Sulphate Pulp Mill Research Articles

A filter method for the active and passive monitoring of sulfur dioxide in workplace air.

A method where sulfur dioxide is collected on impregnated filters (glycerol/potassium hydroxide solution) is described. Sampling can be done either with a pump or by the use of two different passive monitors available on the market. Analysis is made by ion chromatography. The methods have been evaluated and compared with a colorimetric air monitoring badge system (ProTek). Laboratory tests show that the accuracy of the filter methods is acceptable and that samples can be stored. Water vapor does not interfere, but hydrogen sulfide causes a minor decrease in recovery. ProTek has high accuracy but storage tends to decrease the recovery. Field tests in a steel rolling mill and a sulfate pulp mill showed a fairly good correspondence between the methods.

Direct determination of trace amounts of chlorophenols in fresh water, waste water and sea water

Chlorophenols were acetylated and the derivatives extracted by the simultaneous addition of acetic anhydride and hexane directly to the water sample. The extracts were then analysed by glass capillary column gas chromatography with electron-capture detection. Determination of chlorinated phenols at μg/1 concentration levels requires only 5 ml of sample. At ng/1 levels a 100-ml sample is sufficient. The total time of analysis is 18 min per sample. A comparison between pentafluorobenzoylation and acetylation showed that the acetylated derivatives of chlorophenol isomers separated better on the column. The method has been applied to drinking water, sea water and waste water from a sulphate pulp mill.

Computer Control of Sulphite Recovery Boiler and Evaporation Plant at Finnish Mill

Since 1976 fifteen computer control systems have been installed in recovery boilers of sulphate pulp mills in Finland. An extensive development in this area has taken place and the merits of computerized recovery boiler control systems have been outlined numerous times. In spite of this the very first computer control of a sulphite recovery boiler was installed as late as in the first half of 1982, at the pulp mill of Rauma-Repola Oy. The mill is the biggest dissolving, fluff and speciality pulps producer in Finland. The liquor of this process is burned in a Tampella type recovery boiler, which has a capacity of 1 050 mt dry solids per day. In spite of careful selection of material unexpected corrosion has existed on certain surfaces of the boiler. The running conditions and corrosion mechanism have been examined therefore effectively.During years the operating conditions have been developed to a direction where corrosion rate has been decreased remarkably. The reason for corrosion is the special sulphite liquor. These factors and especially the high sulphidity dictate more strictly the operating parameters in sulphite recovery boilers compared with the conditions in low sulphidity boilers.In this paper features of the control of this high sulphidity recovery boiler are discussed. Also the computer control system for this process is described. Finally the benefits of the control system are discussed.

Modelling and Optimization of Mud Filter and Lime Kiln

The possibilities to improve the operation of the lime cycle of a sulfate pulp mill through optimizing the controls of the mud filter and the lime kiln are discussed. By simulations, where real operational data is used, it is proved that there are great potentials to achieve considerable energy and chemical savings in the chemical recovery system. The problems and their solution methods are studied in three levels: viz. in 1) operational, 2) computational and 3) instrumental levels. Special attention is paid to modelling and optimization procedures, and a few new pragmatic methods are presented and proposed for future tests and real time use for ex. to optimize the set points and blowing interval of the mud filter. The studies show that in order to be able to optimize the operation of the calcining system, an adaptive control scheme is required. Some simple adaptive estimation and disturbance compensation methods are presented to fulfill the needs of real-time control. This is due to many kinds of process disturbances as well as variation in the filter performance between blowing intervals. In the end the applicability of the proposed methods is discussed in the light of mill experiences.

A new optical method for measuring suspended solids in pulp and paper mill effluents

A new optical method, the so-called TP-method, has been developed at the Swedish Forest Products Research Laboratory for measuring the amount of suspended solids. The great advantage of this method compared to other existing optical methods is that the result is independent of particle size. This is an important feature, since the characteristics of suspended solids from pulp and paper mills can vary significantly. The TP-method also provides a first order measure on the size distribution of the particles in the suspension. Furthermore, the TP-method is independent of the flow rate of the measuring medium and by compensation insensitive to variation in colour.The TP-method has been extensively tested in the laboratory and in mills with different kinds of production. The results show that the TP-method is well suited for quantitative measurement of suspended solids.Several years of experience with TP-instruments in different on-line positions is also very good. The instruments have shown to provide valuable and relevant information on both variations in concentration and variations in particle size distribution, with the result that it has been possible to indicate and to explain disturbances within the process - system. Several instruments have been used in an in-mill pollution control system, which was installed in a sulphate pulp mill in Sweden.

A New Optical Method for Measuring Suspended Solids in Pulp and Paper Mill Effluents

A new optical method, the so-called TP-method, has been developed at the Swedish Forest Products Research Laboratory for measuring the amount of suspended solids. The great advantage of this method compared to other existing optical methods is that the result is independent of particle size. This is an important feature, since the characteristics of suspended solids from pulp and paper mills can vary significantly. The TP-method also provides a first order measure on the size distribution of the particles in the suspension. Furthermore, the TP-method is independent of the flow rate of the measuring medium and by compensation insensitive to variation in colour.The TP-method has been extensively tested in the laboratory and in mills with different kinds of production. The results show that the TP-method is well suited for quantitative measurement of suspended solids.Several years of experience with TP-instruments in different on-line positions is also very good. The instruments have shown to provide valuable and relevant information on both variations in concentration and variations in particle size distribution, with the result that it has been possible to indicate and to explain disturbances within the process - system. Several instruments have been used in an in-mill pollution control system, which was installed in a sulphate pulp mill in Sweden.

An on-line production control system

Large sulphate pulp mills as the Skutskär mill are complex. They consist of many production departments with storage capacities between them. The effects of breakdowns and other disturbances in one department tend to propagate through the system and influence also other parts of the mill.The purpose of the computer based production control system described in this paper is to improve the coordinated operation of the different production departments and to reduce the negative effects of disturbances. This is primarily brought about by effective utilization of existing storage capacities.The production control system in the Skutskär mill uses a central process computer and an on-line information system. It includes an algorithm that calculates, on the basis of known restrictions, a plan with suggested production rates in the different departments during the planning period (1.5 days). The system allows manual modifications of a plan, in case modifications would turn out to be desired. The consequences of a plan are calculated, including the development in time of storage tank levels, production volumes and energy balances. Economic evaluations are also made based on the suggested plan. The plan and its consequences are presented on video screens using colour display.

An On-Line Production Control System

Large sulphate pulp mills as the Skutskär mill are complex. They consist of many production departments with storage capacities between them. The effects of breakdowns and other disturbances in one department tend to propagate through the system and influence also other parts of the mill.The purpose of the computer based production control system described in this paper is to improve the coordinated operation of the different production departments and to reduce the negative effects of disturbances. This is primarily brought about by effective utilization of existing storage capacities.The production control system in the Skutskär mill uses a central process computer and an on-line information system. It includes an algorithm that calculates, on the basis of known restrictions, a plan with suggested production rates in the different departments during the planning period (1.5 days). The system allows manual modifications of a plan, in case modifications would turn out to be desired. The consequences of a plan are calculated, including the development in time of storage tank levels, production volumes and energy balances. Economic evaluations are also made based on the suggested plan. The plan and its consequences are presented on video screens using colour display.

The premises for a computer based production control system of a sulphate pulp mill

The considerable benefits gained in recent years through computer control of pulp digesting and bleaching have encouraged the development of corresponding systems for the energy section and for the processes used in the chemical circulation in the pulp mill, namely the recovery furnace, the causticization plant and the lime kiln. This development has led to the need for development of higher level co-ordinating systems in order to assure the overall optimal operation of the mill. This paper deals with the newest process control systems and outlines the functions of the production control and management information system.

A Practical Approach to the Control of Recovery Boilers

The recovery boiler is an expensive and critical subprocess in the sulphate pulp mill and it will quite often cause a bottleneck in production. The burning process of black liquor is also quite sensitive to various disturbances (quality and analysis of BL). The recovery boiler has a dual function: on the one hand, to convert the used digesting chemicals to a reusable form, and on the other hand to utilize the heat produced by the burning process for steam generation as effectively as possible. The operation of a recovery boiler also has a substantial effect on environmental pollution. It is very understandable, then, that in the last few years much research and development work has been carried out in order to improve the control of the recovery boiler. It is also evident that digital computers can be used effectively to control recovery boilers: some systems are already in operation.This paper deals with the possible ways of tackling this problem. Some references are also made to experiences in Finland with a computer control system for recovery boilers developed in close cooperation with the user, the vendor and research workers and in continuous use at the Kaukopää Mill of the Enso-Gutzeit Company since winter 1976. The economical results achieved with this system will also be briefly presented.

Process for Clarifying Sulfate Pulp Waste Water

In a sulfate pulp mill, the waste liquors from alkali treatment in the bleaching of pulp and of the washing of unbleached pulp are highly colored and muddy, and these greatly affect the coloring of the waste water of the sulfate pulp mill.Clarifying the waste water of the mill by decoloring these waste liquors with iron or aluminium scrap under special treatment was studied .The process is as follows : Iron or aluminium scrap is dipped into chlorine waste liquor of bleaching treatment while aerating, thus metallic ion is dissolved into the liquor .The liquor is added to the colored water containing alkali waste liquor of the bleaching treatment and waste liquor of washing of unbleached pulp in suitable quantity, and mixed together to produce ferric or aluminium hydroxide, whereby the organic colloidal substance contained in the colored liquor is absorbed, bringing about cohesion and then precipitated together.In this process where is used iron scrap, chlorine waste liquor is to be fed with flue gas to strengthen the acidity, and when mixed with the colored waste liquor slaked lime is added.The clarifyiug results by these processesareasfollows : Color degree of the treated liquid…r/3-r/7 of the original liquid (mixture of colored waste liquor and chlorine waste liquor).B.O.D.of treated liquid…reduced by about 70% compared with the original liquid.Sulfide and metallic content in treated liquid…practically undetectable.

THE PREPARATION OF FIBERBOARD WITH SEVERAL WASTE WOODS

In our country, wood, one of the most important raw and construction materials, is rapidly getting scarce.From the rational utilization of wood, authors have been carried out this study in order to find whether the rejects in paper mills are suitable as raw material for fiberboard or not.In this report, the rejects in sulfate pulp mill were used as sample material.1. Preparation of stock. The rejects (so called knots) were disintegrated with Unimax-Refiner (a kind of vertical type refiner), the stock resulted had following characteristics.freeness (S.R.) 13.5alcohol-benzol extracts 0.9%Lignin (72%H2SO4) 24.8%2. Sheet formation and hot-pressing. The wet fiber sheets were prepared using the laboratory forming box from the suspension of its pulp. Thus obtained wet sheets were pressed holding between wire-gauze and stainless steel plate under next same pressing condition, as the temperature 140°C. the pressure 30 Kg/Cm2 and time 20minutes.In this experiment, rice straw defibrated after cooking with water, as raw material, was used solely or as blended to above reject.3. QualityQualities of thus obtained hardboard were tested depending upon the specification of JIS-A-5903, the figures measured were as following table. From the above table, it will be known that the characteristics of hardboard prepared with sulfate pulp reject (knot) are the impact strength very high and the flexibility is relatively large in comparing with the density of those boards owing to the partial delignification by cooking process.

Preventing Corrosion in the Sulfate Pulp Mill

Preventing Corrosion in the Sulfate Pulp Mill