CN113280579B

CN113280579B - Method for evaporating wood by utilizing evaporating furnace

Info

Publication number: CN113280579B
Application number: CN202110592611.XA
Authority: CN
Inventors: 寇宗辉
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-05-28
Filing date: 2021-05-28
Publication date: 2023-08-22
Anticipated expiration: 2041-05-28
Also published as: CN113280579A

Abstract

The application relates to the technical field of wood processing, and discloses a method for evaporating wood by using an evaporating furnace. The method comprises the following steps of S1: placing the wood to be evaporated to dryness into an evaporation furnace, and injecting water into a water tank; s2: heating the water in the water tank into water vapor in the furnace by utilizing microwaves; s3: heating the water vapor in the furnace to a first set temperature; s4: reducing the water vapor in the furnace to a second preset temperature which is 3-5 ℃ lower than the first preset temperature; s5: raising the temperature of the steam in the furnace to the first set temperature again; repeating the steps S4 and S5 until the wood in the furnace is evaporated to the required water content. According to the method, only steam is used as a heating carrier, the wood is directly heated without a dry heat source, wood fibers can be steamed, deformation and expansion of the wood in a drying process are avoided, resin and mineral substances in the wood fibers and the wood are not damaged, and the toughness of the wood is ensured.

Description

Method for evaporating wood by utilizing evaporating furnace

Technical Field

The application relates to the technical field of wood processing, in particular to a method for evaporating wood by using an evaporating furnace.

Background

The stability of wood is an important indicator of wood quality, the main reason for the instability of wood being due to the retractility of the green, original wood fibers: the wood fiber loses own moisture and contracts, and absorbs moisture in a humid environment and stretches. The resin and mineral substances in the wood not only increase the density and toughness of the wood, but also solidify or crystallize during the drying process, so that the stability of the wood can be increased. Therefore, before deep processing of the wood, the wood fiber needs to be cured, the moisture in the wood fiber is reduced, and the wood fiber, the resin and the mineral substances in the wood cannot be damaged, so that the stability of the wood is improved, the toughness of the wood is prevented from being damaged, and the wood finished product cannot deform, crack and the like in later use.

At present, the existing wood drying is a method for drying wood by adopting a dry heat source, specifically, the wood in a drying furnace is directly heated and dried by heat source radiation and hot air convection, or the wood is directly radiated by microwave to heat and dry the inside of the wood, and the dry heat source drying method has a plurality of problems:

1) Surface cracking, namely, the surface of the wood is quickly dried by dry heat drying, the surface-dried part is rapidly contracted, and the moisture in the wood is expanded after being heated, so that opposite forces inside and outside the wood are generated, and the surface cracking of the wood is caused;

2) The internal cracking, the dry heat drying can quickly solidify or crystallize the resin in the wood before the wood fiber is cured, the solidified or crystallized resin can block the water path in the wood, and the internal moisture expands extremely after the wood is heated, so that the wood is propped and cracked, thereby causing the internal cracking of the wood.

3) The drying temperature is difficult to control, if the drying temperature is controlled within 80 ℃, the drying temperature is insufficient to cure the wood fibers, and if the drying temperature exceeds 80 ℃, the wood fibers are embrittled and the resin and mineral substances are damaged, so that the toughness of the wood fibers is damaged, and the phenomena of surface cracking and internal cracking are more serious.

Although the prior art also has the method of introducing steam into the furnace in the process of directly heating and drying the wood by using a dry heat source, the effect of the steam is only used for maintaining the environment in the furnace at a certain humidity, so that the difference of the water content inside and outside the wood is reduced, the heating uniformity can be improved to a certain extent, the deformation of the wood is reduced, but the steam is not used as a main heat source for heating the wood, the steam is insufficient for steaming the wood fibers, and the heating mode is still that the dry heat source is used for drying the wood basically: namely, the wood is directly heated by high-temperature dry heat source radiation and hot air convection or microwave radiation, and the problems of surface cracking, internal cracking and damage to wood fibers and internal beneficial components can not be solved.

Disclosure of Invention

Aiming at the problems in the prior art, the application aims to provide a microwave timber steaming method which simply relies on steam as a heat source to dry timber, and the timber fiber is steamed before drying, so that the timber is prevented from deforming or expanding even in the drying process, the timber fiber, the resin and mineral substances in the timber are not damaged, and the toughness of the timber is ensured.

In order to achieve the above purpose, the application adopts the following technical scheme:

a method for evaporating wood by using an evaporating furnace, wherein the evaporating furnace comprises a furnace body, a microwave assembly, a mesh type microwave shielding device and a water tank, the water tank and the mesh type microwave shielding device are arranged in the furnace body, a water draining exhaust port is arranged at the bottom of the furnace body, and the mesh type microwave shielding device is used for blocking the wood in the microwave direct radiation furnace, and the method comprises the following steps:

s1: placing the wood to be evaporated to dryness into the furnace body, and injecting water into the water tank;

s2: starting the microwave assembly, and heating and evaporating all water in the water tank into water vapor in the furnace by utilizing microwaves;

s3: the microwave assembly continues to heat the steam in the furnace, so that the temperature of the steam in the furnace is gradually increased to a first preset temperature, and in the heating process, the steam in the furnace heats wood in the furnace, so that wood fibers are steamed and part of moisture in the wood is heated to the steam in the wood at the first preset temperature;

s4: reducing the power of the microwave component, reducing the temperature of the steam in the furnace to a second preset temperature which is 3-5 ℃ lower than the first preset temperature, condensing part of the steam in the furnace in the temperature reduction process, discharging the condensed water from the water discharge exhaust port, and releasing the steam in the wood into the furnace from the wood;

s5: the power of the microwave component is increased, the temperature of the steam in the furnace is increased to the first set temperature again, in the heating process, the steam in the furnace is heated and expanded, part of the steam is discharged from the water discharge and exhaust port, the residual steam in the furnace heats the wood in the furnace again, and part of the residual moisture in the wood is heated to the steam in the wood with the first set temperature;

repeating the steps S4 and S5, and carrying out a plurality of cooling and heating processes until the wood materials in the furnace are evaporated to the required water content.

Preferably, the furnace body is provided with a through hole, the microwave assembly comprises a microwave generator, a waveguide tube and a waveguide plate, the microwave generator is arranged outside the furnace body, one end of the waveguide tube is communicated with the microwave generator, the other end of the waveguide tube penetrates through the through hole and stretches into the furnace body, and the waveguide plate is connected to the other end of the waveguide tube.

Preferably, the first set temperature is 70-120 ℃.

Preferably, a weighing device is arranged at the bottom of the steam dryer.

Preferably, an electric controller is further arranged on the outer side of the steaming drying furnace, and the electric controller is in communication connection with the microwave assembly.

The application utilizes the saturated steam generated by microwave once and the unsaturated steam generated after the steam is continuously heated to heat the wood, the moisture in the wood is discharged in the form of saturated steam after the temperature is reduced, and the partial steam discharged from the wood is used as a heating carrier for continuously evaporating the wood. The microwave wood steaming method has the following beneficial effects:

1. the timber steaming method overcomes the prejudice of the prior art, and the prior art considers that the timber is not directly heated by a dry heat source, and only water vapor is used as a carrier for directly heating the timber, but the water vapor moistens the timber, so that the timber cannot be dried forever. The application skillfully utilizes the multiple alternating processes of temperature rise, temperature reduction and temperature rise, water in the wood is heated into water vapor through the water vapor, then the furnace temperature is reduced to release the water vapor in the wood into the furnace, and then the furnace temperature is raised to expand and discharge the water vapor in the furnace, thereby realizing continuous evaporation, release and discharge of the water in the wood outside the furnace, and finally reaching the drying requirement.

2. According to the application, the wood fibers are steamed by high-temperature steam, so that the high-temperature damp heat can not only be used for curing the wood fibers and eliminating the activity and internal stress of the wood fibers, but also be used for avoiding the telescoping of the wood fibers in the subsequent drying and using processes, and the problem of embrittlement of the wood fibers caused by high-temperature dry heat curing can be avoided.

3. According to the application, the wood is heated by high-temperature steam, so that wood fibers can be steamed and cured gradually from outside to inside, and meanwhile, resin in the wood can be softened, so that a moisture passage in the wood is opened, the water vapor in the wood is discharged, and the wood is prevented from being expanded by the steam in the wood; and the steam heating does not destroy beneficial components such as resin in the wood.

4. According to the application, part of water vapor released from the wood is skillfully utilized as a heating carrier for subsequent heating and evaporating the wood, so that only primary water is injected into the water tank at first and the water in the water tank is completely evaporated at one time by microwave, no new water is needed to be added into the water tank in the subsequent step, and no new steam is needed to be continuously introduced into the furnace, and the whole process is simple, continuous and high in automation degree.

5. The application uses the cooling step to condense and discharge partial water vapor in the furnace, uses the reheating step to expand and discharge more residual vapor rapidly, does not need to arrange a special exhaust device such as an exhaust fan, and saves the cost.

6. The application adopts the mesh microwave shielding device to shield microwaves, the design is very ingenious, the free entry and exit of water vapor into the microwave shielding device can be facilitated, the microwave assembly can continuously heat the steam generated by the water tank and the steam released by the wood in the whole process of steaming, and the direct radiation of the microwaves to the wood can be avoided to damage the structure of the wood. In the prior art, the microwave assembly is arranged outside the furnace, but a microwave shielding device is not arranged in the furnace, in the design, microwaves directly radiate wood, the temperature in the wood can be rapidly increased, and the wood is easy to crack and carbonize.

Detailed Description

The present application will be described in further detail with reference to examples. It is to be understood that the specific embodiments described herein are merely illustrative of the application and are not limiting thereof.

In the description of the present application, unless explicitly stated and limited otherwise, the terms "connected," "connected," and "fixed" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements or interaction relationship between the two elements. The specific meaning of the above terms in the present application will be understood in specific cases by those of ordinary skill in the art.

In the present application, unless expressly stated or limited otherwise, a first feature "above" or "below" a second feature may include both the first and second features being in direct contact, as well as the first and second features not being in direct contact but being in contact with each other through additional features therebetween. Moreover, a first feature being "above," "over" and "on" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature is higher in level than the second feature. The first feature being "under", "below" and "beneath" the second feature includes the first feature being directly under and obliquely below the second feature, or simply indicates that the first feature is at a lesser level than the second feature.

In the description of the present embodiment, the terms "upper," "lower," "left," "right," and the like are merely for convenience of description and simplicity of operation, and do not indicate or imply that the devices or elements in question must have a particular orientation, be constructed and operated in a particular orientation, and thus are not to be construed as limiting the application. Furthermore, the terms "first," "second," and the like, are used merely for distinguishing between descriptions and not for distinguishing between them.

The embodiment discloses a method for evaporating wood by utilizing an evaporating furnace, which is used for evaporating wood in an evaporating furnace, wherein the evaporating furnace comprises a furnace body, a microwave assembly, a mesh type microwave shielding device and a water tank, the water tank and the mesh type microwave shielding device are arranged in the furnace body, and a water draining and air exhausting port is arranged at the bottom of the furnace body. The water tank is used for injecting a certain amount of water at one time; the microwave component is used for generating microwaves to heat and evaporate water in the water tank and heat water vapor in the furnace body; the drainage and exhaust ports can be arranged in a plurality, and the drainage and exhaust functions are achieved. The mesh-type microwave shielding device is used for blocking the wood in the microwave direct radiation oven in the whole drying process.

Illustratively, the furnace body of the evaporating furnace is in a cuboid shape, a plurality of supports are arranged at the bottom of the furnace body, a wood entrance door is arranged at one side of the furnace body, and a water filling port is arranged at the other side of the furnace body; the inside heat preservation that is equipped with of furnace body, the wall of furnace body is provided with a plurality of through-hole, the microwave subassembly the number with the through-hole number is the same, and every microwave subassembly includes microwave generator, wave guide and waveguide board, and microwave generator sets up outside the furnace body, wave guide one end intercommunication microwave generator, the other end passes the through-hole stretches into the furnace body, the waveguide board connect in the wave guide other end. The mesh type microwave shield cover is arranged above the water tank and encloses a space together with the inner wall of the furnace body, the waveguide plate is positioned in the space, and the space is communicated with the main body space in the furnace body through meshes of the microwave shield. The specific use mode is as follows: the microwave generator outside the oven body generates microwaves, the microwaves are guided into the oven body through the waveguide tube, the waveguide plate is used for guiding the microwaves into the water tank, the water in the water tank can be heated into water vapor through the microwaves, the generated water vapor can enter the main body space in the oven body through the meshes, the water vapor in the main body space can also enter the surrounding space for heating, that is to say, the surrounding space can not influence heating of the water vapor inside and outside the surrounding space while preventing the microwaves from being emitted to directly radiate the wood in the oven through the microwave assembly, the water tank and the mesh type microwave shield. Of course, the above-described composition and structure of the steaming oven are only exemplary, and the steaming oven used in the present application may be entirely other alternatively implemented compositions and structures, as long as the microwave wood steaming method of the present application can be implemented.

The microwave timber steaming method specifically comprises the following steps:

s1: and (3) placing the wood to be evaporated to dryness into an evaporation furnace, and injecting water into the water tank.

Specifically, the timber to be evaporated can be loaded into a skip car, and the timber to be evaporated is loaded into the evaporation furnace through a timber access door at one side of the evaporation furnace body. Then, a certain amount of water is injected into the water tank in the evaporating furnace, and the specific required weight of the injected water is related to the weight of the loaded wood.

S2: and starting the microwave assembly, and heating and evaporating all water in the water tank into water vapor in the furnace by utilizing microwaves.

Preferably, an electric controller is further arranged on the outer side of the drying oven, the electric controller is in communication connection with the microwave assembly, and the microwave assembly can be opened and closed through operation of the electric controller, and the power of the microwave assembly can be adjusted. Specifically, the electric controller is operated to start the microwave assembly, and the water in the water tank is heated into water vapor in the furnace by microwaves at one time. It is noted that by the arrangement of the microwave shield, the microwave assembly in this embodiment is capable of radiation heating of water in the water tank and water vapor in the oven, but not directly radiating the wood itself in the oven.

S3: the microwave assembly continues to heat the steam in the furnace, so that the temperature of the steam in the furnace is gradually increased to a first preset temperature, and in the heating process, the steam in the furnace heats wood in the furnace, so that wood fibers are steamed and part of moisture in the wood is heated to the steam in the wood at the first preset temperature.

After all the water in the water tank is evaporated into water vapor, the microwaves of the microwave assembly continue to heat the water vapor in the furnace until the water vapor is heated to the high-temperature unsaturated water vapor with the first set temperature, and the heating process is gradual and relatively slow, and takes more than 10 hours to raise the temperature in the furnace to the first preset temperature. In the gradual heating process, the high-temperature steam in the furnace heats the wood in the furnace from outside to inside, gradually evaporates and cures the wood fibers and softens the resin in the wood, simultaneously heats the moisture in the wood, and evaporates part of the moisture into the steam in the wood, and the steam in the wood is continuously heated until the steam and the furnace temperature reach a first preset temperature together. The first preset temperature is in particular dependent on the type of wood to be dried, and preferably ranges from 70 to 120 ℃. On one hand, the steam in the temperature range can enable the steam to reach an unsaturated state, and is also sufficient for gradually and completely steaming and ripening wood fibers from outside to inside, and simultaneously, the resin in the wood is softened, so that a moisture passage in the wood is opened, the steam in the wood is discharged, and the wood is prevented from being expanded by the steam in the wood; on the other hand, the water vapor temperature in this temperature range is not so high as to destroy the useful components such as wood fibers and resins, minerals and the like in the wood.

S4: and (3) reducing the power of the microwave assembly, reducing the temperature of the steam in the furnace to a second preset temperature which is 3-5 ℃ lower than the first preset temperature, and in the cooling process, part of the steam in the furnace is condensed, the condensed water is discharged from the water discharge exhaust port, and the steam in the wood is released into the furnace from the wood.

And reducing the power of the microwave assembly by operating the electric controller, and reducing the temperature of the water vapor in the furnace to a second preset temperature which is 3-5 ℃ lower than the first preset temperature. In the process, on one hand, the temperature in the furnace is firstly reduced, so that partial water vapor in the furnace can be condensed, the humidity in the furnace is reduced, and the condensed water is discharged out of the furnace from a water discharge and exhaust port of the furnace bottom. On the other hand, the temperature of the water vapor in the wood does not immediately decrease, and the temperature thereof is still higher than the temperature of the water vapor in the furnace, so that the water vapor in the wood in turn heats the water vapor in the furnace, while the water vapor in the wood can be released from the wood into the furnace in the form of relatively saturated water vapor. That is, part of the moisture in the wood is evaporated to the outside of the wood, and the wood is partially evaporated.

S5: and (3) increasing the power of the microwave assembly, and increasing the temperature of the steam in the furnace to the first set temperature again, wherein in the heating process, the steam in the furnace is heated and rapidly expands, part of the steam is discharged from the water discharge exhaust port, the residual steam in the furnace heats the wood in the furnace again, and part of the residual moisture in the wood is heated to the steam in the wood with the first set temperature.

The electric controller is operated to increase the power of the microwave component, the temperature of the steam in the oven is increased to the first set temperature again by utilizing microwaves, and in the process, on one hand, the steam in the oven (which contains the steam released from the wood at the moment) is heated and rapidly expanded, and part of redundant steam in the oven is discharged to the outside of the oven from a water discharge outlet at the bottom of the evaporating oven; on the other hand, part of water vapor still remains in the furnace, and the residual water vapor in the furnace is changed into high-temperature unsaturated water vapor again, so that part of the residual water in the wood is heated into the water vapor in the wood with the first preset temperature as a new heating carrier, and the wood is heated and evaporated to dryness for a new round.

Repeating the steps S4 and S5, and carrying out a plurality of cooling and heating processes until the wood materials in the furnace are evaporated to the required water content. Through repeated cooling and heating operations, the redundant moisture in the wood is gradually released into the furnace in the form of saturated steam, and then part of steam in the furnace is rapidly expanded and discharged out of the furnace, so that after a plurality of steaming and drying cycles are performed, when the moisture content of the wood in the furnace is detected to reach the steaming and drying requirement, an electric controller can be operated to close a microwave assembly, and after the temperature in the furnace is reduced to a preset temperature (such as room temperature), the furnace door is opened, and the wood is taken out. As to how to judge whether the wood in the furnace reaches the required moisture content, there are various conventional mature detection judging modes in the art. The embodiment is preferably a weight comparison method, and the specific method is that a weighing device is arranged at the bottom of the steaming furnace, for example, the whole furnace body is placed on a scale, and the scale can display the total weight of the steaming furnace and the wood placed in the steaming furnace. The water content of the timber in the evaporating process is gradually released and discharged out of the furnace, the reading of the weighing device is gradually reduced, and the reading is in one-to-one correspondence with the water content of the timber. Thus, when its reading is reduced to a preset weight, the wood is considered to be evaporated to a preset desired moisture content.

Note that the above is only a preferred embodiment of the present application and the technical principle applied. It will be understood by those skilled in the art that the present application is not limited to the particular embodiments described herein, but is capable of numerous obvious changes, rearrangements and substitutions without departing from the scope of the present application. Therefore, while the application has been described in connection with the above embodiments, the application is not limited to the embodiments, but may be embodied in many other equivalent forms without departing from the spirit or scope of the application, which is set forth in the following claims.

Claims

1. The method for evaporating wood by using the evaporating furnace is characterized in that the evaporating furnace comprises a furnace body, a microwave assembly, a mesh type microwave shielding device and a water tank, wherein the water tank and the mesh type microwave shielding device are arranged in the furnace body, a water draining exhaust port is arranged at the bottom of the furnace body, and the mesh type microwave shielding device is used for blocking the wood in the microwave direct radiation furnace, and the method comprises the following steps:

s2: starting the microwave assembly, and heating and evaporating the water in the water tank into water vapor in the furnace by microwaves at one time;

s3: the microwave assembly continuously heats the steam in the furnace to gradually increase the temperature of the steam in the furnace to 120 ℃ which is the first preset temperature, and the steam in the furnace reaches an unsaturated state;

s4: reducing the power of the microwave assembly, reducing the temperature of the steam in the furnace to a second preset temperature which is 3-5 ℃ lower than the first preset temperature, condensing part of the steam in the furnace in the temperature reduction process, discharging the condensed water from the water discharge exhaust port, and releasing the steam in the wood into the furnace from the wood;

s5: the power of the microwave component is increased, the temperature of the steam in the furnace is increased to the first preset temperature again, in the heating process, the steam in the furnace is heated and expanded, part of the steam is discharged from the water discharge and exhaust port, the residual steam in the furnace heats the wood in the furnace again, and part of the residual moisture in the wood is heated to the steam in the wood with the first preset temperature;

2. The method for drying wood by steaming furnace according to claim 1, wherein the furnace body is provided with a through hole, the microwave assembly comprises a microwave generator, a waveguide tube and a waveguide plate, the microwave generator is arranged outside the furnace body, one end of the waveguide tube is communicated with the microwave generator, the other end of the waveguide tube penetrates through the through hole and stretches into the furnace body, and the waveguide plate is connected with the other end of the waveguide tube.

3. The method for drying wood using a drying oven according to claim 2, wherein a weighing device is provided at the bottom of the drying oven.

4. A method of drying wood using a drying oven according to any one of claims 1 to 3, wherein an electrical control is further provided outside the drying oven, said electrical control being in communication with said microwave assembly.