Test Coke Oven Research Articles

Characteristics of coke pore formation and its effect on solution loss degradation

Pore structure is an important factor that affects coke thermal properties. In order to reveal the formation regularity of coke pore structure, high temperature carbonization experiment of blending coals was carried out in 40 kg test coke oven. The pore structure of different regions and different orientations of the obtained coke was detected by microscope. The ratio of the average pore diameter of the coke to the average wall thickness was highly correlated with the square of porosity. The relationship shows that during coking, the development of the wall thickness is restricted by pore coalescence and coal expansion. The softened coal can form a thicker wall structure only after the pores have coalesced fully without excessive expansion. The four coke pore size distribution curves and pore-wall-thickness distribution curves reflect the quality change of the coal blending. Therefore, the adjustment of a coal blending scheme according to the pore structure distribution curve provides a promising, accurate coal blending method.

Study on the Influence of Coal Blending with Waste Rubber on Coke Quality

In order to investigate the influence of coal blending with waste rubber on coke quality, the pyrolysis performance of rubber powder was analyzed, and the coking experiment of coal blending was carried out in 70 kg test coke oven. The experimental results showed that the pyrolysis range of waste rubber was similar to that of blended coal by analyzing the pyrolysis characteristics of waste rubber. The ash content (Ad), coke reactivity index (CRI) and coke strength after reactivity (CSR) would decrease, while the sulfur content (St, d) of coke would increase with the increasing of coal blending ratio of waste rubber. The specific surface area of coke increased from 1.5m2/g to 3.5m2/g, the Lc of coke microcrystalline structure and the degree of graphitization decreased gradually with increasing the ratio of waste rubber from 0% to 6% in coal blending. The optical structure of coke showed that the fine-grained mosaic structure increased and the degree of anisotropy of coke (OTI) decreased.

Improving coke strength prediction using automated coal petrography

A range of Australian and overseas coals with a mean maximum vitrinite reflectance (Ro, max) range of 0.68–1.71% were carbonized in a test coke oven. Coal properties were characterized using XRF, XRD and automated imaging of polished sections of discrete coal grains. The Full Maceral Reflectance (FMR) parameter was calculated from the reflectance data and was correlated with coal as well as coke properties. The Ro, max values and the vitrinite estimates from the semi-automated microscopic technique indicated a good correlation with similar data based on manual point count analysis. The FMR parameter is shown to increase with increasing carbon content, structural ordering of carbon and decrease with increasing volatile matter. The FMR parameter of coal was related to cold coke strength DI15150 and coke strength after reaction (CSR). The FMR parameter was modified by diluting the contribution of high reflectance coal grains as well as incorporating the effect of ash contribution to propose a combined coal index (CCI). The new coal index is shown to improve the accuracy of coke strength prediction. The combined coal index provides a promising objective measurement based alternative for predicting coke strength.

The cause of the uneven carbonization process in wet coal charging in coke oven chamber

In the case of the wet coal charging process in coke oven chamber, it is known that the coking process is uneven and a local carbonization delay occurs. The reason was investigated through a laboratory-scale experiment and a quantitative estimation. A partial carbonization test in a test coke oven replicated the uneven plastic layer and local carbonization delay. It was revealed that most of the gas generated in the uncarbonized coal layer results from the evaporation of condensed water and that steam can break through the plastic layer in a test coke oven. Moreover, the order estimation implied that steam that generates in the uncarbonized coal layer and breaks through the plastic layer has sufficient heat capacity to cool the heating wall and delay the carbonization. It was also shown that the steam pressure peak measured in a commercial coke oven is much lower than the estimated steam pressure in this study assuming steam not breaking through the plastic layer. The above-mentioned results and quantitative investigation strongly support the ‘steam breaking through the plastic layer’ theory proposed by Dr. Rohde that an uneven carbonization process is caused by vaporized coal moisture breaking through the plastic layer at definite, unforeseeable points, which results in cooling of the wall by the steam flow.

中低温乾留コークスの再加熱挙動

Medium temperature carbonization is one of the technologies to increase productivity of a coke oven. However, strength of lower temperature coke is lower than that of high temperature coke. Then technology covering the decrease of coke strength will be necessary for accompanying the medium temperature carbonization. Heating medium temperature coke further to the high temperature carbonization level after pushed off the oven is one of the methods to modify coke quality.Medium temperature coke was made in a test coke oven and then heated further in a vessel by an electric heater passing model heating gas. The effect of heating conditions and of reactions with reactive gas on coke strength was investigated. It took coke less than one hour to be fully modified at the heating temperature. Carbonized coke below 750°C in a coke oven at oven center did not sufficiently recover its strength even in the non-reactive gas. Coke strength decreased in proportion to the weight loss by the reaction with carbon dioxide or steam similarly. However, coke strength slightly decreased in a reaction with oxygen.Change in gas composition along with flow was measured in a coke bed of more than 1.0 m. From the behavior of reactions between coke and reactive gas, their reaction rates were analyzed. Following these results, further heating situation in coke dry quencher (CDQ) by air injection was simulated and it is confirmed that medium temperature coke can be modified in its strength to that of high temperature coke in spite of the weakening of the coke strength by the reaction loss.

The effect of volume change of coal during carbonization in the direction of coke oven width on the internal gas pressure in the plastic layer

The coking pressure in a coke oven, which is caused by the internal gas pressure in the coal plastic layer, is determined by the gas permeability of the layer. The gas permeability of the plastic layer depends on its density as well as the physical property of the plastic coal itself. The plastic layer is sandwiched between the coke and the resolidifying layers and the coal layer and the effect of the volume change of these outer layers in the direction of coke oven width, i.e. contraction and compression, on the density of the plastic layer and the internal gas pressure was studied. A sandwich carbonization test, where different kinds of coals were charged in the test coke oven, showed that the internal gas pressure depends not only on the kind of coal in the plastic phase but also on the kind of coal in the resolidifying and the coke phases near the oven walls. The relative volume of coke transformed from the unit volume of coal was measured using an X-ray CT scanner and it varied greatly across the coke oven width depending on the kinds of coals. The volume change of coal during carbonization in the direction of coke oven width affects the density of the plastic layer and the internal gas pressure. The relative volume of semicoke and coke transformed from the unit volume of coal near the oven walls is higher for a high coking pressure coal than that for a low coking pressure coal. This causes the plastic layer to have a high density and the generation of dangerously high internal gas pressure in the oven center.

Internal Gas Pressure Characteristics Generated during Coal Carbonization in a Coke Oven

Coal carbonization for various kinds of single coals, coal blends, and operating conditions has been carried out in a movable-wall test coke oven (0.18 mW × 0.4 mH × 0.45 mL) to investigate the coking pressure behavior. The internal gas pressure and its corresponding temperature at the coal charge center were measured using the probe with thermocouple. Internal gas pressure of single coals increases with an increase of coking capacity and a decrease of volatile matter content. The internal gas pressure and the coke strength of coal blends mixed with single coals mainly depend on the blending ratio of a given coal in coal blends. With decreasing moisture content of coal blends, heating rate at the coal charge center decreases and internal gas pressure exponentially increases. Bulk density of coal blends exponentially increases with decreasing moisture content. Also, coke strength linearly increases with a decrease of coal moisture content. With increasing heating-wall temperature, internal gas pressure of ...

99/02971 Coking pressure behavior during coal carbonization in a movable-wall test coke oven

The paper gives a general overview of characteristics of coking in industrial catalytic processes. Although there may be similarities in coking mechanism, the big differences in deactivation rates result in different operational strategies and reactor systems.

乾留初期におけるコークス炉内炉幅方向水分移動機構

In order to clarify the moisture transfer mechanism, moisture distribution across the oven width at the early stage of carbonization has been investigated using the test coke oven with the upper heating wall. There is a region having a maximum moisture content below 100°C because of moisture condensation. Subsequently, as temperature is elevated close to 100°C, remarkable moisture vaporization has taken place so that the moisture in coal decreases rapidly. However, there remains a little moisture in coal beyond 100°C.Two dimensional coke oven mathematical model was hence updated by introducing this moisture transfer mechanism.

Determination of Gas Flow Pattern in a Test Coke Oven Charge and Its Time Variation by Tracer Technique.

The travel path of produced gas in a coke oven has always been of interest. However, few studies have been reported on this subject. In the present study, a tracer technique was employed for the determination of the path of gas in a test coke oven with width of 45 cm, and charge height of 85 cm. Three tubes were inserted horizontally from the coke side at 15.6 cm high (L) and at 0, 8 and 16 cm from the center of the width. Two kinds of tracer gas were uniformly introudced along the tubes. Other six tubes were also inserted at 36 (M) and 54 (H) cm high and at 0, 8 and 22 cm from the center, and the gas in the oven was withdrawn from their ends located at the center of the length of the oven. The gas sampling was conducted every two hours through the sampling tubes and from the exit ascension pipe, where the total flow rate of the produced gas was determined from the concentrations of tracers. Ar injected at L16 was hardly detected inside the charge (0 or 8 cm from the center) at the middle stage of carbonization. The flow rate of produced gas at the vicinity of the wall (22 cm from the center) was determined from mass balance of Ar assuming that all Ar flowed there. Rates of gas cross from the center side to the wall side was evaluated from the concentration profile of He introduced into the coal layer. At the middle stage, most of the produced gas passed upward in the coke layer and no cross flow was found. This phenomena were to be explained by large flow resistance of the plastic zone. At the last stage, both of the tracers were uniformly distributed all over the coke layer.

Analysis of steam flow in coke oven chamber by test coke ovens and a two-dimensional mathematical model.

The deviation in the carbonization rate in the coke oven chamber has been investigated with the use of test coke ovens and a 2-dimensional mathematical model.In the measurement using a 250 kg test coke oven, in the case of using a wet coal charge, there were several points of delay in the carbonization rate at random times, but in the case of a dry coal charge, there were no points of delay and the carbonization progressed uniformly. It was confirmed that the deviation in the carbonization rate was affected by the moisture content of the charged coal.In order to evaluate flow pattern and heat transfer caused by the steam and the decomposition gas during carbonization, a 2-dimensional gas flow mathematical model was developed. This model consists of mass, energy involving terms of convection and momentum balance equations in both the gas and solid phases. It was confirmed that temperature change, changes in gas pressure and steam flow pattern in a test coke oven with the heating wall at the upper portion were estimated by this model. In the model calculation, the coke fissures and a local distribution of the bulk density affected the steam flow and caused a deviation in the carbonization rate.

セミコークス化過程におけるコークス性状挙動

In order to clarify the influence of carbonization temperature on coke qualities and oven operations, change of coke properties during calcination (500-1000°C) was investigated. The sample cokes were carbonized by a special electric test coke oven in which a heating wall is set on the upper side. Further coke productivity and coke qualities in the case of medium temperature carbonization were estimated by a mathematical model for carbonization.The following findings were obtained.(1) With the increase of carbonization temperature, microstrength of coke increases, while crystallite size of carbon does not increase untill 800°C. These phenomena are presumed to be attributed to the fact that three dimensional accumlation of crystallite precedes the growth of its size.(2) It is estimated by the model that the coke strength is sufficient in the medium temperature carbonization, although coke reactivity is slightly insufficient.

Coking behaviour of coals recovered from slurry pipelines using a selective agglomeration technique

The coking behaviour of coking coals after transport in experimental slurry pipelines and recovery from the slurry by oil agglomeration has been studied using a 100 kg test coke oven. It was shown that excellent quality coke could be made, in some cases stronger than would be produced from the same coals after conventional preparation. The improved coke strength was due to the fine grinding of the coals which was a characteristic of the agglomeration technique. The presence of diesel oil or kerosene had a retarding effect on heat transfer and in some conditions decreased coke oven productivity. Normal productivity was observed when tar was used as the agglomeration agent. A two-step process with recovery and re-use of oil is suggested and the potential improvement in yields of blast furnace coke per tonne of raw coal are presented.