Continuous Cooking Research Articles

Parameter sensitivity of a wood chips flow model

AbstractA computational fluid dynamics (CFD) study of the parameter sensitivity of a wood chips model was performed on an industrial impregnation vessel, which is the first step in a continuous cooking system. The solid and liquid phases were both treated as continua and it was found that the continuum model for the solid wood chips phase could capture the previously observed oscillating formation of arches in the contracting part of the vessel, which will occur at different levels of volume fraction depending on the material constants. The parameters that were examined are the solid pressure, permeability, viscosity, and wall friction. It was found that all the parameters strongly affect the distribution of the wood chips in the vessel as well as the oscillation effects, hence also the flow field which is important to accurately predict in order to ensure optimal performance of the impregnation vessel. Thus, correct material data for these types of simulations are crucial to the outcome and should be chosen for the appropriate situation and bio‐material.

Development and performance analysis of continuous cooking systems

Development and performance analysis of continuous cooking systems

The effect of continuous cooking on the properties of spaghetti and its cooking water

AbstractBackground and ObjectivesIn catering environments, subsequent batches of pasta are cooked in the same water to save water and energy. This results in formation of a foam layer made up by solids leached from the pasta. Here, the effect of cooking up to 13 subsequent batches on spaghetti cooking and foaming of the cooking water was investigated. Cooking at acidic pH was also studied for a single batch.FindingsWater uptake by dry spaghetti decreases with batch number. The increasingly lower mobility in the network of swollen starch and polymerized protein network reduces the extent to which albumins and globulins are leached out. Evidently, the solid content in the cooking water increases with batch number while its pH drops. Separation of pasta fragments from the cooking water does not significantly affect (p > 0.05) the foam stability.Significance and NoveltyThis study provides additional insights in the composition and foaming properties during the continuous cooking process of pasta.

РАЗРАБОТКА ТЕХНОЛОГИИ ПРОПЕЧЕННЫХ ДИЕТИЧЕСКИХ ПАШТЕТОВ ИЗ ДАЛЬНЕВОСТОЧНЫХ РЫБ

Technology of baked diet pates from Far Eastern fishes was developed in the laboratories of the Institute of Food Production of the FSBEI HE "Dalrybvtuz". The purpose of the work was to develop the technology of dietary baked fish pates, providing an expansion of the assortment of finished products and rational use of secondary fish raw material of saffron cod and rudd. The new technology provides substituting vegetable oil by fish broths from secondary raw materials in the recipe for baked general-purpose fish pates made of saffron cod and rudd. Functional and technological properties of broths were studied depending on the duty of water (from 0.5 to 2.0) with a continuous cooking time of 60 minutes. The influence of the duty of water and the duration of broth cooking on their organoleptic properties was studied. It is established that the increase in duty of water from 0.5 to 1.0-1.5 is accompanied by a decrease in the content of dry matter in the broth, curves of kinematic viscosity and surface tension of broths have a similar dynamics, which indicates a direct-proportional relationship between the colloid properties of broths and the content in them of dry substances. It is shown that the duration of cooking has a priority over the duty of water effect on the organoleptic properties of fish broths. As a result of the research, the optimal technological parameters for the production of baked dietary pates were established: duty of water - 0.5 (for saffron cod) and 1.5 (for reddish); the broth cooking time is 60 minutes; temperature during cooking broth 100°C; mass fraction of broth in the formulation of the finished product 35%, vegetable oil 0%. In the course of study of the quality of pastes made using the developed technology it was stated that the calorie content of diet pates is lower than that of general pates by 57.2% for saffron cod and 64.9% for rudd; while maintaining a high level of organoleptic properties and relative biological value of finished products in relation to the basic version - general pates.

Box type solar cookers with sensible thermal energy storage medium: A comparative experimental investigation and thermodynamic analysis

Box type solar cookers with and without thermal energy storage are experimentally analysed within the scope of this research for characteristic continental climatic conditions of Bayburt, Turkey. For efficient and continuous cooking in such climates, thermal energy storage is required to be considered in solar cookers due to remarkable temperature differences between sunrise and sunset. Bayburt stone, a special natural stone with low density and notably high specific heat capacity, is utilised as a sensible thermal energy storage medium in a box type solar cooker, and thermal performance assessment of Bayburt stone cooker is compared with a conventional cooker without thermal energy storage through a comprehensive experimental research and thermodynamic analysis. For a typical late summer day, solar intensity, ambient temperature, absorber plate temperatures, internal air temperatures, internal and external glass temperatures, water temperatures, energy and exergy efficiencies are determined time-dependently for each solar cooker. The results clearly indicate that absorber plate temperature in conventional solar cooker has a notable decreasing tendency toward sunset, which totally affects the overall thermal performance of the system. On the contrary, Bayburt stone cooker enables an efficient, steady and continuous cooking till late evening owing to sensible thermal energy storage medium. In terms of thermodynamic performance figures, Bayburt stone cooker is observed to have considerably better energy and exergy efficiency. According to the results, energy efficiency of Bayburt stone cooker is determined to be in the range of 35.3–21.7% while it is found to be 27.6–16.9% for conventional solar cooker. On the other hand, exergy efficiency of Bayburt stone cooker is determined to be 21.2–14.1% whereas it is calculated to be 18.0–11.6% for conventional cooker. It can be concluded from the results that Bayburt stone as a thermal energy storage medium remarkably improves the thermal performance figures of box type solar cookers.

連続蒸解装置の発展の歴史とアンドリッツの最新技術

連続蒸解装置の発展の歴史とアンドリッツの最新技術

Design and development of energy efficient continuous cooking system

For large scale cooking, it is desirable to implement continuous cooking. In addition to the usual advantages of continuous cooking (size of cooker, uniform cooked quality, possibility of process control), there is a possibility of increasing the thermal efficiency by preheating water against the hot cooked food leaving the cooker. In the present work, solid and liquid phase residence time distribution (RTD) have been measured in 120mm diameter and 1.6m long continuous cooker. Three levels of screw speed (1, 3 and 5rpm), two levels of solid flow rate (12and 24kg/h) and three levels of liquid flow rate (15, 25 and 35 lph) were selected. The solid phase was always found to move in a plug flow manner as the minimum Peclet number was found to be 81.5. This information was found to be useful for deciding the capacity of the continuous cooker. Thus, the time required for batch cooking was found to be equal to the minimum residence time in a continuous cooker at equivalent operating condition of temperature.

A history of failed innovation: continuous cooking and the Soviet pulp industry, 1940s–1960s

In the years before and after the Second World War, chemical and related industries in a variety of countries experienced a surge in innovation and development. As a result, the pulp industry became a space for considerable innovation. In Sweden, Johan Richter developed the Kamyr digester, a pulp cooker that could run continuously and was adopted by industry within a decade. Prior to Richter, Soviet engineer Leonid Zherebov designed a similar cooker. But after 25 years of experiments, Zherebov’s design failed, and Soviet factories began to produce pulp using imported Kamyr digesters. This article examines the history of continuous pulp cooking in the Soviet Union as a means to understand the nature of Russian technological innovation and its failures. The paper contends that his effort failed because of the technological system developed by Soviet forestry – a system characterized by a lack of open communication among its main institutional actors and a scarcity of resources to facilitate innovation.

Integrated control of emission reductions, energy-saving, and cost-benefit using a multi-objective optimization technique in the pulp and paper industry.

Reduction of water pollutant emissions and energy consumption is regarded as a key environmental objective for the pulp and paper industry. The paper develops a bottom-up model called the Industrial Water Pollutant Control and Technology Policy (IWPCTP) based on an industrial technology simulation system and multiconstraint technological optimization. Five policy scenarios covering the business as usual (BAU) scenario, the structural adjustment (SA) scenario, the cleaner technology promotion (CT) scenario, the end-treatment of pollutants (EOP) scenario, and the coupling measures (CM) scenario have been set to describe future policy measures related to the development of the pulp and paper industry from 2010-2020. The outcome of this study indicates that the energy saving amount under the CT scenario is the largest, while that under the SA scenario is the smallest. Under the CT scenario, savings by 2020 include 70 kt/year of chemical oxygen demand (COD) emission reductions and savings of 7443 kt of standard coal, 539.7 ton/year of ammonia nitrogen (NH4-N) emission reductions, and savings of 7444 kt of standard coal. Taking emission reductions, energy savings, and cost-benefit into consideration, cleaner technologies like highly efficient pulp washing, dry and wet feedstock preparation, and horizontal continuous cooking, medium and high consistency pulping and wood dry feedstock preparation are recommended.

Digester thinning: Erosion-corrosion of internal flow channel headers

A softwood continuous digester has experienced severe erosion-corrosion of the shell wall inside the internal flow channel headers of the extraction and modified continuous cooking (MCC) zones. Although erosioncorrosion is a common form, it is not typically looked for inside digester flow channels. The worst damage was located where high velocity liquor exits the screen orifices and enters the collection headers. With erosion-corrosion rates as high as 200 m/year, the damage has effectively reduced the wall thickness almost by half in the worst areas. Also affected were the horizontal backing rings that form the bottom of the flow channels. An API-579/ASME FFS-1 Part 5, Level 2 analysis was performed to allow the mill to continue operating the digester until the next scheduled outage. Owner-users are encouraged to inspect these locations in their digesters to ensure that erosion-corrosion has not caused accelerated and/or unexpected shell thinning. The internal flow channels represent locations that are not readily accessible for internal visual inspection without removal of the flow channel header cover plates and removal of the residual black liquor typically retained in these flow channels. External, on-stream ultrasonic thickness testing (UT) at the proper collection header elevations has been determined to be an effective way to detect the presence of this erosion-corrosion phenomena. Also discussed are considerations to make on-stream UT as accurate as possible. Corrosion rates determined via electrochemical corrosion probe monitoring have correlated very well with the corrosion rates determined by on-stream UT data.

Hydrothermal Pretreatment of Hardwood Chips Prior to Alkaline Pulping and D0(EP)D1 Bleaching

In this study, mixed southern hardwood was pretreated via a hydrothermal process at 160 °C for 1 h. Alkaline pulping was then conducted on both the pretreated and original chips to prepare pulp with Kappa 17 and 30. For the Kappa 30 pulps, oxygen delignification was further carried out to render Kappa 17. After pulping, the different pulps with similar Kappa 17 were bleached by the D0(EP)D1 sequence. Pulping results show that the pretreated chips are easier to cook and necessitate less alkaline charge to achieve a similar Kappa without decreasing the pulp viscosity. Under similar bleaching conditions, hydrothermal pretreatment leads to pulps with a higher brightness, viscosity, and paper sheet opacity and scattering coefficient, while also lowering the burst and tensile strength. Furthermore, the pulp fiber length, fiber width, and percentage of fines decreases, yet the coarseness, curl index, and kink index increase. However, the paper properties of bleached pulps are not improved significantly when subjected to modified continuous cooking (MCC) pulping or oxygen delignification.

The Study of Kraft Continuous Cooking of Knenaf

The paper studied the possibility of using the whole stalk kenaf as a raw material for producing high yield and good quality bleachable pulp. The stem of kenaf has two distinct parts: the bast and the core. which have markedly different chemical components and fiber morphology. In general, the length of bast fiber ranges from about 2-2.5mm, while that of the core varies from about 0.5-0.8mm, so it is important to achieve a balance of the bast fiber and the core during pulping. The study indicated that using the selected continuous cooking conditions, the properties of kenaf pulp approached to the hardwood pulp and would be easily bleached.

Energy efficient control techniques in continuous cooking application

Abstract Energy efficiency is one of the main aspects in the Kraft pulping process. In Kraft pulping, the delignification of the pulp is mainly controlled by temperature and alkali. However, the quality is usually measured only in the blowline of the digester resulting in a control delay several hours. This affects to the quality control and also the energy efficiency of the plant. In this study, energy efficiency in the continuous Downflow Lo-Solids ® cooking application is studied using model-based approach. Temperature and alkali controls are considered and some suggestions are proposed.

Industrial Lo-Solids Pulp Digester Simulation by the Purdue Model

The Purdue model was adapted to simulate an industrial Lo-Solids pulp digester using ad-hoc reac-tion kinetics for Pinus radiata cultivated in Chile. Simulation results for blow line kappa number, pulp yield, free liquor temperature profile, and pulp production rate all agreed well with pulp mill data from Celulosa Arauco y Constitucion’s Arauco plant in Chile. Researchers then applied the mathematical model to simulate an increase in fil-trate flow to the modified continuous cooking zone to save white liquor consumption, keeping blow kappa number at its target value. Simulation results show a 9.1% savings of white liquor and a significant decrease in dissolved sol-ids content, thus improving the Lo-Solids pulping process.

FAULT TOLERANT CONTROL APPLICATION FOR CONTINUOUS KRAFT PULPING PROCESS

In this study, the fault tolerant Kappa number control in continuous cooking application is investigated. The Kappa number is one of the quality measures in the pulp cooking process and usually the only on-line measurement. It is a measure of the residual lignin content in the pulp. The Kappa number is mainly controlled by the cooking temperature. In this study, Kappa number control (temperature control) is carried out using Gustafson's Kappa number model for the prediction of the blowline Kappa number. New temperature set point is solved iteratively based on the difference between the predicted and target blow-line kappa numbers. The input variables are monitored using self-organizing map (SOM). The data is collected from industrial conventional continuous cooking digester. Good results were achieved using the proposed approach.

IDENTIFICATION OF RESIDENCE TIMES IN CONVENTIONAL CONTINUOUS KRAFT COOKING

Industrial kraft cooking process producing both softwood and hardwood pulp was studied. Residence times of chips in the conventional continuous digester were modelled based on volume fractions of chips. The volume fractions were modelled as a function of a real-time modelled cooking degree profile of chips in the digester. Control of continuous cooking process can be improved by the more accurate information about the residence times.

Ultrafiltration of kraft cooking liquors from a continuous cooking process

Two cooking liquors and a black liquor were fractionated by ultrafiltration. The liquors were withdrawn from different stages in a kraft pulp mill employing continuous digestion. The ultrafiltration was performed at 90°C with two ceramic membranes with cut-offs of 5 kDa and 15 kDa. Only small differences in membrane performance were observed when concentrating the three liquors to 90% volume reduction. The average flux was 55 l/m 2 h for the 5 kDa membrane and about 115 l/m 2 h for the 15 kDa membrane. The concentration of lignin was on average 230 and 155 g/L in the retentate from the 5 kDa and 15 kDa cut-off membranes. The ash content was reduced from 37–40 g/g total dry solids to 20–30 g/g after ultrafiltration.

PREDICTION AND CONTROL OF BLOW-LINE KAPPA NUMBER

Two industrial continuous cooking processes producing both softwood and hardwood pulp were studied. Real time kappa number profiles of conventional and Downflow Lo-Solids cooking were modelled. Gustafson's kappa number model with optimised parameters was used. Blow-line kappa numbers were successfully predicted before cooking zone. New kappa number control strategy is presented. In control strategy temperature set point is determined iteratively using prediction model of kappa number.

VISUALIZING YIELD PROFILES IN CONTINUOUS COOKING PROCESSES

In industrial continuous cooking systems, yields are seldom measured online. In this study, profiles for lignin, carbohydrates and total yield are constructed using physical model. The yield profiles are utilized for two kinds of digesters: conventional and Downflow Lo-Solids cooking processes. The total yield is also predicted using fuzzy clustering model.

DIAGNOSIS SYSTEM FOR CONTINUOUS COOKING PROCESS

Industrial systems generate a lot of information for operators. Increased measurement information flow might cause difficulties for the process operators to observe the process states and faulty process operation. In this study, measurements and statistical variables are combined by fuzzy logic to generate key factors for several points in the continuous cooking digester. The overall diagnosis system combines the key factors into one system which is used for the operational purposes and as a helping tool for process condition monitoring.