Effect of a moving flame on the temperature of polymer coatings and substrates

A computational model is developed to predict the temperature profile over an organic coating on a metal surface as a result of the action of a moving flame. The deflection of the flame as it impinges on the surface is simulated and its consequent heat transfer to the polymer is determined. The scanning action of the flame across the substrate is quantified and the temperature profiles within the polymer are calculated. The results show a substantial build up of temperature at the surface and large temperature gradients throughout the thickness, which are due to the low thermal conductivity of polymers. This can be particularly detrimental for polymers owing to their low softening and decomposition temperatures. The model can be applied to flame impingement on a bulk polymer or on an organic coating on a metal substrate. The research shows the risks of a moving flame overheating a polymer surface and indicates remedial measures.     

从燃烧温度分析套筒窑燃烧高炉煤气的可行性

计算了传统工艺下套筒窑燃烧高炉煤气时下燃烧室的燃烧温度并分析了其不可行性,并就采用燃气预热技术、高效喷射技术及无焰燃烧技术对下燃烧室燃烧温度的影响进行计算分析,从而得出套筒窑燃烧高炉煤气的可行性,并给出若干措施及建议。     

Adiabatic flame temperature from biofuels and fossil fuels and derived effect on NOx emissions

There is currently a sustained interest in biofuels as they represent a potential alternative to petroleum derived fuels. Biofuels are likely to help decrease greenhouse gas emissions and the dependence on oil resources. Biodiesels are Fatty Acid Methyl Esters (FAMEs) that are mainly derived from vegetable oils; their compositions depend on the parent vegetables: rapeseed (“RME”), soybean (“SME”), sunflower, palm etc. A fraction of biodiesel has also an animal origin (“tallow”). A key factor for the use of biofuels in gas turbines is their emission indices (NOx, CO, VOC, and PM) in comparison with those of conventional “petroleum gasoils”. While biodiesels reduce carbon-containing pollutants, experimental data from diesel engines show a slight increase in NOx. The literature relating to gas turbines is very scarce. Two recent, independent field tests carried out in Europe (RME) and in the USA (SME) showed slightly lower NOx while a lab test on a microturbine showed the opposite effect. To clarify the NOx index of biodiesels in gas turbines, a study has been undertaken, taking gasoil and natural gas (NG) as reference fuels. In this study, a calculation of the flame temperature developed by the 3 classes of fuels has been performed and the effect of their respective compositions has been investigated. The five FAMEs studied were RME, SME and methyl esters of sunflower, palm and tallow; these are representative of most widespread vegetable and animal oil bases worldwide. The software THERGAS has been used to calculate the enthalpy and free energy properties of the fuels and GASEQ for the flame temperature (T_f), acknowledging the fact that “thermal NOx” represents the predominant form of NOx in gas turbines. To complete the approach to structural effects, we have modeled two NG compositions (rich and weak gases) and three types of gasoil using variable blends of eleven linear/branched/cyclic molecules. The results are consistent with the two recent field tests and show that the FAMEs lie close to petroleum gasoils and higher than NG in terms of NOx emission. The composition of the biodiesel and regular diesel fuel influences their combustion heat: methyl esters with double bonds see a slight increase of their T_f and their NOx index while that of gasoil is sensitive to the aromatic content.     

Ti2CTx MXene: A novel p-type sensing material for visible light-enhanced room temperature methane detection

The development of semiconductor-based room-temperature methane (CH₄) gas sensors is appealing but challenging. Herein, we report a CH₄ gas sensor operating at room temperature based on Ti₂CT_x MXene, a novel p-type sensing material, achieving high-performance CH₄ detection with visible light assistance. The Ti₂CT_x MXene based device showed more than seven-fold improvement for CH₄ detection under visible-light irradiation, and the response/recovery times were also sharply decreased. The excellent CH₄ sensing performance at room temperature could be attributed to the visible-light photocatalytic CH₄ oxidation activity of the Ti₂CT_x sensing material. CH₄ oxidation was revealed by photocatalytic measurement, O₂-TPD and in-situ IR spectroscopies. The present work demonstrates the novel application of Ti₂CT_x MXene as a promising p-type sensing material for methane detection at room temperature. Moreover, the concept of “photocatalysis-enhanced gas sensing” can be employed in room-temperature gas sensors based on other novel semiconductors.     

Hydrothermal flame impingement experiments. Combustion chamber design and impingement temperature profiles

The current work presents the hydrothermal flame impingement experiments conducted for the design of a hydrothermal spallation drilling nozzle. The products of hydrothermal flames of mixtures of ethanol, water and oxygen were injected as free jets in a high pressure water bath. The nozzle design was based on ideas stemming from underwater welding and cutting of metal sheets. Water entrainment in the flame-jets and the heat transfer capabilities of flames injected from various nozzles have been analyzed by measuring their impingement temperature profiles on a flat stainless steel plate. It was found that the thermal-to-kinetic energy ratio of the jet has a direct influence on the entrainment of water in it. Furthermore, the cooling water of the combustion chamber was injected in various angles to the axis of the jet resulting to different entrainment rates. It was found that higher water injection angles reduced the rate of entrainment. Finally, it was indicated that at certain operational points of the jet, its trans-critical properties had an important influence on the impingement temperatures.     

Effect of the radiation surface on temperature and NOx emission in a gas fired furnace

A significant increase in the efficiency of furnaces burning natural gas is achieved by increasing the radiation heat transfer from the flame. In this study, the effect of cylindrically shaped additional radiation surface called, filling material (FM), on emissions and temperature distribution in the combustion chamber (CC) was investigated experimentally. Experiments were carried out on a fire tube water heater described in the standard EN 676 for the firing rates of 58, 87 and 116 kW. Two diameters of the filling materials, 25 and 30 cm, and two lengths of 20 and 40 cm were considered. The flame temperature and nitrogen oxide (NO) emission were measured for different positions and geometries of the filling material in the combustion chamber. The flame temperature and the temperature drop of the flame in the back flow increased with the increasing diameter and length of the filling materials compared to the case without filling material. It was observed that the filling material with the larger diameter increased the heat transfer rate in the back flow compared to the case without filling material. The in-furnace measured NO concentration was in good agreement with NO concentration in the well-mixed flue gas. The 20 cm long filling materials decreased the NO emission. Increased length of the filling material resulted in increased the NO emission.     

Thermoneutral tri-reforming of flue gases from coal- and gas-fired power stations

The treatment of flue gases from fossil fuel fired power stations by tri-reforming with natural gas or by coal gasification could become an attractive approach for converting the CO₂, H₂O, O₂, and N₂ contained in these flue gases via syngas processing into useful products, such as methanol, hydrogen, ammonia, or urea. The present study determines the constraints for achieving such thermochemical reactions under conditions of thermoneutrality, by reacting the flue gases with water, air, and natural gas or coal at 1000–1200 K. The implications of such reactions are examined in terms of CO₂ emission avoidance, fuel saving, economic viability, and exergy efficiency.     

Natural gas density under extremely high pressure and high temperature: Comparison of molecular dynamics simulation with corresponding state model

This work applied molecular dynamics(MD) simulation to calculate densities of natural gas mixtures at extremely high pressure( 138 MPa) and high temperature( 200 °C) conditions(x HPHT) to bridge the knowledge and technical gaps between experiments and classical theories. The experimental data are scarce at these conditions which are also out of assumptions for classical predictive correlations, such as the Dranchuk Abou-Kassem(DAK) equation of state(EOS). Force fields of natural gas components were carefully chosen from literatures and the simulation results are validated with experimental data.The largest relative error is 2.67% for pure hydrocarbons, 2.99% for C1/C3 mixture, 7.85% for C1/C4 mixture, and 8.47% for pure H_2S. These satisfactory predictions demonstrate that the MD simulation approach is reliable to predict natural-and acid-gases thermodynamic properties. The validated model is further used to generate data for the study of the EOS with pressure up to 276 MPa and temperature up to 573 K. Our results also reveal that the Dranchuk Abou-Kassem(DAK) EOS is capable of predicting natural gas compressibility to a satisfactory accuracy at x HPHT conditions, which extends the confidence range of the DAK EOS.     

Development of a least squares support vector machine model for prediction of natural gas hydrate formation temperature

Hydrates always are considered as a threat to petroleum industry due to the operational problems it can cause.These problems could result in reducing production performance or even production stoppage for a long time.In this paper,we were intended to develop a LSSVM algorithm for prognosticating hydrate formation temperature (HFT) in a wide range of natural gas mixtures.A total number of 279 experimental data points were extracted from open literature to develop the LSSVM.The input parameters were chosen based on the hydrate structure that each gas species form.The modeling resulted in a robust algorithm with the squared correlation coefficients (R2) of 0.9918.Aside from the excellent statistical parameters of the model,comparing proposed LSSVM with some of conventional correlations showed its supremacy,particularly in the case of sour gases with high H2S concentrations,where the model surpasses all correlations and existing thermodynamic models.For detection of the probable doubtful experimental data,and applicability of the model,the Leverage statistical approach was performed on the data sets.This algorithm showed that the proposed LSSVM model is statistically valid for HFT prediction and almost all the data points are in the applicability domain of the model.     

A new process for synthesis gas by co-gasifying coal and natural gas

Production of synthesis gas with coal and natural gas co-gasification is a new process based on coupling of methane steam-reforming and coal gasification. The process concept is discussed in this paper. Experiments are carried out in a laboratory fixed-bed gasifying reactor to investigate the effect of feedstock on composition, ratio of hydrogen to carbon monoxide, concentrations of hydrogen and carbon monoxide in the produced raw synthesis gas. Preliminary experimental results indicate that the effect of steam flow rate on component, ratio of hydrogen to carbon monoxide and concentrations of hydrogen and carbon monoxide of the raw synthesis gas is slight, while the effect of oxygen flow rate is pronounced. When the ratio of oxygen to methane in feedstock is below 1, the ratio of hydrogen to carbon monoxide is greater than 1 and the total concentration of hydrogen and carbon monoxide is above 90%. Comparison of experimental results with calculated results shows that the composition of raw synthesis gas is near equilibrium.     

环氧化天然橡胶玻璃化转变温度与环氧化程度的关系

根据Ｖａｎ Ｋｒｅｖｅｌｅｎ 等提出的一些高聚物物理参数加合性原则,推导了环氧化天然橡胶（ＥＮＲ） 的玻璃化转变温度（Ｔｇ） 与环氧化程度（Ｂ） 的关系,并根据经验公式计算了不同环氧化程度ＥＮＲ 的Ｔｇ 。     

Adiabatic premixed combustion in a gaseous fuel porous inert media under high pressure and temperature: Novel flame stabilization technique

This work presents an experimental investigation to study the characteristics of combustion using a premixed methane-air mixture within a non-homogeneous porous inert medium (PIM) under high pressure and temperature. In order to obtain a stable flame under these operating conditions within PIM, a novel flame stabilization technique in porous inert media (PIM) combustion under high pressure and temperature has been developed and evaluated. The proposed technique avoids the draw backs of the hitherto developed techniques by properly matching the flow and flame speeds and, consequently, ensuring a stable combustion, for a wide range of operating pressure and temperature. The success of this technique permits the extension of PIM combustion to new applications such as gas turbines. The validity of this new technique has been assessed experimentally in detail by analyzing combustion inside a prototype burner. The effects of various operating conditions, such as initial preheating temperature and elevated pressure, have been examined for an output power range between 5 and 40 kW. The experiments covered a broad spectrum of operating conditions ranging from a mixture inlet temperature of 20 °C and pressure ratio of 1 up to a temperature of 400 °C and a pressure ratio of 9. Evaluation of the results revealed excellent flame stability with respect to both flashback and blow-out limits throughout all the operating conditions studied, including relative air ratios far beyond the normal lean limit. While the blow-out stability showed no significant dependence on pressure, it was strongly determined by the preheating mixture inlet temperature. A remarkable broadening of the stability range from 0.6 to 1.0 on preheating to 400 °C was observed. This reveals the potential of pre-heat temperature to improve the dynamic modularity of the burner.     

Combining coal gasification and natural gas reforming for efficient polygeneration

A techno-economic analysis of several process systems to convert coal and natural gas to electricity, methanol, diesel, and gasoline is presented. For these polygeneration systems, a wide range of product portfolios and market conditions are considered, including the implementation of a CO₂ emissions tax policy and optional carbon capture and sequestration technology. A new strategy is proposed in which natural gas reforming is used to cool the gasifier, rather than steam generation. Simulations along with economic analyses show that this strategy provides increased energy efficiency and can be the optimal design choice in many market scenarios.     

催化剂用高温焙烧炉系统的设计开发

针对某厂催化剂的焙烧特性,研制出新型的多通道燃气式高温焙烧炉,并对其系统进行优化。实现了焙烧系统的精确控温和安全保护,可解决原有的辊道窑产能低、能耗高、设备运行成本高等问题。单台设备产能提高3倍,能耗降低20%,催化剂制造成本明显降低,达到增产提质的目的。     

Feasibility study on pressure swing sorption for removing H2S from natural gas

The possibility of removing H₂S from natural gas by applying a pressure swing sorption (PSS) process was experimentally proven. The key technique of the PSS process relies on using a special type of sorbent where solid grains were coated by a layer of liquid. It was shown that the solubility of H₂S in the layer of liquid enlarged the concentration of H₂S at the solid surface and, hence enhanced the adsorption of H₂S on adsorbent. The solubility of H₂S is very sensitive to the partial pressure above the layer of liquid, therefore, the saturated sorbent could be easily regenerated by sweeping the bed of sorbent with nitrogen at ambient temperature and pressure. The sorption capacity as well as the coated sorbent was stable during the operation cycles of sorption/desorption. The new PSS technology of sweetening natural gas is advantageous over the prevailing technologies of today in that both savings of investment and energy cost could be expected.     

Simultaneous measurements of two-dimensional temperature and particle concentration distribution from the image of the pulverized-coal flame

This paper presented a model for simultaneously measuring the two-dimensional temperature and particle concentration distribution from the images of the flame. In order to determine the relationship between a point in the three-dimensional space and its image in the camera, the optical image-formation process was analyzed. The inverse problem of the radiation transfer in the participating medium was studied. The mathematics method to simultaneously solve the temperature and the particle concentration was discussed. To validate the model presented in this paper, a test furnace with the fuels mixed by pulverized-coal and oil was set up. The temperature and particle concentration of a cross section were measured under different coal feed rates. The comparison between the measured temperature by the pyrometer and the calculated temperature according to the flame image proved that the two-dimensional distribution of temperature can be obtained accurately. The particle concentration distribution was reasonable under different cases.     

Comparison of oxidation induction time measurements with values derived from oxidation induction temperature measurements for EPDM and XLPE polymers

Oxidative stability and retained operational utility of polymers used as insulation for electrical cables, such as ethylene propylene diene monomer (EPDM) and crosslinked polyethylene (XLPE), may be assessed by oxidation induction time (OIT) analysis. OIT is measured directly with a differential scanning calorimeter. Using a simplified kinetics model, Gimzewski demonstrated that it is possible to calculate the OIT from measured values of oxidation induction temperature and the activation energy for petroleum lubricants. In the present research, directly measured OITs are compared with OITs calculated from measured oxidation induction temperatures and activation energies for EPDM and XLPE cable insulation. Good agreement between the two methods was demonstrated for these materials.     

天然气和烃油脱汞技术研究进展

综述了天然气和烃油中汞的含量、汞形态和汞的危害以及天然气和烃油中吸附脱汞方面的技术进展。此外,对一些吸附剂的优缺点、吸附机理和影响因素进行了对比分析,对相关的最新研究成果进行了综述。     

Auto-cyclic reactor: Design and evaluation for the removal of unburned methane from emissions of natural gas engines

A non-adiabatic fixed bed auto-cyclic reactor (ACR) consisting of two counter-current concentric compartments was designed and built for removing low concentrations of methane from exhaust gases from natural gas engines. The length was based on simulations by a simple heterogeneous one dimensional model using literature parameters and kinetic data, while the diameter was selected to assure a linear fluid velocity between 0.5 and 2 m/s. Its innovative design consists of a judicious combination of 14 longitudinal fins welded to the outlet part of inner reactor compartment to maximize the heat transfer to the inlet section and highly active pellet type catalyst filling the space between fins to lower the ignition temperature.The experimental ACR pilot unit was loaded by a combination of highly active laboratory prepared catalysts: palladium/alumina pellets and palladium/alumina coated cordierite monoliths. The efficiency of methane removal from air and from synthetic exhaust gas containing 7 vol% CO₂ and 14 vol% H₂O was evaluated under a wide range of operating conditions: temperature from 290 to 500 °C, methane concentration between 500 and 3800 ppm. The reactor performance was monitored in terms of axial temperature profiles and methane conversion both in transient and steady state conditions.Reproducible performance of the ACR was observed even after 1200 h of cumulative operation and complete methane removal was obtained at relatively low temperatures.To simulate the obtained experimental data, a heterogeneous one-dimensional model was developed to suit the final reactor configuration using actual laboratory determined kinetic data. The model described adequately the experimental temperature profiles and methane conversion when heat transfer between the reactor compartments and heat loss were taken into account.     

Computer calculation of heat capacity of natural gases over a wide range of pressure and temperature

This paper presents a method whereby specific heats or heat capacities of natural gases, both sweet and sour, at elevated pressures and temperatures may be made suitable to modern day machine calculation. The method involves developing (1) a correlation for ideal isobaric heat capacity as a function of gas gravity and pseudo reduced temperature over the temperature range of 300 to 1500 K and (2) a mathematical equation for the isobaric heat capacity departure based on accepted thermodynamic principles applied to an equation of state that adequately describes the behavior of gases to which the Standing and Katz Z factor correlation applies. The heat capacity departure equation is applicable over the range of 0.2 ≤ P_r ≤ 15 and 1.05 ≤ T_r ≤ 3. The significance of the method presented here lies in its utility and adaptability to computer applications.