DE3607210A1 - Steam generator with NOx reduction installation - Google Patents

Abstract

Fossil-fuelled steam generator with downstream NOx reduction installation, in which the smoke gas temperature can be influenced by the steam-heated feed-water preheating installation.

Description

Steam generator with NOx reduction system

x Description: For the NOx reduction of the smoke gases, certain Minimum temperatures in the reduction system are observed.

In the case of fossil-fired steam generators, however, it sinks in the low-load range the flue gas temperature below the required minimum value.

There are therefore technical measures to comply with these Minimum temperature to be met at low loads.

In order to achieve this, it is suggested that the operationally existing, to use steam-heated feed water preheater for this purpose.

According to the example according to circuit diagram 1, a, through its operational design data of suitable feedwater preheater 4 selected. in the This preheater is low-load by opening the reducing valve 9 from its normal operational steam supply.

Due to the increase in pressure in the feedwater preheater 4, the non-return valve closes 21 automatic. Then slide 11 can also be closed.

When supplying steam to the feedwater preheater 4 from the high-pressure system of the system, steam cooling will also be required in most cases, which can take place via an injection valve 11.

The pressure in the feed water preheater 4 is increased.

This increases the final preheating of the feed water. As a further consequence the result is that the heat consumption of the economizer 5 drops and thus the flue gas temperature Before the NOx reduction system 16 rises, or there will be a further decrease in the flue gas temperature prevented at low load.

Due to the increase in pressure in the feedwater preheater 4, it is still there possible, also from this subsystem via a withdrawal 18 in the low-load range To supply consumers that require a higher operating pressure, e.g. B.

Oil atomizer.

When the steam generator output increases, the slide is opened 11 and closing the reducing valve 9 reversed the measure.

When the system starts cold, the reducing valve 9 can be used to warm the Main steam line up to directly in front of turbine 12 or steam consumer makes sense can be used. The condensate that forms when the main steam line is heated is discharged via the drainage valves 8, while the overheating through the steam is introduced, which via the reducing valve 9 for regenerative feed water preheating is being used. This reduces start-up losses.

To protect the feed water preheater against excessively high pressure or If the temperature is too high, it makes sense to take measures for safe closing of the reducing valve 9 to be provided. It is also suggested for valve leaks to install a safety valve 20.

State of the art: The task has not been long because of the used NO reduction technology in the low-load range relatively new. So far have been Measures mainly discussed and examined on the steam generator itself. The problem up to now, the flue gas temperature support has been provided by a separate circulating pump and on the feed water side Bypassing the economizer or bypassing the economizer on the flue gas side or flue gas recirculation or additional burner detached in front of the NOx reduction system.

All of these measures require a correspondingly high investment cost with system-specific fault possibilities and maintenance effort.

According to the invention, the task should therefore be operationally simpler and cheaper by using existing feed water preheaters and a steam reduction station be solved.

Exemplary embodiment: Circuit diagram 1 shows a typical thermal circuit diagram for a condensing power plant, like the feed water temperature upstream of the economiser 5 can be increased at low load. By opening the reducing valve 9 closes the check valve 21 automatically. The feed water preheater 4 is already there separated from the cold reheater line. The slide 11 can also getting closed.

When the load increases, the reducing valve 9 is closed and the non-return valve 11 opens automatically when slide 11 has been opened.

In circuit diagram 1: 1 - low pressure preheater 2 - feed water tank 3, 4 - high pressure preheater 5 - flue gas heated economiser 6 - evaporator 7 - HP - [) superheater 8th - Drainage valve for heating 9 - Steam reducing valve 10 - Injection water valve 11 - Gate valve 12 - HP turbine 13 - MD turbine 14 - LP turbine 15 - condenser 16 - NOx reduction system 17 - Air preheater 18 - Extraction for auxiliary steam consumers at low load 19 - reheater 20 - safety valve for leakage steam 21 - Non-return valve 22 - Reducing station from HD to CLOSED.

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Claims (3)

Protection claims 1. Fossil-fired steam generator with NOx reduction system characterized in that a steam-heated one to maintain the minimum flue gas temperature Feed water preheater disconnected from its normal operational steam supply and is supplied with high pressure steam via a reducing valve. 2. Steam generator with downstream consumer characterized in that that the steam reducing valve according to claim 1 for heating the high pressure line during Start-up is used. 3. Steam generator according to claim 1, characterized in that in the low load range other consumers can also be supplied via the reducing valve.