Liquor Spray Research Articles

Kraft recovery boiler operation with splash plate and/or beer can nozzles — a case study

In this work, we study a boiler experiencing upper furnace plugging and availability issues. To improve the situation and increase boiler availability, the liquor spray system was tuned/modified by testing different combinations of splash plate and beer can nozzles. While beer cans are typically used in smaller furnaces, in this work, we considered a furnace with a large floor area for the study. The tested cases included: 1) all splash plate nozzles (original operation), 2) all beer can nozzles, and 3) splash plate nozzles on front and back wall and beer cans nozzles on side walls. We found that operating according to Case 3 resulted in improved overall boiler operation as compared to the original condition of using splash plates only. Additionally, we carried out computational fluid dynamics (CFD) modeling of the three liquor spray cases to better understand the furnace behavior in detail for the tested cases. Model predictions show details of furnace combustion characteristics such as temperature, turbulence, gas flow pattern, carryover, and char bed behavior. Simulation using only the beer can nozzles resulted in a clear reduction of carryover. However, at the same time, the predicted lower furnace temperatures close to the char bed were in some locations very low, indicating unstable bed burning. Compared to the first two cases, the model predictions using a mixed setup of splash plate and beer can nozzles showed lower carryover, but without the excessive lowering of gas temperatures close to the char bed.

Use of Waste Plastics in Coke Oven: A Review

To help in building a recycling-oriented sustainable society, Nippon Steel & Sumitomo Metal Corporation developed a waste plastic-recycling process using coke oven and put it into commercial operation in 2000. Now roughly 200,000 tons per year of waste plastics are processed in coke oven in Japan. In this process, the waste plastics collected from households are agglomerated to the sizes ranging from 20 to 30 mm in diameter and charged into coke ovens with coal at the blending ratio of about 1 mass%. Waste plastics are thermally decomposed into approximately 20 mass% coke, 40 mass% hydrocarbon oil (tar and light oil) and 40 mass% coke oven gas, which are utilized as iron ore-reducing agents in blast furnaces, raw materials for the chemical industry, and a fuel for power plants, respectively. Moreover, 92 mass% of the chlorine in waste plastics is released and absorbed by the ammonia liquor spray for cooling hot coke oven gas and converted to ammonium chloride. The waste plastic-recycling process using coke ovens is superior in that a large amount of waste plastics can be treated, useful materials can be recovered using the existing facilities, coke quality can be kept the same and the chlorine released from waste plastics can be fixed in the existing ammonia liquor spray system.

Behavior of chlorine during co-carbonization of coal and chloride compounds in cokemaking process

The behavior of chlorine during co-carbonization of coal and chloride compounds such as PVC in cokemaking process both on a laboratory scale and commercial scale was investigated. On a laboratory scale test, the chlorine residue ratio in coke derived from PVC was only 0.04%, which was much lower than that derived from the coal tested (35.1%) and NaCl (52.9%). The chlorine residue ratio derived from PVC reached near zero at about 400°C and it decreased at lower temperature range than that derived from MgCl2, NaCl and CaCl2. CaO addition helped the chloride derived from coal, PVC and NaCl to be fixed in coke. In the commercial scale coke oven, the addition of PVC to coal hardly affected the chlorine content in coke and COG. Most of the released chlorine was absorbed by the ammonia liquor spray for cooling hot COG. The chlorine in PVC was distributed to the coke, the ammonia liquor and the COG by 7%, 92% and 1% respectively, while the chlorine in coal was distributed by 43%, 56% and 1% respectively. The chlorine residue ratio in coke derived from PVC was much lower than that derived from coal since the decomposition of PVC added to coal was much faster than the release of chlorine from coal during carbonization.

Effects of flashing on spray characteristics of splashplate nozzles

The effects of flashing on black liquor spray patterns were investigated by analyzing numerous spray images obtained from laboratory experiments using small scale splashplate nozzles with water and experiments using actual size splashplate nozzles with black liquor. The results showed that flashing produces small droplets and increases droplet velocity. The liquor mass flow rate varies with direction: the rate is higher at the center than at the sides of the spray sheet, particularly at a lower excess temperature. At a higher excess temperature, however, the mass distribution becomes more uniform across the spray sheet. Criteria were developed for predicting the onset of flashing and for estimating the mean droplet size of the black liquor spray under flashing conditions.

CFD-modeling for more precise operation of the kraft recovery boiler

During kraft recovery boiler operation, situations can be encountered where the furnace temperature is asymmetric when comparing one side of the furnace to the other (i.e., left vs. right). In this paper, computational fluid dynamics (CFD) modeling is applied to study furnace load and liquor spraying as causes for asymmetric furnace temperatures in a 4450 tons dry solids (TDS)/day kraft recovery boiler. The model predictions are compared against validation measurements. Decrease in furnace load is identified as the main cause of the temperature asymmetry. The simulations also suggest that, at decreased load, relatively small differences in the tilts of individual liquor sprays can increase the temperature asymmetry.

The Significance of Celocity in Black Liquor Spraying

The characteristics of black liquor sprays can be estimated using flashing maps that present the velocity of the spray at different spraying temperatures as a function of mass flux. Dimensionless velocity describes well the flashing intensity of the flow and is the key factor in estimating the effect of minor changes in spraying tem-perature or mass flux. The flashing maps give valuable initial data useful for boiler modeling purposes and boiler operations.

Characteristics of black liquor sprays from gas-assisted atomizers in high-temperature environments

Black liquor droplets in an entrained-flow gasifier that are too large or too small can cause problems in the chemical recovery process. It is therefore important in gasifier design to understand the nature of the atomized gas spray. We used high-speed imaging to study black liquor sprays in cold and hot environments. Significant conclusions are that: 1. the droplet size distribution width is linked to the mean droplet size as for other sprays in the literature, necessitating a gasifier design that is tolerant of the distribution width associated with the target droplet size; 2. the shape of black liquor droplets is highly non-spherical, necessitating consideration of shape in addition to mass; 3. black liquor has exceptional ability to attach to the nozzle and thereby to form larger-than-desired fragments of liquor; and 4. the furnace environment has a measurable impact on droplet formation, making cold-spray-chamber test results difficult to apply to practical in-furnace spray performance. It had previously been assumed that the furnace environment does not affect the spray.

Furnace endoscope?measuring fuel spray properties in hot and corrosive environments

A furnace endoscope was developed to carry out in-furnace measurements of black liquor sprays in order to discover the initial velocity, opening angle and trajectory of the spray, and compare spray disintegration mechanisms and spray appearance with the ones measured in a spray chamber. An error analysis of the velocity measurement method was carried out, and the meaning of the optimum measurement distance from the optics to the observed object is discussed. Some details of the development process of the probe are also presented, especially the definition of the scale of the image and the cooling system of the protection tubes. The furnace endoscope can be used in difficult conditions, such as those found inside a chemical recovery boiler (~1,200°C and corrosive chemicals) with promising and accurate measurement results. The equipment has been tested in several furnaces.

Black Liquor Sheet Breakup Mechanisms and the Effect on Drop Size

Black liquor is a spent liquor of the pulp and paper industry. It is burned in kraft recovery boilers for chemical and energy recovery. The high dry solids content and viscosity of black liquor require a high spraying temperature this high spraying temperature changes the performance of the boiler. Kraft recovery boiler deposit formation, emissions and chemical recovery are strongly affected by the drop size, size distribution and velocity of the black liquor spray formed by a splashplate nozzle. Black liquor droplet formation of a splashplate nozzle is the subject of this study. The sheet breakup mechanism was studied with a system based on a video and image-analysis. The drop size of mill-scale nozzles was also measured with an image-analysis-system. Measurements were carried out in a test chamber. The sheet breakup mechanism and drop size tests were carried out both below and over the boiling point of black liquor. Special attention was paid to the effect of flashing on drop formation. Temperature increase normally decreases drop size. In the case when the wavy-sheet disintegration changes to perforated-sheet disintegration, the drop size increases. Spray velocity rises when the temperature is increased above the boiling point.

DROP SIZE MODIFICATION IN BLACK LIQUOR SPRAYS FROM COMMERCIAL NOZZLES USING PULSED FLOW

Improved operation of kraft recovery boilers is expected to result from knowing how to obtain a controlled, well-defined droplet size distribution issuing from the black liquor spray nozzle. Black liquor drop size data were obtained from an environmentally acceptable spray facility capable of delivering liquor at normal firing temperatures using commercial nozzles. Image analysis techniques were developed from high-speed video images which gave good two-dimensional representations of black liquor sprays. Previous work showed that black liquor sprays have a characteristic size distribution which is determined by the fluid mechanical forces breaking up the liquid sheet issuing from the nozzle. This work has centered on applying flow pulsation as an independently controlled force on the sheet breakup process in an attempt to change the drop size distribution. Experiments are described which feature controlled frequency flow pulsations. Results are presented which show the dependence of median drop size on pulsation frequencies up to 450 Hz.

Influence of Stubble Treatment and Autumn Application of Nitrogen to Stubbles on the subsequent Incidence of Take‐all and Eyespot

SUMMARYCommercial‐scale field trials on farms in North Hampshire over four seasons (1963 to 1968) showed that nitrogen applied to wheat or barley stubble after harvest in the autumn failed to reduce the incidence of take‐all and eyespot in the succeeding wheat or barley crop, or produced only minor reductions in the spring which were not maintained up to the stage of crop maturity. There were no consistent significant differences in levels of disease between rate or form of nitrogen applied as urea/ammonium nitrate spray at 0, 12, 24 or 48 units/acre (1 unit/ac × 1·25 kg/ha), ammoniacal gas liquor spray at 48 units/acre and anhydrous ammonia injected at 40 units/acre. Burning‐off stubbles with high‐output flame cultivators did not significantly reduce the incidence of either disease.