Aerial dryer in the production of chip boards

Contents

INTRODUCTION

1. CHARACTERISTICS OF MANUFACTURED PRODUCT

2. RAW MATERIALS

2.1 Characteristics

2.2 Monitoring

3. CPD PRODUCTION TECHNOLOGY

4. SELECTION OF CPD PRODUCTION METHOD. PRESSING CYCLE

5. LINE POWER

6. HEAT ENGINEERING CALCULATION

7. CALORIFER CALCULATION AND SELECTION

8. AUTOMATION OF AERIAL DRYERS

9. SAFETY, HEALTH AND ENVIRONMENTAL REQUIREMENTS

CONCLUSION

LIST OF SOURCES USED

List of graphic material:

Sheet 1 - Thermal Unit (Sheet A1)

Introduction

Wood in one form or another is used in all sectors of the national economy. It is very difficult to fully meet all the growing needs for this raw material. Harvested wood is far from fully used, most of it goes to waste.

In the process of logging, along with business wood, a large amount of fine and wood wood (non-coarse) is obtained, which was used mainly as fuel. The increasing use of natural gas, coal, fuel oil and peat as fuels makes the rational use of all types of wood and wood waste even more acute. The woodworking industry, the production of particle boards (CPDs), contributes significantly to this problem.

CPDs are used in the furniture industry, construction, as well as in other sectors of the national economy. They have a number of valuable advantages over lumber, carpentry, etc.

The advantages of slabs include:

- uniformity of properties in different directions along the plane;

- Relatively small size changes under variable humidity conditions;

- the possibility during production to give them increased resistance to fungi and insects, reduced water and moisture absorption, fire resistance, etc.;

- Use of wood wood and non-wood waste from woodworking enterprises for their production;

- almost complete automation of the production process and its high efficiency.

Select the method of production of the dsp. pressing cycle

Pressing is the process of obtaining from plastic masses of products of given sizes and configuration in a mold under the pressure of a punch. The product on hydraulic presses is pressed by two methods: compression (direct) and transfer (casting); compression pressing can be cold and hot.

The correct press mode of the boards should be considered to ensure high quality of the boards produced and maximum press productivity.

Mode indicators include: 1) time of plates closing and specific pressure rise to the specified value; 2) the amount of specific pressure during the entire pressing process; 3) press plate temperature; 4) time of plate holding in press (total and by pressing stages).

Pallets with pieces of chip carpet by conveyor at speed significantly exceeding that of conveyor, on which formation is performed, are opened from the latter and fed into press for cold pressing. Underpressure is carried out at the normal temperature of the workshop (without heating), and therefore is often called cold.

The carpet is several times (4-10) larger than the thickness of the finished plate. The chip layer is very loose, and therefore the fine particles are sprinkled down onto the tray during transport of the carpet, so that the opposite surfaces of the plate are obtained from different particle sizes, which can lead to warping of the finished plates.

Pressurization is carried out in order to reduce the spillage of fine particles and the showering of edges (and the associated losses of resin-coated chips) during transportation, as well as to reduce the thickness of the carpet, so that it can be more conveniently loaded between hot press plates. Therefore, a method of cutting the carpet across and cutting its longitudinal edges after cold pressing is highly desirable. These operations are performed with the action of special pressing devices. The edges of the carpet in this case have the correct shape. The chips obtained by such cutting are returned for reuse in the hoppers of the forming machines. Using this method, waste from finished boards during cutting is somewhat reduced .

Single-light hydraulic presses with upper cylinder arrangement are used for underpressure. It is pressed at specific pressure from 5 to 30 kG/cm2. Usually, presses with a specific pressure of 10-15 kG/cm2 are used in existing enterprises.

After cold pressing the plates are supplied to hot pressing. The nine-storey hot press consists of three mechanisms installed along the centerline of the main conveyor: a hydraulic multi-storey (multi-lumen) press with heated plates and lifting loading and unloading floors.

Both storeys are designed in the same way. They are a welded frame on which several horizontal rows of paired rotating rollers are mounted. The number of rows of rollers corresponds to the number of press lumens. Storey has mechanism for its lifting and lowering. Lifting is done automatically to one floor after the previous one is loaded with the next tray with a chip layer. In order to reduce the harmful effect of thermal radiation of hot press plates on resin polymerization, in the latter structures, as the stack is loaded, a lifting curtain is lowered to one floor or a lifting curtain is installed between the press and the stack. The filled storey is raised and mounted against the press hot plates. The operator from the control panel includes a loading mechanism that pushes all the trays between the hot plates of the press at the same time. Once the plates have been loaded, the loading mechanism returns to its original position and the stack is lowered down until the upper row of rollers flush with the conveyor loading the chip-bed tray onto the stack.

At the same time, hydraulic cylinders are turned on, which lift the lower crossbeam with the lower hot plate resting on it. Then at further lifting of crossbeam hot plates one after another lie on carpet and rise up until carpet of upper floor is squeezed between two last plates of press. Thereafter, the pressure of the liquid in the cylinders is rapidly increased to the limit value set by the pressing mode. Distance gaskets are laid along both longitudinal edges of hot plates, which determine the specified thickness of the plate. The thickness of the gaskets shall be equal to the sum of the thickness of the tray and the nominal size of the plate, since the tray is pushed together with the plate between the two gaskets. Gaskets are made of metal with low coefficient of thermal expansion. The thickness of the press plates should be such that they are sufficiently rigid and do not bend during pressing. It is usually in the range of 80-120 mm depending on the size of the press plates. The length of the press plates is usually 150-200 mm, and the width is 200-250 mm larger than the final dimensions of the produced plates.

Press plates are heated with steam or hot (superheated) water to a temperature of 140-160. Before unloading the boards, the unloading rack must be raised to the extreme upper position so that its rollers are on the same level as the press plates. The unloading mechanism, arranged according to the same principle as the loading mechanism, but equipped with special grips instead of pushers, grabs the pallets by special triangular protrusions attached to them and removes all pallets with plates from the gaps between the hot plates. After that, the unloading of pallets with finished plates from the storey begins. Plates are unloaded by chain conveyor with pusher. After the first slab is unloaded, the storey is automatically lowered to one floor and the second slab is unloaded, etc. The plates pass under the lower end of the pusher and thus it does not interfere with the unloading of the storey. Electric interlock is made in such a way that the next plate is removed from the rack only when space from the previous one is free on the conveyor.

In a batch pressing method, one or more bags are loaded into a hot press which operates in a set mode. Once the plates are formed, the press is stopped and loaded.

After processing in mixers, the chip-polymer mass is somewhat compacted and formed into a so-called bag (during batch pressing) or into a carpet (during continuous pressing).

The Becken Van Hüllen press (manufactured by Germany) has the following technical characteristics:

- plate length - 365 cm;

- plate width - 175 cm;

- plate thickness - 12 cm;

- number of hot plates - 10;

- total pressing force - 1200 t;

- specific pressing pressure - 20 kg/cm2;

- plate closing speed: 50 mm/sec

The press is loaded and unloaded simultaneously on all floors.

The slabs are heated with superheated water. The temperature of the plates is controlled and controlled using thermocouples and corresponding recording devices. For ease of maintenance, the press is deepened 2.3 m from the floor surface. Loading of pressed bags and unloading of finished plates on multi-storey presses is usually mechanized. Chambers, roller tables and loading and unloading mechanisms are installed on the sides of the press.

Automation of aerial dryers

The air temperature is controlled by changing the coolant flow rate through the heater in accordance with the signal of the temperature sensor installed in the drying unit. If the system has 2 heating circuits, a second heater is installed after the fan, in which the temperature is finally controlled, and the first one serves for preheating the air.

Temperature control is carried out by various regulators (for example, a three-position regulator of the PT3 type, working complete with a pulse breaker and an electric actuator; accuracy of regulation ±1ᵒC).

The circuit provides protection of the heater from freezing (according to the sensor signal) by closing the outdoor air valve with a non-operating system and connecting preliminary electric heaters with a fully open valve on the coolant before starting the system.

The circuit can serve plenum ventilation plants combined with air heating. The system allows for full or partial recycling. Temperature of air supplied to the unit is maintained by temperature regulator acting on actuator of coolant supply to calorifer. The operation of the plant according to the flow scheme or the recirculation rate varies depending on the ratio of the opening of the outdoor air valve, the discharge of the spent drying agent and the valve of the mixing chamber. The air is blown by the supply fan and sucked by the exhaust.

Conclusion

According to the assignment, a batch drying unit (aerial dryer) for the production of chipboard was designed, which has the following technical and economic parameters:

Per hour = 504m2/hour .

ƩQ=3010588,26 kJ/h

T=1700C

W = 40.8 kg/h

Air speed: W = 0.2 m/s

Sushilka_Aerofontannaya_Red_1.dwg