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1.
The pulp and paper industry is placed in a unique position as biomass used as feedstock is now in increasingly high demand from the energy sector. Increased demand for biomass increases pressure on the availability of this resource, which might strengthen the need for recycling of paper. In this study, we calculate the energy use and carbon dioxide emissions for paper production from three pulp types. Increased recycling enables an increase in biomass availability and reduces life-cycle energy use and carbon dioxide emissions. Recovered paper as feedstock leads to lowest energy use (22 GJ/t) and CO2 emissions (−1100 kg CO2/t) when biomass not used for paper production is assumed to be converted into bio-energy. Large differences exist between paper grades in e.g. electricity and heat use during production, fibre furnish, filler content and recyclability. We found large variation in energy use over the life-cycle of different grades. However, in all paper grades, life-cycle energy use decreases with increased recycling rates and increased use of recovered fibres. The average life-cycle energy use of the paper mix produced in The Netherlands, where the recycling rate is approximately 75%, is about 14 GJ/t. This equals CO2 savings of about 1 t CO2/t paper if no recycled fibres would be used.  相似文献   

2.
Treatment of a basic dye, methylene blue, by electrochemical oxidation, fly ash adsorption, and combined electrochemical oxidation-fly ash adsorption was compared. Methylene blue at 100 mg L?1 was used in this study. The toxicity was also monitored by the Vibrio fischeri light inhibition test.When electrochemical oxidation was used, 99% color and 84% COD were removed from the methylene blue solution in 20 min at a current density of 428 A m?2, NaCl of 1000 mg L?1, and pH0 of 7. However, the decolorized solution showed high toxicity (100% light inhibition).For fly ash adsorption, a high dose of fly ash (>20,000 mg L?1) was needed to remove methylene blue, and the Freundlich isotherm described the adsorption behavior well.In the combined electrochemical oxidation-fly ash adsorption treatment, the addition of 4000 mg L?1 fly ash effectively reduced intermediate toxicity and decreased the COD of the electrochemical oxidation-treated methylene blue solution. The results indicated that the combined process effectively removed color, COD, and intermediate toxicity of the methylene blue solution.  相似文献   

3.
A novel CO2 separation concept is described wherein the enzyme carbonic anhydrase (CA) is used to increase the overall rate of CO2 absorption after which hydrated CO2 reacts with regenerable amine-bearing polyacrylamide buffering beads (PABB). Following saturation of the material's immobilized tertiary amines, CA-bearing carrier water is separated and recycled to the absorption stage while CO2-loaded material is thermally regenerated. Process application of this concept would involve operation of two or more columns in parallel with thermal regeneration with low-pressure steam taking place after the capacity of a column of amine-bearing polymeric material was exceeded. PABB CO2-bearing capacity was evaluated by thermogravimetric analysis (TGA) for beads of three acrylamido buffering monomer ingredient concentrations: 0 mol/kg bead, 0.857 mol/kg bead, and 2 mol/kg bead. TGA results demonstrate that CO2-bearing capacity increases with increasing PABB buffering concentration and that up to 78% of the theoretical CO2-bearing capacity was realized in prepared PABB samples (0.857 mol/kg recipe). The highest observed CO2-bearing capacity of PABB was 1.37 mol of CO2 per kg dry bead. TGA was also used to assess the regenerability of CO2-loaded PABB. Preliminary results suggest that CO2 is partially driven from PABB samples at temperatures as low as 55 °C, with complete regeneration occurring at 100 °C. Other physical characteristics of PABB are discussed. In addition, the effectiveness of bovine carbonic anhydrase for the catalysis of CO2 dissolution is evaluated. Potential benefits and drawbacks of the proposed process are discussed.  相似文献   

4.
Fenton oxidation pretreatment was investigated for enhancement of biodegradability of wastewater sludge (WWS) which was subsequently used as substrate for the production of value- added products. The Response surface method with fractional factorial and central composite designs was applied to determine the effects of Fenton parameters on solubilization and biodegradability of sludge and the optimization of the Fenton process. Maximum solubilization and biodegradability were obtained as 70% and 74%, respectively at the optimal conditions: 0.01 ml H2O2/g SS, 150 [H2O2]0/[Fe2+]0, 25 g/L TS, at 25 °C and 60 min duration. Further, these optimal conditions were tested for the production of a value added product, Bacillus thuringiensis (Bt) which is being used as a biopesticide in the agriculture and forestry sector. It was observed that Bt growth using Fenton oxidized sludge as a substrate was improved with a maximum total cell count of 1.63 × 109 CFU ml?1 and 96% sporulation after 48 h of fermentation. The results were also tested against ultrasonication treatment and the total cell count was found to be 4.08 × 108 CFU ml?1 with a sporulation of 90%. Hence, classic Fenton oxidation was demonstrated to be a rather more promising chemical pre-treatment for Bt - based biopesticide production using WWS when compared to ultrasonication as a physical pre-treatment.  相似文献   

5.
The chilled ammonia process absorbs the CO2 at low temperature (2–10 °C). The heat of absorption of carbon dioxide by ammonia is significantly lower than for amines. In addition, degradation problems can be avoided and a high carbon dioxide capacity is achieved. Hence, this process shows good perspectives for decreasing the heat requirement. However, a scientific understanding of the processes is required. The thermodynamic properties of the NH3–CO2–H2O system were described using the extended UNIQUAC electrolyte model developed by Thomsen and Rasmussen in a temperature range from 0 to 110 °C and pressure up to 100 bars. The results show that solid phases consisting of ammonium carbonate and bicarbonate are formed in the absorber. The heat requirements in the absorber and in the desorber have been studied. The enthalpy calculations show that a heat requirement for the desorber lower than 2 GJ/ton CO2 can be reached.  相似文献   

6.
The environmental impacts of food waste management strategies and the effects of energy mix were evaluated using a life cycle assessment model, EASEWASTE. Three different strategies involving landfill, composting and combined digestion and composting as core technologies were investigated. The results indicate that the landfilling of food waste has an obvious impact on global warming, although the power recovery from landfill gas counteracts some of this. Food waste composting causes serious acidification (68.0 PE) and nutrient enrichment (76.9 PE) because of NH3 and SO2 emissions during decomposition. Using compost on farmland, which can marginally reduce global warming (−1.7 PE), acidification (−0.8 PE), and ecotoxicity and human toxicity through fertilizer substitution, also leads to nutrient enrichment as neutralization of emissions from N loss (27.6 PE) and substitution (−12.8 PE). A combined digestion and composting technology lessens the effects of acidification (−12.2 PE), nutrient enrichment (−5.7 PE), and global warming (−7.9 PE) mainly because energy is recovered efficiently, which decreases emissions including SO2, Hg, NOx, and fossil CO2 during normal energy production. The change of energy mix by introducing more clean energy, which has marginal effects on the performance of composting strategy, results in apparently more loading to acidification and nutrient enrichment in the other two strategies. These are mainly because the recovered energy can avoid fewer emissions than before due to the lower background values in power generation. These results provide quantitative evidence for technical selection and pollution control in food waste management.  相似文献   

7.
A column of silica gel was employed to contact water with flue gas (CO2/N2) mixture to assess if CO2 can be separated by hydrate crystallization. Three different silica gels were used. One with a pore size of 30 nm (particle size 40–75 μm) and two with a pore size of 100 nm and particle sizes of 40–75 and 75–200 μm respectively. The observed trends indicate that larger pores and particle size increase the gas consumption, CO2 recovery, separation factor and water conversion to hydrate. Thus, the gel (gel #3) with the larger particle size and larger pore size was chosen to carry out experiments with concentrated CO2 mixtures and for experiments in the presence of tetrahydrofuran (THF), which itself is a hydrate forming substance. Addition of THF reduces the operating pressure in the crystallizer but it also reduces the gas uptake. Gel #3 was also used in experiments with a fuel gas (CO2/H2) mixture in order to recover CO2 and H2. It was found that the gel column performs as well as a stirred reactor in separating the gas components from both flue gas and fuel gas mixtures. However, the crystallization rate and hydrate yield are considerably enhanced in the former. Finally the need for stirring is eliminated with the gel column which is enormously beneficial economically.  相似文献   

8.
Capture and storage of CO2 from fossil fuel fired power plants is drawing increasing interest as a potential method for the control of greenhouse gas emissions. An optimization and technical parameter study for a CO2 capture process from flue gas of a 600 MWe bituminous coal fired power plant, based on absorption/desorption process with MEA solutions, using ASPEN Plus with the RADFRAC subroutine, was performed. This optimization aimed to reduce the energy requirement for solvent regeneration, by investigating the effects of CO2 removal percentage, MEA concentration, lean solvent loading, stripper operating pressure and lean solvent temperature.Major energy savings can be realized by optimizing the lean solvent loading, the amine solvent concentration as well as the stripper operating pressure. A minimum thermal energy requirement was found at a lean MEA loading of 0.3, using a 40 wt.% MEA solution and a stripper operating pressure of 210 kPa, resulting in a thermal energy requirement of 3.0 GJ/ton CO2, which is 23% lower than the base case of 3.9 GJ/ton CO2. Although the solvent process conditions might not be realisable for MEA due to constraints imposed by corrosion and solvent degradation, the results show that a parametric study will point towards possibilities for process optimisation.  相似文献   

9.
The injection of CO2 at the Ketzin storage site and the chemical detection of its arrival in the observation well allowed testing of different numerical simulation codes. ECLIPSE 100 (E100, black-oil simulator), ECLIPSE 300 (E300, compositional CO2STORE) and MUFTE-UG were used for predictive modelling applying a constant injection rate of 1 kg s?1 CO2 and for a history match applying the actual variable injection rate which ranged from 0 to 0.7 kg s?1 and averaged 0.23 kg s?1. The geological model applied, is based on all available geophysical and geological information and has been the same for all programs.The results of the constant injection regime show a good agreement among the programs with a discrepancy of 21–33% for the CO2 arrival times. However, it is determined from the comparison of the cumulative mass of CO2 at the time of CO2 arrival that the injection regime is an important factor for the accurate prediction of CO2 migration within a saline aquifer. Comparing the actual variable injection regime with the simulations applying a constant injection rate the results are relatively inaccurate.Regarding the actual variable injection regime, which was evaluated using all three simulators, the computational results show a good agreement with the data actually measured at the first observation well. Here, the calculated arrival times exceeded the actual ones by 8.1% (E100), 9.2% (E300) and 17.7% (MUFTE-UG).It can be concluded that irrespective of the deviations of the simulations, due to combinations of different codes and slight differences in input parameters, all three programs are well equipped to give a reliable estimate of the arrival of CO2. Deviations in the results mainly occur due to different input data and grid size choices done by the different modelling teams working independently of each other. Deviations of the simulations results compared to the actual CO2 arrival time result from uncertainties in the implementation of the geological model, which was set up based on well log data and analogue studies.  相似文献   

10.
Methodology is presented for a first-order regional-scale estimation of CO2 storage capacity in coals under sub-critical conditions, which is subsequently applied to Cretaceous-Tertiary coal beds in Alberta, Canada. Regions suitable for CO2 storage have been defined on the basis of groundwater depth and CO2 phase at in situ conditions. The theoretical CO2 storage capacity was estimated on the basis of CO2 adsorption isotherms measured on coal samples, and it varies between ∼20 kt CO2/km2 and 1260 kt CO2/km2, for a total of approximately 20 Gt CO2. This represents the theoretical storage capacity limit that would be attained if there would be no other gases present in the coals or they would be 100% replaced by CO2, and if all the coals will be accessed by CO2. A recovery factor of less than 100% and a completion factor less than 50% reduce the theoretical storage capacity to an effective storage capacity of only 6.4 Gt CO2. Not all the effective CO2 storage capacity will be utilized because it is uneconomic to build the necessary infrastructure for areas with low storage capacity per unit surface. Assuming that the economic threshold to develop the necessary infrastructure is 200 kt CO2/km2, then the CO2 storage capacity in coal beds in Alberta is greatly reduced further to a practical capacity of only ∼800 Mt CO2.  相似文献   

11.
Concentrated, aqueous piperazine (PZ) is a novel solvent for carbon dioxide (CO2) capture by absorption/stripping. One of the major advantages of PZ is its resistance to thermal degradation and oxidation.At 135 and 150 °C, 8 m PZ is up to two orders of magnitude more resistant to thermal degradation than 7 m monoethanolamine (MEA). After 18 weeks at 150 °C, only 6.3% of the initial PZ was degraded, yielding an apparent first order rate constant for amine loss of 6.1 × 10?9 s?1. PZ was the most resistant amine tested, with the other screened amines shown in order of decreasing resistance: 7 m 2-amino-2-methyl-1-propanol, 7 m Diglycolamine®, 7 m N-(2-hydroxyethyl)piperazine, 7 m MEA, 8 m ethylenediamine, and 7 m diethylenetriamine. Thermal resistance allows the use of higher temperatures and pressures in the stripper, potentially leading to overall energy savings.Concentrated PZ solutions demonstrate resistance to oxidation compared to 7 m MEA solutions. Experiments investigating metal-catalyzed oxidation found that PZ solutions were 3–5 times more resistant to oxidation than MEA. Catalysts tested were 1.0 mM iron (II), 4.0–5.0 mM copper (II), and a combination of stainless steel metals (iron (II), nickel (II), and chromium (III)). Inhibitor A reduced PZ degradation catalyzed by iron (II) and copper (II).  相似文献   

12.
The present work is a study to evaluate ionic liquids as a potential solvent for post-combustion CO2 capture. In order to enhance the absorption performance of a CO2 capture unit, different ionic liquids have been designed and tested. The main goal was to get a comparison between a reference liquid and selected ionic liquids. As the reference, a solution of 30 w% monoethanolamine (MEA) and water was used. A large range of different pure and diluted ionic liquids was tested with a special screening process to gain general information about the CO2 absorption performance. Based on these results, a 60 w% ionic liquid solution in water was selected and the vapour–liquid equilibrium was measured experimentally between 40 °C and 110 °C. From these curves the enthalpy of absorption for capturing CO2 into the ionic liquid was determined. With these important parameters one is able to calculate the total energy demand for stripping of CO2 from the loaded solvent for comparison of the ionic liquid based solvent with the reference MEA solvent. The energy demand of this 60 w% ionic liquid is slightly lower than that of the reference solution, resulting in possible energy savings between 12 and 16%.  相似文献   

13.
With the pavement industry adopting sustainable practices to align itself with the global notion of habitable environments, there has been growing use of life-cycle assessment (LCA). A hybrid LCA was used to analyze the environmental footprint of using a reclaimed asphalt pavement (RAP) content in asphalt binder mixtures. The analysis took into consideration the material, construction, and maintenance and rehabilitation phases of the pavement life cycle. The results showed significant reductions in energy consumption and greenhouse gas (GHG) emissions with an increase in RAP content. The contribution of the construction phase to the GHGs and energy consumption throughout pavement life cycle is minimal. Feedstock energy, though not consequential when comparing asphalt mixtures only, has a significant impact on total energy. Based on LCA analysis performed for various performance scenarios, breakeven performance levels were identified for mixtures with RAP. The study highlighted the importance of achieving equivalent field performance for mixtures with RAP and virgin mixtures.  相似文献   

14.
Chemical-Looping Combustion (CLC) is an emerging technology for CO2 capture because separation of this gas from the other flue gas components is inherent to the process and thus no energy is expended for the separation. Natural or refinery gas can be used as gaseous fuels and they may contain different amounts of light hydrocarbons. This paper presents the combustion results obtained with a Cu-based oxygen carrier using mixtures of CH4 and light hydrocarbons (LHC) (C2H6 and C3H8) as fuel. The effect on combustion efficiency of the fuel reactor temperature, solid circulation flow rate and gas composition was studied in a continuous CLC plant (500 Wth). Full combustions were reached at 1073 and 1153 K working at oxygen to fuel ratios, ? higher than 1.5 and 1.2 respectively. Unburnt hydrocarbons were never detected at any experimental conditions at the fuel reactor outlet. Carbon formation can be avoided working at 1153 K or at ? values higher than 1.5 at 1073 K. After 30 h of continuous operation, the oxygen carrier exhibited an adequate behavior regarding attrition and agglomeration. It can be concluded that no special measures should be taken in a CLC process with Cu-based OC with respect to the presence of LHC in the fuel gas.  相似文献   

15.
Amorphous silicon (a-Si:H)-based solar cells have the lowest ecological impact of photovoltaic (PV) materials. In order to continue to improve the environmental performance of PV manufacturing using proposed industrial symbiosis techniques, this paper performs a life cycle analysis (LCA) on both conventional 1-GW scaled a-Si:H-based single junction and a-Si:H/microcrystalline-Si:H tandem cell solar PV manufacturing plants and such plants coupled to silane recycling plants. Both the energy consumed and greenhouse gas emissions are tracked in the LCA, then silane gas is reused in the manufacturing process rather than standard waste combustion. Using a recycling process that results in a silane loss of only 17% instead of conventional processing that loses 85% silane, results in an energy savings of 81,700 GJ and prevents 4400 tons of CO2 from being released into the atmosphere per year for the single junction plant. Due to the increased use of silane for the relatively thick microcrystalline-Si:H layers in the tandem junction plants, the savings are even more substantial – 290,000 GJ of energy savings and 15.6 million kg of CO2 eq. emission reductions per year. This recycling process reduces the cost of raw silane by 68%, or approximately $22.6 million per year for a 1-GW a-Si:H-based PV production facility and over $79 million per year for tandem manufacturing. The results are discussed and conclusions are drawn about the technical feasibility and environmental benefits of silane recycling in an eco-industrial park centered around a-Si:H-based PV manufacturing plants.  相似文献   

16.
Following the feasibility study of sour compression process as a novel purification method of producing NOx-free, SO2-free oxyfuel-derived CO2 using actual fluegas, in this paper, we present the study of the individual reactions taking place in the process in a controlled environment. We have previously showed that an increase of NO/NO2 concentration in the inlet stream is beneficial for SO2 removal as NO2 promotes SO2 oxidation and the further removal as liquid acid. In this study we show that the reaction SO2 + NO2  SO3 + NO does not take place significantly in the absence of liquid water at a range of conditions relevant to the sour compression process. When liquid water is present, SO2 is oxidised by NO2 regenerating NO with the rate of conversion of SO2 being dependent on the acid concentration in the liquid. The formation of small liquid droplets where very low levels of pH (?0) can be reached is shown to be of great importance to the SO2 + NO2 conversion process.  相似文献   

17.
MEA solutions were subjected to oxidative degradation at both low and high gas rates. Solutions were degraded with 100 mL/min of 98%O2/2%CO2 with mass transfer achieved by vortexing. Solutions were analyzed for degradation products by IC and HPLC. In a parallel apparatus 7.5 L/min of 15%O2/2%CO2 was sparged through solution, with additional mass transfer achieved by vortexing. A Fourier Transform Infrared (FTIR) analyzer collected continuous gas-phase data on volatile products.Hydroxyethyl-formamide (HEF) and hydroxyethylimidazole (HEI) are the major liquid-phase oxidation products. In the presence of Fe2+ and Cu2+, HEF, HEI, and MEA losses increase by a factor of 3 compared to Fe2+ alone. Cr3+ and Ni2+, two metals present in stainless steel alloys, resulted in MEA losses that are 55% greater. In terms of oxidative degradation potential (greatest to lowest): Cu2+ > Cr3+/Ni2+ > Fe2+ > V5+.Inhibitor A reduces the formation of known products by 90% when catalyzed by Fe2+ and Cu2+ and by 99% with Cr3+/Ni2+. Inhibitor B reduces product rates by 97% and MEA losses by 75%, while a 100:1 ratio of EDTA to Fe2+ completely inhibits oxidation.  相似文献   

18.
Industrial Combined Heat and Power plants (CHPs) are often operated at partial load conditions. If CO2 is captured from a CHP, additional energy requirements can be fully or partly met by increasing the load. Load increase improves plant efficiency and, consequently, part of the additional energy consumption would be offset. If this advantage is large enough, industrial CHPs may become an attractive option for CO2 capture and storage CCS. We therefore investigated the techno-economic performance of post-combustion CO2 capture from small-to-medium-scale (50–200 MWe maximum electrical capacity) industrial Natural Gas Combined Cycle- (NGCC-) CHPs in comparison with large-scale (400 MWe) NGCCs in the short term (2010) and the mid-term future (2020–2025). The analyzed system encompasses NGCC, CO2 capture, compression, and branch CO2 pipeline.The technical results showed that CO2 capture energy requirement for industrial NGCC-CHPs is significantly lower than that for 400 MWe NGCCs: up to 16% in the short term and up to 12% in the mid-term future. The economic results showed that at low heat-to-power ratio operations, CO2 capture from industrial NGCC-CHPs at 100 MWe in the short term (41–44 €/tCO2 avoided) and 200 MWe in the mid-term future (33–36 €/tCO2 avoided) may compete with 400 MWe NGCCs (46–50 €/tCO2 avoided short term, 30–35 €/tCO2 avoided mid-term).  相似文献   

19.
Studies of the kinetics of sulfur dioxide (SO2)- and oxygen (O2)-induced degradation of aqueous monoethanolamine (MEA) during the absorption of carbon dioxide (CO2) from flue gases derived from coal- or natural gas-fired power plants were conducted as a function of temperature and the liquid phase concentrations of MEA, O2, SO2 and CO2. The kinetic data were based on the initial rate which shows the propensity for amine degradation and obtained under a range of conditions typical of the CO2 absorption process (3–7 kmol/m3 MEA, 6% O2, 0–196 ppm SO2, 0–0.55 CO2 loading, and 328–393 K temperature). The results showed that an increase in temperature and the concentrations of MEA, O2 and SO2 resulted in a higher MEA degradation rate. An increase in CO2 concentration gave the opposite effect. A semi-empirical model based on the initial rate, ?rMEA = {6.74 × 109 e?(29,403/RT)[MEA]0.02([O]2.91 + [SO2]3.52)}/{1 + 1.18[CO2]0.18} was developed to fit the experimental data. With the higher order of reaction, SO2 has a higher propensity to cause MEA to degrade than O2. Unlike previous models, this model shows an improvement in that any of the parameters (i.e. O2, SO2, and CO2) can be removed without affecting the usability of the model.  相似文献   

20.
While the demand for reduction in CO2 emission is increasing, the cost of the CO2 capture processes remains a limiting factor for large-scale application. Reducing the cost of the capture system by improving the process and the solvent used must have a priority in order to apply this technology in the future. In this paper, a definition of the economic baseline for post-combustion CO2 capture from 600 MWe bituminous coal-fired power plant is described. The baseline capture process is based on 30% (by weight) aqueous solution of monoethanolamine (MEA). A process model has been developed previously using the Aspen Plus simulation programme where the baseline CO2-removal has been chosen to be 90%. The results from the process modelling have provided the required input data to the economic modelling. Depending on the baseline technical and economical results, an economical parameter study for a CO2 capture process based on absorption/desorption with MEA solutions was performed.Major capture cost reductions can be realized by optimizing the lean solvent loading, the amine solvent concentration, as well as the stripper operating pressure. A minimum CO2 avoided cost of € 33 tonne−1 CO2 was found for a lean solvent loading of 0.3 mol CO2/mol MEA, using a 40 wt.% MEA solution and a stripper operating pressure of 210 kPa. At these conditions 3.0 GJ/tonne CO2 of thermal energy was used for the solvent regeneration. This translates to a € 22 MWh−1 increase in the cost of electricity, compared to € 31.4 MWh−1 for the power plant without capture.  相似文献   

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