DE202009015181U1 - Contact surfaces of tubular impact bodies for the improvement of SO2 separation in flue gas desulphurisation - Google Patents

Abstract

Contact surface to improve the separation of SO2 and dust in a flue gas desulfurization installation below the spray levels in a REA with vertically upwardly directed flue gas stream consisting of tubular baffles, said plastic tubes are preferably polypropylene horizontally and mounted on a support structure, wherein the contact surfaces of the Cover the entire scrubber cross-section and wherein the pipe segments are permanently wetted with suspension liquid and the SO2 contained in the flowing flue gas can be deposited in this suspension liquid.

Description

The This invention relates to an improvement in SO2 deposition in flue gas desulphuris (REA) from coal power plants. The dust and Sulfur dioxide separation in the REA is due to the use of Tube contact bodies or roller contact bodies improved become.

fumes From fossil-fired thermal power plants become predominantly Desulphurized by the wet scrubbing process. The sulfur-containing flue gas (Suspension solution) is sprayed with limestone milk (most widely used method) and that in the flue gas SO2 in the spray drops of this suspension solution and then converted to calcium sulphite dihydrate (gypsum).

additionally are also fine dust, which pass through the electrostatic filter could, partly deposited - if the dust particles come in contact with the suspension liquid.

It There is now a need for a variety of reasons to further improve the deposition. On the one hand, there are the environmental requirements many countries that are increasingly restricting emissions of SO2 and power plants to optimize SO2 capture.

Secondly will be the certification procedure in the USA and in the future also in Europe operated. The power plant must emit SO2 for every ton to buy a certificate. The price of these certificates rises in the the last few years, on the one hand, governments less and less allowances in the market, on the other hand environmental organizations buy these certificates and third, the power production continues to increase. The emission of SO2 therefore causes the power plant considerable costs.

Last will be the introduction of CO2 capture in the next Future planned. The processes that remove the CO2 from the flue gas and then deposition is based largely on the principle the amine wash. This requires a very big one Purity of the flue gas of SO2 (and SO3) because these two substances cause the amines to be decomposed. The costs The CO2 scrubbing is driven up by this.

It there is a need today, and more so in the future, to improve the SO2 purification in the REA and to separate the SO2 as much as possible.

It Now there are a variety of methods of wet washing, with where the SO2 can be deposited in a REA. Essentially can distinguish three methods: spray tower, Blubberverfahren and contact surface method.

The large mass of plant engineers and already built plants are so-called spray towers. The flue gas will directed from below into a large container tower and becomes as it flows upwards sprayed with suspension liquid. The efficiency These spray towers can be known by a variety Measures are optimized.

modern Nozzle technology ensures that the spray levels spray as many very small drops as possible. This optimizes the deposition - because of a high number from drops also to a correspondingly high contact probability between the SO2 molecules and the suspension drops.

The Of course, deposition can also be improved by that you increase the number of spray levels used. Of course, this also has a corresponding increase the deposition, because here too the probability increases that a SO2 molecule with a suspension drop comes into contact.

Further In recent years, the improvement of the flue gas duct has been very strong worked. The separation efficiency for dust and SO2 largely depends of how well it succeeds, the entire cross-section of a REA Cover with spray cones (for each spray level!). A gap without spraying does not lead only to have a proportional part of the flue gas through them Gap flows. However, the spray cone for the flue gas flow a considerable resistance represents, the greater the amount of flue gas to this and through this gap, because of the Flow resistance at these points of course is correspondingly low and therefore much flue gas through this gap will escape the resistance of the flue gas flow.

each Gap in the flue gas flow thus leads to a large volume of flue gas spraying with suspension liquid and thus the cleaning of dust and SO2 avoid and unpurified can continue to flow.

A well-known problem is the leakage flows along the scrubber wall. Due to the flow conditions, particularly strong gas flows form on the walls. For example, the flue gas stream is introduced at high speed from the side into the REA. The nozzles located above the inlet spray onto this flue gas stream and rear it up. Instead, the flue gas flow shifts across the REA to the side opposite the entrance to bounce against the wall. Then it will be the flue gas is pushed upwards by the inflowing flue gas and a particularly strong stream of flue gas flows up the wall on the wall opposite the inlet.

It was therefore a few years ago by the company Marsulex the Concept of a wall ring designed and patented. This acts it is a protruding into the flue gas flow bead. This is formed from two plates welded to the wall become. These pointed beads press the flue gas stream under the nozzle screen in the absorber and interrupt it the mass flows described above or cover the gaps in the spray cones described above the nozzles. However, it is also a problem here that These wall rings protrude into the spray cone of the nozzles and therefore suffer from abrasion.

aid The CFD analyzes (Computational Fluid Dynamics) are the flue gas flows analyzed and the nozzle configuration is set so that a uniform distribution of the flue gas flow is reached on the cross-sectional area. Through these analyzes be the nozzle configuration (distances, alignment and configuration of the nozzle) in iterative analyzes adjusted the need so that despite different flow of the first nozzle plane through a uniform flow the multiple spray levels arise.

With Help of these measures is today quite possible, up to 98% of SO2 at a reasonable cost. Even higher Separation rates are possible - but leads that then leads to considerable operating costs. Currently 80% worldwide the REA built with this technique.

A alternative concept is provided by the companies Chiyoda and Alstom (Flowpac) represented. Here, the flue gas is passed through a liquid layer (Bubble). The flue gas is introduced from below and then through a perforated plate through this liquid layer. The flue gas flows through the liquid layer in the form of many small bubbles.

These On the one hand, this method can point to high precipitation rates but in the past also operating problems due to caking. Currently, this technique is only sporadically built.

The third concept is a mixture of the two previously described Techniques. It becomes one compared to the conventional spray tower reduced number of spray levels used and the deposition reinforced by contact surfaces.

On At first glance, the contact surface methods have the Advantage that the operating costs could be lowered, since the Number of spray levels has been reduced.

The However, a majority of these proceedings suffered from the fact that the contact surfaces are heavily polluted with time and massive caking developed, on the one hand for cause an increase in the pressure loss and on the other hand only below considerable effort could be cleaned again.

It Although considerable effort was made in optimizing the contact surfaces plugged to prevent this tendency to caking. However, could most procedures in the market because of the pollution issue not pass.

Just a process has been successful in the market, the "tray" of Babcock & Wilcox. This "tray" is a segmented one Perforated plate. The suspension liquid is from a conventional Spray level sprayed on the rising flue gas and thus already has a cleaning function. After that, the drops fall However, on the "tray" where they have a liquid layer form several centimeters high. That through the holes Rising flue gas displaces the liquid and avoids that the liquid immediately down through the Leaves holes in the "tray", but always a certain level of fluid on the "tray" is. These "trays" have proven very successful because they do not pollute and reach a very high deposition. They have a similar operation as the blubber reactors Alstom and Chiyoda - just a much thinner Liquid layer.

Also if the one to two spray levels above the tray still separate SO2, so the mass of the deposit but reached through the "tray". In older ones Attachments, the spray level was designed so that As a result, almost no Abscheideffekt more was achieved (no nozzles but baffles) and still with a "tray" yet Separation rates of over 90% were achieved.

These "trays" have the advantage that the number of feed pumps in comparison is significantly reduced to a conventional spray tower. Instead of three to six spray levels (pumps) are only one up to two spray levels (pumps) in use. That reduces Of course, operating and maintenance costs significantly. On the On the other hand, the "trays" cause a whole considerable pressure loss. A pressure loss of 5-8 bar for a clean "tray" is normal.

So far the state of the art for the REA.

Basically, the use of Kontaktflä chen known from many processes as advantageous. Contact surfaces lead - depending on the design - to a very high contact of a gas flowing through with the liquid and thus a very high separation (or a high heat transfer - cooling tower).

Just In the REA, this concept could not prevail, because the Development of caking from the chemical process of the REA that even made simple contact surfaces relatively quickly and during operation high pressure losses and after operation high cleaning costs incurred. The contact surface principle was because of these costs, but even more because of the resulting Operating insecurity less and less used in the REA.

It However, there are two findings from the operation of REA, which it seem to let the subject touch surfaces again pick up. On the one hand, there is the experience that has been around for many years Years in use REA the Babcock & Wilcox with the "tray" no serious contamination issue with the "tray" knows.

on the other hand There are interesting experiences from the Abscheidergebiet, the application could find. The separators are in the REA above built in the spray levels and have the function of the drops to be separated, which entrained in the spraying process with the flue gas were.

The slat separators used here for decades suffered and suffer to varying degrees also under massive caking - similar like the contact surfaces. In extreme cases were the mist eliminators are so clogged after just two to four weeks, that the REA drove off and cleaned the mist eliminator manually had to be.

The Although slat separators do not basically have the function the contact surfaces, but it is known that here too still SO2 deposition can take place - especially in REA with a rather low rate of precipitation in the spray tower. Furthermore, the lamellae are similar to most contact surfaces designed as plates or curved plates.

In the last 10 years, however, a type of droplet separator has been developed and has been used very successfully in many REA - the roller separator (among others DE 20 2007 004 864 . DE 20 2005 002 723 . DE 203 02 380 and other utility models and patents).

With This type of separator has two experiences:

1. Solution of pollution problems

It could be the problem of pollution in many power plants the droplet separator (lamella separator) can be loosened, by replacing the lamella separator with a roller separator or a roller separator was connected upstream of the lamella separator. The pollution problem disappeared in most cases completely and the deposition was improved.

2. Operation without Waschbedüsung

The Known lamella separators are usually involved in the coarse separator an upstream side and a downstream side Wash spray equipped. This wash spray is usually once an hour for 60 seconds operated. Nevertheless, the mist eliminator could not caking be kept free. Many of the built-in roller separators come but without Waschbedüsung off. You simply have none Waschbedüsung. This also applies in particular to REA, where an existing lamella separator, with two Waschbedüsungen was equipped, which now has an upstream roller separator received without Waschbedüsung. Also in this case it came not to contamination of the roller separator.

It is to assume that the geometric shape of the pipe and the distances between the pipes a decisive influence on the tendency to fouling to have.

The Separator blades only have a distance of 27.5-37.5 mm (coarse separator) to each other and form in pairs a circa 170 mm high channel through which the flue gas flows. The Deflection of the flue gas by the shape of the fins leads causing the drops to be separated.

Of the Roller separator has distances of 90 mm-120 mm between the tubes and this is only the smallest distance. Due to the round geometry, the passage opens immediately back to an even greater extent. The Deflection is achieved that the flow resistance of the pipe to flow around the pipe. The flow curve is exactly the same as with the lamella.

The Invention takes advantage of the experience from the role separator and suggests a similarly configured installation as a contact surface below the spray level use.

Of the Use of a functioning contact surface would have a number of benefits for the power plants - new ones like existing power plants:

1. pressure loss

in the Comparison to a "tray" or a blubber concept (Chiyoda and Alstom) the pressure loss would be significantly reduced. Roller separators (roller contact surfaces) have a pressure loss from 0.5-0.8 mbar while a "tray" one Pressure loss of 5 - has 8 mbar. The pressure loss of a Roller separator (roller contact surface) is with the pressure loss to compare a spray level.

2. Operating costs

A Spraying level requires a huge pumping capacity around huge ones To pump liquid quantities in height and below To spray increased pressure in the flue gas stream. If a roller contact surface has a comparable SO2 separation efficiency it can be like a spray level omitted - it would result in a corresponding saving.

3. Investment and maintenance costs

A Spraying requires, on the one hand, a considerable investment Effort and on the other hand, a current considerable maintenance. A contact area is investivly minor and has low maintenance costs (as far as it is not too massive caking comes).

4. Retrofit of inventory REA

Also with existing REA, role contact surfaces could be be retrofitted. This could include inventory REA be raised to a higher level of separation - too relatively low cost.

5. Flow distribution

It a considerable effort is made in existing as well as in new construction REA for a uniform flow of the flue gas to reach in the REA. It should local speed peaks (volume peaks) avoided and a uniform spraying of the flue gas can be achieved with suspension. It is known that the "tray" a massive homogenization the flue gas results. The same was for the roller separator determined. A pipe contact surface would be many of the known irregularities avoid the gas flow. The pipe contact surface can even be configured to have a different one depending on the sector Pressure loss has compensated and thereby residual imbalances.

6. Operational safety

REA experience repeated damage and disturbances because Nozzles clog or break, pipes destroyed etc .. The consequence of these disturbances are always unequal distributions the flue gas flow and the resulting deterioration of the SO2 deposition. A contact surface knows this problem Not.

The proposed pipe contact surface has opposite the known contact surfaces the following advantages:

1st diversion

Lots the known contact surfaces for REA are surfaces, which are in the flue gas and lead this only slightly. This helps to prevent pollution in the REA. The proposed pipe contact surface has the advantage that the flue gas is diverted considerably. This is known to lead to a turbulence and increased contact many Flue gas molecules with the contact surface.

2nd round geometry - dead zones

The Round geometry minimizes dead zones (low flow zones) in the contact area. The dead zones are the places on where the caking begins. By avoiding dead zones can the danger of caking is minimized.

3. Distances

The Distances of the pipes are kept wide - so the danger of caking is minimized.

4th round geometry and self-cleaning

From the overlying spray levels becomes the pipe contact body constantly with large amounts of liquid applied. The constant strong "rain" of Suspension drops avoids the buildup of caking - it There is a permanent wash or self-cleaning. The Suspending liquid precipitating from above strikes on the tubes and keeps the top half clean. The bottom half is constantly going through the top impinging and descending suspension liquid kept moist.

5. amount of liquid

The Liquid quantity per unit area is larger as in the known contact surfaces. This will be the Danger of caking further reduced. In addition, flows the liquid due to the configuration faster than in the known contact surfaces, so that's why can not settle solids.

The inventively proposed Kon Pipe area has only a height of less than 200 mm in a two-ply configuration (two pipes offset from each other). However, it can also be used three or more layers. Despite the low height, the SO2-depositing effect is significantly higher than in the known contact bodies of Mitsubishi or Noell. However, these cause no or only a slight diversion of the gas stream. Therefore, correspondingly higher installations are necessary to achieve the same contact intensity between flue gas and suspension liquid.

When Material for the pipe contact surface is plastic - preferably Polypropylene - chosen because of its low Weight, its superior resistance to abrasion and because of its low price. It is also known that plastic surfaces bind less strongly caking than other materials .. The problem of abrasion is due to this Material choice completely avoided.

The Pipe segments are spaced at a distance but with a sufficient Gap between two tubes laid. This gap on the one hand causes flue gas to flow between the pipes can. On the other hand, due to the gap between the pipe segments drain the suspension liquid from Rain down the higher suspension spray levels. This keeps the tubes permanently through a reactive liquid film covered with the flue gas flowing through from below comes into contact and filters out the SO2 and dust particles.

The proposed concept thus consists of a number of known Components and concepts together and will only be through the special Configuration or by the novel use of the known components and concepts for an invention. The familiar concepts:

1. Use of plastic

It is nothing new plastic - especially polypropylene - in Use REA for cost-saving reasons. plastics have the advantage that they are in this highly corrosive situation not to be attacked.

2. Use of pipe segments

pipe segments were already used in the REA as a mist eliminator - as so-called pipe or roller separators. Here could the superiority the geometric shape of the pipe in terms of low tendency to fouling be proved.

3. roll and tube

The Tubes can be both tightly welded as also partly built as rotatable rollers.

4. Contact surfaces

It were used in different REA designs - eg. By Noell, Mitsubishi Heavy Industry and Babcock & Wilcox - Contact surfaces used to improve the deposition of the flue gas.

The Invention of this utility model is that the known Function of the contact surfaces in a novel and procedural like cost-related more advantageous design is implemented or the well-known Type of roller separator for a new process engineering Application is used.

The proposed design leads to a much lower Pressure loss (because of the deflection) than the known design of the "tray" and is therefore procedural in this central technical parameter advantageous over the "tray".

The Pollution problem of the contact surfaces, the installation made these contact surfaces very problematic in REA, is avoided by the configuration of these contact surfaces and makes the proposed configuration advantageous known contact surface concepts.

there can also be the rotatable suspension next to the configuration in itself advantageous. The rotatable suspension allows a movement of the tube relative to the flue gas stream. This movement may be a vibration that shakes the deposits and possibly breaks up (in hard deposits) but also a small one Rotation. The rotation is caused, for example, by the weight of the deposits. It has the consequence that the deposit is exposed to the gravitational force will slip off or slip off after rotation.

A further improvement of the deposition as well as the pollution can be generated by the contact surface in The different sectors are configured differently. Thereby the pressure loss of the contact surface can be changed become. A closer setting (less distance between the tubes) in both directions - horizontal and vertical) naturally to a larger one Pressure loss as another shot.

By different adjustment of the flue gas stream can be controlled. The sectors with high volume of flue gas (high speed) are designed with a tight configuration - thereby obstructing the flue gas flow) and the sectors with a rather small amount of flue gas are designed with a further configuration. Local obstruction of the flue gas flow redistributes the flue gas flow - from the high volume sectors to the low volume sectors.

Of the Operating and maintenance costs can be compared with conventional Spray absorbers are significantly reduced because fewer spray levels with piping, nozzles and pumps are needed. The gives the proposed configuration an advantage over the spray tower with 3-6 spray levels.

It Thus, the disadvantages of the three types mentioned are avoided but used their advantages.

The Overall configuration of the system is shown in Figure 5 in particular. The flue gas stream enters from below coming into the contact surface a, which consists of bundles of tubes, as in Figure 3 will be shown. Above the contact surface is then at least one spray level consisting of a pipeline and spray nozzles created. From this spray level the suspension liquid is sprayed onto the flue gas, with the pollutant - here SO2 - from the flue gas is washed. This spray wets and moisturizes the Contact surfaces continuously. The amount of fluid is so high that it also removes the deposits that over time form on the contact bodies, washed by these. For the latter, it is necessary that the contact surfaces evenly sprayed and evenly with Flue gas flow are applied.

1

Pipe segments, from which the contact surface is built

2

pads

3

absorber wall

4

Round absorber

5

bracket the pipe segments

6

gas flow

7

suspension rotatable roller

8th

spray system for suspension liquid

9

spray nozzle

Picture 1 round absorber with pipe contact surface

The picture shows a round REA washing tower in the top view. The absorber wall ( 3 ) and the support beams ( 2 ) are the steel structure on which the roller contact surfaces lie. The roller contact surfaces ( 1 ) cover the entire area.

Picture 2 three-layer raw contact surface

The picture shows the side view of a three-stage molded roller contact surface. The roles ( 1 ) stuck in so-called brackets ( 5 ).

Fig. 3 Depiction of the deflection

The picture shows the gas flow ( 6 ) by the roles ( 1 ). The gas flow is deflected by the rollers and around the rollers ( 1 ), which serve as flow resistors, led around.

Picture 4 rotatable roller

The picture shows the rotatable suspension of the rollers ( 1 ) in a typical shape ( 7 ).

Figure 5 Absorber in side view

The Picture shows the side view of an absorber central part with a Spray level and a level contact body. The Spray level sprays - as in the normal spray absorber - the Suspension liquid on the rising gas stream. Below this spray level lie the contact surfaces, which permanently moistened by the spray coming from above and kept moist.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 202007004864 U [0034]
• DE 202005002723 U [0034]
• - DE 20302380 U [0034]

Claims (5)

Contact surface to improve the deposition of SO2 and dust in a flue gas desulphurisation plant for installation below the spray levels in a REA with vertically to overhead flue gas stream consisting of tubular impact bodies, these plastic tubes preferably polypropylene horizontally and are mounted on a support structure, wherein the contact surfaces cover the entire scrubber section and where the Pipe segments permanently wetted with suspension liquid are and that contained in the flowing flue gas SO2 can precipitate in this suspension liquid. Contact surface according to claim 1, characterized in that the tubes have a diameter of 50-110 mm (preferably 75 mm-90 mm) and at a distance of preferably 05, D to 0.95 D (D = pipe diameter) are stored to each other. Contact surface according to claim 2, characterized in that the contact surface of at least two levels pipe segments, which are parallel to each other and offset lie so that the tubes of at least two levels on both Overlap pages immediately Contact surface according to claim 3, characterized in that a part of the tube segments rotatable is stored to achieve a flexible storage and thus to allow the falling off of contamination. Contact surface according to claim 3, characterized in that depending on the distribution of the gas stream the pipe distances over the scrubber cross section is changed to adjust for different pressure losses and the flue gas stream over the cross section of the absorber to equalize.