WO2025053758A1

WO2025053758A1 - Ammonium nitrate production with multiple condensers

Info

Publication number: WO2025053758A1
Application number: PCT/NL2024/050490
Authority: WO
Inventors: Rahul Patil; Solomon Assefa WASSIE
Original assignee: Stamicarbon BV
Current assignee: Stamicarbon BV
Priority date: 2023-09-08
Filing date: 2024-09-09
Publication date: 2025-03-13
Anticipated expiration: 2026-03-08

Abstract

The disclosure pertains to the production of ammonium nitrate using a neutralizer that is provided with multiple condensers for the vapor from the neutralizer.

Description

P135531PC00 Title: AMMONIUM NITRATE PRODUCTION WITH MULTIPLE CONDENSERS Field [0001] The invention pertains to the production of ammonium nitrate by the neutralization of nitric acid with ammonia. Introduction [0002] The invention pertains to the production of ammonium nitrate (NH₄NO₃; abbreviated AN) by the reaction of gaseous NH3 with aqueous nitric acid (HNO₃; abbreviated NA), under the release of steam. The steam is condensed and the resulting steam condensate is used at least in part elsewhere in the plant. [0003] G.R. Maxwell, Synthetic Nitrogen Products (2005), p.251-265, chapter Ammonium Nitrate, DOI: 10.1007/0-306-48639-3_10 describes various processes and apparatuses for AN production. Fig. 10.4 of said document illustrates the Stamicarbon AN process wherein steam from the neutralizer is condensed in two condensers in parallel, a first condenser configured for indirect heat exchange with the AN solution, i.e. steam to be condensed in the shell and AN solution in the tubes, and a separate parallel surplus steam condenser. The steam condensate from both condensers is combined and supplied to an ammonia scrubber. Vapor from the scrubber is condensed and purged to the reactor to recover NH3. Liquid from the scrubber bottom is recovered as steam condensate. Fig. 10.2 of said document illustrates the Uhde AN process wherein vapors are separated from the AN solution and scrubbed. The vapor scrubbing units are said to produce a liquid effluent that contains as little as 15 ppm N. The document mentions on p.258 that AN emissions from the neutralizers are very difficult to remove due to the very fine particles. A further background reference is Ullmann's Encyclopedia of Industrial Chemistry, chapter Ammonium Compounds, 2012, DOI: 10.1002/14356007.a02_243. [0004] The brochure Nitrates for fertilizers and technical applications of Thyssenkrupp (formerly Uhde) mentions that in the illustrated AN production process, the vapors formed in the ammonium nitrate neutralization and evaporation process are scrubbed either in the vapor separator direct or in a separate scrubbing column. Depending on the quality of the process vapors, a single or dual-stage scrubber is applied. The scrubbed process vapors are used for feedstock preheating, while surplus vapors are condensed. Production of process condensate with e.g. 15 ppmw nitrogen is mentioned. The illustrated process scheme uses a number of condensers in parallel, each configured for indirect heat exchange with a different stream to be heated respectively cooling water. [0005] One of the uses of AN is the production of UAN (urea ammonium nitrate), which can be used as a liquid fertilizer. Fertilizer grade UAN typically contains 40 – 45 wt.% AN, 30 – 35 wt.% urea, and 30-20 wt.% water. Summary [0006] The invention aims to provide for a process and plant for AN production wherein the handling of the vapor and condensate is improved. [0007] The invention pertains in a first aspect to a process for the production of ammonium nitrate comprising, reacting NH3 and nitric acid in a neutralizer reactor to give an ammonium nitrate solution and a first vapor stream; subjecting said first vapor stream to condensation in a first condenser to give a first condensate stream and a second vapor stream; and subjecting the second vapor stream to condensation in a second condenser to give a second condensate stream; wherein the first and the second condensate stream are obtained as separate streams. [0008] The invention also provides an ammonium nitrate production unit comprising: a reactor comprising a reaction zone having an inlet for nitric acid and an inlet for NH3, and a separation zone for gas/liquid separation of effluent from the reaction zone with an ammonium nitrate solution outlet, a first vapor outlet , and a recirculation line for ammonium nitrate solution to the reaction zone, wherein the reactor comprises a restriction orifice for the effluent between the reaction zone and the separation zone and the recirculation line comprises a pump; first condenser connected to said first vapor outlet and having a first condensate outlet and a second vapor outlet; and a second condenser connected to said second vapor outlet of the first condenser and having a second condensate outlet, wherein said first and second condensate outlets are separate outlets. [0009] The invention also provides a plant comprising the inventive ammonium nitrate production unit; and a nitric acid production unit comprising a burner section and an absorber. [0010] The invention also provides a method of modifying an existing ammonium nitrate production unit. [0011] Hence, generally, the invention pertains to the production of ammonium nitrate using a neutralizer that is provided with multiple condensers for the vapor from the neutralizer. Brief description of the drawings [0012] Figure 1 schematically illustrates an example embodiment of a process and plant of the invention. [0013] Figure 2 schematically illustrates an example embodiment of the reactor used in the invention. [0014] Figure 3A schematically illustrates an example UAN unit used in embodiments of the process and plant of the invention. [0015] Figure 3B schematically illustrates an example NA production unit used in embodiments of the process and plant. [0016] Any embodiments illustrated in the figures are examples only and do not limit the invention. Detailed description [0017] The invention is generally based on the judicious insight of providing the AN neutralizer with a condensation section for the vapor released from the neutralizer, wherein the condensation section comprises a first and a second condenser in series. The second condenser receives vapor from the first condenser. The first and second condenser each have a condensate outlet, to provide two distinct condensate streams with a different composition. Advantageously, the condensate from the second condenser has a high purity, enabling the flexible disposal, especially if this condensate stream constitutes excess water from the AN production. [0018] In the inventive process, ammonia (in particular NH3 gas) and nitric acid (preferably aqueous nitric acid; NA) are reacted in a reactor (comprising a neutralization zone and a separation zone; and referred to as a neutralizer reactor) to give an ammonium nitrate solution and a first vapor stream. In the process, the water in the nitric acid solution is evaporated by the heat of the neutralization reaction and the first vapor stream is essentially steam, however with entrained droplets which include (dissolved) ammonium nitrate. This entrainment causes the condensate obtained by condensation of the first vapor stream to contain impurities. In the process, an effluent from the neutralization zone is supplied to the separation zone and is subjected to gas/liquid separation in the separation zone. [0019] Preferably, the first vapor stream is formed in the separation zone and a monophasic liquid stream is transferred from the neutralization zone to the separation zone, preferably through pressure reduction means, for example a restriction orifice. Preferably, in the process, the separation zone is operated at a lower pressure than the neutralization zone and the transfer of fluid effluent from the neutralization zone to the separation zone causes expansion of the effluent and (flash) evaporation of H2O contained in the effluent to form a vapor that is separated from the liquid in the separation zone. The evaporation provides for cooling of the liquid. The liquid is ammonium nitrate solution that is in part recirculate to the neutralization zone and in part obtained as a product. The ratio recycle to product solution is e.g. above 5, above 10, or above 20; usually less than 60. [0020] A first part of the ammonium nitrate solution is recirculated as diluent to the reaction zone for heat management and a second part is purged as product; the ratio of recycle to purged product is usually at least 5, e.g. at least 10 or at least 20. The heat of the exothermic neutralization reaction is at least in part withdrawn by the first vapor (which is mainly steam) and can be withdrawn, at least in part, by condensation of the first vapor, and be transferred at least in part to a cooling liquid. Accordingly, the flashing contributes to heat management in the reaction zone. [0021] The reaction zone is operated with a (small) excess of HNO3 to NH3 (molar ratio above exactly 1), which permits that all NH3 is converted into ammonium nitrate in the neutralization zone, assuming thorough mixing of the feeds and recycled AN solution, such that the liquid at the outlet of the reaction zone contains no or negligible unreacted NH3. The purged stream is usually subjected to a final neutralization of the unreacted NA by addition of NH3; for example the urea-containing liquid stream that is combined with the purged AN solution to make UAN contains some NH3. [0022] In an example embodiment, the reactor is as described in Australian Patent AU654632B1. [0023] In an example embodiment, the reactor comprises a mixing zone receiving aqueous nitric acid and recirculated ammonium nitrate solution, a shell- and-tube chamber configured for receiving a liquid mixture of ammonium nitrate solution and aqueous nitric acid in the tubes and gaseous NH3 in the shell space, and a reaction zone connected to the outlet ends of the tubes. The tubes comprise perforations in the wall to admit gaseous NH3 into the liquid in the tubes. Optionally, one or more static mixing elements are provided between the outlet tube ends and the outlet of the reaction zone, to ensure that any unreacted NH3 at the tube outlets is converted into ammonium nitrate in the reaction zone. A background reference for such a reactor design is Australian Patent AU654632B1. [0024] The aqueous nitric acid (nitric acid solution) contains e.g. at least 10 wt.% water, or at least 20 wt.%, typically less than 50 wt.%; and typically contains at least 50 wt.% nitric acid, preferably at least 60 wt.% nitric acid, and typically less than 68 wt.% nitric acid. [0025] Preferably, the ammonia and aqueous nitric acid solution are reacted in a reaction zone comprised in the first reactor to give a first effluent and this first effluent is subjected to gas/liquid separation in a separation zone. More preferably, the first effluent is passed through a restriction orifice. Preferably, the effluent that is passed through the restriction orifice is in the liquid phase. In this way, transport of gaseous NH3 to the gas/liquid separation zone is avoided. Thereby advantageously the first vapor stream preferably contains less NH3. Also the level of AN dust can be relatively low. [0026] Preferably, the reaction zone is operated at higher pressure than the separation zone, preferably at least 0.1 bar higher or at least 0.5 bar higher. For instance, the reaction zone is operated at a pressure of at least 1 bara, such as 1.0 – 2.0 bara, e.g. about 1.5 bara. The separation zone is for example operated at a pressure below 1 bara, e.g. at a pressure of less than 0.8 bara, or less than 0.50 bara, typically above 0.10 bara, e.g. in the range 0.25 – 0.40 bara. The first and second condenser are preferably operated as substantially the same pressure as the separation zone, e.g. max. 0.1 bar lower than the separation zone. The first and second condenser are preferably operated at a pressure below 1 bara, e.g. at a pressure of less than 0.8 bara, or less than 0.50 bara, typically above 0.10 bara, e.g. in the range 0.25 – 0.40 bara. [0027] Preferably, the reaction zone is operated at a temperature below the boiling point temperature of the reactor effluent at the pressure in the reaction zone. This advantageously prevents gaseous ammonia slip into the separation zone. [0028] Typically, a part of the ammonium nitrate solution is recirculated to the reaction zone, suitably using a circulation pump. Hence, preferably the process uses forced circulation. [0029] The first vapor stream is for instance scrubbed, or is not, using an aqueous scrub liquid to remove entrained droplets and/or dust, which contains entrained AN and NA, upstream of the first condenser. In embodiments wherein such scrubbing is used, the resulting spent scrub liquid is e.g. added to the AN solution. The scrubbing e.g. involves counter-current contact of the scrub liquid and the first vapor stream. The scrubber is for instance a tray scrubber. The scrubber may be a scrubbing zone of the reactor. [0030] In the process, the first vapor stream is subjected to condensation in a first condenser to give a first condensate stream and a second vapor stream. The condensation involves gas/liquid separation of the second vapor stream from the first condensate stream. The condensate is aqueous. The second vapor stream comprises steam with entrained droplets and/or dust, usually with inert gases originating from NH3 feed, and possibly gaseous NH3. The entrained droplets and dust contain AN and nitric acid. Usually, selectively the second vapor stream is supplied to the second condenser; usually less than 10 wt.% of the first condensate stream is supplied to the second condenser. [0031] The first condenser has an inlet for the first vapor stream and an outlet for the first condensate stream and a separate outlet for the second vapor stream, and is e.g. a shell-and-tube heat exchanger. The first condenser is preferably a surface condenser or a falling-film shell-and-tube condenser with gas to be condensed in the shell. The first condenser is for instance a falling-film condenser with an outlet for the second vapor stream located in a bottom part of the shell. Other designs of the condenser may also be used. [0032] A judicious insight of the inventors is that the second vapor stream is cleaned compared to the first vapor stream, i.e. has a lower content of ammonium nitrate. A part of the steam condenses in the first condenser resulting in dissolving of dust and capture of entrained droplets from the first vapor, which contributes to a cleaner second condensate. [0033] The first condenser is preferably operated with substantially the same pressure as the separation zone, such as a pressure of below 1.0 bara. [0034] The first condensation is hence preferably partial condensation. For example, max. 5/6 (83.3%) by weight or mole of the H2O in the water vapor in the first vapor stream is condensed in the first condenser, or max. 80%, or max.75%, and preferably the weight ratio of first to second condensate is preferably max. 5.0, or e.g. max. 4.0. [0035] The first and second condensation preferably individually, more preferably both, use heat exchange against a cooling liquid, such as e.g. cooling water. [0036] In the process, the second vapor stream is subjected to condensation in a second condenser to give a second condensate stream and, typically, a third vapor stream. The second condensate is aqueous. The second vapor stream is preferably directly supplied to the second condenser, without purification between the first and the second condenser. [0037] The first and second condenser together constitute a condensation section. Optionally, the first and second condenser are independently provided as one or more condenser apparatuses, provided that different condenser apparatuses are used for the first and second condenser. [0038] Typically, the second vapor stream is supplied directly to the second condenser by a gas flow transport line. [0039] The second condenser is preferably operated with a pressure the same as or lower than the first condenser, e.g. max. 0.05 bar lower; and/or with a pressure below 1.0 bara. For instance, the second condenser is operated with a pressure slightly lower than the first condenser, e.g. 0.01 – 0.05 bar lower; and/or with a pressure below 1.0 bara. Hence, the first and second condenser are preferably vacuum condensers. [0040] The first condenser and second condenser are separate units, and the plant typically comprises a flow line, e.g. duct or pipe, for second vapor from an outlet of the first condenser to an inlet of the second condenser. The outlet of the first condenser for condensate is separate and distinct of the outlet of the second condenser for condensate. The first condensate and the second condensate are obtained as separate streams and have a different composition. [0041] Typically, the first condensate and the second condensate are obtained as separate streams from the respective outlets and this can be implemented by supplying these streams into separate liquid flow lines (piping) connected to the respective outlets. [0042] The usual third vapor stream usually mainly includes inert gases originating from the NH3 feed along with air ingress for pressure control of the vacuum condensers. In embodiments with nil inert gases in the NH3 feed the second condenser can achieve a very high degree of condensation. [0043] The third vapor stream can be withdrawn from the second condenser using an ejector, e.g. a steam-driven ejector, and be brought to atmospheric pressure. The third vapor stream is e.g. vented or supplied to a suitable (acidic) scrubber. [0044] The second condenser is preferably shell-and-tube heat exchanger with vapor to be condensed in the shell and cooling fluid (e.g. cooling water) in the tubes; preferably with a configuration wherein the tubes are not submerged in liquid in operation. The second condenser is for example a surface condenser, i.e. a shell- and-tube condenser with cooling fluid (cooling water) in the tubes and with gas to be condensed in the shell. The surface condenser has typically a vertical or horizontal tube bundle. The second condenser is for example a surface condenser with a vertical tube bundle, with an inlet for vapor in an upper part of the shell, with an outlet for the third vapor stream located in a bottom part of the shell, and with a liquid outlet from the shell for second condensate in a bottom part of the shell, usually provided lower than the vapor outlet. In embodiments wherein the second condenser is a surface condenser with a horizontal tube bundle, preferably in operation a liquid level is maintained below the horizontal tube bundle. Especially if the second condenser is a surface condenser, the second condenser is preferably operated below 1 bara, e.g. at a pressure of less than 0.8 bara, or less than 0.50 bara, typically above 0.10 bara, e.g. in the range 0.25 – 0.40 bara. [0045] The second condensate was found to have a lower content of N than the first condensate. This advantageously enables different uses of the first and second condensate. [0046] The second condensate preferably contains maximum 40 ppm by weight AN, or maximum 30 ppm by weight AN, and e.g. in the range 10 – 40 ppm by weight AN or in the range 10 – 30 ppm by weight AN. The inventive process preferably comprises a step of making available at least a part of the second condensate as an aqueous stream having AN levels in said ranges. [0047] In a preferred embodiment, the second condensate preferably contains at least 90 mol% of the H2O comprised in the second vapor stream. [0048] In a preferred embodiment, at least 90 mol% of the H2O comprised in the second condensate, or all thereof, originates from the second vapor stream. Correspondingly, preferably no large amounts of aqueous liquid are added in the second condenser. This helps to ensure good and efficient condensation in the second condenser, e.g. in case of a surface condenser, with the formation of a desired quantity of relatively pure second condensate. Preferably, especially in this embodiment, in the weight ratio between the first and second condensate is at most 5:1, e.g. is in the range of from 1:5 to 5:1. Hence, the first condenser is operated with partial condensation (condensing max. 83% of the water vapor) permitting an advantageously large amount of relative pure second condensate to be obtained in the downstream second condenser. Preferably in this embodiment, the second condensate preferably contains maximum 40 ppm by weight AN, or maximum 30 ppm by weight AN, e.g. in the range 10 – 30 ppm by weight AN. Preferably in this embodiment, wherein at least 90 mol% of the H2O comprised in the second condensate originates from the second vapor stream, at least a part of the second condensate is supplied to a treatment unit, such as a polishing unit and/or ion exchange unit. Not diluting the second condensate upstream such a unit contributes to efficient AN removal in the treatment unit. [0049] Moreover, the high fraction of the water in the second condensate that originates from the second vapor reflects that the high purity of the second condensate is achieved by the purifying action of the upstream first condenser and not by diluting the second condensate with a clean aqueous stream in or after the second condenser. Especially for second condensate supplied to a polishing unit, not diluting the condensate provides advantages for the polishing. [0050] In a preferred embodiment, the second condenser has an inlet for the vapor stream to be condensed and the stream at the inlet contains less than 1.0 vol.% liquid relative to the total stream, e.g. as entrained droplet, thereby the liquid from the liquid outlet of the second condenser advantageously is essentially formed by the vapor condensation. [0051] The first and second condensate are separately disposed of. Hence, the first and second condensate are not completely mixed and combined into a single stream. Preferably, from the first and second condenser two parallel condensate streams are provided with a different AN concentration that are supplied, for at least a part of each stream, to different units. [0052] In a possible embodiment, a part of the first condensate may be mixed with at least a part of the second condensate; or a part of the second condensate may be mixed with at least a part of the first condensate. The inventive process provides two different process condensate streams having a different composition, in particular having a different level of dissolved ammonium nitrate. [0053] Hence, in a typical embodiment, these two process streams originate from the first and second condenser and are made available as separate process streams, typically are provided in separate liquid flow lines. These process condensate streams, or at least a part of each stream, are supplied to different units. [0054] Preferably, at least a part of the second condensate is not mixed with the first condensate. In this way, the non-mixed part of the second condensate is obtained as a relatively pure aqueous stream. [0055] In an embodiment, the first and second condensate stream are not mixed. [0056] In a preferred embodiment, at least a part of the first condensate is used in a first unit and at least a part of the second condensate is used in a different, second, unit. Typically, the first and second are separate, distinct units, that are separated from each other; for example are provided in separate housings. [0057] In a preferred embodiment, the process includes using the second condensate (at least in part) as a clean process condensate, typically the process includes supplying the second condensate, at least in part, to a unit using a clean aqueous stream; typically to a unit requiring any aqueous stream supplied to it to have an AN level of 0 - 40 ppm by weight AN, more preferably 0 – 30 ppm by weight AN. [0058] The second condensate stream is preferably used at least in part as boiler feed water (BFW), i.e. converted into steam, after a suitable condensate treatment, such as polishing. For instance, ion exchange treatment can be used (based on ion exchange resins). The treatment is more economical with lower impurities in the condensate, for a fixed condensate flow rate (kg/hr); diluting condensate with clean water upstream of the condensate treatment is not beneficial. Other treatment options for the condensate include, e.g. purification with an evaporator, multi effect evaporator, vapor recompression evaporator, reverse osmosis, electro dialysis; combinations are also possible. However, these methods all have disadvantages (costs) and for all these methods a low level of initial impurities in the condensate to be treated is desired. Discharge to the environment is typically not permitted or not desirable without purification. [0059] The second condensate is preferably sent in part or entirely to a condensate treatment unit, known as polishing unit, which uses e.g. contact with an ion exchange resin, to give a purified condensate. This purified condensate can be used e.g. as BFW, but also for other uses that need highly pure water streams. [0060] Preferably, a part or all of the second condensate stream is treated in a polishing unit and/or an ion exchange treatment unit, e.g. by contact with an ion exchange resin, and the polishing unit receives more second condensate (kg/hr) than first condensate (kg/hr), i.e. on a mass basis. For example, the polishing unit receives no first condensate. This is advantageous for the operating costs of the polishing per kg condensate treated in it that originates from the first vapor. [0061] It is noted that there is a demand for BFW in fertilizer plants, in particular for cooling, for example in nitric acid plants where BFW is used for cooling. [0062] The first condensate is preferably used, in part or entirely, preferably for at least 50 wt.% or at least 90 wt.%, for one or more uses selected from the group consisting of: 1. treating a gas stream by counter-current contact between a liquid originating at least in part from the first condensate and the gas stream, to remove one or more components from the gas stream, and 2. as diluent of a liquid stream containing at least 10 wt.% urea and/or at least 10 wt.% ammonium nitrate, preferably by adding it to such a liquid stream optionally after combining the first condensate or part thereof with another stream. [0063] Said use 1 for example includes use as a scrub liquid in a scrubber, and use as absorption liquid in an absorption column, wherein the scrubber and the absorption column receive a gas stream to be treated. [0064] Said use 2 for example includes adding the first condensate optionally in combination with another stream, to a urea solution that is included in UAN product or by adding it to the AN solution or to the feed of the neutralization. [0065] A part of the second condensate is optionally also used for said uses 1 and 2. [0066] The first condensate is for example used at least in part for scrubbing the first vapor stream. It may also be used as scrub liquid in another scrubber, e.g. for an acid scrubber of a of a urea melt plant, e.g. in the finishing section (granulator, prilling tower) of the urea melt plant or in another section of the urea melt plant. [0067] The first condensate is for example used at least in part as absorption liquid of the absorption column of the nitric acid production plant where the feed nitric acid solution is produced. The nitric acid plant is for instance based on the Ostwald process wherein ammonia is oxidized and the resulting NO2 is absorbed in water to form nitric acid. [0068] Preferably, the weight ratio between the first and second condensate is at least 1:5 and/or up to 5:1. If the weight ratio exceeds 5:1, there can be excess of first condensate in view of the specified maximum water content of UAN to be produced by mixing the AN solution with a urea solution having a specified water content. For instance, it is attractive to combine the AN solution with a urea solution having a relatively high water content to form UAN as converting the urea synthesis solution into a more concentrated urea solution is more energy consuming. [0069] If the weight ratio is less than 1:5, the removal of AN traces from the vapor in the first condenser can be limited. [0070] The AN solution is preferably used in part or entirely, preferably at least 90 wt.%, for making UAN. The UAN preferably comprises at least 30 wt.% AN, at least 20 wt.% urea, and at least 10 wt.% water and preferably less than 50 wt.% water. More preferably, the UAN contains 40 – 45 wt.% AN, 30 – 35 wt.% urea, and 30-20 wt.% water. Hence, preferably, the AN solution is combined with a urea-containing liquid stream, wherein preferably the urea-containing liquid stream contains at least 60 wt.% urea and/or up to 90 wt.% urea; preferably 60 -80 wt.% urea or 60 – 75 wt.% urea. Urea wt.% is including biuret. Preferably, the AN solution from the outlet of the neutralizer reactor is not concentrated by water removal (water evaporation) before being combined with the urea-containing liquid stream. [0071] In a preferred embodiment, at least 60 %, more preferably at least 90 %, e.g. wt.%, of the amount of water that is comprised in the first condensate is included in the urea ammonium nitrate liquid stream. [0072] The urea-containing liquid stream is preferably urea solution (which term includes a melt) from a urea plant containing at least 60 wt.% urea or at least 70 wt.% urea, and e.g. up to 99 wt.% urea, preferably up to 90 wt.% or up to 80 wt.% or up to 75 wt.%. Preparation of urea solutions with higher water content is less energy consuming as less concentration of the urea solution from a recovery section of a urea plant required. The urea solution typically originates from a concentration unit, also known as evaporation unit, where it is concentrated by evaporation of at least some water from it. The evaporation unit is preferably operated with a pressure of less than 1.0 bara, more preferably less than 0.50 bara, usually above 0.02 bara, for the urea solution; and in the invention preferably above 0.20 bara. Avoiding deep vacuum may improve energy efficiency. [0073] The evaporation unit is a heating unit, typically a heat exchanger, e.g. using steam as heating fluid, more preferably a process-process heat exchanger, for instance with indirect heat exchange between a carbamate condensation compartment and the compartment for concentrating the urea solution. The evaporation unit may be referred to as a ‘pre-evaporator’ of the urea melt plant. It is noted that the evaporation unit, in particular as heat exchanger, may be integrated in a unit of the urea plant, e.g. a carbamate condenser. The evaporation unit may also be provided by two or more evaporators in series or in parallel or a combination thereof. Preferably, urea solution is supplied from a recovery section of a urea plant to the evaporation unit, preferably from a low pressure recovery section operating at 2 to 10 bara. The recovery section comprises a decomposer having an inlet and outlet for urea solution and a gas outlet, with the gas outlet usually connected to a carbamate condenser. The recovery section may comprise two or more decomposers in series. [0074] Preferably, the process also involves producing the urea-containing liquid stream, said urea production comprising reacting NH3 and CO2 at high pressure (above 100 bar) to form urea synthesis solution, subjecting the synthesis solution to recovery in one or more recovery sections, more preferably including a low pressure (LP) recovery section operating at e.g. 2 – 10 bara to form a LP urea solution, and subjecting the LP urea solution to evaporation in one or more evaporation units operating at less than 1.0 bar to concentrate the urea solution. [0075] Preferably, the process also involves producing the aqueous nitric acid in a process that comprises reacting NH3 with O2 (e.g. supplied as air) in a burner to form a process gas stream comprising NO and H2O, oxidation of NO to NO2, and reaction of NO2 with H2O in an absorption zone, typically an absorption column, which receives aqueous absorption liquid, and typically also some O2, (e.g. supplied as air) to give aqueous nitric acid. The water fraction of the aqueous nitric acid originates from the water by-product and the aqueous absorption liquid. Usually a large part of the aqueous absorption liquid is included in the aqueous nitric acid, this part is set by the design and operating conditions of the absorber. Preferably, the aqueous nitric acid from the absorber is used without concentration (water removal) in the neutralizer, i.e. without concentration between the absorber and the neutralizer. [0076] In some embodiments wherein UAN is produced, the amount of water in the UAN is less than total of the amount of water in the urea-containing liquid stream used for making the UAN, the amount of water formed as by-product in the nitric acid formation, and the amount of water (if any) contained in the NH3 and O2 (e.g. air) feed of the nitric acid formation. In these embodiments, the UAN plant (comprising the NA plant, AN neutralizer, and UAN production unit where AN is combined with the urea-containing liquid stream) has, broadly speaking, a need to dispose of the excess water, e.g. by using it as BFW. In the invention, this is very advantageously done by the second condensate, which has high purity. [0077] Typically, the total amount of water supplied by the total feed streams (urea-containing liquid, NH3 and O2 supplying stream) and water formed as by- product in the nitric acid formation, is more than is permitted in the UAN product (at the desired UAN concentration). In the invention, the disposal (purging) of excess water is very advantageously done by the second condensate, which has high purity. [0078] Hence, the invention also provides a UAN plant which comprises the NA plant with inlets for NH3 and for an O2 containing stream, and which is based on the reaction of NH3 with O2 to form nitric acid; the AN neutralizer reactor according to the invention with the first and second condenser, which AN neutralizer reactor receives nitric acid and NH3 and forms AN, and the UAN production unit receiving the AN and a urea-containing stream and forming UAN. The invention also pertains to a UAN production process carried out in this UAN plant, the process involving producing AN according to the inventive process. In an embodiment, this UAN plant when operated purges excess water, as a stream separately from the UAN product. Herein, the excess is due to the stoichiometry, the UAN specification, and the water content of the urea-containing stream that is available. The second condensate may constitute at least a part of the excess water purge. The UAN production unit for instance has an inlet for the urea-containing liquid stream that is in liquid flow connection with an outlet of a urea synthesis reaction where NH3 and CO2 are reacted to urea and water. [0079] In such embodiments, not all of the total first and second condensate, and not all of the H2O in the first vapor, can be incorporated in the UAN, giving a need to dispose of some of the condensate in other ways. As noted, the condensate will contain some dissolved AN limiting its possible uses in a fertilizer plant when it can not end up in UAN and removing of the AN by polishing or suitable treatment is relatively costly. For a given amount (kg) of condensate containing dissolved AN, the treatment for AN removal to specified lower dissolved AN level is qualitatively more costly with a higher initial dissolved AN level. [0080] The inventive ammonium nitrate production unit comprises a reactor, a first condenser, and a second condenser. The reactor comprises a reaction zone having an inlet for nitric acid and an inlet for NH3, and a separation zone for gas/liquid separation of effluent from the reaction zone with an ammonium nitrate solution outlet, a first vapor outlet, and a recirculation line for ammonium nitrate solution to the reaction zone. The reactor comprises a restriction orifice for the effluent between the reaction zone and the separation zone and the recirculation line comprises a pump. The first condenser is connected to said first vapor outlet and has a first condensate outlet and a second vapor outlet. The second condenser is connected, by an inlet, to the second vapor outlet and has a second condensate outlet. The gas flow line from the second vapor outlet of the first condenser to the inlet of the second condenser preferably does not comprise a (steam) ejector. [0081] In a typical embodiment, the first and second condensate outlets are separate outlets. Typically, the first and the second condensate outlet are connected to different, separate, liquid flow lines (provided by different, separate piping) to different units. Specifically, the first condenser has an outlet for the first condensate connected to a first liquid flow line to an inlet of a first unit and the second condenser has an outlet for the second condensate connected to a first liquid flow line to an inlet of a second unit, wherein the first and second liquid flow line are different from each other and wherein the first and second unit are different from each other. The first and second liquid flow line typically do not combine with each other and are provided by different piping. Furthermore, the first unit is neither the first condenser nor the second condenser and the second unit is neither the first condenser nor the second condenser. The first and second outline may each be connected to further liquid flow lines; i.e. be connected to two or more liquid flow lines. [0082] All preferences and details discussed for the process apply also to the inventive ammonium nitrate production unit. The inventive process is preferably carried out in the inventive ammonium nitrate production unit. [0083] The invention also provides a plant comprising the inventive ammonium nitrate production unit and a nitric acid production unit, wherein the nitric acid production unit comprises preferably a burner section and an absorber. The plant is typically a fertilizer plant or an ammonium nitrate plant. [0084] The process of the invention is preferably carried out in the plant of the invention. The plant is preferably suitable for the inventive process. All preferences and details specified for the units and connections used in process also apply for the plant and vice versa. [0085] The plant preferably comprises the liquid flow lines from the condensate outlets, and the first and second unit as discussed. [0086] The plant further preferably (i) comprises a condensate treatment unit, preferably a polishing unit, having an inlet in liquid connection with the second condensate outlet. The polishing unit is e.g. an ion exchange treatment unit. The treatment unit is e.g. an evaporator, multi effect evaporator, vapor recompression evaporator, reverse osmosis, electro dialysis, or polishing unit; combinations thereof are also possible. [0087] The plant further preferably (ii) comprises a urea ammonium nitrate (UAN) production unit configured for combining a urea-containing liquid stream with the ammonium nitrate solution from the ammonium nitrate production unit to form UAN. Optionally, the plant comprises a urea production section that yields the urea-containing liquid stream; wherein the urea production section comprises a synthesis section for reaction NH3 and CO2 to form urea, a dissociation section to purify the urea solution by carbamate dissociation and gas/liquid separation, and an evaporation unit to concentrate the urea solution by water evaporation. [0088] The plant further preferably (iii) comprises a (first) liquid flow connection (liquid flow line) from the first condensate outlet to one or more units selected from the group consisting of: a scrubber comprised in the ammonium nitrate production unit, the absorber of the nitric acid production unit, and the urea ammonium nitrate production unit; and preferably a second liquid flow connection (liquid flow line) from the second condensate outlet to one or more units other than the units connected to the first liquid flow line. [0089] The plant preferably has the features (i), (ii) and (iii) in combination. [0090] The plant optionally comprises a nitric acid production section comprising a burner for reacting NH3 and O2, and an absorber having an inlet for a gas stream from the burner, a gas outlet, a liquid inlet, and an aqueous nitric acid outlet connected to the AN production unit. [0091] The invention also pertains to a method of modifying an existing ammonium nitrate production unit. The existing ammonium nitrate production unit comprises the reactor and the first condenser; and the method involves adding a second condenser connected to the second vapor outlet, i.e. connected to the first condenser, and the second condenser having a second condensate outlet, thereby preferably obtaining a nitric acid production unit according to the invention. The first and second condensate outlets are separate outlets. All preferences and details for the inventive ammonium nitrate production unit apply also to the modified ammonium nitrate production unit. [0092] The invention also provides a method of modifying an existing plant comprising the existing ammonium nitrate production unit and a nitric acid production unit, wherein the existing nitric acid production unit comprises the reactor and the first condenser, and a first liquid flow line from a condensate outlet of the first condenser to a first unit comprised in the existing plant, wherein the method involves adding said second condenser, and a second liquid flow line from the added second condenser to a second unit in the plant, wherein the first and second unit are different, to give a modified plant. The modified plant is preferably in accordance with the inventive plant. All preferences and details for the inventive plant apply also for the modified plant. [0093] Figure 1 schematically illustrates an example embodiment of a process and plant of the invention. The NH3 feed stream (6) and aqueous nitric acid feed stream (7) are reacted in a neutralizer reactor (R) to give an ammonium nitrate solution (8) and a first vapor stream (1). The first vapor stream is subjected to condensation in a first condenser (C1) to give a first condensate stream (2) and a second vapor stream (3). The second vapor stream separated from the first condensate and is supplied from an outlet of the first condenser to an inlet of the second condenser (C2) and is subjected to condensation in a second condenser (C2) to give the second condensate stream (4), and a third vapor stream (5). The first and the second condensate stream are obtained as separate streams. The second condensate stream (4) is supplied in this example in a first part to a polishing unit (PU) for purification, e.g. using ion exchange resins, to give a purified condensate (10) that is used e.g. as boiler feed water. A second part (9) is mixed with the first condensate. The first condensate (2) is used inter alia for scrubbing in the reactor (R). [0094] Figure 2 schematically illustrates an example embodiment of the reactor used in the invention. [0095] The neutralizer reactor (R) comprises a reaction zone (201) and a separation zone (202). Ammonia (6) and nitric acid (7) are reacted in the reaction zone (201) at a first pressure to give a first effluent (203). The first effluent is expanded, preferably through a restriction orifice (204), and subjected to gas/liquid separation at a second pressure in the separation zone, to give the first vapor stream (1) and AN solution (8). The first vapor is scrubbed in a scrubbing zone (205), e.g. a zone comprised in the same vessel as the separation zone (202), preferably using a part of the first condensate (2) to give a scrubbed gas stream (1a) that can be sent to the first condenser (C1). A first part of the AN solution (8) is recirculated to the reaction zone by recirculation line (206) which comprises a pump (207) and a second part is purged as a product AN stream (8a). Scrub liquid (208) from the scrubbing zone (205) is supplied to the separation zone (202). [0096] Figure 3A schematically illustrates an example UAN production unit used in embodiments of the process and plant of the invention. An urea ammonium nitrate liquid stream (303), e.g. UAN liquid fertilizer, is prepared by combining, in a mixing unit (301), the ammonium nitrate solution (8) in part or entirely with a urea-containing liquid stream (302) to form the urea ammonium nitrate liquid stream (303). Preferably, the ammonium nitrate solution (8) is not concentrated by water removal, in particular by water evaporation, between the neutralizer reactor and the UAN production unit. [0097] Figure 3B schematically illustrates an example NA production unit used in embodiments of the process and plant. The NA production unit (304) receives NH3 feed (305) and stream (306) that comprises O2 to form an aqueous nitric acid stream (307). [0098] The abbreviation ‘bara’ indicates absolute pressure in bar. The term ‘typical’ indicates features that are commonly used in embodiments of the invention but that are not essential.

Example The invention will now be further illustrated by the following non-limiting example(s). These examples do not limit the invention and do not limit the claims. Example 1 In a calculated simulation of a forced circulation neutralizer, for production of 1 ton (1000 kg) of AN, 212 kg gaseous NH3 (12.45 kmol) was reacted with a mixture of 787 kg nitric acid (12.49 kmol) and 525 kg water at about 1.5 bara, i.e. excess nitric acid. The 525 kg water is provided by 225 kg by-product from NA production (and 260 kg condensate used as absorption liquid in the NA absorption column, and 40 kg additional H2O e.g. from feed streams of the NA production). The reactor contained an inlet zone, a mixing zone, a shell-and-tube chamber with liquid in the tubes and gaseous NH3 in the shell admitted to the liquid through perforations in the tube, and a reaction zone comprising a static mixer. The resulting effluent contained negligible unreacted ammonia, and was passed to a restriction orifice and flashed in a separation zone at about 0.35 bara to give, after flashing and removal of vapor by gas/liquid separation, an ammonium nitrate solution (1.12 ton, 89 wt.% AN) and a vapor stream consisting, after scrubbing, of about 470 kg H2O, and about 30 to 40 ppm by weight entrained AN and nitric acid in total. The first vapor stream was supplied to a first condenser operating with cooling water (about 30ºC to 50ºC at the outlet) and about 0.35 bara; with 2 kg air added (for 1 ton AN to be produced). The resulting 140 kg aqueous condensate (first condensate) contained 40 ppm by weight AN, corresponding to 14 ppmw N due to AN. The non-condensed gas was supplied directly to a second condenser, also operating with cooling water and about 0.35 bara. The 330 kg aqueous condensate from the second condenser (second condensate) contained 20 ppm by weight AN, corresponding to 7 ppmw N. The first and second condenser operated at about 0.35 bar. The AN solution was combined with a 1000 kg of urea solution, consisting 76 wt.% of urea solution, containing 760 kg of urea and 240 kg water to form 2240 kg UAN-32 (45% ammonium nitrate, 35% urea and 20% water by weight). The urea melt was obtained from an evaporation unit, known as pre-evaporator, operating at 0.45 bara and 95ºC to concentrate a urea solution from a low pressure urea recovery section of a urea plant. The 140 kg first condensate was mixed with about 254 kg second condensate and the condensate mixture was used as follows: 65 kg for UAN dilution, 260 kg as absorption liquid in the nitric acid absorption column, thereby essentially being included in the nitric acid feed, and 69 kg for said scrubbing of the vapor stream, thereby essentially being included in the AN solution. No additional water was added to the UAN. The remaining 76 kg second condensate, which could not be included in the UAN product without exceeding the specified water content of UAN-32, contained 20 ppm by weight AN and was used entirely as BFW after treatment (polishing). Hence, advantageously this non-mixed part of the second condensate was clean enough to be used as boiler feedwater (BFW) after polishing. In a reference plant using a single condenser, the effect would the same as mixing the first and second condensate, using 294 kg of the mixture in the same way as the first condensate, and sending 76 kg of the mixture to polishing. As the condensate sent to polishing in the reference plant has a higher N level than the condensate sent to polishing in the inventive plant, the inventive plant has an advantage in terms of the polishing treatment. In the reference plant, the condensate from the single condenser has a lower N level, but this provides no advantages for producing UAN. The scrubbing of the vapor is for the removal of entrained AN and vapors from nitric acid, present along with water in the vapor and is not negatively affected by the N content of the scrub liquid. Optionally, some first condensate is used, without mixing with second condensate, for diluting UAN. Optionally, some second condensate is used, without mixing with first condensate, in the nitric acid absorption column.

Claims

Claims 1. A process for the production of ammonium nitrate comprising: - reacting NH3 and nitric acid in a neutralizer reactor (R) to give an ammonium nitrate solution and a first vapor stream (1); - subjecting said first vapor stream to condensation in a first condenser (C1) to give a first condensate stream (2) and a second vapor stream (3); and - subjecting the second vapor stream to condensation in a second condenser (C2) to give a second condensate stream (4); wherein the first and the second condensate stream are obtained as separate streams.

2. The process according to claim 1, wherein the first and second condensate are separately disposed of.

3. The process according to claim 1 or 2, wherein the reactor comprises a reaction zone (201) and a separation zone (202), wherein the ammonia and nitric acid are reacted in the reaction zone at a first pressure to give a first effluent (203) and the first effluent is expanded, preferably through a restriction orifice (204) , and subjected to gas/liquid separation at a second pressure in the separation zone, wherein the first pressure is higher than the second pressure; preferably wherein the separation zone is operated at a pressure of less than 0.8 bara.

4. The process according to any of the preceding claims, wherein the first condensate is used at least in part, preferably at least 50 wt.%, for one or more uses selected from the group of use as scrub liquid, use in an absorption column, use as diluent of a liquid stream containing at least 10 wt.% urea, and use as diluent of a liquid stream containing at least 10 wt.% ammonium nitrate.

5. The process according to any of the preceding claims, wherein the second condensate stream is used at least in part as boiler feed water, optionally after a treatment.

6. The process according to any of the preceding claims, wherein the weight ratio between the first and second condensate is in the range of from 1:5 to 5:1.

7. The process according to any of the preceding claims, wherein the first condenser and/or the second condenser use cooling water.

8. The process according to any of the preceding claims, comprising subjecting the first vapor stream to scrubbing with a scrub liquid in a scrubbing zone (205) upstream of said condensation in the first condenser; wherein preferably said first condensate is in part or entirely used as a part or all of said scrub liquid.

9. The process according to any of the preceding claims, for the preparation of an urea ammonium nitrate liquid stream (303), comprising combining the ammonium nitrate solution (8) in part or entirely with a urea-containing liquid stream (302) to form the urea ammonium nitrate liquid stream (303).

10. The process according to claim 9, wherein the urea ammonium nitrate comprises at least 30 wt.% AN, at least 20 wt.% urea, and at least 10 wt.% water and preferably less than 50 wt.% water.

11. The process according to claim 9 or 10, wherein preparation of an urea ammonium nitrate liquid stream is conduced in a UAN plant which comprises: - a NA plant (304) with an inlet (305) for NH3 and an inlet (306) for an O2 containing stream and an outlet (306) for the aqueous nitric acid, and based on the reaction of NH3 with O2 to form nitric acid; - the neutralizer reactor (R) having an inlet for the aqueous nitric acid (307, 7), an inlet (6) for NH3, and an outlet for AN solution (8) - a UAN production unit (301) receiving the AN solution (8) and a urea- containing stream (302) to form UAN product, wherein the UAN plant purges excess water, as a stream separately from the UAN product.

12. The process according any of the preceding claims, wherein a part or all of the second condensate stream is treated in a polishing unit and/or an ion exchange treatment unit, e.g. by contact with an ion exchange resin, wherein the polishing unit receives more second condensate than first condensate (kg/hr), and preferably the polishing unit receives no first condensate.

13. The process according any of the preceding claims, wherein the second vapor stream (3) is supplied directly to the second condenser (C2).

14. An ammonium nitrate production unit comprising: - a reactor (R) comprising a reaction zone (201) having an inlet for nitric acid and an inlet for NH3, and a separation zone (202) for gas/liquid separation of effluent from the reaction zone with an ammonium nitrate solution outlet, a first vapor outlet (1) , and a recirculation line (206) for ammonium nitrate solution to the reaction zone, wherein the reactor comprises a restriction orifice (204) for the effluent between the reaction zone and the separation zone and the recirculation line comprises a pump; - a first condenser (C1) connected to said first vapor outlet and having a first condensate outlet (2) and a second vapor outlet (2); and - a second condenser (C2) connected to said second vapor outlet of the first condenser and having a second condensate outlet (4), wherein said first condensate and said second condensate outlet are separate outlets.

15. The ammonium nitrate production unit of claim 14, wherein the first and the second condensate outlet are connected to different liquid flow lines to different units.

16. A fertilizer plant comprising the ammonium nitrate production unit according to claim 14 or 15, a nitric acid production unit comprising a burner section and an absorber; and – a polishing unit having an inlet in liquid connection with the second condensate outlet; – a urea ammonium nitrate (UAN) production unit configured for combining a urea-containing liquid stream with ammonium nitrate solution from the ammonium nitrate production unit to form UAN; – a liquid flow connection from the first condensate outlet to one or more units selected from the group consisting of: a scrubber comprised in the ammonium nitrate production unit, the absorber of the nitric acid production unit, and the urea ammonium nitrate production unit.

17. A method of modifying an existing ammonium nitrate production unit, the existing ammonium nitrate production unit comprising: - a reactor (R) comprising a reaction zone (201) having an inlet for nitric acid and an inlet for NH3, and a separation zone (202) for gas/liquid separation of effluent from the reaction zone with an ammonium nitrate solution outlet, a first vapor outlet (1), and a recirculation line (206) for ammonium nitrate solution to the reaction zone, wherein the reactor comprises a restriction orifice (204) for the effluent between the reaction zone and the separation zone and the recirculation line comprises a pump; - a first condenser (C1) connected to said first vapor outlet and having a first condensate outlet (2) and a second vapor outlet (2); wherein the method involves: - adding a second condenser (C2) connected to said second vapor outlet of the first condenser and having a second condensate outlet (4), wherein said first and second condensate outlets are separate outlets; wherein the modified unit is preferably according to claim 14 or 15.