupled with (1) air staging, resulting in a three-stage configuration, and (2) natural gas fuel staging, yielding up to four stolchlometric zones. Natural gas, doped with ammonia to yield a 5.8 percent fuel nitrogen content, and distillate fuel oil, doped with pyridine to yield a 2 percent fuel nitrogen content, were used to simulate high nitrogen content fuel/waste mixtures. The multistaged burner reduced NO emissions by 85 percent from emission levels from a conventional unstaged burner mounted on a commercial package bollerTA minimum NO emission level of 110 ppm was achieved in the fuel oil tests, from a level of 765 ppm for conventional firing. This is compared with a 160 ppm minimum NO level achieved in gaseous fuel tests, from an uncontrolled level of 1000 ppm. Boiler fuel staging, or reburnlng, appears to be superior to air staging for high combustion efficiency due to its minimal fuel-rich core and second flame front in the boiler.     

Post-combustion syntheses of PCDD/F and PBDD/F from halogen-rich fuel is suppressed by a pebble heater technology

GOAL, SCOPE AND BACKGROUND: Changes in German and European legislation shifted processing of polymer-rich shredding residues (SR) from landfill to thermal treatment. However, when waste of electric and electronic equipment (WEEE) is the source of SR, thermal treatment is complicated by halogens as well as the presence of polybrominated dioxins and furans (PBDD/F) and brominated flame retardants (BFR). Hence, WEEE requires high temperature incineration with sufficient residence times. Post-combustion synthesis of polyhalogenated dioxins and furans (PXDD/F) is dominant in the temperature range between 250-450 degrees C. Thus, a very rapid gas cooling from 450 degrees to 250 degrees C is important for proper raw gas treatment. The pebble heater technology developed by ATZ Entwicklungszentrum (Sulzbach-Rosenberg, Germany) might serve as an alternative to the state-of-the-art quench cooling. It is based on the application of a pebble bed of natural bulk material, which the exhaust gases flows through radially. It provides an excellent heat transfer and a temperature gradient in the range of 1,500-2,000 K/m. The paper presents data of a pilot application of the pebble heater technology for the treatment of raw gas derived from the incineration of polymeric materials from WEEE. METHODS: A liquid fuel was chosen in order to minimise technical modifications of the plant. It was analysed for halogens by x-ray fluorescence, for brominated flame retardants by HPLC-UV/MS and for PXDD/F by GC-HRMS. Combustion gases were rapidly cooled down to temperatures below 200 degrees C and emissions of PBDD/F and PCDD/ F were estimated without further off-gas treatment. PBDD/F emissions were computed as PCDD/F toxicity equivalents applying two different calculation approaches. RESULTS AND DISCUSSION: PCDD/F emissions accounted for 0.04 ng I-TEQ/Nm3 and are in compliance with European emission limits. Calculated PBDD/F toxicity equivalents exceeded the emission limit of 0.1 ng I-TEQ/Nm3 by factors of 75 and 208 depending on the calculation approach. A mass balance of PBDD/F and PCDD/F congeners revealed an efficient elimination of more than 95% in most cases. Lower reduction rates (76% for 2,3,7,8-TeBDF and 82% for 1,2,3,7,8-PeBDF) were attributed to incomplete combustion. An intended recovery of halogens by one-stage scrubbing downstream of the pebble heater was ineffective, recovering 28% of the applied chlorine and 9% of the bromine, only. CONCLUSIONS: Our pilot incineration test indicates that the pebble heater technology can effectively suppress a post-combustion synthesis of PCDD/F and PBDD/F, resulting in low PCDD/F emission levels without further off-gas treatment. The presented data state that WEEE is sensible to incomplete combustion, which will lead to increased PBDD/F emissions without increasing PCDD/F emission limits. This finding is especially relevant for small and low-technical incineration appliances, which have been reported to treat WEEE in developing countries and are considered to serve as a significant source of PXDD/F these days. RECOMMENDATIONS AND PERSPECTIVES: Monitoring of PCDD/F emissions only might considerably underestimate the total emission of dioxins and dioxin-like compounds. It is therefore an ineffective means for assessing resulting health risks, at least for those waste treatment plants which are considered to handle the increasing amounts of PBDD/ F-containing polymers from WEEE in future. Consequently, it is recommended to initiate a screening programme for PXDD/F emissions in large scale incineration facilities which are capable of treating WEEE shredder residues.     

Metal partitioning in products of incineration of municipal solid waste

Metals contained in the waste transfer to the waste incineration products, including flue gas, fly ash, and bottom ash, as different oxide, nitride, carbides, and other phases. Most of the metal-based phases formed in incineration are toxic and their emissions need to be strictly controlled. Therefore, behavior of metal species during incineration must be well understood. Such understanding is possible based on the experimental identification of the metal phases formed in the waste combustion and determination of their concentration in various incineration products. To avoid well-known experimental difficulties of the industrial waste incinerators associated with the poor fuel/conditions reproducibility and limited instrumentation, a 140,000 Btu/h pilot-scale, laboratory burner was constructed, characterized and operated at NJIT. A synthetic fuel representative of the municipal solid waste in the US was formulated and produced in 600-Lb batches. The solid fuel contained Fe and SiO2 as main constituents, and was doped with trace amounts of Al, Ni, Cr, Hg and PbO. Several experiments have been conducted on combustion of the synthetic fuel in the pilot-scale incinerator with varying fuel-air equivalence ratio. Both gaseous and condensed combustion products were sampled and analyzed. Atomic absorption spectroscopy and X-ray diffraction were used to analyze total metal contents and metal containing phases in the incineration products. Thermodynamic equilibrium computations were performed to obtain the adiabatic flame temperature and identify the phases of the metal-containing products formed at the equilibrium conditions. The results of the equilibrium computations performed at the varied fuel/air ratios were compared with the observed experimental results.     

城市下水污泥焚烧过程中二次污染物排放特性的试验研究

在0.15 MWt循环流化床燃烧试验台上进行了城市下水污泥与煤的混烧试验,分析了烟气中的二次污染物排放特性.分析结果表明,利用循环流化床焚烧城市下水污泥时,添加辅助燃料(如煤)及改变焚烧条件,不仅可以达到稳定燃烧的目的,而且有利于抑制焚烧中二次污染物(如CO及二恶英等有机污染物)的生成.分析了焚烧污泥污染物的排放特性,为采用焚烧方式处理城市下水污泥提供了基础性试验数据.     

城市下水污泥焚烧过程中二次污染物排放特性的试验研究

在0．15MWt循环流化床燃烧试验台上进行了城市下水污泥与煤的混烧试验，分析了烟气中的二次污染物排放特性。分析结果表明，利用循环流化床焚烧城市下水污泥时，添加辅助燃料（如煤）及改变焚烧条件，不仅可以达到稳定燃烧的目的，而且有利于抑制焚烧中二次污染物（如CO及二恶英等有机污染物）的生成。分析了焚烧污泥污染物的排放特性。为采用焚烧方式处理城市下水污泥提供了基础性试验数据。     

Boiler briquette coal versus raw coal: Part II--Energy, greenhouse gas, and air quality implications

The objective of this paper is to conduct an integrated analysis of the energy, greenhouse gas, and air quality impacts of a new type of boiler briquette coal (BB-coal) in contrast to those of the raw coal from which the BB-coal was formulated (R-coal). The analysis is based on the source emissions data and other relevant data collected in the present study and employs approaches including the construction of carbon, energy, and sulfur balances. The results show that replacing R-coal with BB-coal as the fuel for boilers such as the one tested would have multiple benefits, including a 37% increase in boiler thermal efficiency, a 25% reduction in fuel demand, a 26% reduction in CO2 emission, a 17% reduction in CO emission, a 63% reduction in SO2 emission, a 97% reduction in fly ash and fly ash carbon emission, a 22% reduction in PM2.5 mass emission, and a 30% reduction in total emission of five toxic hazardous air pollutant (HAP) metals contained in PM10. These benefits can be achieved with no changes in boiler hardware and with a relatively small amount of tradeoffs: a 30% increase in PM10 mass emission and a 9-16% increase in fuel cost.     

Boiler Briquette Coal versus Raw Coal: Part II—Energy,Greenhouse Gas,and Air Quality Implications

ABSTRACT

The objective of this paper is to conduct an integrated analysis of the energy, greenhouse gas, and air quality impacts of a new type of boiler briquette coal (BB-coal) in contrast to those of the raw coal from which the BB-coal was formulated (R-coal). The analysis is based on the source emissions data and other relevant data collected in the present study and employs approaches including the construction of carbon, energy, and sulfur balances. The results show that replacing R-coal with BB-coal as the fuel for boilers such as the one tested would have multiple benefits, including a 37% increase in boiler thermal efficiency, a 25% reduction in fuel demand, a 26% reduction in CO₂ emission, a 17% reduction in CO emission, a 63% reduction in SO₂ emission, a 97% reduction in fly ash and fly ash carbon emission, a 22% reduction in PM_2.5 mass emission, and a 30% reduction in total emission of five toxic hazardous air pollutant (HAP) metals contained in PM₁₀. These benefits can be achieved with no changes in boiler hardware and with a relatively small amount of tradeoffs: a 30% increase in PM₁₀ mass emission and a 9–16% increase in fuel cost.     

Mass Burn Incineration with a Presorted MSW Fuel

This research, supported by the U.S. Dept. of Energy, investigates potential benefits to mass burn incineration from burning a presorted MSW fuel. Comparative boiler efficiency tests at three mass burn incineration sites utilizing as-received MSW and a presorted MSW fuel are reported. Test results indicate that waste presorting can provide substantial benefits to the mass burn process. Flue gas and ash heavy metals are found to be significantly reduced. Discarded automobile batteries are found to substantially contribute to lead levels in the waste stream. Reductions in emissions of CO, HC, HC1, HF, and NO_X are reported. Increases in facility boiler efficiency and MSW disposal capacity are measured.     

Field Testing and Computer Modeling of an Oxygen Combustion System at the EPA Mobile Incinerator

The LINDE® Oxygen Combustion System has been demonstrated successfully at the EPA Denney Farm site as part of the modified EPA mobile incinerator. This paper describes the field testing results and computer modeling of the LINDE system. The oxygen system enables the EPA unit to incinerate dioxin and PCB contaminated soil at a consistent rate of 4000 lb/h—200 percent of the original maximum capacity. The pure oxygen combustion system improved the thermal efficiency of the incinerator by over 60 percent and reduced the flue gas volume dramatically. Therefore, the dust carryover problem was mitigated. The destruction and removal efficiencies of hazardous wastes exceeded EPA requirements.

The design of the proprietary burner allows the use of up to 100 percent oxygen in place of air for incineration with improvements over conventional oxy-fuel burners. As a result, the temperature distributions in the rotary kiln are uniform and NO_x emissions are low.

The oxygen combustion system, controlled by a programmable controller, provided much better response and flexibility than conventional air based systems. The system generated a stable flame and responsed well to the transient conditions of the rotary kiln. Kiln puff occurrence was virtually eliminated in the operation of the mobile incinerator.

A computer model of the incinerator was developed and used for the process design of the LINDE system. The model predicted the test results reasonably well. This model can be a useful tool in the design and operation of rotary kiln incineration systems.     

Effect of liquid inhibitors on PCDD/F formation. Prediction of particle-phase PCDD/F concentrations using PLS modelling with gas-phase chlorophenol concentrations as independent variables

Emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) from municipal waste incineration are currently a subject of considerable public concern because of their extreme toxicity. PCDD/F formation in incineration processes is being studied widely, but little work has been done on their inhibition. We studied the effect of two liquid inhibitors, sodium ammonium hydrogen phosphate (NAHF) and urea (H2NCONH2), on PCDD/F formation in the combustion of liquid fuel doped with copper and chlorine using a pilot-scale plant. The inhibitors were injected into the flue gas stream at a temperature of 725 degrees C, whereupon both the chlorophenol and PCDD/F concentrations decreased. Particle-phase PCDD/F concentrations in particular decreased by up to 90% with NAHF and 70% with urea, but gas phase reduction took place only with urea. The results suggest that the formation of PCDD/Fs is hindered in the particle phase at the early stages of the PCDD/F formation chain, probably even before precursors such as chlorophenols have been formed. As a consequence, particle-phase PCDD/F concentrations can be predicted by a PLS (partial least-squares) approach with the gas-phase chlorophenol concentrations as independent variables. The structure and partial charges of Cu(+)-urea complex were calculated by the HF/3-21G basis set.     

Bromine in waste incineration partitioning and influence on metal volatilisation

INTENTION, GOAL, SCOPE, BACKGROUND: The halogen bromine is far less abundant than chlorine, but it can be found at high concentrations in special materials like flame retarded plastics. The fate and effects of Br in waste incineration are not well understood. It may have similar implications like Cl for the volatilisation of heavy metals and the formation of low volatile organic compounds. Due to its lower oxidation potential, there is a risk of formation of elementary Br2 in the offgas. OBJECTIVE: Co-combustion tests of different types of Br containing plastic waste materials (up to 22%) and MSW in the TAMARA pilot plant for waste incineration were conducted to investigate the Br partitioning and the influence of Br on metal volatilisation. METHODS: The Br inventory of the fuel mix was elevated to approx. 1 wt-%. All input and output mass flows of the furnace have been sampled and the partitioning of Cl, Br, S, and a number of heavy metals, has been calculated on the basis of closed mass balances. RESULTS AND DISCUSSION: Organically-bound Br was typically released to more than 90% into the raw gas. Elementary Br2 was detected at high Br levels. Its presence was always analysed when all SO2 in the raw gas was oxidised to SO3. Br enhances the volatilisation of metals like K, Zn, Cd, Sn, Sb, and Pb out of the fuel bed principally in the same way as Cl. The tests gave strong indication that the promoting influence of the halogens on metal volatilisation is more pronounced than that of the fuel bed temperature. The volatilised metals are condensated on the fly ashes and are discharged along with the filter ashes. CONCLUSIONS: As long as a surplus of SO2 is present in the raw gas no Br2 is formed. Although the halogen induced transfer out of the fuel bed causes high concentrations of volatile metals in the filter ashes, a recovery is not economically feasible for the time being. The volatilisation gives no rise to metal emission problems as long as efficient dedusting is achieved. RECOMMENDATION AND OUTLOOK: If there is a risk of Br2 formation, in wet scrubbing a reducing agent has to be added to the neutral scrubber for efficient abatement. Filter ashes should be disposed of in a way that enables access for recovery in the future. The exact volatilisation characteristics of the various metals have to be studied in future using specifically tailored experiments.     

Reduction in greenhouse gas emissions from sludge biodrying instead of heat drying combined with mono-incineration in China

Sludge is an important source of greenhouse gas (GHG) emissions, both in the form of direct process emissions and as a result of indirect carbon-derived energy consumption during processing. In this study, the carbon budgets of two sludge disposal processes at two well-known sludge disposal sites in China (for biodrying and heat-drying pretreatments, both followed by mono-incineration) were quantified and compared. Total GHG emissions from heat drying combined with mono-incineration was 0.1731 tCO₂e t^?1, while 0.0882 tCO₂e t^?1 was emitted from biodrying combined with mono-incineration. Based on these findings, a significant reduction (approximately 50%) in total GHG emissions was obtained by biodrying instead of heat drying prior to sludge incineration.

Implications: Sludge treatment results in direct and indirect greenhouse gas (GHG) emissions. Moisture reduction followed by incineration is commonly used to dispose of sludge in China; however, few studies have compared the effects of different drying pretreatment options on GHG emissions during such processes. Therefore, in this study, the carbon budgets of sludge incineration were analyzed and compared following different pretreatment drying technologies (biodrying and heat drying). The results indicate that biodrying combined with incineration generated approximately half of the GHG emissions compared to heat drying followed by incineration. Accordingly, biodrying may represent a more environment-friendly sludge pretreatment prior to incineration.     

Urea as a PCDD/F Inhibitor in Municipal Waste Incineration

ABSTRACT

Emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from municipal waste incineration have been widely studied because of their extensive toxicity, and many efforts have been made to restrict their emissions. Although a number of chemical compounds have been shown in laboratory-scale tests to inhibit the formation of PCDD/Fs, few have been tested in pilot- or full-scale plants. This work evaluates the effect of urea as a PCDD/F inhibitor in a pilot-scale incinerator that uses refuse-derived fuel (RDF). The decomposition of urea under the test conditions was also studied using detailed kinetic modeling. An aqueous solution of urea was injected into the flue gas stream after the furnace at ~730 °C, with varied urea concentrations and flue gas residence times used between the furnace and the sampling point. The results demonstrate that urea can successfully inhibit PCDD/F formation in waste incineration if concentrations and injection points are properly adjusted. The kinetic model showed that urea can be rapidly decomposed under appropriate flue gas conditions, indicating that in addition to the urea molecule itself, decomposition products of urea can also be responsible for the reduction of PCDD/F production during incineration.     

NOx Reduction in a Gas Fired Utility Boiler by Combustion Modifications

Data on the effect of several combustion modifications on the formation of nitrogen oxides and on boiler efficiency were acquired and analyzed for a 110 MW gas fired utility boiler. The results from the study showed that decreasing the oxygen in the flue gas from 2.2% to 0.6% reduced the NO_x formation by 33% and also gave better boiler efficiencies. Flue gas recirculation through the bottom of the firebox was found to be ineffective. Staged combustion was found to reduce the NO_x emissions by as much as 55 % while decreasing the efficiency by about 5%. Adjustment of the burner air registers reduced the NO_x formation by about 20 ppm. The lowest NO_x emissions of 42 ppm (at about 3% O₂) in the stack was obtained for air only to one top burner and 0.5% oxygen in the flue gas.     

Authors’ Reply

Emissions from oil-fired residential heating equipment can be reduced by improved steady running and cyclic efficiencies. Techniques which reduce the heating demand (thermostat cut-back) or reduce envelope losses (chimney damper) lead to reductions in SO₂ and NO emissions proportional to the fuel saving. Higher savings in CO and particulates result from cyclic modification. Reductions in nozzle size lead to an increase in unit cycle duration, reducing the off-cycle losses, with emissions reduced similarly. Changing the thermostat anticipator yields little reduction in fuel, SO₂ or NO, but significantly reduces CO and particulate emissions, by decreasing the number of cycles. Improved burner performance, with combustion at low excess air, offers the largest fuel savings, with commensurate reductions in SO₂ and NO, and greater reductions in CO and particulates.     

Suppressing effect of goethite on PCDD/F and HCB emissions from plastic materials incineration

Polyethylene (PE) and polyvinyl chloride (PVC) are the leading plastics in total production in the world. The incineration of plastic-based materials forms many chlorinated compounds, such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). In this study the addition of goethite (alpha-FeOOH) was investigated to determine its suppressing effect on the emission of PCDD/Fs and hexachlorobenzene (HCB) during the combustion of wastes containing PE and PVC. Goethite was being considered since it acts as a dioxin-suppressing catalyst during incineration. Results showed that incorporation of goethite greatly reduced the generation of PCDD/Fs and HCB in the exhaust gas and fly ash. The concentration of PCDD/Fs in flue gas decreased by 45% for lab-scale and 52% for small incinerator combustion experiments, where the goethite ratios in feed samples were 0.54% and 0.34%, respectively. Under the same conditions, the concentration of HCB in flue gas decreased by 88% and 62%, respectively. The present study showed a possible mechanism of the suppressing effect of the goethite for PCDD/F formation. It is likely that iron chlorides react with particulate carbon to form organo-chlorine compounds and promote PCDD/F formation in the gas phase. XRD analysis of combustion ash revealed that the goethite was partially dehydrated and converted to alpha-Fe(2)O(3) and Fe(3)O(4) but no iron chlorides formation. Therefore the goethite impregnated plastics can contribute the reduction of PCDD/Fs and HCB in the exhaust gas during incineration of MSW.     

A Probabilistic Production Costing Analysis of SO2 Emissions Reduction Strategies for Ohio: Emissions,Cost, and Employment Tradeoffs

A new approach for state- and utility-level analysis of the cost and regional economic impacts of strategies for reducing utility SO₂ emissions is summarized and applied to Ohio. The methodology is based upon probabilistic production costing and economic input-output analysis. It is an improvement over previous approaches because it: (1) accurately models random outages of generating units, “must-run” constraints on unit output, and the distribution of power demands; and (2) runs quickly on a microcomputer and yet considers the entire range of potential control strategies from a systems perspective. The input-output analysis considers not only the economic effects of utility fuel use and capital investment, but also those of increased electric rates. Two distinct strategies are found to be most attractive for Ohio. The first, more flexible one, consists of emissions dispatching (ED) alone to meet short run emissions reduction targets. A 75 percent reduction can then be achieved by the turn of the century by combining ED and fuel switching (FS) with flue gas desulfiirization, limestone Injection multistage burners, and physical coal cleaning at selected plants. The second is a scrubber-based strategy which includes ED. By the year 2000, energy conservation becomes a cost effective component of these strategies. In order to minimize compliance costs, acid rain legislation which facilitates emissions trading and places regional tonnage limits on emissions is desirable.     

On-line real-time measurements at incineration plants: PAHs and a PCDD/F surrogate compound at stationary combustion conditions and during transient emission puffs

Laser mass spectrometry has been applied for on-line monitoring of traces of aromatic compounds from flue gas of incineration plants. The experiments have been carried out at two sampling sites in an industrial hazardous-waste incinerator. With laser mass spectrometry resonance-enhanced multiphoton ionization (REMPI) with time-of-flight mass spectrometry (TOFMS) (REMPI-TOFMS), using the group selective multi-component monitoring approach, aromatic compounds are selectively ionized from the complex flue-gas matrix. In this case, the result of an REMPI-TOFMS on-line measurement is a distinct pattern of aromatic compounds. These patterns are dependent on: (i) the point of measurement, (ii) the incineration plant, (iii) the temperature, and (iv) the fuel. This contribution focuses on the fuel dependence of the pattern. The most transient behavior can be observed when containers filled with hazardous waste are burnt, leading to puffs. Real-time monitoring results of puffs are given. Furthermore, as an approach towards on-line monitoring of the TEQ (PCDD/F toxicity equivalent), REMPI-TOFMS on-line analysis results of chlorobenzene are presented.     

Proportional Sampling System for the Collection of an Integrated Auto Exhaust Gas Sample

Carbon baking process involves evolution of fumes containing hydrocarbons and soot particles which cannot be discharged directly into the atmosphere. An incinerator can be used to clean these fumes. However, length of the baking cycle, nature of the fumes and variations in fume volume and temperature may result in excessive auxiliary fuel usage and inefficient incineration, if the incinerator is not designed properly. This paper describes the application of fundamental knowledge of aerodynamics, reaction kinetics and combustion, together with clear understanding of the process, in design of a highly efficient, fully automated incinerator. The design incorporates a unique but simple control system which results in reduction of auxiliary fuel usage without endangering the safety and efficiency of the incineration process. Operations and economics of the incinerator are described by illustrating a typical baking cycle and comparing actual fuel usage with the thermal ratings of the incinerator. Operating experience from a number of installations in the U. S. and Canada is also noted.     

Reduction of combustion by-products in WTE plants: O2 enrichment of underfire air in the MARTIN SYNCOM process

The SYNCOM process involves oxygen enrichment of underfire air, recirculation of flue gas and a combustion control system using infrared thermography of the waste layer on the grate. At the demonstration plant in Coburg, operational reliability and plant availability using SYNCOM could be proven under real disposal conditions with a waste throughput of 7 t/h. Oxygen enrichment of the underfire air promotes the destruction of pollutants due to the high oxygen partial pressures and temperatures. This is then reflected in very low residual amounts of organic combustion by-products in the bottom ash and flue gas from the SYNCOM unit. The flue gas concentrations of organic pollutants are reduced, as compared with conventional operation, by over 35% (for CO, total hydrocarbons and PCDD/F) at the boiler outlet. As the flue gas flow is reduced by oxygen enrichment and flue gas recirculation, the resulting reduction in terms of kg of pollutant per Mg of waste is even higher. In the bottom ash, the level of organic residues is reduced, by 45% in the case of loss on ignition and by 55% in the case of TOC and dioxins (I-TE of PCDD/F). This is due to the higher oxygen partial pressures and the fuel bed temperature which is increased by 135 to 1200 degrees C. Other important features of the process include more intense sintering and thus improved immobilization of the bottom ash, as well as reduced flue gas and fly ash flows.