Abstract: A method for extracting and separating Gold, Silver, Copper, Zinc and/or Lead from an Arsenic-containing ore, concentrate or tailings characterized in that the extraction is carried by roasting in the presence of a calcium-containing material and at least one of an alkali metal halide and alkaline metal halide. In the method, Arsenic remains immobilized in the extraction residue.

Abstract: This invention relates to a hydrometallurgical process for the recovery and separation of valuable precious, base or rare elements such as platinum group metals (PGMs), gold or silver, and other valuable base and rare metals such as nickel, cobalt, copper, rare earth elements (REE), yttrium and scandium, as well as uranium, thorium, manganese, zinc, cadmium, molybdenum, titanium, tin, and other minor elements such as vanadium, germanium and gallium from a feed material comprising ores, concentrates and other materials. In particular, the process comprises quantitative removal of additional base, rare and gangue elements for increased efficiency of further treatment of the solids for valuable metals recovery and/or recycling and/or separation of valuable metals from pressure leach residue and may be integrated into one or more existing valuable element extraction processes.

Abstract: A vertical autoclave according to an embodiment of the present disclosure is a vertical autoclave including an inlet port through which a process solution is introduced, an outlet port through which the process solution is discharged, an oxygen inlet port through which oxygen is supplied to the process solution, an agitator configured to mix the process solution, an inner wall, an acid-resistant brick layer lined on a lower portion and a side portion of the inner wall, and an acid-resistant metal layer lined on an upper portion of the inner wall. A method of removing salt from an autoclave includes raising a surface level of a solution in the autoclave from a first level to a second level such that salt in the autoclave is immersed in the solution, and maintaining the surface level of the solution at the second level. The salt is dissolved in the solution while the surface level of the solution is maintained at the second level.

Abstract: A system and method for improving leach kinetics and recovery during above-atmospheric leaching of a metal sulfide is disclosed. In some embodiments, the method may comprise the steps of: (a) producing a metal sulfide concentrate [34] via flotation; (b) moving the produced metal sulfide concentrate [34] to at least one chamber [22a] of at least one reactor such as an autoclave [20]; (c) leaching the produced metal sulfide concentrate in said at least one chamber [22a] in the presence of oxygen [82] at a pressure and/or temperature above ambient, and in the presence of partially-used [25] and/or or new [92] grinding media within the at least one chamber [22a]. Systems [10] and apparatus [20, 200] for practicing the aforementioned method are also disclosed.

Abstract: A method of leaching chalcopyrite ores includes the steps of forming agglomerates of fragments of chalcopyrite ores and silver and leaching the agglomerates with suitable leach liquor.

Abstract: A process to significantly improve the copper chemical leaching process for primary and secondary minerals, using calcium chloride including the agglomeration, curing, and leaching with a high content of chloride, iron and copper stages. The mineral is then washed with a low concentration of copper and a high concentration of acid, where the impregnated copper is extracted from the pit and wherein a recirculated solution is used in the agglomeration stage.

Abstract: Provided are a sulfuric acid adding facility and an operation method therefor which enable an increase in the maximum capacity and the operation rate of a sulfuric acid supply pump provided in the sulfuric acid adding facility. In a sulfuric acid adding facility, sulfuric acid is added to an autoclave used in a leaching step of a high pressure acid leaching method for a nickel oxide ore. The sulfuric acid adding facility is provided with the same number (n+1) (n is an integer, at least 1) of each of the following: a plurality of sulfuric acid adding pipes for adding sulfuric acid into the autoclave; and a plurality of sulfuric acid supply pumps for supplying sulfuric acid to the sulfuric acid adding pipes. Each of the first through n+1th sulfuric acid supply pumps includes at least three diaphragms and discharge ports of the same number as that of the diaphragms.

Abstract: The present disclosure relates to methods for enhanced demetalyzation of an ultrahard material, such as polycrystalline diamond (PCD) or cubic boron nitride (CBN), using a thiourea solution. The thiourea solution may contain thiourea and an acid, such as a Bronstead acid suitable for leaching. The thiourea may contain thiourea or a substituted thiourea, including tautomers thereof. The ultrahard material may be exposed to the thiourea solution for a time and under conditions sufficient to remove at least a desired amount of a metal, such as a catalyst used during formation of the PCD or CBN, from at least a portion of the ultrahard material.

Abstract: Provided is a method for preparing metal powder; a metal nitrate or metal sulfate is combined with ammonia water to produce an ammonia-containing complex metal salt solution; the said solution is then quantitatively jet-mixed with the solution containing the hydroxylamine compounds, and reacted under intense stirring; a dispersant solution is added during the reaction process, and after the reaction is complete, the solution is separated by centrifugation to yield the metal power. The method of the present invention can effectively control the reaction rate during the production process, and well control the nucleation rate and dispersity, with the produced metal powder having very good crystallinity, sphericity, tap property and dispersity.

Abstract: The disclosure relates to pre-treatment of precious metal-bearing oxide ores, prior to precious metal leaching by thiosulfate. The process comprises mixing oxide ore in oxygenated water in the presence of a carbon-based material (e.g., activated carbon or other type of carbon). The carbon-based material can be separated from the ore slurry, and, the gold is thereafter leached by a thiosulfate lixiviant.

Abstract: A process for extraction of copper from an arsenical copper sulfide concentrate is provided. The process includes atmospheric oxidative leaching of a feed slurry including the arsenical copper sulfide concentrate and an acidic iron sulfate-containing leach solution, in the presence of oxygen, to produce a leach slurry including copper and arsenic dissolved into the leach solution. After dissolving the copper and arsenic, scorodite-containing seed is introduced to the leach slurry to induce precipitation of the arsenic dissolved during the oxidative leaching, as scorodite.

Abstract: This invention provides a hydrometallurgical process for extracting one or more saleable products from a sulphate or chloride pregnant leach solution (PLS), or both. The products may be any one or more of the products selected from the group consisting of: precious metals including platinum group metals (PGMs), gold and silver, base metals, and rare metal elements, and metal cathodes, powders, salts or precipitates thereof; sulphur; hydrochloric acid (HCl); calcium; and silica.

Abstract: A process for the preparation from a partially decomposed organic material like peat a granulated or pelletized sorption medium using low-temperature, thermal activation of the sorption medium to produce a high degree of granule or pellet hardness balanced against an efficacious level of ion-exchange and adsorption capacity, followed by chemical treatment of the thermally-activated sorption material via an acid solution and a salt solution to increase its ion-exchange and adsorption performance while minimizing the transfer of natural impurities found in the sorption medium to an aqueous solution is provided by this invention. The sorption medium of this invention can be used in a variety of aqueous solution treatment processes, such as wastewater treatment.

Abstract: A process for the preparation from a partially decomposed organic material like peat a granulated or pelletized sorption medium using low-temperature, thermal activation of the sorption medium to produce a high degree of granule or pellet hardness balanced against an efficacious level of ion-exchange and adsorption capacity, followed by chemical treatment of the thermally-activated sorption material via an acid solution and a salt solution to increase its ion-exchange and adsorption performance while minimizing the transfer of natural impurities found in the sorption medium to an aqueous solution is provided by this invention. The sorption medium of this invention can be used in a variety of aqueous solution treatment processes, such as wastewater treatment.

Abstract: Aqueous leachant compositions and processes for using the same comprising: (a) providing a metal-containing compound; and (b) subjecting the metal-containing compound to an acid digestion comprising contacting the metal-containing compound with an aqueous leachant; wherein the aqueous leachant comprises a mixture selected from the group consisting of: (i) sulfuric acid and one or more alkanesulfonic acids having alkane moieties selected from the group consisting of propyl, ethyl and methyl groups, at a weight ratio of alkanesulfonic acid to sulfuric acid of 1:1000 to 1:1; (ii) sulfuric acid and one or more salts of alkanesulfonic acids having alkane moieties selected from the group consisting of propyl, ethyl and methyl groups, at a weight ratio of salt of alkanesulfonic acid to sulfuric acid of 1:9 to 1:99.

Abstract: A method for selectively processing a polymetallic oxide solution containing a plurality of base metals comprising at least one of: Cu, Co, Ni, Zn associated with iron, comprising acid leaching the solution; recovering a filtered leachate; oxidizing the leachate; and adjusting the pH of the leachate in presence of a complexing agent; wherein the acidic solution is one of: i) a hydrochloric acid solution and ii) a sulfuric acid solution at a pH lower than about 1.5, and the complexing agent is one of: i) ammonium chloride and ii) ammonium sulfate, the step of adjusting the pH comprising raising the pH to a range between about 2.5 and about 3.5.

Abstract: The present invention discloses a new process for leaching sulfide minerals consisting of leaching crushed ore in a vat reactor, wherein the leaching solution is fed with an ORP value close to the upper limit suitable for leaching and the exiting leaching solution leaves the reactor with an ORP above the lower limit suitable for leaching the ore. The output leaching solution that leaves the leaching reactor goes through an iron oxidation stage outside the leaching reactor, with the iron oxidation producing soluble ferric sulfate that is mixed with a recirculated portion of the output leaching solution to increase its ORP up to a value close to the upper limit of the redox potential range that is suitable for the ore leaching.

Abstract: Disclosed are methods and compositions for improving metal extraction processes by introducing at least one cationically charged compound selected from a group consisting of amines, particularly quaternary amines such as alkyldimethylbenzylammonium chlorides (ADBAC compounds), polyamines and other suitable cationic organic materials, and mixtures thereof, for neutralizing and/or coagulating excess anionic organic compounds including, for example, flotation reagents, surfactants, polymers, flotation reagent by-products and/or anti-scalant additives found in metal concentrate streams, and thereby reduce the downstream fouling of the activated carbon by these compounds.

Abstract: The invention relates to an apparatus and method for removing molybdenum and other possible impurities from an organic copper-containing extraction solution in connection with the liquid-liquid extraction related to copper recovery. The removal of impurities occurs in one or several removal units built into the organic extraction solution storage tank.

Abstract: A method of extracting targeted metallic minerals from ores that contain sulfide metallic minerals along with oxide minerals, carbonate minerals, silicate minerals, halide minerals or combinations thereof. In the method, an ore slurry containing the metallic mineral in oxide, carbonate, silicate or halide form is provided. The slurry is activated by adding sodium thiosulfate and sodium metabisulfite, whereby the targeted metallic mineral forms an intermediary metal complex with the sodium thiosulfate and sodium metabisulfite. One or more metal release components are introduced into the ore slurry; whereby the targeted metallic mineral is released from the intermediary metal complex to form a metal sponge. This metal sponge is then subjected to a flotation process, whereby the targeted metallic mineral is drawn out of the ore slurry and thereby extracted from the ore.

Abstract: Provided is a method for separating and recovering iodine ingredients from acid solution containing iodide ions and iron (II) ions and for efficiently producing iron (III) ions. Said method is for treating acid solution containing the iodide ions and the iron (II) ions. Said method comprises a step of oxidizing the iron (II) ions in said solution into iron (III) ions with iron-oxidizing microorganisms, the step being performed in the presence of activated carbon.

Abstract: A method for producing an iron (III) ion from the acidic solution containing an iodide ion and an iron (II) ion efficiently and stably is provided. The method including performing the following steps (a)-(b), repeatedly and continuously: (a) a step wherein the iron (II) ion in the acidic solution containing the iodide ion and the iron (II) ion is oxidized into iron (III) ion in a reactor using a microbes immobilizing carrier to which iron oxidizing microbes attached; (b) a step wherein sedimentation of the solution obtained in the step (a) is performed in a sedimentation tank to obtain the solution containing the iron (III) ion and concurrently the sediment of the microbes immobilizing carrier to which the iron oxidizing microbes have attached is recovered and then reintroduced into the reactor in the step (a).

Abstract: A method of recovering copper from chalcopyrite concentrate by chemical leaching, using pyrite and silver. The catalytic properties of pyrite in the chalcopyrite leaching process are significantly enhanced by pretreating the pyrite with silver ions. Particulate pyrite is exposed to a solution containing silver ions to form silver-treated pyrite. Particulate chalcopyrite and the silver-treated pyrite are mixed in an acidic sulfate leach solution. The copper is leached from the concentrate in the leach solution in the presence of an oxygen-containing gas, under conditions whereby the pyrite is substantially unoxidized. The leached copper is recovered from the solution by conventional methods. The used silver-treated pyrite is recycled to the leaching process.

Abstract: A method for selectively removing arsenic from a sulphide material containing arsenic by conducting a leaching step that includes contacting the material with a leaching solution that leaches arsenic from the material to form a pregnant liquor containing dissolved arsenic and a solid of a sulphide material of reduced arsenic content, and subsequently separating the solid from the pregnant liquor. The fresh leaching solution that is provided to the leaching step is an alkaline solution having a sulphide-containing compound present in an amount of from 0 to 1.0 times the amount of sulphur containing compound required to react with the arsenic present in the material.

Abstract: A method of removing mercury adsorbed onto activated carbon is provided. The method includes treating an adsorbed mixture of metal cyanide complexes on a carbon substrate with an acidic solution of a stripping agent that is a weak acid. The method also eliminates inorganic scalants from the carbon substrate. In precious metal mining operations, the disclosed method reduces environmental emissions of mercury during the gold elution and carbon reactivation processes.

Abstract: Methods and compositions are described for preparing metal salts and selectively separating metals from substrates and other metals. The methods can include a thionyl reagent that reacts with a metal in a solution to produce a metal salt. The reaction can be controlled by varying reagents and conditions such that the method can be used to selectively separate one or more metals from another metal or from a substrate. The method can also be used for removing metals from a surface. Compositions produced by the method are also described.

Abstract: The invention discloses an additive for bioleaching that makes it possible to increase the recovery of copper from sulfide ores. In which this additive is substantially made up of the Licanantase lipoprotein and a solution of sulfuric acid with a pH of 0.8 to 3. The Licanantase lipoprotein that has an amino acid sequence with at least 50% homology regarding the sequence defined in SEQ ID No. 1 or is the product of translation of a nucleotide sequence with at least 50% homology regarding the sequence defined in SEQ ID No. 2. It also protects the improved bioleaching process that includes adding the additive during the ore bioleaching process as defined in the present invention; and continuing with the habitual process, obtaining copper recoveries increased 5 to 20%.

Abstract: A method of recovering metal from heap leached ore is provided. The method includes supplying process fluid to a tank, distributing heap leached ore in the tank, optionally disrupting the flow of ore through the tank, creating a pregnant solution and discharging the process fluid, heap leached ore and pregnant solution from the tank to recover additional metal from the heap leached ore.

Abstract: A method for recovering a metal, capable of recovering a metal easily without requiring the use of an organic medium, is provided. A complex between a chelating agent and a metal present in a sample is formed in a mixture prepared by mixing the chelating agent and the sample under pH conditions where the chelating agent can be insoluble in an aqueous medium. Then, the complex is recovered from the mixture, and further, the metal is recovered by dissolving the recovered complex in an aqueous medium under pH conditions that are different from the pH conditions where the chelating agent can be insoluble in an aqueous medium. By this method, a metal can be recovered easily without requiring the use of the use of an organic medium.

Abstract: A topical formulation for application to exposed body tissue, the formulation comprising a silver(II) oxide and zinc oxide, intimately dispersed within a carrier medium.

Abstract: A method of selectively leaching a metal such as nickel from an ore or ore processing intermediate comprising the metal and cobalt. The ore or ore processing intermediate is contacted with an acidic leach solution comprising an amount of an oxidising agent sufficient to oxidise a major portion of the cobalt to thereby cause it to be stabilised in the solid phase while a major portion of the metal is dissolved for subsequent recovery.

Abstract: Processes for recycling electronic components removed from printed wire boards, whereby precious metals and base metals are extracted from the electronic components using environmentally friendly compositions. At least gold, silver and copper ions can be extracted from the electronic components and reduced to their respective metals using the processes and compositions described herein.

Abstract: The invention relates to a method for separating nickel and other valuable metalsparticularly from material having low nickel content, which contains iron and magnesium in addition to nickel and other valuable metals. The material havinglow nickel content is subjected to pulpingand atmospheric leaching in acidic and oxidising conditions, in which the majority of the metals in themate-rialdissolve and the iron is partially precipitated. The precipitated iron is sepa-rated from the solution, after which nickel and the other dissolved valuable metalsare precipitated as sulphides.

Abstract: A method of recovering copper from chalcopyrite concentrate by chemical leaching, using pyrite and silver. The catalytic properties of pyrite in the chalcopyrite leaching process are significantly enhanced by pretreating the pyrite with silver ions. Particulate pyrite is exposed to a solution containing silver ions to form silver-treated pyrite. Particulate chalcopyrite and the silver-treated pyrite are mixed in an acidic sulfate leach solution. The copper is leached from the concentrate in the leach solution in the presence of an oxygen-containing gas, under conditions whereby the pyrite is substantially unoxidized. The leached copper is recovered from the solution by conventional methods. The used silver-treated pyrite is recycled to the leaching process.

Abstract: Various embodiments provide new methods of rhenium recovery. The methods can include subjecting a metal-bearing solution to an activated carbon bed, and adsorbing rhenium onto the activated carbon. The methods can also include heating a basic aqueous elution solution and eluting the rhenium from the activated carbon with the heated elution solution. The methods can also incorporate an ion exchange as a rhenium recovery apparatus.

Abstract: A method recovers noble metals from noble metal-containing compositions and includes steps of (i) providing a noble metal-containing composition containing an adsorption agent that is based on an inorganic material and is functionalized by organic groups and has at least one noble metal adsorbed to it, and (ii) ashing of the noble metal-containing composition provided in step (i) in order to adjust a residual carbon content of at most 10% by weight, relative to the total weight of the noble metal-containing composition after ashing, to obtain an ashed composition.

Abstract: Methods and apparatuses for separating metal values, such as nickel and nickel compounds, from mineral ores, including lateritic ores are disclosed. The method includes providing a mixture of particles (e.g., crushed and sized ore) that is composed of at least a first group of particles and a second group of particles. Group members have similar chemical composition, while particles belonging to different groups have dissimilar chemical compositions. The mixture of particles is concurrently, or generally concurrently, heated (using microwave/millimeter wave energy) and exposed to a reactant. The wave energy and the reactant act to increase the difference in either the magnetic susceptibility or other separation properties between the first and second group of particles. The mixture of particles is then passed through an appropriate separator to separate the particles of interest. Optional steps are disclosed for purifying selected particles.

Abstract: Provided is a method for separating and recovering iodine ingredients from acid solution containing iodide ions and iron (II) ions and for efficiently producing iron (III) ions. Said method is for treating acid solution containing the iodide ions and the iron (II) ions. Said method comprises a step of oxidizing the iron (II) ions in said solution into iron (III) ions with iron-oxidizing microorganisms, the step being performed in the presence of activated carbon.

Abstract: A method of recovering minerals from hydrocarbonaceous materials can include forming a constructed permeability control infrastructure. This constructed infrastructure defines a substantially encapsulated volume. A comminuted hydrocarbonaceous material can be introduced into the control infrastructure to form a permeable body of hydrocarbonaceous material. The permeable body can be contacted with an agent sufficient to remove minerals therefrom. The agent is typically a solution containing a solvent, leachant, chelating agent and the like via which minerals can be removed having value, toxic minerals, radioactive minerals and the like.

Abstract: Various embodiments provide new methods of rhenium recovery. The methods can include subjecting a metal-bearing solution to an activated carbon bed, and adsorbing rhenium onto the activated carbon. The methods can also include heating a basic aqueous elution solution and eluting the rhenium from the activated carbon with the heated elution solution.

Abstract: A process for recovering a target metal from an oxidized metalliferous material comprises the steps of: in an acid generation stage, adding sulfuric acid to a solution comprising a metal halide to generate an acidic aqueous halide solution; in a leaching stage that is separate to the acid generation stage, leaching the oxidized metalliferous material with the acidic aqueous halide solution to leach the target metal into solution; passing the solution from the leaching stage to a target metal recovery stage in which the target metal is recovered from the solution while the metal halide is retained in solution; and returning the solution with the metal halide therein from the target metal recovery stage to the acid generation stage.

Abstract: A method of sequestering carbon dioxide emissions during recovery of hydrocarbons from hydrocarbonaceous materials can include forming a constructed permeability control infrastructure. This constructed infrastructure defines a substantially encapsulated volume. A comminuted hydrocarbonaceous material can be introduced into the control infrastructure to form a permeable body of hydrocarbonaceous material. The permeable body can be heated sufficient to remove hydrocarbons therefrom. During heating, the hydrocarbonaceous material is substantially stationary as the constructed infrastructure is a fixed structure. Additionally, during heating, any carbon dioxide that is produced can be sequestered. Removed hydrocarbons can be collected for further processing, use in the process, and/or use as recovered.

Abstract: Disclosed is a method of efficiently leaching copper not only from a readily-soluble copper ore but also a poorly-soluble copper sulfide ore partially containing or consisting of chalcopyrite and/or covellite by means of ore heap leaching under versatile conditions for actual operation. Also disclosed is a method of leaching copper from a copper sulfide ore, including leaching copper from an ore including a copper sulfide ore by heap or dump leaching with the use of a sulfuric acid solution containing ferric (III) ions and iodide ions at a total iodine concentration of 8 to 100 mg/L as a leaching solution.

Abstract: A method of extracting Te and bismuth oxide and recovering byproduct comprises: leaching raw materials with a Te content of ?1.8% by utilizing a leaching system containing H2SO4, Cl?, Br?, NH4+ and NaClO3, reducing leach solution with SO2 gas by precipitation method after separating impurities from it, washing with concentrated hydrochloric acid to obtain tellurium precipitation (18), purifying to obtain Te with a purity of higher than 99.99%. The filtrate produced is used for extracting Bi2O3 with a purity of higher than 99.99% when Bi content in the raw material is ?2%. Acidic waste solution produced during the process could be returned to the leaching step for recycle.

Abstract: A method of recovering copper from a copper sulfide concentrate comprising a copper arsenic sulfosalt or a copper antimony sulfosalt, using pyrite as a catalyst. The concentrate and pyrite are added to an acidic sulfate leach solution. The copper is leached from the concentrate, in the presence of an oxygen-containing gas, under conditions whereby the pyrite is substantially unoxidized. The pyrite:copper sulfide ratio of the pyrite being added to the copper sulfide present in the concentrate being added is at least 1:3. The pyrite may be maintained at a concentration in the leach solution of at least 9 grams per liter. The leached copper is recovered from the solution by conventional methods.

Abstract: Disclosed is a method of copper leaching without reducing the growth of iron-oxidizing bacterium and the iron-oxidizing capacity when leaching copper from a copper sulfide ore with the use of a sulfuric acid solution to which iron-oxidizing bacteria and silver have been added. Also disclosed is a method of leaching copper from a copper sulfide ore, including adding a naturally occurring nitrogen-containing organic component to a leaching solution upon copper leaching from a copper sulfide ore with the use of, as the leaching solution, a sulfuric acid solution to which iron-oxidizing bacteria and silver have been added is provided.

Abstract: A method of conducting a bioleaching process including the steps of forming a main heap, culturing at least one microorganism which exhibits bioleaching activity in a predetermined temperature range, monitoring the temperature in the main heap, which is a result, at least, of microbial leaching activity and inoculating the heap with the cultured microorganism at least before the temperature reaches the predetermined range.

Abstract: A method of leaching copper sulfide ore includes leaching copper from copper sulfide ore using a sulfuric acid solution comprising iodide ion and iron (III) ion surplus to the iodide ion as a leaching solution; reducing iodine in a solution obtained after the leaching step to less than 1 mg/L by an activated carbon treatment; and oxidizing iron (II) ion or newly added iron (II) ion in a solution obtained after the iodine reduction step by using iron oxidizing microbes to recover iron (III) ion.

Abstract: An object of the present invention is to provide a method of efficiently leaching copper from a copper sulfide ore containing chalcopyrite or enargite as a main constituent under versatile conditions for actual operation. A method of leaching copper from a copper sulfide ore, characterized by comprising using, as a leaching solution, a sulfuric acid solution containing iodide ions and ferric (III) ions in an excessive amount relative to the iodide ions and leaching copper from a copper sulfide ore; or a method of leaching copper from a copper sulfide ore, characterized by comprising leaching copper from a copper sulfide ore with the use of a leaching solution further containing water-soluble ligands such as chloride ions that can stabilize ferric (III) ions in addition to the above components, is provided.

Abstract: A system for cooling and recuperative heating of a slurry in a metallurgical process which includes heat exchangers, pumps and autoclaves is described herein. The heat exchangers use a non-scaling common liquid heat transfer medium. Preferably, the heat exchangers are tube-in-tube heat exchangers with 3 to 7 slurry tubes in each heat exchanger. An advantage of this system is that it does not use flash tanks. To minimize abrasive wear on impinged surfaces, the velocity of the slurry is not more than 5 meters per second. The slurry comprises a solids concentration of 25% to 50%. Preferably, the pumps in the system are float-type pumps in which the driven liquid from the discharge pumps is also used as the drive liquid for the feed pumps.