DE1941938A1 - Pneumatic-hydrothermal drying and firing - of ceramic prods and silicate building mat-erials - Google Patents

Abstract

The raw products are simultaneously dried and fired in an electrically heated, gas-tight unit. The charge-firing material is first heated without appreciable dehydration to 1-160 degrees C and then dried with vapour temps. of 1-200 degrees C and water vapour partial pressures of 0.1-6 atm. The material thus dried is heated to 550-950 degrees C at water vapour partial pressures of 0.1-6 atm. While this temp. is maintained final firing takes place, followed by cooling the firing material and unit. The water vapour escaping from the charge or firing material during the entire combined process is utilized as a drying medium in the drying phase and as a decisive parameter in the firing phase. This is effected by using fans to force the vapour, under an excess pressure of 0.1-6 atm. in the gas-tight apparatus, through the charge-firing material, formed as a hollow product, to generate convective heat and material transfer.

Description

Process and device for pheumatic-hydrothermal drying and firing ceramic goods, silicate building materials and the like.

The invention relates to a method and a device for pheumatic-hydrothermal Drying and firing of ceramic goods, silicate building materials and the like in one self-contained work process.

It is known that by hot steam drying compared to hot air drying the time required for drying can be reduced. Usually will for superheated steam drying under normal pressure and when superheated steam is purchased externally, the technical one Effort so great that drying ceramic goods after this process is economical is not portable. Furthermore, the hot steam drying of ceramic goods is used usually a hot deformation in advance and thus restrictions of the use ceramic raw materials required.

Furthermore, the drying and firing process of ceramic moldings has been used so far Carried out spatially and temporally separately. Burning in a steam enriched The atmosphere is to accelerate the burning process from the ceramic Known in practice. It has already been suggested that water vapor be essential Firing parameters for generating new material properties in ceramic goods to use.

During this pneumatic-hydrothermal burning under the influence, water vapor, which is predominantly at overpressure compared to the atmosphere, occurs for hydrothermal synthesis of partly new mineral societies in z. B. ceramic shards.

Through the usual separation of the drying and firing processes there are very long treatment times in the individual technological sections, the unfavorable thermal conditions in the entire process and to one labor-intensive effort in the production of, for example, masonry bricks, roof tiles and other ceramic materials.

The purpose of the invention is to achieve a technological redeployment of the Drying and burning process and thus an increase in throughput and a Improvement of the thermal economy as well as an optimal adaptation of the overall process to achieve the conditions of mechanization and automation.

The invention is based on the task of drying and firing preferably ceramic products using predominantly hydrothermal syntheses in the supercritical temperature range of water vapor in a self-contained To carry out the work process within an electrically heated unit.

According to the invention, the object is achieved in that the to be treated, predominantly moist goods, with Exposure to suitable stability brought into the electrically heated facility on basket trolleys and there gradually is heated to a temperature of about 1 - 160 ° C. The escaping water vapor builds up an atmosphere containing water vapor over the property, the total pressure of which is above their temperature can be regulated. According to a specified temperature-time program after completion of the drying process gradually transferred to the firing process. The atmosphere, which contains a lot of water vapor, is heated up to the required cooking temperature, which is between 550 and 950 ° C, preferably at 750 ° C, maintained. The necessary one Water vapor partial pressure of 0.1 - 6 at is achieved by setting Gas overflow valves specified.

The method is carried out in a device according to the invention consists of a pressure chamber that is open on one side and through a gas-tight closure device can be closed.

Inside the pressure jacket, which is covered with a heat-insulating. layer is provided, there are electrical heating conductors, fans and gas overflow valves on the pressure jacket arranged.

The interior of the device is designed so that the to be treated Good, stacked on appropriately designed insertion devices, brought in and out can be.

The invention is to be described in more detail below using an exemplary embodiment explained. In the accompanying drawing show: the 1: the cross-section of the direction of FIG. 2: the longitudinal section of the device i <1ig. 3: a temperature-time program of the combined dry-firing process.

The device according to the invention consists of a gas-tight pressure jacket 1, the one with a heat insulating layer 2 and gas overflow valves 3 3 for regulation the water vapor-gas overpressure is provided in the device. This pressurized container receives a gas-tight closure device 4 at the front. The heat is supplied by electrical energy via electrical heating conductors 5, which are on the inner wall of the are attached. Heat transfer conditions are established via fans designed to be controllable within the overpressure container by means of forced convection, in which the water vapor-gas mixture for heat dissipation through cavities in or between the load 7 stacked aui 'basket trolley and then to absorb heat is forced past the electrical heating conductors 5. Through the ventilator nose an external gas (e.g. 3rd Itilluft) for e.g. forced cooling in the pressure vessel are introduced. The device works discontinuously, preferably in the interconnection of several ovens to form a battery.

The material to be fired 7 is stacked on basket trolleys 8 which are designed to be gas-permeable and for treatment according to the method according to the invention in the facility brought in. According to the temperature-time program shown in FIG. 3, the Equipment with damp, e.g.

50 ° C hot brick blanks occupied and over the gas-tight closure device 4 sealed gas-tight.

ground the gas overflow valves 3 to an internal gas pressure of, for example 2 at is set, it builds up only slightly when the device is heated Dehydration from the moist charge 7 @ a water vapor partial pressure which results in the drying section a - b..Achieves the entire water vapor-gas pressure inside the device 2 at, the water vapor that continues to be produced flows via the gas overflow valves 3. As those inside the facility Framdgases, such as the air introduced during charging or the degassing pro products of the set good 7, with progressive drying compared to the water vapor content will be negligibly low at a product temperature of 120 0C in the furnace gas phase a water vapor pressure of 2 at, corresponding to the saturation vapor pressure of the water at 120 OC.

In the following drying section b - c, the supplied heat is used Evaporation of the water from the charge 7 is used up, the charge 7 almost isothermally dried and the resulting water vapor from the interior of the facility with a pressure of 2 at and a temperature that is, for example, only a little more than 120 ° C.

After this approximately isothermal drying phase ends b-c, in the drying section c-d, the residual water becomes as the product temperature rises driven out and after drying in the first firing section d-e the firing material 7 heated to 750 0C, for example. This in turn arises from the drainage the clay minerals water vapor of the in the same way as with the drying a - d from the facility is discharged.

The cooking firing in the firing section e - f then takes place at 2 atm Water vapor pressure inside the device and at, for example, 750 ° C. The cooling off of the material to be fired 7 takes place in the firing section f - g and can be heated by appropriate heating elements Dimensioning of the facility or accelerated by forced cooling.

The entire combined drying and firing process a-d; d-g becomes over the temperature of the water vapor-gas phase inside the device is controlled and / or regulated.

Claims (7)

Claims 1. Process for pneumatic-hydrothermal drying and firing of ceramics Goods, silicate building materials and the like., Characterized in that the to be treated, Mainly ceramic raw products, electrically heated in elraem, sealed gas-tight Unit dried simultaneously in a combined drying-firing process (a - g) and are burned1 in that the material to be used / to be burned (7) is initially without any noteworthy Dehydration heated to a temperature of 1 - 160 ° C (a-b) and then with steam temperatures is dried from 1-2oo 0C and water vapor partial pressures of 0.1 - 6 at (b-d) and then heating the material thus dried to a temperature between 550 - 950 ° C (d-e), under water vapor partial pressures of 0.1 - 6 atm and maintaining At this temperature the cooking takes place (e-f), which is used to cool the items to be fired (7) and unit, if necessary by forced cooling, is connected (f-g), with during of the entire combined process (a-g) that escapes from the material to be used or to be burned (7) Steam in the drying phase (a-d) as a drying agent and in the burning phase (d-g) is used as the decisive firing parameter in that it is within the gas-tight sealed device under an excess pressure of 0.1 - 6 atm by means of Fans (6) to generate a convective heat and mass transfer the inserted material (7), which is mainly designed as pile material, is pushed through and its mass is reduced in accordance with the overpressure to be maintained. 2. The method according to claim 1, characterized in that the entire Combined drying and firing process (a-d; d-g) exclusively via temperature the; water vapor gas phase inside the device controlled and / or regulated will. 3. The method according to claim 1 and 2, characterized in that water vapor also obtained from an external process and the drying / burning process via the gas overflow valves (3) or the fans (6) can be fed. 4. The method according to claim 1 to 3, characterized in that at the firing process (d-g) even without water-poor or anhydrous dried items previous drying process (a-d) and without the supply of steam from a External process, with the sole exploitation of the drainage of the clay minerals resulting water vapor takes place. 5. Device for performing the method according to claim 1 - 4, characterized in that inside a pressure jacket (1) on its inside is provided with a heat-insulating layer (2), electrical heating conductors (5) and one or more fans (6) and gas overflow valves on the pressure jacket (1) (3) are arranged and that a gas-tight closure device (4) is attached on one side is. 6. Device according to claim 5, characterized in that in the interior Gas-permeable formed Sorbwagen (8) with the input / fuel (7) and be applied. 7. Device according to claim 5 and 6, characterized in that several individual ovens can be configured to form a battery by interconnecting them.