Search

89APR177

MD microstriations in paper: a two-sided shrinkage phenomenon?, TAPPI JOURNAL April 1989

An analytical approach to assess the interrelation of surface properties and softness of tissue paper, TAPPI Journal February 2023

An analytical method to quantitatively determine the amount of polyamide epichlorohydrin (PAE) in paperboard and white water, TAPPI Journal February 2023

Editorial: Nonwovens sector provides opportunities for professional and advanced textiles growth, TAPPI Journal February 2023

Mechanistic aspects of nanocellulose–cationic starch–colloidal silica systems for papermaking, TAPPI Journal February 2023

Recycling performance of softwood and hardwood unbleached kraft pulps for packaging papers, TAPPI Journal February 2023

Setting priorities in CNF particle size measurement: What is needed vs. what is feasible, TAPPI Journal February 2023

Non-process elements in the lime cycle: New findings regarding NPE distribution and lime mud filterability, TAPPI Journal July 2026

ABSTRACT: Proper functioning of the recausticizing cycle is crucial for securing a stable white liquor supply for a pulp mill. Common runnability problems in the modern lime cycle, such as low filterability and poor dewatering of lime mud, high dead load, or ring formation in the lime kiln, are often caused by accumulation of non-process elements (NPEs). This project attempted to verify the traditional rules of thumb regarding the chemical behavior of NPEs: magnesium (Mg), aluminum (Al), silicon (Si), phosphorus (P), zinc (Zn), manganese (Mn), iron (Fe), copper (Cu), barium (Ba), cadmium (Cd), and lead (Pb) in the causticizing reaction, and to investigate the reasons behind poor lime mud filterability. First, a standardized method for measuring filterability of lime mud was developed. Next, a series of recausticizing experiments, followed by immediate filtration trials, was conducted using mill green liquors, laboratory-made synthetic green liquor, reburned lime/makeup mix, and extra NPE additions. It was found that sodium (Na), potassium (K), and sulfur (S) followed the liquid phase, as expected, while Mg, P, and Ba, but also Pb, Cu, and Cd, showed low solubility and accumulated in the lime mud. The Si and Al accumulated in the lime mud even though the soluble content in liquor was high, while the behavior of Mn, Fe, and Zn was more complex. Based on these results, tentative solubility limits for NPEs were suggested as a first estimate for the maximum possible concentrations of NPEs in mill white liquor. The causticization-filtration experiments revealed that overliming and high content of Mg in green liquor clearly led to lower filterability, but our addition of Si did not have such an effect. As differences in particle size and size distribution have a certain impact on the filtration resistance, the lime mud sedimentation behavior, combined with other characterization methods, might be used as an indication for the filterability. Finally, a list of recommendations for pulp mills was formulated that starts with establishing a comprehensive standard for a lime mud with good filterability. This standard can be used as a benchmark for comparison any time a lime cycle runnability problem is identified.

Controlling sulfidity by recycling sulfur in CNCG, TAPPI Journal July 2026

ABSTRACT: Pulp and paper mills have faced a major dilemma. On one hand, mills should not dispose of the side streams by mixing them with effluent water. On the other hand, there has been no other way to dispose of excess sulfur than getting rid of recovery boiler electrostatic precipitator (ESP) ash and buying sodium hydroxide to replace lost sodium. A new, yet old, process has been introduced to alleviate the problem. An alternative is the onsite production of sulfuric acid (H2SO4) to significantly reduce, or to even eliminate, the need for recovery boiler fly ash dumping. A sulfuric acid plant produces concentrated commercial quality H2SO4 from concentrated non-condensable gases (CNCGs). Up to 99.9% of the sulfur in CNCGs can be converted into concentrated sulfuric acid with this wet-gas sulfuric acid (WSA) process. There are already references on pulp mills highlighting that the process is straightforward to use. Mills can increase the amount of sulfur in CNCGs by controlling the heavy back liquor storage time and temperature. This opens up a new way to control the mill sulfidity by recycling sulfur. The effect of recycling sulfur is highlighted with reference mills. Due to integrated paper production, the Northern Mill is a large energy consumer, producing mostly softwood-based end products. The Eucalyptus Mill is a large standalone hardwood (eucalyptus) pulp mill where electricity is produced substantially in excess of its own use. As a sample case, lignin production with and without sulfur recycling is presented.

Black liquor spray properties in-furnace conditions for swirl cone nozzles TAPPI Journal July 2026

ABSTRACT: Recovery boiler furnace operation is controlled for high chemical recovery, high steam production, and low emissions. Good control allows long runs with minimum cleaning without expensive shutdowns. An essential variable affecting boiler operation is black liquor spraying into the furnace. Poorly controlled black liquor spraying causes difficulties, e.g., in chemical recovery, fouling of heat transfer surfaces, and decreased energy production. A challenging measurement strategy with three different swirl cone nozzles . types A, C, and T . was carried out at a mill in the United States. Black liquor spray properties were measured under in-furnace conditions for flow rates of 2.0 L/s to 3.0 L/s. Three spraying temperatures of 119™‹C, 122™‹C, and 126™‹C, which were 2™‹C, 5™‹C, and 9™‹C above the boiling point (ÄTe), were tested. These flow rates and temperatures are typical for industrial nozzle sizes with exit orifice sizes of 17 mm and 22 mm. An imaging method to measure droplet size in a highly challenging furnace environment was developed. Droplet volume median diameter (Dv50) for nozzles A, C, and T varied between 7 mm to 4 mm, 7 mm to 5 mm, and 8 mm to 6 mm, depending on the flow rate and temperature. The high number of droplets detected by the analysis program enabled data fitting into statistical correlations. The size and width parameters for the Rosin™] Rammer droplet size distribution function could be defined. The droplet size distribution was found to be surprisingly wide, probably because of swollen droplets. Spray velocity was measured in two locations, 5 cm from the nozzle and 1.8 m from the nozzle. Near the nozzle, the average velocity increased from 7.3 m/s to 13 m/s when the flow rate was increased from 2 L/s to 3 L/s. Increase of black liquor temperature increased spray velocity in most of the cases. At the distance of 1.8 m from the nozzle, average spray velocities varied between 4.0 m/s to 11 m/s, depending on nozzle geometry, flow rate, and temperature. The opening angles of the spray for nozzles A and C varied between 57™‹ to 78™‹. The opening angle of nozzle T with flow guide varied between 48™‹ to 56™‹. The highest penetration of the spray was estimated for nozzle T because of the narrow spray and large droplets.