FR2648055A1 - Improvement of the drying of gases by refrigeration method with variable dew point - Google Patents

Abstract

The subject of the present invention is the improvement of the drying of gases by refrigeration method with variable dew point. It consists of the combination first of a refrigerating machine consisting of a compressor 3 and a condenser 4 with a fan 5, capable of functioning with evaporation at less than 0 DEG C and regulated by a simple pressure-sensitive switch (pressostat) 22 situated on the return circuit 23 of the evaporator, periodically stopping the compressor 3 in the cold period, and next of an evaporator connected to the cold generator, formed by a bank of finned pipelines 6 and situated in a closed chamber 8 provided with baffles (chicanes) 9 and with a droplet separator 10 in which the gas to be treated is cooled in contact with the fins, and finally of an economiser 2 which the gas passes through before and after its passage into the evaporator, and which is also composed of a chamber 11 with baffles 12 and a droplet separator 13 containing a bank of finned tubes 14. It is intended in particular for equipping industrial installations for producing compressed air or gas.

Description

IMPROVED DRYING OF GASES BY REFRIGERATION PROCESS A
VARIABLE DEW POINT
The object of the present invention is to improve the drying of gases by a variable dew point refrigeration process.

It is intended in particular for the equipment of industrial installations for the production of compressed air or gas.

The devices produced to date for the drying of gases and compressed air by refrigeration work with a system of thermal regulation imposing a dew point greater than or equal to +2 C, whatever the temperature, the flow of the gas to be treated on entry and external conditions.

In industrial compressed air production systems, the distribution pipes frequently pass through unheated premises.

Consequently, a sufficient installation in summer will not be able to completely dry the gas in winter, which risks leading to blockage of the pipes by freezing. It is necessary to have recourse to a system of drying by absorption, expensive solution to the purchase and the use and moreover, generating of high pressure losses.

The device according to the present invention eliminates all these drawbacks. Indeed, it makes it possible to carry out gas drying installations in the cold with a negative dew point in winter while using an installation whose dimensions and power correspond to those required in summer. Indeed, the air temperature at the inlet of the dryer is generally +350 C or more in summer, but in winter it is possible to lower this temperature to around +20 C, which considerably reduces the power required , on the other hand, the refrigerating machine which condensed at + LO / L50 C can condense at +30 C, hence an increase in cooling capacity. These two facts mean that an installation calculated in summer for a dew point of + 4 C can reach a point in winter. dew -100 C.

All the devices are apparently conventional, but the exchange surfaces are designed to accept a deposit of ice.

The all or nothing regulation allows the compressor to stop on accumulation of ice. This device allows in all cases to automatically give the best achievable dew point.

it is made up by the combination first of all, of a refrigerating machine made up of a compressor and a condenser with fan, being able to function with an evaporation lower than 0 C and regulated by a simple pressure switch located on circuit of return of l '' evaporator periodically stopping the compressor in cold period, then of an evaporator connected to the refrigeration generator, formed of a battery of finned pipes, and located in a closed enclosure provided with baffles and a droplet separator in which the gas to be treated cools in contact with the fins, finally, an economizer that the gas crosses before and after its passage in the evaporator and also composed of an enclosure with baffles and droplet separator containing a battery of finned tubes.

The detailed description below closely relates to a nonlimiting example of one of the embodiments of the object of the invention and refers to the attached schematic drawing.

The device consists of an evaporator I, an economizer 2 and a refrigeration unit essentially comprising a compressor 3, a condenser 4 cooled by a fan 5, or by water.

The evaporator 1 is composed of a battery of pipes provided with fins 6 designed to withstand without inconvenience periodic icing, in which the refrigerant from the compressor 3 expands after passing through a thermostatic expansion valve 7, said battery being contained in an enclosure 8, equipped with baffles 9 and a droplet separator 10, in which the gas to be treated circulates in contact with the fins.

The structure of the economizer is similar. It consists of an enclosure 11, with baffles 12 and droplet separator 13.

Finned pipes 14 pass through said enclosure lengthwise. It is possible to place a heater 15 at the outlet of the economiser, because the rise in temperature increases safety in cold weather and also increases the volume of compressed air. This heater can be a pre-condenser of the refrigeration unit or an electrical resistance. It can be incorporated into the economizer.

The two chambers 8 and 11 are equipped with condensate traps 16 and 17.

The refrigeration unit is completed by a manual valve 18 on the low pressure return circuit, and on the high pressure circuit 24, by another manual valve 19, by a high pressure safety thermostat 20, by a filter drier 21 and a liquid sight glass 28.

The air or gas to be dried enters the economizer 2 according to arrow 25 and passes outside the tubes 14 where it undergoes pre-cooling, for example from 35 to 21 C in summer, and from 20 to 5 C in winter and finds a droplet separator 13 in a woven mattress before entering the evaporator 1 according to arrow 26 where it passes over the outside of the finned coil 9.

There, it cools to the dew point, that is, as an indication from +21 to +3 C in summer, and from +5 to -10 "C in winter. At the outlet of evaporator 1, the gas crosses again a droplet separator 10, before returning to the economizer 2 via the pipe 27, where it will heat by passing against the current inside the tubes 14. The temperatures will be at the outlet of the order of 230 C in summer and 8 C in winter.

The regulation is ensured by a simple pressure switch 22, located on the low pressure circuit 23 and acting on the compressor 3.

In hot periods, at normal flow rate, the compressor 3 operates continuously, the cooling of the gas in the evaporator 1 causing the condensation of the water vapor it contains.

In cold periods, or in the event of a low flow, the treated gas fails to keep the fins of the evaporator at a temperature sufficient to prevent icing. When the ice is deposited on the evaporator, the evaporation decreases to -15 / -180 C, which results in a reduction in the pressure acting on the pressure switch 22 which stops the compressor 3. The temperature of the evaporator 1 goes up, the ice melts and at around +20 C the compressor starts again. For a few tens of seconds, the dew point rises to + L C, which can cause a slight deposit of ice in the pipes, but this spite is minimal and is eliminated by sublimation or by the rise in temperature (night day).

Thanks to the simplicity and the reliability of its regulation system, thanks to its excellent performance in all seasons allowing an economy of investment, the device which has just been described protects itself particularly well to the realization of dehydrators for industrial power stations of production of compressed air of medium or high capacity.

The positioning of the various constituent elements gives this device a maximum of useful effects which had not been obtained to date by similar devices;

Claims (1)

CLAIMS 10 Improvement of gas drying by refrigeration process with variable dew point intended in particular for the equipment of industrial installations for the production of compressed air or gas, characterized by the combination first of all, of a refrigeration machine consisting of '' a compressor (3) and a condenser (4) with fan (5), which can operate with a dew point lower than OC and regulated by a simple pressure switch (22) located on the return circuit (23) of the evaporator and set to periodically stop the compressor (3) during a cold period or in the event of low flow, even in summer, when ice has formed on the fins of the evaporator (1) and the temperature in the latter is dropped below minus 15 C so as to allow the ice to melt and the temperature to rise to about plus 2 o C, the pressure switch (22) then restarting the compressor (3), then an evaporator ( 1) connected to refrigeration generator, formed by a battery of finned pipes (6), and located in a closed enclosure (g) provided with baffles (9) and a droplet separator (10), in which the gas to be treated cools in contact with the fins, finally, an economizer (2) also composed of an enclosure (11) with baffles (12) and droplet separator (13) in which the raw gas undergoes a first cooling before passing through the condenser, the aforesaid enclosure (II) containing a battery of finned tubes (14), which the gas crosses after passing through the condenser (1). 2 Device according to claim 1, characterized in that a heater (15) consisting of an electrical resistance is placed at the outlet of the economizer (2). 3 Device according to claim 2, characterized in that the heater (15) consists of a pre-condenser of the refrigerating machine (3, A, 5). 40 Device according to any one of the preceding claims, characterized in that the heater (15) is incorporated in the economizer (2).