Patent Application
20240308889
Hydrogen sulfide is a chemical compound with the formula H2S. At room temperature, it is a colorless, flammable and extremely dangerous gas with the characteristic foul odor of rotten eggs. Chemically, hydrogen sulfide acts as a reducing agent, and reacts with metal ions to form metal sulfides, which may be considered the salts of hydrogen sulfide. In addition, the naturally occurring mineral form of several metals are sulfides (e.g., galena, or lead (II) sulfide and sphalerite, or zinc sulfide).
In regards to health, hydrogen sulfide is both an irritant and a chemical asphyxiant which affects oxygen utilization and the central nervous system. At lower concentrations (2-5 ppm), this can cause nausea, tearing of the eyes, headaches and/or loss of sleep. Higher concentrations (5-100 ppm) can cause more severe eye and respiratory irritation. At higher concentrations, (100+ ppm) it can cause shock, convulsions, inability to breathe, extremely rapid unconsciousness, coma and death.
As far as the mining industry, hydrogen sulfide is used in the preparation of metal sulfides and removal of impurities in metallurgical processes. This process is described, for example, in the article entitled “Biological Sulfide Production for Metal Recovery,” by C. J. N. Buisman et al. at the TMS Congress of 1999. Often in industries (e.g., mining industries, sulfuric acid factories) diluted streams of sulfuric acid, contaminated with metals have to be treated. These streams in the past have been neutralized using limestone or other alkalinic components, resulting in the precipitation of sulfates and metals such as gypsum and metal hydroxides, respectively, which have to be landfilled. In addition, all valuable metals are lost in the sludge. With biogenic sulfide production, these contaminated streams can be treated to produce sulfur and metal sulfides. Metals present in the waste acid bleed used as a source for hydrogen sulfide production will precipitate as metal sulfides based on:
Metal+H2S→metal-sulfide
However obtained, hydrogen sulfide can be very costly to produce because of the dangers involved in production, and because of the hazards it poses to human health. What is needed is a cost-effective method of producing industrial-scale quantities of hydrogen sulfide that eliminates the need for expensive reagents such as pure hydrogen, ethanol or natural gas.
Additionally, it would be advantageous to produce hydrogen sulfide in a process that is thermodynamically favored such that the rate of production can be controlled by controlling the temperature of the reaction vessel.
There are major mining companies which have concentrator plants for which sodium hydrosulfide (NaHS) is widely used during separation of the copper/molybdenum. It is shown that at this stage you can use either sodium hydrosulfide (NaHS), sodium sulfide (Na2S) or directly hydrogen sulfide (H2S) when any of the substitutes reagents (NaHS or Na2S) is fed, the final product is H2S.
NaHS used by major mining companies at its mines in Mexico for example generally are imported from the USA by rail, which has the disadvantage of being very expensive, difficult to manage as well as remoteness. These mining companies could use H2S directly in their process and in this case there is great interest in on-site production technology.
In view of the foregoing disadvantages inherent in its production, embodiments described herein provide an innovative, efficient, and fast process to produce hydrogen sulfide on-site.
In some embodiments, processes are described that provide a safe, cost-efficient method for producing hydrogen sulfide used for the precipitation of metal that are in solution. The hydrogen sulfide can be produced on-site to eliminate the need for transporting thus reducing costs and removing an element of danger.
In some embodiments, the hydrogen sulfide is used for the extraction of metals in liquid streams, containing at least one metal, whereby the gaseous hydrogen sulfide is fed into a mixing apparatus containing the liquid stream and mixed under conditions sufficient to extract the at least one metal.
In one embodiment of the process, a stream of concentrated Na2SO4 is combined with a stream of natural gas into a converter at a temperature of about 1050° C. The preferred product is Na2S. In the same embodiment, the preferred product is directed into a prep tank, into which an appropriate amount of water is injected to prepare an appropriate stoichiometric solution. The solution is then pressurized using a high-pressure pump. This stream is then blended with another water stream, which is specifically incorporated to facilitate heat recovery of reaction products using an interchange device. The Na2S and water stream then flows through a heater and into the H2S reaction system. A sulfur stream is blended with a recycle sulfur stream. A composite of these two streams is then pumped into a sulfur tank. The sulfur will melt inside the H2S reactor. This elemental molten sulfur is pumped out and directed into the H2S reaction system.
In an alternate embodiment the preferred product is directed into an agitated Na2S solution and sulfur slurry prep tank. Finely ground, comminuted elemental sulfur is pneumatically transported into the prep tank. A recycle sulfur stream, is also continuously blended into the slurry pump tank. A stream of water emanating from interchanger is also continuously introduced into the prep tank. The product from the Na2S solution and sulfur slurry prep tank is pressurized using a high-pressure pump. High pressure slurry solution stream then flows through an interchange where it picks up any available heat from the stream that is flowing into the prep tank. The warmed slurry solution stream then flows through a heater, that brings the entire stream up to the necessary temperature for initiating and conducting the downstream reactions. The Na2S-sulfur/water stream is directed to flow into the first H2S reactor.
These and other aspects of the embodiments herein are further described in the following figures and detailed description. However, the claims are not intended to be limited by such figures and description.
In one embodiment, as represented in
The Na2S is directed into a prep tank, 9, into which an appropriate amount of water, 10, is injected to prepare an appropriate stoichiometric solution. This solution is then pressurized using a high-pressure pump, 11. This stream is then blended with another water stream, 29, which is specifically incorporated to facilitate heat recovery of reaction products using an interchanger device. This Na2S and water stream then flows through a heater, 12, and into the H2S reaction system.
A sulfur stream, 13, is blended with a recycle sulfur stream, 14. A composite of these two streams is then pumped into a sulfur tank, 15. The sulfur will melt inside the H2S reactor. There is no need to maintain a sulfur temperature of about 120° C. outside of the reactor. This elemental molten sulfur is pumped out using a jacketed high pressure positive displacement pump, 16, and directed into the H2S reaction system.
The Na2S-water stream and the molten elemental sulfur stream are directed to flow into the first H2S reactor, 17. This reactor is equipped with an agitation device, 18, that ensures the maintenance of finally dispersed sulfur in the Na2S-water medium. The H2S reactor operates at a temperature of 200-250° C. and a service pressure between 20-50 bar. The H2S, which is a product of the reaction, leaves the reactor through line 19. The H2S reactor, 17, is configured to work in a cascade mode where the overflow from this reactor is directed into the next reactor through line 20. This H2S reactor, 21, as noted is working in a cascade mode using the overflow from the first reactor, 17. This reactor is also equipped with an agitation-dispersion device, 22, which ensures homogeneity of the reaction. Hydrogen sulfide, the reaction product, leaves through line 23. The merged H2S lines from reactor 17 and 21 flows through a backpressure control valve, 24. The depressurized H2S stream, 25, is then piped for its appropriate use.
The hot liquids leaving the two H2S reactors are combined as stream, 26. This stream primarily comprises of Na2SO4, a small amount of unreacted Na2S, unreacted sulfur and unreacted water. It first flows through the tube side of a heat interchanger, 27. Water, stream 28, flows through the shell side of this interchanger to maximize the pick-up of heat. This hot water stream 29, is redirected back into the H2S reactor cascading system. The cooled reactor effluent stream, 30, then flows into a centrifuge that is specifically designed to separate the sulfur slurry component from the Na2SO4 liquor component. The sulfur slurry component, 32, is then sent into a dehydrator, 33, where the water is boiled out as stream 34 leaving behind sulfur in a molten condition. This sulfur is pumped back into the main sulfur tank, 15.
Leaving the centrifuge, 31, is the Na2SO4 liquor recycle stream, 2, that is directed to the Na2SO4 concentrator. This stream undergoes concentration and flows into the Na2SO4 to Na2S converter that closes the sodium salt recycle loop. In another embodiment, as represented in
The Na2S is directed into an agitated Na2S solution and sulfur slurry prep tank, 9. Finally ground, comminuted elemental sulfur, 10, is pneumatically transported into the prep tank, 9. A recycle sulfur stream, 12, is also continuously blended into the slurry pump tank, 9. A stream of water emanating from interchanger 15 is also continuously introduced into the prep tank. The product from the Na2S solution and sulfur slurry prep tank is pressurized using a high-pressure pump, 13. High pressure slurry solution stream, 14, then flows through an interchanger, 15, where it picks up any available heat from the stream, 11, that is flowing into the prep tank. The warmed slurry solution stream, 16, then flows through a heater, 17, that brings the entire stream up to the necessary temperature for initiating and conducting the downstream reactions.
The Na2S-sulfur/water stream is directed to flow into the first H2S reactor, 19. This reactor is equipped with an agitation device, 20, that ensures the maintenance of finally dispersed sulfur in the Na2S-water medium. The H2S reactor operates at a temperature of 200-250° C. and a service pressure between 20-50 bar. The H2S, which is a product of the reaction, leaves the reactor through line 21. The H2S reactor, 19, is configured to work in a cascade mode where the overflow from this reactor is directed into the next reactor through line 22. This H2S reactor, 23, as noted is working in a cascade mode using the overflow from the first reactor, 19. This reactor is also equipped with an agitation-dispersion device, 24, which ensures homogeneity of the reaction. Hydrogen sulfide, the reaction product, leaves through line 25. The merged H2S lines from reactors 19 and 23 consolidate as line, 26 and flow through a backpressure control valve, 27. The depressurized H2S stream, 28, is then piped for its appropriate use.
The hot liquids leaving the two H2S reactors are combined as stream, 29. This stream primarily comprises of Na2SO4, a small amount of unreacted Na2S, unreacted sulfur and unreacted water. It first flows through the tube side of a heat interchanger, 30. Water, stream 31, flows through the shell side of this interchanger to maximize the pick-up of heat. This hot water stream, 32, is directed to the interchanger, 16, and from there becomes line 11 that flows into the prep tank, 9. The cooled reactor effluent stream, 33, then flows into a centrifuge, 34, that is specifically designed to separate the sulfur slurry component from the Na2SO4 liquor component. The sulfur slurry component, 35, is then recycled using pump, 36, and becomes stream 12 that flows into prep tank, 9.
Leaving the centrifuge, 34, is the Na2SO4 liquor recycle stream, 2, that is directed to the Na2SO4 concentrator. This stream undergoes concentration and flows into the Na2SO4 to Na2S converter that closes the sodium salt recycle loop.
In one embodiment the hydrogen sulfide is generated electrochemically. Generating H2S in an electrochemical reactor whereby one can:
Hydrogen can be from tank hydrogen or can be made on demand by the electrolysis of water by controlling current. With adequate H2 then H2S should also be supplied on demand by controlling the current.
In another embodiment the hydrogen sulfide can be produced using bio-reactors and feed into a mixing system or apparatus.
In another embodiment, use of proprietary bubble column reactors (BCR) can be done. In an example of its operation, an acid mine effluent has been tested at a site, with an average flow rate of 100 m3/day, and a concentration of 720 ppm of Fe, 21 ppm of Cu and 258 ppm of Zn at pH 2.5. The purpose of this setup was to try to reduce the concentration of metals and neutralization of the effluent. This is accomplished by producing H2S through a plant.
In one embodiment, hydrogen sulfide and dosing in BCR columns with the following operating conditions of the plant is performed:
This application claims priority to Provisional Application No. 63/081,585 filed on Sep. 22, 2020, to Provisional Application No. 63/014,947 filed on Apr. 24, 2020, and is a continuation of application Ser. No. 17/302,101, the content of all of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 17302101 | Apr 2021 | US |
| Child | 18669064 | US |
