JPH01189494A - Heating of fluid in fluidized bed of fine powder - Google Patents

Abstract

PURPOSE:To improve the efficiency of the heating and achieve stability of the operation by using as solid particles spherical particles with a specified weight mean diameter and specified bulk densities and controlling the upward flow of the fluidizing gas at specified superficial standard velocities in fluidized bed. CONSTITUTION:By introducing as solid particles forming a fluidized bed particles which are substantially spherical and have a weight mean diameter of 30-120mum and bulk densities in the range of 0.3-1.5g/cm<3> bubbles formed in the fluidized bed are rendered small in size, changes in static pressure of the fluidized bed are reduced, and a pronounced improvement can be achieved in smoothness and uniformity of the fluidized condition. Furthermore, the solid particles are so fine in size and light in weight that the fluidized condition can be satisfactory by controlling the upward flow of the fluidizing gas at 2-40cm/sec in terms of superficial standard velocity in fluidized bed. In a fluidized-bed heater 1, the fluidizing gas is supplied from a conduit 4 to the bottom of the apparatus, passed through a distributor 3, and blown into the fluidized bed 2. In the fluidized bed runs a conduit 6 through which a fluid to be heated flows, entering the bed at 6A and going out at 6B. The fluidized bed is heated by an electric heater 5 and at a constant temperature by automatic control of the heating.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Objectives of the Invention (1) The present invention relates to a method of heating a gaseous or liquid fluid using a fluidized bed, and in particular a heating method that is more efficient than conventional methods. This provides a stable and easy-to-use method.

E1: A fluidized bed in which solid particles are fluidized by a standing gas has a uniform temperature inside the bed and good heat conductivity, so it is possible to heat the object by directly feeding it into the fluidized bed. BACKGROUND ART Conventionally, a container having a heat transfer surface, for example, a metal tubular container, is placed in a fluidized bed and a fluid such as gas or liquid is passed through the container to indirectly heat the container.

In both cases, the heating of the fluidized bed itself.

Methods used include heating the wall of a fluidized bed or heating inserts using electricity or high-temperature liquid, or direct fluidization using high-temperature gas.

Conventionally, solid particles fluidized in a heating fluidized bed are relatively coarse particles with a weight average diameter of about 0.2 to 2 mm and a bulk density of about 1.3 to 4 g/cm'. Therefore, dense sand and iron powder have been used.

These coarse and dense solid particles have been exclusively used because they have the following characteristics: fewer particles are scattered by the fluidizing gas, the heat capacity of the fluidized bed is large, and the fluidized bed is thermally stable. However, in order to fluidize it, a relatively large amount of fluidizing gas is required.

This requires a large amount of blowing power and a large amount of heat loss due to the discharge of a large amount of high-temperature gas, and is likely to cause problems such as unstable operation due to poor flow conditions, equipment damage, and particle wear. There are problems such as:

An object of the present invention is to provide a fluid heating method using a fine powder fluidized bed that solves the above-mentioned problems and enables more efficient heating and stable operation.

Arrangement 1 of the Invention The method of heating a fluid using a fine powder fluidized bed according to the present invention includes a fluid container having a heat transfer surface in a heated fluidized bed in which solid particles are fluidized by a gas. In the method of installing and heating the fluid, solid particles with a weight average diameter of 30 to 120 pm are used.
, using substantially spherical particles with a bulk density of 0.3 to 1.5 g/(~3), and maintaining the rising speed of the fluidizing gas at 2 to 40 cm/sec based on the empty column of the fluidized bed. do.

The fluidized bed used in the present invention has a weight average diameter of 30 to 120 JLm as solid particles fluidized by gas.
, is characterized by the use of substantially spherical particles having a bulk density of 0.3 to 1.5 g/cm'.

Although such fine particles have been used in fluidized catalytic reactions in which catalysts are used in an ionic state, there is no example of their use in a fluidized bed for heating.

This is because the former uses fine catalyst particles because it is necessary to maintain close contact between the catalyst and the reaction gas, whereas for heat transfer purposes, they are scattered along with the fluidizing gas. This is because it has been common knowledge that coarse and dense solid particles with fewer particles, a larger heat capacity of the fluidized bed, and thermal stability are preferable.

In the present invention, as solid particles forming a fluidized bed,
1 quantity average diameter 30S120m, preferably 40-100m
ILm, bulk density 0.3-1.5 g/cm3. Preferably, by using substantially spherical particles of 0.4 to 1.2 g/am', bubbles generated in the fluidized bed are small, static pressure fluctuations in the fluidized bed are small, and an extremely smooth and uniform fluidized state can be obtained. It will be done.

In addition, since the solid particles are fine and light, the rising speed of the fluidizing gas is 2 to 40 cm/sec, usually 3 to 3 cm/sec, based on the empty column of the fluidized bed.
Good fluidity can be obtained even at 0 cm for 7 seconds.

In addition, because the solid particles are fine, the heat transfer coefficient between the fluidized bed and the heat transfer surface of the fluid container increases even if the rising speed of the fluidizing gas is reduced, so the temperature between the fluidized bed temperature and the surface of the fluid container increases. The difference is smaller than in the case of a conventional coarse particle fluidized bed, and it is excellent in maintaining a uniform temperature on the surface of the fluid container.

There are relatively few particles scattered with the gas because the linear velocity of the fluidizing gas is low, but the scattered particles are collected with a cyclone and returned to the fluidized bed, which reduces the loss of solid particles that form the fluidized bed. can be made substantially O.

The upper limit of the weight average diameter of the solid particles is set to 120 JLm because it is the upper limit at which a good fluid state can be obtained, and as the value becomes smaller, such as 100 gm or 704 m, the fluid state gradually becomes smoother and more uniform. Ru. Also, the lower limit value is 30Bm
This is because if the flow rate is lower than that, the smoothness and uniformity of the fluid state will deteriorate, and the amount of particles scattered along with the gas will increase.

The upper limit of the bulk density of solid particles is set at 1.5 g/cm' because it is the upper limit for obtaining a good fluid state, and the smaller the value is, the smoother and more uniform the fluid state becomes. . In addition, the lower limit value was set at 0゜3 g/cm' because the fluidity state is good even if it is lower than that, or the amount of particles scattered by the gas increases, or one particle becomes brittle and the fluid is in a state of poor flow. This is because it becomes powdery due to wear and cannot be put to practical use.

On the other hand, conventional fluid heating methods using fluidized beds use relatively coarse particles with an average particle size of about 0.2 to 2 mm and a bulk density of about 1.3 to 4 g/cm'. When sand or iron powder with a high density is used as fluidizing particles, the bubbles generated in the fluidized bed become large, the static pressure of the fluidized bed fluctuates greatly, and the fluidized state becomes non-uniform.

The particle shape of the solid particles used in the present invention is substantially spherical, so that the fluid state is smoothed and made uniform.
Furthermore, this has the advantage that wear on the equipment and particles can be significantly reduced.

Solid particles having the above-mentioned properties can usually be easily produced by a spray drying method, etc. 4. The solid particles used in the present invention must be stable at the operating temperature, and as such, Siliceous, alumina, silica
Inorganic materials such as alumina are produced industrially and are commercially available as fluidized catalysts and their supports. These particles are suitable for the present invention.

In order to sufficiently fluidize such solid particles, the rising speed (linear velocity) of the fluidizing gas must be set at 5 to 50% of the fluidization start speed.
It is necessary to make it 1O times or more, and the superficial reference gas velocity is 2 cm 7 seconds or more, preferably 3 cm
7 seconds are required.

Furthermore, if the rising speed of the fluidizing gas becomes too high, the amount of heat held by the gas discharged from the fluidized bed will increase, and the amount of particles scattered from the fluidized bed with the gas will also increase significantly, so it is normally 40 cm/sec. (vacant group 71'-) or less, and more preferably 30 cm/sec or less.

In order to effectively carry out the present invention, it is necessary to collect particles scattered with the gas and constantly return them to the fluidized bed. Fine particles whose terminal velocity is less than the fluidizing gas velocity will be scattered from the fluidized bed along with the gas, and if left as is, the amount of particles packed in the fluidized bed will decrease.

The flow state becomes non-uniform due to the reduction of fine particles. Therefore, in order to maintain a stable fluidized state, a mechanism is required to collect the scattered particles and constantly return them to the fluidized bed.

The means for collecting particles scattered with the gas and constantly returning them to the fluidized bed is not particularly limited, but it is convenient to use a cyclone or a bag filter, which are generally used to capture solid particles. In particular, a cyclone-despreg system is suitable for carrying out the present invention.

The means for heating the fluidized bed is not particularly limited; for example, there is a method of heating the outer wall surface of the fluidized bed or the heat transfer surface of an insert inserted into the fluidized bed using electricity, high-temperature fluid, or the like. The interpolation within the fluidized bed is positioned such that it does not significantly impede the fluidization of the solid particles. Alternatively, the amount of high-temperature fluidized gas may be increased or the fuel may be combusted within the fluidized bed.

The type of fluidizing gas is not particularly limited, but room temperature or preheated air, combustion gas, etc. are suitable.

The fluid container having a heat transfer surface only needs to have the heat transfer surface located within the fluidized bed.

The fluid to be heated may be allowed to flow continuously in the fluid container, or may be held in batches for a certain period of time without being allowed to flow, and then taken out.

Furthermore, the shape of the fluid container is not particularly limited;
When handling the fluid continuously, it is preferable to use a tubular shape, and when handling the fluid in one batch, it is preferable to use a tank shape. In either case, it is important to uniformly arrange the solid particles so as not to significantly impede the flow of the solid particles. In particular, in order to reduce the temperature difference between the heating surface and the fluid and prevent overheating of the fluid, it is desirable to flow the fluid through the tubular passage at a high velocity.

FIG. 1 is a diagram showing an example of an apparatus for implementing the present invention.

1 is a fluidized bed apparatus, in which fluidizing gas is supplied from a conduit 4 to the bottom of the fluidized bed and is injected into the fluidized bed 2 through a distribution plate 3. Within the fluidized bed there is a conduit 6 through which the fluid to be heated passes, the fluid entering through 6A and exiting through 6B. The fluidized bed is heated by an electric heater 5, and the amount of heating is automatically controlled so that the temperature of the flowing WJ layer is constant.

The hot gas leaving the fluidized bed is separated from entrained particles by a cyclone 8 and discharged through a pipe 9. The particles collected by the cyclone are continuously returned to the fluidized bed 2 through a conduit (despreg) 10.

The structure and effects of the present invention will be specifically illustrated below using Examples and Comparative Examples.

1 difference j A fluidized bed apparatus made of steel pipes having the structure shown in FIG. 1 was used. The main specifications of the device are as follows.

Fluidized bed inner diameter: 8cm Fluidized bed height: 1m Heated fluid conduit inner diameter: 4 mm Heated fluid conduit length: 4m Electric heater (nominal)・2kw The specifications of the solid particles used are as follows.

Base material rainbow liquor alumina fluid catalyst weight average diameter (50% by weight) + 561Lm bulk density + 0.8
5 g/am'' The above fluidized bed apparatus was filled with 2.7 kg of the above solid particles, 38 ONl/h of air was flowed at room temperature to form a fluidized bed, the fluidized bed was heated with an electric heater, and the temperature of the fluidized bed was increased. Approximately 2
When the temperature reached 50'C, 2.5 kg/h of petroleum pitch, which had been preheated to about 200°C and became liquid, was flowed into the heated conduit.

Next, the fluidized bed temperature was set to 380'C and automatically controlled (air linear velocity 5 cm, 7 seconds).When the fluidized bed temperature was almost stabilized, the fluidized bed temperature was maintained at 380±1'C and the temperature of the outflowing pitch was maintained at 380±1'C. The temperature became almost constant at 379±1°C.

The power consumption of the electric heater at this time was about 0.8 kW.

L comparison 1 Solid particles having the following specifications were used.

Base material: sand Weight average diameter (50% by weight): 500gm Bulk density: 1.4
g/cm' Using the fluidized bed apparatus used in the example, 4.4 kg (equivalent in volume to Example 1) of the above solid particles was filled.

A fluidized bed was formed by flowing air at 380 V/h at room temperature, but the pressure fluctuations in the fluidized bed were large and the fluidized state was extremely uneven.Next, the fluidized bed was heated with an electric heater, and the fluidized bed was Approximately 20℃ when the temperature reaches approximately 250℃
2.5k of liquid petroleum pitch preheated to 0℃
g/h into the heated conduit.

Next, the fluidized bed temperature was set to 380°C and automatically controlled (
The temperature of the fluidized bed was maintained at 380±2° C. when the air line velocity was 50 cm/sec) and the temperature became almost constant, and the temperature of the pitch flowing out was 378±2° C.

The power consumption of the electric heater at this time was approximately 1.3kw.

Note that the fluidized bed apparatus used in the Examples and Comparative Examples is a small experimental apparatus, so the proportion of heat loss from the outer wall of the apparatus (the same in both Examples and Comparative Examples) in the amount of heat required for heating is relatively large. In large-scale equipment, the ratio of heat loss from the outer wall of the equipment becomes small, and the ratio of heat loss due to fluidizing gas discharged from the fluidized bed increases significantly. Significantly superior to conventional methods.

In addition, the air flow rate in the example is one-tenth that of the comparative example, and when considering the pressure loss of the fluidized bed due to the difference in bulk density of one particle, the blowing power in the uninvented case is less than one-tenth of the conventional method. In large-scale equipment, it is expected that the amount of heat required for heating will be reduced and the energy economy will be significantly improved compared to conventional methods.

C.8 Effects of the Invention The method of the present invention has the following advantages over conventional methods.

a. The pressure fluctuation in the fluidized bed is small, and even if the inside of the fluidized bed is raised, slagging (fluidized bed moves up and down like a piston) does not occur, and a sufficient heat transfer surface is obtained.
Easy to rotate.

b, the temperature inside the fluidized bed is uniform, and the fluidized bed and R inside it.
Since the heat transfer coefficient between the heated fluid container and the heat transfer surface can be increased, the heated fluid can be heated more uniformly than in the conventional method.
It can be heated to a certain temperature.

Breakdowns due to wear of the CO device and wear and tear of particles are significantly reduced.

d. Fluidization is possible with a small superficial gas velocity, so less electricity is required for gas supply, and the amount of high-temperature fluidizing gas discharged is small, reducing the associated heat loss and heating. The amount of heat required for this is reduced.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of an apparatus for implementing the present invention.

Claims (1)

[Claims] 1. A method of heating a fluid by installing a fluid container having a heat transfer surface in a heated fluidized bed in which solid particles are fluidized by a gas, wherein the solid particles have a weight average diameter of 30 ~120μm, bulk density 0.3~1.5g/cm^3
A method for heating a fluid using a fine powder fluidized bed, characterized in that substantially spherical particles are used, and the rising speed of the fluidizing gas is maintained at 2 to 40 cm/sec based on the empty column of the fluidized bed. 2 In a method of heating the fluid by installing a fluid container having a heat transfer surface in a heated fluidized bed in which solid particles are fluidized by gas, the solid particles have a weight average diameter of 30 to 120 μm and a bulk density of 0. .3~1.5g/cm^3
Using substantially spherical particles, the rising speed of the fluidizing gas is maintained at 2 to 40 cm/sec based on the empty column of the fluidized bed, and the particles scattered with the gas are collected and returned to the fluidized bed. A method for heating a fluid using a fine powder fluidized bed.