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.

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%.

Study on the interaction between inherent minerals of coal with refuse derived fuel(RDF)during co-firing

In this paper,refuse derived fuel(RDF)and bituminous coal were co-fired to investigate the particulate matter(PM)yields and the interaction between the inherit minerals in a lab-scale drop tube furnace(DTF).The PM1-10 yields during the co-firing of coal and RDF dramatically decreased by 16.29%~28.5%of the combustion of coal alone.In addition,methane auxiliary combustion inhibited the PM_(1) yields by 7.95%at air atmosphere.The Si-rich minerals in coal interreacted with the organic alkali(earth)metals in RDF,massively generating sticky particles with high liquid amount of K-Al-Si and Ca-Al-Si,promoting the transformation of fine grains into coarser mode.Moreover,it was proved that both methane auxiliary combustion and co-firing can reduce the emission of fine particles.The additional heat accelerated the burn of the char at the early stage of combustion,providing adequate time for the interaction between the inorganic species.Through thermodynamic equilibrium calculations of 1500~3000 fly ash grains,it was found that co-firing increased the formation of sticky particles by 64.8%~70.3%,resulting in a significant enhancement in capturing fine particles and Na,K vapor.Therefore,the co-firing of coal with RDF offers a promising approach to realize the harmless and resourceful treatment of municipal solid waste(MSW),and inhibit land resource losses caused by landfill.

Use of coals and wastes in a co-gasification process aimed at producing hydrogen rich gas

The use of low-quality coals and flotoconcentrates is currently severely limited,and the problem of managing municipal waste from anthropogenic activities is currently a challenge.The problems of reducing carbon dioxide emissions,utilizing the energy potential of waste and increasing its recycling have an impact on the costs of electricity production.Considering the abundant streams of unused fuels,they can be considered as attractive energy materials,so environmentally-friendly and cost-effective options for their utilization should be developed.A study was conducted using steam co-gasification technology on selected coals,flotation concentrates and Refuse Derived Fuel(RDF)alternative fuel.Selected low-quality coals were combined with RDF alternative fuel in a process aimed at hydrogen production.The experiments produced gas with hydrogen concentrations ranging from 67%(vol.)to 68%(vol.)with low methane concentrations.It was observed that the addition of alternative fuels helped to increase the hydrogen concentration in syngas.Attention was paid to the catalytic ability of the metal oxides contained in the fuel blend,with particular reference to K_(2)O and Al_(2)O_(3)and TiO_(2).

Recycling combustibles from aged municipal solid wastes(MSW)to improve fresh MSW incineration in Shanghai:Investigation of necessity and feasibility

Aged municipal solid wastes(MSW)excavated from landfills and dumpsites were characterized to analyze their fraction composition,moisture content,and lower heat value(LHV).The necessity and feasibility of recycling combustibles from aged MSW to improve the incineration of fresh MSW were investigated.The results showed that combustibles in aged MSW were easily separated from other components and than LHV of the separated combustibles are higher than 11000 kJ/kg.The fresh MSW are of high moisture contents with average LHV below 6500 kJ/kg,making their stable combustion difficult to maintain in MSW incinerators.For both fresh MSW and aged MSW,plastics are the main contributor to their LHV.To improve incineration of fresh MSW that are characterized with low LHV,combustibles separated from aged MSW were made into refuse derived fuel(RDF)pellets and were then added to fresh MSW by 2%wt.–5%wt.LHV variation and air supply resistance change of the MSW layer on the incinerator grate caused by the addition of RDF was checked,and no significant changes were found.No obvious difference was observed for the‘burn-out time’between RDF pellets and fresh MSW either.RDF made from aged MSW combustibles is found to be a promising auxiliary fuel to improve the incineration of fresh MSW,and aged MSW from old landfill cells and dumpsites can be finally disposed of jointly with fresh MSW by recycling combustible from the former to be coincinerated with the latter in the incineration plants.

Effects of introducing energy recovery processes to the municipal solid waste management system in Ulaanbaatar, Mongolia

Currently, most developing countries have not set up municipal solid waste management systems with a view of recovering energy from waste or reducing greenhouse gas emissions. In this article, we have studied the possible effects of introducing three energy recovery processes either as a single or combination approach, refuse derived fuel production,incineration and waste power generation, and methane gas recovery from landfill and power generation in Ulaanbaatar, Mongolia, as a case study. We concluded that incineration process is the most suitable as first introduction of energy recovery. To operate it efficiently,3Rs strategies need to be promoted. And then, RDF production which is made of waste papers and plastics in high level of sorting may be considered as the second step of energy recovery.However, safety control and marketability of RDF will be required at that moment.

Co-combustion of RDF and biomass mixture with bituminous coal:a case study of clinker production plant in Egypt

Cement clinker production in Egypt till 2013 relied mainly on fossil fuel as a primary energy source.However,with multiple fossil fuel shortages,the utilization of biomass wastes was initiated by multiple cement producers.In the current work,and to present an industrial-scale biomass and coal co-combustion study,the utilization of multiple biomass fuels to substitute a portion of bituminous coal was studied in an Egyptian clinker production plant.Mixtures of biomass fuels were used to reduce the consumption of bituminous coal and to investigate the diminishing of the environmental impact of the clinker production process.The current study was conducted during 8 days of the stable clinker production process by replacing 14%of bituminous coal with biomass mixtures while monitoring the major process control parameters and resulting emissions.Emission results were compared to the nation’s regulations.A conclusion can be made that using biomass mixtures as alternative fuels minimized the dependency on coal as the main fuel and reduced the CO_(2)burden of the cement produc-tion process.In addition,NO_(x)and SO_(2)emissions were declined while CO emissions were increased by utilizing biomass mixtures as alternative fuels;all emissions,however,were below the allowable limits stated by the Egyptian environmental authority.Noticeably,the heavy elements,dioxins,and furans were not changed significantly compared to those produced using coal only.