JPH033878B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying a heat exchanger system for heating or cooling gas.

Various heat exchanger systems are known for heating or cooling gases. Widespread are, for example, rotary heat exchangers according to the Ljungstro¨m principle, which comprise a heat storage element in the form of stationary shaped plates, tubes or sheets, which converts a hot gas stream into a cold gas stream. It moves cyclically into the flow, absorbing and releasing heat as it does so. Heat exchangers are also often used in which a hot or cold medium (for example steam or water) flows through a tube or other hollow body, around the outer surface of which a gas flows.

When known heat exchangers are used to heat or cool dust-laden gases, deposits easily form on the heat exchange surfaces. It is extremely difficult to eliminate crust formation and stickiness in heat exchanger systems when temperatures are below the dew point or when water droplets or aerosols are entrained in the gas, such as in wet-purified flue gas. be.

The crust formed on such heat exchanger systems increases the pressure drop in the heat exchanger and further impedes heat transfer between the gas and the heat exchange surfaces.

The known heat exchangers installed in such systems are therefore partially equipped with extremely complex purification devices. It is then known to clean heat exchange surfaces with steam, air or water spray. This usually requires very high pressures and very high equipment costs (DE 2948201
Publication No.). In the area of steam cans, mechanical cleaning methods are also known, for example, in which the heat exchange surfaces are periodically cleaned with a "rain of steel balls".

It is also known (e.g. U.S. Pat. No. 793,648) to place a layer of deposits of discrete particles, such as spheres, in front of the actual heat exchange surface as dirt trapping means; Deposits in the bed cause a significant pressure drop and must therefore be replaced or cleaned periodically. In another system, described in US Pat. No. 3,872,918, a rotary heat exchanger is filled with a number of moving elements in the form of stacked layers, which transfer heat to the tube walls and by their movement. to clean the heat exchange surface.
This solution would result in relatively high equipment costs, high pressure losses in the deposited layer, and moreover, the relatively small movements in such a layer significantly limit the cleaning effect.

The object of the invention is to provide a simple and effective method for purifying heat exchangers used for heating or cooling gases in such a way that heat transfer and pressure losses can be kept constant over long operating times. be.

This purpose, according to the invention, consists of a heat exchanger with elements such as a number of spheres, hollow spheres or saddle-shaped bodies that can move freely in the gas, either constantly or occasionally forming a fluidized bed. This can be achieved by deploying them in dangerous parts of the country.

Specifically, according to the present invention, a partition wall that has a rotating heat storage member, a rotating gas passage, or a chamber into which high-temperature gas or low-temperature gas is introduced alternately, and that allows gas to pass therethrough is a gas-permeable partition wall. In a heat exchanger for heat exchange between gases, which is installed transversely to the flow of gas, the gas flows downward from above between at least two said partitions, which may also be formed as heat storage members themselves. It contains a number of separately movable elements, sometimes forming a deposited layer and forming a fluidized layer when gas is flowed upward from below, and such a fluidized layer is
characterized by constant removal of deposits in at least one zone of the heat exchanger during operation by means of mutual collision and mutual friction of said elements forming a fluidized bed; A method for cleaning a heat exchanger is provided. Examples of these include the elements being formed as spheres, hollow spheres or saddle shapes, and the elements comprising or being formed of latent heat storage materials or high heat capacity materials. This purification method can be used in rotary heat exchangers with radial gas flow.

In rotary heat exchangers, the elements in the fluidized bed achieve constant cleaning of the heat exchange surfaces by impingement or friction. It has been found that in rotary heat exchangers, crusts and deposits formed by the joint action of moisture and contained dust are produced, especially in the cold gas inlet areas. According to the invention, this inlet section side is free of sticky substances, since in rotary heat exchangers which operate in countercurrent and have a vertical axis, this element serves as dirt trapping means in the form of a deposit layer. During rotation of the rotor (or rotation or movement of the gas passages in other known heat exchanger systems) the element transforms into a fluidized bed in which it is protected by collisions and friction. Automatically removes deposits. In certain applications it is advantageous to provide such devices on both sides of the heat exchanger, ie on the cold inlet side and on the hot gas inlet side. In the case of a heat exchanger driven by direct current, the element is placed on the inlet side,
This flow is carried out in such a way that the elements become fluidized beds on both sides of the heat exchanger.

This method can also be easily applied to known rotary heat exchangers with radial flow.

Examples of elements suitable for the purification method of the invention and their arrangement in known heat exchanger systems are shown in FIGS. 1 to 4.

FIG. 1 shows an element 1 of spherical shape (hollow or solid sphere) for purification.

FIG. 2 shows a cleaning element 1a formed as a saddle-shaped object.

FIG. 3 shows a heat exchanger according to the Ljungström principle having a rotating body 2, a housing 3 and a vertical shaft 4 and suitable for the method of the invention. The elements 1, 1a form a deposited layer 7 which acts as a dirt trapping means on the inlet side of the cold gas 8, where there is a risk of the formation of a crust, and this element
is purified in a fluidized bed 6 on the outlet side.

[Brief explanation of the drawing]

1 is a perspective view of a spherical element, FIG. 2 is a perspective view of a saddle-shaped element, and FIG. 3 is a perspective view schematically showing a heat exchanger according to the Ljungström principle. In the drawings, 1 and 1a are elements, 2 is a rotating body,
3 is a housing, 6 is a fluidized layer, 7 is a deposited layer,
7' is a tube, 8 is a cold zone, 9 is a hot zone, and 11 is a hot or cold medium.

Claims (1)

[Claims] 1. A device having a rotating heat storage member, or having a rotating gas passage, or having a chamber into which high-temperature gas or low-temperature gas is alternately introduced, and a partition wall that allows gas to pass through the gas flow. In a heat exchanger that exchanges heat between gases, it is installed horizontally on the
At least two heat storage elements which can also be formed as heat storage elements themselves.
Between the two partition walls, a deposited layer is formed when gas flows downward from above, and a fluidized layer is formed when gas flows upward from below.
accommodating a number of separately movable elements, maintaining such a fluidized bed constantly in at least one area of the heat exchanger during operation, and mutual collision of said elements forming a fluidized bed; and by mutual friction,
A method of purifying a heat exchanger, characterized by steadily removing deposits. 2. The method according to claim 1, which is used in a rotary heat exchanger that allows gas to flow in a radial direction. 3. A method according to claim 1 or 2, wherein the element is formed as a sphere, a hollow sphere or a saddle shape. 4. A method according to any one of claims 1 to 3, wherein a latent heat storage material or a high heat capacity material is added to the element or the element is made of such a material. .