Glass Furnace Research Articles

On the use of hydrogen in oxy-fuel glass melting furnaces: An extensive numerical study of the fuel switching effects based on coupled CFD simulations

The present study examined the potential of utilizing hydrogen as a fuel in an industrial cross-fired oxy-fuel glass melting furnace with a total energy input of 3.9 MW. To this end, comprehensive three-dimensional CFD simulations were performed in Ansys Fluent, employing a coupled numerical model from preceding works. A two-step validation process was presented, comprising the validation of both the numerical furnace setup and the modeling of industrial oxy-fuel combustion setups using hydrogen as a fuel gas. Assuming an equal thermal energy input for both combustion conditions, the fuel/oxidizer ratios of velocity and momentum of the six PrimeFire burners were found to be significantly affected. Consequently, the low-momentum flames with natural gas transformed into jet-type flames with a straighter trajectory when transitioning to hydrogen. This change led to an enhanced turbulent mixing and a reduction of flame lengths by over 25%, while the average flame temperature increased by up to 82 K due to the accelerated reaction kinetics. In addition, the elevated flame momentum in the cross-fired burner configuration resulted in a localized rise in maximum side wall temperatures by more than 20 K. With the exception of these local effects, the global temperature distribution and heat transfer mechanisms were not significantly impacted. This indicated a comparable melting process and furnace efficiency, while still allowing for a reduction of total CO2 emissions by 77.5%. Future research should concentrate on both the impact on glass quality and the evaluation of potential alternative burner configurations for hydrogen-fired oxy-fuel glass melting furnaces.

Study on the Characteristics of Molten Glass in a Float Glass Process with a New Structure.

Glass is one of the most common materials in society, and the float glass process is the main production method of glass used at present, which involves adopting a melting furnace with a single cooler. However, this structure has been difficult to fit to the requirements of modern glass production, such as producing multiple types of glass and large-scale production. Therefore, a large-tonnage float glass melting furnace with a double cooler is studied, which is rising in popularity in the glass sector. The aim of this paper is to clarify the characteristics of the new glass furnace. A numerical simulation technique is applied to analyze the thermal and flow characteristics of molten glass in the new structure so as to clarify the feasibility of production by checking the temperature distribution and flow field of the molten glass. The results show that the new structure also exhibits flow behavior similar to the original structure in the branch line. Due to the addition of the branch line, the stability of the temperature is improved, with a 60 K and 43 K difference between the surface and bottom in the main and branch lines, respectively. Similar stability is shown in the flow field, specifically low acceleration in the cooler (0.006 m/s2). The bubble clarification time is about 2700 s, less than the 3000 s required for flow. The parameters of the branch line meet the requirements of glass production. In theory, a glass-melting furnace with a double cooler has the capacity to produce two types of glass.

Status and prospects of energy efficiency in the glass industry: Measuring, assessing and improving energy performance

The significant share of energy-related emissions in the glass industry necessitates robust energy efficiency strategies. This paper evaluates the status and prospects of energy efficiency by integrating the measurement, assessment, and improvement of energy performance through energy data and modelling. Measurement and assessment are crucial for effective energy management in hard-to-abate industrial sectors, providing insight into the existence and extent of potential energy efficiency gains. The use of appropriate performance indicators allows for comparison across production contexts and the monitoring of improvements achieved through interventions. The benchmarking of a representative sample of container glass furnaces reveals a current potential for improvement of around 10% based on alignment with best practices. Energy modelling is used to map energy flows along the various systems involved in production, thereby identifying major energy losses. Energy efficiency options can then be categorised based on their contribution to improving energy performance, facilitating the identification of solutions that address current bottlenecks. The study discusses promising opportunities arising from improved batch compositions and outlines the role of renewable penetration on the viability of hydrogen use and furnace electrification. The proposed approach can be transferred to other hard-to-abate industrial sectors to drive progress in decarbonisation.

Sustainable construction materials from alkali-activated waste fiberglass and waste refractory

In this work, waste fiberglass was up-cycled, alone, or mixed with used alumina-zirconia-silica (AZS) refractory from dismantled glass melting furnaces. Alkali activation was performed by suspending fiberglass and fiberglass/AZS powders in NaOH aqueous solution of various concentrations (8M, 6M, and 3M). The activation of waste fiberglass with 8M NaOH yields a gel with calcium and sodium-containing aluminosilicate hydrates. The addition of AZS refractory enabled the release of aluminates into the solution, which had beneficial effects on the mechanical properties. Low molarity activation yielded weaker materials which could be used as precursors for firing at moderate temperatures (800 °C and 1000 °C) to create cellular glass-ceramics, with a total porosity of up to 92 %. The firing of 8M activated samples resulted in glass ceramics with a 66–75 % porosity range and compressive strength of 10–23Mpa. The compressive strength-to-density ratio before and after firing was comparable to that of established commercial construction materials.

Simulation of the work of glass furnaces with the purpose of searching for reserves and increase their efficiency

The object of research is the operation of a glass furnace. The work involved modeling the operation of a glass furnace by changing the technical and economic indicators of its operation in order to optimize the technological processes of manufacturing glass products, increase the energy efficiency of the process, and reduce the ecological burden on the environment. Glass furnaces are complex heat engineering units that require a large amount of energy to operate. Therefore, increasing their effectiveness is the main task of our research. In the work, computer modeling of thermal processes in the furnace was carried out, heat balances were calculated and analyzed, and the performance of the furnace was analyzed after changing and improving the technological regimes of combustion processes, glass boiling and furnace construction. Studies have shown that in order to increase the technical and economic performance of glass furnaces, it is advisable to conduct additional thermal insulation of the furnace enclosures. The thermal insulation of the vault increases the efficiency of the furnace by 2–3 %, and the thermal insulation of the remaining areas of the furnace in total allows to increase the efficiency of the heating unit up to 3 %. Such measures improve the sanitary and technical working conditions of the staff in the machine-bath shop. Studies have shown that additional heating of the air used for burning fuel significantly increases the efficiency of the furnace. Thus, an increase in air temperature by 100 °C increases the efficiency of the furnace by approximately 2.5 %. However, such a measure is possible with a corresponding increase in the volume of regenerator nozzles. A significant increase in the efficiency of the furnace was achieved when additional electric heating was installed. This allows to reduce the total energy costs, and at the same time, the introduction of every 10 % of additional electric heating increases the efficiency of the furnace by up to 3 % and improves the quality of the glass mass. Such additional heating can be recommended in the amount of 20–30 % of the total heat consumption for the operation of the furnace. The analysis of the obtained results showed a fairly good convergence of the results, which indicates the acceptable adequacy of the models. The obtained process simulation results allow choosing the optimal design and operation parameters of the glass furnace. The results of the work can be used in practice for the design of efficient glass furnaces of various purposes and performance.

Comparative analysis of combustion characteristics and economy between air assisted combustion and oxy-fuel combustion in glass furnaces

The oxy-fuel combustion is an effective means to improve the high energy consumption, pollution, and economic cost of glass furnaces. In this paper, the combustion characteristics in the flame spaces of traditional natural gas/air assisted combustion glass furnace (GF-NAC) and reformed natural gas/oxy-fuel combustion glass furnace (GF-NOC) are analyzed and compared by means of numerical calculation. More importantly, a systematic quantitative comparative analysis is conducted on the economic performance of the two glass furnaces from the perspectives of fixed and operating costs. The results show that enhanced combustion performance of GF-NOC over GF-NAC is found with flames being extended across the entire width of the furnace in GF-NOC. A more uniform temperature distribution within the furnace is consequently accomplished in GF-NOC. The flame center temperature, the average furnace temperature, and the average glass surface temperature in GF-NOC are increased by 7.42 %, 1.17 %, and 7.96 %, respectively, compared to GF-NAC. Furthermore, a reduction in gas velocity by 50 % at the arch in GF-NOC is observed to mitigate the erosive effects of high-temperature gas flows on the furnace crown. According to the service life of glass furnace of 15 years, the GF-NOC can save 420 M (million yuan) (12.8 %) compared to the GF-NAC. Although the fixed cost of GF-NOC is 9.82 M (5.43 %) higher than that of GF-NAC due to the expenditure on oxygen production equipment, the difference is offset by operating costs. Compared to GF-NAC, GF-NOC can save operating costs of 28.7 M (15.87 %) per year.

Effect of metakaolin content and shape design on strength performance of lightweight rubberized geopolymer mortars incorporated slag-waste glass powders

Lightweight rubberized geopolymer (LRGP) has gained attention due to its economic, engineering, and environmental benefits. With the rising human demands, the need for alternative materials to meet the requirements of infrastructural expansion, and global industrialization required. Based on those facts, this study aimed to develop of lightweight geopolymer mortars using wastes rubber as fine aggregate (WRA) to replace the natural aggregates, which metakaolin (MK), wastes bottle glass (WBG) and granulated blast furnace slag (GBFS) used as precursor materials with alkaline activator contained low molarity of sodium hydroxide solution and sodium silicate and cured at ambient temperatures. The effect of WRA on physical, mechanical, and microstructural properties of metakaolin-based rubberized geopolymer has been evaluated by using several tests such as compressive, flexural and tensile strength. As well as morphology and chemical reaction on LRGP by using AFM, FESEM, EDX, FTIR and XRD tests. In addition, a sustainable shape design has been cast and subjected to compressive strength to obtain the strength performance of the proposed LRGP mortar. At optimal mixture, the SEM images exhibited improvement in the interfacial transition zone (ITZ) among WRA and binder, leading rubberized geopolymer with 15% WRA to achieve a strength of 27.47 MPa after 28 days and with a reduction in density by 7.2%. The findings of this study can provide valuable insights on utilizing WRA in the shape design and formulation of geopolymer mortar, a key ingredient in the development of functional environmentally friendly building materials.

Effect of Residence Time on Desulfurization and Denitration by the Semi-Dry Ozone Injection Reactor

ABSTRACT The semi-dry nonthermal plasma-induced ozone injection process is a promising desulfurization and denitration method for flue gases emitted from glass melting furnaces. To design a reactor for this process in an actual plant, it is necessary to evaluate the effect of the residence time of the flue gases in the reactor on desulfurization and denitration. In this study, the inner volume of the reactor was vertically divided into ten sections corresponding to the temperature measurement points. The residence time of each section was calculated to determine the residence time in the reactor. The effect of residence time on desulfurization and denitrification was then elucidated. In addition, the nitrite ( N O 2 − ) and nitrate ( N O 3 − ) ions in the droplets collected in the wastewater tank connected to the bottom of the reactor and in the condensates in the condensers downstream of the reactor were measured to evaluate the nitrogen balance with respect to the removed NOx.

Techno-economic evaluation of a thermochemical waste-heat recuperation system for industrial furnace application: Operating cost analysis

An operational cost analysis was conducted to determine the optimal parameters for achieving maximum net present profit value through thermochemical recuperation (TCR). The parameters of the TCR system (enthalpy, temperatures of exhaust gas and synthesis gas) were determined based on computational fluid dynamics (CFD) modeling. The results of the CFD modeling were verified using experimental data. The techno-economic evaluation of the TCR system was performed for two types of industrial furnaces with methane mass flow rate of 1.0 kg/s: a glass-melting furnace with an exhaust gas temperature of 1500 °C and a forging furnace with an exhaust gas temperature of 900 °C. The operational parameters of the steam methane reforming process varied during analysis: a residence time of 50–250 kgcat⋅s/molCH4, a feed steam-to-methane ratio of 1.0–3.0 mol/mol, and an operational pressure of 10 bar. Various prices for catalyst, electricity, and natural gas, as well as different replacement periods for the catalyst, were analyzed. It was found that the net present profit had an extreme value that depended on operational and cost parameters. The optimal residence time (specific mass of catalyst per mole flow rate of methane) was determined for various operational and cost parameters of the TCR system.

Effect of ammonia-air combustion melting on the color and physical properties of soda lime silicate

Ammonia is a carbon-free fuel; hence, it does not generate CO2 during combustion. However, ammonia has a different combustion reaction and flue gas composition from conventional city gas; therefore, its impact on the glass-melting process and glass quality is unknown. In this study, batches of soda lime silicate glass and cullet raw materials were melted using ammonia or city gas as the fuel. Furthermore, the glass melted in the combustion and exhaust gas fields was analyzed to evaluate the effects on composition and color tone. The type of fuel and combustion atmosphere were found to affect the color and glass transition temperature. The batches and cullet materials that melted in the combustion field were colored because of combustion-atmosphere-induced changes in the valence of the Fe in the raw materials, and the coloration of this glass was more affected by the cullet than by the batches. Meanwhile, the glass melted in the exhaust gas field of ammonia combustion exhibited a lower glass transition temperature owing to the higher presence of H2O in the exhaust gas. The temperature was measured by four thermocouples (TC1–4) installed inside the furnace. The glass transition temperature of the glass at the TC4 position in the exhaust gas field using ammonia as fuel was 24 and 9 °C lower than those of the reference batch and cullet, respectively. Ammonia can be used as a decarbonized fuel for glass-melting furnaces by designing raw materials for soda lime silicate glass. However, the raw materials containing carbonates emitted CO2 in the exhaust gases during ammonia combustion. Therefore, to achieve a carbon-neutral glass manufacturing process, CO2 derived from both raw materials and fuel should be reduced.

Dynamic Modeling Simulation of Regenerator for Glass Furnace Applications

The melting process in the glass industry is an energy-intensive process that uses fossil fuels to maintain melting temperatures between 1600°C and 1700°C. The process is carried out in the Glass Furnace. Obtained the high temperature also of flue gas is around 1350 °C – 1500 °C. Hence with the high temperature is potential to heat recovery in the form of combustion air pre-heating using a regenerator to increase the efficiency in Glass Furnace. This phenomenon gave rise to an idea to create a modelling mathematic to know the optimum process in Glass Furnace. Many studies on Glass furnace regenerator have been carried out but only for one cyclic of heat transfer in regenerator. Therefore, in this study, dynamic modeling of the regenerator will be made, namely a mathematical model that describes quantitatively the dynamic behavior during the process of reversing the direction between the regenerators, which will later explain the effect of air flow rate and the selection of the optimal transition time value for the demonstration, regenerator work and regenerator heat stability, by observing the dynamic behavior of the regenerator temperature profile using the FlexPDE software version 7. The simulation results show that the longer the switching time of regenerator is linier to inclining temperature in the regenerator with the optimum switching time (ST) at 10 minutes. The regenerator heat stability greatly influenced by air flow rate and heat propagation by heat transfer convection. However, the dimension selection of the regenerator plays a crucial role in heat utilization in glass furnaces.

Space numerical simulation of full oxygen combustion flame in glass melting furnace based on flue gas preheating

This study explores the innovative design of a glass-melting furnace, which incorporates a combustion lance and a flue on one side. The research validates the simulation that the high-temperature flue gas, produced by the pure oxygen combustion of natural gas, can utilize residual heat in a multi-stage process to preheat and burn the fuel natural gas via a jet heat pump. This process significantly reduces energy consumption, thereby decreasing construction costs and energy usage in industries related to glass furnace production. The research focuses on the flame space of a 600 t/day natural gas flat glass all-oxygen combustion furnace. Utilizing numerical calculation methods, a three-dimensional mathematical model of the all-oxygen lance flame space was developed. Numerical simulation methods were employed to examine the temperature field, airflow field, and the distribution pattern of the liquid flow field within the glass space in the furnace. The simulation results reveal that incorporating high-temperature flue gas into the fuel can markedly enhance the performance of the spray gun flame. Additionally, choosing spray gun outlet designs of varying widths can tailor the flame width to better meet the requirements of the glass melting system, thereby significantly improving the waste heat utilization rate of the flue gas. This offers more alternatives for the direct utilization of flue gas. When compared to traditional oxy-combustion glass melting furnaces, this innovative design substantially reduces construction costs and is more energy-efficient and environmentally friendly.

Industrial Technologies for CO2 Reduction Applicable to Glass Furnaces

In recent years, the European Union’s legislation about sustainable development has promoted the gradual decarbonization of all industrial sectors, pushing towards the final goal of a carbon-neutral European glass industry in 2050. Moreover, the COVID-19 pandemic, the war in Ukraine and the consequent natural gas supply crisis have led to significant increases in the costs of traditional energy commodities and CO2 emission allowances. In this scenario, the European glass industry, which is both an energy-intensive sector and a large emitter of CO2, needs to reduce its specific energy consumption, change its energy sources and decarbonize its production process. In order to understand and support this metamorphosis of the glass industry, the follwing questions must be answered: are the technologies reported in scientific publications merely theoretical exercises, or can they be adopted by the industry? In what timeframe can they be adopted? The aim of this study is to review consolidated and emerging technologies applicable to the glass industry and investigate which ones can be implemented in the short or medium term to reduce energy consumption and CO2 emissions related to the glass production process. This study is based on a review of the literature, the materials presented in technical conferences and the opinions of interviewed experts. This study showed that the literature is not very substantial, lacking detailed information on technologies and their effects in terms of energy savings or emissions. More information can be found in the proceedings of selected specialist conferences. This study found that, on one hand, some technologies are mature and only adopted when economically viable, and appropriate boundary conditions are available; the state of the art regarding these technologies was already extensively covered in past publications (e.g., cullet pre-heating). On the other hand, there are many promising technologies in the research or testing phase (i.e., steam methane reforming, process electrification, use of hydrogen); in-depth studies about them are limited due to the novelty of the solutions that they propose or not available due to industrial secrecy issues. In addition to periodicals and specialized conferences, interviews were carried out with managers and technicians from industry, as well as technicians from the Italian glass research institute and industrial machinery producers (especially melting furnaces). The interviews represent added value of this publication, useful in helping us to truly understand the state of the art and degree of readiness of the technologies identified. In addition, the production values of the glass industry were studied: our research confirmed that the most important sub-sectors are flat and container glass, as well as the largest glass-producing nations/continents. Finally, a review of specific energy consumption and CO2 emissions indexes was carried out.

INTEGRATION OF OPERATION OF REGENERATORS OF GLASS FURNACES

The material of the article relates to the glass industry, namely to equipment for cooling the roof of regenerators of glass melting furnaces and can be used in the construction of new or reconstruction of existing regenerators.
 When the refractories of industrial glass melting furnaces are destroyed, an intensive decrease in the wall thickness of the melting basin occurs, which leads to a significant increase in the temperature of the outer surface of the walls and, accordingly, an increase in heat losses. The maximum destruction of the refractory masonry of the walls of the melting basin is observed at the level of the mirror of the melted glass. There is uneven wear along the height and perimeter of the pool. The rate of destruction of the masonry is determined by the stability of the used refractories, the temperature regime of glass melting, and the design features of the units.
 The technical task of the article is: to increase the service life of the refractory masonry of the glass furnace regenerator roof; utilization of the heat of the outer masonry surface of the regenerator roof, as well as improvement of its cooling system by using water cooling of the outer surface of the regenerator roof; saving fuel consumed to heat the same amount of coolant in boiler equipment.
 The proposed cooling of the outer surface of the regenerator roof makes it possible to: reduce the temperature of the outer surface of the roof to the level of 30 °C and at the same time make the most of the heat of the outer surface of the regenerator roof, which has not been used before, for example, to obtain hot water from a heat supply system, and this makes it possible to save fuel costs, which are necessary for the operation of boiler equipment to heat the same amount of coolant; to ensure a more uniform distribution of temperature fields over the entire plane of the regenerator roof by using flat collectors of a special design, which, in turn, makes it possible to slow down the process of destruction of the refractory lining of the regenerator roof. The thermocouples installed in the pipelines make it possible to monitor the change in the temperature of the coolant in the collectors, and in the event of an increase in the surface temperature of the collectors, the automation increases the flow of the coolant in the pipelines. The collectors are equipped with pressure valves, when the temperature of the coolant in the collector is above 100 °C, it can boil in the collector and then the pressure valve equalizes the pressure in the collector.

Glassmaking remains from the 12th to 14th centuries CE glass workshop in Boshan, Shandong Province, China

Many glass furnaces producing K2O-CaO-SiO2 glass were excavated in Yanshen Town, Zibo city, Shandong province, dating to the Jin to Ming Dynasties, a large-scale glass-making center recorded in historical sources. According to the typological study of ceramics, the workshop which produced the studied samples dated from the Jin to the Yuan Dynasties (12th to 14th centuries CE), and is one of the earliest archaeological glass workshops found in China. The workshop yielded many semi-finished glass fragments, final products, and glass crucible fragments. We conducted chemical and micro-structural analysis by LA-ICP-AES and SEM-EDS, determining that the glass recipe included feldspar, quartz, nitrate, fluorite, colorants, and probably calcite. These minerals match those in the glass recipes recorded in the historical literature. Glass making comprised at least two steps, namely the pre-melting of raw materials into a semi-finished glass, to which more fluxes were then added to make the final glass products or ingots.

In the quest for historical Lisbon through 17th century Millefiori glass

Being Lisbon one of the world’s most important trading port and a place where historical documents attest the presence of at least four glass furnaces working between the 16th and 17th centuries, the authors decided to investigate one of the most luxurious coeval glass decorative techniques (millefiori) found in Lisbon to try to understand the trade route and raw-materials provenance of these artefacts.For this work, two Lisbon archaeological contexts were selected: Largo do Chafariz de Dentro (LCD) and Santana Convent (LCS) due to their significant amount of interesting millefiori fragments (eight fragments) and the presence of production waste (one in LCD and three in LCS). The analysis, comparison and discussion of glass production waste (PW) and archaeological glass artefacts will be carried out for the first time.For this work, macroscopic and microscopic observations were combined with the chemical characterization of colourless and coloured glass to make the morphological characterization and to determine which raw materials were employed in its production. The chemical characterization was made by using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to obtain the major, minor and trace elements composition, including rare earth elements (REE).The chemical composition of the selected samples revealed that all the millefiori glasses are of soda-lime-silica type (part of them made with Levantine ashes and the other part with barilla) while the glass type of PW is was not attributed.Regarding the Lisbon millefiori glass fragments, there is a notable relation between the concentration of major components associated with the silica source, namely SiO2, Al2O3 and TiO2. Moreover, upon analysing the geochemical patterns exhibited by the production waste found in LCS context and comparing it with the pick-up glass fragments, a consistent trend emerges, implying that both were made by using either the identical silica source or, at the very least, a closely related silica source. For this reason, the possibility of a Portuguese local production may be proposed, especially when some decorative patterns are clearly from Portuguese inspiration (e.g. caravel and cross of Christ), while the authors admit that more data analysis is still required to prove this hypothesis.

Two Roman Glass Furnaces Discovered at Reşca-Romula (Romania)

Two Roman Glass Furnaces Discovered at Reşca-Romula (Romania)

Protection of NOx Sensors from Sulfur Poisoning in Glass Furnaces by the Optimization of a "SO2 Trap".

Electrochemical NOx sensors based on yttria-stabilized zirconia (YSZ) provide a reliable onboard way to control NOx emissions from glass-melting furnaces. The main limitation is the poisoning of this sensor by sulfur oxides (SOx) contained in the stream. To overcome this drawback, an "SO2 trap" with high SOx storage capacity and low affinity to NOx is required. Two CuO/BaO/SBA-15 traps with the same CuO loading (6.5 wt.%) and different BaO loadings (5 and 24.5 wt.%, respectively) were synthetized, thoroughly characterized and evaluated as SO2 traps. The results show that the 6.5%CuO/5%BaO/SBA-15 trap displays the highest SO2 adsorption capacity and can fully adsorb SO2 for a specific period of time, while additionally displaying a very low NO adsorption capacity. A suitable quantity of this material located upstream of the sensor could provide total protection of the NOx sensor against sulfur poisoning in glass-furnace exhausts.

Modelling of fresh properties and strength activity index with microstructure characterisation of ternary cement incorporating waste glass and granulated blast furnace slag

Research in innovative construction materials has focused on utilising supplementary materials in cementitious composites to promote sustainable development and reduce CO2 emissions. Within this context, this study aims to investigate the fresh properties and assess the pozzolanic activity of ternary blended cement by incorporating two industrial waste materials, namely waste glass (WG) and granulated blast furnace slag (GBS), as cement replacements up to 30%. A mixture design approach was employed for composition optimisation, and mathematical models were implemented to achieve this. XRD and SEM/EDS analyses were conducted to examine the structure and composition of the cementitious matrix. The results indicate that the setting time was prolonged compared to the reference mixture. Furthermore, based on the results of the SAI (Strength Activity Index) test, an acceptable level of strength development was demonstrated, confirming that WG and GBS possess the potential to replace cement while meeting the minimum strength requirements outlined in the specifications. Microstructure analyses revealed good adhesion between WGP, GGBS, and the cementitious binder. This research contributes to the development of eco-efficient binders that exhibit increased cement replacement ratios and qualities comparable to, or even superior to, traditional cement systems.

Glass production at Jalame, Israel: Process, composition and relationship to Roman glass in Europe

Following an initial micro-XRF assay, 42 samples of glass from the twentieth-century excavations of the fourth-century CE production site at Jalame, Israel, were selected and analysed by EPMA, with subsets for trace elements by LA-ICP-MS (n=29 samples) and for Hf isotopes by MC-ICP-MS (n=6). Comparison of major elements for ten samples originally measured in Brill (1988) was good, although the earlier SiO2 values are slightly high. Analyses of furnace debris and contaminated glass imply that glass furnaces were made of, or lined with a lime-rich material, leading to contamination by CaO, rather than Al2O3. This confirms that higher alumina contents measured for Jalame glass relative to Roman Mn-decolourised glass of first-third century Europe are significant and it is suggested that the source of the earlier Roman glass lies further North on the eastern Mediterranean coast.A wide range of trace elements are shown to have entered the glass with the addition of manganese, so caution should be exercised when interpreting trace element and isotopic data on glass with significant amounts of Mn, although the effects on REE and some of the lithophiles most often used in provenancing appear minor or insignificant in Jalame glass with MnO below 1.3 wt%. For example, the hafnium isotope composition of the Jalame material does not appear to have been significantly affected and falls within the previously determined Levantine range, distinguishable from Egyptian glass. Associated trace elements indicate that two Mn sources were exploited and this raises the possibility of further investigation of Mn sources in early glass production. The wide range of added manganese suggests problems in obtaining a homogeneous batch and it is suggested that (a) a single initially inhomogeneous furnace load melted to a range of colours, which were subsequently colour-sorted as chunks, and/or (b) the recycling of poorly fused manganese-decolourised glass into later manganese-free batches resulted in the observed variation.The cobalt pigment used was the high-nickel late antique type and allows the introduction of this source to be pushed back from the sixth to the fourth century CE. The use of antimony in glassmaking ceased at around the same time, and it is speculated that these changes were related.