Energy Conversion Law of Refuse Gasifi cation/Incineration in Low-Oxygen Plateau Areas—A Case Study of Lhasa,China

Combusting refuse for energy production is promising for their treatment and disposal. However, because of geographical constraints, there has not been a stable model for the energy utilization of refuse in low-oxygen plateau areas. This paper took Lhasa as an example to conduct gasification and incineration experiments on local representative combustible refuse,and relevant energy conversion laws were investigated. Results showed that under gasification and incineration modes, the energy conversion rate of any component of refuse can reach 75% and 85% in low-oxygen plateau areas at temperatures of 450 and 650 ℃, respectively, which were 5%–10% lower than those in plain areas. The regional distribution of energy conversion of refuse in Lhasa showed that the energy conversion rate under the gasification mode was 3%–5% lower than that of the incineration mode at 450 and 650 ℃. In terms of temperature, the energy conversion rates of refuse were 5%–10% lower at 450 ℃ than those at 650 ℃, but an energy conversion rate of more than 85% can still be achieved. Thus, gasification, incineration, or gasification-assisted secondary incineration at temperatures of at least 450 ℃ is suitable for energy recovery of refuse in low-oxygen plateau areas.

Numerical simulation on the fluidized bed gasification and CaO dechlorination of refuse derived fuel

A three-dimensional numerical model verified by previous experimental data is developed to simulate the fluidized bed gasification of refuse derived fuel （RDF）. The CaO dechlorination model obtained by the thermal gravity analysis （TGA） is coupled to investigate the process of CaO dechlorination. An Eulerian-Eulerian method is adopted to simulate the gas-solid flow and self-developed chemical reaction modules are used to simulate chemical reactions. Flow patterns, gasification results and dechlorination efficiency are obtained by numerical simulation. Meanwhile, simulations are performed to evaluate the effects of Ca/Cl molar ratio and temperature on dechlorination efficiency. The simulation results show that the presence of bubbles in the gasifier lowers the CaO dechlorination efficiency. Increasing the Ca/Cl molar ratio can enhance the dechlorination efficiency. However, with the temperature increasing, the dechlorination efficiency increases initially and then decreases. The optimal Ca/Cl molar ratio is in the range of 3. 0 to 3. 5 and the optimal temperature is 923K.

The Optimal Plan for WTE Plants in an Urban Area Considering Refuse Collection and FIT

Burnable municipal solid waste is disposed sanitarily at incinerator plants, which leads decrease of environmental load. At the same time, WTE （waste-to-energy） is realized as recovery of energy. WTE, however, has weakness of low generation efficiency and output in Japan due to smaller capacity of incinerator plants. To overcome above weakness, high efficient WTE is necessary with total integration and scaling up of incinerator plants. In addition FIT （feed-in tariff） has been started recently in Japan. When planning, we must consider totally both cost of incinerator plants and cost of refuse collection which is important role for the waste disposal. The planning method whose target is an urban area has formulated in this study. Considering the situation of the decrease trend of refuse volume and the strict finance condition of a local government, so that the proposed method is very effective.

Three-stage aged refuse biofilter for the treatment of landfill leachate

A field-scale aged refuse （AR） biofilter constructed in Shanghai Refuse Landfill, containing about 7000 m^3 aged refuse inside, was evaluated for its performance in the treatment of landfill leachate. This AR biofilter can be divided into three stages and can manage 50 m^3 landfill leachate per day. The physical, chemical, and biological characteristics of AR were analyzed for evaluating the AR biofilter as leachate treatment host. The results revealed that over 87.8%-96.2% of COD and 96.9%-99.4% of ammonia nitrogen were removed by the three-stage AR biofilter when the infiuent leachate COD and ammonia nitrogen concentration were in the range 5478-10842 mg/L and 811-1582 mg/L, respectively. The final effluent was inodorous and pale yellow with COD and ammonia nitrogen below 267-1020 mg/L and 6-45 mg/L, respectively. The three-stage AR biofilter had efficient nitrification but relative poor denitrification capacity with a total nitrogen （TN） removal of 58%-73%. The external temperature of AR biofilter did not influence the total ammonia nitrogen removal significantly. It was concluded that the scale-up AR biofilter can work very well and can be a promising technology for the treatment of landfill leachate.

Excavation and characterization of refuse in closed landfill

Refuse in landfills becomes stabilized as organic matter in refuse degrades and soluble inorganic substances dissolve during their long term stabilization process. In this paper, this process is also referred to as mineralization process and the resultant stabilized refuse referred to as aged refuse. Aged refuse contains a wide spectrum and huge quantity of microorganisms with strong decomposition capability for refractory organic matter present in some wastewater such as leachate. In this study, aged refuse excavated from 2 to 10 years old closed landfill compartments in Shanghai Refuse Landfill is characterized in terms of particulate distribution by screening, total nitrogen, total phosphorus, biodegradable matter. The approaches for redevelopment of both land and aged refuse in the stabilized landfills are proposed.

Performance Appraisal of Controlled Low-strength Material Using Sewage Sludge and Refuse Incineration Bottom Ash

This research evaluated the use of sewage sludge and refuse incineration bottom ash to replace calcium sulfoaluminate cement （CSA） in making controlled low-strength material （CLSM）. Various properties of CLSM mixtures were characterized in terms of unconfined compressive strength, microstructure and leachability. It was found that the strength of tested CLSM mixtures ranged from 3.6 to 9.0 MPa, over the upper excavatable limit of 2.1 MPa. The micro-structural analysis revealed that sewage sludge and bottom ash were crystallochemically in- corporated within CLSM system_s by forming the needle-like ettringite （C3A＇3CS＇_H32） with exiguous tu.bers via the typical Pozzolanic Reaction, leading to a dense and low-porosity microst;＇ucture. Furthermore,-the toxicity characteristic leaching procedure evidenced that the cumulative leachable metals in the leachate were much below the regulatory thresholds. The potential for us!ng sewage sludge and bottom ash!n CLSM makin.g was thus confirmed.

Effect of bio-column composed of aged refuse on methane abatement-A novel configuration of biological oxidation in refuse landfill

An experimental bio-column composed of aged refuse was installed around the exhaust pipe as a new way to mitigate methane in refuse landfill.One of the objectives of this work was to assess the effect of aged refuse thickness in bio-column on reducing CH 4 emissions.Over the study period,methane oxidation was observed at various thicknesses,5 cm （small size）,10 cm （middle size） and 15 cm （large size）,representing one to three times of pipeline diameters.The middle and large size both showed over 90% methane conversion,and the highest methane conversion rate of above 95% occurred in the middle-size column cell.Michaelis-Menten equation addressed the methanotrophs diffusion in different layers of the bio-columns.Maximum methanotrophic activity （V max） measured at the three thicknesses ranged from 6.4 × 10 3 to 15.6 × 10 3 units,and the half-saturation value （K M） ranged from 0.85% to 1.67%.Both the highest V max and K M were observed at the middle-size of the bio-column,as well as the largest methanotrophs population,suggesting a significant efficiency of methane mitigation happened in the optimum zone with greatest affinity and methanotrophic bacteria activities.Therefore,bio-column is a potential style for methane abatement in landfill,and the aged refuse both naturally formed and artificially placed in the column plays a critical role in CH 4 emission.

Effect of leachate recycling and inoculation on the biochemical characteristics of municipal refuse in landfill bioreactors

Activity development of key groups of enzymes involved in municipal refuse decomposition was measured in laboratory landfill bioreactors with and without leachate recycling and inoculation for about 210 days. The results showed that the enzymes (amylase, protease, cellulase, lipase and pectinase) were present in fresh refuse but at low values and positively affected by leachate recycling and refuse inoculation. The total average of cellulase activity in digesters D3 operated with leachate recycling but no inoculation, D4 and D5 operated with leachate recycling and inoculation was much higher than that in digesters D1 and D2 without leachate recycling and inoculation by 88%—127%, 117%—162% and 64%—98%. The total average of protease activity was higher in digester D4 than that in digesters D1, D2, D3 and D5 by 63%, 39%, 24% and 24%, respectively, and the positive effect of leachate recycling and inoculation on protease activity of landfilled refuse mainly was at the first two months. The total average of amylase activity was higher in digesters D3, D4 and D5 than that in digesters D1 and D2 by 83%—132%, 96%—148% and 81%—129%. During the early phase of incubation, the stimulatory effect of inoculation on lipase activity was measured, but refuse moisture was the main factor affecting lipase activity of landfilled refuse. The inoculation, initial and continuous inoculation of microorganisms existing in leachate, was the mainly stimulatory factor affecting pectinase activity of landfilled refuse.

Soil water deficit and vegetation restoration in the refuse dumps of the Heidaigou open-pit coal mine,Inner Mongolia,China

The sustainability of ecosystem restoration of refuse dumps in open-pit coal mines depends on plant species selection, their configuration, and the optimal usage of water resources. This study is based on field experiments in the northern refuse dump of the Heidaigou open-pit coal mine in Inner Mongolia of China established in 1995. Eight plant configurations, including trees, shrubs, grasses, and their combinations, as well as the adjacent community of natural vegetation, were selected. The succession of the revegetated plants, soil water storage, the spatiotemporal distribution of plant water deficits degree and its compensation degree were also studied. Results indicated that the vegetation cover （shrubs and herbaceous cover）, richness, abundance, soil nutrients （soil organic matter, N and P）, and biological soil crust coverage on the soil surface are significantly influenced by the vegetation configurations. The average soil water storage values in the shrub ＋ grass and grass communities throughout the growing season are 208.69 mm and 206.55 mm, which are the closest to that of in the natural vegetation community （215.87 mm）. Plant water deficits degree in the grass and shrub ＋ grass communities were the lowest, but the degrees of water deficit compensation in these configuration were larger than those of the other vegetation configurations. Differences in plant water deficit degree and water compensation among the different config- urations were significant （P 〈0.05）. Plant water deficit degrees were predominantly minimal on the surface, increased with increasing soil depth, and remained stable at 80 cm soil depth. The soil moisture compensation in the natural vegetation, shrub ＋ grass, and grass communities changed at 10%, while that in other vegetation communities changed between 20% and 40%. Overall, we conclude that the shrub ＋ grass and grass configuration modes are the optimal vegetation restoration models in terms of ecohydrology for future ecological engineering projects.

Froth flotation of refuse coal fines and process optimization using 2D surface plots

Refuse coal fines of size <500 μm was collected from a metallurgical coal preparation plant located in the eastern coalfield region of India. The coal was beneficiated using froth flotation technique to recover clean coal with ash content of about 20% with the highest possible yield. Diesel oil as collector and pine oil as frother were used. Box-Behnken statistical design was followed for analyzing the performance at varying pulp density, collector and frother dosage. Results were discussed using 2D surface plots. Response function predictions determined by the regression analysis show coefficient of correlation(R^2) for yield and the ash content as 0.72 and 0.86, respectively. The highest yield of 45.79% is obtained at pulp density 10%, collector dose 2 kg/t and frother dose 1.5 kg/t. The lowest ash content of 18.9% is obtained at pulp density 10%, collector dose 1 kg/t and frother dose 1 kg/t.

Effect of Inoculation with Effective Microorganisms and Leachate Recycle on Degradation of Municipal Refuse

Biodegradation of waste in landfill is a slow process requiring decades for completion. Accelerated degradation of municipal refuse in modulated landfill environments may alleviate or eliminate pollution to the land, water and air. In this work, nineteen effective microorganisms (EMs) were isolated from old landfill refuse by enrichment culturing techniques and used for the inoculum of municipal refuse. The preliminary experiments demonstrate that a combination of EMs inoculation in landfill with leachate recycle resulted in increased rates of decomposition and faster process stability. The concentrations of COD, VFA and SO4^2- in digester with EMs inoculation and leachate recycle decreased more rapidly than others. Gas production from digester with EMs inoculation and leachate recycle commenced around 32 days, which is a week shorter than with leachate recycle only. And peak cumulative gas production was obtained much earlier in digester with EMs inoculation and leachate recycle (150 days) compared to 180 days with leachate recycle only. Moreover, in the first two months, the rate of settlement in digester with EMs inoculation and leachate recycle was more rapid than others.

Combustion Characteristics of Solid Refuse Fuels from Different Waste Sources

In the production(as co-fuel or alone)of solid refuse fuel(SRF),knowledge about the characteristics of the raw materials is required for an ecofriendly and effective combustion process.SRFs are commonly produced by drying combustible waste and removing incombustible matter,resulting in a higher combustibility as compared to the original waste.However,the characteristics of SRFs may highly vary depending on where and from which materials they were produced.Thus,we investigated the characteristics of various SRFs using thermogravimetric analysis(TGA).As a TGA sample is commonly small,on the scale of milligrams,and,unlike homogeneous fuels,SRFs are heterogeneous,individual SRF samples analysed with this method may not represent the bulk material,and sample properties may vary significantly between batches.Therefore,we further performed combustion experiments using a small-scale combustor and sample sizes from 1 to 10 g.To optimise SRF combustor design and determine the SRF characteristics,proximate,elemental,heating value,TG,and differential thermogravimetric analyses were conducted,and weight losses and gas concentrations at different temperatures were measured upon combustion.The lower heating values of the three analysed SRFs were 20,976,16,873,and 19,762 kJ/kg,and their Cl contents were 0.89,0.95,and 1.27 wt.%(legal criterion[Cl]<2.0 wt.%).TGA and small combustor experiments showed that complete weight loss was achieved below 500°C.However,CO was detected until 620°C.

Degradation of Refuse in Hybrid Bioreactor Landfill

Objective To explore the process of refuse decomposition in hybrid bioreactor landfill. Methods The bioreactor landfill was operated in sequencing of facultative-anaerobic and aerobic conditions with leachate recirculation, pH, COD, and ammonia in the leachate and pH, biodegradable organic matter （BDM）, and cation exchange capacity （CEC） in refuse were detected. Results CEC increased gradually with the degradation of refuse, which was negatively correlated with BDM. COD and ammonia in the leachate was declined to 399.2 mg L^-1 and 20.6 mg N L^-1, respectively, during the 357-day operation. The respective concentrations of ammonia and COD were below the second and the third levels of current discharge standards in China. Conclusion The refuse is relatively stable at the end of hybrid bioreactor landfill operation. Most of the readily biodegradable organic matter is mineralized in the initial phase of refuse degradation, whereas the hard-biodegradable organic matter is mainly humidified in the maturity phase of refuse degradation.

Classification of Domestic Refuse in Medical Institutions Based on Transfer Learning and Convolutional Neural Network

The problem of domestic refuse is becoming more and more serious with the use of all kinds of equipment in medical institutions.This matter arouses people’s attention.Traditional artificial waste classification is subjective and cannot be put accurately;moreover,the working environment of sorting is poor and the efficiency is low.Therefore,automated and effective sorting is needed.In view of the current development of deep learning,it can provide a good auxiliary role for classification and realize automatic classification.In this paper,the ResNet-50 convolutional neural network based on the transfer learning method is applied to design the image classifier to obtain the domestic refuse classification with high accuracy.By comparing the method designed in this paper with back propagation neural network and convolutional neural network,it is concluded that the CNN based on transfer learning method applied in this paper with higher accuracy rate and lower false detection rate.Further,under the shortage situation of data samples,the method with transfer learning and ResNet-50 training model is effective to improve the accuracy of image classification.

Ecological Restoration Design of Refuse Landfill——A Case Study of Landscape Planning of Beichen Shuangkou Refuse Landfill in Tianjin City

Refuse landfill plays an important role in daily life,but also brings serious pollution.By investigating environment pollution of Beichen Shuangkou Refuse Landfill in Tianjin City,this paper put forward major problems of this refuse landfill,and suggestions for turning it into a landscape system with regeneration and renewing capacity,so as to provide references for ecological restoration and landscaping of similar damaged land resources.

Study of Engineering Characteristics of Coal Refuse Foundation

Coal refuse in a natural state is a kind of loose medium with inherent physical and chemical properties. It can be used after compaction as materials for foundation of buildings. Based on the results of numerical analysis and experiments, a study is successfully made in this paper to reveal the compression, load-bearing and anti-mining de formation characteristics. The obtained results are of great significance in guiding the miniug operations under surface buildings erected on pre-paved refuse foundations.

Absorption of phosphorus from wastewater by aged refuse excavated from municipal solid waste landfill

Municipal solid waste(refuse) landfill stabilizes as the refuse degrades. After years of biodegradation, the refuse in the landfill becomes stabilized and aged, which may vary with the local climate, humidity, and composition of refuse placed. In this work, it is found that the refuse with an age of over 8 years at Shanghai Refuse Landfill has been significantly stabilized and sufficiently aged and is thus suitable for excavation. The 8 year old aged refuse is mechanically screened, and the fine fractions of refuse(aged refuse) with a diameter less than 2 cm are then used as a biological absorbent for removal of both inorganic and organic phosphorus in livestock wastewater and prepared aqueous solution. It is proved that the aged refuse is very effective for the quantitative removal of both types of phosphorus. The absorption mechanism is proposed. It is considered that phosphorus is firstly absorbed onto the surface of the aged refuse and then used as a substrate for the growth of microorganisms which ultimately leave the aged refuse as sludge.

Low Temperature Dechlorination of Densified Refuse Derived Fuel in Pyrolysis

Study on behavior of chlorine contained in oval-shaped densified refuse derived fuel (d-RDF) prepared from municipal solid waste in pyrolysis was carried out by means of temperature-programmed electrical furnace, and the gas evolving from pyrolysis was investigated by FTIR. De-HCl rate was calculated by determining the emission fraction of HCl in the flue gas and the fraction of Cl left in the pyrolysis residue. The results show that Cl in the d-RDF releases primarily in the form of HCl during the pyrolysis, and the initial releasing temperature of HCl enhances with the increase of heating rate. Meanwhile, the higher the end temperature of pyrolysis, the more the Cl released. De-HCl rate is about 70% when the end temperature of pyrolysis is around 600℃. Besides, mechanism of Cl release is dis-cussed.

Preparation and Characterization of Refuse Derived Fuel for Pyrolysis and Gasification by Bindless High Pressure Briquetting Technology

A new type of refuse derived fuel (RDF) for pyrolysis and gasification was prepared from municipal solid waste (MSW) in the presence of a small quantity of coal by bindless high pressure technology at room temperature. The physicochemical property of RDF was tested. Orthogonal experiment method was used to optimize the process parameters using dropping strength (mechanical strength) and thermal stability of the RDF as indices for quality of RDF. The result shows that the mixture of MSW and coal with a total moisture ranging from 5% to 17% can be easily compressed into RDF briquettes at a pressure above 70 MPa. When the briquetting pressure is higher than 100 kN and moisture content is about 10%, the qualified RDF can be obtained. The orthogonal experiment shows that the moisture can greatly affect the mechanical strength of RDF, while all the technique parameters have no obvious influence on thermal stability of RDF. The optimal parameters are a shaping pressure of 106 MPa, a moisture content of 10%, and a coal content of 20%.

Studies on Human Intestinal Parasites in Refuse Dumps

This study investagated the data of the prevalence of intestinal parasites of human from September 2007 to July 2008 using faecal samples which were picked from refuse dump sites. A total of 2,050 stool samples picked and examined from five selected popular refuse dump sites in Ado-Ekiti. And Entamoeba histolytica, Giardia lamblia and Balantidium coli were mostly identified. The analysis of the infection shows that E. histolytica has a percentage prevalence of 65.5%, followed by G. lamblia with 42.5% and B. coli having 1.9%. Multiple infections of these parasites were also prevalent. There was a positive correlation （r=0.995, P〈0.05） between percentage prevalence of infection and home surroundings, waste, sewage disposal facilities and habits. Also, there was a significant difference （t=1 1.06, P〈0.05） in the prevalence of infections between location A and B. Probable ways of eliminating/controlling the disease are also highlighted.