Hydrogen Chloride Emission Research Articles

Air pollutant emissions and reduction potentials from municipal solid waste incineration in China

China fully implemented the new emission standards in 2016 to further reduce the emissions of air pollutants from the municipal solid waste (MSW) incineration industry; however, the implementation effect of the new standards remains unknown. This study developed the first nationwide air pollutant emission inventory of MSW incineration plants in China based on the measured concentration data from China's continuous emissions monitoring systems (CEMS) network, and activity level data from the China Urban Construction Statistical Yearbook, to evaluate the effectiveness of implementing the new emission standards and estimate the future reduction potentials. Our results demonstrated that the overall standard-reaching proportions of particulate matter (PM), sulfur dioxide (SO2), nitrogen oxide (NOX), hydrogen chloride (HCl) and carbon monoxide (CO) were 98.8%, 99.3%, 99.4%, 99.4% and 97.6%, respectively, by comparing with the corresponding concentration limits of new emission standards. The total emissions of PM, SO2, NOX, HCl and CO from 412 MSW incineration plants in 2019 were 1.9, 6.2, 50.8, 4.3 and 6.6 kt yr−1, respectively, which is 33.6–75.8% lower than those in 2015, mainly due to the sharp decrease in emission factors. Pollutant emission hotspots were mainly concentrated in eastern and central and southern regions with large populations and well-developed economies. The analysis of future scenario results shows that despite the continuous increase of MSW incineration amount in the future, if the government strengthens pollutant emission standards and comprehensively implements waste sorting, total emissions and emission factors of air pollutants could be further reduced by 25.8–72.7% and 59.8–81.2%, respectively, by 2050. These findings provide helpful insights into future policymaking and technology selection for China and other countries seeking to reduce pollutant emissions from the MSW incineration industry.

Chloride (HCl ∕ Cl−) dominates inorganic aerosol formation from ammonia in the Indo-Gangetic Plain during winter: modeling and comparison with observations

Abstract. The Winter Fog Experiment (WiFEX) was an intensive field campaign conducted at Indira Gandhi International Airport (IGIA) Delhi, India, in the Indo-Gangetic Plain (IGP) during the winter of 2017–2018. Here, we report the first comparison in South Asia of high-temporal-resolution simulation of ammonia (NH3) along with ammonium (NH4+) and total NHx (i.e., NH3+ NH4+) using the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) and measurements made using the Monitor for AeRosols and Gases in Ambient Air (MARGA) at the WiFEX research site. In the present study, we incorporated the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) aerosol scheme into WRF-Chem. Despite simulated total NHx values and variability often agreeing well with the observations, the model frequently simulated higher NH3 and lower NH4+ concentrations than the observations. Under the winter conditions of high relative humidity (RH) in Delhi, hydrogen chloride (HCl) was found to promote the increase in the particle fraction of NH4+ (which accounted for 49.5 % of the resolved aerosol in equivalent units), with chloride (Cl−) (29.7 %) as the primary anion. By contrast, the absence of chloride (HCl / Cl−) chemistry in the standard WRF-Chem model results in the prediction of sulfate (SO42-) as the dominant inorganic aerosol anion. To understand the mismatch associated with the fraction of NHx in the particulate phase (NH4+ / NHx), we added HCl / Cl− to the model and evaluated the influence of its chemistry by conducting three sensitivity experiments using the model: no HCl, base case HCl (using a published waste burning inventory), and 3 × base HCl run. We found that 3 × base HCl increased the simulated average NH4+ by 13.1 µg m−3 and NHx by 9.8 µg m−3 concentration while reducing the average NH3 by 3.2 µg m−3, which is more in accord with the measurements. Thus HCl / Cl− chemistry in the model increases total NHx concentration, which was further demonstrated by reducing NH3 emissions by a factor of 3 (−3 × NH3_EMI) in the 3 × base HCl simulation. Reducing NH3 emissions in the 3 × base HCl simulation successfully addressed the discrepancy between measured and modeled total NHx. We conclude that modeling the fate of NH3 in Delhi requires a correct chemistry mechanism accounting for chloride dynamics with accurate inventories of both NH3 and HCl emissions.

Global Emissions of Hydrogen Chloride and Particulate Chloride from Continental Sources.

Gaseous and particulate chlorine species play an important role in modulating tropospheric oxidation capacity, aerosol water uptake, visibility degradation, and human health. The lack of recent global continental chlorine emissions has hindered modeling studies of the role of chlorine in the atmosphere. Here, we develop a comprehensive global emission inventory of gaseous HCl and particulate Cl- (pCl), including 35 sources categorized in six source sectors based on published up-to-date activity data and emission factors. These emissions are gridded at a spatial resolution of 0.1° × 0.1° for the years 1960 to 2014. The estimated emissions of HCl and pCl in 2014 are 2354 (1661-3201) and 2321 (930-3264) Gg Cl a-1, respectively. Emissions of HCl are mostly from open waste burning (38%), open biomass burning (19%), energy (19%), and residential (13%) sectors, and the major sources classified by fuel type are combustion of waste (43%), biomass (32%), and coal (25%). Emissions of pCl are mostly from biofuel (29%) and open biomass burning processes (44%). The sectoral and spatial distributions of HCl and pCl emissions are very heterogeneous along the study period, and the temporal trends are mainly driven by the changes in emission factors, energy intensity, economy, and population.

Chlorine Release from Co-Pyrolysis of Corn Straw and Lignite in Nitrogen and Oxidative Pyrolysis

Elevated emissions of hydrogen chloride (HCl) from the combustion of biomass in utility boilers are a major issue because they can cause corrosion problems and deposit molten alkali chloride salts on boilers’ water tubes, resulting in further corrosion. Pyrolysis is a good pre-treatment for solving this problem. This work conducted pyrolysis and co-pyrolysis of pulverized corn straw and lignite coal in a horizontal muffle furnace, with compositions typical of power plant combustion effluents (5% O2, 15% CO2, 80% N2) at different temperatures. Cl compounds were monitored in fuel, flue gas, and solid production of pyrolysis. The co-pyrolysis significantly affected Cl release from fuel. Cl release from corn straw into fuel gas was reduced during biomass co-pyrolysis with lignite. Co-pyrolysis had little influence on the release of organic Cl and KCl. Furthermore, at moderate-temperature pyrolysis, O2 promoted HCl release, when compared with pyrolysis under a N2 atmosphere.

Anthropogenic emissions of atomic chlorine precursors in the Yangtze River Delta region, China

Chlorine radical plays an important role in the formation of ozone and secondary aerosols in the troposphere. It is hence important to develop comprehensive emissions inventory of chlorine precursors in order to enhance our understanding of the role of chlorine chemistry in ozone and secondary pollution issues. Based on a bottom-up methodology, this study presents a comprehensive emission inventory for major atomic chlorine precursors in the Yangtze River Delta (YRD) region of China for the year 2017. Four primary chlorine precursors are considered in this study: hydrogen chloride (HCl), fine particulate chloride (Cl−) (Cl− in PM2.5), chlorine gas (Cl2), and hypochlorous acid (HClO) with emissions estimated for twelve source categories. The total emissions of these four species in the YRD region are estimated to be 20,424 t, 15,719 t, 1556 and 9331 t, respectively. The emissions of HCl are substantial, with major emissions from biomass burning and coal combustion, together accounting for 68% of the total HCl emissions. Fine particulate Cl− is mainly emitted from industrial processing, biomass burning and waste incineration. The emissions of Cl2 and HClO are mainly associated with usage of chlorine-containing disinfectants, for example, water treatment, wastewater treatment, and swimming pools. Emissions of each chlorine precursor are spatially allocated based on the characteristics of individual source category. This study provides important basic dataset for further studies with respect to the effects of chlorine chemistry on the formation of air pollution complex in the YRD region.

Effects of Municipal Solid Waste Torrefaction and Classification Pretreatment on Hydrogen Chloride Release

The incineration treatment of municipal solid waste is widely used, but gas-phase hydrogen chloride (HCl) generated during the incineration seriously threatens the heating surface of boiler tail, and even causes serious harm to environment. Through incineration experiments, this paper found that many factors (temperature, oxygen concentration, residence time and moisture content) affect the HCl emission characteristics in the process of municipal solid waste incineration treatment. In order to effectively cut back the HCl emission in incineration treatment of municipal solid waste, this paper proposes torrefaction and classification pretreatment of municipal solid waste. Torrefaction pretreatment has a significant inhibitory effect on HCl emission during the incineration of mixed municipal solid waste. At the same time, compared with the incineration treatment of mixed municipal solid waste, sawdust and plastic municipal solid waste of the same quality after classification pretreatment can effectively curb HCl emissions within the entire temperature range. In particular, HCl emissions are reduced by 35% during sawdust incineration treatment at 400°C. Furthermore, by studying the reaction mechanics of HCl generation during combustion at different temperatures, and the reaction rate of HCl generation is: mixed municipal solid waste >plastic >sawdust. Therefore, this paper believes that torrefaction and classification pretreatment of mixed municipal solid waste is beneficial to inhibit the precipitation of chlorine during the incineration process and promotes the resource utilization of municipal solid waste, which is of significant significance for energy conservation and emission reduction.

Uranus’ Stratospheric HCl Upper Limit from Herschel/SPIRE*

Abstract Herschel/SPIRE observations of Uranus are used to search for stratospheric hydrogen chloride (HCl) emission at 41.74 cm−1. HCl was not detected and instead 3σ upper limits were determined; <6.2 ppb (<2.0 × 1014 molecules cm−2) for a 0.1 mbar step profile and <0.40 ppb (<1.2 × 1014 molecules cm−2) for a 1 mbar step profile. HCl is expected to have an external source and these upper limits are consistent with abundances of other external species (CO, H2O, CO2) and a solar composition source.

Neptune’s HCl upper limit from Herschel/HIFI

Here we search for hydrogen chloride (HCl) in Neptune’s stratosphere using observations of the 1876.22 GHz J=3–2 transition from the Heterodyne Instrument for the Far-Infrared (HIFI) on Herschel. Observations comprise a 7.2 hr disc-averaged integration, originally designed to investigate stratospheric methane. Significant HCl emission was not detected. Instead, we determine upper limits using step-type abundance profiles, defined by zero deep abundance and uniform volume mixing ratio for pressures less than a transition pressure (assumed to be 0.1 or 1 mbar). These profiles are a reasonable first-order approximation for an externally sourced species; at higher pressures HCl is expected to be removed by aerosol scavenging and reactions with ammonia. The 3σ upper limits are <0.70 parts per billion (ppb) for a 0.1 mbar transition pressure and <0.076 ppb for a 1 mbar transition pressure. These upper limits are the most stringent to date and are consistent with current estimates of interplanetary dust particle flux and the hypothesis that Neptune experienced a large comet impact in the past 1000 years.

Coastal Sea Salt Chlorine Deposition Linked to Intertropical Convergence Zone (ITCZ) Oscillation in French Guiana

AbstractSea salt chloride is a major component of atmospheric aerosol and its behavior is an essential element in determining the climate. Two atmospheric chlorine deposition measurement procedures were performed between 2004 and 2008 by the French Guiana Regional Air Observatory (ORA), in the coastal plain of Sinnamary. The main goal was to determine the background spatial distribution of marine chlorine in order to evaluate the impact of Ariane rocket hydrogen chloride emission. To determine the chlorine concentration level, weekly samples from 10 sites were analyzed. A seasonal pattern was identified. For every site, a high sea salt chlorine deposition level was observed from December to April and a low level from July to October. The ratio of high to low mean chloride concentration RHC/LC shows that just under half of the variation in chlorine deposition can be linked to the variation of sea salt production with low-level wind speed. Equations relating mean sea salt chlorine concentration and the distance to shore were studied, taking into account parameters found in other tropical regions, with a focus on neighboring Brazil. The wind rotation between the two seasons, and the sea salt chlorine loss per kilometer equation found for dry deposition, were used to calculate RHC/LC. It appears that the observed rotation (60°) explains 88% of RHC/LC. Finally, inland sea salt chlorine deposition behavior in this region was linked to intertropical convergence zone oscillation through variations in wind speed and direction.

Co-combustion of residual forest biomass and sludge in a pilot-scale bubbling fluidized bed

In this work, the co-combustion of residual forest biomass from eucalyptus and its blend with different amounts of primary and secondary sludge from the pulp and paper industry was studied in a pilot-scale bubbling fluidized bed reactor. The main objective was the determination of sludge addition influence on the overall process and on the composition of the exhaust gases, with emphasis on chlorine emissions, namely present in the solid phase (fly ashes) and in the gaseous phase (hydrogen chloride), and nitrogen oxides emissions. The co-combustion process of residual forest biomass with primary sludge (up to 5% in mass) and secondary sludge (up to 10% in mass) was successfully demonstrated as a valid energy valorization option. Except specific cases, no significant emissions increase of nitrogen oxides, carbon monoxide or hydrogen chloride were found with the addition of sludge. In fact, hydrogen chloride emissions decreased, potentially due to an increase in the chlorine retention in ashes caused by the high inorganic content present in the sludge. This high inorganic content can also lead to a significant increase in ash production during the combustion process. Thus, consequently, without proper maintenance, significant ash accumulation along the combustion system may occur, which can decrease the process efficiency and cause equipment damage.

Thermogravimetric and Kinetic Study of Pyrolysis of Chlorine-Containing Medical Waste

In this paper, the thermal decomposition (pyrolysis) of components of medical waste that consist of polyvinyl chloride (medical oilcloth and tubes of blood transfusion systems) is investigated. Thermogravimetric analyzes were performed in the TG-DTG mode on the synchronous thermal analysis device NETZSCH STA 449 F3 Jupiter. Based on the data obtained, the calculation of the kinetic parameters of the process of thermal decomposition of the investigated samples of medical waste was performed. For tubes of blood transfusion systems, experiments were conducted to absorb gases entering from the reaction volume in order to determine the temperature range of hydrogen chloride emission.

Interaction of magnesium production salt melts with atmospheric air

The paper provides a review of the literature on the interaction of magnesium production salt melts with atmospheric air. The method for measuring the mass of reaction products of the molten salt with air is described. The results of investigation of hydrogen chloride and chlorine emission intensity by salt melts of MgCl 2 -KCl-NaCl, MgCl 2 -KCl-NaCl-BaCl 2 , MgCl 2 —KCl—NaCl—CaCl 2 systems, as well as the intensity of HCl + HBr and Cl 2 + Br 2 gas emission by MgCl 2 —KCl—NaCl—NaBr system salt melts are presented. Thermodynamic analysis of reactions of interaction of magnesium salt melts with atmospheric air is carried out. It is determined that magnesium chloride in salt melt interacts with atmospheric air most intensively with the release of chlorine and hydrogen chloride. Specific rates of halogen-containing gases formation per unit surface area of the MgCl 2 -KCl-NaCl, Mga 2 -KCl-NaCl-BaCl 2 , MgCl 2 -KCl-NaCl-CaCl 2 , MgCl 2 -KCl-NaCl-NaBr systems are measured. The influence of calcium chloride, sodium bromide and magnesium fluoride on the intensity of halogen-containing gases emission by the surface of salt melts is studied. It is found that the addition of magnesium fluoride in the composition of chloride melts reduces the intensity of chlorine and hydrogen chloride emission.

Hydrogen chloride (HCl) absorption by raw meal and raw meal compounds, using in-situ HCl generation and TGA-FTIR tests

HCl emission control optimization from cement plants requires a quantification of the HCl absorption capacity of raw meals (mixtures of fine particles of raw materials) and the determination of raw meal constituent effects on HCl capture below 400 °C. This work reports lab data obtained by ramping temperature tests using a standard TGA-FTIR set-up, a thermally degradable solid HCl source (AlCl3·6H2O), industrial raw meals, and mixtures of reagent grade raw meal constituents (SiO2, CaCO3, Fe2O3, and Al2O3). The lab data showed that industrial raw meals had significantly higher HCl absorption capacity than reagent grade CaCO3. The presence of Fe2O3 promoted HCl capture by CaCO3 between 90 °C and 350 °C. The HCl absorption by raw meals was higher when the HCl source was dispersed rather than when it was placed below the raw meals.

Formation and emission of hydrogen chloride in indoor air

To improve our understanding of chlorine chemistry indoors, reactive chlorine species such as hydrogen chloride (HCl) must be analyzed using fast time-response measurement techniques. Although well studied outdoors, sources of HCl indoors are unknown. In this study, mixing ratios of gaseous HCl were measured at 0.5Hz in the indoor environment using a cavity ring-down spectroscopy (CRDS) instrument. The CRDS measurement rate provides a major advance in observational capability compared to other established techniques. Measurements of HCl were performed during three types of household activities: (a) floor exposure to bleach, (b) chlorinated and nonchlorinated detergent use in household dishwashers, and (c) cooking events. Surface application of bleach resulted in a reproducible increase of 0.1 ppbv in the affected room. Emissions of HCl from automated dishwashers were observed only when chlorinated detergents were used, with additional HCl emitted during the drying cycle. Increased mixing ratios of HCl were also observed during meal preparation on an electric element stovetop. These observations of HCl derived from household activities indicate either direct emission or secondary production of HCl via chlorine atoms is possible. Calculations of photolysis rate constants of chlorine atom precursors provide evidence that photolysis may contribute to indoor HCl levels.

Indirect environmental benefits of a variable set-point for HCl emission in waste-to-energy flue gas cleaning

Hydrogen chloride (HCl) is a typical contaminant generated in waste combustion, whose emission is strictly regulated. In order to cope with severe limits issued by local authorities on the annual mass flow of HCl emitted, several European waste-to-energy plants perform at least a two-stage abatement of the pollutant and operate with a set-point for HCl concentration at stack well below the hourly emission limit imposed by the Industrial Emissions Directive. Even though the operating conditions in a WtE facility are highly variable (both in terms of HCl release from the burnt waste and of operating temperature of the HCl removal system), it is common industrial practice to keep both the set-point for HCl concentration at stack and the set-point for HCl concentration between the two abatement stages at a constant value. However, this might force the abatement system to operate far from its design conditions and from the optimal reactivity window of the adopted HCl removal agent, thus increasing the consumption rate of reactant and the consequent generation rate of process residues. Both the supply chain of reactants and the management of residues generate environmental impacts. The present work demonstrates that the adoption of variable values for both set-points can provide cost savings and indirect environmental benefits, thanks to the reduction of reactant consumption and residue generation. By considering as case study a WtE plant equipped with a two-stage dry HCl removal system, a year of operation of the plant was analysed. The operating costs and life cycle impacts generated by the actual operation of the HCl treatment system with constant set-points were compared with those generated if the plant had operated with variable set-points, simulated with a semi-empirical model for HCl removal tuned on historical process data from the plant. A 13 % reduction of the life cycle global warming impact and an 8 % reduction of the life cycle acidification impact, in addition to 10 % cost savings, were associated to the utilisation of variable set-points.

Reduction of HCl Emissions from Combustion of Biomass by Alkali Carbonate Sorbents or by Thermal Pretreatment

Elevated emission of hydrogen chloride (HCl) from the combustion of biomass in utility boilers is a major issue, as it can cause corrosion, and in combination with the high alkali content often encountered in these fuels, it can deposit molten alkali salts on the boiler’s water tubes. Such deposition can impede the heat transfer and cause further corrosion. Previous work in this laboratory showed that the HCl emissions of biomass combustion can be drastically abated by burning torrefied biomass instead of raw biomass. Alternatively, the present work concentrated on using alkali-based sorbents to capture the HCl emissions from the combustion of raw biomass and reported on their effectiveness. It burned corn straw and corn-based distillers dried grains with solubles (DDGS), both pulverized to the size range 75–150 µm. Their combustion products were treated with calcium carbonate (CaCO3), sodium carbonate (Na2CO3), and potassium carbonate (K2CO3). The high-temperature evaluation of the sorbent’s performance was achieved by the coinjection of the sorbents with biomass in a drop tube furnace (DTF) at steady-state steady-flow conditions. Moderate- and low-temperature evaluation of the sorbent’s performance was achieved by allowing the effluents of the batch combustion of the biomass to pass through heated fixed beds of the alkali carbonates. In all experiments, the HCl reductions by the sorbents ranged from 10 to 57% at a molar alkali/chlorine ratio of ∼5 and a gas/sorbent contact time on the order of 1 s. The HCl reduction by the alkali carbonate sorbents at the high temperature (1,350 K) was comparable to that achieved at the moderate temperatures (773 and 573 K), whereas the reduction at room temperature (298 K) was lower. Potassium carbonate was more effective than sodium carbonate, which in turn was more effective than calcium carbonate in the HCl capture. However, under all the current experimental conditions, the replacement of the raw biomass fuel with thermally pretreated biomass (torrefied at 523 K) resulted in HCl emissions that were lower than those from treating the effluents of raw biomass with the previously described alkali carbonate sorbents.

Modeling the impact of chlorine emissions from coal combustion and prescribed waste incineration on tropospheric ozone formation in China

Abstract. Chlorine radicals can enhance atmospheric oxidation, which potentially increases tropospheric ozone concentration. However, few studies have been done to quantify the impact of chlorine emissions on ozone formation in China due to the lack of a chlorine emission inventory used in air quality models with sufficient resolution. In this study, the Anthropogenic Chlorine Emissions Inventory for China (ACEIC) was developed for the first time, including emissions of hydrogen chloride (HCl) and molecular chlorine (Cl2) from coal combustion and prescribed waste incineration (waste incineration plant). The HCl and Cl2 emissions from coal combustion in China in 2012 were estimated to be 232.9 and 9.4 Gg, respectively, while HCl emission from prescribed waste incineration was estimated to be 2.9 Gg. Spatially the highest emissions of HCl and Cl2 were found in the North China Plain, the Yangtze River Delta, and the Sichuan Basin. Air quality model simulations with the Community Multiscale Air Quality (CMAQ) modeling system were performed for November 2011, and the modeling results derived with and without chlorine emissions were compared. The magnitude of the simulated HCl, Cl2 and ClNO2 agreed reasonably with the observation when anthropogenic chlorine emissions were included in the model. The inclusion of the ACEIC increased the concentration of fine particulate Cl−, leading to enhanced heterogeneous reactions between Cl− and N2O5, which resulted in the higher production of ClNO2. Photolysis of ClNO2 and Cl2 in the morning and the reaction of HCl with OH in the afternoon produced chlorine radicals which accelerated tropospheric oxidation. When anthropogenic chlorine emissions were included in the model, the monthly mean concentrations of fine particulate Cl−, daily maximum 1 h ClNO2, and Cl radicals were estimated to increase by up to about 2.0 µg m−3, 773 pptv, and 1.5 × 103 molecule cm−3 in China, respectively. Meanwhile, the monthly mean daily maximum 8 h O3 concentration was found to increase by up to 2.0 ppbv (4.1 %), while the monthly mean NOx concentration decreased by up to 0.5 ppbv (6.1 %). The anthropogenic chlorine emissions potentially increased the 1 h O3 concentration by up to 7.7 ppbv in China. This study highlights the need for the inclusion of anthropogenic chlorine emission in air quality modeling and demonstrated its importance in tropospheric ozone formation.

Anthropogenic Emissions of Hydrogen Chloride and Fine Particulate Chloride in China.

Particulate chloride (Cl-) can be transformed to nitryl chloride (ClNO2) via heterogeneous reaction with nitrogen pentoxide (N2O5) at night. Photolysis of ClNO2 and subsequent reactions of chlorine radical with other gases can significantly affect the atmospheric photochemistry. In China, the only available integrated anthropogenic chloride emission inventory was compiled in the 1990s with low spatial resolution, which hinders assessment of impact of ClNO2 on current air quality. In this study, we developed an up-to-date and high-resolution anthropogenic inventory of hydrogen chloride (HCl) and fine particulate Cl- emissions in China for 2014 with 0.1° × 0.1° resolution. Detailed local data and county-level activity data were collected and complied. The anthropogenic emissions of HCl and fine particulate Cl- in 2014 were estimated to be 458 and 486 Gg, respectively. Biomass burning was the largest contributor, accounting for 75% of fine particulate Cl- emission and 32% of HCl emission. Northeast China and North China Plain were the largest chloride emitters. The monthly distribution varied in different regions, due to different agricultural activities and climate conditions. This work updates the chloride emission information and improves its spatial and temporal resolution, which enables better quantification of the ClNO2 production and its impact over China.

Hydrogen Chloride Release From Combustion of Corn Straw in a Fixed Bed

Chlorine plays an important role in the slagging and corrosion of boilers that burn high-chlorine content biomass. This research investigated the emissions of hydrogen chloride (HCl) gas from combustion of biomass in a fixed bed, as functions of the mass air flow rate through the bed and of the moisture content of the fuel. The biomass burned was corn straw, either raw or torrefied. Results showed that increasing the air flow rate through the bed increased the release of HCl gas, as a result of enhanced combustion intensity and associated enhanced heat release rates. When the airflow through the bed was increased by a factor of six, the amount of fuel-bound chlorine converted to HCl nearly tripled. Upon completion of combustion, most of the chlorine remained in the biomass ashes, with the exception of the highest air flow case where the fraction of chlorine released in HCl equaled that captured in the ashes. HCl emissions from torrefied biomass were found to be lower than those from raw biomass. Finally, drying the biomass proved to be beneficial in drastically curtailing the generation of HCl gas.

Life-cycle environmental and economic assessment of medical waste treatment

The environmental and economic impacts of three medical waste disposal scenarios (i.e., pyrolysis, steam sterilization, and chemical disinfection) were quantified via a cost-coupled life cycle assessment to quantify the effective technique for medical waste disposal. Results show that steam sterilization and chemical disinfection scenarios exhibit the highest overall environmental and lowest economic impacts, respectively, because of the differences in energy consumption. The overall economic burden is attributed to the cost of investment, labor, electricity, and human health protection for each scenario, whereas the environmental burden comes from energy and chemical production processes. The contribution of hydrogen chloride emission to the overall environmental burden is relatively low, although the direct hydrogen chloride emission is significantly higher when generated from medical waste pyrolysis than from municipal solid waste and industrial hazardous waste incineration. However, opposite results are observed for direct mercury emission. Effective measures to reduce the environmental burden include improving electricity and diesel consumption efficiency, reducing the use of chemicals (e.g., sodium hydroxide, lime, and chlorine oxide), selecting clean energy, and providing medical waste incineration with energy recovery. Similarly, effective measures to reduce the economic impact include optimizing labor and investment costs and electricity consumption.