JPH0459927B2 - - Google Patents

Abstract

It is known to desulphurise flue gases by passing them through a scrubber. In order to achieve the necessary chimney temperature of the clean gas stream, the heat of the crude gas stream is utilised which can be transferred to the clean gas stream via a heat displacement system. As long as the temperatures lie above the dew point of sulphuric acid, materials such as steel can be used for this. However, difficulties result if the temperatures are below the dew point of sulphuric acid, so that special measures have been found. <??>The invention now provides staggered heat displacement systems 13, 14, in which, initially, in a relatively high temperature range, heat exchangers 3, 7 made of steel are connected together via a heat transport medium and, in a downstream second heat displacement system 14, heat exchangers 4, 6 made of corrosion-resistant and antiadhesive plastics are used. <IMAGE>

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is an energy transfer device for a desulfurization plant, in which a heat exchanger is installed in the rough gas stream before the scrubber, the heat exchanger being By means of a forcedly guided flowing heat carrier, it is connected for fluid exchange purposes to another heat exchanger installed in the raw gas stream behind the scrubber, in this case possibly with fins. The invention relates to a type of heat exchanger in which the heat exchanger tubes and the communication conduit are made of a pressure-resistant material, for example steel.

BACKGROUND OF THE INVENTION As a result of extensive efforts to prevent environmental pollution, it has become necessary to take measures to desulfurize flue gas in both newly constructed and existing power plants. In this case, wet desulfurization systems are mainly used. In this wet desulfurization system, during the cleaning process the flue gas is cooled by the cleaning solution so that it exits the washer at a temperature of approximately 50°C.

However, the purified flue gas must be heated again to at least 72°C before being released to the atmosphere. A variety of different methods have been developed to accomplish this heating. An energy-economically optimal method involves extracting the thermal energy required for reheating from unpurified hot raw gas.

For this purpose, a heat exchanger with fins is installed in the raw gas stream before the scrubber, through which a heat carrier flowing through, for example antifreeze water, is connected to another heat exchanger with fins. A heat exchanger with a vessel is connected, which heat exchanger is arranged in the clean gas stream after the washer. This device can be used to extract heat from the rough gas stream and release it via a heat carrier into the clean gas. In this case, the connecting conduits for the tubes and the heat carrier are usually made of steel. However, this poses significant problems when temperatures in the sulfuric acid condensation point range occur. It has therefore already been proposed to coat individual components of heat exchangers. However, in this case, it has been confirmed that due to the large molecular structure of the coating material, a residue consisting of diffused molecules is formed under the coating layer over time. This residue not only destroys the base material but also dissolves the coating layer. Furthermore, it is already known to use hollow heat exchangers in flue gas desulfurization equipment. However, neither treatment has been able to satisfy the industry for various reasons.

Problem to be Solved by the Invention It is an object of the invention to improve the energy transfer device of a desulphurizer of the type mentioned in the introduction so as to provide a satisfactory supply of flue gas over a long service life without the use of expensive materials. The goal is to ensure that no purification is achieved.

Means for Solving the Problems The problem of the present invention has been solved by the features set forth in claim 1.

Effects of the Invention In the configuration of the invention, two heat exchange systems working at different temperature levels are connected in series. The crude gas, still very hot at approximately 140° C., is first passed through a heat exchanger comprising smooth or finned thick-walled steel tubes. Here, cooling takes place to approximately 115°C.
The heat carrier picks up heat from the hot gas and releases it into the clean gas via a heat exchanger integrated into the clean gas stream. Since a constant temperature of 105° C. to 120° C. is obtained during the circulation of the heat carrier, no temperature below the condensation point of sulfuric acid occurs anywhere in the heat exchange system made of steel. That is, at temperatures above 65° C., substantially all of the droplets contained in the clean gas after the washer droplet separator are vaporized.
Crusts therefore no longer form on the surfaces of the heat exchanger in the clean gas stream. Of course, for safety reasons it is also possible to additionally equip a carbon fan.

For the second stage, ie cooling to a lower temperature level, a heat exchange system is used, the material of which is corrosion-resistant and non-stick plastic. Depending on the heat carrier temperature set for this purpose, the raw gas is cooled, for example, from 115° C. to 95° C. Based on this temperature level, the sulfuric acid condensation point is passed on the raw gas side in the area of the heat exchanger installed there. The acid formed therein partly flows or drips down along the hose or pipe, or partly mixes with the ash and deposits on the hose or pipe. Purified water can be used for cleaning. This purified water can be collected and fed to a washer.

The heat absorbed by a heat carrier, e.g. antifreeze water, circulating in plastic hoses or pipes is
The clean gas stream is led to a low temperature heat exchanger arranged between the scrubber and the radiant heat exchanger, via which the clean gas is transferred. In this case, the clean gas is heated to a temperature of about 50°C to over 65°C. As a result, any water droplets still present in the gas stream on the inlet side of the heat exchanger are completely vaporized. In this case, the calcium sulfate contained in the drops may remain. In this manner, a crust of calcium sulfate should form on the plastic surface. However, because of the non-stick surface properties of the plastic used, this crust can be easily cleaned by shaking. Furthermore, temperature fluctuations can also be used for cleaning.

The invention makes it possible to use conventional pressure-resistant materials, such as steel, in the high temperature range above the sulfuric acid condensation point of the rough gas stream and above the drying range of 65°C for the clean gas stream. Make it. In contrast, in the lower temperature range, plastic pipes or hoses are used virtually without pressure, both in the raw gas stream and in the clean gas stream.

The arrangement of both heat exchange systems arranged in series in stages can be carried out at any point in the raw gas and clean gas streams. Heat exchangers connected to each other by heat carriers, arranged in the rough or clean gas stream in each system, can be separated by more than 50 m without causing any interference. Furthermore, the invention allows easy retrofitting of existing equipment. Since the clean gas is not contaminated by the rough gas, fans can be placed in both the dry rough gas stream and the dry clean gas stream. Also, the degree of separation achieved in the washer is maintained. That is, the degree of separation is also the degree of separation of the flue gas desulfurization device. In addition, since known corrosion-resistant and durable materials can be used,
A long service life is achieved which does not result in wear of the heat exchanger even with long operating times.

Embodiments Advantageous embodiments of the invention are defined in claim 2.
It is described in the section. Of course, heat exchangers constructed from such plastics can only be designed for relatively low internal pressures. Since the aforementioned materials have a tendency to flow at high temperatures and pressures, both temperature and internal pressure must be reliably guaranteed. In this case, however, it is also possible to take into account the relatively low pressure resistance of the plastic by choosing the temperature of the heat carrier below 100 °C and placing a cascade of water coolers in front of the individual heat exchangers. can. This ensures that the pressure generated in the heat exchanger never exceeds tolerances.
Furthermore, a sudden rise in temperature in the flue gas no longer increases the internal pressure.

According to the feature recited in claim 3, the temperature of the heat carrier can be maintained at a desired level.
These advantageous properties also apply, of course, to the heat transfer system made of steel in the first stage.

In order not to excessively increase the pressure in the heat exchanger through which water as a heat carrier passes, which is advantageously arranged at different heights, it is possible to
The features of terms are helpful. This ensures that each heat exchanger is provided with only a predetermined water pressure. Water, which transfers heat from the rough gas to the clean gas, flows through the heat exchanger on a head-to-head basis. Return flow is provided by a pump.

The features of patent claim 5 are useful for monitoring the outflow of the heat carrier through the heat exchanger which is arranged at a metrologically low level.

A particularly advantageous embodiment of the invention is indicated in claim 6. Such hoses or tubes can be arranged in bundles, so that the individual heat exchanger bundles can also be removed individually and replaced during operation. By means of U-shaped hoses or tubes the distribution and collection chambers can be arranged outside the gas flow. Accessibility is thus guaranteed in a simple manner.

If the U-shaped suspended plastic hose or tube is perpendicular to the gas flow, a horizontally freely suspended plastic hose or tube may also be provided, as indicated in claim 7. I can do it.

The fixing of the plastic hoses or tubes to the heat exchanger bottom takes place with the features of claim 8. For this purpose, first a hose or tube is inserted into the tube bottom. The plug-in sleeve is then inserted into the end section and then expanded.

In this connection, it is advantageous if the plug-in sleeve is made of copper or brass, as specified in claim 9.

In accordance with the features recited in claim 10, each hose end is provided with a water inlet which is dynamically favorable for fluid with low losses.

By using the features of patent claim 11, bending of the hose or tube at the bottom is avoided.

Depending on the features of claim 12, the inlet of the individual hoses or pipes into the distribution or collection chamber can be controlled during operation and the hoses or pipes can also be clamped in severe cases. . Additionally, this procedure ensures the use of high-strength conventional materials for constructing the distribution and collection chambers, and the use of a separate, corrosion-resistant but low-strength material for inserting into the gas sealing surfaces. do.

As described in claim 13, fixing the plastic hose or tube to the gas sealing surface in a self-sealing manner reduces the water pressure generated inside the hose during operation due to the elasticity of the flexible hose or tube. achieved in connection with. This water pressure is higher than the expected gas pressure.

The supply of purified water in pulsed streams as described in claim 14 allows for easy cleaning in conjunction with the non-stick surface properties of the plastic. In this case carbon, dust and sulfuric acid are washed away. In connection with this, one distribution pipe protrudes into each tube bundle, from which purified water can also flow out laterally at predetermined intervals.

The roof-sloping spacer plate according to claim 15 not only ensures that the plastic hoses or pipes are well guided, but also ensures that the purified water flows out perfectly.

According to claim 16, vibrations are imparted to at least the low temperature heat exchanger arranged in the clean gas stream. The dirt that adheres thereby is removed by rocking. Oscillation can also be combined with thermal expansion of the plastic material. The adhering parts are destroyed upon temperature changes. For this purpose, it is sufficient simply to ensure that the longitudinal expansion of the hoses and tubes is unhindered.

The invention will now be explained with reference to the drawings: The device 1 shown schematically in FIG. 1 forms part of a coal power plant and is used for the desulphurization of the flue gas produced in the power plant.

Rough gas flowing out from electric filter 2 in the direction of the arrow
ROS has a temperature of about 140°C, and at this temperature, first,
Made of steel, with fins extending parallel to each other,
It is passed through a heat exchanger 3 having a series of heat exchanger tubes not shown.

After leaving heat exchanger 3, the raw gas ROS still has a temperature of approximately 115°C. Rough gas at this temperature
ROS loads another heat exchanger. This heat exchanger 4 will be explained in detail using FIGS. 2 to 6.

From this heat exchanger 4 the rough gas stream ROS comes out at a temperature of about 95°C. Upon entering the washer 5, the crude gas is wet desulfurized.

The temperature of the purified flue when exiting the cleaner 5 is approximately 48°C.
, and at this temperature the clean gas stream RES is sent through the heat exchanger 6. This heat exchanger 6 is connected in a heat exchange manner with a heat exchanger 4 in the rough gas stream ROS. In this heat exchanger 6, the clean gas stream RES is heated to approximately 68°C,
It is then passed through another heat exchanger 7. This heat exchanger 7 is connected for heat exchange with a heat exchanger 3 installed in the rough gas stream ROS.

After leaving heat exchanger 7 the clean gas flow RES is approximately 90
℃ and is discharged into the atmosphere via the flue 8 at this temperature.

Built into rough gas flow ROS and clean gas flow RES,
Heat exchanger 3, 7 with thick-walled steel tubes with fins
are fluidly connected by conduits 9,10. The fluid medium consists of antifreeze water. This water is heated to approximately 120℃ in heat exchanger 3,
It flows via conduit 9 to heat exchanger 7 in a clean gas stream RES, where it is cooled to approximately 105°C. A return flow of the heat carrier is ensured by a pump in conduit 10. By adjusting the bypass 12, the temperature of the heat carrier is maintained between 105°C and 120°C. Therefore, wall temperatures below the condensation point of sulfuric acid do not occur anywhere in the heat transfer system 13 made of steel.

Heat exchangers 4, 6 installed in the heat transfer system 14 of the second stage of the rough gas desulfurization plant 1 for the rough gas stream ROS and the clean gas stream RES are connected to each other by conduits 15, 16. In this heat transfer system 14, water is circulated which is likewise protected from freezing and has a temperature range between 70°C and 80°C. This water is a rough gas flow
It is heated to approximately 80° C. in a heat exchanger 4 located in the ROS and flows from there via a conduit 15 to a heat exchanger 6 located in the clean gas stream RES, where it releases the heat to the clean gas. This cools the heat carrier to approximately 70°C. At this temperature, the heat carrier is passed back into the heat exchanger 4 in a rough gas stream ROS, for example using a pump 17. The conduits 15, 16 are connected to each other by a bypass 18.

Since the temperature of the circulating heat carrier of the second heat transfer system 14 is approximately 75° C., the sulfuric acid condensation point is passed on the raw gas side. In order to avoid damage to the heat transfer system 14, both heat exchangers 4, 6 are covered or coated with a corrosion-resistant and non-stick plastic. The plastic can be polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, or the like. Furthermore, the conduits 15, 16 between the two heat exchangers 4, 6 can also be made of at least corrosion-resistant plastic.

In order to carry out the heat exchange (see Figures 2 and 3), in the case of horizontal gas flows, U-shaped plastic hoses were bundled from above in both the rough gas flow ROS and the clean gas flow. suspended in shape. The plastic hose can be made of, for example, polytetrafluoroethylene, polyvinylidene fluoride or polypropylene.

As an example, in FIG. 2, a heat exchanger 4 installed in the rough gas stream is divided into three sections A, B, and C, as well as a heat exchanger 6 installed in the clean gas stream RES. It is designed to be able to be inspected individually and during operation. Each section A, B, C
The U-shaped bundling of the plastic hoses 19 in (FIG. 3) makes it possible to arrange only one distribution chamber 20 and one collection chamber 21 in one plane outside the gas stream ROS or RES. Separation is effected by a gas sealing surface 22 of a suitable material. The heat carrier enters the distribution chamber 20 and thus the hose 19 as indicated by the arrow 23 and exits from each section A, B, C as indicated by the arrow 24.

As shown in FIG. 4, the fixation of the individual hoses 19 in the bottom 25 of the distribution and collection chambers 20, 21 is achieved by inserting the hoses 19 into the corresponding holes 26 in the tube bottom 25 and then pushing and expanding them. This is done by fixing with an open insertion sleeve 27 made of copper or brass. The shape of the plug-in sleeve 27 is chosen such that a hopper-like water inlet or outlet 28 is provided at the end in order to reduce flow losses. Furthermore, the length L of the plug-in sleeve 27 is selected to be greater than the thickness D of the tube base 25. In this way, the hose 19 is prevented from bending at the bottom 25.

As can be seen from Figures 2 and 5, heat exchangers 4 and 6
Each section A, B, C is pierced by a vertical tube 30. The tube 30 is mounted in a gas-tight manner on the gas sealing surface 22 and has lateral outlets 31 at different heights. By supplying purified water as indicated by arrow 32, the hoses 19 (FIG. 3) tied together in each section A, B, C are purified in a pulsed flow as required. Purified water is supplied to the drainage section via the water tank 33. All parts of the heat exchangers 4, 6 that come into contact with the raw gas are made of plastic, which is at least corrosion-resistant. These parts are a tube bundle guide 35, an apron 36, a water tank 33 and a discharge section 34.

Furthermore, it can be seen from FIG. 5, in conjunction with FIG. 3, that the individual hoses 19 are forced to be guided to different heights. For this purpose, a spacer plate 37 is used which slopes laterally in a roof-like manner from a vertical central longitudinal plane. The slope of the roof allows the purified water to flow outwards towards the tank. Total heat exchanger 4, 6
Or individual parts can be vibrated as required. The rocking system necessary for this purpose is not shown in the drawing.

In FIG. 6, the low temperature heat exchangers 4, 6 of the second heat transfer system 14 are arranged at metrically different heights.
In order to prevent the pressure in the heat exchangers 4, 6 from increasing excessively, intermediate tanks 38, 39 are disposed before and after the heat exchangers 4, 6, respectively.
This intermediate tank 38, 39 ensures that each heat exchanger 4, 6 withstands a certain water pressure differential. rough gas flow
The water that transfers heat from the ROS to the clean gas RES flows through the heat exchangers 4 and 6 based on the head difference. The discharge through the heat exchanger 6, which is arranged at a lower measurement level, is monitored by a pressure-controlled regulator valve 40 arranged in the conduit 15. Pump 17 transports the heat carrier via conduit 16 from intermediate tank 39 to intermediate tank 16 and from intermediate tank 39 to intermediate tank 38 .

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a flue gas desulfurization apparatus having two heat transfer systems arranged in series with stages in the rough gas flow; Fig. 2 is a diagram showing the heat exchanger of the heat transfer system of Fig. 1; Figure 3 is an enlarged view showing details of the heat exchanger in Figure 2, Figure 4 is an enlarged view of a portion of Figure 3, Figure 5 is a detailed perspective view of the heat exchanger in Figure 2, and Figure 6 is a detailed perspective view of the heat exchanger in Figure 2. The figure shows another embodiment of the heat transfer system. 1... device, 2... electric filter, 3... heat exchanger, 4... heat exchanger, 5... cleaning device, 6... heat exchanger, 7... heat exchanger, 8... flue ,9,10
... Conduit, 13 ... Heat transfer system, 14 ... Heat transfer system, 15, 16 ... Conduit, 17 ... Pump, 18
...Bypass, 19...Plastic hose, 2
0...Distribution room, 21...Collection room, 25...Pipe bottom,
26...hole, 27...insertion sleeve, 28...outlet, 30...pipe, 31...outlet, 33...water tank,
34... Discharge section, 35... Tube bundle guide, 36...
Apron, 37... Spacer plate, 38, 39...
Intermediate tank, 40... regulating valve.

Claims (1)

[Scope of Claims] 1. Energy transfer device for a desulfurization plant, in which a heat exchanger is installed in the rough gas stream before the scrubber, the heat exchanger being forced to guide a flowing heat carrier. is connected for fluid exchange purposes to another heat exchanger integrated into the clean gas stream after the scrubber, in which case the heat exchanger with the heat exchanger tubes and the communicating conduit are pressure resistant. In the type made of the material, it is resistant to the rough gas flow ROS between the heat exchanger 3 and the washer 5 and the clean gas flow RES between the TO washer 5 and the heat exchanger 7. One heat exchanger (4
or 6), respectively, and these heat exchangers 4, 6 are connected to one another in such a way as to conduct a heat carrier by means of communication conduits 15, 16, which are also made of at least corrosion-resistant plastic, in which case: Energy for a desulfurizer, characterized in that all gas contacting parts (33-37) of the low-temperature heat exchangers 4, 6 are covered or coated with a corrosion-resistant and non-stick plastic. Mobile device. 2 Low temperature heat exchangers 4, 6 and their communication conduits 15, 1
6 consists of polytetrafluoroethylene, polyvinylidene fluoride or polypropylene or is covered or coated with polytetrafluoroethylene, polyvinylidene fluoride or polypropylene, claim 1
Energy transfer device as described in Section. 3 Communication conduit 15, 1 between low temperature heat exchangers 4, 6
3. Energy transfer device according to claim 1 or 2, characterized in that 6 are connected to each other by a bypass 18. 4. The low-temperature heat exchangers 4, 6 are arranged at different geodesic heights, and one intermediate storage 38, 39 is provided for the heat carrier before or after the low-temperature heat exchangers 4, 6, respectively. An energy transfer device according to any one of claims 1 to 3. 5. Energy transfer according to claim 4, in which a pressure-controlled regulating valve 40 is integrated in the communication conduit 15 from the elevated low-temperature heat exchanger 4 to the low-temperature heat exchanger 6. Device. 6. A low-temperature heat exchanger 46 with a horizontal gas flow comprising a U-shaped plastic hose or tube 19 suspended from above in the rough gas stream ROS and the clean gas stream RES. The energy transfer device according to any one of items 1 to 5. 7 Claims 1 to 5 with a vertical gas flow and in which a plastic hose or tube 19 is provided horizontally and freely suspended within the low temperature heat exchanger 4, 6. An energy transfer device according to any one of the above. 8. According to any one of claims 1 to 7, in which the free end of the plastic hose or tube 19 can be fixed to the heat exchanger base 25 by an expandable bayonet sleeve 27. The energy transfer device described. 9. Energy transfer device according to claim 8, wherein the plug-in sleeve 27 is made of copper or brass. 10 Outer end section 28 of bayonet sleeve 27
The energy transfer device according to claim 8 or 9, wherein the energy transfer device is expanded into a hopper shape. 11 The length L of the insertion sleeve 27 is the heat exchanger bottom 2
5. Energy transfer device according to any one of claims 8 to 10, wherein the energy transfer device is greater than the thickness D of 5. 12 The distribution chamber 20 and the collection chamber 21 of the low temperature heat exchangers 4, 6 are separated from the gas streams ROS, RES by a corrosion-resistant gas sealing surface 22. An energy transfer device according to any one of claims 1 to 11. 13 A plastic hose or tube 19 is secured in a self-sealing manner to the gas sealing surface 22. An energy transfer device according to claim 12. 14. The plastic hose or tube 19 can be loaded with a pulsed flow of clean water. An energy transfer device according to any one of claims 1 to 13. 15. The plastic hose or tube 19 is guided between the gas sealing surface 22 and the curved length section through at least one spacer plate 37 which slopes roof-like laterally from a vertical central longitudinal plane;
An energy transfer device according to claim 6, 13, or 14. 16. Energy transfer according to any one of claims 1 to 15, characterized in that vibrations are imparted to at least the cryogenic heat exchanger 6 arranged in the clean gas stream RES. Device.