GB1561762A - Humidification of gases - Google Patents

Description

(54) HUMIDIFICATION OF GASES (71) We, BRITISH STEEL CORPORATION, a Corporation incorporated and existing under the Iron and Steel Act 1967 whose principal office is at 33 Grosvenor Place, London, S.W.1 do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the humidification of a gas which is to be introduced into a heat exchanger particularly a blast furnace stove.

In conventional ironmaking humidified air, i.e. air containing water vapour, is injected into a blast furnace via the tuyeres at high pressure. The moisture in the gas assists in promoting the efficiency of the various reduction processes which take place in the blast furnace during ironmaking. Conventionally the air is humidified by injecting steam into the air stream after it has been compressed and before it reaches the blast furnace stove which by heat transfer heats up the humidified air. The hot moist air is then injected into the blast furnace.

According to the present invention a method for humidifying a gas which is to be introduced in a heat exchanger comprises introducing into the chamber of a compressor a stream of gas and a stream of water in the form of atomised particles, the flow rate, temperature and pressure of the gas and the water particles within the compressor being such that the gas leaving the compressor contains water vapour.

Preferably the heat exchanger is a blast furnace stove.

Suitably the water particles have a size no greater than 50 microns.

Tn one embodiment of the invention the gas contains oxygen and may if desired be air.

If the technique of the present invention is adopted in ironmaking instead of the prior practice previously described, two important advantages are obtained. Firstly, while the air/vapour mixture entering the blast furnace stove is at a lower temperature than is the case with the prior practice, more heat is extracted from the hot blast furnace stove to heat the vapour so that due to increased heat transfer the stove works more efficiently. This results in an energy saving equivalent to the latent heat required to evaporate the water added, which would, in conventional practice, be supplied in the steam from the boiler plant. Secondly, it has been found that the shaft work or energy required to compress the air in the present invention is lower than in the prior art practice.This is due to the cooling effect exerted on the air as a result of the evaporation of the water particles introduced in to the intake gas steam.

An embodiment of the present invention will now be particularly described by way of example only with reference to the accompanying flow sheet.

Air at ambient pressure of 1.02 bar absolute was supplied to the chamber of a conventional centrifugally operated compressor. The volume flow rate of the air was 45.0 cubic metres per second, the ambient air temperature was 16"C and relative humidity was 49%. Very pure distilled water at a temperature of 16"C was supplied to a suitable atomising nozzle located in the compressor inlet. The nozzle atomised the water to form droplets of average size 45 microns and these entered the compressor chamber at a flow rate of Sg/m3 of air. The exit gas was found to contin water vapour and left the compressor at a pressure of 2.5 bar absolute.

This gas was then led to a hot blast stove and thence to a blast furnace in line with conventional practice. The compressor isentropic efficiency was 65% and the energy required to compress the air was found to be 7.381 MW. This compared with the normal energy required to compress the air alone of 7.554 giving an energy saving of 0.173MW. In addition it was found that the fuel flow saving in latent heat of steam was 0.665 MW.

It will be appreciated that for blast furnaces of conventional size these energy savings are very worthwhile but for the newer larger furnaces (10,000 tonnes/day capacity) the savings are considerable.

It will also be appreciated that while the invention has been described with reference to iron-making, it could equally well be applied with advantage to any operation in which the compression of gas forms an important part of the procedure. For in- stance the energy saving in the compression of gas necessary to drive a gas turbine would also be considerable were the present technique to be applied thereto.

WHAT WE CLAIM IS: 1. A method for humidifying a gas which is to be introduced into a heat exchanger, the method comprising introducing into the chamber of a compressor a stream of gas and a stream of water in the form of atomised particles, the flow rate, temperature and pressure of the gas and the water particles within the compressor being such that the gas leaving the compressor contains water vapour.

2. A method as claimed in claim 1 in in which the heat exchanger is a blast furnace stove.

3. A method as claimed in claim I or claim 2 in which the water particles have a size no greater than 50 microns.

4. A method as claimed in any preceding claim in which the gas contains oxygen.

5. A method as claimed in any preceding claim in which the gas is air.

6. A method substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. and thence to a blast furnace in line with conventional practice. The compressor isentropic efficiency was 65% and the energy required to compress the air was found to be 7.381 MW. This compared with the normal energy required to compress the air alone of 7.554 giving an energy saving of 0.173MW. In addition it was found that the fuel flow saving in latent heat of steam was 0.665 MW. It will be appreciated that for blast furnaces of conventional size these energy savings are very worthwhile but for the newer larger furnaces (10,000 tonnes/day capacity) the savings are considerable. It will also be appreciated that while the invention has been described with reference to iron-making, it could equally well be applied with advantage to any operation in which the compression of gas forms an important part of the procedure. For in- stance the energy saving in the compression of gas necessary to drive a gas turbine would also be considerable were the present technique to be applied thereto. WHAT WE CLAIM IS:

1. A method for humidifying a gas which is to be introduced into a heat exchanger, the method comprising introducing into the chamber of a compressor a stream of gas and a stream of water in the form of atomised particles, the flow rate, temperature and pressure of the gas and the water particles within the compressor being such that the gas leaving the compressor contains water vapour.

2. A method as claimed in claim 1 in in which the heat exchanger is a blast furnace stove.

3. A method as claimed in claim I or claim 2 in which the water particles have a size no greater than 50 microns.

4. A method as claimed in any preceding claim in which the gas contains oxygen.

5. A method as claimed in any preceding claim in which the gas is air.

6. A method substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.