SU676668A1 - Steam-air mixture heat utilization method - Google Patents

Description

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This invention relates to methods for recovering heat from gaseous emissions, primarily from the solvent emitted from an alkaline pulping process. There is a method of heat recovery of gas emissions from the solvent of the melt of the steam-recovery boiler unit (CPKA), based on the use of heat exchangers {.

The disadvantages of this method are as follows:

heat exchangers have significant resistance to the passage of the vapor-air mixture, and therefore the installation of a fan is required for its transportation;

in case of fluctuations in the amount of a vapor-air mixture, it is necessary to provide for the discharge of its excess before the heat exchanger to the atmosphere;

The operation of the fan in conditions of a corrosive environment and fluctuations in the consumption of a steam-air mixture is associated with great difficulties.

Closest to the present invention is a method of heat recovery of the vapor-air mixture leaving the melt solvent, which involves cooling it in a heat exchanger, transporting it with a fan and returning it back to the melt solvent. To reduce the oxygen content in the air-steam mixture, the vapor-air mixture and flue gases are fed to the melt solvent, after removing a part of the air-steam mixture 2.

However, in this method, there is a gradual accumulation of dust particles in the engine-steam mixture and them; deposition on the heating surfaces of the heat exchanger, fan rotor, as well as pollution of the atmosphere during periodic discharges of the vapor-air mixture. The purpose of the invention is to increase the efficiency of the heat recovery process while simultaneously cleaning the vapor-air mixture.

Set goal Achieved by washing the vapor-air mixture, cooled and condensed using a heat exchanger, in a jet gas washer, after which the mixture can be sent back to the solvent tank and exhausted to the atmosphere directly or mixed with flue gases soda recovery boiler. The condensate formed during the cooling of the vapor-air mixture in the

heat exchanger, which allows simultaneously with the capture of dust particles to absorb the hydrogen sulfide, since the water is a soda solution having a pH of 13-13.5. At the same time, the jet washer jetter transports the steam-air mixture.

The drawing shows the technological scheme of the proposed method of heat recovery of a steam-air mixture.

The steam-air mixture from the tank 1 of the melt solvent passes through the duct 2 to the heat exchanger 3. Coolant is supplied to it via pipe 4 and discharged through pipe 5 for process needs. Water vapor condenses in the heat exchanger.

The non-condensed part of the air-steam mixture is sucked off by the mixing tube 6 of the jet gas scrubber. In the mixing tube 6, the dust particles are enlarged due to their deposition on the drops of the spray liquid and the gas-liquid mixture is transported to the droplet separator 7. In the drop catcher 7, the liquid drops are separated from the gas phase, which is directed through the gas duct 8 to the melt solvent tank 1 or through Exhaust 9 to the atmosphere directly or in mixture with CPKA flue gases.

A valve 10 is provided to adjust the emission of the gas mixture to the atmosphere.

The water vapor condensed in the heat exchanger 3 and the irrigating liquid separated in the drip catcher 7 are drained into an intermediate collection tank 11, from which pump 12 feeds the pipe 13 to the irrigation of the jet washer’s blender 6. The excess liquid collected in the tank collector through the pipe 14 is discharged into the tank 1 of the melt solvent.

Example. The heat of the vapor-air mixture of the CPKA melt solvent was regenerated according to the proposed method. The amount of this mixture is 20,000 under operating conditions, the humidity is 70%, the dust content is 10 g / nm of dry gas, the concentration of hydrogen sulfide is 0.3 g / nm of dry gas.

A steam-air mixture from the SRKA solvent tank with a capacity of 626 tons a. with. C / day (a. c. c. - absolutely dry substance) was fed to a horizontal heat exchanger. The gases flowed into the annular space, and the water for cooling - through the tubes. After the heat exchanger, the cooled mixture entered the jet washer, irrigated with water vapor condensate. The specific consumption of irrigating fluid, which was pumped under a pressure of 800 kPa to the spray device, is equal to 1.8 l / m of working gas.

Thus, the proposed method of heat-recovery of the steam-air mixture makes it possible to prevent the accumulation of dust particles in the steam-air mixture, since the total efficiency of their trapping in the heat exchanger and the jet scrubber is higher than 98%, therefore, the contamination of the heating surfaces of the heat exchanger during the circulation period

this mixture does not occur and the heat exchange process is stable.

In addition, the replacement of the fan with a jet-jet-gas-jet mixer, which, with a high specific flow rate of the irrigating fluid, has the ability to eject the vapor-air mixture in large quantities and with a large pressure, prevents possible disturbances in the mode of transportation of this mixture,

what happens when sticking dust particles on the rotor of this fan.

Periodic release of circulating

air-vapor mixture to atmosphere just

as well as continuous, it does not lead to the pollution of the air with harmful substances contained in this mixture after washing it in a jet gas scrubber, whose concentration in the surface layer of the atmosphere would not exceed the maximum permissible by sanitary norms.

According to the proposed method, the efficiency of utilization of the vapor-air mixture is increased due to the return to the production cycle of harmful substances (dust

particles, hydrogen sulphide and water vapor) required for the production of the main product.

Claims (2)

1.Pasechnik S.P. and Peat A.I. Gas purification installations of a melt solvent, Review of WITAIlesprom, 1977. 2. Patent of the USSR No. 283096, cl. D 210 11/06, 1967.