KR101915066B1

KR101915066B1 - Method and arrangement for operating a steam turbine plant in combination with thermal water treatment

Info

Publication number: KR101915066B1
Application number: KR1020177008354A
Authority: KR
Inventors: 알렉산데르 트레멜; 마르쿠스 지크만
Original assignee: 지멘스 악티엔게젤샤프트
Priority date: 2014-08-29
Filing date: 2015-05-11
Publication date: 2018-11-05
Also published as: US20170306799A1; CN106605042A; EP3140519A1; DE102014217280A1; EP3140519B1; WO2016030029A1; CN106605042B; KR20170044734A

Abstract

The present invention relates to an arrangement and method for operating a steam turbine plant with a hydrothermal treatment plant, the arrangement comprising a first condenser for condensing raw water from the exhaust gas of the steam turbine, an evaporator for operating with raw water and air, A tank for receiving raw water with impurities of increased concentrations, a second condenser downstream of the evaporator, for condensing pure water from the air, a second condenser for operating with purified water, And at least one steam turbine for generating steam.

Description

Technical Field [0001] The present invention relates to a method and arrangement for operating a steam turbine plant with hydrothermal treatment,

The present invention relates to a method and arrangement for operating a steam turbine plant with a thermal water treatment plant for purifying a condensate from an exhaust gas of a steam turbine process, the invention relates to an arrangement.

Steam power plants are a prominent type of power plant for electricity generation. There is a high demand for water quality of the boiler feed water of the water circuit of such power plants. When the boiler feedwater is vaporized by steam, depending on the design, the liquid water is completely converted from the hot surfaces to the gas phase. In this case, all non-volatile boiler feed components are deposited on this hot surface. As a disadvantage, the deposits interfere with heat transfer or cause, for example, mechanical failures of the valves. In addition, many inorganic components of the boiler feedwater cause further increases in the corrosion tendency of the components in the steam circuit. This can lead to stress cracks in the components, particularly those made of steel.

In order to reduce the corrosive properties of the water and / or steam of the steam circuits, various conditioning methods exist. These mainly include alkalization of water and oxygen metering. Both elevated pH and reduced redox potential result in reduced solubility of iron oxide. However, alkalization using solid alkalization agents can not be used in disadvantageous, continuous-flow heaters because the water will be completely vaporized here and the deposits will occur accordingly. Therefore, in this case, ammonia is frequently used as a volatile alkalizing agent.

Various processes are known to eliminate impurities in the boiler feedwater. These methods are generally based on ion exchange. However, ion exchange processes can also act as causes of contamination. The breakdown products of the resin material can be adversely fixed on the dry surfaces of the various components of the heated vapor circuit. In addition, the boiler feedwater may be purified using a reverse osmosis process. However, in reverse osmosis, the high loading of raw water results in a disadvantageously reduced flux in reverse osmosis. In addition, the known methods are also very energy-intensive.

It is an object of the present invention to specify a method and arrangement for the treatment of water for steam circuits, which overcomes the above disadvantages.

The object is achieved by the method according to claim 1 and the arrangement according to claim 9.

A method for operating a steam turbine plant with a hydrothermal treatment plant, according to the present invention, comprises a plurality of steps. First, the steam from the steam turbine plant is condensed to the raw water from the first condenser. At least a portion of the raw water is added to the evaporator along with the carrier gas and mass transfer and heat exchange occur between the raw water and the carrier gas in the evaporator. In the evaporator, raw water and carrier gas are conducted in a counter flow. In this case, the carrier gas is heated in the evaporator, and pure water is taken from the raw water by the carrier gas. The raw water is cooled and impurities, especially non-volatile impurities, are concentrated in the raw water. Raw water with concentrated impurities is collected in a downstream tank of the evaporator. The carrier gas loaded with pure water is conducted to the second condenser. In the second condenser, the purified water is condensed from the carrier gas and the second condenser is cooled using the raw water from the tank. The purified water is then recycled to the vapor circuit. The preheated raw water in the second condenser is conducted to the first heater and heat is transferred to the preheated raw water from the steam turbine plant or steam circuit. The preheated raw water is then conducted from the heater to the evaporator.

Arrangement for operation of a steam turbine plant with a hydrothermal treatment plant includes a first condenser for condensing steam from a steam turbine plant to form raw water. In addition, the arrangement includes an evaporator for operating with raw water and carrier gas, and mass transfer and heat exchange take place in the evaporator. In addition, the arrangement includes a tank for collecting raw water enriched with contaminants. The arrangement further comprises a second condenser downstream of the evaporator for condensing pure water from the carrier gas. The arrangement also includes at least one steam turbine for operating with at least a portion of the purified water.

The method and arrangement according to the present invention preferably also utilizes components of the exhaust gas of the steam turbine, in particular steam, as well as heat from the steam turbine process and the steam circuit, in particular from the steam generator. Evaporation of the raw water from the exhaust gas of the steam turbine operates by the principle of forced convection. The second condenser cooled by the raw water advantageously ensures the recovery of the heat of evaporation. The water and carrier gas are advantageously conducted in reverse flow through the evaporator. In this case, the temperature of the carrier gas is increased during the backwash process, while the temperature of the raw water is lowered. At the height of the evaporator or stage, the air temperature is lower than the temperature of the raw water. Advantageously, by coupling the heat streams, a low electrical energy demand of the cleanup process of the boiler feedwater of the steam turbine and low operating costs are achieved. In addition, irrespective of the quality of the raw water, it is possible, using the method, to obtain purified demineralized water of non-volatile components as a product with constant product quality. Advantageously, the heat only needs to be provided at a low temperature level. Water treatment succeeds in virtually no additional electrical energy input. The required thermal energy is advantageously taken from the steam turbine plant or steam circuit. The steam circuit typically includes at least one steam generator, a plurality of condensers and a heater.

In an advantageous refinement of the present invention, the raw water comprises ammonia as a conditioning agent for the boiler feedwater for the steam turbine process. In addition, the pH of the raw water is adjusted to be acidic upstream of the evaporator in such a way that ammonia in the evaporator remains in the raw water. Ammonia itself is a very volatile component. Ammonia in water can be conditioned in such a way that ammonia is present as an ammonium ion. This is the case for lower pHs below at least one pH unit than the pKa value for ammonia at 9.2. When ammonia is present in hydrolyzed water as an ammonium ion, ammonia loses its volatility. As a result, since ammonia is not converted into a gas phase, ammonia can be separated from the evaporator.

In order to influence the corrosive properties of water, it is likewise conceivable that ammonia should be present in the water after purification. In this advantageous refinement of the present invention, the pH is chosen to be high enough to exceed the pKa of ammonia, which is very volatile and can be delivered simultaneously with the carrier gas, and thus can be recovered in the condenser with purified water. In this case, the previously conditioned water is available as a boiler feedwater.

In an embodiment of the invention, fresh raw water may be added to the tank. The raw water is, in particular, water from the condensation of the exhaust gas of the steam turbine. Raw water may also be river water, seawater or wastewater, or may originate from additional water sources. Due to the evaporation process, it is also possible to use highly polluted wastewater. In this way, more and more water can be supplied to the process, depending on the amount of raw water resulting from the condensation of the exhaust gas of the steam turbine.

In a further embodiment of the present invention, the temperature of the raw water of the evaporator is between 60 캜 and 100 캜. Because of this low temperature level, it is advantageously possible to heat the raw water only by the waste heat of the steam circuit, in particular the steam generator, or the exhaust gas of the steam turbine. This is advantageously very energy-saving.

In a further advantageous embodiment of the invention, the heater is operated using the heat of the exhaust gas of the steam generator of the steam turbine process. Therefore, the water treatment advantageously succeeds in virtually no additional electrical energy input. The required thermal energy is advantageously recovered completely from the exhaust of the steam circuit or steam turbine process.

In a further embodiment of the invention, the evaporator is a falling-film evaporator or a trickle-flow evaporator. For these evaporator embodiments, advantageously the carrier gas, especially the interface between air and raw water, is particularly high to allow mass transfer and heat transfer. Typically, the carrier gas is conducted from the bottom to the top, and the raw water is conducted from the top to the bottom.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described on the basis of an exemplary embodiment with reference to the accompanying drawings. In the drawings:
1 shows an arrangement with a steam circuit, turbine, condensers and hydrothermal treatment;
Figure 2 shows a hydrothermal treatment arrangement with an evaporator and a condenser.

Figure 1 shows an arrangement 1 in which a steam turbine power plant is coupled to a hydrothermal treatment arrangement 5. By way of example, in Figure 1, only one turbine stage 2 is shown. The steam generator generates new steam 7 from the boiler feedwater 14 using a heat supply 12, typically an external heat source. The new steam 7 is then transferred to the turbine 2 for power generation. The exhaust gas formed in the steam generator is delivered to the heater, which heats the raw water in the hydrothermal treatment arrangement (5). The steam 8 leaves the turbine 2 and then is condensed in the first condenser 3 to form the condensate 9. A part of the condensate (9) is transferred to the hydrothermal treatment (5) as raw water. Conducting all of the condensate 9 to the hydrothermal treatment 5 is likewise possible. In the case of hydrothermal treatment (5), new raw water may also be added from another external source. This may be, for example, seawater or river water. After the water treatment (5), raw water (19), which has been condensed with contaminants, leaves the hydrothermal treatment arrangement (5). In addition, the purified water 22 leaves the hydrothermal treatment arrangement 5. Then, the boiler feedwater 14 is supplied to the steam generator in turn. Depending on the degree of contamination of the steam 8 or the condensate 9 the purified portion of the boiler feedwater 14 may be mixed with the uncleaned portion of the condensate 9 to form the boiler feedwater 14 have.

In addition, heat is taken to heat the heater at various points of the steam circuit in the case of a plurality of turbine stages, and also between the stages, when the heat of the exhaust gas is insufficient after the steam generation in the steam generator .

2 shows the hydrothermal treatment arrangement 5 in detail. The core part of the hydrothermal treatment arrangement 5 is an evaporator. In this example, a trickle-flow evaporator is used in particular. In this case, the raw water to be purified flows from top to bottom through a structured evaporator packing. Air 13 as the carrier gas is conducted from the bottom to the top via the trickle-flow evaporator. The temperatures of the trickle-flow evaporator range from 60 ° C to 100 ° C. Trickle-flow evaporators operate by convectively supported evaporation of water. The pure water evaporates into the convectively air 13, and then the pure water is again condensed in the second condenser 17 and is again conducted as the clean water 22 to the steam generator. The second condenser 17 is cooled using raw water. The already-heated raw water is then conducted through a heater to bring the raw water to the temperature required in the trickle-flow evaporator. The raw water is then trickled onto the appropriate evaporator material. The materials used are, in particular,

To

Or structured packings made of plastic, metal or cellulose having a specific surface area of at least about 10 microns.

The trickle-flow evaporator is operated in counter flow. This means that the temperature of the raw water flowing downward is reduced towards the bottom of the top of the trickle-flow evaporator because energy is recovered from the water by evaporation and air heating. In contrast, the temperature of the backwash air is increased from the lowermost portion to the top portion of the trickle-flow evaporator. At the separation stage, i.e. at the height in the trickle-flow evaporator, the temperature of the air is always kept lower than the temperature of the raw water. Thereby, the heat transfer proceeds from the descending water to the rising air and, corresponding to the rising temperature, the air can take more steam in the upper area of the trickle-flow evaporator. Raw water 19, which is condensed with contaminants, is partially filled into the tank for storage and, in part, is transported out of the system. Depending on the requirements of the boiler feedwater 14 and the quality of the enriched raw water 19, the tank is filled with fresh raw water. The new raw water may on the one hand be the condensate from the turbine 2, but on the other hand it may also be water from other sources such as, for example, wastewater from river water, seawater or sewage treatment plants. The advantage of the evaporation method used is that even very polluted wastewater can be treated.

The boiler feedwater 14 is typically conditioned upstream of the steam generation for operation of the steam turbine in such a manner that the corrosion tendency is reduced. This occurs, for example, with the addition of volatile alkalizing agents, especially ammonia. Typical ammonia concentrations are determined according to procedures,

To

(With phosphate) or

(No phosphate addition). However, ammonia can eventually cause corrosion in the presence of external ions such as phosphate at excessive concentrations, especially due to the formation of ammonia salts in the heated vapor circuit. Therefore, according to the procedure, it may be necessary to remove ammonia from the system of hydrothermal treatment arrangement 5. Ammonia is a volatile component and will be converted from the trickle-flow evaporator to the gas phase, without contaminating the raw water, thereby contaminating the purified water. To prevent this, the pH of the raw water is adjusted in such a way that it is at least one pH unit below the pKa of ammonia of 9.2. In this pH range, ammonia is present in water as the ammonium ion. Ammonium ions are hydrolyzed and consequently less volatile. Therefore, in the trickle-flow evaporator, this leaves the raw water 19 concentrated in the trickle-flow evaporator, not in the gas phase. Ammonia can then be added back to the boiler feedwater 14 at the desired concentration.

If ammonia is not removed from the raw water, a pH of at least one pH unit higher than the pKa of 9.2 may be selected. Thus, the ammonia can be conducted to the second condenser 17 together with the air 21 to which the purified water is loaded. The water can be recirculated directly to the steam circuit of the turbine 2 as a conditioned boiler feedwater 14. However, in this mode of operation, the ammonia is concentrated due to its high vapor pressure in the condensation of the water treatment plant.

The need to remove ammonia depends on several factors. First, the type of boiler feedwater conditioning is important. It should be noted that if the ammonia concentration is limited, as shown in Figure 1, a portion of the condensate 9 downstream of the turbine 2 is again conducted directly to the steam generator. If part of the condensate 9 is directly con- ducted to the steam generator without treatment, the purification also depends on the proportion of the amount of condensate 9 to the amount of raw water used. This uncleaned condensate (9) contains ammonia at a defined concentration. Depending on the concentration, in the hydrothermal treatment 5, the ammonia has to be correspondingly reduced in order to set the desired ammonia concentration in the boiler feedwater 14.

If ammonia is not completely removed from the raw water, but is not completely left in the raw water or even concentrated,

There is a possibility that the desired ammonia concentration can be set by the corresponding selection of the pH within the range of.

Claims

CLAIMS 1. A method for operating a steam turbine plant with a thermal water treatment plant,
Condensing the steam from the steam turbine plant into raw water from a first condenser,
Adding at least a portion of the raw water and a carrier gas to the evaporator, wherein mass transfer and heat exchange occur between the raw water and the carrier gas in the evaporator,
Conducting the raw water and the carrier gas counterflow in the evaporator wherein the carrier gas is heated in the evaporator and takes pure water from the raw water and the raw water is cooled And the pollutants are concentrated -
Collecting said raw water with contaminants concentrated in the downstream of said evaporator in a tank,
Conducting the carrier gas loaded with pure water into a second condenser,
Condensing the purified water from the carrier gas in the second condenser, the second condenser being cooled by the raw water from the tank,
Conducting the purified water to a vapor circuit of the steam turbine plant,
Conducting preheated raw water from the second condenser to a first heater, wherein heat from the steam turbine plant or the steam circuit is transferred to the preheated raw water,
And conducting said preheated raw water from said heater to said evaporator,
A method for operating a steam turbine plant with a hydrothermal treatment plant.

The method according to claim 1,
Said raw water comprising ammonia, and
Wherein the pH of the raw water is adjusted to be acidic in such a manner that ammonia in the evaporator remains in the raw water,
A method for operating a steam turbine plant with a hydrothermal treatment plant.

The method according to claim 1,
Said raw water comprising ammonia, and
Wherein the pH of the raw water is adjusted to a basic level in such a manner that the ammonia is transferred to the carrier gas,
A method for operating a steam turbine plant with a hydrothermal treatment plant.

4. The method according to any one of claims 1 to 3,
Fresh fresh water is added to the tank,
A method for operating a steam turbine plant with a hydrothermal treatment plant.

5. The method of claim 4,
Wherein the new raw water is condensate water from the exhaust gas of the steam turbine, river water, seawater or wastewater,
A method for operating a steam turbine plant with a hydrothermal treatment plant.

4. The method according to any one of claims 1 to 3,
Wherein the temperature of the raw water in the evaporator is in the range of < RTI ID = 0.0 > 60 C < / RTI &
A method for operating a steam turbine plant with a hydrothermal treatment plant.

4. The method according to any one of claims 1 to 3,
Wherein the heater is operated by using the heat of the exhaust gas of the steam generator of the steam circuit,
A method for operating a steam turbine plant with a hydrothermal treatment plant.

4. The method according to any one of claims 1 to 3,
Air is used as the carrier gas,
A method for operating a steam turbine plant with a hydrothermal treatment plant.

An arrangement for operating a steam turbine plant with a hydrothermal treatment plant,
A first condenser for condensing steam from the steam turbine plant into raw water,
An evaporator for operating using raw water and a carrier gas, wherein mass transfer and heat exchange occur in the evaporator,
A tank for collecting raw water enriched with contaminants,
A second condenser downstream of said evaporator for condensing pure water from said carrier gas,
And at least one steam turbine for operating with at least a portion of the purified water,
An arrangement for operating a steam turbine plant with a hydrothermal treatment plant.

10. The method of claim 9,
Wherein the evaporator is a falling-film evaporator or a trickle-flow evaporator,
An arrangement for operating a steam turbine plant with a hydrothermal treatment plant.