JPS59132988A - Reduction of dissolved oxygen in condensed water - Google Patents

Abstract

PURPOSE:To reduce dissolved oxygen in condensed water within a short time, by circulating condensed water, to which hydrazine has been preadded at the upper stream side of an activated carbon-packed column provided in a recirculation line of condensed water, through the activated carbon column, and then starting a deaeration column. CONSTITUTION:A hydrazine solution 16 in a hydrazine tank 15 is injected through an injection pipe 17 and a valve 19 into condensed water at the upper stream side of an activated carbon-packed column 14 by a pump 18. Dissolved oxygen and hydrazine in the condensed water are reacted with each other by bringing them into contact with activated carbon 13 to reduce said dissolved oxygen, and then the treated water is returned through a valve 20 and a recirculation line 11 of condensed water to a condenser 6. The condensed water 7 in which the dissolved oxygen has been reduced is let flow through a pipe 8, a pump 9, a valve 10, the by-pass pipe 21 of the activated carbon-packed column 14 and a valve 22 to perform the by-pass operation of said activated carbon- packed column 14. By this method, dissolved oxygen in the condensed water can be reduced down to 0.003ppm within a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reducing dissolved oxygen in condensate during startup of a thermal power plant.

Figure 1 shows a conventional method for reducing dissolved oxygen in condensate during startup of a power plant.

In Figure 1, makeup water 2 is stored in makeup water tank 1.
is tube 3. Make-up water pump4. It passes through the valve 5 and is stored in the condenser 6.

The condensate 7 stored in the condenser 6 is transferred to a pipe 9 by a condensate pump 8. A condensate recirculation line 11 in communication with valve 10. Valve 1
It is designed to be circulated to condenser O via 2.

The dissolved oxygen in the circulating condensate is nearly saturated in the exhaust pipe 13. It is difficult to reduce dissolved oxygen by simply evacuating the condenser 6 using the vacuum pump 14. Usually, it is combined with a deaerator (not shown), and the deaerator performs vacuum heating deaeration. The condensate is returned to the condenser 6 and reduced.

In this process, according to conventional results, it takes 5 to 8 hours to reduce dissolved oxygen in the afterwater.

An object of the present invention is to provide a method for eliminating the above-mentioned drawbacks and reducing dissolved oxygen in condensate in a short time at the time of plant startup.

That is, the present invention fills activated carbon in the condensate recirculation line as a method for reducing dissolved oxygen in condensate in a short period of time during startup for weekend shutdowns and daily startup/stop operations in power generation plants. An activated carbon packed tower and a hydrazine injection device are installed, and the hydrazine injection device causes condensate to which hydrazine is added to flow through the activated carbon packed tower, and the activated carbon in the tower adsorbs hydrazine and dissolved oxygen in the condensate. The present invention relates to a method for reducing dissolved oxygen in condensate, which comprises starting a deaerator after reducing the dissolved oxygen concentration in condensate by repeatedly performing the reaction of the following formula (1) in the vicinity. According to the method, the time for degassing condensate can be shortened.

N2H4+ o,, ~ → 2I (20-1-N2...
- (1) Fig. 2 is a diagram showing an embodiment of the method of the present invention. In FIG. 2, the components designated by the same reference numerals as those in FIG. 1 have the same structure and function, so the explanation of these components will be omitted.

In FIG. 2, the hydrazine solution 16 stored in the hydrazine tank 15 is injected into the activated carbon packed tower 1 through the hydrazine injection g17 valve 19 by the hydrazine injection pump 18.
The condensate is injected into the condensate upstream of 4. When the dissolved oxygen and hydrazine in the condensate come into contact with the activated carbon 15, the reaction shown by reaction formula (1) occurs, and after reducing the dissolved oxygen in the condensate, the valve 20. It returns to the condenser O through the condensate recirculation line 11. The make-up water 2 in the make-up water tank 1 also passes through the pipe 3° valve 5 by the make-up water pump 4, and then is injected into the condenser 6 through the same route as above, with dissolved oxygen being reduced.

Condensate 7 with reduced dissolved oxygen is transferred to pipe 8. Condensate pump9.
Valve 10. The activated carbon packed tower 14 can be operated by bypass through the activated carbon packed tower bypass pipe 21 and the valve 22, which are connected to the condensate recirculation line 11.

Note that the activated carbon 16 acts as a catalyst for the reaction of reaction formula (1) as described above, and the adsorbed dissolved oxygen and hydrazine exit from the activated carbon as H20 + N2 through this reaction21. This is different from the action of activated carbon, which adsorbs dissolved oxygen, in the "Method for Reducing Dissolved Oxygen in Condensate" filed at the same time as the present invention.

FIG. 3 is a diagram showing an example of the results of a dissolved oxygen removal test in the addition of hydrazine according to the method of the present invention.

Figure 3 shows the case where condensate containing 4.85 ppm of dissolved oxygen is sent to an activated carbon-packed tower under the conditions of activated carbon loading of 2 t, 5V-5h-'', and hydrazine concentration of 1 equivalent (4.85 ppm). As is clear from the figure, more than 10,000 pieces of condensate containing 0.005 ppm of dissolved oxygen can be collected.

As described above, according to the method of the present invention, hydrazine and dissolved oxygen are continuously concentrated, reacted, and removed in activated carbon, and dissolved oxygen in water is effectively removed. Compared to methods for removing dissolved oxygen in water, it takes a shorter time and reduces dissolved oxygen in condensate by 0.003 pp.
It can be reduced to m.

In the embodiment shown in FIG. 2, the capacity of the water refill type 6 is 20 m', the condensate circulation is 1[]0rn3/hour, and the degassed condensate of 0.01 ppm or less is discharged from the activated carbon packed tower. Estimated assuming that water returns to condenser 6 and is diluted,
Theoretically, the amount should be 0.01 ppm or less in about 80 minutes, and from the above experimental results, this amount can be sufficiently treated with 5V-5h'-' and active return light 'R total 2 om''.

In other words, according to the method of the present invention, it takes 5.5 ppm to reduce dissolved oxygen to 0.01 ppm or less during cleanup at startup.
This shows that it can be achieved in a very short time of about 80 minutes, although it previously required ~8 hours.

[Brief explanation of the drawing]

Figure 1 shows the conventional method for reducing dissolved oxygen in condensate, Figure 2
The figure shows an embodiment of the method of the present invention, and FIG. 6 is a chart showing the results of tests conducted to confirm the effects of the method of the present invention. □ Sub-agents 1) Meifuku agent Ryo Hagiwara -ya

Claims (1)

[Claims] To reduce dissolved oxygen in condensate in a short time when starting up a thermal power plant, hydrazine-added condensate is flowed into the activated carbon column upstream of an activated carbon-packed column that has been installed in advance in the condensate recirculation line. After the dissolved oxygen and hydrazine in the condensate are adsorbed and reacted with activated carbon in the activated carbon-packed tower to reduce the dissolved oxygen in the condensate, a degassing device is started. Dissolved oxygen reduction method.