RU2125217C1 - Process of drying organic and/or inorganic materials and device for realization of this process - Google Patents

Abstract

FIELD: method of drying various ground organic or inorganic materials (mainly, wastes) through conversion of part of liquid into fog acting as vapor or gas. SUBSTANCE: device has chamber with rotor inside it; rotor is provided with knives attached to it. Inner surface of this chamber is provided with stiffening ribs arranged in definite pattern. Chamber is provided with ultrasonic energy source or magnetic vibrator. method of drying organic and inorganic materials is based on use of ultrasonic energy or magnetic vibrations. Provision is also made for delivery of heat from external source. EFFECT: reduced power requirements. 11 cl, 8 dwg

Description

 The invention relates to a method for drying materials that are disclosed in the preamble of paragraph 1 of the patent 1. The invention also relates to a device for carrying out drying of materials that is disclosed in the preamble of paragraph 3 of a patent.

 Thus, this invention relates to a method for removing liquids (drying) from various ground organic and inorganic materials by converting a portion of the liquid into a mist, acting as steam or gas, thus preserving the heat of vaporization, significantly reducing the absorbed energy compared to pure vaporization of those the same liquids.

 In principle, all prior art techniques or processes related to the removal of liquids from such ground materials are based either on mechanical separation by centrifugation, precipitation, etc., or some other form of complete evaporation of the liquids from the material. The objective of this invention is to show a new way of removing liquids from materials described in the literature that are dried after some of the liquids have been removed using the above methods.

 The literature provides a number of different drying systems, mainly including various ways of supplying energy to materials in order to evaporate liquids. The rationale for this need for different methods is the type of material, particle size, type of fluid and no less, thermodynamic estimates of materials during the process.

 The simplest and most trivial type of drying is observed when drying laundered laundry outdoors. Here, clothes dry out under the influence of the sun and wind.

Among others, the prior art includes the following methods and processes:
rotary drying, when energy is supplied by means of a flame blown into the dryer - the so-called hot-air dryer, or by means of thermally conductive elements of various designs (pipes, plates, etc.) - the so-called oil or steam dryers;
a fluidized bed dryer, which usually consists of a vertical cylinder with a net or some other perforated plate at the bottom through which any heated gas is blown, heating the material and removing liquids by evaporation.

 In addition, there is an infrared dryer, where the energy is delivered in the form of infrared radiation, various types of tunnel kilns and the so-called "turbo dryers", where the material is dried in a vertical cylinder with the help of rotary fans and counterflow of hot air or some other heated gas.

 The processes, which are well known from prior technical experience, are described in detail in a number of manuals, such as the Perry's Chemical Engineering Handbook, used for drying for different purposes.

 The problem with all these methods is that the evaporation of liquids requires so much energy that the final product should usually have a significant selling price, far exceeding the cost of drying.

However, there are now a number of different mixtures of materials / liquids for which this is not so; nonetheless, it was very favorable, for various reasons, to dry them, especially for environmental reasons. Such material / liquid mixtures may, for example, include:
All types of dirt from urban plants.

 Ordinary sewage.

 Manure of livestock.

 All types of filtrates with centrifuges containing liquids.

Various biological and chemical fluids from
oil refining, timber processing and food industry, etc.

 Most of these materials differ in that they are usually considered waste, and thus are considered not worth the cost of the drying process by evaporation.

 The subject of this invention is to show a process or method of drying such materials using less energy-intensive than existing drying processes in which liquids are not evaporated but removed by converting a significant portion of these liquids into fog.

When evaporating a liquid, the energy demand is expressed by the following equation:
Q = m • C • dt [J],
where Q is the necessary energy in Joules;
m is the mass of liquid in kg;
C is the specific heat of the liquid in J / cal ^o ;
dt is the difference between the evaporation temperature and the initial temperature of the liquid.

When water is evaporated, the equation is often expressed as follows:
Q = m • dh = m (h ₂ - h ₁ ) + k [J],
where h ₂ is the vapor enthalpy at the evaporation temperature;
h ₁ is the enthalpy of water at the feed temperature, that is, the temperature of the water at which it is supplied to the process together with solids;
k is equal to the loss in the process.

Q = m • x _s • c _s • dt + m • x _v (h ₂ - h ₁ ) + k = m [x _s • c _s • dt + x _v (h ₂ - h ₁ )] + k [J ],
where x _s is the weight ratio of solids;
c _s is the specific heat of solids;
x _v is the weight ratio of water.

 If there are several different solids in the material, the equality is expanded for each solid ingredient with its corresponding weight ratio and specific heat.

Turning to typical waste from the wood processing industry, containing 30% fiber and 70% water, provided that dt = 100 - 20 = 80 ^o C, c _s = 1500 J / kg ^o C = 1.5 kJ / kg ^o C C , h ₂ = 2,676,000 J / kg ^o C = 2676 kJ / kg ^o C and h ₁ = 83,900 J / kg ^o C = 83.9 kJ / kg ^o C, energy consumption per kg will be Q = 1 [0.3 • 1.5 • 80 + 0.7 (2676 -83.9)] = 1.850 kJ / kg = 1850000 kJ / t = 514 kWh / t net weight.

 In addition to this, there will be losses during the process, which can vary from 10% to more than a few hundred percent. Energy consumption three times the estimated amount is not unusual.

If we now consider the energy needed to turn water into droplets of fog, the starting point should be the size of the droplets of fog, which is in the range from 0.1 to 10 microns. If we choose to use (0.01 + 10) / 2 = 5 μm as the average size, then one liter of water can form the number of droplets of fog expressed by the equation N = V / dV, where V is the volume of one liter of water = 100000 ³ μm ³ and dV is the volume of each droplet = d ³ π / 6.
From which
N = 100000 ³ • 6/5 ³ μm = 1.53 • 10 ¹³ .

Это по порядку значения примерно в 20000 раз меньше, чем энергия для чистого выпаривания воды.The energy required for the formation of these droplets can be taken equal to the energy of the surface tension of the entire surface between water and air. The surface tension of pure water is σ _v = 71.4 dyn / cm = 7140 dyn / m = 7140 dyn • m / m ² = 7140 • 10 ^-5 Nm / m ² = 7145 • 10 ^-5 J / m ² . The total surface of the droplets of fog is
A _total = N • d ² π = 1.53 • 10 ¹³ • (5 • 10 ^-6 ) ² π = 1200m ² .
Total energy is equal

This is in order of magnitude approximately 20,000 times less than the energy for pure evaporation of water.

 This phenomenon is currently used for devices such as so-called humidifiers. Earlier models were based on pure evaporation, in which a submersible electric heater was placed in a container for heating water to a boil and evaporation. In modern models, the immersion heater is replaced by a piezoelectric crystal vibrating at a frequency of about 20 kHz. When a drop of water hits the crystal, it breaks into millions of very small droplets of water, together forming a fog that moisturizes the air in the room at room temperature.

The frequency of the ultrasonic source necessary to achieve this is expressed by F.D. Smith (FD Smith) as
f = [1 / (2π)] / [{3π (P _o + 2σ / r)} / o] ^0.5 ,
where r represents the radius of the droplets;
μ is the specific heat of gas in droplets;
P _o is the external hydrostatic pressure;
o is the specific gravity (density) of the liquid;
σ is the surface tension at the interface between liquid and gas.

The equation refers to cavitation in a liquid when it is exposed to ultrasonic energy. Calculations for droplets of various sizes show that the frequency should be in the range from 10 ⁴ to 10 ⁶ Hz.

 The materials to be dried, however, are a heterogeneous mass. They may consist of a number of different materials, as well as liquids of one or more different types, although the predominant part will usually be water.

 It is well known that liquids in such mixtures can exist both in the form of a free mobile fluid, and in the form of a fluid bound by physical bonds in substances represented mainly by capillary forces. To overcome these forces during the normal drying process, the vapor pressure must overcome the capillary pressure, which increases in proportion to the decrease in the porous structure. In a typical drying process, this is achieved by drying the materials at a temperature such that the vapor pressure overcomes the capillary pressure. This will often require temperatures well above that which is strictly necessary for evaporation. Another aspect that affects purely thermal drying is that the thermodynamic values of materials change during the process. They are getting worse. This, in turn, must be compensated by higher temperatures and a larger heating surface, which leads to a higher cost of equipment and operation.

 In order to achieve the technical result of this invention - drying as a combination of fog formation and evaporation, the units supplying ultrasonic and thermal energy to the material should be able to supply it under turbulent conditions when all parts of the material are processed. By bringing the material into an extremely turbulent state, it is possible to obtain not only conditions with approximately constant thermodynamic parameters, but also prevent the material from sticking to the walls of the chamber in which the process takes place and the components from sticking together, which is the main problem with all other drying processes of the prior art.

To achieve the above conditions, the process involves the inclusion of the following elements:
A mixer is installed in a vertical or horizontal cylindrical container, driven by a rotating energy source - an electric motor or an internal combustion engine. A series of knives has been developed for the mixer, which, when the rotor rotates, are bent outward by centrifugal force.

 An inlet for the material to be dried, an outlet for dry material, and an opening for removing steam and fog are arranged on the process chamber itself.

To supply ultrasonic energy to a material in a turbulent flow, the following procedure can be applied:
On the inner side of the chamber for the process, stiffeners are created that extend along the length along the entire inner periphery of the chamber. The ribs are shaped so that they are approximately parallel to the blades where they pass the ribs. When a rotor with N blades on the blade rotates at n rpm, each rotation will create n • N pressure pulses between the rib and the knife, which are transmitted to the turbulent mass in the chamber. For example, with a diameter of 2 m and 179 ribs with 35 mm intervals, with 12 knives around a rotor rotating at a speed of 2500 rpm, pressure waves from each knife will be generated with a frequency of 179 • 2500/60 = 7458 pulses per second. These pressure waves will break the liquid and cause a substantial part of it to cavitate and form fog. In addition, heat from the knives will be generated as a result of internal friction in the mass and, additionally, by supplying heated air or other gas, for example, CO ₂ from an internal combustion engine. When these gases are added, the fog will cause an extremely low partial pressure to form during the process in the chamber to evaporate part of the liquid. The experiments showed that the partial pressure for the vapor will be so low that it will provide evaporation at 40-75 ^o C.

 Gases, fog and steam leaving the process chamber through the outlet can either be condensed or vented to the atmosphere, depending on the nature of the gases.

 Another way to increase the frequency and, in this way, mechanical effect on liquids, is to use the design of the knives in the form of adjustable forks, so that they are better tuned to the natural vibration during the passage of the ribs, thus contributing to the release of ultrasonic energy. As an alternative to the purely mechanical action on the adjustable forks, they can be excited by electromagnetic action using a magnetic vibrator mounted externally. It is designed to allow a magnetic field to pass through the wall of the process chamber by constructing said chamber from a non-magnetic material (such as stainless steel).

 A magnetic field will act on each of the knives designed as an element that vibrates at the same frequency as the magnetic field. An additional way to enhance the effect could be to place magnetically-strictive material on knives, such as terfonol, made from elements: iron, terbium, and dysprosium. Under the influence of a magnetic field, the alloy will expand by approximately 1–2%. This increase in volume can directly affect the knives and thus the material to be processed.

 Another way to create a strong ultrasonic field in the process chamber is to place the ribs on piezoelectric or magnetostrictive materials. When the correct impedance is established between the mass of the ribs, it will be possible to force the ribs to oscillate with any selected frequency in the practical range under consideration by a frequency modulator from the outside. At a frequency in the region of 20,000 Hz, no movement will be observed on the ribs, since they will vibrate approximately in the range of their elasticity.

 You can provide other ways of summing up vibrations, such as designing knives so that they make a sound similar to a whistle when moving in mass. This can be achieved simply and practically by designing the backs of the knives so that they create very strong turbulence behind the specified knives. In addition to imparting vibrations, turbulence will also create a lag vacuum, which will contribute to more efficient fogging and evaporation at low temperature.

 Experiments have shown that it is possible to reduce energy consumption to less than half of the theoretical energy consumption for drying, for example, wood fiber waste.

During the process, the following parameters are automatically adjusted:
process temperature
engine load
humidity of the dried material.

 In other words, the yield of dried material begins at the selected operating temperature and humidity. The resulting reduced engine load will cause the load to turn on until the load reaches the limit again. During loading, the temperature drops and kickback begins. With properly adjusted equipment, this will be continuous, so that loading will balance the output, i.e. output and loading will be continuous.

The process is shown in detail in the following drawings, where:
FIG. 1 shows a schematic view of a process.

 FIG. 2 shows a detail of a process chamber and a knife at the time of movement.

 FIG. 3 shows a detail of one of the knives designed as an adjustable fork.

 FIG. 4 shows the same plug pre-stressed by the magnetostrictive material terfonol with a vibrating magnetic field generator.

FIG. 5 shows a detail of a stiffener attached to a piezoelectric or magnetostrictive material
FIG. 6 shows a side view of an example embodiment of a 450 kW apparatus.

 FIG. 7 shows a front view of the same embodiment.

 FIG. 8 shows a top or bottom view of an embodiment.

 In FIG. 1 shows a chamber for carrying out the process 1 with a rotor 2 and knives 3, driven by the motor 4. The mass is fed into the chamber for carrying out the process using the feed conveyor 5 from the hopper 6. The feed conveyor is driven by the motor 7. The mass in the chamber for carrying out the process broken by knives 3 and exposed to ultrasonic energy or vibrations from knives and stiffeners 8. As additional energy, partly in the form of heated gas can be supplied from unit 9. Gases, fog and vapors leave the chamber for conducting process 1 through the outlet, through the ventilation channel with the impeller 11 and either into the open atmosphere or into the condenser. The dried material is guided through the outlet 12 through the rotary shutter 13.

 In FIG. 2 shows, as indicated, the detail of the chamber for carrying out the process and the knife at the time of movement.

 In FIG. Figure 3 shows a detail of one of the knives designed in the form of an adjustable fork.

 In FIG. 4 shows the same plug pre-stressed by the magnetostrictive material terfonol 14 with a vibrating magnetic field generator 15.

 In FIG. 5 shows a detail of a stiffener 4 connected to a piezoelectric or magnetostrictive material 20 that receives vibration energy through cables 21 and 22 from a generator 23.

 In FIG. 6, where reference numbers have the same meaning as in FIG. 1 also shows a screw conveyor 15 for solids and a rail mechanism 16 on which the structure is placed. It also shows the exhaust pipe 17 for exhaust gases and fog, which are discharged into the open atmosphere. The process control apparatus 18 is located at the end of the engine. The entire unit is integrated in a 20-foot (6.1 m) standard ISO 19 container.

 In FIG. 7 shows a front view of the same embodiment, including an exhaust outlet 10 for exhaust gases and fog, a ventilation duct with an impeller 11, and a feed conveyor 5 to the hopper 6. There are 4 transverse feed conveyors in the hopper, the sole function of which is to feed material to the feed conveyor 5.

Claims (11)

 1. Device for drying organic or inorganic materials or mixtures thereof containing one or more liquids, in which drying occurs by removing liquids or liquids from solid materials in the form of finely divided droplets in the form of a mist, including a chamber for carrying out the process with an inlet for the material , which must be dried, having an inner wall, characterized in that it contains a rotor, mounted rotatably around the axis of the chamber for the process, and the periphery of the rotor with an opposite inner wall of the chamber for carrying out the process, an annular gap is provided, the rotor is provided with peripheral vibrating rotor knives, and the inner wall of the chamber for carrying out the process has substantially axially mounted stiffening ribs, while the rotor knives provide material to the inlet during rotation and are folded outward to remove liquids or liquids from solids, the rotor blades are arranged substantially close to opposing ribs to provide while rotating fluid turbulence removed from the solids in the vibrating rotor blades provide vibration to the liquid mist.  2. The device according to claim 1, characterized in that each rotary knife is mounted rotatably on an axis parallel to the axis of rotation of the rotor.  3. The device according to claim 1, characterized in that the rotor knives have backs that create high turbulence, visible in the direction of rotation.  4. The device according to claim 1, characterized in that the rotary knives are made in the form of adjustable forks.  5. The device according to claim 1, characterized in that the magnetic vibrator is installed outside the inner wall of the chamber for carrying out the process, and the rotor knives are connected to magnetostrictive material.  6. The device according to claim 1, characterized in that the stiffeners are made in the form of vibrating elements.  7. The device according to claim 6, characterized in that the stiffeners are located on a piezoelectric ceramic or magnetostrictive material.  8. A method of drying organic or inorganic materials or mixtures thereof, containing liquid or liquids, comprising supplying material to a chamber for carrying out a process between rotor knives located at the periphery, the rotor rotating about the axis of the chamber for carrying out a process having an inner wall, characterized in that the inner wall of the chamber for carrying out the process is performed with essentially axially spaced stiffeners, the rotating rotor provides the material with the possibility of movement of its radial but outward about the axis of rotation and removal of the liquid or liquids from the material, and the vibrating rotor knives and opposing ribs provide the occurrence of vibrational forces and turbulence to affect the external fluid flow in order to form a fog.  9. The method according to claim 8, characterized in that it includes the supply of heated gas to the chamber for carrying out the process to provide additional energy for drying the material.  10. The method according to claim 8, characterized in that the material is waste.  11. The method according to p. 8, characterized in that to ensure vibration, the stiffeners are exposed to a magnetic vibrator mounted outside the chamber for carrying out the process.

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