Advanced Materials Research Vols. 347-353

Abstract: With the development of information and computer technology, it is possible to monitor and analyze on-line features of large steam turbine-generator units. The energy consumption rate and the exhaust steam dryness are two important indices. Base on the analyses of those existed calculation methods for turbine varying condition, we give a sequential varying condition calculation that starts with steam extraction of the final stage or the second final stage (superheated steam condition). According to the initially assumed final stage flow, and the thermodynamic parameters before the final stage, also the backpressure, we can distinguish the flow patterns of the stage by a discriminant criteria. Then we can conduct a stage varying condition calculation of primary stage in sequence from the front final stage parameter, so the new exhaust steam enthalpy and the exhaust steam dryness can be got. So the precise energy consumption rate and the exhaust enthalpy (or the dryness) can be got easily. Obviously, without measuring the flow or the dryness, we can accurately monitor the on-line energy consumption rate and the dryness of the units.

Abstract: The catalytic effect of HZSM-5 on fast pyrolysis of lignin was investigated by using an analytical pyrolyzer coupled with Gas Chromatography and Mass Spectrometry (Py-GC/MS). The distribution of products was studied primarily obtained at different reaction conditions of temperature and addition ratio of HZSM-5. The main products were phenols and aromatic hydrocarbons. With the addition of HZSM-5, the content of phenols was decreased from 67.66% (for pure lignin) to 26.07%, and the content of aromatic hydrocarbons was increased from 10.77% to 57.38% when the mass ratio of HZSM-5: lignin was 1:1. However, the effect of temperature on the reaction activity of HZSM-5 in the range of 400-600°C was not significant. It was concluded that the addition of HZSM-5 enhanced the conversion of phenols to aromatic hydrocarbons by deoxygenation, and this effect was improved with the addition ratio of HZSM-5 increasing.

Abstract: An analytical pyrolyzer coupled with Gas Chromatography and Mass Spectrometry (Py-GC/MS) was employed to study the influence of HZSM-5 on the pyrolysis products of cellulose. The results revealed that pyrolysis products of cellulose consisted of light molecular weight products with linear chain, anhydrosugars and furan compounds. Light molecular products were mainly acetaldehyde and 2-propanone, 1-hydroxy; anhydrosugars were mainly levoglucosan (LG), levoglucosenone (LGO) and 1,4:3,6-Dianhydro-α-d-glucopyranose (DGP); Furans were mainly furfural (FF) and 5-(hydroxymethyl) furfural (HMF). The addition of HZSM-5 changed the contents of main products from fast pyrolysis of cellulose, especially for aromatic hydrocarbons, which belonged to light molecular products and increased rapidly. In addition, plenty of carbon dioxide appeared. With the addition of HZSM-5, the dehydration of LG was enhanced to produce LGO and then LGO was further decomposed into small molecular products with HZSM-5: cellulose ratio increasing. And the formation of FF and HMF were both inhibited with the addition of HZSM-5, but the formation of furan was improved. It was inferred that the addition of HZSM-5 could effectively promote the further dehydration of initial products from cellulose fast pyrolysis by the breakage of side chain.

Abstract: In many of the current biomass-fired power plants, the fly ash usually contains abundant combustible char, due to the in-sufficient burning. In this study, a new idea was proposed to prepare briquette fuel using the fly ash. Experiments were conducted to produce six briquette fuels from the fly ash added with the composite binder and using a lab-scale briquetting machine. The mechanical strength of the six briquette fuels and their burning-out residues was measured, to reveal the effects of the composite binder on preparation and characteristics of the briquette fuel.

Abstract: A new type of cavity configuration — butterfly-type cavity applied in the scramjet is proposed in this paper. The supersonic combustion chamber with Butterfly-type cavity was investigated numerically and experimentally. Results show that the horizontal vortex moving along the Y direction is helpful in gathering hydrogen gas, but the vertical vortex moving along the Z direction is not. Both turbulent kinetic energy and turbulent kinetic energy dissipation rate are very high at the junction between the cavity and the main combustion chamber. And the production of turbulent kinetic energy is agreeable with that of turbulent kinetic energy dissipation.

Abstract: Aiming at the coke oven temperature characteristics of great inertia pure time-delay, non-linear and time changeable, a new method that genetic algorithm is introduced to optimize PID parameters is proposed .In calculation of iteration, the optimal solutions are always reserved to guarantee all individuals to converge to the global optimization. For obtaining perfect control effect, the square of control quantity and overshoot-punishment item are set to an objective function with a time-integral to the absolute value of error. The genetic PID algorithm is adopted to control the output temperature. The simulation results of the proposed algorithm applied to a simplified oven model show the feasibility of the method

Abstract: A mathematical model is developed for the gas flow in a biomass-fired grate boiler with inner dust removal device, with the purpose to optimize the combustion condition. The distribution of gas flow is determined by the air flow ratio and the optimization is realized by the particular simulation. The optimal air flow is obtained by the analysis of various air flow ratios, via the comparison of flow characteristics and turbulence kinetic energy. The results of the numerical simulation show that the optimum air flow can help the sufficient the mixing and burnout of combustible in the furnace. It clearly indicates that the numerical simulation can be an effective tool for the practical guidance.

Abstract: Anaerobic co-digestion of dairy manure, chicken manure with corn stalks were investigated at 15, 35 and 55 °C. Two trials were carried out, one based on co-digestion of dairy or chicken manure alone with corn stalks at ratios of 1:1, 2:1 and 3:1, the other based on co-digestion of dairy and chicken manure together with corn stalks on the premise of the optimal ratio between manure and stalks. In the first trial, the analysis based on the biogas and methane yields showed that co-digestion of dairy or chicken manure with corn stalks at 2:1 both had higher fermentabilities than other ratios. In the second trial, at 15 °C and 35 °C, various ratios of co-digestion of dairy and chicken manure together with corn stalks were all higher than co-digestion of two kinds of manure alone with corn stalks and maximum biogas and methane yields were obtained at the C/N ratios from 25 to 28. At 55 °C, only at the mixture ratios of 1.6:0.4:1, co-digestion of dairy and chicken manure together with corn stalks were higher than co-digestion of dairy manure with corn stalks, indicating the optimal C/N ratios from 28 to 30 in biogas and methane production. Based on regression analysis, maximum biogas and methane yields were found at 49.9 °C and 46.9 °C with the ratios of dairy, chicken manure and corn stalks at 1.14:0.86:1 and 0.74:1.26:1, respectively.

Abstract: Because of quite a certain content of alkali metal in biomass, bed material agglomeration appears in the process of thermal reaction in fluidized bed, which can destroy fluidization. In the paper, fluidized bed gasification experiments on alkali metal enrichment were made, of which cotton straw pellets were used as fuel. The results are shown that experiments could keep running by bed material replaced at regular time without slag and the component of the bed material maintained stability. The replaced bed material could be used again after being washed. Through the XRF analysis, it could be found that the potassium compound with high dissolubility could be removed by washing.

Abstract: The inhibition of ammonia nitrogen and volatile acid on anaerobic methanogenesis during the anaerobic digestion of kitchen wastes by way of digest fluid backflow was studied. The experiment was conducted at 35°C, and used kitchen wastes as organic carbon source .The results shows that the ammonia nitrogen inhibition concentration is 1400-1700 mg/L. When the ammonia nitrogen concentration rises to 2000 mg/L, the anaerobic methanogenesis efficiency decreased obviously, along with the accumulation of volatile acid. At the feeding organic load of 3.5-4.0kgVS/(m³.d), the anaerobic methanogenesis system was stable operation, the higher VS reduction (72.17%) and the higher methane production rate were obtained..