Coal Fluid Research Articles

Coal–Fluid Interfacial Tension in the Coal–Water–CO2 System: Implications for CO2 Sequestration in Coal Seams

Coal–Fluid Interfacial Tension in the Coal–Water–CO₂ System: Implications for CO₂ Sequestration in Coal Seams

Failure analysis of pulverizer pipe elbow in PLTU boiler

Erosion occurs due to several different mechanisms, depending on the composition, size, shape of the eroding particles, speed, angle of impact, and surface composition of the eroded components. The pulverizer pipe elbow has become worn out due to the pulverized coal fluid abrasion flowing on the pipe, which the type is AISI Grade 1026. This study was carried out on the causes of this damage case. Damage to the elbow in the boiler needs to be analyzed for the failure of the elbow so that the damage's cause is known and it becomes a lesson so that the same damage does not occur again. The research aims to: 1. Find out the cause of damage to the pulverizer elbow on the boiler; 2. Know the correct maintenance strategy to increase the reliability of pulverizer pipes in boilers; 3. Simulate erosion due to coal particles in the pulverizer pipe using the Autodesk Simulation Computational Fluid Dynamics software program; 4. Analytical calculations of the erosion rate that occurs at the bend of the pulverizer pipe (elbow) in the boiler. The analysis was done by visual observation, hardness testing, metallographic observation, simulation of the ANSYS CFD program, and analytical calculation. The result of the ANSYS simulation showed that the main factor causing the leakage was erosion-corrosion. In the leaking area, the corrosion concentration was higher than in other areas, indicated by the red color in that area. From the calculation results, it was concluded that the largest erosion rate occurs at the angle of 200 with the value is 4.9548 x 10- 11 m3 / s, the smaller the pulverized coal’s angle of impact crashed the pulverizer pipe elbow, the greater the erosion.

Deciphering the Differential Influence of Organic Additives on Coal Fluidity Development: A First-Principles Investigation

Formation of high-quality coke is essentially controlled by the development of the extended stability of the coal fluid phase during industrial carbonization processes. Stabilization of coal free r...

Predictive Diagnostics of Wet Bottom Boilers Operational States by Calculation of Steam Coal Ash Fluid Temperature

This article deals with the issue of steam coal ash fluid (or fusion) temperature evaluation by mathematical method, based on comparison of statistic values obtained by laboratory analysis. The ash fluid temperature is very important parameter for Wet Bottom Boilers operation states because of quality of slagging. The ash composition has the biggest impact to the operation effectiveness and reliability of the Wet Bottom Boilers. It can directly influence the boiler production. Importance of information on ash fluid temperature increased after more strict of NOx emission limits (below 600 mg/m3) become obliged. WBB were initially designed for optimal operation with high temperatures in combustion chamber, with a production of high amount of NOx (often about 1400 mg/m3). The ash fluid temperature is usually determined by laboratory only, but it requires certain time and costs. Authors tried to bring faster and easier way how to evaluate of ash fluid temperature with acceptable accuracy of the parameter as predictive diagnostics [6] of the future boiler operational states.

A Laboratory Investigation of Permeability of Coal to Supercritical CO2

The kinetics of gas–coal interaction during coalbed methane (CBM) recovery and/or carbon dioxide sequestration in coal has been subject of investigation over past few years. Swelling of coal matrix due to gaseous phase CO2 injection is now well established through laboratory experiments and field validations. Further, fluid exchange or flow in coal alters effective stresses in the underground environment. These significantly affect the permeability characteristics of coal and therefore influence the gas recovery/injection projects. Most research works on coal seam sequestration have been carried out for gas or liquid phase CO2. Considering the pressure–temperature conditions of deep seated coal, studies are now being done on supercritical CO2 flow and adsorption in coal. A newly developed experimental set up was utilized to replicate the underground conditions in laboratory to investigate the (1) initial N2 permeability of coal, (2) supercritical CO2 permeability of coal, (3) effects of CO2 sorption on N2 permeability of coal. The temperature of the set up was maintained at 33 °C while CO2 injection pressures were varied between 11 and 15 MPa at a range of 16–24 MPa confinements, and N2 was used as a relatively neutral medium to estimate the loss in permeability due to supercritical CO2 flow. The results indicate that high adsorption of supercritical CO2 in coal led to significant reduction in permeability. On increasing the confining pressure, further decline in the permeability was recorded. CO2 becomes liquid-like with increasing confining pressures and the coal–fluid interactions change, causing high sorption and matrix swelling, leading to reduced permeability in coal. This explains why substantial decline in the injection rate of CO2 was observed progressively in most CO2 sinks.

Simulation Study on Microscopic Penetration of Coalbed Gas

The fracture system plays a very important role in the coalbed methane migration because they dominate the coal reservoir fluid flow. For this reason, determination of fracture permeability properties control mechanism for forecasting capacity is very important. This thesis fracture morphology of the role of coal-bed methane migration control, in single-phase flow conditions to simulate the fluid nature of the gas, the deduction of the macroscopic permeability, numerical calculations of the impact fracture surface morphology of permeability.

The Numerical Simulation of the Pressure Buildup Process of Cavity Completion for CBM Wells

A numerical model is established to simulate gas injection with high pressure for CBM cave completion. The model is used with the discrete element simulation software UDEC and considers two kinds of fracture morphology exiting in coal bed face cleat and butt cleat. The effective stress of coal matrix, fluid pressure and vector distribution of calculation nodal displacement under the influence of crustal stress is studied as bottom-hole pressure increases. Results show that the model considering cleat system can simulate reservoir fluid migration and matrix deformation more accurately in the process of pressure buildup of cavity completion; the different fluid velocities caused by different directions of face cleat and butt cleat will induce shear fractures for coal bed; the development of coal reservoir extensional fractures can be known by calculating the vector distribution of nodal displacement; the anisotropic formation stresses will make the break and collapse of coal bed more easily.

Thermodynamics of coal-derived fluids: 2. Vapour-liquid equilibria of coal liquid fractions

A thermodynamic model for prediction of vapour-liquid equilibria (VLE) in coal-derived fluids has been developed. The model uses group contribution methods for property evaluations and a continuous thermodynamics approach for VLE computations. A coal fluid is defined by multiple molecular weight distributions, and each distribution is represented by an average molecule with fixed relative proportions of different functional groups. Besides the hydrocarbon group, phenolic, pyridinic and thiophenic groups are used to represent O, N and S heteroatoms. From the results it is concluded that for low-boiling coal liquid fractions the phenolic compounds need to be treated separately, as opposed to the use of a single average molecule to define the coal liquid. Comparison with published data shows that the model is successful in predicting boiling ranges for low-boiling fractions. Failure of the model at higher temperatures is attributed to the binary interaction parameters in the UNIFAC model which are regressed from low-temperature binary VLE data.

San Juan Basin Coal-bed Methane Well Completion Techniques

Coal-bed methane wells in the San Juan basin Fruitland Formation are typically completed by running and cementing casing through the coal interval followed by jet perforation and hydraulic fracture stimulation. Completion design has a significant effect upon productivity, as illustrated by open-hole cavity completions that are producing significantly greater coal-bed methane gas rates than cased and fractured wells. Cavity completions are installed by top-setting overpressured, relatively high-permeability coal seams with casing and drilling through the coal with formation water. Once total depth is reached, air is injected to increase the well pressure, followed by a rapid blow-down to allow coal, water, sand, and shale to collapse into the well and be produced. This presentation summarized these fractured and cavity well completion techniques and quantifies reasons for the productivity differences. Quantitative analyses concerning the effectiveness of hydraulic fracture stimulations will be presented. The quantitative data and information to be presented on cavity completions have been obtained from the Completion Optimization and Assessment Laboratory (COAL) site located 23 mi southwest of Durango, Colorado. The COAL site is a joint research effort between Amoco Production Company, the Gas Research Institute (GRI), and Resource Enterprises, Inc., to quantify open-hole cavity completion behavior. Sufficient informationmore » has been collected from this site to evaluate the reservoir properties and geology, the geometry of the induced cavity, and the effect of the cavity upon coal properties and fluid deliverability. This presentation will be the first time that the data have been discussed publicly.« less

室炉式石炭乾留における軟化層の幅

Width of plastic layer zone was measured in the packed coals heated in a chamber oven by microscopic observation after the rapid quenching to define influen-tial factors related to coals and carbonization conditions. Coals of fluidity in a broader range of temperature formed a wider plastic zone, while more inerts in the coal reduced the width. The carbonization pressure induced 'by volatiles trapped in viscous products ex-panded the plastic zone increasing its width. Broader temperature distribution in the pack-ed coal which was brought about by the migration of fused coal of high fluidity into the zone of lower temperature increased the width, practically by the fusion and dissolution of coal particle by the aid of coal fluid. Such all factors related to the carbonization properties of coals are compared with their petrographic composition and reflectance.

A group contribution and equation of state approach for coal fluid calorimetric properties

This work examines the relationship between the calorimetric properties of coal fluids and their molecular functional group composition. A set of functional groups appropriate for the characterization of the coal fluids is proposed. Coal fluid samples that have had their calorimetric properties measured have been characterized using proton n.m.r., i.r. and elemental analysis. These characterizations are then used in a chemical structural model to determine the composition of the coal liquid in terms of the proposed functional groups. These functional group concentrations are used to estimate the ideal gas calorimetric properties of the fluid using Benson's method. The residual calorimetric properties are then determined using an existing equation of state methodology. The result of the combination of characterization and correlation demonstrates a significant improvement over the existing equation of state based, properties estimation system.

Influence of coal preoxidation and the relation between char structure and gasification potential

A study was carried out to ascertain the effects of coal preoxidation and carbonization conditions on the structure and relative gasification potential of a series of bituminous coal chars. Chars were prepared from two freshly mined bituminous coals and preoxidized samples derived from them. Carbonization conditions included a wide range of heating rate (0.2–10000K s −1), temperature (1073–1273 K) and time (0.25–3600 s). Char properties were characterized in terms of analysis of char morphology, surface area, elemental composition, and gasification reactivity in air. Over the range of conditions used, preoxidation substantially reduced coal fluid behaviour and influenced macroscopic char properties (char morphology). Following slow heating (0.2 K s −1), preoxidized coals yielded chars having higher total surface areas and higher reactivities toward gasification in air than did similar chars prepared from fresh coal. Following rapid heating (10000 K s −1) and short residence times (0.25 s), chars prepared from preoxidized and fresh coals exhibited similar microstructural and chemical properties (surface area, C H ratios, gasification rates). Carbonization time and temperature were found to be the critical parameters influencing char structure and gasification potential.