Deactivation and regeneration of ZSM-5 zeolite in catalytic pyrolysis of plastic wastes

In this work, a study of the regeneration and reuse of ZSM-5 zeolite in the pyrolysis of a plastic mixture has been carried out in a semi-batch reactor at 440 °C. The results have been compared with those obtained with fresh-catalyst and in non-catalytic experiments with the same conditions. The use of fresh catalyst produces a significant change in both the pyrolysis yields and the properties of the liquids and gases obtained. Gases more rich in C3-C4 and H₂ are produced, as well as lower quantities of aromatic liquids if compared with those obtained in thermal decomposition. The authors have proved that after one pyrolysis experiment the zeolite loses quite a lot of its activity, which is reflected in both the yields and the products quality; however, this deactivation was found to be reversible since after regeneration heating at 550 °C in oxygen atmosphere, this catalyst recovered its initial activity, generating similar products and in equivalent proportions as those obtained with fresh catalyst.     

Hydrogen-rich fuel gas production from refuse plastic fuel pyrolysis and steam gasification

In this study, experimental conditions were optimized to maximize the production of hydrogen gas from refuse plastic fuel (RPF) by pyrolysis and steam gasification processes conducted in a laboratory-scale reactor. We carried out gasification using 10-g RPF samples at different temperatures (700°-1000°C) with and without steam. The effect of the amount of steam (0–0.25 g/min) for RPF steam gasification was also studied. The effect of K₂CO₃ as a catalyst on these processes was also investigated. Experimental results showed that the hydrogen gas yield increased with temperature; with respect to the gas composition, the hydrogen content increased mainly at the expense of other gaseous compounds, which highlights the major extension of secondary cracking reactions in the gaseous fraction at higher temperatures.     

Production of gaseous fuel from refuse plastic fuel via co-pyrolysis using low-quality coal and catalytic steam gasification

In this study, refuse plastic fuel (RPF) was copyrolyzed with low-quality coal and was gasified in the presence of a metal catalyst and steam. Some metal catalysts, such as Ni, NiO, and Mg, and mixtures of these with base promoters such as Al₂O₃ and Fe₂O₃ were employed in the pyrolysis and gasification processes to convert the synthesis gas into more valuable fuel gas. The operating temperatures for the pyrolysis and gasification were between 700° and 1000°C. The experimental parameters were the operating temperature, catalyst type, basic promoter type, and steam injection amount. Solid fuel samples (5 g) were fed into a semibatch-type quartz tube reactor when the reactor reached the designated temperature. The synthesis gas was analyzed by gas chromatography. The use of low-quality coal as fuel in co-pyrolysis with RPF was explored. For the co-pyrolysis of RPF and low-quality coal, the effectiveness of the catalysts for fuel gas production followed the order Mg > NiO > Ni. In catalytic gasification of RPF, the addition of Al₂O₃ seemed to reduce the activity of the corresponding catalysts Ni and Mg. The maximum fuel gas yield (92.6%) was attained when Mg/Fe₂O₃ was used in steam gasification at 1000°C.     

High-temperature thermal destruction of poultry derived wastes for energy recovery in Australia

The high-temperature thermal destruction of poultry derived wastes (e.g., manure and bedding) for energy recovery is viable in Australia when considering resource availability and equivalent commercial-scale experience in the UK. In this work, we identified and examined the opportunities and risks associated with common thermal destruction techniques, including: volume of waste, costs, technological risks and environmental impacts. Typical poultry waste streams were characterised based on compositional analysis, thermodynamic equilibrium modelling and non-isothermal thermogravimetric analysis coupled with mass spectrometry (TG–MS). Poultry waste is highly variable but otherwise comparable with other biomass fuels. The major technical and operating challenges are associated with this variability in terms of: moisture content, presence of inorganic species and type of litter. This variability is subject to a range of parameters including: type and age of bird, and geographical and seasonal inconsistencies. There are environmental and health considerations associated with combustion and gasification due to the formation of: NO_X, SO_X, H₂S and HCl gas. Mitigation of these emissions is achievable through correct plant design and operation, however, with significant economic penalty. Based on our analysis and literature data, we present cost estimates for generic poultry-waste-fired power plants with throughputs of 2 and 8 tonnes/h.     

Feasibility study for thermal treatment of solid tire wastes in Bangladesh by using pyrolysis technology

In this study on the basis of lab data and available resources in Bangladesh, feasibility study has been carried out for pyrolysis process converting solid tire wastes into pyrolysis oils, solid char and gases. The process considered for detailed analysis was fixed-bed fire-tube heating pyrolysis reactor system. The comparative techno-economic assessment was carried out in US$ for three different sizes plants: medium commercial scale (144 tons/day), small commercial scale (36 tons/day), pilot scale (3.6 tons/day). The assessment showed that medium commercial scale plant was economically feasible, with the lowest unit production cost than small commercial and pilot scale plants for the production of crude pyrolysis oil that could be used as boiler fuel oil and for the production of upgraded liquid-products.     

Characterization of char derived from various types of solid wastes from the standpoint of fuel recovery and pretreatment before landfilling

Carbonization is a kind of pyrolysis process to produce char from organic materials under an inert atmosphere. In this work, chars derived from various solid wastes were characterized from the standpoint of fuel recovery and pretreatment of waste before landfilling. Sixteen kinds of municipal and industrial solid wastes such as residential combustible wastes, non-combustible wastes, bulky wastes, construction and demolition wastes, auto shredder residue, and sludges were carbonized at 500 degrees C for 1h under nitrogen atmosphere. In order to evaluate the quality of char as fuel, proximate analysis and heating value were examined. The composition of raw waste had a significant influence on the quality of produced char. The higher the ratio of woody biomass in waste, the higher heating value of char produced. Moreover, an equation to estimate heating value of char was developed by using the weight fraction of fixed carbon and volatile matter in char. De-ashing and chlorine removal were performed to improve the quality of char. The pulverization and sieving method seems to be effective for separation of incombustibles such as metal rather than ash. Most char met a 0.5 wt% chlorine criterion for utilization as fuel in a shaft blast furnace after it was subjected to repeated water-washing. Carbonization could remove a considerable amount of organic matter from raw waste. In addition, the leaching of heavy metals such as chrome, cadmium, and lead appears to be significantly suppressed by carbonization regardless of the type of raw waste. From these results, carbonization could be considered as a pretreatment method for waste before landfilling, as well as for fuel recovery.     

Recovery of polypropylene and polyethylene from packaging plastic wastes without contamination of chlorinated plastic films by the combination process of wet gravity separation and ozonation

Wet gravity separation technique has been regularly practiced to separate the polypropylene (PP) and polyethylene (PE) (light plastic films) from chlorinated plastic films (CP films) (heavy plastic films). The CP films including poly vinyl chloride (PVC) and poly vinylidene chloride (PVDC) would float in water even though its density is more than 1.0 g/cm³. This is because films are twisted in which air is sometimes entrapped inside the twisted CP films in real existing recycling plant. The present research improves the current process in separating the PP and PE from plastic packaging waste (PPW), by reducing entrapped air and by increasing the hydrophilicity of the CP films surface with ozonation. The present research also measures the hydrophilicity of the CP films.In ozonation process mixing of artificial films up to 10 min reduces the contact angle from 78° to 62°, and also increases the hydrophilicity of CP films. The previous studies also performed show that the artificial PVDC films easily settle down by the same. The effect of ozonation after the wet gravity separation on light PPW films obtained from an actual PPW recycling plant was also evaluated. Although actual light PPW films contained 1.3% of CP films however in present case all the CP films were removed from the PPW films as a settled fraction in the combination process of ozonation and wet gravity separation. The combination process of ozonation and wet gravity separation is the more beneficial process in recovering of high purity PP and PE films from the PPW films.     

Optimization of process parameters using response surface methodology for maximum liquid yield during thermal pyrolysis of blend of virgin and waste high-density polyethylene

Journal of Material Cycles and Waste Management - The pyrolytic fuel generated by high-density polyethylene (HDPE) has the potential to replace fossil fuels as a primary source of energy. Thermal...     

Use of a low‐cost substrate in a continuous recirculation process to stimulate plumewide anaerobic dechlorination of chlorinated solvents

Over the past 20 years, significant time and money have been spent on better understanding and successfully applying bioremediation in the field. The results of these efforts provide a deeper un‐derstanding of aerobic and anaerobic microbial processes, the microbial species and environ‐mental conditions that are desirable for specific degradation pathways, and the limitations that may prevent full‐scale bioremediation from being successfully applied in heterogeneous subsur‐face environments. Numerous substrates have been identified as effective electron donors to stimulate anaerobic dechlorination of chlorinated ethenes, but methods of delivering these sub‐strates for in situ bioremediation (direct‐push injections, slug injections, high‐pressure injections, fracture wells, etc.) have yet to overcome the main limitation of achieving contact between these substrates and the contaminants. Therefore, although it is important (from a full‐scale remedia‐tion standpoint) to select an appropriate, low‐cost substrate that can be supplied in sufficient quantity to promote remediation of a large source area and its associated plume, it is equally im‐portant to ensure that the substrate can be delivered throughout the impacted plume zone. Failure to achieve substrate delivery and contact within the chlorinated solvent plume usually re‐sults in wasted money and limited remediation benefit. Bioremediation is a contact technology that cannot be effectively implemented on a large scale unless a method for rapidly delivering the low‐cost substrate across the entire source and plume areas is utilized. Unfortunately, many cur‐rent substrate delivery methods are not achieving sitewide distribution or treatment of the sorbed contaminant mass that exists in the organic fraction of a soil matrix. The following discussion sum‐marizes substrate delivery using an aggressive groundwater recirculation approach that can achieve plumewide contact between the contaminants and substrate, thus accelerating dechlori‐nation rates and shortening the overall remediation time frame. © 2006 Wiley Periodicals, Inc.     

A pilot plant two-phase anaerobic digestion system for bioenergy recovery from swine wastes and garbage

A pilot plant bioenergy recovery system from swine waste and garbage was constructed. A series of experiments was performed using swine feces (SF); a mixture of swine feces and urine (MSFU); a mixture of swine feces, urine and garbage (MSFUG); garbage and a mixture of urine and garbage (AUG). The system performed well for treating the source materials at a high organic loading rate (OLR) and short hydraulic retention time (HRT). In particular, the biogas production for the MSFUG was the highest, accounting for approximately 865-930Lkg(-1)-VS added at the OLR of 5.0-5.3kg-VSm(-3)day(-1) and the HRT of 9 days. The removal of VS was 67-75%, and that of COD was 73-74%. Therefore, co-digestion is a promising method for the recovery of bioenergy from swine waste and garbage. Furthermore, the results obtained from this study provide fundamental information for scaling up a high-performance anaerobic system in the future.     

Pyrolysis and catalytic pyrolysis as a recycling method of waste CDs originating from polycarbonate and HIPS

Pyrolysis appears to be a promising recycling process since it could convert the disposed polymers to hydrocarbon based fuels or various useful chemicals. In the current study, two model polymers found in WEEEs, namely polycarbonate (PC) and high impact polystyrene (HIPS) and their counterparts found in waste commercial Compact Discs (CDs) were pyrolysed in a bench scale reactor. Both, thermal pyrolysis and pyrolysis in the presence of two catalytic materials (basic MgO and acidic ZSM-5 zeolite) was performed for all four types of polymers. Results have shown significant recovery of the monomers and valuable chemicals (phenols in the case of PC and aromatic hydrocarbons in the case of HIPS), while catalysts seem to decrease the selectivity towards the monomers and enhance the selectivity towards other desirable compounds.     

Characteristics of liquid product from the pyrolysis of waste plastic mixture at low and high temperatures: influence of lapse time of reaction

Pyrolysis of a waste plastic mixture (high-density polyethylene: low-density polyethylene: polypropylene: polystyrene = 3:2:3:1) into a liquid product was carried out in a stirred semi-batch reactor at low (350 degrees C) and high (400 degrees C) temperatures. The effect of lapse time of reaction in the reactor and also degradation temperature on the characteristics of the liquid product from pyrolysis of the mixture was investigated. Liquid products were described by cumulative amount distribution, paraffin, olefin, naphthene and aromatic (PONA) distribution and molecular weight distribution. Their characteristic was quite differed with a lapse time of reaction and also at a low and high degradation temperatures, because of the different physicochemical properties of the plastic types in the mixture. With increase of lapse time of reaction, the order for the main products in PONA components obtained at 350 degrees C was firstly aromatic products and then olefin products, while at 400 degrees C the order was firstly aromatic products, then olefin products and finally paraffin products. The experiments also showed from the molecular weight distribution of liquid PONA components that the paraffin and olefin products had a wide distribution by mainly random scission of polymer, but in the case of olefin products were produced by an end-chain scission mechanism as well as random scission mechanism, as evidenced by much more light olefin products. This phenomenon was evident at a higher degradation temperature. Also, both the light olefin and naphthene products with a molecular weight of around 120, as a main product, showed a similar trend as a function of lapse time, which had a maximum fraction at 343 min (at 350 degrees C) and 83 min (at 400 degrees C). Among PONA components, the highest concentrations of aromatic products were obtained with a molecular weight of around 100 at the fastest lapse time of reaction, regardless of degradation temperature. It was concluded that the characteristics of liquid product on the pyrolysis of plastic mixtures were strongly influenced by lapse time of reaction and degradation temperature.     

Study of the solubility and stability of polystyrene wastes in a dissolution recycling process

Dissolution with suitable solvents is one of the cheapest and more efficient processes for polystyrene waste management. In this work the solubility of polystyrene foams in several solvents benzene, toluene, xylene, tetrahydrofuran, chloroform, 1,3-butanediol, 2-butanol, linalool, geraniol, d-limonene, p-cymene, terpinene, phellandrene, terpineol, menthol, eucalyptol, cinnamaldheyde, nitrobenzene, N,N-dimethylformamide and water has been determined.Experimental results have shown that to develop a “green process” the constituents of essential oils, d-limonene, p-cymene, terpinene, phellandrene, are the most appropriate solvents. The action of these solvent does not produce any degradation of polymer chains. The solubility of the polymer in the mentioned solvents at different temperatures has been investigated. The solvent can be easily recycled by distillation.     

Cogeneration from thermal treatment of selected municipal solid wastes. A stoichiometric model building for the case study on Palermo

This paper aims to calculate the energetic and environmental effects of an integrated solid waste management system in Palermo, Italy. In particular, the thermal treatment of Municipal Solid Waste (MSW) with energy recovery is assessed. The current characterization at the local scale is taken into account. Two different options of collection are taken into account: (1) unselected wastes; and (2) sorted collection, according to the current Italian regulation. Combustion process is analyzed and the following features are calculated: (1) stoichiometric content of air and air excess; and (2) temperature and enthalpy of flue gases. Energy recovery is performed in the hypothesis of Hirn cycle both with steam condensation to produce only power, and with bleeding cycle for the combined production of power and thermal energy. Total electric efficiency is assumed as representative index of the technological level of the assessed plant. Results show that the thermal treatment of selected MSW, associated with a cogenerative recovery of energy, represents a relevant sustainable strategy of waste valorization as an alternative to fossil fuels.     

Integrated process development for the recovery of Europium and Yttrium from waste fluorescent powder

Journal of Material Cycles and Waste Management - Fluorescent powder plays an important role in the modern electronic lighting products. During the production of electronic lighting products, a...     

Characteristics of products and PCDD/DF emissions from a pyrolysis process of urethane/styrofoam waste from electrical home appliances

A plastic fraction consisting mainly of polyurethane/styrofoam waste is generated after separating valuable spare parts and metals from used electrical home appliances. In Korea, such waste is currently incinerated in cement kilns or is landfilled. However, owing to its high volatile matter content, conversion into gaseous or liquid pyrolysis products is a preferable alternative. A pyrolysis process of polyurethane and styrofoam waste from electrical home appliances was evaluated by characterizing the products generated at 500°–800°C. The para meters determined were the yields of gas, oil, and char; the characteristics of the remaining char; and the con centration of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzo-furans in the product gas. As expected, the char yield decreased at higher temperatures, whereas gas and oil yields showed increasing tendency. The oil products could be used as storable fuels with a calorific value of 6000–8000 kcal/kg. Fine pores were observed in the char. The adsorption and decolorizing ability of the char were almost the same as those of activated carbon, so that pyrolysis char has potential for use as a sorbent. Further feasibility studies will be needed before utilizing pyrolysis technology to recover either fuels or usable products from polyurethane/styrofoam waste.     

Phosphorus recovery from secondary effluent and side-stream liquid in a sewage treatment plant using zirconium-loaded saponified orange waste

Zirconium was loaded onto orange waste, a cheap and available agricultural waste in Japan, to investigate the feasibility of its utilization for phosphorus recovery from secondary effluent and side-stream liquid, which contain 5.9 and 68.2 mg/dm³ phosphorus, respectively. The phosphorus removal from side-stream liquid by using zirconium-loaded saponified orange waste (Zr-SOW) gel increased with an increasing solid/liquid ratio, and it was found that Zr-SOW gel showed better performance than zirconium ferrite. The prepared adsorbent was effective for phosphorus removal and exhibited a reasonably high adsorption capacity, twice than that of zirconium ferrite. The secondary effluent was treated in a column packed with Zr-SOW gel, and an dynamic adsorption capacity of 1.3 mol-P/kg was attained. The adsorbed phosphorus from the column was successfully eluted as a concentrated form by using a small amount of 0.2 M NaOH. Throughout the elution process, zirconium was not leaked from the adsorption gel.     

核电站温排水环境影响研究方法调查评价

核电站的温排水是其运行过程中对周围环境影响的重要因素之一。通过对核电站温排水环境影响研究方法的调查和研究,分析各种调查、研究方法的特点,给出初步环境影响方法评价结论和建议。     

Experimental and numerical calculations of waste R-134a thermal decomposition for energy and fluorine material recovery

Considering the global warming potential of R-134a (C₂H₂F₄) with the substantial generation of this refrigerant as waste material in various industrial sectors, the development of proper thermal destruction method of R-134a is of great practical significance. For this, experiment and numerical calculations have initially made for a tubular-type furnace in order to figure out the basic combustion characteristics of R-134a. A series of experimental investigations for the thermal decomposition of R-134a have been made as a function of wall temperature of tubular furnace and important reacting species such as O₂ and H₂O necessary for the decomposition of C₂H₂F₄ into HF, CO₂ and H₂O. In general, the thermal decomposition of R-134a is successfully made for the condition of temperature above 800 °C with the supply of stoichiometric amount of O₂ and these results are well agreed with numerical prediction. And this information is employed for the simulation of a full-scale, practical incinerator used for the CDM project. For this, numerical investigation has been made for a commercial-scale incinerator using CH₄–air flames for the proper destruction C₂H₂F₄ together with the control of pollutants such as CO and NO. In general, the destruction rate of C₂H₂F₄ appears more than 99.99 % and the generation of CO and NO species appears rather sensitive to the operational condition such as amount of water vapor. The numerical method of HFCs (hydrofluorocarbons) thermal treatment shows high possibility as a viable tool for the proper design and optimal determination of the operational condition for a HFCs incinerator.     

Potential utilization of rubberwood flour and sludge waste from natural rubber manufacturing process as reinforcement in plastic composites

Journal of Material Cycles and Waste Management - The present study aims to evaluate and compare the potential of rubberwood flour (RWF) and sludge waste from manufacturing process of the...