[PDF] Offdesign Operation Of Kraft Recovery Boiler eBook

Author : Peter Lars Versteeg
Publisher :
Page : 174 pages
File Size : 26,85 MB
Release : 2007
Category :
ISBN : 9780494400692

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Operating data from three recovery boilers was collected and analyzed using Principal Component Analysis (PCA) and Partial Least Squares Analysis (PLS). Variability in the operating data due to deposit accumulation on heat transfer surfaces, commonly called fouling, was visualized using PCA. This allowed a high-level comparison between operational periods of high fouling and low fouling in all boilers. This also serves as a proof-of-concept for the monitoring of recovery boiler fouling. PLS was used to extract the correlation structures between model input and output variables unique to each recovery boiler. The correlation structures showed that some variables were disproportionably associated with fouling. This suggests that controlled changes in these variables could improve operation. Together, these two techniques represent a major step forward in identifying operating variables that may be adjusted to minimize fouling in recovery boilers, and in developing an on-line fouling monitoring technology.

Author : Asghar Khalaj-Zadeh
Publisher :
Page : 426 pages
File Size : 29,33 MB
Release : 2008
Category :
ISBN : 9780494580219

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Carryover particles are partially/completely burned black liquor particles entrained in the flue gas in kraft recovery boilers. Understanding how carryover particles form and deposit on heat transfer tube surfaces is critically important in the design and operation of a recovery boiler. The tendency for a carryover particle to deposit on a tube surface depends on the particle temperature and composition at the moment of impact. This study was the first to examine systematically how carryover particle composition changes with the black liquor chemistry and burning conditions.A dynamic model was also developed to predict the composition of carryover particles as a function of black liquor composition and burning conditions. Based on the data obtained experimentally in this study, the kinetic equations for the oxidation of sulphide available in the literature were modified and incorporated into the model to improve its sulphide and sulphate predictions. The model predicts the main components of carryover particles formed in both the EFR and three operating recovery boilers reasonably well, except for the K content, which is slightly over-predicted at high O2 concentrations (or high particle temperatures).Based on the predicted composition, it is possible to determine the thermal properties of carryover and to assess its fouling propensity in the boiler. The information helps boiler manufacturers and operators to identify locations in the boiler where massive carryover deposition may occur and to devise appropriate control strategies to minimize fouling and to improve boiler thermal efficiency.The effect of black liquor composition and particle size, gas composition (O2 and SO2 concentrations) and temperature on the composition of carryover particles were studied using an Entrained Flow Reactor (EFR). Field studies were conducted on three operating boilers, where an air-cooled probe was used to collect carryover samples at the superheater entrance.The results show that the chloride (Cl) and potassium (K) contents in carryover particles were linearly proportional to their contents in black liquor. Cl and K were depleted during black liquor combustion due mainly to the vaporization of NaCl and KCl. The depletion of Cl is about three times greater than that of K. The significant depletion of Cl implies that carryover particles contain much less Cl, and hence, are less sticky than previously expected from black liquor composition.

Author : Terry N. Adams
Publisher :
Page : 0 pages
File Size : 29,2 MB
Release : 1997
Category : Boilers
ISBN : 9780962598593

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The 2005 Edition of the National Design Specification for Wood Construction was approved as an American National Standard on January 6, 2005. The 2005 NDS was developed as a dual format specification incorporating design provisions for both allowable stress design (ASD) and load and resistance factor design (LRFD). The NDS is adopted in all model building codes in the U.S. and is used to design wood structures worldwide.

Author : Honghi Tran
Publisher :
Page : 0 pages
File Size : 19,28 MB
Release : 2019-12-27
Category :
ISBN : 9781595102935

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Practical application and research on Kraft recovery boilers.

Author : Babak Emami
Publisher :
Page : 0 pages
File Size : 30,41 MB
Release : 2009
Category :
ISBN : 9780494609460

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The fouling of heat transfer surfaces in kraft recovery boilers is a significant concern for the pulp and paper industry. The usual approach to controlling fouling is the use of so-called "sootblowers," that utilize boiler steam to generate supersonic steam jets that are literally used to knock deposits off of the boiler tubes. About 3 to 10% of the total steam produced in a recovery boiler is used for sootblowing. This high energy cost demands that they be operated as efficiently as possible. It is thus essential to devise improved strategies for maximizing sootblower efficiency and minimizing steam consumption. To achieve this, the behaviour of sootblower jets, and the effects of various parameters on sootblowing, must be well understood. This thesis documents a study of the performance of sootblower jets using numerical simulation; CFDLib 3.02, a CFD code from the Los Alamos National Laboratory, was used for the simulations. This work had two main parts. In the first part, sootblower jets that perform at the design condition (fully-expanded jets) were studied; in the second part, the study was extended to off-design (under/over-expanded) sootblower jets. In the second part, the study was extended to sootblower jets not operating at the design condition. The compressibility-corrected code failed to properly simulate these under-over/expanded supersonic jets. A wide series of tests was carried out to determine that the problem was due to the turbulence model. The model was then modified to account for turbulence/shock wave interaction, by adding corrections to take into account shock unsteadiness and a realizability constraint. The new model yielded good agreement with some available measurements. The new model was then used to successfully predict some actual sootblower measurements, and to study the interaction of a sootblower jet with geometries similar to tube banks in recovery boilers. A parametric study was carried out to examine the effect of the offset between a sootblower jet and a tube bank, and of deposit size on a sootblower jet. The results indicate that the shock cell structure of a jet is only slightly affected by the offset, but that the size of a deposit strongly affects the pressure exerted by the impinging sootblower jet, which depends both on the jet shock cell structure, and on the location where the interaction occurs. In the first part, a compressibility-corrected version of CFDLib was validated against a wide range of available experimental data, of subsonic and fully-expanded supersonic free and impinging jets; simulations successfully predicted all of the cases. This compressibility-corrected model was then deemed suitable for modeling the fluid mechanics of fully-expanded sootblower jets, and so was used to study the effects of two parameters on sootblower jets: the lance pressure, and the rate of rotation of a sootblower. To study the effect of the lance pressure, numerical simulation was used to model fully-expanded sootblower jets corresponding to a range of lance pressures. To study the effect of rotation, the equations of motion were modified by adding the Coriolis and centrifugal terms, so that computations could be performed in a rotating frame of reference. Simulations were then run to study a fully-expanded sootblower jet operating at different rotation rates. The results indicate that sootblowers operate more efficiently at lower lance pressures, and that the rate of rotation does not significantly affect the structure of a sootblower jet.

Author :
Publisher :
Page : 14 pages
File Size : 35,39 MB
Release : 1999
Category :
ISBN :

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The temperatures of floor tubes in a slope-floored black liquor recovery boiler were measured using an array of thermocouples located on the tube crowns. It was found that sudden, short duration temperature increases occurred with a frequency that increased with distance from the spout wall. To determine if the temperature pulses were associated with material falling from the convective section of the boiler, the pattern of sootblower operation was recorded and compared with the pattern of temperature pulses. During the period from September, 1998, through February, 1999, it was found that more than 2/3 of the temperature pulses occurred during the time when one of the fast eight sootblowers, which are directed at the back of the screen tubes and the leading edge of the first superheater bank, was operating.