Evaporation Plant Research Articles

ＩＴＣの操業経験

Hokuetsu Niigata Mill started up recently its third coated paper machine (PM 8) with a capacity of 240, 000 tpy. For the purpose of not having to purchase as much market hardwood pulp for this machine and other upgraded machines, the increase of pulp production capacity and the modernization of the pulp plant were planned and carried out before the machine's start up.Many facilities such as a recovery boiler, a recausticizing plant including lime kiln, a bleach chemical preparation plant, a steam turbine and power generator, an evaporation plant, a wastewater treatment facility, a chip handling system and a fiber line have been installed one after another according to the three-year program which was completed by March 1998.This fiber line with 1, 200 tpd of hardwood bleached pulp is now running satisfactorily and achieved the expected results, meeting demands of quality and quantity for the paper machines of our four mills.This article describers operation experience of the ITC (Isothermal Continuous Cooking) digester system which has the state-of-the-art technology of extended delignification in the new fiber line.

Further evaporation and final treatment of process-water concentrates

The study is part of a longer-term effort aimed at developing a separate treatment process for evaporation-concentrates of paper-mill process waters. This article deals with research on the two key processing steps; namely, the further evaporation and the final treatment of the concentrates. In laboratory experiments, various feed waters, including several different TMP filtrates, were evaporated to high dry-solids contents. The condensates recovered in most experiments contained relatively small amounts of organic matter. The extent of vapourisation of organic acids, relative to water, increased somewhat with increase in dry-solids content. Two TMP concentrates from large-scale evaporation plants were further concentrated in a pilot-scale forced-circulation evaporator. Viscosity was the factor limiting the extent of concentration. Using an evaporation temperature of about 80°C, the maximum dry-solids contents achieved with the two different concentrates were about 45 wt% and about 60 wt%, respectively. Fouling of heat-transfer surfaces was observed with both concentrates. A techno-economic evaluation of final-treatment options for alkali-rich concentrates is under way. According to intermediate results, molten-phase combustion processes would not require support fuel once the dry-solids content of TMP concentrate exceeds about 50 wt%. The aim of future work is to optimise the overall treatment process.

Biosludge incineration in a recovery boiler

An activated sludge process is an effective tool against effluent emissions in a pulp mill. It has only a few features which can be regarded deficiences. One of them is that effluent treatment of a modern pulp mill creates some 10-20 tonnes dry solids of biosludge per day. This sludge is difficult to burn due to its high moisture content. The most common way is to mix biosludge with primary sludge, to dewater the mixture in presses and finally to burn it in a solid fuel boiler. This type of sludge treatment incurs rather high costs and does not produce any net energy. Also combustion emissions vary depending on the boiler type. The Metsa-Botnia Kemi Pulp Mill was the first mill in the world to burn biosludge in a recovery boiler. The system start-up was in 1993 and it has been in operation ever since. Mechanically dewatered biosludge is mixed with weak black liquor and concentrated in a conventional evaporation plant equipped with a pressurized superconcentrator unit. In a modern recovery boiler, firing conditions are well controlled and monitored. Better emission control than in most bark fired boilers is achieved. Accumulation of nonprocess elements, corrosion, plugging, scaling and some other operational problems were expected. A lot of experience has been gathered during the years of operation and reviewed in this presentation. The achieved benefits of the system are discussed. Disposal of biosludge in a recovery boiler offers an economically and environmentally attractive alternative. Probably the best evidence from this is the fact that Metsa-Botnia has applied the same process solution in the recent reconstruction of the recovery departments at the Jouteno Mill.

Experimental and theoretical study of an open multi-compartment absorption heat transformer for different steam temperatures. Part III: application to process industry

The technical and economic feasibility of incorporating an absorption heat transformer was investigated, to increase the energy efficiency of an evaporation–crystallization plant in a sugar mill, having an intake capacity of 17.5 kton of sugar beets per day. A new design of this transformer was developed to cope with the common situation prevailing in many process industries where there is both a need for different steam temperatures and access to waste vapours of various temperatures. Both the absorber and generator are partitioned in a number of compartments which depend on the number of high quality steams and waste vapours, respectively. The circulation of the working medium is quite low which causes a fairly high concentration change and thereby different temperatures in the compartments. The low circulation ratio eliminates the need of heat exchange between the generator and the absorber. Four main process configurations were simulated to establish optimal energy conservation strategies for the evaporation plant and to determine the optimum location and size of the transformer. The crystallization plant, which is supplied with vapour extracted from the evaporation plant, had to be incorporated in the calculations. The absorber and generator are provided with the waste vapour leaving the last evaporator and waste vapour streams leaving the crystallization plant, respectively. These vapours are normally discharged to a dump condenser. The results of these simulations revealed that the total amount of live steam used in the evaporation plant can be reduced by 11.8–16.4%, depending on the temperature level allowable in the crystallization plant. The payback period of this type of investment depends mainly on the equipment cost, local steam cost, and annual operation time.

Dynamic simulation of an absorption heat transformer incorporated with an evaporation plant

This study presents a simple lumped parameter model of an absorption heat transformer (AHT). The model is compared with operating data from a pilot-scale AHT unit incorporated with one of the sulphite-liquor evaporation plants at a major pulp and paper mill. The expected performance of a full size AHT incorporated in different ways to the evaporation plant is also discussed.

Industrial water production by utilization of a reverse osmosis and an evaporation plant

ITALIMPIANTI has realized the steel making plant in Woljsky (on 1989), situated in the Volgograd area between the Caspian Sea and the Black Sea, with a steel output of 150,000 t/y from scrap, 720,000 t/y of seamless pipes, and 210,000 t/y of blooms. In the ambit of the operation system of water necessary for the production cycles, for ancillary equipments and in compliance with the former USSR rules, it has been chosen a treatment system to bring to “zero” the waste water discharge from the steel plant complex. In this point of view, the “conventional” treatment stages of the make-up recycling water and steam generators feeding is as follows: flow rate 300 m 3/h, softening line, gravity sand filters, two lines of demiwater production for two different purposes, final storage, and sand filter backwash treatment and sludge dewatering lines. A “nonconventional” process is added to the previous one to treat different effluents of backwashing water of resins used for the demineralizing system for which the following scheme is foreseen: flow rate max. 600 m 3/d, neutralization, and two lines of RO having each three stages in series. The aim of this treatment plant is to produce industrial water with characteristics as above mentioned. The concentrated makes up the feeding of a multi-flash evaporator with a production of mixed crystals and condensate used as industrial water.

Simulation Of Integrated Systems Of Evaporation Plants And Different Energy Conservation Techniques

This paper describes the flowsheeting program EVAPSYS, developed for both design and evaluation calculations of any type of evaporation plants. The evaporation plant may be simulated either separately or integrated with an energy conservation unit such as a mechanical compressor, a steam ejector, or an absorption heat cycle. Different component modules are incorporated to provide the user with maximum flexibility in constructing any evaporation plant. These modules include an evaporator, heat exchanger, expansion vessel, mixer, splitter, mechanical compressor, and steam ejector. Other component modules are incorporated to enable the user to simulate single-stage absorption cycles. This arrangement allows the program to be executed in three different modes: evaporation plants, absorption heat cycles, and heat-pump-driven evaporation systems. Three subfunctions are incorporated for computing the overall heat transfer coefficients for falling-film evaporators, forced circulation heat exchangers and evaporators, and black liquor in vertical tube evaporators. The physical and thermodynamic properties of different liquors for evaporation applications and different working fluid pairs for absorption heat cycle applications are available in the database of the program. Three examples from the desalination, sugar, and pulp and paper industries are given to demonstrate the program capabilities in simulating complex flowsheets of evaporation systems.

Dynamic Simulation of an Absorption Heat Transformer Incorporated with an Evaporation Plant

Dynamic Simulation of an Absorption Heat Transformer Incorporated with an Evaporation Plant

Modernizing the desalination industry

The theme of this paper is that the desalination industry should modernize, recognizing that it is no longer a struggling, piecemeal effort, but a mature, large-scale enterprise, capable of using to the fullest the experience and technology that it has accumulated. In the early growth period many variations of design, process and materials were tried. Some were failures, but others worked well. The few well-performing designs have been copied many times over the years, with a tendency to resist all changes. In the meantime much has been learned. New processes and new materials have appeared, some early failures were found to have simple remedies, and some major economic relationships have changed. We now have the experience and scientific data to undertake a major upgrade of desalination equipment and processes. We know that in many parts of the world desalination is not a temporary solution, but a permanent part of life. We can assess realistically the water needs, energy costs, environmental costs, and other aspects of a plant, and design the best, most efficient plant size and plant type for each location. When the water demand is large, we can now build a suitable large unit, instead of a multiplicity of small units. In this paper I will summarize some of the changed conditions that now govern optimum design, and some of the opportunities we now have to design improved, more efficient, and more reliable plants at much lower cost than existing plants. The recent design of a 75 mgd (283,000 m 3/d) single unit vertical tube evaporator plant for the Metropolitan Water District of Southern California (MWD) embodies many of the concepts discussed, and will serve as an example.

An energy efficient evaporation process for treating bleach plant effluents

Abstract Simulation results of an energy efficient evaporation process are reported for the treatment of bleach effluents in the pulp and paper industry. Due to the low concentration of the effluent stream, the evaporation process must have a high degree of energy efficiency in order to compete with other treatment alternatives, such as ultrafiltration, adsorption, ion exchange and biological treatment. For a pulp and paper mill with an annual capacity of 335,000 ton of bleached kraft pulp, the capacity of the spent black liquor evaporation plant is about 7.5 ton water/ton pulp if its concentration is increased from 16 to about 65 wt% dry substance. An evaporation plant for the bleach effluent was simulated for a flow rate corresponding to 7.2 m3/ton pulp and a concentration of 1.4 wt% dry substance. This stream is to be concentrated to 16 wt% resulting in an evaporation capacity of 245 ton water/h. The total evaporation capacity for both evaporation plants would be increased by 91%. Optimal energy conservation strategies were investigated where an absorption heat transformer unit (AHT) is integrated with both the existing black liquor evaporation plant and the proposed bleach effluent evaporation process. Different process configurations were simulated using a flow sheeting program, developed for simulation of general multiple-effect evaporation processes and absorption heat pump systems. Using real operating data from a major Swedish pulp and paper mill, simulation results are reported for the optimum location of the AHT unit. Consequently, the energy requirements for both evaporation plants would increase by only 6.6%. One of the main practical features of this process is that integrating the AHT unit would require minimum changes in the existing plant. An economic analysis resulted in a cost of 23 SEK/ton of pulp for the first alternative where the pre-concentrated 16 wt% effluent stream is concentrated further to 65 wt%, within the existing black liquor evaporation plant, and then recycled to the recovery boiler. The corresponding cost of 49 SEK/ton of pulp would result for the second alternative, where the 16 wt% effluent stream is sprayed on the waste from bark peeling and co-burned in the bark boiler.

Kombi-Verdampferanlage zur Ausbildung von Chemiker/-innen und Ingenieur/-innen an der Ingenieurschule beider Basel

A pilot evaporation plant designed and built to train future chemists and process engineers at the Basle State Institute of Technology, Switzerland, is presented and first experiences from running it are discussed.

Design and experimental performance evaluation of an absorption heat transformer with self-circulation

A 10 kW experimental absorption heat transformer unit operating with self-circulation has been thoroughly tested. The self-circulation is obtained according to the thermosyphon principle. The pressure difference in the unit is achieved through a difference in hydrostatic pressures. Theoretical relationships for the pressure profiles within the different components of the heat transformer have been derived. Stabilising the self-circulation has been the primary objective in this work, rather than the optimisation of the efficiency of heating and cooling areas. A satisfactory stable operation with self-circulation has been achieved. A reference heat transformer plant, delivering 100 kW, has been designed and installed in a major pulp and paper mill. This unit is directly incorporated with one of the evaporation plants of the mill. Plant operation data obtained under real industrial conditions are presented.

Carry over of some high molecular weight organics from seawater to MSF distillates

Carry over of a few high boiling organic compounds in multistage flash evaporation (MSF) plants was studied using a bench top experimental set up. Eighteen known organic pollutants; i.e., nine phenols (phenol, 2,4-dichloro-, 2,4,6-trichloro-, 2,3-dichloro-, 4-chloro-, 4-bromo-, 2,4-dibromo-, 2,6-dibromo- and pentachloro phenols), five polycylic aromatic hydrocarbons (naphthalene, anthracene, chrysene, benzo(a)pyrene and dibenzo(a,h)anthracene), three phthalic acid esters (dimethyl, diethyl and di-n-butyl esters) and a high molecular weight n-alkane (tritetracontane) were selected for the studies at three plant operation conditions: (1) 95°C, 630 mm Hg, (2) 80°C, 350 mm Hg and (3) 50°C, 90 mm Hg corresponding to 1st, 5th and 15th stages of the MSF plant. Effect of an external deaerator to remove the organics through the vent system was also tested. Experimental results have been discussed in correlation with the temperature and vacuum conditions employed in the experimental set up.

An MSF evaporator for the UANW 9 and 10 power station. Design considerations based on energy and exergy

A thermoeconomic study was conducted to obtain the optimum design parameters of an MSF seawater evaporation plant to be associated with the UANW 9 and 10 steam power plants which can provide turbine extraction steam for the evaporator. The study used both energy (enthalpy) and exergy in cost accounting in order to compare the optimum design parameters which are obtained for each case. Cost accounting was based on realistic capital and fuel cost figures as obtained from recent bids. Based on current capital cost estimates for MSF evaporators and auxiliary boilers, as well as cost estimates for electricity and steam obtained from the thermoeconomic study, it was found that the optimum performance ratio and number of stages of the proposed MSF evaporator were slightly larger for the case of energy accounting compared to exergy accounting. For an evaporator having a capacity of 2600 m 3/h, the optimum performance ratio was found to be 10.3 for energy accounting compared to 10.1 for exergy accounting. The optimum number of stages was estimated to be 27 for energy accounting and 25 for exergy accounting. The optimum top brine temperature for both accounting methods was found to be close to the upper constraint value of 120°C. The optimum cost of distilled water was found to be slightly (about 7%) higher for the case of energy accounting compared to exergy accounting.

Irrigation management of soybean (Glycine max (L.) Merrill) in a semi-arid tropical environment. II. Effect of irrigation frequency on soil and plant water status and crop water use

Plant and soil water status, crop water use and water use efficiency, as affected by irrigation treatment, were monitored over two seasons for soybean cv. Ross, sown in the late wet season in the Ord Irrigation Area in north Western Australia. Irrigation treatments were, in both seasons, furrow irrigation after cumulative open pan evaporative losses of 30, 60 120 and 240 mm, and in the second year, an additional treatment, saturated soil culture (continuous furrow irrigation, analogous to irrigation after 0 mm pan evaporation). As expected, during periods of strong evaporative demand plant water status, as indicated by leaf water potential and leaf conductance of water vapour, was consistently greater in the more frequently irrigated treatments, while soil water depletion occurred to greater extent and depth in the less frequently irrigated treatments. However, total soil water use was directly proportional to crop growth, so that there was little evidence that water use efficiency was enhanced by restricting water supply in this environment. Indeed, efficiency of water use even under the continuous furrow irrigation system was comparable with that from other irrigation treatments. The responses are interpreted to imply that there is unlikely to be any economic advantage to the use of limited supplemental irrigation in this environment.

Optimal Control of Evaporator and Washer Plants

Tests with radioactive tracers were used for experimental analysis of a multiple-effect evaporator plant. The residence time distribution of the liquor in each evaporator was described by one or two perfect mixers with time delay and by-pass flow terms. The theoretical model of a single evaporator unit was set up on the basis of its instantaneous heat and mass balances and such models were fitted to the test data. The results were interpreted in terms of physical structures of the evaporators. Further model parameters were evaluated by conventional step tests and by measurements of process variables at one or more steady states. Computer simulation and comparison with the experimental results showed that the model produces a satisfactory response to solids concentration input and could be extended to cover the steam feed and liquor flow inputs. An optimal feedforward control algorithm was then derived for a two unit, co-current evaporator plant. Because the operation of such a plant is affected by the out...

A Training Simulator for a One-stage Evaporator Plant

In this paper an integral training system for elementary control principles and tuning of PID-controllers is described. This training system runs in IBM PC/AT compatible microcomputers, and is programmed with Fortran. The training is based on a simulated process, training material and interactive training sessions. The system is designed such that the presence of an instructor is not necessary during the training sessions. This system shows clearly that microcomputers equipped with graphics terminal suit well for used as training simulators.

Low temperature reject heat utilization for desalination; Economical and technical aspects

The economics of medium and large sized (1'000…10'000 m 3/d) MSF/ME plants which utilize reject heat at temperatures between 50…90 °C is investigated. It is shown that for a cogeneration plant based on the Rankine cycle in combination with an evaporative desalination plant, there exists a steam condensation temperature (60…80 °C) below which the water production of the cogeneration plant is higher than the production of a power equivalent reverse osmosis plant. Power equivalent means, that the reverse osmosis plant would utilize the electricity otherwise lost when the same Rankine cycle is operated at higher condenser temperature. In spite of the higher investment costs for the evaporative plant, the specific water costs are lower than those for the power equivalent RO plant. Using a Rankine cycle for cogeneration, optimization of reject heat temperature levels is therefore crucial for obtaining economically favourable conditions. Further it is shown, that for todays and assumed future electricity rates and oil prices, the MSF/ME when powered by diesel reject heat produces cheaper water than RO or VC plants. It is necessary however, that the MSF/ME can cope with the inevitable load variations of the diesel power station. Our companys contribution in this field is briefly described.

A new technique for measuring thickness of thin solid films

AbstractA new technique has been developed for measuring the thickness parameter for any thin solid films. Various thin films of silver, aluminium and antimony have been prepared by using vacuum evaporation plant at the vacuum of 10−5 torr. The films have been scratched by a fine metal pin. By employing a semi‐silvered cylindrical convex lens, a point contact has been established between a silvered scratch‐film and a cylindrical lens. Multiple beam Fizeau interference fringes have been obtained over the surface of thin films. Across the step of the scratch, because of height difference, the shift in the fringes have been observed. Due to the axis of point contact, no ambiguity in allocation of ringe order has been obtained. The thicknesses of silver, aluminium and antimony thin films have been determined very precisely. The technique gives high resolution with a good degree of reproducibility and implications are discussed.

Vacuum evaporation plant for concentration of yeast suspensions

Vacuum evaporation plant for concentration of yeast suspensions