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Flakt Pulp Dryer 3.2 meter wide 1987------ Never Been Used * Recently SOLD FOR SALE and wholly owned by Brickman Machinery:
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SPECIFICATION INDEX :
1. INTRODUCTION
2. TECHNICAL DATA
General
Pulp web
Steam and condensate system
3. DESIGN AND FUNCTION
General
Drying principle and process
Cooling
Drying cabinet and turning roll towers
Drying cabinet
Turning roll towers
Tape threading and drive systems
General
Start and adjustment of the drive system
Nip roll adjustment
Control roll adjustment
Circulation fans
Steam and condensate system
Fire extinguishing system
Heat recovery system
Equipment for service and maintenance
Lifting gear for the blow boxes
Illumination
Vacuum-cleaning system
Operational controls, monitoring and alarm functions
INTRODUCTION
The FCSC special dryer is used for drying CTMP pulp. The dryness of the pulp increases from 48% to 85% while the web moves through the dryer.
The dryer is supported on a framework of steel beams cast into the concrete foundation. The drying cabinet is divided into 16 fan sections. Each section contains circulations fans, steam heated coils and blow boxes.
At the infeed and outfeed ends of the drying cabinet are the turning roll towers with bearings and chain transmissions for the turning rolls. The space between the towers is known as the turning end.
The pulp is dried by warm air being blown onto the web as it is fed through the drying cabinet. The air-stream maintains the web a few millimetres above the lower blow boxes which means that the web is fed through the dryer suspended on an air cushion. The pull necessary to advance the pulp through the dryer is provided by the nip exerted by two rolls, the lower of which is motor-driven. The upper nip roll presses the web against the driven roll.
The lower level is the cooling level. Cooling air at a temperature of about 20oC is blown onto the web to reduce its temperature before it leaves the dryer.
At the input end the web passes over a roll fitted with a device that measures the web tension. The measured web tension is used to adjust the speed and pulling force of the motor driven roll.
For inspection and maintenance purposes there is a catwalk along each side of the dryer and two at each end.
In addition to the dryer itself the system also includes a heat recovery system, a vacuum-cleaning system and separate condensate system. The heat recovery system uses the hot wet air from the dryer for preheating of the fresh air going into the dryer. The vacuum-cleaning system is used to clear the dust and other impurities from the mesh-wire in front of the heating coils. The separate condensate system collects the condensate generated when the steam is cooled by the heating coils.
TECHNICAL DATA
General
Kind of Pulp: CTMP
Stock Freeness: m/s CSF 150 – 400
Capacity: tonnage 250- 300 / 24 hours
Dryness of pulp entering dryer: % BD 48
Dryness of pulp leaving dryer: % BD 85
Water Evapouration: 8502 kg/hour
Net length of dryer: 26 200 mm or 28.6 yards
Net width of dryer: 6900mm or 7.5 yards
Net height of dryer: 7050mm or 7.7 yards
Number of decks: 14 pcs
Number of cooling decks: 1 pcs
Number of sections: 16 pcs
Number of circulation fans: 48 pcs
Power consumption measured
in switchgear room: 440 Kw
Compressed air requirements: 6 ATG
Pulp Web
Width of pulp web entering dryer: 3320 mm or 130.7 inches
Width of pulp web leaving dryer: 3200 mm or 125.98 inches
Normal basic weight 100 % BD: 1000 g/m2
Normal processing speed at 1000 g/m2: 55 meters/min or 60 yards a min
Min temp of pulp web entering dryer: 55 degrees cel
Pulp temp in bale after cooling with +20 degrees cel air: 34 degrees Celsius
Steam and condensate system
Maximum permissible steam pressure at dryer coils: 11.2 ATG
Permissible steam temp at 11.2 ATG max: 195 degrees cel
Permissible steam temp at < 11.2 ATG: 225 degree cel
Heat consumption per kg evapourated water: 2730 Kj / kg
DESIGN AND FUNCTION
Drying principle and process
When the wet pulp moves through the dryer warm air is blown continuously onto the web. The warm air causes the water in the web to evaporate, the result of which is that the air in the dryer is cooled off while at the same time the humidity of the air increases. In order not to be come saturated, therefore, the air must be warmed up continuously. This is achieved by means of heating coils through which hot steam is circulated.
When the dryer is in operation the air humidity will gradually increase and would eventually reach the point of saturation and the drying effect would be lost. Some of the wet air, however, is extracted continuously by the heat reclamation system and replaced with warm dry air.
The circulation flow generated by the drying process: The warm air is blown by the circulation fans through the pressure chambers of the fan stacks and into the end openings of the blow boxes. The function of the lower blow boxes is to keep the web suspended during the passage through the dryer while the evaporation is initiated by the warm air being blown onto the bottom of the web. The upper blow boxes improves the evaporation by blowing warm air onto the top of the web. Since the function of the upper and lower blow boxes are not entirely similar, their perforation patterns are different.
After having reached the pulp web and lost some of its heat, the circulation air continues up/down between the blow boxes and is then diverted towards the steam heated coils. It is sucked through the coils by the circulation fans after which it is again blown into the blow boxes.
In this way the air continues to circulate upwards through the various decks of the dryer. On reaching the upper deck some of the air is extracted by the wet-air fan through openings in the ceiling of the drying cabinet.
Cooling
During its passage through the lower deck, the cooling deck, the pulp is cooled down to approximately 35 oC. This deck only has the lower type of boxes blowing the cooling air at a temperature of 20 oC onto the web from underneath. The air is introduced at the lead carrier side and leaves the drying
cabinet at the drive side.
Drying cabinet and turning roll towers
Together with the turning roll towers the drying cabinet constitutes the major and central component of the FCSC dryer. The mechanical link between the cabinet and the towers is the turning rolls which are located inside the cabinet and supported on bearings in the towers. Between the towers and the cabinet is a thermal insulation wall.
Drying cabinet
The drying cabinet consists of 16 fan sections and 2 turning ends. The cabinet is designed with a ceiling and roof, the space between which serves as a duct for extraction of wet circulation air.
Fan sections
All fan sections are identical, their main components being:
1 fan stack
1 heating coil section
84 blow boxes, upper type
84 blow boxes, lower type
There are 3 axial flow circulation fans installed above each other in the fan stack. The space in front of the fans is called the pressure chamber, common for all fans in the stack.
The fans are mounted in wall sections which are attached to the cabinet framework and constitute part of the side walls of the cabinet. Each fan stack has two heating coils, one on either side.
The walls of the pressure chamber are provided with inspection ladders for access to the fans. The electrical function of the fans is described under the heading “Circulation fans”.
The blow boxes are made of galvanized steel plate and constitute part of the section that connects the fan stack with the heating coil compartment. Appendix 3 shows the location of the blow boxes in the dryer.
The open end of the blow boxes is turned towards the pressure chamber in the fan stack. Between the boxes are walls of steel plate onto which the boxes are fitted. The lower type boxes are fixed to the walls whereas the upper type boxes are attached so that they can be moved vertically.
All boxes taper in height from half their length towards the heating coil compartment. Consequently, the height of the covered end of the box which faces the heating coil compartment is lower than the end facing the pressure chamber. This means that it is possible to lift up the end of the upper type boxes facing the heating coil compartment, thus gaining access for inspection and cleaning of the boxes.
A description of the lifting arrangement for the blow boxes can be found under the heading “Equipment for service and maintenance”.
On the carrier side of each deck there is a tape tray of sectional aluminium bolted onto the top of the lower type blow boxes.
The covered ends of the blow boxes are turned towards the heating coil compartments. The steam heated coils constitute the partitions between the coil compartments and the fan stacks. In front of the coil are mesh-wire filters that separate the dust from the pulp web. The coil compartments are provided with inspection doors for cleaning the filters.
In every other section there is an opening in the coil compartment ceiling for evacuation of circulation air to the heat reclamation system. The floors in the remaining sections having openings for the introduction of fresh air.
Turning ends
At the infeed end are 8 turning rolls, one of which is for the cooling deck, 1 blow box table, and 14 sets of end boxes. The blow box table consists of 4 lower type blow boxes fitted closer together than the other blow boxes in the dryer.
The end box sets consists of “blow boxes” without perforation, welded together. There is no air, therefore, being blown through these sets. Their task is to provide support for the pulb web before and after it passes the turning rolls.
The outlet and has 7 turning rolls and 14 sets of end boxes.
Turning roll towers
These towers are designed as steel framework which rest on a concrete foundation and serve as a support for the bearings and drive mechanisms of the turning rolls.
Steam and Condensate System
1 pipe system for steam and condensate
32 steam heated coils type QLBD (also known as air heaters)
2 primary condensate tanks
1 water seal (U bend)
1 condensate tank
2 condensate pumps
The essential parts of the heated coils are copper tubing and aluminium fins. To facilitate an even distribution of the steam to the coils, a orifice plate is fitted in the outlet from each coil.
When the steam from the existing steam system moves through the coils, heat is given off to the dryer circulation air. This causes condensation of the steam. The condensate thus obtained flows by gravity into the two primary condensate tanks.
To prevent air locks in the coils a certain portion of the steam, also known as pull steam, must pass through the coils without condensation (approx. 15%). This causes some steam to be fed into the primary condensate tanks. In order to fully utilise the heat from this steam it is fed into 2 + 2 secondary coils which are of exactly the same type as the other 28 coils.
The condensate from the primary condensate tanks and the secondary coils is collected in a common condensate tank from where it is pumped over to the steam generation section by one of the two condensate pumps. One pump is always on stand-by. In order not to drain the condensate tank a certain portion of the condensate is returned to the tank via throttle discs.
The surplus steam, known as flash steam, that collects in the condensate tank is transferred to a steam heated coil of the QLGC type where it is used to heat the fresh air going into the dryer.
Fire extinguishing system
The dryer is equipped with a fire extinguishing system in which steam is used as the extinguishing agent. The main components of the system are a manually operated shut off valve for the steam and a steam pipe leading to the fan stacks in section 5 and 13. Thus, in the event of fire the steam is distributed in the dryer by means of the circulation fans.
Heat recovery system
1 heat exchanger comprising 12 tube exchangers type QGBA
1 wet air fan type PMCA
1 radial-flow inlet air fan type HCLP
1 steam heated coil type QLGC
Ductwork between the respective units
Equipment for temperature monitoring
The inlet air fan provides ambient air from inside the building. The air is drawn through the heat exchanger where the temperature is raised from about 25 oC to 77 oC, From the exchanger the air is fed through the coil where the temperature is increased even more. The amount of air being drawn is regulated by the frequency controlled fan motor.
On leaving the coil, the air is introduced through the floor of the coil compartments. Once inside the dryer the inlet air mixes with the circulation air and participates in the drying of the web.
Since outside air is introduced continuously into the dryer the corresponding amount of air must also leave the dryer. Extraction takes place through openings in the ceiling of the coil compartments. These openings lead into the wet-air duct between the dryer cabinet’s ceiling and roof. The exhaust air is then drawn through the heat exchanger by the wet-air fan. Like the motor of the inlet air fan the motor of this fan is also frequency controlled. With proper control of these two fans it is therefore possible to achieve zero pressure in the drying cabinet.
When the exhaust air passes through the exchanger some of its hat is given off to the inlet air. On leaving the heat exchanger the exhaust air is expelled into the atmosphere through a chimney.
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Copyright © 2000-2004 Brickman Machinery
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