JPS61114711A - Method and apparatus for recovering heat from contaminated high temperature exhaust gas - Google Patents

Abstract

PURPOSE:To prevent the reduction in heat transfer quantity with the elapse of time, by contacting high temp. exhaust gas with a heat exchange liquid based on polyols to recirculate said heat exchange liquid while arranging a suspended solid removing filter and a heat exchanger in a recirculation pipeline. CONSTITUTION:High temp. exhaust gas enters a contact tower 1 from a gas inlet 1a and rises through a packed bed 1b to perform not only the heat exchange with a heat exchange liquid based on polyols from a distributor 1c but also washing simultaneously therewith. The heat exchange liquid is pumped up from a liquid sump 1e by a pump 2 and passed through a filter 3 to remove the suspended solid therein while the filtered liquid reaches an air heating chamber 4 to heat air and is cooled by itself. The purified gas enters a liquid droplet separator 7 while liquid droplets therein are removed by a mesh filter 1f and fine liquid droplets are collected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application: The present invention relates to a method and apparatus for recovering the thermal energy of a high-temperature gas. However, the present invention is not very attractive when dealing with gases that contain foreign substances that are difficult to settle out, such as in a heat setter for cloth using synthetic fibers.
200°C to 250° for woven fabrics such as Tetron and Ny0/
A suitable example of the dirty high-temperature gas of the present invention is a gas containing tar-like powder particles generated when hot air of C is blown.

Conventional technology: This section describes the use of tar-containing gas during heat setting of synthetic fibers. As mentioned in the previous section, this gas is 200~2
Since it has a temperature of 50℃, its thermal energy (th
It is desirable to use permanent energy. Conventionally, indirect heat exchangers have been used to recover the thermal energy, but good results have not been obtained. The reason for this is that the heat transfer coefficient of the high-temperature gas (hereinafter referred to as dirty gas) contaminated with tar-like substances on the heat transfer surface decreases to, for example, 0.5 to 3 kcal/h°C. Furthermore, the tar-like substance that adheres to the surface is not easily removed even when rubbed with a brush. A method of processing the heat transfer surface with 7-soy sealant was also attempted, but not only was it economically disadvantageous due to the high surface thickness, but it was also difficult to process the heat transfer surface on the cooled heat transfer surface (the heat transfer surface of an indirect heat exchanger is on the high temperature side). ), liquid or solid substances may adhere,
Since it impedes heat transfer, it does not have the desired effect.

Problems Solved by the Present Invention: By eliminating the indirect heat exchange method, the present invention fundamentally eliminates the degradation of heat transfer efficiency over time, the necessity of cleaning the heat transfer surface, etc. caused by this method.

Means for solving the problem: In the present invention, a direct contact heat exchanger is used. As the heat exchange medium (heat exchange liquid), water-soluble polyalcohols such as ethylene glycol or polyethylene glycol, glycerin, pentaerythritol, trimeteleneglopane, etc., which can be produced by the reaction of ethylene oxide and water, are used. It is not necessary to use it alone; a mixture, such as a combination of ethylene glycol and polyethylene glycol, is inexpensive and highly effective.

We will enumerate the properties that this type of heat exchange liquid should have and examine the suitability of the polyalcohol.

(g) Thermal Stability 2 The polyalcohol described above does not undergo thermal decomposition up to approximately 180°C (the temperature of the heat exchange liquid used in the present invention is 100°C to 180°C).

).

(b) Self-explosive property: Polyethylene glycol has an ether bond, and the ether bond is peroxidized (of course (−) in the air).
C-0-0-C-) It is easy to become, but) Ri x f
v y ri'l co-/I/ (HOCH2CH20C
H2CH20H) with a single ether bond is
Even on its own, it has self-1 and no explosiveness.

(c) Toxicity: Unlike phenols, nitro compounds, and amines, it has low toxicity and carcinogenicity.

) Corrosion: Most common steel at temperatures up to about 200°C! (I don't eat.

(e) Captivity of dirt substances: Due to its polarity, polyol captures dirt substances.

It is preferable that the polyol contains water and that the water vapor pressure based on this water is equal to the water vapor pressure in the outside air, and the contained water makes the polyol flammable and explosive, thereby stabilizing it.

Next, the present invention will be specifically explained with reference to Examples.

In Figure 1 of Example 7, the high-temperature dirty gas enters the direct contact tower (1) from the gas inlet nozzle (la) as shown by the hollow arrow, rises to the packed bed (lb), and is distributed. Heat exchange is performed as described above with the heat exchange liquid discharged from the IC, and at the same time, substances that are washed and form dirt (tar-like substances, dust-like substances, etc.) are rubbed away. This packed bed (1b
) is similar to a packed bed used for gas absorption, humidity control, etc.
Raschig rings can be regular or irregularly filled (structured, mesh-shaped, perforated layers, etc.), but it is particularly desirable that the layer is divided into a large number of independent cells by these inclusions. The reason is that even if air enters the polyol and the polyol is combustible and ignites, it will be extinguished because the cold R ratio per volume is large, and the fire will not spread to other small rooms. It's for a reason.

The heat exchange liquid is pumped from the sump (1e) by the pump (2), passes through the filter (3) to remove suspended solids, reaches the air heater (4), and is sent from the blower (5). The rabbit heats the air that enters, cools itself, passes through Hikoji (6),
from the distributor (IC).

As the heat exchange fluid goes through this cycle, it passes through the filter (
3) leads to the inclusion of foreign matter that cannot be separated. In this case, it is sufficient to draw out a portion of the liquid and replace it with new liquid.

It is possible to recover polyol from the extracted waste liquid by vacuum evaporation, etc., but it can also be used as fuel for other equipment as appropriate.
It is easy to reject.

On the other hand, the exhaust gas that comes into direct contact with the circulating fluid through the contact layer (lb), is cooled, and at the same time removes pollutants, is separated into droplets by a mesh filter (1f), and then passed through the droplet separator (7). Enter the bottom. In the droplet separator (7), there is a contact layer (packed layer/
(layers with a large contact area per unit volume, such as stepped layers) (
7 &) are formed, and the micro droplets collide with the surface, lose interfacial energy, and are captured. In the droplet separator (7),
Circuit (7b), pump (7C), tube 8 (7d), distribution!
(7e: Circulation of liquid that flows through the Yotaka separator in one way / i
One route will be provided.

Liquid reservoir (7g) K Initially, clean water is poured in, but the liquid in the contact tower (1) containing exhaust gas is dissolved, or the exhaust gas is cooled in the water washing tower, so polyol escapes as paper in the exhaust gas. It condenses in the cooling gutter and turns into an aqueous solution of polyol. When the liquid temperature rises, a part of the liquid is sent to the pipe (8) t-week 9, the contact tower (1), and the liquid is sent to the pipe (8).
Receive fresh water supply from 7f).

In this embodiment, heat recovery from the heat exchange liquid is performed on the air taken in from the blower (5), but it may also be heated with fresh pond water, regardless of the heat recovery light.

Furthermore, it goes without saying that the D performance can be improved by adding, for example, a small amount of silicone oil as an antifoaming agent or an organic or inorganic phosphoric acid compound as a flame retardant to the heat exchange liquid. stomach.

Effective effect: As described above, the present invention is effective in treating wastewater contained in high-temperature exhaust gas, especially when an indirect heat exchanger is used. This system prevents the amount of transmission from decreasing over time by recovering heat from the exhaust gas using a direct contact tower using polyols as the heat exchange liquid and trapping pollutants in the heat exchange liquid. .

In particular, when heat-setting IR fibers (by blowing gently), some of Tetron, nylon cloth, etc. are thermally decomposed and a tar-like substance is produced, making it impossible to recycle them. Energy can be saved by heating the air and using it for combustion.

[Brief explanation of the drawing]

Figure 1 is an example of implementing the present invention. : It is a process diagram shown. 1...Concubine tower, 2...Pump, 3...Filter, 4...Heat exchanger, 5...Prower 17...Droplet molecule quasi 4゜Figure 1

Claims (1)

[Claims] 1. When recovering heat from high-temperature exhaust gas containing pollutants: (a) The high-temperature exhaust gas is passed from the bottom to the top of the contact tower, and a heat exchange liquid containing polyols as a main component is passed through the contact tower. (b) The heat exchange liquid is pulled out from the bottom of the contact tower and returned to the top of the contact tower for circulation. (c) The heat exchange liquid is appropriately added to the circulation pipe line for the heat exchange liquid. , a method for recovering heat from dirty high-temperature exhaust gas, characterized by installing a filter to remove suspended solids, and a heat exchanger to recover heat from a heat exchange liquid. 2. The method according to claim 1, wherein the heat exchange liquid is mainly composed of a mixture of ethylene glycol and polyethylene glycol. 3. The method according to claim 1, wherein the heat exchange liquid is triethylene glycol. 4. When recovering heat from high-temperature exhaust gas containing pollutants: (a) The high-temperature exhaust gas is passed from below to above, and a heat exchange liquid containing polyols as a main component is irrigated from above to below for countercurrent contact. (b) a circulation device that circulates the heat exchange liquid by drawing it from the bottom of the contact tower and returning it to the top of the contact tower; (c) installed at an appropriate position in the circulation pipe of the circulation device. In addition, a device for recovering heat from dirty high-temperature exhaust gas is equipped with a filter for removing suspended solids and an indirect heat exchanger for heat recovery.