Method of ammonia synthesis and an installation used for the purpose

FIELD: chemical industry; production of ammonia.

SUBSTANCE: the invention is pertaining to the process of synthesis of ammonia, in particular to improvement of the process of cleanout synthesis of the gas added into the catalytic reactor for substitution of the reacted synthesis gas. The method of synthesis of ammonia provides for compression of the synthesis gas containing hydrogen and nitrogen in a many-stage centrifugal compressor. On the first stage of this compressor the synthesis gas is compressed up to the pressure making from approximately 800 up to 900 pounds per a square inch - (56-63)·105 Pa, withdraw from this stage and cool, and also dehydrate by a contact to a liquid ammonia in a dehydrator. Then the cooled and dehydrated synthesis gas is fed back in the compressor and bring it on the second stage. The installation for realization of this process contains a centrifugal compressor supplied with the synthesis gas outlet, that connects the synthesis gas discharge outlet from the first stage of the compressor with the synthesis gas inlet in the dehydrator, and also an intermediate inlet of the synthesis gas connecting by a hydraulic link the inlet of the second stage of the compressor with the synthesis gas discharge (outlet) from the dehydrator. Due to the intermediate cooling and a dehydration the compressor rate is lowered, and due to favorable effect of the dehydrator on the last two stages of the compressor a significant saving of the consumed power is also achieved. The additional saving of the consumed power is possible due to decreased need of chill in the closed contour of the synthesis process.

EFFECT: the invention ensures a significant saving of the consumed power for the synthesis process in the installation.

13 cl, 1 dwg

 

Background of the present invention

The present invention relates to a method and installation for producing the product in a catalytic reaction under pressure synthesis gas. For example, one variant of the present invention is concerned with the obtaining of ammonia used for this catalytic reaction under pressure synthesis gas containing hydrogen and nitrogen. In particular, the present invention relates to an improved method for cleaning an incremental synthesis gas, namely the synthesis gas that is added in a catalytic reactor to replace the reacted synthesis gas.

Related technologies

In U.S. patent 3350170 on October 31, 1967 (owned J.A.Finneran et al) disclosed a process of cyclic reactions of synthesis at high pressure and, in particular, it relates to improvement of the compression method when such processes fresh and recycled synthesis gas. This patent is well illustrated by the type of synthesis process associated with the present invention. As shown in figure 1 of U.S. patent 3350170, fresh synthesis gas 10 is introduced into a centrifugal compressor together with the circulating gas 42 from the Converter 38, in which hydrogen and nitrogen catalytically converted to ammonia. Therefore, the working gas discharged from the Converter 38, and contains ammonia (as finished product)and unreacted hydrogen and the OST. Specified working gas is re-injected into the compressor through the pipeline 24. Thus, compressed escaping gas 26 contains a mixture of the circulating gas and introduced through the pipeline 10 fresh (incremental) gas. Ammonia in the quality of the finished product is separated in the separator 31, and the compressed and depleted in ammonia synthesis gas by pipeline 33,34 and 35 is supplied to the Converter 38. The pipe 46 is used to select from closed circuit synthesis flushing gas in order to prevent this circuit impurities in pipelines 42,24,26 and 33.

Standard processes for the synthesis of ammonia destruction of H2On extension of the synthesis gas is performed by mixing the gas containing approximately 160×10-6water circulating gas, which occurs at the input disk of the circulating compressor. Coming out of the compressor the gas is then cooled and mixed with N2Oh, absorbed condensing NH3. In this separator NH3and absorbed N2About is separated from the gas. In the Converter serves the gas from the separator, and the separated gas is substantially not contain water or it contains at least only a very small residual amount. The separated gas may contain, for example, approximately 1.9% of NH3. This system has several disadvantages. Because of the dilution e is fluent Converter incremental gas which reduces the concentration of NH3and the condensing temperature, a higher cooling capacity. This transfers the load from the freezers with higher temperatures for freezers with lower temperatures, which on 1 ton cold it needs more power. In addition, in the reverse cycle finished NH3is compressed, the consumption power of the compressor is increased. As shown in the U.S. patent 1815243, thanks to the inclusion in this system dehydrator can better implement requirements for energy reduction.

In 1989, at the meeting of the American Institute of chemical technology (American Institute of Chemical Engineers) was presented H.Bendix, L.Lenz (VEB Agrochemie Piesteritz, the developer of the German Democratic Republic (East Germany). In this work, entitled "Results and experience of reconstruction of large ammonia plants, with one pipeline" {Results and. Experience on Revamping of Large-Scale Ammonia Single-Line Plants), described further introduction to synthesis gas, which divert from the third compression stage of the synthesis gas, liquid ammonia using a Venturi. The declared goal is drying synthesis gas.

Work M.Badano, F.Zardi was presented at the meeting of the Nitrogen'99, held February 28-March 2, 1999 in Caracas (Venezuela) and sponsored by British Sulphur Publishing. In the work entitled "the Experiences of a group Casale reconstruction to the of ElexV ammonia, methanol and urea" (Casale Group Experience in Revamping Ammonia, Methanol and Urea Complexes) revealed rinsing liquid ammonia ammonia synthesis gas, which is carried out between the second and third stages of the syngas compressor.

Another method of the prior technology described in U.S. patent 1830167 and patent Canada 257043. This method involves washing the combined stream extension and circulating gas liquid NH3, it is performed before the heating of this thread and before being sent to the Converter. Usually flushing the reverse flow was not necessary, because this thread does not contain any impurities. The disadvantage of these schemes patents is that they impurities distributed throughout the gas stream. Therefore, since these impurities are diluted due to their dispersion throughout the gas flow, the impact on the complete removal of these impurities is more difficult. For processing such combined stream to install a gas washing must have a lot of large dimensions and can be more expensive than would be required for flushing of the stream of net incremental gas because of the volume of the gas flow in 4-5 times the volume of the net flow of additional gas. Therefore, in the schemes of U.S. patent 1830167 and patent Canada 257043 load washing increased due to the fact that the reverse and add CNY streams unite before washing.

Another way (from the previous technology) included the use of molecular sieves to remove water from the additional gas with absorption. The idea dehydrogenation extension allows gas to fill the cooling system coming out of the Converter flow having the highest content of NH3. This saves considerable cooling capacity and can contribute to a significant growth of the plant performance, limited by the dimensions of the refrigeration compressor. Is to save power, since the dew point has a higher value, which leads to some condensation with cooling water, and to transfer the load from the freezers, low temperatures for freezers with high temperature, which on 1 ton of refrigeration requires less power. Removal of N2About using molecular sieves gives the possibility not to apply the freezer flushing gas, which uses the deep cooling of NH3.

Then incremental gas that does not contain water (and NH3), is mixed with the circulating gas, is subjected to compression in the working cycle, and fed into the Converter. This system has advantages over competing technologies, which consist in the fact that the content of NH3in the original reaction mixture of the Converter is low, it is approximately 1.4%. Oncoproteomics this advantage are other factors, such as the heat required for regeneration of molecular sieves, the complexity of operation (because of absorption and desorption of water from the molecular sieves during cyclic operation required multiple switching valves), higher cost of maintenance and high capital cost of reservoirs of molecular sieves, heat exchangers, filters, piping and valves. Compared with the standard calculation of the secondary flash energy savings are estimated at approximately 0,53 MM BTU/ST (where ST means a small ton (=907,2 kg) or 2000 pounds).

Another prior idea of this technology is shown in U.S. patent 3349569. This patent discloses the installation of scrubber NH3at the outlet of the syngas compressor in order to use liquid NH3for absorption of water from incremental synthesis gas. This allows mixing of incremental gas from the working gas and its direct filing in the ammonia Converter. Then effluent Converter is fed directly to the cooling/freezing, the type of which was described above in connection with the use of molecular sieves. Significant cooling effect is realized due to the heat necessary for the evaporation of NH3that comes from incremental cooling gas. Then this extension gas, to a large degree the Yeni contains no water and contains approximately 4.9% of NH 3mixed with the circulating gas, as described above in connection with the use of molecular sieves.

This system has several disadvantages. Redundant cooling, additional gas due to excessive evaporation of NH3caused by low pressure, leads to overheating of the scrubber and to the fact that the outlet temperature of the compressor (-27°F) below the minimum temperature for standard construction materials (-20°F). For such a scrubber requires more expensive low-temperature structural materials, and will be a recalculation of the compressor (if possible). Recalculation of the compressor in some cases can be achieved if the original materials of its construction suitable for more severe operating conditions. Or you may need to upgrade the low-pressure compressor, and it is expensive. Another drawback of this method is that in the circulating gas fed to the desulfurization in the preprocessor setup will contain NH3that will reduce the efficiency of the installation. In the area of reforming the reverse of this scheme NH3should decompose to H2and N2. From the point of view of moisture removal suction scrubber is also a hindrance, since the equilibrium water content, although it is low, but its value will be 2-3 times higher than in the synthesis loop is agitation of the present invention. However, the main disadvantage of the system on the previous technology is the result of her work at low pressure, which leads to additional introduction of a significant number of NH3in the gas supplied to the Converter, which contains approximately 2.6% of NH3. This reduces the energy savings compared to the standard calculation of the secondary flash to about 0.45 MM BTU/ST (ST=907,2 kg or 2000 pounds). (See, for example, U.S. patent 1815243).

In the embodiment, the suction scrubber (as described in U.S. patent 3349569) for condensing a certain amount of NH3, evaporated primarily on the outlet of the compressor scrubber, you can use additional cooling and freezing, which occurs between stages of the compressor. The resulting liquefied NH3is used for further purification of synthesis gas by selective absorption of some of the remaining impurities. However, the need of such kind of system in cold weather should be prohibitive.

Another system according to the previous technology puts the scrubber in the same conditions of pressure in the closed circuit synthesis, namely approximately 1900 pounds per square inch. This gives one the advantage of minimizing the content of NH3in the upper chase scrubber (2.7%) and in the load Converter (2,1%). However, this scheme who meet a number of drawbacks. Most important for reconstructing circuit synthesis at 1900-2000 pounds per square inch is a modification of the two-phase compressor. Should add a fourth nozzle (change, which had never produced), and the size of the back wheel should be reduced. For less than a standard high pressure (2500-3000 psi) two-phase compressor already has 4 nozzles, so adding one nozzle in this case is not a problem. The risk associated with the modification of the compressor, is significant, as there may be many problems (vibration, pulsation, oil leakage, failure of bearings and so on). It is also expected that the cost of reconstruction of this system will be very high due to the modification of the compressor, the need for additional introduction of two or more heat exchangers (coolers inlet scrubber) and need to pump for NH3. No reduction in speed of the compressor is not happening because there is no any evaporation of NH3and the subsequent freezing of incremental gas (first or second stages). It is expected that energy savings for systems serving scrubber 36°F (excluding problems of freezing) will be approximately 0,44 MM BTU/ST (ST=907,2 kg or 2000 pounds).

A summary of izobreteny the

In General, the present invention provides a process and system for producing ammonia from the compressed synthesis gas containing a mixture of hydrogen and nitrogen, to remove water from the synthesis gas with the intermediate stage of the compressor syngas use a dehydrator.

In a preferred embodiment, the present invention provides the use of substantially anhydrous liquid NH3for washing, and subsequent cooling in the dehydrator reset the synthesis gas between the first and second stages of the multistage compressor. This affects cleaning incremental gas, and reduces the power required for compression.

In addition, the present invention introduces a scheme for synthesis of an advanced stage of cleaning so that increased the effectiveness of the stages of the process. Flushing incremental synthesis gas liquid NH3in order to remove impurities (mainly water) allows mixing the synthesis gas from the working gas and its immediate supply to the Converter. In particular, cleaning of the specified incremental gas allows it to mix with the gas depleted in NH3to this mixture is served on the third or on the back of the stage compressor and then to the Converter. In a revolving drum NH3in the form of finished product is not subjected to compression, and it saves energy is Yu. Effluent Converter can be sent directly to the cooling/freezing for condensation NH3at this prevents dilution of the added gas and reduces the need for cooling. Thus, compared with the systems according to the previous technology, the power consumption is reduced. NH3in the form of the finished product is removed before carrying out the reverse of compression.

Compared to previous technological schemes of the present invention reduces power requirements, used for compression and the energy consumed in the process, makes it possible to increase the capacity of the plant, to reduce the speed of the compressor, to conduct a stage of purification (removal of water and other saturated with oxygen impurities) at a pressure high enough to achieve significant cleaning without the need for further stages of the technological process, as well as to exclude using excessively expensive intermediate stage of compression required for some prior technological schemes.

In particular, in accordance with the present invention provides an improved process of obtaining ammonia. This process involves the compression of the synthesis gas containing hydrogen and nitrogen, in a multistage compressor (each compressor has an inlet and connected with it the issue), to Tachibana subjected to compression of synthesis gas into ammonium reactor with a suitable catalyst under conditions to facilitate the interaction between parts (smaller than the whole amount) of hydrogen and nitrogen from the synthesis gas with obtaining ammonia, separating the finished of ammonia coming from the ammonia Converter flow effluent reactor, and return in a multistage compressor part of the flow effluent reactor containing unreacted hydrogen and nitrogen. This process involves the removal of the compressor flow incremental synthesis gas, cooling and dehydration of the exhaust flow synthesis gas (and stage dewatering takes place when contacting the specified flow exhaust synthesis gas with liquid ammonia), as well as the return flow of the cooled and dewatered synthesis gas in the compressor. The improvement is that the exhaust flow synthesis gas discharged through the output of the first stage of the compressor and returned to the compressor from entering its second stage.

Another aspect of the present invention is provided to the entire flow of the synthesis gas taken out from the output of the first stage of the compressor, cooled and dehydrated.

In the private aspect of the present invention a multi-stage compressor is a three-stage compressor, and synthesis gas derived from the first stage at a pressure of from about 800 to 900 pounds per square inch(56-63)·105PA), from the second stage at a pressure of from AP is sustained fashion 1800 to 1900 pounds per square inch(126-133)· 105PA), and from the third stage at a pressure of from about 2000 to 2100 pounds per square inch(140-147)·105PA).

In one aspect of the present invention, the exhaust flow synthesis gas is cooled to a temperature of from about 20.5 and to -26,1°C (-5 to -15° (F) before to make his return to the compressor.

In another aspect of the present invention the flow of the synthesis gas from the dehydrator return to the compressor without heating.

Another aspect of the present invention is provided to the water content in the exhaust stream of the synthesis gas prior to its return to the compressor is decreased to the value component is less than 0.1 parts by volume per million.

The present invention also includes cooling the exhaust from the syngas compressor for condensing the contained ammonia and removal from the synthesis gas and the condensed ammonia before it is input in the ammonia Converter.

Typically, the synthesis gas contains hydrogen and nitrogen at their molar ratio of approximately 3:1.

Another aspect of the present invention provides improved devices for carrying out the process of producing ammonia by compressing the synthesis gas containing hydrogen and nitrogen. The process is carried out in a multistage compressor comprising at least first and verwustung, and each stage compressor has a combined suction and discharge. The process includes contacting compressed in the ammonia reactor synthesis gas with a suitable catalyst under conditions that promote interaction of the parts (less than the whole amount) of hydrogen and nitrogen from the synthesis gas with obtaining ammonia, as well as a selection of ready-made ammonia from a stream effluent reactor discharged from the ammonia Converter. This process also includes processing in a multi-stage compressor part of the flow effluent reactor containing unreacted hydrogen and nitrogen and contacting incremental synthesis gas with liquid ammonia in the dehydrator with the intake and production of synthesis gas, and the intake and discharge of liquid ammonia. The improvement of the installation lies in the fact that the compressor is equipped with (a) the production of synthesis gas, connecting the hydraulic connection of the output of the first stage and the inlet of the synthesis gas in the dehydrator, and (b) an intermediate inlet of the synthesis gas, which connects the hydraulic connection inlet of the second stage with the release of the synthesis gas from the dehydrator, which defines the path of movement of the stream of synthesis gas from the outlet of the first stage through the dehydrator, and therefrom to the inlet of the second stage.

The inlet and outlet for synthesis gas and the liquid ammonia is preferably located so that dehydratation liquid ammonia and synthesis gas are moved in a counter.

The apparatus aspect of the present invention ensures that the specified device also includes a heat exchanger for heating the synthesis gas, and vapor-liquid separator for separating water from it, and the specified heat exchanger and the vapor-liquid separator located in the path of movement of the synthesis gas between the first stage compressor and the inlet of the synthesis gas in the dehydrator.

Brief description of drawing

On a single drawing shows a flow chart illustrating one variant of the present invention.

Detailed description of the present invention

In the production of ammonia in a closed loop incremental gas preprocessor installation is primarily a mixture of hydrogen (H2) and nitrogen (N2when a molar ratio of approximately 3:1. This gas also contains smaller amounts of inert substances such as methane (CH4) and argon (Ar), and other unwanted impurities, type monoxide (CO), carbon dioxide (CO2)and water vapor (H2About). In the circuit synthesis of ammonia, it is imperative that oxygen-containing compounds (including water) were removed before the gas is introduced into the ammonia Converter, since these compounds poison the catalyst synthesis. Such substances tend to oxidize the catalyst, providing the item is and this to it's harmful effects.

According to the present invention for the absorption of additional gas water and minor amounts of other impurities in the dehydrator uses liquid NH3the process carried out at an intermediate stage of the compressor synthesis gas. This allows mixing of incremental gas from the working gas and its direct filing in the ammonia Converter, and then effluent Converter is fed directly to the cooling/freezing. In accordance with the present invention a gas selected from the intermediate stage of the compressor, is technologically processed in the dehydrator. For most applications (for example, the synthesis loop at 2000 psi (140·105PA) with two stages of compression incremental gas scrubber performs the processing gas at the inlet to the second stage of the syngas compressor and it works under medium pressure. In such designs the dehydrator must operate at a pressure of approximately 800-900 pounds per square inch(56-63)·105PA). In less than the standard regimen of synthesis for higher pressure (2500-3000 psi) ((175-210)·105PA), it is better to dehydrator was placed between the second and third stages of the compressor and worked at a pressure of approximately 1200-1400 pounds per square inch(84-98· 105PA).

As for the outline of the synthesis of NH3there is an optimum operating pressure (depending on several factors of approximately 1500-2500 psig) ((105-175)·105PA), and also for removal of water, including contact with liquid NH3there is an optimum pressure. It was found that the standard outlines the synthesis of operating at a pressure in the 1900-2000 pounds per square inch(133-140)·105PA), the optimal pressure for removal of water should be 800-900 pounds per square inch(56-63)·105PA), which is the working point between the two housings of the compressor. It was found that this range of pressures is the best due to the following factors:

Energy efficiency improvements (approximately 0.55 MM BTU/ST for installations with energy consumption in 32 British thermal unit/ST (ST=907,2 kg or 2000 pounds);

Growth reducing the speed of the compressor (approximately 3% for syngas compressor and approximately 4-5% for refrigeration compressor);

The change (increase) throughput (3-4%, if the turbine compressor syngas);

The reduction of complexity (no refund NH3in the preprocessor);

Reduction of capital investment (no need for technicians is lnyh expensive construction materials, there is no need of modification of the syngas compressor, there is no need for additional exchangers type scrubber inlet coolers for nodes of high pressure, does not require any additional mezhdustupenchatogo cooling).

The following discussion applies to the standard outline of the synthesis of NH3in which use three-stage syngas compressor (two additional stages and one reverse). In accordance with the present invention for such a synthesis loop dehydrator is located between the first two stages of the compressor. It was found that some of the above reasons this location is optimal (optimal working pressure).

Refer to the single drawing. It schematically shows the use of the dehydrator in the circuit synthesis of ammonia at a nominal pressure of 2000 pounds per square inch (104·105PA). Thread 1 incremental synthesis gas derived from known previous stages of the process (type of reforming with steam supplied hydrocarbon with subsequent conversion, removing CO2and mechanisatie), enters the dehydrator under pressure, constituting approximately 300-400 pounds per square inch(21-28)·105PA). Depending on suction design, there may be some changes to this pressure, but the fact is not relevant to the present invention. Gas mainly contains reagents are hydrogen (H2) and nitrogen (N2when a molar ratio of approximately 3:1. Other components such as methane (CH4) and argon (Ar) are usually present in small quantity (a total of approximately 1%). There are also oxygen-containing impurities of the type of carbon monoxide (CO), carbon dioxide (CO2)and water vapor (H2About). Using above methanator oxides of carbon have been virtually removed from the gas stream 1, but the water still needs to be removed, this must be done before the synthesis gas is introduced in a closed loop and before submitting them to the ammonia Converter 60.

At the first stage centrifugal compressor synthesis gas 50 gas stream 1 is subjected to compression to a pressure of about 800-900 pounds per square inch(56-63)·105PA). Thread 2, the exhaust from the first stage is divided, with part of it, the thread 3 is sent to the preprocessor setup for use as a gas hydrodesulphurization (what is known in this technology). The entire gas stream 2 passes in the direction of flow 4 into the heat exchanger 52 (which may include a few different sites)where it is cooled to the temperature component of the estimated 4.4° (40°F). The main part of water present the outdoor is:, separated in the drum 53 and leaves the system as stream 7.

Stream 6 containing approximately 160×10-6water represents the flow of steam leaving the drum 53 and coming in dehydrator 54, where it is washed in a largely anhydrous NH3contained in stream 26. The dehydrator 54 may be any of the known gas-liquid contacting device in which in order diffusion transfer occurs close contact of the gas and liquid phases with each other. Water from a specified gas phase is absorbed by the ammonia liquid phase, the process takes place in the dehydrator 54. The latter usually can be a column that uses the cap plate / tube sheet plates, seals, and any suitable and known means for the implementation of close contact vapor-liquid. In this case, to ensure an adequate contact of the vapor-liquid preferred columns with bubble cap plates, since each plate is supported by a certain concentration of the liquid. To remove most impurities and, basically, the entire amount of water, the gas in contact with liquid NH3in counterflow. In the column dehydrator 54 coming from the top gas is in contact with the liquid moving down. When absorption as it moves up the column, the amount absorbed component in the gas phase at anisette, and its quantity in the liquid phase increases when moving down.

The final water content in the exiting gas should be such that it was in equilibrium with the liquid leaving the stage (almost pure NH3with a very small amount of water). The water content of the exiting gas should be less than 10×10-6so that the water content of the gas supplied to the Converter, after dilution of the circulating gas was not more than (1-2)×10-6. In actual practice it is expected that the water content should be a lot lower and it actually is not detected. According to calculations, the concentration of water in the pair after the first theoretical plates is reduced to a value which is less than 0,1×10-6and after the second theoretical plates is essentially to zero. Although it is expected that the water content should be as low efficiency dehydrator actually should not be changed, even if the water content in the upper chase is slightly higher (approximately up to 5×10-6). The experimental data set forth in U.S. patent 3349569 and related balance of water/ammonia, show that the water content of the thread 8 of the upper shoulder strap, leaving dehydrator 54 must be sufficiently low (after adjusting for the concentration at the inlet and operating pressure up to 1×10-6). the button to get the heat which is necessary for the evaporation of NH3saturating a gas, there is a significant cooling effect. Last dehydrogenation top zipper scrubber comes out of it in the form of a stream of 8 at the temperature of approximately -10°F, the content in this thread NH3is approximately 3.5%. At the bottom of the column containing the dehydrator 54, is supported by some concentration of fluid and clean fluid comes out in the form of stream 27.

At the second stage 56 of the compressor facing upper shoulder strap 8 is compressed to a pressure of about 1900 pounds per square inch (133·105PA). Exhaust from the second stage 56 stream 9 is then mixed with the circulating gas stream 31 with the formation of the thread 10. The last third stage 57 of the compressor is further compressed to a pressure of approximately 2030-2080 pounds per square inch, (142,1-145,6)·105PA). This third stage is sometimes referred to as "working the wheel". The exact value of the discharge pressure will depend on the pressure drop in a closed circuit synthesis, which is a function of the specific circuit performance, the conversion of NH3and other factors. The combined stream extension and back strip 11 extends from the third stage of the compressor 57 and is pre-heated in heat exchanger 59 to which zagruzki/effluent. Then preheated gas containing approximately 2.3% of NH3in the form of stream 12 is directed to the ammonia Converter 60. Here over the catalyst is a reaction for the synthesis of ammonia, its schema is shown by the following equation:

3H2+N2=2NH3

Coming out of the Converter gas stream 12 containing from about 12 to 20% of NH3(usually from about 15 to 17% of NH3), then passes through the heat exchanger 61 with regenerative heating surface. This heat exchanger 61, the gas exits as stream 14, then it is cooled in the heat exchanger 59 exits as stream 15. Further cooling of the gas stream 15 is in the heat exchanger 62 under the action of the cooling water. Escaping gas leaves the heat exchanger 62 water-cooled in a stream 18, which, as shown, is divided into stream 16 and 17, received respectively in the heat exchangers 64 and 66. Additional cooling with a suitable refrigerant (type NH3) is carried out in a heat exchanger 64, which may include multiple nodes, using successively higher level of cooling. In the heat exchanger 66 is regeneration cold. Facing the threads 19 and 20, respectively, are then combined in stream 21 heading into the separator finished product 67. In this separator ready NH3about is really in the form of a liquid phase (stream 23). The gaseous phase (stream 22) is returned to the heat exchanger 66 to the above-mentioned regeneration cold. Re-heated gas (stream 30) share, and the smaller stream 32 is cleaned by removing inert impurities, in order to obtain fuel. Most of the flow is returned to the compressor in the reverse flow 31. It should be noted that there is no need to illustrate the device of the freezer cleaned gas path 32 and separator.

The fluid flow 23 from the separator of the finished product 67 share, and part of it goes in the dehydrator as stream 25. The pressure of stream 25 is reduced in a direction transverse to the orifice 55, and the thread 26 coming out of the throttle 55 is directed into the top of the dehydrator. The remainder of pressurised fluid, in the form of a stream 24 is directed from the separator of the finished product 67 to release the drum 69. This tank operates at a reduced pressure of about 250-270 pounds per square inch. At the very bottom of the dehydrator liquid NH3(stream 27), which contains water and minor amounts of other impurities, is separated from the incremental synthesis gas, selected through a level controller 71, and an intermediate stream 33 is sent to the drum 69. Instantly eye-catching gas (stream 28) out of the upper part of the trigger drum 69 in the form of fuel, and the liquid is NH 3as a finished product (stream 29) out of the lower part of the trigger drum 69.

Refer to the drawing. The temperature of the gas coming out of the dehydrator 54 in the form of the upper thread 8, and the concentration of NH3will slightly vary as a function of the temperature of the injected gas (stream 6), the temperature of liquid NH3(the threads 25 and 26), as well as working pressure. It is usually best to minimize the operating temperature (to reduce its flow 8 to about -20°F), as this will reduce the vapor pressure of NH3and his number in the extension Gaza, and ultimately will reduce the concentration of NH3in the gas supplied (stream 12) on the ammonia Converter. The energy minimum in the case that increasing concentrations of NH3parallel to the specified Converter is maximized. In addition, as already discussed, the lower the temperature at the inlet of the compressor reduces the volumetric rate of the incoming flow, power consumption and speed. If the temperature at the outlet of exchanger 52 is relatively high (for example, if the exchanger is not cooling the freezer), it would be reasonable to provide further cooling of the stream 6 to a lower temperature, which constitutes approximately 40°F.

The amount of wash liquid used in the stream 25 going to the top of the dehydrator 54, may also be the somewhat fickle. To prevent evaporation in the dehydrator dry, this number must be at least equal to the amount of evaporated NH3. In practice, the calculated minimum number necessary to add some extra to the specified number was at least 10% of stream 3 exiting the separator 67. If the temperature of the stream 25 is very close to the temperature of the upper part of the dehydrator 54 (for example, -10° (F)the quantity of wash liquid delivered by the flow 25/26, have a minor effect on the heat balance of the dehydrator, and so it should be 10-15% of the stream 23. If the thread 25 is warmer (for example, -2°F), its consumption should be reduced to approximately 10-15% of the thread 23, because large numbers have a tendency to slight heating, and on top of the dehydrator comes a little more NH3. If the thread 25 is colder (for example, -18°F), its consumption should be increased at least up to 15-20% of the stream 23 as the increase of consumption tends to cooling, the concentration of NH3at the top of the dehydrator is reduced.

The dehydrator 54 may be a column with a small number of plates (preferably the column cap plates), at the bottom of which is a tank containing liquid NH3if this is the level control. When is provedenii operations in terms of recycling (on start) for syngas compressor you can use a reverse cooler (not shown). In order to remove the oil when it is undesirable emissions from the compressor may be required at the outlet of the compressor to set the separator (not shown). For flow of the liquid ammonia in the dehydrator 54 on stage leaching need to pump for NH3no. This is because the dehydrator 54 operates under moderate pressure, which is much lower than the pressure in the separator 67, the feed liquid NH3. This represents a significant improvement compared with the previous technology use scrubber high pressure, requiring the pump and stock. For example, in the nominal synthesis loop at 2000 pounds per square inch separator 67 will be under pressure of approximately 1950 pounds per square inch, while the dehydrator 54 under pressure, constituting approximately 800-900 pounds per square inch. It should be noted that the washing is carried out to isolate the flow of additional gas, and for the combined incremental/reverse flow, it is not required (as is necessary for example, in U.S. patent 1830167 and patent Canada 257043).

For the reconstruction of the dehydrator of the present invention to the existing installation (but, of course, not new), required some modification of the system of filings in circuit synthesis. The release of the circulating compressor wheel is connected with a pipe is ATiM inlet of the heat exchanger 59. Effluent Converter with a housing of the heat exchanger 59 is directed to the inlet of the exchanger 62. Instantly evaporating gas leaves the separator 67, passes through the tubular wall of the exchanger 66 and, after cleaning the outflow is directed to the inlet of the back wheel. Need a little liquid pipelines NH3from separator 67 to dehydrator 54 and the bottom of the dehydrator drum 69.

The present invention has one or more of the following features and has advantages over previous schemes of technological processing.

Unlike used in previous technology multistage cleaning, cleaning incremental synthesis gas is carried out in one stage (in the dehydrator). On the contrary, in U.S. patent 3349569 shown that for washing and further purification NH3this gas condense after the suction scrubber between stages of the compressor. Due to the fact that the additional need for cooling between stages of the compressor (for example, what was necessary under the scheme of U.S. patent 3349569) are excluded, the present invention reduces capital and operating expenses. In addition, it eliminates the unwanted return of NH3in the preprocessor setup, as it occurred on the suction scrubber in U.S. patent 3349569.

The decrease in the rate of syngas compressor temperature is raised by the exhaust gas dehydrator, selected intermediate stage of the compressor, in particular, the gas outlet of the dehydrator from the space between the first and second stages of the compressor. For example, please refer to the drawing. It shows the exhaust gas emerging from the first stage 50 of the compressor. Exhaust gas, as described above, is cooled in heat exchanger 52 and dehydrated in a dehydrator 54, this happens before in the form of a stream of 8 it will be sent to the second stage 56 of the compressor when the temperature of approximately -23,3°C(-10°F). The result is a reduction of the load for the second and third stage ("working the wheel") of the compressor, which will be described in more detail below. In the previous configurations of technological schemes such benefits were received. The temperature at the inlet to the second stage lower than at the outlet of the dehydrator, it is approximately -10°F (previous standard schemes it was approximately 40-45°F). Lower temperature reduces the load on the compressor second stage. In addition, the discharge temperature at the second stage, respectively below, because it is determined by the equation T2=T1·(P2/P1n-1/n-1), where T1=inlet temperature, T2=temperature, P1=inlet pressure P2=pressure at the exit, a (n)/n=(k-1)/(k· ep), where k=Cp/Cv, EP=polytropic efficiency of the compressor CP=specific heat at constant pressure, and Cv=specific heat at constant volume.

Lower inlet temperature provides a lower discharge temperature. This means that the temperature of the mix at the entrance of the back wheels is lower than the previous standard technology since before mixing release from the second stage and the reverse flow is not being cooled. Introduction in this process dehydrator can increase performance by about 3-4%, if it is limited by the drive power of the gas compressor outlet, and approximately 8-9%if performance is limited by the drive power of the refrigeration compressor. Introduction dehydrator in the process provides the conditions are relatively mild compared to previous technological schemes, this means that there is no need for special low-temperature structural materials (materials developed for temperatures below -20°F).

Introduction in the process dehydrator reduces the pressure in the synthesis loop, which is approximately 5% lower than the pressure in the suction scrubber from U.S. patent 3349569. In the system of the present invention, the content of NH3in the upper chase dehydrator is 3.5% (compared the structure from 4.9% for the suction scrubber), and the content of NH3supply Converter below, it is 2.3% (compared to 2.6% for the suction scrubber). This leads to reduced circulation in a given volume, and therefore to decrease the pressure drop.

Safe and continuous operation of the Converter is guaranteed, because blagoje must be at least as full (if not more)as in the diagram on the previous technology. Water removal should be done in the dehydrator, including a specially designed column (designed for this purpose rather than for the previously used)by accidental contact with liquid NH3as long as the flow discharged from the compressor passes to the separator in the freezer and pipeline. The latter approach is illustrated in U.S. patent 1815243.

Dehydrator of the present invention is connected (as shown for example in U.S. patent 1830167 and patent Canada 257043), so that the processing has been only incremental gas, and not the combined stream extension and the circulating gas. This significantly reduces the size and cost of the dehydrator.

Work dehydrator is continuous, and hence is much easier than in previous systems using molecular sieves. In the system of the present invention does not require any expensive and require a high Uro is nya maintenance of switches, as in the flowsheet with molecular sieves. In addition, the cost of the mounting system of the present invention is much lower (60-70%)than systems with molecular sieves. Energy saving dehydrator comparable to the savings in the system of the molecular sieve.

Rinsing stage dehydrator, removes water, mainly located (as noted above) between the first two stages of the syngas compressor. Intermediate stage of dehydration is the best for several reasons; these include the reduction of energy consumption, decrease the speed of the syngas compressor and increase performance.

High blood pressure, when running the dehydrator of the present invention (for example, approximately 800-900 pounds per square inch)is sufficient to remove the water has been adequately and sufficiently without the use of further contact with liquid NH3. Use dehydrator for washing incremental synthesis gas liquid NH3at elevated temperature provides the removal of impurities (mainly water, but also traces of CO and CO2to make incremental synthesis gas suitable for the catalytic synthesis of NH3. Is substantially complete removal of water, after only one theoretical stage of contact of the liquid with gas residual is the amount of water in the dehydrator is 0.1× 10-6that provides satisfactory operation of the Converter and high catalytic resource. For standard catalyst ammonia Converter maximum content of atomic oxygen in the feed stream is 3×10-6. In the most standard synthesis systems use secondary instantaneous evaporation (see patents 1815243 and 3350170), and removal of water depends on the contact between the condensing NH3and synthesis gas passing in the exchangers and pipelines. It was found that the removal of water by prior technology is far from complete, some measurements show that the water content in the initial reaction mixture Converter is 15×10-6. While indirectly to standard catalysts for ammonia synthesis is satisfactory (although contributing to the reduction of the durability of the catalyst), but these options are unacceptable to the newly developed noble catalysts for the synthesis of ammonia.

In accordance with the present invention for optimal performance and maximum energy efficiency was carried out reflow closed circuit synthesis. For interstage dehydration synthesis gas using the dehydrator, the result is the removal of water, so reflow closed circuit synthesis becomes possible is. Washed incremental gas can be mixed with the circulating gas with a reduced content of NH3and be sent directly to the ammonia Converter (drawing number 60). Then effluent ammonia Converter can be sent directly to stage cooling/freezing (excluding the incremental dilution gas), while saving energy artificial cooling. After removal of NH3(in the separator 67) and after purification reset (by pipeline 32) of the circulating gas is fed to the third (current) stage of the compressor. Ready NH3at the stage of recycling is not subjected to compression, which saves energy. In addition, reflow closed circuit synthesis at a fixed output pressure of the ammonia compressor reduces the pressure at the outlet of the syngas compressor. This is due to the fact that compared to previous technological schemes between the compressor and Converter are fewer pieces of equipment. The last is one of those factors that reduce the capacity and contribute to the reduction of energy consumption. The main reason for the decrease of energy consumption in reflow scheme is that due to increasing dew points in effluent Converter coming in dehydrator excess NH3may condense in this scheme with the Auray when using cooling water, than cooling freezers. Thus, a significant increase in the capacity of the compressor synthesis gas occurs without loss of refrigeration capacity of the compressor. Such reflow closed loop ammonia synthesis also allows greater heat recovery in the heat exchanger (node 61 in the drawing), which is used to heat the boiler water supplied by heat exchange with effluent ammonia Converter (node 60 in the drawing), since the energy, which is the third stage or on the back wheel (node 57 in the drawing) of the compressor is directed to the ammonia Converter. In previous technologies, on the contrary, this energy was directed to a water-cooled exchanger as it occurs in constructions with secondary ultrafast evaporation (type structures from patents 1815243 and 3350170). Another advantage realized when reflowed closed circuit synthesis, is the exclusion of her freezer and wash separator gas. New design saves money and energy, regardless of whether the design of new or reconstructed. The reason for this is that the flushing gas is frozen at successively higher levels of cooling in a closed circuit synthesis, reflow in accordance with the practice of the present invention, while predydushih designs it was cooled using only the most cold level. In the end, a substantial energy saving of approximately 0.5 MM BTU/ST (where ST means a small ton or 2000 pounds of ready-NH3), is a result of the use of interstage dehydrator of the present invention.

The original layout of the synthesis loop is preserved even if the dehydrator (drawing number 54)located between the first (in the drawing at number 50) and second (in the drawing at number 56)compressor, can be used to facilitate removal from synthesis gas water (and other impurities). In the absence of benefit from significant energy savings due to the above-described reflow circuit synthesis, preserved in the syngas compressor energy is mainly compensated by the need for higher cooling capacity. In this case, the main prize will be a significant increase in the durability of the catalyst Converter due to lower water content. In addition, the compressor load the synthesis gas will be transferred to the refrigeration compressor. In the syngas compressor will receive a speed reduction of approximately 2%. This may be suitable for installations in which limited the syngas compressor and refrigeration compressor which has the additional bandwidth (for example, in cold climates or in the winter for a warmer climate). In these conditions it is possible to get more performance installation.

In accordance with the practice of the present invention stage leaching is located between the first two steps (figure numbered 50 and 56) of the syngas compressor. This location is the best for several reasons, including reducing the required amount of energy, decrease the speed required for the syngas compressor and increasing productivity. Non-rigid working conditions mean that no special low-temperature materials and that in the repair of existing installations can be left without changing modern metallurgy. In new installations of low-temperature metallurgy need less. Reset, dehydration and cooling is carried out between the first and second stages, eliminates unwanted return of NH3in the preprocessor setup, as it happens when using the suction scrubber (described in U.S. patent 3349569).

The amount of high pressure dehydrator, approximately 800-900 pounds per square inch, sufficient to carry out an adequate and substantially complete removal of water, when it is not used further contact with liquid NH3as described in U.S. patent 3349569.

From the practice of the present invention is excluded clean is the need for extensive cooling between stages, as for condensation of NH3no cooling is required and extensive freezing of the gas from the intermediate stages of the compressor. On the contrary, the refrigeration power consumed to achieve deep cooling (-5° (C)-(-50° (C), or from 23 to -58°F (referred to in U.S. patent 3349569)must equal or exceed the power savings in this scheme, the syngas compressor. We also exclude the extensive investments required in constructions according to the previous technology. For reconstruction (repair existing installation) you can use the existing heat exchangers upstream of the dehydrator.

On cooling the synthesis gas between the first and second steps of the beneficial effects instead of one have both stages of the syngas compressor. The design of the most used compressors easily make hardware changes; these include the placement of the compressor of the second stage and the third compressor stage (reverse) in the same building, but the compression of the working wheel is subjected to the combined flow of additional gas and recycled synthesis gas. From dehydrator frozen gas delivered to the second stage of the compressor, and after compression the temperature at the outlet is lower because it is determined by the equation T2=T1(n-1)/n. Then this thread without further what about the cooling mixed with reverse, therefore, the temperature of the combined stream below. Lower temperatures at the inlet to the second and third stage will have lower energy needs of both levels because they are well known polytropic relation P=K/ep·MPH·T1·Z·n/(n-1)·(P2/P1(n-1)/n-1), where P=power, K is a constant, MRR=molar flux in moles per hour, Z=compressibility, and ep, n, P1P2and T1were defined above. At the entrance to the second stage of cooling is stronger than in the parallel branches increased molar flow (as shown below), in which only the second stage receive a 7% saving. Other factors in the equation above substantially constant, which gives

P=(460-10)/(460+41)·(1,035/1,00)=0,93

On stage recycle inlet temperature is lower for the reasons mentioned earlier. In addition, the rearrangement circuit synthesis affects the temperature at the inlet and the flow (since the finished NH3not subjected to compression), so is 12% energy savings are shown in the following further calculations:

P=(460+114)/(460+150)·(0,935/1,00)=0,88

In addition, the circulating power is slightly reduced, which causes a further pressure drop. Power on the first stage should be almost the same, so the amount of the reduction capacity of the compressor, the synthesis gas is approximately 6%. Simplistically this is expressed by the equation:

P=(1,0·0,36)+(0,93·0,36)+(0,88·0,28)=0,941

Of course, when using a dehydrator between levels there is some redistribution of power to match the performance of the compressor. This leads to the fact that the ratio of pressure for the first stage lower, and the ratio of pressure for the second stage, respectively, higher. Still, the total energy remains approximately equal to 6%. The input volumetric flow is also small, the speed of the compressor is lower (approximately 3% during reflow circuit synthesis) and, therefore, operational complexity less. This advantage (positive impact dehydrator for two steps) in constructions according to the previous technology was not implemented.

Liquid NH3serves on stage leaching from pressure separator at higher pressure. During normal operation does not require a pump.

Flushing is limited only by the flow of additional gas, not combined stream extension and the circulating gas, as described in U.S. patent 1830167 and 257043. (It was noted that in U.S. patent 3349569 washed only incremental stream).

The drop in pressure in the closed circuit synthesis is lower than in the case of suction scrubber (for example, pokazanego U.S. patent 3349569), provided that further condensation NH3between the steps is not performed. This is due to the fact that in the upper part of the dehydrator (54) the concentration of NH3lower than in the suction scrubber from previous technological schemes (3.5% and 4.9% respectively), and also due to the fact that the pressure in the dehydrator above the pressure in the suction scrubber from previous technological schemes (850 and 350 pounds per square inch, respectively). Therefore, the concentration of NH3in applying to the ammonia Converter (60) is lower than in the previous technological schemes (2.3% and 2.6% respectively). In the scheme of the present invention at a fixed concentration of NH3the output from the Converter changes the concentration in parallel Converter must be greater than the change for U.S. patent 3349569 under which a given capacity and lower pressure drop is smaller circulation. This also leads to the fact that you want a lower power recycling.

Typically, the amount of liquid NH3that is used for washing should be 10-15% of the total amount of fluid flowing from the high pressure separator. When reducing the amount of liquid ammonia is reduced re-admission of inert substances in closed loop fusion, the same applies to gabarito cost of pipelines for liquids, valves and equipment for cleaning.

Before leaching incremental gas pre-cooled (the process is carried out in a cooled vessel typically to a temperature component of approximately 38-45°F). The specified pre-cooled in order to remove the condensed water is carried out using wybitnego drum. This reduces the water content in the saturated gas, and also reduces the load on the scrubber. Pre-cooling reduces the content of NH3in the pair from the top of the dehydrator, and therefore, the content of NH3download Converter. Furthermore, the reduced temperature in the upper part, which has a favorable effect on the already mentioned power and speed of the compressor.

In less standard designs installation of ammonia synthesis uses a closed loop at 2500-3000 pounds per square inch(175-210)·105PA), which used a four-stage compressor (three incremental steps and one recirculating). Usually two incremental steps placed in the first housing of the compressor and the second compressor housing is a structure with four nozzles. In this design dehydrator (type dehydrator 54) can be placed after the first incremental step, after the second incremental steps or under the pressure of the synthesis loop - after t is ETA incremental steps. In short, the selection of incremental synthesis gas compressor, dehydrator can be done with any intermediate stage of compression, and to return to the compressor at the entrance to the next level.

It is preferable, however, that in such cases the gas sampling was performed after the second incremental steps, this is due to three reasons. At this stage compression pressure must be large enough to ensure adequate removal of water. At the same time, the effect of freezing will be useful for the third incremental stage of the compressor, and therefore the necessary power and speed are reduced. Finally, the reconstruction of existing installations the freezer is already in place.

In closed circuits synthesis at a higher pressure (2500-3000 psi) ((175-210)·105PA) dehydrator is better to place between the second and third stages of the compressor and to work better under pressure, constituting approximately 1200-1400 pounds per square inch(84-98)·105PA). Thus, in this four-stage configuration of the compressor synthesis gas is withdrawn from the second stage of the compressor under pressure, constituting approximately 1200-1400 pounds per square inch(84-98)·105PA), and the fourth stage of the compressor under pressure, constituting approximately 2500-3000 pounds kvadratnymi ((175-210)· 105PA).

Skilled in this technology, people should be clear that in the above-described private options, you can make many changes, but these changes are the essence of the present invention, defined here by the claims.

1. The process of obtaining ammonia by compressing containing hydrogen and nitrogen synthesis gas in a multistage compressor, each compressor has an inlet and connected with it the release, contacting the compressed synthesis gas and a suitable catalyst ammonium reactor under conditions that promote interaction of the parts, less than the entire amount of hydrogen and nitrogen synthesis gas with obtaining ammonia, separating the finished of ammonia coming from the ammonia Converter flow effluent reactor, return to the multistage compressor part of the flow effluent reactor containing unreacted hydrogen and nitrogen, removal of the compressor flow incremental synthesis gas, cooling and dewatering flow exhaust synthesis gas, and stage of dehydration is carried out by contacting the exhaust flow synthesis gas with liquid ammonia, and return to the compressor flow cooled and dewatered synthesis gas, wherein the exhaust flow synthesis gas discharged through the output of the first stage of compr the quarrel, and return in the specified compressor at the inlet to the second stage.

2. The process according to claim 1, characterized in that the output of the first stage of the compressor away, cool and dehydrate the entire flow of the synthesis gas.

3. The process according to claim 1 or 2, characterized in that the multi-stage compressor is a three-stage compressor, and additional synthesis gas away from the first stage at a pressure of approximately (56-63)·105PA, divert from the second stage at a pressure of approximately (126-133)·105PA and away from the third stage at a pressure of approximately (140-147)·105PA.

4. The process according to claim 3, characterized in that the incremental synthesis gas undergoes no cooling between the second and third stages of the compressor.

5. The process according to claim 3, characterized in that before returning to the compressor flow synthesis gas is cooled to a temperature factor of approximately 20.5 and to 26.1°C (-5 to -15°F).

6. The process according to claim 1 or 2, characterized in that the flow of synthesis gas return from the dehydrator in the compressor without reheating.

7. The process according to claim 3, characterized in that the content of N2About the exhaust flow of the synthesis gas before returning it to the compressor is reduced to the value component is less than 0.1 parts by volume per million.

8. The process according to claim 1 or 2, characterized in that the synthesis gas contains water the genus and nitrogen at a molar ratio, of approximately 3:1.

9. The process according to claim 1 or 2, including cooling of the exhaust from the syngas compressor for condensing the contained ammonia and removing the condensed ammonia from the synthesis gas prior to its introduction into the ammonia Converter.

10. Installation for implementing the process of obtaining ammonia by compressing the synthesis gas containing hydrogen and nitrogen, in a multistage compressor having at least first and second stage, and each stage compressor has an inlet and connected with him the issue, the process includes contacting the compressed synthesis gas into ammonium reactor with a suitable catalyst under conditions that promote interaction of the parts less than the whole amount of hydrogen and nitrogen synthesis gas with obtaining ammonia, separating the finished of ammonia coming from the ammonia Converter flow effluent reactor, return to the multistage compressor part of the flow effluent reactor containing unreacted hydrogen and nitrogen, as well as contacting the synthesis gas with liquid ammonia in the dehydrator equipped with a feed inlet for incremental synthesis gas, the release for the synthesis gas, as well as inlet and outlet for liquid ammonia, characterized in that the compressor is equipped with a production of synthesis gas, connecting the hydraulic connection issue with the first is level with the inlet of the synthesis gas in the dehydrator, intermediate the inlet synthesis gas, which connects the hydraulic connection inlet to the second stage with the release of the synthesis gas from the dehydrator, which determines the path of movement of the synthesis gas from the outlet of the first stage through the dehydrator, and therefrom to the inlet of the second stage.

11. Installation according to claim 10, characterized in that the inlets synthesis gas and liquid ammonia, and their releases are so that in the dehydrator liquid ammonia is moved in counter-flow to the synthesis-gas.

12. Installation according to claim 10 or 11, comprising a heat exchanger for cooling the synthesis gas, and vapor-liquid separator for separation of H2About located in the path of movement of the synthesis gas between the first stage compressor and the inlet of the synthesis gas in the dehydrator.

13. Installation according to claim 10 or 11, characterized in that the multi-stage compressor is a three-stage compressor.



 

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