Steam Stream Research Articles

Combination of autothermal reforming with water-gas-shift reaction—small-scale testing of different water-gas-shift catalysts

Abstract The amount of carbon monoxide in the reformate of the autothermal reforming (ATR) of liquid hydrocarbons can be significantly reduced by means of the water-gas-shift (WGS) reaction. It is possible to directly feed the reformate from the ATR of liquid hydrocarbons to the WGS reactor without deactivation of the WGS catalyst. In a first step, the dry reformate from the ATR and a separately fed stream of steam were used to conduct the WGS reaction. Special emphasis was given to the chemical composition of the reformate which under convenient reaction conditions did not feature any detrimental higher aliphatic or aromatic hydrocarbons. Applying these premises, no catalyst deactivation could be observed. Strong differences concerning the catalytic activity between the three investigated commercial monolithic catalysts could be observed. The most active one showed a very promising catalytic behaviour. At a gas hourly space velocity (GHSV) of 12,250 h −1 , CO conversion amounted to 85% at 280 °C. This result reduces the CO concentration in the reformate from 6.1 to about 0.9 vol.%. In a second step, also the non-converted water from the ATR was fed to the reactor for the WGS reaction together with the additional components of the reformate. In this case, also the amount of total carbon dissolved in the water was analysed, which might — after adsorption — have a deleterious effect on the accessibility of the active sites of the WGS catalyst. No catalyst deactivation was observed within almost 90 h under ATR conditions generating only traces of carbon dissolved in the water.

Adsorption removal of pollutants by active cokes produced from sludge in the energy recycle process of wastes

This study proposes a recycling system of sludge into active cokes and the fundamental examinations for the application were carried out. In the system, active cokes were produced by carbonizing pellets of sludge in a steam stream. Pyrolysis gas yielded by carbonization can be available to a fuel for a steam generation boiler. The exhaust heat from the boiler is used sequentially for drying of sludge. The active cokes are applied to the adsorbent for dioxin removal in exhaust gas from incinerators of wastes, or for purification of gas obtained in a gasification process of wastes, particularly removal of H 2S. The used adsorbent is not recycled, but incinerated in the furnace without a desorption process to decompose adsorbed dioxin or to oxidize H 2S for a sequential desulfurization process of SO 2. Dry pellets of sludge were carbonized in a quartz tube reactor under various atmospheres. The micro pore structure and the adsorption performance of the cokes produced without activation process were examined. The micro pore structure was influenced by the temperature, the sort of flow gas (N 2, CO 2 and steam) and carbonization time, and the active cokes produced under the condition of the temperature 823 K for 60 min in the steam atmosphere had a largest specific surface area in the diameter less than 5 nm. The amount of benzene adsorption as an alternative substance of dioxin into the active cokes had a similar quality to a commercial active char produced from coal if it was evaluated by adsorption per a unit specific surface area. This fundamental knowledge must be reflected to an optimum design for development of a simple continuous process to produce the active cokes by a fluidized bed type of the carbonization furnace.

Experimental Evaluation of Triangular Microgrooved on a Condensing Surface

The addition of microgrooves to a condensing surface has been proposed to reduce the film thickness to increase the condensation heat transfer coefficient. Microgrooves promote the removal of condensate via the capillary pressure induced by the difference in curvature of the meniscus formed in the groove. Triangular microgrooves of different apex angles (45 and 60 deg) and width (300 and 500 μm) were machined on several copper plates (140 x 25.4 mm), and the resulting film condensation was observed at a macroscopic scale. Experimental results demonstrated the beneficial presence of the grooves by achieving enhancement factors up to 2.22 in the Nusselt number. This enhancement was separated to allow determination of the individual contributions of the gravitational body force and the effect of the steam stream velocity. Visual observation of the phenomenon demonstrated that the microgrooves evaluated had an active length, but that the effect of this active length was easily obscured by the macroscopic phenomenon that produced a thick condensate film over a majority of the length of the plate. Conclusions from the current research indicated that the microgrooves were able to improve the heat transfer process, even at a macroscopic length scale, because they added an additional path through which the condensate could be removed. When conditions similar to microscale condensation were obtained, the effect of the grooves was isolated and found to be very satisfactory.

Antibacterial activated carbon fiber derived from methyl methacrylate-grafted phenolic resin fiber

Methyl methacrylate-grafted phenolic resin fiber was soaked in AgNO 3 aqueous solution to support Ag + by ion exchange reaction. The fiber supporting Ag + was carbonized at 900°C for 30 min in a nitrogen atmosphere, followed by activation at 900°C under a stream of steam. One of the activated fibers contained 0.58 wt% of silver and showed 2100 m 2/g of specific surface area and 200 MPa of tensile strength. This fiber showed antibacterial activity against Staphylococcus aureus and Escherichia coli before and after soaking in the flowing tap water for 20 days. The amount of Ag + dissolved from the fiber into the water is discussed from a viewpoint of practical use.

Antibacterial activated carbon fibre derived from phenolic resin fibre by use of co-graftpolymerization

Phenolic-resin fibre was co-graftpolymerized with methyl methacrylate and methacrylic acid. The weight of the fibre increased by 26% after grafting. The grafted fibre was soaked in silvernitrate solution to introduce silver ion on methacrylic acid in the graft by an ion-exchange reaction, followed by carbonization at 900 °C for 30 min under a nitrogen stream and activation at 900 °C under a steam stream. After activation for 40 min, the resulting fibre showed a silver content of 8.3 wt% a specific surface area of 1300 m2g−1 and antimicrobial activity against Staphylococcus aureus and Escherichia coli. The average crystallite size of the silver in this fibre was 30 nm, which suggests co-graftpolymerization is a useful technique to disperse fine silver particles in the activated carbon fibre. After soaking in flowing tap water for 10 and 20 days, this activated carbon fibre lost about 50 wt% of silver but kept its antibacterial activity.

Preparation of pitch-based antibacterial activated carbon fiber

Silver acetate dissolved in quinoline was mixed thoroughly with the spinnable isotropic petroleum pitch dissolved in the same solvent. After removing the quinoline, the resulting pitch was spun, stabilized, carbonized, and finally activated at 900°C under a stream of steam. The fiber with 33 wt% yield after activation contained 0.63 wt% of fine silver particles and showed N 2-BET specific surface area of 740 m 2/g. It showed antibacterial activity against Staphylococcus aureus and Escherichia coli, before and after soaking in flowing tap water for 20 days. How to improve spinnability of the pitch containing silver acetate and how to increase the specific surface area effectively by the activation process are problems remaining to be solved.

HEAT TRANSFER CHARACTERISTICS AT EVAPORATING WATER SURFACE IN LAMINAR STREAM OF SUPERHEATED STEAM

ABSTRACT The heat transfer characteristics at a horizontal evaporating water surface exposed to a laminar stream of superheated stenm, which is a radiation participating real gas, have been investigated and compared to those of a hot air flow by means of a real-time laser holographic inter ferometry. Water surface temperatures and temperature profiles within the laminar boundary layer were measured precisely under adiabatic evaporation conditions. Temperature gradients at the water surface were determined and local Nusselt numbers were estimated. Those experimental results were compared to the analytical results obtained by solving the laminar boundary equations. It can be concluded here that both temperature profiles within the laminar boundary layer and heat transfer characteristics at the evaporating water surface in superheated steam stream are quite different from those in hot air flow due to an influence of gas radiation from superheated steam.

THERMAL PERFORMANCE AND EVALUATION OF SIPERHEATED STEM DRYING SYSTEM USING SOLAR-ASSISTED ABSORPTION HEAT TRANSFORMER

ABSTRACT This paper summarizes the main results of our study carried out under the priority-area research “Energy Conversion and Utilization with High Efficiency” supported by the grant-in-aid of scientific research from the Ministry of Education, Science and Culture of Japan. In the research we focused on applications of solar energy utilization for industrial drying systems. In this paper a new concept of a closed drying system with superheated steam provided from a temperature boosting type heat pump (absorption type heat transformer) was proposed. The heat transformer is driven directly by heat from a solar collector. The performance for different three drying periods and a number of factors affecting it were predicted by a computer simulation. Furthermore the heat and mass transfer characteristics of water evaporation into superheated steam stream by radiative and convective heating were indicated experimentally. It was concluded that the system would be useful for industries where high temperature (...

Development of a method for analyzing volatiles from foodstuff matrices, including microextraction by demixture. Application to the analysis of grapes

This paper presents a general method for analyzing volatiles from foodstuff samples, and its application to the analysis of grapes. The method includes steam stream distillation, microextraction and chromatographic analysis, and all aspects of the analysis, including sample treatment, are discussed. Data on recovery and reproducibility are given. The method allows to prepare samples for quantitative chromatographic analysis in only one hour and to quantitate the volatiles present in the original samples at concentrations between 0.2 and 2000 mg 1−1 with FID detection.

Determination of fluorine and chlorine in geological materials by induction furnace pyrohydrolysis and standard-addition ion-selective electrode measurement

Fluorine and chlorine in geological materials are volatilized by pyrohydrolysis at about 1150° in a stream of oxygen (1000 ml/min) plus steam in an induction furnace. The catalyst is a 7:2:1 mixture of silica gel, tungstic oxide and potassium dihydrogen phosphate. The sample/catalyst mixture is pyrohydrolysed in a re-usable alumina crucible (already containing four drops of 1 + 3 phosphoric acid) inserted in a silica-enclosed graphite crucible. The absorption solution is buffered at pH 6.5 and spiked with 1.6 μg of fluoride and 16 μg of chloride per g of solution, to ensure rapid and linear electrode response during subsequent standard-addition measurement. The simple plastic absorption vessel has ⪢99.5% efficiency. The 3 s limits of detection are 5–10 μg/g and 40–100 μg/g for fluorine and chlorine respectively. The procedure is unsuitable for determining chlorine in coal.

A pyrohydrolytic method for the determination of low fluorine concentrations in coal and minerals

Techniques are described for the pyrohydrolysis of a range of sample materials in a silica tube furnace. Samples are mixed with a catalyst and combusted ar 1200°C in a stream of oxygen and steam, and the liberated fluorine is absorbed in solutions appropriate to either ion-selective electrode or ion-chromatographic measurement. Catalyst composition, furnace temperature, and gas flow rates are particular variables discussed with respect to recovery of fluorine ar concentrations up to about 5% (w/w). Recovery and precision are favourable compared with those obtained by the alternative peroxide fusion and oxygen bomb combustion methods for coal analyses. Relative standard deviation is less than 0.05 for most samples. Results agree with certified values of available reference materials including ores and rocks, while new data are provided for several non-certified reference materials.

STEAM STREAM DRYING

ABSTRACT Steam stream drying is minimized energy expenditure for water removal. A fast moving steam stream at low pressure and moderate superheat is charged with moist material. Heat is added to the stream at a rate equal to the desuperheating flux caused by the suspended moist material as it dries. Rapidly dewatered macerial is separated from the transport steam via a cyclone or baghouse. Steam generated from material moisture is continuously relieved, and the remaining steam is recycled to the moist material charge point.

１・１／４Ｃｒ‐１／２Ｍｏ鋼の低炭素化とその溶接割れ防止

The erosion/corrosion damage symptom was experienced in a part of units made of carbon steel in nuclear power plants. The damage was erosion/corrosion one caused by the wet steam stream containing little dissolved oxygen. Therefore, erosion/corrosion tests were executed about various kinds of steel having different additional elements. As the results of the tests, it has been concluded that 11/4Cr-1/2Mo steel has excellent erosion/corrosion resistance. This material was applied to actual plants to solve the above problem for the time being.However, since this 11/4Cr-1/2Mo steel is heat-resisting steel for hot pressure vessels primarily, it contains chromium and molybdenum in addition to about 0.16% of carbon. It is necessary for the prevention of cracking in the welds of this steel to keep preheat and interpass temperature at 200 to 350°C during welding and perform dehydrogen heating process at 400°C for 30 min after completion of welding. These procedure is very much complicated, as compared with the procedure for the welding of carbon steel. Furthermore, the material's strength is not so much important at the elevated temperature higher than 400°C, because the maximum temperature of the steam is 282°C in the units concern. Therefore, the reduction of carbon content has been investigated, for the improvement of the weldability of 11/4Cr-1/2Mo steel. The effect of carbon content has been examined on tensile properties, Charpy absorved energy, the resistance against weld cracking and erosion/corrosion properties. As the results of the investigations, (1) the carbon content can be reduced to 0.07 to 0.10% in case of annealed type of steel, securing its tensile properties and improving weldability, (2) the annealed type of steel can be welded free from cracking without dehydrogen heating process, keeping the interpass temperature more than 225°C, and (3) the hydrogen diffusion parameter τ=Σi(Di/Δti) can be used to prevent multi-pass weld cracking.

Evaporation of water into a laminar stream of air and superheated steam

A numerical investigation was conducted to study the evaporation of water into a laminar stream of air, humid air and superheated steam. Results were obtained both for variable properties and for constant properties using the one-third rule. It was shown that below a certain temperature of the free stream, named the inversion temperature, water evaporation decreases as the humidity of air increases; and above the inversion temperature, water evaporation increases as the humidity of air increases. The constant-property approximation using the one-third rule yields accurate results for the evaporation rate of water except when the free stream is mostly steam at high temperature.

Preparative gas-liquid chromatography in steam

We were the first to run the preparative separation of compounds by gas-liquid chromatography in a stream of steam. The substantial advantages of the process in the separation of mixtures of polar compounds like amines, free aliphatic acids, aliphatic alcohols, and other compounds, were demonstrated.

Generalization of test data pertaining to the mean heat transfer coefficient for tube bundles in a turbulent longitudinal stream of air and superheated steam

A method has been developed for the generalization of test data on heat transfer which takes into account the effects of the temperature factor and of the bundle geometry. From a compilation and an analysis of the test data have come out new and reliable recommendations for the thermal design of heat exchangers.

A rapid method for the determination of fluoride in silicate rocks

A rapid method for the analysis of fluoride in silicate rocks is described. The sample is heated in a stream of oxygen and superheated steam (pyrohydrolysis), and fluoride determined spectrophotometrically as the purple-blue double complex with the cerium chelate of alizarin fluorine blue (3-maminomethylalizarin- NN-diacetic acid). 5 p.p.m. F − can readily be determined using 1 g of sample.

Paper 24: The Development of a Controlled Wet-Steam Generator

This paper describes what is believed to be the first attempt to make a wet-steam ‘wind’ tunnel. Saturated water is sprayed from a small high-speed rotating disc so that the globules are entrained by a stream of saturated steam at the same temperature in which the disc is immersed. The tunnel is designed for a maximum steam speed of 30 ft/sec in a circular working section of 16-in diameter with steam pressures ranging from a full vacuum to 10 lb/in2 gauge. The entrained globules range in size from 5 to 100 micron, and the minimum nominal dryness fraction is 94 per cent. A sampling technique was developed based on the impressions made by the globules on a prepared slide, and an attempt is made to relate the globule size to the disc size and speed, the injection water flow and the physical characteristics of the saturated liquid and vapour. Globule trajectories were calculated by computer allowing for variation of drag coefficient and acceleration of the entraining steam. In the paper the design of the equipment and the problems encountered both in generating the wet steam and in determining the size of the globules are discussed.

Preparation of levoglucosan (?-d-1,6-anhydroglucopyranose) by the thermodegradation of cellulose in a stream of superheated steam under reduced pressure

It was shown that it is possible to prepare levoglucosan (β-D-1,6-anhydroglucopyranose) in a yield of not less than 40% by the thermodegradation of cellulose at low pressure with superheated steam as heat-transfer medium.

Adaptation of the volumetric‐evolution method for carbonates in soaps to synthetic detergents

SummaryThe suggested modifications make it possible to adapt the original method of Hitchcock‐Divine to alkyl benzene sulfonates and similar types of synthetics which cannot be hydrolyzed. Alcohol instead of water solutions of the sample are used to eliminate foaming. An electric mantle, a CO2‐free stream of steam, or both can be used to prevent the solutions from “bumping” while boiling under vacuum.