Coal-water Slurry Containing Petrochemicals Research Articles

An experimental investigation into ignition and combustion of groups of slurry fuel droplets containing high concentrations of water

In this study, the main ignition and combustion characteristics have been compared for droplet groups of a coal-water slurry containing petrochemicals (CWSP), as well as oil, surrounded by water droplets. Thus, in a combustion chamber, we simulated the ignition and combustion conditions of a heterogeneous fuel aerosol that can be formed when jets of different liquids cross or when multi-component flows delaminate. It was shown that a decrease in the distance between droplets (from 10 mm to 2 mm, i.e. to the typical fuel droplet size) reduces the gas-phase and heterogeneous ignition delay times of oil and CWSP by 30% on average. The evaporation times of water droplets decrease by approximately 25%, if the distance between them increases in the combustion chamber. It was established that the ignition delay times of oil and coal-water slurry containing petrochemicals increased by 20–40% and 40–70%, respectively, when a combustible liquid droplet was in the center with six water droplets around it. The experimental results are a database for the development of efficient technologies of injecting multi-component fuel into combustion chambers.

Influence of the initial temperature of coal water slurries containing petrochemicals on their ignition characteristics

In this research, we determined how the low temperatures of coal water slurry containing petrochemicals (CWSP) influence the ignition conditions. We have included research findings on fuel compositions that filter cakes of non-baking, low-caking and gas coals, and typical used turbine oil. The main research parameters are as follows: ignition delay time; minimum temperature sufficient for sustainable ignition; complete combustion time; maximum temperature of a droplet during the combustion process. In the experiments, we varied the following factors: types of solid and liquid components, temperature in the combustion chamber, initial size of fuel droplets. It was found that when CWSPs of five different compositions were cooled down from 20 °C to 0 °C, the ignition delay times decreased by 11–35%. The change in minimum ignition temperatures was insignificant. The difference between the maximum combustion temperatures of cooled down CWSPs as compared to ones of room-temperature fuels was 20–50 °C. The decrease in the initial fuel temperature also had very little effect on the mass of the unburnt residue and the combustion duration. Regardless of the cooling temperature, CWSP ignition delay times decreased by 70–77% when the temperature in the model furnace varied in the range of 400–900 °C. An increase in the initial temperature from 20 °C to 60 °C did not have a pronounced effect on the combustion temperature, ignition temperature, combustion temperature or ignition delay time.

Ignition of a Droplet of Composite Liquid Fuel in a Vortex Combustion Chamber

Experimental study results of a droplet ignition and combustion were obtained for coal-water slurry containing petrochemicals (CWSP) prepared from coal processing waste, low-grade coal and waste petroleum products. A comparative analysis of process characteristics were carried out in different conditions of fuel droplet interaction with heated air flow: droplet soars in air flow in a vortex combustion chamber, droplet soars in ascending air flow in a cone-shaped combustion chamber, and droplet is placed in a thermocouple junction and motionless in air flow. The size (initial radii) of CWSP droplet was varied in the range of 0.5–1.5 mm. The ignition delay time of fuel was determined by the intensity of the visible glow in the vicinity of the droplet during CWSP combustion. It was established (under similar conditions) that ignition delay time of CWSP droplets in the combustion chamber is lower in 2–3.5 times than similar characteristic in conditions of motionless droplet placed in a thermocouple junction. The average value of ignition delay time of CWSP droplet is 3–12 s in conditions of oxidizer temperature is 600–850 K. Obtained experimental results were explained by the influence of heat and mass transfer processes in the droplet vicinity on ignition characteristics in different conditions of CWSP droplet interaction with heated air flow. Experimental results are of interest for the development of combustion technology of promising fuel for thermal power engineering.

Environmental indicators of the combustion of prospective coal water slurry containing petrochemicals

Negative environmental impact of coal combustion has been known to humankind for a fairly long time. Sulfur and nitrogen oxides are considered the most dangerous anthropogenic emissions. A possible solution to this problem is replacing coal dust combustion with that of coal water slurry containing petrochemicals (CWSP). Coal processing wastes and used combustible liquids (oils, sludge, resins) are promising in terms of their economic and energy yield characteristics. However, no research has yet been conducted on the environmental indicators of fuels based on CWSP. The present work contains the findings of the research of CO, CO2, NOx, SOx emissions from the combustion of coals and CWSPs produced from coal processing waste (filter cakes). It is demonstrated for the first time that the concentrations of dangerous emissions from the combustion of CWSPs (carbon oxide and dioxide), even when combustible heavy liquid fractions are added, are not worse than those of coal. As for the concentration of sulfur and nitrogen oxides, it is significantly lower for CWSPs combustion as compared to coals. The presented research findings illustrate the prospects of the wide use of CWSPs as a fuel that is cheap and beneficial, in terms of both energy output and ecology, as compared to coal.

Conditions of Stable Ignition of Coal-Water Slurry Containing Petrochemicals Based on Carbon Residue of Tire Pyrolysis

The results of experimental investigations of ignition of single droplets (radius of 0.5–1.5 mm) of coal-water slurry containing petrochemicals (CWSP) in a stream of air (oxidizer) with a temperature of 600–1200 K and velocity of 0.5–5 m/sec are presented. Carbon residue (particle sizes of 80–100 μm) from pyrolysis of used automobile tires, water, and exhausted engine, turbine and transformer oils were used as the main fuel components. The times of ignition delay and complete combustion of CWSP droplets were determined atvarying concentrations of the components in the ranges corresponding to modern combustion and burner devices. The conditions at which stable combustion of CWSP is initiated were determined.

Environmental Potential of Using Coal-Processing Waste as the Primary and Secondary Fuel for Energy Providers

The main anthropogenic emissions (CO, CO2, NOx, SOx) produced by the processing (combustion) of wastes (coal filter cakes) were measured directly for the first time. The research considered the most widespread coal filter cakes: those of nonbaking, low-caking, coking, flame, and gas coals. These filter cakes are regarded as promising components for the technologies of coal-water slurry (CWS) and coal-water slurry containing petrochemicals (CWSP). According to our estimates, the annual increment of such wastes in the world is as high as 100 million tons. Consequently, the effective utilization of these wastes in the power industry is of high interest. The evaluation of hazardous emissions from the combustion of such wastes shows that filter cakes produce a similar amount of CO and CO2 as the initially-used coals but filter cakes are more cost-effective. We have established that CWS and CWSP technologies can be used to reduce NOx and SOx emissions. To reduce CO and CO2 emissions when burning filter cakes, we need to switch to low-temperature combustion. Lowering the combustion temperature of filter cakes from 850 °C down to 650 °C decreases the underburning insignificantly while decreasing CO and CO2 emissions by 30–40%.

Influence of the shape of soaring particle based on coal-water slurry containing petrochemicals on ignition characteristics

This paper examines the laws of stable ignition of organic coal-water slurry containing petrochemicals (CWSP). The CWSP is based on the filter cake of coal and scavenge oil. The experiments are performed for individual CWSP particles soaring in a special set-up. The temperature and velocity of an oxidizer flow are varied between 500-1200 K, and 0.5-3 m/s. The dimensions (longitudinal and transverse) of particles range are from 0.5 mm to 5 mm. The study indicates how the shape of a fuel particle (sphere, ellipsoid, and polyhedron) influences its ignition characteristics (delay time, minimum temperature, modes, stages). Based on the experimental results, the paper explains why the surface configuration of particles influences the conditions of heat transfer with an oxidizer. The results obtained for soaring particles are compared with the results for fixed CWSP particles having different surface configurations (sphere, ellipsoid, and polyhedron). In general, the study may contribute to the expansion of the fuel resource base. The experimental data may be used for the development of the technologies of burning CWSP prepared by recycling traditional fuels. As a result of this study, several recommendations for the practical application of research results are made.

Maximum combustion temperature for coal-water slurry containing petrochemicals

This study examines the temperature change of droplets of coal-water slurry containing petrochemicals (CWSP). The slurry consists of coal and oil processing waste. The temperature of oxidant in a modelled combustion chamber is varied between 600 and 1200 K. The initial size (radius) of CWSP droplets varied in the range of 0.5–3 mm. The study identifies typical temperature trends at the center and on the surface of the CWSP droplet. The temperature trends represent the following stages: (i) heating of fuel, (ii) evaporation of water and a liquid combustible component, (iii) thermal decomposition of coal and yield of volatiles, (iv) gas phase ignition of volatiles together with vapor of the combustible liquid, and (v) heterogeneous ignition of carbon and its burnout. Moreover, these trends indicate the maximum combustion temperatures of CWSP that reflect corresponding heat release. The study specifies the parameters which influence the maximum combustion temperature: fuel component composition, properties of components, droplet size, and the oxidant temperature. Finally, the study defines the minimum ignition temperatures and delay times of sustainable combustion initiation that characterize the ignition inertia. The knowledge of influence of these factors will allow one to predict the optimal conditions for the combustion of the CWSP.

Ignition of the Coal–Water Slurry Containing Petrochemicals and Charcoal

The lack of effective technologies to use coal processing waste and waste flammable liquids is a major research and development problem. To address this problem, we study the ignition characteristics and conditions for coal–water slurries (CWS) based on these wastes. The key challenge posed by the wastes under study is their poor reactivity (they require more power resources for sustainable ignition). Therefore, this paper suggests adding a highly reactive material (charcoal) in a low concentration to coal–water-slurry containing petrochemicals (CWSP) based on wastes. Individual CWSP droplets are studied in a model combustion chamber. The integral characteristics of the processes under study (ignition delay time and minimum oxidizer temperatures sufficient for ignition) are determined for a CWSP droplet of 0.5–2 mm in radius fixed at the junction of a low-inertia thermocouple using a high-speed (up to 105 fps) video camera and Tema Automotive software. We compare the ignition characteristics of CWSP compo...

Ignition Characteristics of Coal–Water Slurry Containing Petrochemicals Based on Coal of Varying Degrees of Metamorphism

This paper examines a coal–water slurry containing petrochemicals (CWSP) based on lignite, bituminous coal, anthracite, and typical waste—carbon residue obtained from the pyrolysis of tires. Waste motor oil is used as a liquid fuel component of the slurry. The study of CWSP ignition is performed via placing a fuel droplet on a low-inertia thermocouple junction (junction diameter is 0.1 mm; thermal inertia is less than 1 s) into the hot oxidant flow. The temperature and velocity of the oxidant flow vary in the range of 600–1200 K and 0.5–5 m/s, respectively. These ranges are typical for power plants in the large- and small-scale energy industry. The paper specifies the minimum oxidant temperatures which are sufficient for sustainable ignition, as well as the ignition delay times, the times for complete burnout of CWSP droplets (radii of 0.5–2 mm), and the maximum temperatures in the fuel combustion area. We discuss how the oxidant temperature and the component composition of CWSP influence the parameters l...

The ignition parameters of the coal-water slurry droplets at the different methods of injection into the hot oxidant flow

Two different experimental approaches were realized for investigations of integral characteristics of single droplet ignition of coal-water slurry containing petrochemicals (CWSP) inside the hot flow of the gas oxidant. At first, the droplet was fixed inside the flow by special holder and the second way is free injection of the soaring droplet into the volume of combustion chamber. Research reports an experimental estimation of influence of material holder on ignition characteristics for typical CWSP. This is important, since many researchers use various holders (the ceramic rod, thermocouple junction, metal wire) when inserting droplets of coal-water slurry (CWS) and CWSP into the combustion chamber. There were three types of the droplet holders: the junction of the high-speed thermocouple, metallic wire and the ceramic rod. The basic components of the CWSP were filter-cake (the coal processing waste), the used turbine oil, the plasticizer (wetting agent) and water. Initial droplet radius was 0.5–1mm, and the temperature and the oxidant flow velocity were 400–1000K and 0.5–5m/s correspondingly. The ignition delays and the combustion times for the fuel droplets together with minimal temperatures of the stable ignition (with further combustion) were defined. Comparison of parameters of the flying droplet ignition with corresponding values for droplets that were fixed by holder was done. Soaring droplets have smaller ignition delay times (for 7–25%) relative to the case of droplet fixed inside the oxidant flow by holder (when the all rest parameters are similar). Influence of the holder material onto the values of times of ignition delay and combustion become essentially weaker with oxidant temperature growth. The obtained numerical results show the limitations and advances of the two approaches for laboratory investigations of the CWSP ignition and combustion.

Simultaneous ignition of several droplets of coal–water slurry containing petrochemicals in oxidizer flow

This paper examines ignition features of coal–water slurry containing petrochemicals (CWSP). Fuel slurry composition is based on a filter cake (typical processing waste) of coal (grade K), water, scavenged turbine oil, and plasticizer. The novelty of this paper is that it indicates a joint influence of several droplets on the CWSP ignition characteristics in an oxidizer flow (air). Its temperature and velocity vary in the range of 400–1200K and 0.5–5m/s. These ranges are chosen so as to yield optimal results that can be used in various fuel technologies and waste recycling. The study examines the cases of two, three, four, and five droplets. It is considered that droplets are arranged differently relative to each other (in parallel, in series, and in rhomb) in the oxidizer flow. The distances between droplets are also different; here, they vary from 0.5mm to 1.5mm. The diameter of each droplet is about 1mm. The study specifies the ignition delay time for CWSP. Special facilities, such as high-speed cameras, cross-correlation systems, a hollow glass cylinder (representing a combustion chamber), are used to monitor the basic parameters of ignition. Tema Automotive and Actual Flow software allow processing of the experimental results. Experiments demonstrate that the local sources of heterogeneous combustion are formed when CWSP droplets are burning. Such formation is characterized by some features, since droplets are spaced differently in the group relative to the oxidizer flow. Finally, the paper discusses the joint influence of neighboring droplets on the conditions and characteristics of their sustainable combustion.

Ignition of promising coal-water slurry containing petrochemicals: Analysis of key aspects

An experimental study of the macroscopic laws of the ignition of coal-water slurry containing petrochemicals (CWSPs) based on coal and flammable liquids processing waste is presented. Investigations have been performed to determine the prospects for burning such fuel mixtures prepared from raw materials in power plants at temperatures ranging from minimal (700–800K) to high (not <1000K). Oxidizer flow velocities varied between 0.5 and 5m/s. The study specifies the main stages of the processes at different heating rates and heat flows through a fuel surface element (a droplet or a particle). Investigations have been conducted on a single droplet (radius from 0.25mm to 1.5mm) of a specified fuel composition (we have considered over 20 different compositions). With the use of cross-correlation and high-speed video cameras coupled with software applications Tema Automotive, Actual Flow, we have examined the interactions of oxidizer flow with a fuel droplet surface. The ignition delay time and durations up to complete combustion of CWSP droplets have been measured. The experimental results allowed us to elaborate the heat and mass transfer mathematical model including phase transitions and chemical reactions in the main stages of the processes under study, which are: the inert heating up of the sample, the evaporation of moisture from a superficial layer (water and flammable liquid), the thermal decomposition of coal in the superficial layer of a droplet, the mixing of volatiles with an oxidizer, the combustion initiation of the emerging gas mixture, the heating up of coke, and its heterogeneous ignition. From the mathematical model and experimental data, we have defined the necessary and sufficient conditions for the ignition of CWSP.

Burning Properties of Slurry Based on Coal and Oil Processing Waste

The main physicochemical coefficients of the components and of the tested coal–water slurry containing petrochemicals (CWSP) have been collected. The viscosity, mixture stability, density, ash content, humidity, flash and ignition temperatures, and enthalpy of combustion of the tested CWSP are reported. The temperatures of combustion of fuel compositions with different concentrations of solid and liquid components have been measured, as well as the important parameters: the ignition time delays of droplets (radius 0.25–2.5 mm) and the times required to reach their complete burning. The study allows determination of the optimal fuel compositions yielding the shortest ignition time delays, the longest times to complete burning, the highest temperatures of combustion, and the maximum enthalpy of combustion. It is found that the viscosity of CWSP is dependent almost proportionally on the moisture content of components. It is shown that the calorific value of CWSP is dependent proportionally on the calorific v...