CN103438678B - Efficient energy-saving pulp dewatering and drying equipment - Google Patents

Abstract

The invention discloses a high-efficiency and energy-saving paper pulp dehydration and drying equipment, which mainly consists of a double-roller squeezer with a hot-roller structure, a two-stage drying chamber, a microwave generator, a heat-conducting oil boiler, an air preheater and a heat exchanger devices etc. The feature of the twin-roller press with hot roll pressing structure is that it can use the residual heat of the system exhaust to conduct contact heat transfer to the pulp board, which plays a role in optimizing the drying conditions of the pulp; the two-stage drying chamber respectively The pulp is dried at a constant speed and decelerated; the microwave generator is installed and works near the inflection point of the pulp from the dehydration stage at a constant speed to the dehydration stage at a deceleration rate, and its function is to increase the drying rate of the pulp deceleration drying section and reduce energy consumption. The air preheater is used to recover the waste heat of the flue gas discharged from the heat transfer oil boiler, and to preheat the fresh air supplemented by the system. The invention has the characteristics of simple equipment, fast drying rate, high energy utilization rate, wide application range and the like.

Description

High-efficiency and energy-saving pulp dehydration and drying equipment

technical field

The invention belongs to the technical field of industrial drying, and can also be applied to other industrial drying fields. It is a process and equipment designed for pulp drying, and in particular relates to a high-efficiency and energy-saving pulp dehydration drying equipment.

Background technique

my country imports a large amount of pulp every year, and drying the pulp can make the pulp easy to store and transport. At present, the commonly used technologies for pulp drying mainly include airflow drying and hot air drying (that is, flash drying).

The main process of air-flow drying is: after the pulp with a dryness of about 3% is squeezed by the squeezer, the dryness reaches about 50%; The pulp is in the form of flocs with a diameter of several millimeters; the pulp flocs are sent to the bottom of the vertical drying tower, and are blown from bottom to top by hot air in the tower. When a certain dryness is reached, the pulp is discharged out of the drying tower with the hot air. into the cyclone separator. After the pulp flocs are separated by the cyclone separator, they are sent to the next drying tower for drying again until the required dryness is reached. Airflow drying has higher thermal efficiency and faster drying speed, but its equipment is more complicated, installation and maintenance are more difficult; and its operation requires a lot of mechanical work.

Hot air drying is the most widely used drying method at present. It mainly heats the air through a heat exchanger and uses the hot air to take away the moisture of the pulp. It has the advantages of large processing capacity, low cost, and easy automation, but it also has disadvantages such as high energy consumption and poor product quality.

Microwave drying is the body heating of materials caused by dielectric loss in the electromagnetic field. During the drying process, the moisture content inside the wet materials is often higher than that on the surface, causing a large amount of moisture inside the materials to absorb microwave energy and convert it into heat energy. Therefore, the temperature inside the materials higher than the surface. At the same time, due to the heating inside the material, the water is rapidly vaporized, water vapor is generated, and a pressure gradient is formed; at this time, the temperature gradient and pressure gradient of the wet material are consistent with the diffusion direction of water, which greatly improves the drying process. Moisture migration conditions, thus effectively improving the diffusion rate of water and accelerating the drying speed. At the same time, due to the existence of the pressure gradient, microwave drying has the characteristics of drying from the inside to the outside: for the material as a whole, the inner layer of the material is dried first, thus overcoming the formation of skin due to the outer layer of the material being dried first in the hot air circulation drying. The core structure, which prevents the moisture inside the material from continuing to migrate outward, greatly improves the moisture migration conditions during the drying process, thereby increasing the diffusion rate of moisture and speeding up the drying speed.

Microwave drying has the advantages of fast heating speed, high energy utilization rate, and small equipment footprint. Its main disadvantages are poor heating uniformity, difficulty in controlling product quality in the later stage of drying, limited production capacity, and high equipment maintenance costs.

The study found that there are two stages in the pulp dehydration drying process: uniform drying stage and deceleration drying stage. In the uniform drying stage, the drying rate has little to do with the moisture content of the material itself. Increasing the flow rate and temperature of the external airflow and reducing the humidity of the external ambient air are the key to increasing the drying rate in the uniform drying stage; while in the decelerating drying stage, rapidly increasing the internal temperature of the object Temperature is an effective way to increase the drying rate.

Combining the advantages and disadvantages of hot air drying and microwave drying, combined with the characteristics of the pulp dehydration process, consider using microwave drying in the hot air drying process: that is, when the hot air drying reaches the critical moisture content point, microwave drying is introduced to quickly increase the internal temperature of the object. To achieve the purpose of improving the drying rate.

As shown in Figure 1. The uniform speed drying stage of pulp dehydration adopts hot air drying. When the drying progresses to the vicinity of the constant speed and deceleration critical point, microwave drying is used. The microwave is used to heat the material as a whole, especially the internal heating, so that the moisture inside the pulp can be quickly evaporated and discharged. It is beneficial to shorten the drying time and improve the drying efficiency.

Contents of the invention

The object of the present invention is to provide a high-efficiency and energy-saving paper pulp dehydration drying equipment with high energy utilization rate and high production efficiency.

For realizing the above object, technical solution of the present invention is:

The invention is a high-efficiency and energy-saving pulp dehydration and drying equipment, which includes a frame, a pulp cutting mechanism, a heat exchanger, an air preheater, a microwave generator, a double-roller squeezer, a hot air circulation pipeline, a material transportation system, a drying room, heat transfer oil boiler; on the frame from left to right are installed a double-roller press machine, drying room, heat exchanger, pulp cutting mechanism, the heat transfer oil boiler is installed on the frame and below the drying room, The microwave generator is installed on the frame and above the drying room. The twin-roll press is located at the beginning of the drying room and connected to the material transportation system in the drying room; the pulp cutting mechanism is located at the end of the drying room. The mechanism is connected to the material transportation system in the drying room through the hot air circulation pipeline, and the heat exchanger is respectively connected to the heat-conducting oil boiler, the drying room and the air preheater.

Described drying room is divided into two sections, and it is made of the first drying room and the second drying room; The first drying chamber and the second drying chamber are separated by hot air circulation pipes; material transportation systems are installed in the first drying chamber and the second drying chamber respectively.

The microwave generator is installed between the first drying chamber and the second drying chamber and above the drying chamber, and the microwaves generated by the microwave generator act on the end of the first drying chamber and the beginning of the second drying chamber.

The heat exchanger is an air-heat transfer oil heat exchanger, and the body of the heat exchanger is provided with a heat transfer oil inlet and an outlet, a hot air inlet and a hot air outlet; the heat transfer oil inlet is connected to a heat transfer oil boiler, and the heat transfer oil comes from Heat conduction oil boiler; the hot air outlet leads to the drying room through the hot air circulation pipe, and the hot air inlet is connected to the air preheater, and the high temperature flue gas of the boiler is used to preheat the fresh air to improve energy utilization.

The two-roller press includes a hopper, a rolling box, a first conveyor belt, a rolling cylinder, a second conveyor belt, and a hot rolling tube; the hopper is installed at the entrance of the rolling box and the outlet of the hopper Opposite to the first conveyor belt installed in the rolling box, two symmetrically installed in the rolling box, the output end of the first conveyor belt and the input end of the second conveyor belt are respectively connected to the input end and output end of the two roller pressing cylinders. The output end of the second conveyor belt is connected to the input end of several rows of symmetrically arranged hot rolling tubes. The hot rolling tube is a hollow roller, and fins are arranged inside the roller to enhance convection heat transfer. One end of the roller passes hot air The circulation pipe is connected with the hot air inlet of the drying chamber, and the other end is the hot air outlet.

The air preheater is composed of a shell and a central rotor, the central rotor is rotatably installed in the outer shell, the shell plays the role of external sealing and gas diversion, and the central rotor plays the role of a heat exchanger.

After adopting the above scheme, the present invention has the following advantages:

1. The present invention fully utilizes the respective advantages of hot air drying and microwave drying, couples and utilizes microwave heating and hot air heating technology to dry the pulp, and makes up for the low efficiency of hot air drying with the high efficiency of microwave drying; The advantages of low drying cost and large output make up for the inability of microwave drying to carry out mass production.

2. The present invention recycles and utilizes the waste heat of the system as much as possible to realize efficient utilization of system energy: one is to use the air preheater to recover the waste heat of the flue gas discharged from the heat transfer oil boiler; The pressure mechanism uses the hot roller to recycle the residual energy of the hot and humid air discharged from the system, which is used to increase the initial temperature of the pulp board; the third is to recirculate the hot exhaust gas in a certain proportion. Therefore, the whole drying equipment has high energy utilization efficiency.

3. The present invention adopts semi-automatic control, and can set different working parameters such as transmission rate, hot air temperature and hot air volume according to different types of pulp, so as to improve the production efficiency and energy utilization rate of the device.

In summary, the present invention has the advantages of simple equipment structure, wide application range, high energy utilization rate and high production efficiency, and can well replace the existing pulp air drying technology, bringing energy-saving and emission-reducing benefits to enterprises. If certain modification is carried out to the equipment of this case, the present invention can even be applied to the dehydration and drying of other industrial and agricultural products. Therefore, the present invention not only has the characteristics of energy saving and high efficiency, but also has wide application and expansion space.

The present invention will be further described below in conjunction with the accompanying drawings and specific implementation examples.

Description of drawings

Figure 1 is a schematic diagram of the principle of coupled microwave drying in the hot air drying process;

Fig. 2 is a structural block diagram of the present invention;

Figure 3A is a front sectional view of the present invention;

Figure 3B is a top view of the present invention;

Fig. 4A is the isometric view of heat exchanger of the present invention;

Fig. 4B is a front view of the heat exchanger of the present invention;

Fig. 4C is a top view of the heat exchanger of the present invention;

Fig. 5 is a sequence diagram of hot air flowing through each device of the present invention;

Fig. 6 is a schematic structural view of the interior of the twin-roll press of the present invention;

Fig. 7A and Fig. 7B are the isometric view and three views of the air preheater of the present invention.

specific implementation plan

As shown in Fig. 2, Fig. 3A and Fig. 3B, the present invention is a high-efficiency and energy-saving pulp dehydration and drying equipment, which mainly consists of a frame 1, a pulp cutting mechanism 2, a heat exchanger 3, an air preheater 4, and a microwave generator. Device 5, twin-roller press 6, hot air circulation pipes 71, 72, 73, material transportation systems 81, 82, drying chamber 9, heat transfer oil boiler 10, etc.

Described drying chamber 9 is divided into two sections, and it is made of first drying chamber 91 and second drying chamber 92. The first drying chamber 91 and the second drying chamber 92 are connected to each other and installed in the middle of the frame 1. The two sections of drying chambers are separated by partitions, and the first drying chamber 91 and the second drying chamber 92 are circulated by hot air. The pipe 73 communicates. Material transport systems 81 and 82 are respectively installed in the first drying chamber 91 and the second drying chamber 92, and the outside of the drying chamber 9 is wrapped with thermal insulation material to reduce heat loss. The pulp is dried at a constant speed in the first drying chamber 91 and dried at a reduced speed in the second drying chamber 92 .

On the frame 1, a double-roll press 6, a drying chamber 9, a heat exchanger 3, and a pulp cutting mechanism 2 are installed in sequence from left to right, and a heat transfer oil boiler 10 is installed on the frame and below the drying chamber 9 , wherein the twin-roll press 6 is located at the beginning of the first drying chamber 91 and is docked with the material transport system 81 in the first drying chamber 91; the pulp cutting mechanism 2 is located at the end of the second drying chamber 92, that is, the outlet At , the pulp cutting mechanism 2 is docked with the material transport system 82 in the second drying chamber 92 . The pulp cutting mechanism 2 is controlled by a computer to cut the cardboard at a certain time interval, so that the size of the cardboard is convenient for packing. The cardboard cutting mechanism 2 is provided with a microwave short-circuit device to prevent microwave leakage from causing harm to workers.

The microwave generator 5 is installed on the frame 1, between the first drying chamber 91 and the second drying chamber 92 and above the drying chamber 9, and the microwaves produced by the microwave generator 5 act on the first drying chamber 91 The end and the beginning of the second drying chamber 92. The microwave generator 5 contains several magnetrons with the same power, and the microwaves produced by some magnetrons act on the beginning of the first drying chamber 91, and the microwaves produced by other magnetrons act on the second drying chamber 92. the end. In actual work, the number and position of magnetrons to be turned on can be determined according to specific working parameters; and different production needs can be adapted to by adjusting the magnitude and position of microwave action power. The microwave generator 5 works near the critical moisture content point of the pulp, and its function is to put into operation in the initial stage of deceleration drying to rapidly increase the temperature of moisture inside the pulp sheet, thereby increasing the drying rate in the deceleration drying stage.

The material transportation system 81 is mainly composed of a driving device 811, a conveyor belt 812, a roller 813, etc., the conveyor belt 812 is wound on the roller 813, and the driving device 811 provides power for the conveyor belt 812 to the conveyor belt 812 in the drying chamber 9, according to Production needs can be controlled by the computer to convey the speed.

As shown in Figure 4A, Figure 4B, and Figure 4C with reference to Figure 3A, the heat exchanger 3 is an air-heat transfer oil heat exchanger. The body of the heat exchanger 3 is provided with a heat transfer oil inlet 31 and a heat transfer oil outlet 32 , a hot air inlet 33 and a hot air outlet 34 . The heat transfer oil inlet 31 is connected to the heat transfer oil boiler 10 , and the heat transfer oil comes from the heat transfer oil boiler 10 ; the hot air outlet 34 leads to the first drying chamber 91 through the hot air circulation pipe 71 . The hot air inlet 33 is connected to the air preheater 4, and the high temperature flue gas from the boiler is used to preheat the fresh air to improve energy efficiency.

As shown in FIG. 6 , the twin-roll press 6 includes a hopper 61 , a rolling box 62 , a first conveying belt 63 , a rolling cylinder 64 , a second conveying belt 65 , and a hot rolling pipe 66 . The hopper 61 is installed at the entrance of the rolling box 62 and the outlet of the hopper 61 is opposite to the first conveyer belt 63 installed in the rolling box 62, two symmetrically installed in the rolling box 62, the first conveyor belt The output end of 63 and the input end of the second conveyer belt 65 are connected respectively at the input end and output end of two roller cylinders 64, and the output end of the second conveyer belt 65 is connected with the input end of several rows of symmetrically arranged hot rolling tubes 66. Connected, the heat rolling tube 66 is a hollow roller 66, and the inside of the roller 66 is arranged with fins to enhance convective heat transfer. One end of the roller 66 is connected to the hot air inlet of the first drying chamber 91 through the hot air circulation pipe 72, and the other end is the hot air outlet. The hot air is introduced from the exhaust port of the second drying chamber 92; the hot air after heat exchange is discharged from the other end of the roller 66, and part of the discharged hot air is mixed with fresh air in a certain proportion and then enters the heat exchanger 3 for heating, and then puts it into the during the next drying cycle. The twin-roller press 6 is used to roll wet pulp (dryness is about 3%), so that part of the moisture in the pulp can be removed, and the dryness of the pulp after rolling is about 50%. Different from the commonly used squeezers in the existing industry, the squeezer of this equipment adds a hot rolling mechanism mainly composed of a hot rolling tube 66 to utilize the heat energy of the humid hot air after drying. Conduct contact heat transfer to the pulp board to increase its temperature, which is convenient for later heating and drying.

As shown in Figure 7A and Figure 7B, the air preheater 4 is a rotary air preheater, which consists of a housing 41, a central rotor 42, and a bracket 43, and the central rotor 42 is rotatably mounted on the outer shell Inside the body 41, the casing 41 plays the role of external sealing and gas flow guide, and the central rotor 42 plays the role of a heat exchanger. Corresponding positions above and below the central rotor 42 are respectively divided into a flue gas circulation area, an air circulation area and a sealing area, while the outer shell 41 forms a primary air chamber, a secondary air chamber and a smoke chamber within a certain range of these areas. . The primary and secondary air bins form the cold air side, and the flue gas bins form the hot air side. The upper and lower ends of each warehouse body are respectively formed with respective gas flow passages by the outer casing and the air duct.

As shown in Figure 5, it is a sequence diagram of hot air flowing through each device. After the fresh air is mixed with a certain proportion (quantity) of humid hot air, it enters the air preheater 4 for preheating, and the preheated air enters the air-heat transfer oil heat exchanger 3 for heating, and the hot air coming out of the heat exchanger 3 (wind) is divided into two streams, one directly enters the first drying chamber to dry the pulp at a uniform speed; the other stream mixes with the hot air discharged from the first drying chamber and then enters the second drying chamber to dry the pulp at a reduced speed; Two strands of hot air converge in the hot blast circulation duct 73 places.

As shown in Fig. 3A and Fig. 3B, the hot air circulation system of the present invention is composed of a blower, an air supply pipe, an induced draft fan, hot air circulation pipes 71, 72, 73 and valves. The blower is used to deliver fresh air to the air preheater 4; the blower is used to provide heated air to the drying chamber; the hot air circulation pipes 71, 72, 73 and valves are used for the delivery of hot air and the adjustment of the air volume. Control; the induced draft fan is used to get rid of the humid air with high moisture content in the drying system.

The control system adopts semi-automatic operation and is manually set to control the normal operation of the whole set of equipment: mainly control the operation of small heat transfer oil boilers; control the microwave radiation intensity and radiation time of the microwave generation system; control the hot air temperature of the hot air circulation system , Hot air speed; control the material delivery direction and speed of the material delivery system and other parameters.

Working principle of the present invention:

As shown in Figure 3A and Figure 3B, after the wet thin pulp is squeezed into a pulp plate by the twin-roller presser 6, it enters the hot rolling device mainly composed of the hot rolling tube 66, and the pulp is aligned by the hot rolling device. The plate conducts contact heat transfer, and the heat energy of the hot rolling device comes from the residual heat contained in the humid air discharged from the system. The heated pulp board is sent into the second drying chamber 92, and is dried at a constant speed by hot air on the conveyor belt until the pulp reaches its critical moisture content point. When the uniform drying of the pulp is about to end and the deceleration drying is about to start, the microwave drying of the microwave generator 5 is coupled to the drying chamber 9, and microwaves are used to heat the moisture inside the pulp to evaporate the moisture inside the pulp, thereby greatly increasing the drying speed , to reduce the heating energy consumption of pulp. In the first drying chamber 91, the hot air with higher temperature and higher dryness decelerates the pulp to dry it, so that the dryness of the pulp finally meets the production requirements. Finally, the pulp sheet is cut by the pulp cutting mechanism 2 at the exit of the drying chamber 9, so that the produced dry pulp sheets have consistent dimensions.

The above is only a preferred implementation case of the present invention, and there are many ways to arrange the pipelines, so the scope of the present invention cannot be limited with this, that is, the equivalents made according to the patent scope of the present invention and the content of the specification Changes and modifications should still fall within the scope covered by the patent of the present invention.

Claims (6)

1. an energy-efficient dewatering of pulp drying equipment, is characterized in that: it comprises frame, paper pulp cutting mechanism, heat exchanger, air preheater, microwave generator, Var-nip press, hot air circulating pipe, material transport system, hothouse, heat conducting oil boiler; Frame is provided with Var-nip press, hothouse, heat exchanger, paper pulp cutting mechanism from left to right successively, heat conducting oil boiler to be arranged in frame and to be positioned at the below of hothouse, microwave generator to be arranged in frame and to be positioned at the top of hothouse, wherein, Var-nip press is positioned at the starting end of hothouse and docks with the material transport system of hothouse; Paper pulp cutting mechanism is positioned at the end of hothouse, and paper pulp cutting mechanism is docked with the material transport system in hothouse by hot air circulating pipe, and described heat exchanger is connected with heat conducting oil boiler, hothouse, air preheater respectively.

2. energy-efficient dewatering of pulp drying equipment according to claim 1, it is characterized in that: described hothouse is divided into two sections, it is made up of the first hothouse and secondary drying chamber; First hothouse and secondary drying chamber are mutually connected and are arranged on the middle part of frame, and Two stage dryer separates with dividing plate between room, are communicated with between the first hothouse and secondary drying chamber by hot air circulating pipe; Material transport system is separately installed with in the first hothouse and secondary drying chamber.

3. energy-efficient dewatering of pulp drying equipment according to claim 2, it is characterized in that: described microwave generator to be arranged between the first hothouse and secondary drying chamber and to be positioned at the top of hothouse, the end of the microwave action that microwave generator produces in the first hothouse and the initiating terminal of secondary drying chamber.

4. energy-efficient dewatering of pulp drying equipment according to claim 1, it is characterized in that: described heat exchanger is air-heat-condutive oil heat exchanger, the body of heat exchanger is provided with conduction oil entrance and exit, hot-wind inlet and hot-blast outlet; Described conduction oil entrance is connected with heat conducting oil boiler, and conduction oil is from heat conducting oil boiler; Hot-blast outlet leads to hothouse by hot air circulating pipe, and hot-wind inlet is connected with air preheater, utilizes the high-temperature flue gas of boiler to carry out preheating to improve energy utilization rate to fresh air.

5. energy-efficient dewatering of pulp drying equipment according to claim 1, is characterized in that: described Var-nip press comprises hopper, roll-in case, the first conveyer belt, roll-in cylinder, the second conveyer belt, hot-rolling pressure pipe; Described hopper is arranged on the porch of roll-in case and the outlet of hopper is relative with the first conveyer belt be arranged in roll-in case, the output of the first conveyer belt and the input of the second conveyer belt are connected with two roll-in cylinder inputs and output respectively, the input of the hot-rolling pressure pipe that output and some rows of the second conveyer belt are arranged symmetrically with is connected, this hot-rolling pressure pipe is hollow roller, roller inner is furnished with the fin strengthening convection heat transfer' heat-transfer by convection, roller one end is connected with hothouse hot-wind inlet by hot air circulating pipe, and the other end is hot-blast outlet.

6. energy-efficient dewatering of pulp drying equipment according to claim 1, it is characterized in that: described air preheater is made up of housing and center rotor, in the rotatable housing mounted externally of center rotor, housing plays the effect of outside seal and gas flow guiding, and center rotor plays the effect of heat exchanger.