Water-injected compressor arrangement

Description

The subject of the invention is a water injection air compressor arrangement, in which a water circuit is connected to at least one engine-driven compressor arranged between the suction line and the compressed air line, which water circuit includes a water separator connected to the compressed air line, a return line connected at the bottom of the water separator, a water quantity meter, and a conductivity meter and which has a supply line through a reverse osmosis filter and fitted with a valve. In such air compressor arrangements, water is circulated in the compressor, which cools and lubricates the moving parts of the compressor and seals the joints. Depending on the moisture content and temperature of the transported air, each compressor consumes water or separates excess water from the transported air. It is necessary to replace the water in the water circuit through the compressor or to drain the excess water. The water fed into the water circuit must be clean, it is important that it has a relatively low mineral content in order to avoid scale deposits. However, the mineral content of the water fed into the water cycle cannot be arbitrarily low, because the water absorbs carbon dioxide from the air, which cannot be absorbed by water with a very low mineral content, so it turns into carbonic acid, which causes the water's pH value to be low , the free carbonic acid in it is corrosive. The degree of corrosiveness of water can be measured by measuring the conductivity of water. Water with a conductivity between 10-20 pS / cm at a temperature of 25 °C is not considered corrosive. Distilling water is too expensive a process to soften water, so water is usually softened (reduces its mineral content) locally before feeding it to the compressor. Such an air compressor arrangement with a water softening device is described in publication WO-A-99 / 02863. The water softening device includes a reverse osmosis filter and an ion exchanger. The water softening device can be connected to it via valves, optionally to the supply line or to a line bridging the water circuit. The water quality of the water source does not significantly affect the lifetime of the reverse osmosis filter, but it does significantly affect the efficiency of the filtration. Poor water quality results in low filtered water and high levels of mineral concentrate. The reverse osmosis filter is not really suitable for reducing the conductivity of the water in the water circuit. Most of the water content of the water circuit must be removed from the water circuit as a concentrate, and the removed concentrate must be replaced with fresh water. The electrical conductivity of fresh, untreated water is relatively high, and this again should be reduced by the reverse osmosis filter. If an ion exchanger is used instead of a reverse osmosis filter, it is not a much better solution either. The ion exchanger is excellent for reducing conductivity, but its service life is significantly shortened if it is used to treat poor quality water. Our goal with the solution is to eliminate the mentioned shortcomings of the known solutions, by creating a water injection air compressor arrangement that is suitable for protecting the filters and ensuring a long service life, as well as ensuring adequate water quality for the operation of the compressor. The solution to the problem according to the invention is a water injection air compressor arrangement, in which a water circuit is connected to one or more engine-driven compressors arranged between a suction line and a compressed air line, which water circuit includes a water separator connected to the compressed air line, a return line connected at the bottom of the water separator and a water volume meter, and includes a conductivity meter and has a valved feed line through a reverse osmosis filter, where the water circuit has a bypass line incorporating an ion exchanger and valve, where the feed line valve is controlled by the water flow meter and the bypass line valve is controlled by the conductivity meter . Preferably, the water circuit has a line connecting the return line and the suction line, bridging the compressor. Ideally, the conductivity meter is arranged in the return line. A water source is preferably connected to the suction line. Ideally, the water volume meter of the water circuit is a level meter arranged in or connected to the water separator. A water source pump is preferably connected to the section before the reverse osmosis filter in the supply line. Ideally, a water source descaler is connected to the section before the reverse osmosis filter. Preferably, the water circuit has a drain line equipped with a valve controlled by a water flow meter. Ideally, the drain line is connected to the water separator. The essence of the invention is described in detail below, based on a drawing of an exemplary embodiment. The block diagram of the water injection air compressor arrangement according to the invention is shown in the drawing. We note that the "lines" mentioned in the description and claims may in practice be implemented as pipelines. Compressor 1 according to the example is a water injection air compressor (displacement compressor), for example a single or multi-screw compressor. 3 air filters are installed in the suction line 2 of the 1 compressor driven by 5 motors, and 7 water separators are connected to the 4 compressed air lines of the 1 compressor. The compressor 1 is also included in a water circuit 6, which includes the water separator 7, which also serves as a buffer air tank. The main circuit of the water circuit 6 is closed through the compressor 1, the compressed air line 4, the water separator 7 and the return line 8. The return line 8 leads back from the bottom of the water separator 7 from the compressed air HU 225 367 Β1 separated water, mainly into the internal injector of compressor 1. 9 water coolers are installed in the 8 return lines. A secondary water cooler 10 and a secondary water separator 11 are installed in the outgoing compressed air line of the water separator 7, in order to extract the remaining water. The return line 12 of the secondary water separator (secondary) is connected to the suction line 2 of the compressor 1. As mentioned in the description of the state of the art, compressors, depending on the moisture content and temperature of the air drawn in on the 2 suction lines, consume water or separate excess water from the delivered air. In order to drain the excess water, a drain line 13 closed by a controllable valve 14 is connected to the water circuit 6, preferably to the lower part of the water separator 7. The drain line 13 can also be connected at another point of the water circuit 6, for example, it can be connected downstream to the pipe section after the water cooler 9. To replace the missing water from the water source 15, another controllable supply line 16 closed by a two-way valve 18 is used, which is not connected directly to the water circuit 6, but, like the secondary return line 12, to the suction line 2. A reverse osmosis filter 17 is installed in the feed line 16. Concentrate line 19 is used to drain the concentrate produced in reverse osmosis filter 17, and the filtered water is sent to suction line 2 on supply line 16. The water volume meter 20 arranged in the water separator 7 opens the valve 14 of the drain line 13 to drain excess water, and the valve 18 of the supply line 16 to replace the missing water in the water circuit 6. The water quantity meter 20 is preferably a float level meter measuring the water level in the water separator 7. The term "measurement" is used in a broad sense, because it is not necessary to quantify the measured values, it is sufficient to establish whether the measured value is within a prescribed value or range, or deviates from it upwards or downwards. In the case of the 20 water volume meters, this prescribed value is the minimum permissible water level. The water quantity meter 20 preferably also detects the exceeding of a permissible maximum water level, and then opens the valve 14 and then closes it when the exceeding ceases. In the example, the water quantity meter 20 is implemented with at least two level detectors. According to the invention, the compressor 1 is bridged between the air intake line 2 and the water injection inlet by a bridging line 21, which is connected to the return line 8, after the water cooler 9. An ion exchanger 22 and a valve 23 are arranged in the bypass line 21. The output of a conductivity meter 24 is connected to the control input of the valve 23, which opens the bypass line 21 in case of too high conductivity. If the water quantity meter 20 detects a lack of water in the water circuit 6, it opens the supply valve 18, and if there is enough water in the water circuit 6, it closes the valve 18. The freshly fed water is cleaned of its mineral content by 17 reverse osmosis filters. If the conductivity meter 24 measures too high a conductivity value in the water of the water circuit 6, it opens the valve 23 of the bypass line 21 and lets part of the water through the ion exchanger 22. The deionized water enters the compressor 1 directly through the suction line 2. This does not cause water loss in the 6 water circuits, so it does not require water supply. Since the mineral content of the water entering the ion exchanger 22 is significantly lower than that of fresh water, the conductivity of the water only needs to be reduced slightly, so the strain on the ion exchanger is small, so its service life will be relatively long. The ion exchanger 22 is not burdened with cleaning the fresh water supplied to make up for the deficiency, because this is done by the reverse osmosis filter 17, which is installed in a place where it is not disturbing if there is a lot of water enriched in separated minerals that does not enter the water circuit 6. The reverse osmosis filter 17 can therefore be operated under optimal conditions. The water source 15 can be part of a pressure booster pump 25, which is connected to the section before the reverse osmosis filter 17 of the supply line 16. The reverse pressure difference (osmotic pressure) that occurs on the membrane of the reverse osmosis filter 17 can be compensated with the pump 25. The pressure of a relatively low-pressure water supply network may sometimes be insufficient to overcome the osmotic pressure of the reverse osmosis filter 17. In the section before the reverse osmosis filter 17 of the supply line 16, a descaling agent 26 can also preferably be inserted. 80% of the mineral content (calcium salts and magnesium salts) must be removed from a hard, fresh water. A first descaler 26 is suitable for this, which effectively reduces the use of the reverse osmosis filter 17 and increases its efficiency. The descaler 26 forms, for example, a unit with the pump 25 and is arranged upstream of the pump 25. The compressor 1 can be not only the screw compressor mentioned in the example, it can also be, for example, a gear compressor, a spiral compressor or a compressor with a single screw rotor.

Claims

PATENT CLAIMS 1. Water injection air compressor arrangement, in which a water circuit (6) is connected to a compressor (1) driven by a motor (5) arranged between a suction line (2) and a compressed air line (4), which water circuit (6) includes a water separator (7) connected to the compressed air line (4), a return line (8) connected at the bottom of the water separator (7) and a water flow meter (20), as well as a conductivity meter (24), and which has a supply line (16) led through a reverse osmosis filter (17) and equipped with a valve (18), characterized in that the water circuit (6) has a bypass line (21) in which an ion exchanger (22) and a valve (23) are installed, where the valve (18) of the HU 225 367 Β1 supply line (16) is by a water flow meter (20) and the valve (23) of the bypass line (21) is controlled by the conductivity meter.

2. Air compressor arrangement according to claim 1, characterized in that the water circuit (6) has a line (21) connecting the return line (8) and the suction line (2) and bypassing the compressor (1).

3. Air compressor arrangement according to claim 1 or 2, characterized in that the conductivity meter (24) is arranged in the return line (8).

4. An air compressor arrangement according to any one of claims 1-3, characterized in that a water source (15) is connected to the suction line (2).

5. Air compressor arrangement according to any one of claims 1-4, characterized in that the water volume meter (20) of the water circuit (6) is a level meter arranged in or connected to the water separator (7).

6. An air compressor arrangement according to any one of claims 1-5, characterized in that a pump (25) of a water source (15) is connected to the section of the supply line (16) before the reverse osmosis filter (17).

7. An air compressor arrangement according to any one of claims 1-6, characterized in that a water source (15) descaler (26) is connected to the section of the supply line (16) before the reverse osmosis filter (17).

8. Air compressor arrangement according to any one of claims 1-7, characterized in that the water circuit (6) has a drain line (13) provided with a valve (14) controlled by the water flow meter (20).

9. Air compressor arrangement according to claim 8, characterized in that the drain line (13) is connected to the water separator (7).