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[Technology Sharing] Analysis of the impact of condensate recovery on water balance

shengxing

Introduction

Before the condensate recovery device is debugged and put into use, the condensate water of each production device is collected and replenished to the circulating water system by the heat medium water system. After the condensate recovery device is put into use, the condensate part is added to the desalination tank of the deoxygenation water station after advanced treatment. The amount of supplementary desalted water in deoxygenated water station was obviously reduced, and the load of external desalted water was greatly reduced. The low load operation of reclaimed water reuse and the decrease of flow rate of double membrane system are not conducive to the long period operation of double membrane system. At the same time, the fresh water use rate of reclaimed water reuse device and original desalination device is compared synthetically, and the economic benefit of water production by using original desalination device is better.

I. Comparison of the yield of reclaimed water reuse and original desalted water station

The raw water of the original desalination station uses fresh water, and the water production is 45~48 t/h to meet the water demand of the plant. The operation data are shown in Table 1.

 Influent flow

Flow of water

 Concentrated displacement

Water recovery rate

 66 t/h

 48 t/h

 18 t/h

 72.7%

During the operation of the reclaimed water reuse device, in order to ensure that the raw water quality is within the design index, the raw water is mixed with the reclaimed water by fresh water. The feed conductivity is controlled at μs/cm.1700~1800 The conductivity of water and electricity in China :3100~3500μs/cm, fresh water conductivity 650~700. During the operation of the reclaimed water reuse device, the ultrafiltration membrane and reverse osmosis membrane must be washed and washed regularly in order to prevent blockage. The washing water quantity is 1.5~2 times of the water production flow rate, and the water production is consumed by itself, resulting in the lower overall water collection rate. The data during the operation of reclaimed water reuse are shown in Table 2.

Table 2 Operational Data Sheet for Water Reuse

Total water intake

120~140t/h

Reverse osmosis concentration

20~25t/h

 Ultrafiltration Water

110~125t/h

 Reverse osmosis water recovery rate

76%

 Ultrafiltration concentration

7~10t/h

 Total yield

65%

 Reverse osmosis water

75~90t/h

 

 

The fresh water consumption of the original desalination system is 65~70 t/h, and the fresh water consumption of the reclaimed water is 75~85. The fresh water consumption of the reclaimed water reuse is slightly larger than that of the original desalination system. Considering the amount of fresh water, it is economical and reasonable to use the original desalted water system to supply desalted water on the premise of satisfying the amount of desalted water in the device.

I. Operating conditions of the condensate recovery unit

Condensate recovery unit commissioning, water production index qualified. At present, the condensate water intake Flowmeter is not accurate. By changing the quantity of desalted water from reclaimed water before and after putting into use, it can be judged that the condensate water recovery has reached 35 t/h. The water quality after condensate recovery is shown in Table 3.

Oil content

<1mg/L

Total hardness

≤3µmol/L

 Iron

≤50µg/L

 Electrical conductivity

≤0.2µs/cm

Condensate recovery pretreatment needs cooling, that is, heat transfer with desalted water from desalted water tank, deoiling and iron removal before entering desalted water tank. The operating load of deaerator in deaerator station is about 30%, the load is low, the amount of desalting water in deaerator is about 50~60 t/h. The current condensate enters the plate heat exchanger before the temperature 90~100℃, the desalted water temperature 25℃, if the condensate is recovered, then enters the condensate fine treatment

The temperature of the section will exceed 60℃. With the increase of condensate recovery, the temperature in desalted water tank will also rise, so the heat balance state should be considered in condensate recovery.

The condensate recovery positive bed resin is 001×7 resin, the mixed bed resin is 001×7 MB and 201,7 MB resin, all of which are styrene gel resin. Styrene strong acid resin can withstand 120℃ in a short time, styrene strong base resin can withstand 60℃. If the normal operating temperature of styrene gel resin is less than 45℃, it is appropriate. Especially for anionic resins, such as more than 45℃, the degradation rate of resin is greatly increased, which reduces the service life of resin and affects the volume exchange capacity. Therefore, the maximum temperature index of condensate recovery unit is not more than 45℃, and the operating temperature has reached 44℃.

In view of the high temperature before the condensate is recovered into the resin adsorber, which affects the stability of the resin adsorberTitle. Through the technical reform measures, the condensate water and circulating water heat exchanger are added before the condensate enters the resin adsorber, reduce the condensate recovery temperature and achieve the purpose of all condensate recovery and utilization.

I. Full utilization of reclaimed water reuse systems

After most of the condensate is recovered as desalted water, the amount of fresh water replenished by circulating water increases greatly. At present, the amount of water replenished by circulating water system ~900 tons / day. Because the water source changes greatly, the circulating water quality changes greatly. Mainly reflected in the PH value rise, concentration multiple increase, alkalinity increase and so on.

In order to reduce the amount of fresh water, it is proposed that all reclaimed raw water should be used in reclaimed water, and from reverse osmosis water production tank to circulating water system.

1) water reuse all use clear water pool effluent;