KR100205090B1 - Treatment method of zinc-contained dust and its apparatus - Google Patents

Abstract

The present invention provides a method for recovering an effective resource, in particular zinc powder, from a zinc-containing composition such as an electric furnace dust by using a vertical melt reduction furnace having two upper and lower tuyeres having a filling layer of a carbon-based reducing agent, and The apparatus relates to a device, wherein in the treatment of a zinc-containing composition by using a vertical melt reduction furnace having two up and down tuyeres with a packed bed of a carbon-based solid reducing agent, zinc is contained from at least the upper tuyeres of the vertical melt reduction. Furnace gas consisting of the gas produced by the combustion of the dust containing zinc as a main component and the carbon-based solid reducing agent at the exit side of the vertical melting reduction furnace after the composition is blown, and the zinc content contained in the zinc-containing composition is evaporated. And zinc is recovered by directly applying a refrigerant such as water to slurry dust. Treatment method and apparatus.

Description

Process for treating zinc-containing composition and apparatus therefor

The present invention is to efficiently recover effective resources, particularly zinc powder, from zinc-containing compositions, such as electric furnace dust, by using vertical melt reduction furnaces having two upper and lower tuyeres with a packed bed of a carbon-based solid reducing agent. A method and apparatus are disclosed.

In recent years, iron scrap has been recycled from the viewpoint of resource recycling, energy saving, and the like, but iron scrap has a large difference in quality due to its source.

For example, self-generated scrap is an iron scrap generated in the steel manufacturing process, and since its firing is clear and impurities are mixed little, most of it is consumed in the generating plant.

On the other hand, secondary scrap and waste scrap are fractionally recovered during the secondary processing of steel products or until the final product, and contain a lot of scraps of surface-treated steel sheets or special steel. Most of these scraps are melted and refined in an electric furnace manufacturer and reused. In the electric furnace dust, which is a zinc-containing composition generated at this time, chromium, cadmium, lead, etc., which may elute when landfilling is disposed of, may cause environmental pollution. In addition, 10 to 40% of zinc and 25 to 50% of iron are contained. It is. Other zinc-containing compositions include leach residues generated during wet zinc smelting, zinc-containing sludge or shredder dust generated during wastewater treatment of zinc plating. From these zinc-containing compositions, there is a strong demand for the establishment of techniques for recovering and reusing valuable metals such as zinc and iron by immobilizing harmful metals such as chromium, cadmium and lead at low cost.

As a conventional technique for recovering and recycling valuable metals from a zinc-containing composition, a method of using a vertical melt reduction furnace having two up and down tuyeres in Japanese Patent Laid-Open No. Hei 7-173548 is disclosed.

This method will be described based on the apparatus shown in FIG. Reference numeral 1 denotes a vertical melt reduction furnace (hereinafter referred to as a melt reduction furnace). Details thereof will be described with reference to FIG. The furnace-generated gas which consists of the dust which has carbon and the residue which generate | occur | produced in the melting reduction furnace 1, and the exhaust gas containing Zn vapor produced | generated by the combustion of a carbon-based solid reduction agent exhausts from the upper part of the melting reduction reactor 1 It is sent to the cyclone 52 through the gas duct 51, in which a part of carbon and zinc are separated from in-house generated gas. The separated carbon and zinc are discharged out of the system through the hopper 53 through a part of the carbon into the melt reduction path 1 and the remainder through the valve 54, the dust discharge hopper 55, the valve 56. Dust not collected in the cyclone 52 is sent to the cooling tank 58 through the exhaust gas duct 57 together with the exhaust gas to be cooled to remove dust. The remaining exhaust gas and fine dust are sent to the bag filter 59, and most of the dust is recovered there. Dust mainly composed of zinc recovered from the cooling tank 58 and the bag filter 59 is supplied to the transportation device 62 by the valves 60 and 61 and taken out of the system. The exhaust gas from which zinc has been removed is discharged out of the system.

In the case of treating the zinc-containing composition by the above method, when zinc-containing compositions such as electric dust are blown from the upper tuyeres of the melt reduction reactor 1, ZnO contained therein is reduced to Zn vapor, and Zn is It becomes Zn steam as it is. This Zn vapor is withdrawn from the top of the furnace via a carbon-based solid reducing agent. By the way, the dust collector of the cyclone or the like, the cooling tank (indirect cooling cooling tank configured to prevent the coolant from directly contacting the coolant and the dust), and the bag filter are arranged as the rear stage equipment of the melt reduction reactor. The same problem occurs.

1) If the dust that protrudes from the melt reduction path together with the exhaust gas containing Zn vapor is passed through an indirect cooling tank, zinc-containing dust is attached to the surface of the cooling water pipe or the inner wall of the cooling tank, and it is difficult to remove and remove it. In addition, when deposits grow and become mass with passage of time, the zinc-containing dust is not smoothly discharged.

2) In the indirect cooling system, when a large amount of zinc-containing dust adheres to the cooling water pipes arranged inside the cooling tank or the inner wall of the cooling tank, the flow area of the exhaust gas is reduced and the pressure loss in the system becomes large, resulting in unstable operation. .

3) In the case of indirect cooling type cooling tank, when dust is attached to the cooling water pipe in large quantities, the cooling efficiency of dust and exhaust gas is greatly reduced. Therefore, trouble such as damage to bag filter or discharge device due to the temperature of exhaust gas rises. This may occur.

1 is a diagram showing the configuration of an optimal first facility used to practice the present invention.

2 is a diagram showing the configuration of an optimal second equipment used for practicing the present invention.

3 is a view showing the configuration of the exhaust gas temperature and the exhaust gas treatment equipment.

4 is a diagram showing the configuration of a third apparatus that is optimal for use in practicing the present invention.

5 is a view showing a configuration of a conventional zinc composition treatment.

* Explanation of symbols for main parts of the drawings

1: vertical melt reduction furnace 2: top vent

3: bottom vent 5: filling layer

6: powder blowing device 7: pipeline

8: Lance 10: Exit

11, 35: duct 12: cooling device

36, 37: combustion burner

The present invention provides a novel method capable of treating zinc-containing compositions such as dust and the like without causing the problems described above.

The present invention relates to a smelting solvent from at least an upper tuyeres of a vertical melt reduction furnace in treating a zinc-containing composition by using a vertical melt reduction furnace having two up and down tuyeres with a packed bed of a carbon-based solid reducing agent. And the zinc-containing composition was blown together, and the slurry generated by directly acting a liquid refrigerant with a furnace refrigerant gas composed mainly of exhaust gas containing Zn vapor generated by combustion heat of the carbon-based solid reducing agent and dust and residues composed of residues. The dust is a method for treating a zinc-containing composition, which is characterized by recovering zinc.

Further, in the above method, carbon from the in-house generated gas consisting of exhaust gas containing Zn vapor generated by combustion heat and reducing gas of a carbon-based solid supernatant, dust containing carbon and residues generated in the furnace as a main component. A method of treating a zinc-containing composition, which recovers zinc by recovering a portion of zinc and subsequently making the slurry gas by directly acting the furnace gas and the liquid refrigerant at a later stage.

In addition, the present invention provides a device for treating a zinc-containing composition by using a vertical melt reduction furnace having two upper and lower tuyeres with a filling layer of a carbon-based solid reducing agent, wherein the carbon generated in the vertical melt reduction reactor and The furnace gas consisting of dust containing mainly residues and exhaust gas containing Zn vapor generated by the combustion heat of the carbon-based solid reducing agent and the reducing gas is directly cooled with a liquid refrigerant, and further suspended with a liquid refrigerant to further slurry liquid. A cooling device having a cooling means for making the slurry liquid, and a cooling tank for temporarily storing the slurry liquid, a precipitation tank for precipitating the slurry liquid, a dehydration tank for dehydrating the slurry liquid, and a transportation means for discharging the concentrated slurry liquid. It is a processing apparatus of the zinc containing composition which consists of.

Other configurations of the present invention will become apparent from the following detailed description together with the variations thereof.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail using drawing.

1 shows a configuration of a first apparatus suitable for treating a zinc-containing composition.

In the vertical melt reduction furnace 1 (hereinafter referred to as melt reduction furnace), a filling layer 5 is formed in which carbonaceous material is supplied from the carbonaceous material hopper 4 to maintain a predetermined stock line at the top of the furnace.

The zinc-containing composition is a smelting reduction furnace (1) through a pipeline (7) from a powder blowing device (6) to a smelting solvent composed of coal stone and silica, which is added for the purpose of adjusting the viscosity and melting point of slag. Is blown into the furnace through the top tuyeres (2).

And when a zinc containing composition is not powder, it is necessary to make a zinc containing composition into powder previously.

Blowing air is heated at about 800-1000 degreeC, and it blows in into a furnace from the upper tuyeres 2 and the lower tuyeres 4 as hot air through a blower tube, respectively. At this time, if necessary, suitable oxygen is supplied to the hot air to combust the carbonaceous material in the melting / reduction reactor 1, but the zinc-containing composition blown from the upper tuyeres 2 by the heat of combustion and reducing gas at that time melts.

Then, zinc in the zinc-containing composition is reduced to Zn vapor, and Zn is converted to Zn vapor as it is, and passes through the packed bed 5 of the carbonaceous material and is discharged from the exhaust gas duct 11 above the melting furnace reduction furnace 1. do. A secondary combustion lance 8 is arranged at the top of the melt reduction reactor 1, and the exhaust gas is combusted in order to maintain the temperature of the upper portion of the packed bed 5 at 600 to 1000 ° C, which is a temperature at which Zn vapor is stabilized.

Further, the iron oxide in the zinc-containing composition melts in the blower raceway of the upper tuyeres 2 by the heat of combustion of the carbonaceous material together with chromium and the like, and the molten carbon is lowered toward the lower tuyeres 3. While the process is reduced by the reverse flow contact with the reducing gas generated in the blower of the lower tuyeres 3, and in contact with the carbonaceous material of the total electrode layer 5 is directly reduced to separate the metal and slag.

Finally, the molten metal accumulated at the bottom of the furnace is discharged through the tap opening 9, and the slug is discharged through the tap opening 10, respectively, in which chromium and the like are fixed in the molten metal and in the lag to be harmless.

On the other hand, in-house generation consists of dust mainly composed of carbon discharged from the exhaust gas duct 11 above the melt reduction reactor 1 and exhaust gas containing Zn vapor generated by the heat of combustion of the carbon-based solid reducing agent. The gas is sent to the chiller 12. The cooling device 12 includes a cooling tank 14 having two cooling cylinders 13a and 13b, a liquid refrigerant such as water, and the like by spraying 16 and the like into the cooling cylinders 13a and 3b and the cooling tank 14. (Hereinafter, cooling water is shown as a representative example). The one cooling cylinder 13a is connected to the exhaust gas dust 11, and the other cooling cylinder 13b is connected to the exhaust gas discharge dust 17.

Furnace gas discharged from the exhaust gas duct 11 is introduced into the cooling tank 14, is directly cooled by the cooling means 15, is also damped and suspended with cooling water at the bottom of the cooling tank 14 to slurry liquid. (18).

The dust-collected and cooled exhaust gas is discharged out of the system by the exhaust gas duct 17 at a temperature of 200 ° C. or lower, but the slurry liquid 18 accumulated at the bottom of the cooling tank 14 is the level meter 19 and the flow control valve. The liquid level is adjusted by 20, and transported to the settling tank 26 by the slurry pump 21. Subsequently, it is transported from the bottom of the settling tank 26 to the dehydrator 23 by the slurry pump 22, and dewatered in the range of 40-80 degreeC of concentration, More preferably, 50-70 degreeC, and then through the slurry transport apparatus 24. The concentrated slurry of zinc is discharged into the container 25.

The waste liquid of the dehydrator 23 sends the settling tank 26 to settle the solids such as dust contained in the waste liquid, and the cooling means 15 is transferred to the treated water pump 28 with the treated water 27 from which most of the solids are removed. It circulates through the cooling tank 14 through.

In this invention, although the density | concentration of the slurry dust collect | recovered with the dehydrator 23 was made into 40%-80%, the reason is as follows.

That is, when the slurry concentration is less than 40%, since the amount of water contained in the slurry liquid is remarkably increased, there is a disadvantage that the volume of the precipitation tank 26 increases more than necessary. On the other hand, when the concentration of slurry dust exceeds 80%, the load on the slurry transport apparatus 24 becomes large, and there exists inappropriateness, such as a blockage of a transport pipe.

Next, a second apparatus suitable for treating the zinc-containing composition will be described with reference to FIG.

A cyclone 29 is provided between the melt reduction reactor 1 and the cooling device 12, and furnace gas generated from the exhaust gas dust 11 in the upper portion of the melt reduction reactor 1 is heated by the cyclone 29. . Here, a part of dust and zinc containing relatively rough carbon powder generated from the carbonaceous material in the furnace is charged, and most of the carbon powder contained in the dust is separated.

Part of the dust (collected dust) mainly composed of carbon separated by the cyclone 29 passes through the hopper 30 to the furnace through the upper tuyeres 2 from the dust transport device 31, and the remaining dust is The valve 32 is discharged to the outside through the dust discharge hopper 33 and the valve.

Dust not collected in the cyclone 29 is introduced into the cooling device 12 together with the exhaust gas and cooled by the cooling means 15 to be suspended with cooling water at the bottom of the cooling tank 14 to the slurry liquid 18. do. By this method, a higher concentration of zinc can be recovered. The slurry liquid 18 is processed through the same process as the first facility described in FIG.

In the present invention, since the zinc contained in the exhaust gas is recovered as slurry dust in the cooling device 12, adhesion in the cooling tank 14 and accompanying massification are suppressed. Damage troubles can also be avoided.

In the present invention, the exhaust gas is secondary burned in the step before cooling the water spray, but the reason will be described below.

In the treatment of the zinc-containing composition using the carbonaceous filling layer type melt reduction reactor, a large amount of Zn vapor is contained in the exhaust gas, and a large amount of dust mainly containing Zn or ZnO adheres inside the duct through which the exhaust gas passes. It is feared that operation troubles such as aeration will be frequent and the operation in the melt reduction reactor will become unstable.

In order to investigate the cause, various experiments were conducted, and the following became clear.

1) A large amount of deposit mainly composed of a mixture of ZnO and C is observed on the inner wall of exhaust gas dust when ventilation is prevented.

2) Aeration must occur at low exhaust gas temperatures.

3) When the exhaust gas temperature is low, the ZnO side is more stable than Zn even in the carbonaceous filler layer, which is estimated to have high reducibility.

4) Exhaust gas temperature and oxidation degree of exhaust gas (CO ₂ + H ₂ O) + (CO + CO ₂ + H ₂ + H ₂ O), the presence of zinc in the exhaust gas (Zn is ZnO) The situation is as shown in FIG.

5) The Zn vapor pressure of the top flue gas varies depending on the zinc content of the zinc-containing composition. However, in the operating range feasible in the present invention, the optical analysis value of the aggregates collected by the measurement by the exhaust gas mass spectrometer or the rapid aggregation of the collected gas and It is about 0.01 to 0.1 atm from the estimated value calculated from the collected gas.

In view of the above, in the operation of the melt reduction furnace (having two stage vents), in order to stably operate the melt reduction reactor without causing operation troubles due to ZnO dust adhesion in the exhaust gas duct of the furnace, The presence of zinc in the exhaust gas of Zn is required to be Zn vapor.

Here, in the operation using the equipment which consists of the 1st structure shown in FIG. 1, or the apparatus which consists of the 2nd structure shown in FIG. 2, even if it is made to maintain the exhaust gas temperature of a top on the conditions which Zn vapor recognized, Only the combustion lance 8 is concerned about falling short of it at the beginning of operation. Therefore, as shown in FIG. 4, for example, duct secondary combustion burners 36 and 37 are disposed on at least one of the exhaust dusts 11 and 35 of the second facility to burn the exhaust gas.

Attachment of dust in the exhaust gas ducts 11 and 35 detects the magnitude of the pressure loss of the duct, detects the change in the temperature of the thermometer installed in the duct, or measures the temperature of the outer surface of the duct, Can be detected. If it is necessary to specify the position where the dust is attached, install a plurality of pressure gauges or differential pressure gauges P ₁ to P _{3 in} the longitudinal direction of the duct to measure the partial pressure in the duct or the thermometers T ₁ to T. ₄ ) It is good to measure the external surface temperature of duct by installing a plurality of ducts, so that it is possible to grasp the formation status and location of the attachment to the duct.

In the secondary combustion of exhaust gas from the exhaust gas ducts 11 and 35, the amount of oxygen or air blown into the ducts 11 and 35 is adjusted to maintain the temperature of the exhaust gas and the oxidation degree of the exhaust gas appropriately. The deposition of ZnO in the gas is avoided, but the exhaust gas temperature that must be achieved by secondary combustion is a condition as shown in FIG. 3, which is determined by the exhaust gas temperature before secondary combustion and the partial pressure of Zn vapor in the exhaust gas. Follow.

In FIG. 4, the case where one secondary combustion burner is provided in each of the duct 11 and the duct 35 is shown. However, the number of installations of the secondary combustion burners can be increased or decreased according to the operation status (zinc adhesion condition). In particular, the number of installation is not limited.

In the case where the exhaust gas temperature in the exhaust gas ducts 11 and 35 before the secondary combustion is 700 ° C., for example, and the partial pressure of Zn vapor in the exhaust gas at that time is 0.1 atm, as apparent from FIG. 3, In consideration of the effect of increasing the oxidation degree by the secondary combustion and the effect of increasing the exhaust gas temperature, the exhaust gas temperature after the secondary combustion is 1000 ° C or more.

In the exhaust gas ducts 1 and 3 on the exit side of the melt reduction path 1, dust adhesion conditions and parts are detected, and based on the detection information, Zn steam is stabilized while adjusting the combustion conditions by the secondary combustion burner. When the exhaust gas temperature or the oxidation degree are adjusted, adhesion of dust mainly composed of Zn or ZnO in the exhaust gas duct is suppressed, and operation troubles and loss of refractory in the furnace can be avoided, and zinc in the dust can be avoided. Since it can be recovered at a stable and high concentration, it is also very advantageous for recycling.

In the present invention, since the zinc contained in the exhaust gas in the cooling tank 14 is recovered as a slurry, adhesion of the inside of the cooling tank 14 and concomitant agglomeration thereof can be suppressed. Damage trouble can also be avoided. In addition, since secondary combustion of the exhaust gas in the exhaust gas duct prevents adhesion of Zn and dust mainly composed of ZnO in the exhaust gas duct, it is possible to avoid operation trouble or damage to the furnace refractory. Since zinc in dust can be recovered at a stable and high concentration, it is also very advantageous for recycling.

Example 1

Using the equipment shown in FIG. 1 with a furnace having a furnace length of 1.2 m, a height of 8.0 m, and three tuyeres up and down, the air flow rate is 1650 Nm ³ / hr, the blowing temperature is 900 ° C., the amount of hatched oxygen is 50 to 200 Nm ³ / hr, suction amount of dust: 600 ~ 900kg / hr (mixing ratio: 85% of electric charge dust, 15% of solvent (limestone + silica)), electric dust (T.Fe: 28.4%, Ze: 29.9%, Cr) : 0.27%, Pb: 2.05%, Cd: 0.04%, SiO ₂ : 2.91%, Al ₂ O ₃ : 1.55, CaO: 1.23%, MgO: 0.38%, MnO: 2.36%, Na ₂ O: 1.53%, K ₂ O: 0.81%) was carried out to investigate the operation situation at that time. The results are shown in Table 1 together with the test conditions.

As apparent from Table 1, when the dust was treated with electricity according to the present invention, no trouble occurred after the cooling device, and high concentrations of zinc dust could be recovered.

In this test operation, the metal composition obtained from the melt reduction furnace is 90-93% Fe, 1-2% Si, 4.0-4.2% C, 0.8-1.2% Mn, 0.6-0.9% Cr. and containing pig iron, it was the composition containing MnO in for the slag 24-27% of SiO _2, 16 ~ 24% of _{Al 2 O 3, 22 ~ 25} % of CaO, of 2.3 ~ 2.6 MgO, 5.7 ~ 6.8 .

Example 2

Electric furnace dust was treated under the following conditions using the melt reduction furnace shown in FIG. 4 having a furnace length of 1.2 m, a height of 8.0 m, and three tuyeres at the upper and lower ends, and investigated the operation situation at that time. The investigation results are shown in Table 1 together with the test conditions.

Condition

1) Blowing condition

Blowing air volume: 165Nm ³ / hr

Blowing temperature: 900 ℃

Hatching Oxygen: 50 ~ 200Nm ³ / hr

2) Powder blowing condition

Compounding ratio: 85% electric dust (composition is the same as in Example 1)

Solvent (Limestone + Quartz) 15%

Suction volume: 600 ~ 900kg / hr

As apparent from Table 1, when the dust is treated with electricity according to the present invention, no trouble occurs in the exhaust gas dust, and high concentration of zinc dust can be recovered.

The metal composition obtained in this example is pig iron containing 90 to 93% of Fe, 1 to 2% of Fi, 4.0 to 4.2% of C, 0.8 to 1.2% of Mn, and 0.6 to 0.9% of Cr. For the slag, it was a composition containing 24 to 27% SiO ₂ , 16 to 24% Al ₂ O ₃ , 22 to 25% CaO, 2.3 to 2.6 MgO, and 5.7 to 6.8 Mn.

As described above, according to the present invention, since the zinc-containing composition of the dust can be treated as it is, and the separation recovery of dust and molten iron can be treated with a single vertical melt reduction furnace, the treatment cost can be minimized. can do. In addition, since zinc can be recovered from the zinc-containing composition with high efficiency, the effect of resources can be achieved.

Claims (11)

In treating a zinc-containing composition by using a vertical melt reduction furnace having two up and down tuyeres with a packed bed of a carbon-based solid reducing agent, zinc is contained together with a smelting solvent from at least the upper tuyeres of the vertical melt reduction. The composition is blown, and the furnace gas consisting of the exhaust gas containing the heat of combustion of the carbon-based solid reducing agent and Zn vapor generated by the reducing gas and the dust mainly composed of carbon and residues generated in the furnace are directly reacted with the liquid refrigerant. A method for treating a zinc-containing composition, wherein zinc is recovered by slurry dust. In treating a zinc-containing composition by using a vertical melt reduction furnace having two up and down tuyeres with a packed bed of a carbon-based solid reducing agent, zinc is contained together with a smelting solvent from at least the upper tuyeres of the vertical melt reduction. Part of the carbon and zinc from the furnace gas consisting of the exhaust gas containing Zn vapor generated by the combustion heat and reducing gas of the carbon-based solid reducing agent and the dust mainly composed of carbon and residues generated in the furnace. Recovering zinc, and then recovering zinc by directly acting the furnace gas and the liquid refrigerant at a later stage to make slurry dust, thereby recovering the zinc-containing composition. The method of treating a zinc-containing composition according to claim 1, wherein the zinc-containing composition is pretreated in powder form when the zinc-containing composition is treated with a vertical melt reduction furnace. The method for treating a zinc-containing composition according to claim 1, wherein the slurry concentration after dehydration is 40 to 80%. The process for treating a zinc-containing composition according to claim 1, wherein the gas generated in the furnace is subjected to secondary combustion at a stage before directly applying a refrigerant such as water to the gas generated in the furnace. An apparatus for treating a zinc-containing composition by using a vertical melt reduction furnace having two upper and lower stage tuyeres with a filling layer of a carbon-based solid reducing agent, comprising: carbon and residue generated from the vertical melt reduction furnace as main components. This slurry contains cooling means for directly cooling a gas generated in the furnace and a gas produced by the combustion heat of the dust and the carbon-based solid reducing agent with a liquid refrigerant, and further suspending it with the liquid refrigerant to form a slurry liquid. A processing apparatus for a zinc-containing composition comprising a cooling device having a cooling tank for temporarily stopping a liquid, a precipitation tank for precipitating slurry liquid, a dehydration tank for dewatering the slurry liquid, and a transport means for discharging the concentrated slurry liquid. 7. The apparatus for treating zinc-containing compositions according to claim 6, further comprising a cyclone between the vertical melt reduction reactor and the cooling device. 8. The secondary combustion burner according to claim 6 or 7, wherein a secondary combustion burner for ducts is disposed in an exhaust gas transport duct connecting the vertical melt reduction path and the cooling device or the vertical melt reduction path, the cyclone and the cooling device. A treatment apparatus for a zinc-containing composition, characterized in that one. The method of treating a zinc-containing composition according to claim 2, wherein the zinc-containing composition is pretreated in powder form when the zinc-containing composition is treated with a vertical melt reduction furnace. The method for treating a zinc-containing composition according to claim 2, wherein the slurry concentration after dehydration is 40 to 80%. The method of treating a zinc-containing composition according to claim 2, wherein in-furnace generated gas is subjected to secondary combustion in a step before directly applying a refrigerant such as water to the in-house generated gas.