CN112299446A

CN112299446A - Open type synthetic ammonia system

Info

Publication number: CN112299446A
Application number: CN201910669357.1A
Authority: CN
Inventors: 曹为平
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-07-24
Filing date: 2019-07-24
Publication date: 2021-02-02

Abstract

The invention discloses an open type ammonia synthesis system, and relates to the industrial technology of ammonia synthesis in the field of chemical industry. The system separates the residual gas of liquid ammonia through cooling after the hydrogen-nitrogen synthetic ammonia in the synthetic tower is discharged, and sends the residual gas into other synthetic towers for continuous synthesis if the residual gas needs to be continuously synthesized. A plurality of synthetic towers are connected in series from large to small by one stage in a way of not establishing a loop, and the same stage can also be formed by connecting a plurality of synthetic towers in parallel to form a production system. The first stage only feeds fresh hydrogen and nitrogen raw gas containing a small amount of inert gas, and the later stage only feeds residual gas after the ammonia is cooled and separated from the tower at the front stage. When the accumulation of the inert gas is equivalent to that of the circulation method, most of the gas is synthesized under the condition of low inert gas, and the gas concentrated by the inert gas is completely discharged as tail gas in the last stage, so that the advantage that the fresh gas is less in inert gas and does not contain ammonia is fully utilized, the ammonia output is greatly improved, and compared with the circulation method, the yield can be increased by more than 30-40%, the electric energy is saved, and the raw materials are more fully utilized.

Description

Open type synthetic ammonia system

Technical Field

The invention belongs to the synthetic ammonia industrial technology in the chemical industry field, and particularly relates to an open synthetic ammonia system.

Background

Since the synthesis of ammonia by Haber in 1912, a recycling method was used. The haber finds that the synthesis rate of ammonia is very low, so that only a circulation method is used, hydrogen and nitrogen raw materials containing a small amount of methane, argon, helium and other inert gases are compressed and sent to a synthesis tower, a catalyst is used for reaction, a part of ammonia is synthesized, after the ammonia is discharged from the tower and cooled and separated, a large amount of effective components such as hydrogen, nitrogen and the like still exist and cannot be discarded, and then fresh raw materials are supplemented and sent back to the original synthesis tower again for synthesis. As shown in figure 1, a small amount of inert gas mixed in the raw material occupies space, and the inert gas passes through the catalyst and does not have the function of synthesizing ammonia. This will reduce the synthesis efficiency of the synthesis column, so the lower the inerts the better. However, although the content of the inert gas in the fresh raw material gas is not very high, the circulation method causes the inert gas to be accumulated and repeatedly circulated in the synthesis system. After the gas after cooling and separating ammonia from the synthesis tower is mixed with the supplemented fresh gas, the fresh gas is not fresh, so that more and more inert gases are in the synthesis tower, and the synthesis is more and more disturbed. In order to prevent the inert gas from being too high, a part of the gas separated from the synthesis tower must be discharged, which is called tail gas. When the output is low, only the lighting dome lamp is burnt out and can be used as fuel. This not only results in raw material loss, but also results in low synthesis efficiency due to the high content of inert gas during operation of the synthesis column. The tail gas is collected and utilized, the gas quantity to be treated is large, and the cost is high. This method has been used until now over the past century, with improvements.

Disclosure of Invention

The open type synthetic ammonia system is characterized in that after the hydrogen-nitrogen synthetic ammonia in the synthetic tower is discharged from the tower, the residual gas of the liquid ammonia is separated through cooling, and the residual gas is sent to other synthetic towers for continuous synthesis if the residual gas needs to be continuously synthesized.

Preferably, in the open type ammonia synthesis system, a plurality of synthesis towers are connected in series to form a multi-stage system, the multi-stage system is a two-stage synthesis tower and more than two stages, the synthesis tower without other synthesis tower residual gas input at the forefront is a first stage, adjacent stages are respectively called as a front stage and a rear stage, and one multi-stage system has at least two stages.

Preferably, in the open ammonia synthesis system, the gas entering the synthesis tower is any gas mainly containing hydrogen and nitrogen, wherein the gas entering the first stage synthesis tower is mainly fresh raw gas of which inert gases such as methane, argon, helium and the like are not concentrated yet, and the gas entering the other stages synthesis tower is mainly from the rest gas of the other synthesis towers.

Preferably, in the open ammonia synthesis system described above, the transmission path of the surplus gas is from the preceding stage to the succeeding stage, except for the open ammonia synthesis system having only two stages, the first stage having no surplus gas input, when having a size different from that of the second stage, and the last stage having no succeeding stage, allowing the surplus gas input thereto to establish a circuit production.

Preferably, in the open ammonia synthesis system, the same stage can be composed of at least two synthesis towers connected in parallel, and the capacity of the synthesis tower of the stage is the sum of the capacities of the synthesis towers connected in parallel.

Preferably, in the open ammonia synthesis system, from the first stage to the last stage, the capacity of each stage of synthesis tower is gradually reduced along with the synthesis and cooling separation of hydrogen and nitrogen gas to separate liquid ammonia, the volume of gas entering and exiting is smaller, the accumulated amount of inert gas is gradually increased, the number of the latter stages is larger than that of the former stages, until most hydrogen and nitrogen gas is synthesized and separated as liquid ammonia, when the amount of inert gas in the residual gas is insufficient to continue producing synthetic ammonia, the residual gas is discharged as tail gas in one step, and the last stage establishes a synthesis tower which is looped to circulate, and the capacity of the synthesis tower is not limited by the capacity.

Preferably, in the open ammonia synthesis system, the working pressure of the same stage must be the same, the different stages are not constrained, the pressures of the stages are the same or different, and recompression or decompression is required.

Preferably, in the open ammonia synthesis system, the residual gas in each stage of the synthesis tower is not compressed, so that the open ammonia synthesis system is a compression-free fully-closed pressure-reduced open ammonia synthesis system, and the fresh gas enters the system under pressure, enters each stage of the synthesis tower in sequence, is synthesized, cooled, separated, resynthesized, recooled, separated, resynthesized, … … and reaches the last stage of discharge system after being pressurized.

Preferably, in the above open type ammonia synthesis system, the open type ammonia synthesis system is an open type ammonia synthesis system with increasing pressure from low pressure to high pressure of each stage of the synthesis tower from the first stage to the last stage, or an open type ammonia synthesis system with increasing pressure and then decreasing pressure of each stage of the synthesis tower.

The invention has the beneficial effects that: according to the device constructed by the open type ammonia synthesis system, the yield can be improved by more than 30 percent and more than 40 percent by using equipment with the same quantity, and meanwhile, the electric energy is saved, and the raw materials are more fully utilized.

Drawings

FIG. 1 is a schematic view of a connection structure of a circulation ammonia synthesis plant in the background art;

FIG. 2 is a schematic front view of an open ammonia synthesis system according to a first embodiment;

FIG. 2.2 is a schematic front view of an open ammonia synthesis system according to the first and second embodiments;

FIG. 3 is a schematic front view of an open ammonia synthesis system according to a second embodiment;

FIG. 4 is a schematic front view showing the structure of an open type ammonia synthesis system according to a third embodiment;

FIG. 5 is a schematic front view of an open ammonia synthesis system according to a fourth embodiment;

FIG. 6 is a schematic front view of an open ammonia synthesis system according to the fifth embodiment.

Detailed Description

The conventional recycling method in the background art has the above-mentioned problem, and the key point is the recycling method. To avoid this problem, there is only one approach, that is no or few cycles.

As long as all fresh raw gas enters the synthesis tower, the inert gas is not high, the efficiency of ammonia synthesis can be greatly improved, and fresh gas containing less inert gas is used as a resource to be used.

What is then what is the residual gas from the synthesis column after cooling and ammonia separation (hereinafter referred to as residual gas)? They still contain much hydrogen, nitrogen, etc., and the concentration of inert gases is increased, not much higher, and cannot be discarded. Or the fresh gas contains few resources of inert gas, is not fully utilized and is precious. The idea is to feed all of them to another synthesis column, in contrast to the previous column and referred to as the first stage. And it is referred to as the second stage.

The residual gas after cooling and separating ammonia from the second-stage synthesis tower is much, the concentration of the inert gas is increased, but the resource of fresh gas with little inert gas is still not fully utilized. They are sent to the third stage of the synthesis tower for production. … …, so that the stages are connected to each other in a string.

Because of the less and less residual gas at each stage, the synthesis columns required at each stage are also smaller and smaller. And the inerts are increasingly accumulating. However, the inerts at each stage are still much lower or lower than in the recycle process. The fresh gas has less resource containing inert gas and is still used continuously, and the efficiency of synthesizing ammonia is still higher than that of the circulation method.

By the time the inerts rise to tens of percent, as in the recycle process, ninety-five percent of the feed gas has been synthesized. Only a few percent of the total gas enters the stage, only then is the efficiency comparable to the recycle method.

This is open. Therefore, in general, the ammonia is synthesized in the condition of low inert gas, and the efficiency of the synthesis tower is fully exerted. The capacity of other equipment is fully utilized, for example, because the synthesis rate is high, the volume of the gas discharged from the tower is greatly reduced, the non-ammonia gas during ammonia cooling is greatly reduced, and the useless work of treatment is greatly reduced. If compression is desired, the amount of compression is also greatly reduced. Overall, throughput is increased and consumption is reduced.

One more to two stages are also possible. Although the content of the inert gas is higher than that of the recycling method, the method is additional income, and the raw material gas is low in content of the inert gas and the resources are recycled after being fully utilized.

The residual gas of the last stage is treated separately in one time until no synthesis is performed. Referred to as the tail gas of the open synthesis of ammonia.

Because the synthesis rate is increased, the temperature is increased, the gas volume is greatly reduced, the space velocity can also be increased, and the space velocity also needs to be increased to reduce the temperature of the tower outlet, thereby further increasing the synthesis amount of ammonia. In general, the space velocity can be increased by a factor of four or more over the cyclic process.

Because of synthesis, the volume is reduced when the synthesis passes through one stage, so that the synthesis tower is smaller than the synthesis tower from the front stage to the rear stage.

In addition, the fresh raw material gas does not contain ammonia, so that the first-stage synthesis efficiency is improved. It is also utilized as a resource. The residual gas is reduced with the lower stage, and the contained ammonia is harvested in the morning and at night. This is the basic method of the present invention.

After ammonia is separated from gas coming out of the synthesis tower, the gas is not returned to the original synthesis tower, and is completely sent to another synthesis tower without circulation and loop establishment, which is the general rule of the invention.

The synthesis towers can also be connected in parallel, and one or more synthesis towers can be accommodated in the same stage to be spliced into a large size. The splicing is carried out more and less, and the splicing is not limited after the front splicing and the back splicing. It can also be built into a large-scale synthetic ammonia device with a plurality of synthetic towers arranged in an array for production.

The open used equipment and traditional circulation method are mutually universal, the synthesis temperature and pressure are identical, the temperature for cooling and separating ammonia is identical, and the adopted fresh raw material gas is also universal with circulation method-hydrogen-nitrogen gas containing inert gas methane, argon and helium, and is characterized by that several synthesis towers and their matched equipment are completely different in structure.

Each stage of synthetic tower is connected with a heat exchanger (a waste heat boiler and a preheater), a water cooler, a liquid ammonia separator and a cold exchanger through pipelines and valves, and further comprises a re-compressor, an oil remover and the like under the condition of requirement, so that an open synthetic ammonia system is constructed for production.

Because of low inert gas, the advantages of less fresh inert gas and no ammonia are fully utilized, thereby greatly improving the production capacity, reducing the consumption, reducing the output, using less equipment and saving the electric power. And a series of inventions are linked by the method.

The invention has no special requirements for fresh raw gas and recycle method ratio. Less inert gas can be used, and slightly more inert gas can obtain far higher benefit than the circulation method. Even if the fresh gas containing higher inert gas is used, the fresh gas can be made into several stages, and the yield is increased compared with that of the excellent gas used by the circulation method, and the fresh gas is produced after the volume is greatly reduced and the inert gas is high and the inert gas is intensively removed, so that the treatment capacity is greatly reduced.

It is not necessary to excessively pursue the cleanliness of fresh gases such as air separation and liquid nitrogen rinsing to remove inerts, etc. The higher the inert gas of the circulation method, the more remarkable the effect of adopting an open type. The benefit of too low content of inert gas is increased rather insignificantly.

The open type synthetic ammonia has no special requirements for equipment and is suitable for super-huge, large, medium and small equipment. All equipment used in the circulation method can be used. Unless not required or used. For example, synthesis columns with various internal structures and catalysts can be used, and the pressure and the temperature of the circulation method synthesis are open pressure and open temperature. Accordingly, the pressure, synthesis temperature, catalyst and the like of the open type synthesis ammonia are different according to the different synthesis towers.

Because the synthesis rate is high, the temperature of the discharged gas is greatly improved, so that the cooling is increased, but the increased gas is water cooling, the generated high-temperature steam can be utilized, and the high-temperature high-pressure steam is a harvest, and can push a steam turbine to provide power or generate electricity.

Open ammonia cooling temperatures are also the same as for the recycle process. Because the synthesis rate is high, the gas volume is reduced violently, the resistance is reduced correspondingly, the residual gas after the gas is taken out of the tower and is cooled and separated from liquid ammonia is reduced, particularly non-ammonia gas is reduced, and a re-compressor and cooling and separating equipment are greatly saved. The residual gas reduces the saved ammonia cooling, and can eliminate most of even all of the increased refrigerating capacity of liquefied ammonia.

The open method cannot be emptied because of large production capacity and large concentration of tail gas, which must be utilized. And the same-yield circulation method is smaller than the tail gas volume, and the concentration of the inert gas is higher, so that the treatment is facilitated. The processing cost is also low. The treatment method can be used in an open system, such as membrane separation, cryogenic separation, etc., as the circulation method can be used. The separation is not necessary to be complete, and the full utilization can be realized, thereby reducing the cost. Such as: after most of inert gas and redundant nitrogen are removed, the grades with insufficient space velocity and low hydrogen-nitrogen ratio can be supplemented, so that the hydrogen-nitrogen ratio can be completely utilized and improved.

The method only improves the synthesis section of the ammonia synthesis plant. The production of other superior products such as gas making, refined gas and inferior ammonia products (such as chemical fertilizer and explosive) is not in the invention, and all the processes used by the circulation method can be used. The circulation method can still deal with the purge gas released when the liquid ammonia is depressurized.

The haber's circulation method and my open type are two major inventions in parallel in the synthetic ammonia industry, and the open type can also be divided into specific application schemes of various categories, fine categories and thousands of categories, just as the haber method can be divided into various categories, fine categories (such as high pressure, medium pressure, low pressure, osmium catalyst, iron catalyst, ruthenium catalyst, potassium ferrocyanide catalyst, temperature is high, medium and low, synthesis tower is upright and lying) and thousands of different specific implementation rules. The above-mentioned open spirit can be appreciated, and the production apparatus can be arranged and organized according to the respective conditions, owned equipment and funds. All have the characteristics of being different and unlimited.

Breaking the circulation without building a loop is the principle of the invention. Individual levels may be allowed to establish loops in special cases.

The invention is further illustrated by the following specific examples:

as shown in fig. 1, fig. 2, fig. 2.2, fig. 3, fig. 4, fig. 5, and table 4, when designing an open type ammonia synthesis system, the type of the synthesis column to be used is first determined, and the size (expressed by the catalyst volume) of each stage of the synthesis column is determined. To this end, it is necessary to know the capacity of each synthesis column, and first determine the relationship between space velocity and ammonia content in the gas leaving the column, and preferably establish an empirical formula. For a synthesis column operating under a certain amount of inert gas and ammonia fed into the column, several points are taken and a regression equation is established, generally a cubic regression equation is sufficiently accurate.

The following were used:

y＝ax³+bx²+cx+d

this empirical formula is determined by the configuration of the synthesis column and the catalyst, and its set operating pressure and temperature.

x is space velocity (unit can be taken as one hundred thousand), and y is the ammonia content percent of the tower gas.

This is carried out by introducing inert gas r into the column₁Into the column of ammonia y₁' space velocity of lower production and ammonia content of tower gas.

For any gas fed into the tower containing inert gas r and ammonia y' fed into the tower:

y＝(ax³+bx²+cx+d)×((1+y1'+r1)/(1+y1'-r1))×((1+y'-r)/(1+y'+r))

referred to as empirical formula 1.

For a selected space velocity and catalyst volume of the first stage synthesis column, a space velocity is calculated, or the volume of the gas entering the column is calculated based on the selected space velocity and catalyst volume.

Then, according to empirical formula 1, the ammonia content (generally 0%) and the inert gas content of the fresh feed gas are calculated as follows: the ammonia content and volume of the tower gas, the volume percentage of the tower gas, the ammonia volume and non-ammonia volume of the tower gas, and the reduced volume and reduced volume percent of the tower gas. The temperature of the column gas is also calculated. Thereby determining the amount of cooling and cooling equipment required.

According to the cooling capacity of the cooling device and the ammonia content in the gas after cooling and separating ammonia determined by the cooling capacity, the following calculation is carried out: the gaseous volume of the extracted liquid ammonia, the volume of the unretracted ammonia, the volume of the raw material gas for extracting ammonia after synthesis, the volume of the residual gas after separating liquid ammonia and the volume percent of the residual gas are ammonia entering the tower, the concentration of inert gas, the hourly output and the daily output. Annual production can be calculated from the working days of the year. The percent yield increase of the specific cycle method can also be calculated.

The volume of the first-stage residual gas is the volume of the second-stage tower inlet gas, the concentration of the inert gas contained in the second stage is the concentration of the inert gas of the first-stage residual gas, and the content of the ammonia entering the tower is the ammonia content which cannot be separated. If pressurization is required, the synthesis pressure of the second stage of the synthesis tower is added, and the required capacity of a recompressor and an oil remover are calculated and determined.

As with the first stage, an empirical formula is determined for the second stage synthesis column and the respective data is calculated from the empirical formula and the cooling equipment.

The following stages are all so calculated.

The synthesis column and its size and capacity are so determined. The equipment is then selected and manufactured for installation.

After production, generally not exactly the same as that determined during design, close attention is paid to the situation after production, and it is understood that, particularly during design, the selected space velocity is never the optimum, some equipment may be insufficient to become a bottleneck for further production increase, and other equipment may be insufficiently utilized and may have potential to be excavated. The optimum hydrogen-nitrogen ratio of the feed gas to the column is also determined in post-production tests. The above items must be fumbled with fine adjustments.

The open system, like the recycle method, gives rise to the problem of optimum hydrogen to nitrogen ratio. Therefore, after the open production plant is constructed, close attention is paid to experience so as to produce the product under the condition of optimal hydrogen-nitrogen ratio. However, this causes nitrogen to accumulate and the ratio of hydrogen to nitrogen is lower and lower. Therefore, the subsequent grade needs to be supplemented with hydrogen, and hydrogen can be directly supplemented, or gas with higher hydrogen nitrogen can be supplemented. For a certain level with insufficient space velocity, a corresponding amount of hydrogen-nitrogen mixture can be supplemented, and the space velocity and the production capacity are improved.

Thus, new experience is provided for designing open type synthetic ammonia equipment later, and better open type synthetic ammonia system is facilitated to be designed.

A, b, c, d in empirical formula 1 are constants determined by the synthesis column, catalyst, etc., and the operating pressure and temperature set for them, and the catalyst and temperature pressure vary from one synthesis column to another.

The first embodiment is as follows: table 1 is the case of an open ammonia synthesis system.

Fresh feed gas containing 1% of inert gas. Methane 0.7%, argon 0.3%. When the circulation method is adopted for production, the ammonia content of the gas discharged from the tower is 15.65 percent and the temperature is raised by 226 ℃ in 300 days per m under the conditions that the space velocity is 32000, the pressure is 300amt, the ammonia content in the gas entering the tower is 2.5 percent and the inert gas is 16 percent, and the annual work time is 300 days³The catalyst produces 1 million tons of synthetic ammonia. And the same catalyst dosage value.

The empirical formula of the space velocity and the ammonia content of the gas discharged from the tower is as follows:

y＝(0.299x³-0.195x²-0.176x+0.223)×(1.185/0.865)×((1+y'-r)/(1+y'+r))

R2＝0.997

the experimental formula is used for each stage of the open type synthetic ammonia system. And is referred to as empirical formula 1.1

It is taught that when the air speed is as shown in the table, the first three stages are all over 50% of the circulation method when 40000 is selected as the first stage, and the first 48.85% of the first stage is liquid ammonia, because the gas entering the tower originally contains no ammonia, 3% of ammonia is not separated after the synthesis. The synthetic towers can only produce 35 ten thousand tons of synthetic ammonia after working for 300 days in a circulating method, and can produce 52 ten thousand tons of synthetic ammonia by being converted into an open type. The last stage does not use the common ammonia cooling, and uses the cooling with lower temperature or water absorption, so the ammonia in the tower gas is completely extracted. The remaining gas, i.e. off-gas, was only 3.86% of the total volume produced. The residual gas in the tenth stage contains 19.73% of inert gas, and is made into a second stage of 25.88%, if tail gas is used for treatment, the workload is much lighter than that of a circulating method.

TABLE 1

The equipment is basically the equipment used in the circulation method, and the temperature of the first stage is increased by 272 ℃ and is increased by 46 ℃ compared with the circulation method. Additional water cooling is required. Total volume of tower gas 1220145Nm³Total volume of residual gas 1012417Nm³The increase in/h is only small compared to the same recycle method, so the ammonia cooling needs to be increased only a little.

The first six stages synthesize nearly 80% of gas into ammonia, and if the number of stages is too many, the last five stages can be cancelled, and a catalyst 6m is used³The synthesis column of (2) is replaced by a recycle method. As shown in fig. 2.2. (example one. two)

If the open type is produced according to the space velocity of 32000 of the original circulation method, the ammonia cooling is smaller than that of the circulation method, the rest is remained, the yield is further increased along with the increase of the space velocity, the ammonia cooling is also increased, and the ammonia cooling equipment is required to reach the space velocity of 37000 and is equal to the circulation method. Here, the space velocity 40000 was chosen such that only a small increase in ammonia cooling equipment was required to increase the yield by 45%.

The empirical formulas for different space velocities of the synthesis column and ammonia content of the effluent gas and the constants a, b, c and d thereof are different and must be determined individually.

Such as: according to inorganic chemical materials of the institute of eastern science and technology of small synthetic ammonia works and design handbooks, the relationship between the airspeed and the production intensity of ammonia content is as follows:

space velocity m³(mark)/h m³Catalyst 1000020000300004000050000

Outlet ammonia content% 21.719.0217.3316.0715.00

Production strength kgNH3/m3h 13502417337041604920

30.4mPa H2, N2 is 3, no inert gas and no imported ammonia react isothermally at 500 ℃.

The empirical formula thus calculated is:

y＝(-0.66x³+0.86x²-0.4772x+0.2567)

y is the ammonia content of the tower gas. x is one hundred thousand of the space velocity.

Any inert gas r and ammonia y' entering the column:

y＝(-0.66x³+0.86x²-0.4772x+0.2567)×((1+y'-r)/(1+y'+r)

empirical formula 1.2 where R2 is 0.999

The actual circulation space velocity is likely to be 20000, the annual production is 300 days, and the annual production is 5524.2 tons. The former stages were simulated with 25000 space velocity open production, 12 stages. The total amount of 38.7695 cubic catalysts is produced for 300 days per year, and 32.803 million tons of ammonia are obtained. Compared with the circulation method, the yield is increased by 53.16%, and the yield of the first three stages is increased by more than 60%.

The open ammonia synthesis system is different from one another by using different equipment and organizations, and various data are different from one another and are not uniform.

Example two: FIG. 3 is an array open ammonia synthesis system. Empirical formula 1.1 is the same as the example above. The table is calculated.

In total 35 ten thousand tons of synthesis tower, and one 5000 tons of synthesis tower is added. The annual output is 52 ten thousand tons, and the yield of each stage of the synthetic tower is increased almost. The circulation method for disassembling each synthesis tower can only produce 35.5 ten thousand tons, and the yield is increased by 45%.

The parallel connection needs to take the pressure balance of different synthesis towers in the same stage into consideration, and the resistance of each tower is approximately equal, which causes uneven work and comfort.

The pressure of each stage of the open type ammonia synthesis is not limited by other stages and can be different. The residual gas from the previous stage can be recompressed and then sent to the next stage for continuous production, or can not be recompressed. The degree of pressurization may also vary during pressurization.

In the practical use of the invention, a compressor and an oil remover can be completely omitted according to the situation, and all-stage synthesis towers are used for pressure-reducing full-closed production. The fresh gas is compressed and then enters a first-stage pressure inlet system, sequentially passes through synthesis, cooling and separation, then enters a synthesis tower, is cooled again, is separated again, and then enters the synthesis tower and … …, so that the final-stage tail gas comes out, and most of the gas is synthesized into ammonia without any mechanical movement in the middle.

Not only is a recompressor eliminated together with an oil separator and corresponding electric power, but also the pressure applied to the fresh air is fully utilized step by step, so that the low pressure is not necessary to save the compression energy. The system resistance is for this reason not too high. The elimination of equipment and piping also reduces the drag of the system. The pressure resistance of the synthesis column and other equipment in the subsequent stage can be reduced.

In order to reduce the compression work, many ammonia synthesis plants now compete for low pressure, low space velocity. For the open type, it is not necessary, medium pressure is more suitable, although the pressure increased at first is larger, but is never wasted, but is used in production. Recompression is eliminated, which is a savings.

For the compression-free pressure-reduction full-closed production, the resistance of each device and pipeline is required to be reduced as much as possible so as to prevent the final pressure reduction from being too large and not enough for production.

Example three: table 2 is a schematic of a compression-free fully enclosed production. See fig. 4.

The space velocity of 36000 is adopted, and the total amount of catalyst used in the synthesis tower is 103.66m³300 days of work and 135 ten thousand tons of annual output. The yield of the product is increased by 29 percent compared with a circulation method airspeed 32000. The last inert gas is 12.35 percent.

The yield increase is mainly in the first several stages. The table shows that the actual production increase is much greater than the actual production increase with the 300 atmosphere recycle method. The tail gas is large in volume and contains 3% of ammonia. Must be reused. The production can be continued by transferring the pressurization into a circulation method.

Since this is a production at low pressure, the requirements on the pressure resistance of the apparatus are reduced. The shell can be thinned step by step, the last stage is thinned greatly, and the airspeed at the rear stage can be reduced so as to improve the synthesis amount, reduce tail gas and avoid transferring to the production by a circulation method.

TABLE 2

Example four: FIG. 5 is a diagram of a ten-thousand-ton small synthesis tower array and a compression-free pressure-decreasing totally-enclosed production, in which almost all methane, most argon and part of nitrogen are removed by deep cooling of tail gas, and the obtained hydrogen, nitrogen, inert gas and most of the removed gas are used for supplementing a sixth stage and an eighth stage to solve the problem of hydrogen-nitrogen ratio, and the fourth stage is supplemented with hydrogen, and part of the hydrogen is converted from methane separated by deep cooling. The table is omitted.

If the tail gas outlet of the synthetic tower produced by the circulation method is connected with an open ammonia synthesis system consisting of a plurality of small synthetic towers, the tail gas amount is increased, and then the steps are carried out, so that the inert gas amount of the front large synthetic tower can be greatly reduced, the yield is greatly improved, and the yield of the rear small synthetic tower is increased compared with that of the circulation method.

Example five: see Table 3

The method is characterized in that the synthesis tower is produced at 300 atmospheres according to a circulation method, the empirical formula is the same as that of the first embodiment, 2.5 percent of ammonia enters the tower, 16 percent of inert gas, 32000 space velocity and 30 ten thousand tons of synthetic ammonia are produced annually, tail gas is led into an open type synthetic ammonia system consisting of six small synthesis towers to continue production according to a compression-free pressure reduction method, the small synthesis towers add 9 ten thousand tons, the tail gas of the large synthesis tower is increased, the tail gas of the large synthesis tower is cooled and separated from residual gas of ammonia, and the residual gas is divided into eight parts and fed into the open type small synthesis tower system. Returning seven-eighths of the tower to the original tower, and additionally adding fresh gas to the total volume of 1080000N m³The results are surprisingly good,/h, space velocity 36000.

The ammonia entering the large synthesis tower is only 1.87 percent, the inert gas is only 3.01 percent, the ammonia is 3.50 percent and 3.41 percent lower than those entering the tower by the Brownian method, the ammonia discharged from the tower is 19.15 percent, the net ammonia value is 17.28 percent, the production is carried out for 300 days every year which is close to 17.55 percent by the Brownian method, 42 ten thousand tons of synthetic ammonia are obtained, and the production is increased by 38.56 percent compared with the original circulation method. Fresh gas hydrogen to nitrogen ratio 2.96, the column produced at a hydrogen to nitrogen ratio of 2.877.

Six small synthesis towers are produced by a pressure reduction compression-free method, the pressure of each stage is reduced by 20 atmospheric pressures, the first stage inlet and the hydrogen-nitrogen ratio of 2.8257 are used for producing 10.6 ten thousand tons of synthetic ammonia in total, and 52.6 ten thousand tons of synthetic ammonia are produced in total by a large synthesis tower.

5.2% of tail gas, if most of inert gas and part of nitrogen are removed, the tail gas is supplemented to the next stages, the hydrogen-nitrogen ratio is improved, and the yield can also be improved.

The small tower with 9 ten thousand tons supports 22.6 ten thousand tons of output, and the big tower is not transformed by injured tendons and bones and basically keeps the original shape. The recycle compressor only needs to be increased by 4%.

TABLE 3

The open synthetic ammonia can be produced without compression and pressure reduction, and can also be produced with pressure increasing, when the content of the inert gas is low, the synthesis gas is produced under low pressure, and when the content of the inert gas is low, the inert gas is increased, and the pressure is increased, so that the synthesis rate is improved, and the compression work is further reduced without reducing the synthesis rate. Increasing followed by decreasing is also possible.

Example six: see table 4:

TABLE 4

At first, two Brownian synthesis towers are used, one thousand five hundred tons is produced per day, one thousand one ton is produced per day, the Brownian synthesis towers are generally produced under the conditions that inert gas is 3.41%, ammonia entering the towers is 3.50%, ammonia discharged from the towers is 21.00%, but the content of the inert gas is lower than that of raw material gas although air separation and cryogenic treatment are not carried out, and the yield is slightly increased than that of the raw material gas which is 0.25% of that of the raw material gas under the same 15 MPa. The ammonia content of the residual gas is too high, which is determined by its cooling separation equipment, where its separation equipment is used as it is. The third stage of the TopuSo synthetic tower increases the production slightly, and the cooling and separating equipment thereof naturally ensures that the ammonia content of the residual gas reaches 5.00 percent. The kellogg synthesis plant is particularly advantageous in that its inefficiency is due to the high inert gas, which is particularly true for the open format. The separation apparatus was cooled and the ammonia content of the remaining gas was calculated to be 3.001%. The pressure was still going to be raised and kellogg was done as a result, only ten stages, the inerts raised to 26.02% and the tail gas amount was 3.84% of the incoming fresh gas. The ninth stage inert gas exceeds 14.006% of the kellogg cycle method.

Due to the lack of data, no empirical curve could be made. Only one point can be made according to the airspeed at which the data is looked up. The actual space velocity is not known.

The structural properties of the synthesis column, including temperature, pressure and catalyst, are the same as those of the type currently being produced by the recycle process, as are the cooling separation units, except that the ammonia content and the inert gas content of the feed gas to the column are different. The Kalloger column refers to a column having the same empirical formula as Kelloger at the same pressure and temperature regardless of the size.

Total daily output 4968T/d. It can be seen that at a pressure of 150MPa, more than 50% of ammonia has been synthesized by the Brownian method, the Toeplol pressure of 18MPa is increased to more than 65%, and only 35% is done at Kalloger 20 MPa. Thus the pressure work is greatly saved. Although related to the advancement of these plants, this can be achieved without the use of air separation and cryogenic production of feed gas from liquid nitrogen.

The second stage cannot fully utilize the production capacity, the airspeeds of other stages can be increased, and the yield increase is inevitably also greatly increased as long as the airspeeds are increased.

The above examples show that the practical use of open-loop ammonia synthesis can be varied widely and independently. Each can be varied according to the open spirit and capital equipment at hand, without being bound.

Generally, the yield of the device constructed by the method can be improved by more than 30% and more than 40% by using the same amount of equipment, and in turn, the yield can be saved by a considerable synthesis tower and other equipment. The totally-enclosed production of pressure reduction without recompression has the advantages of less yield increase of the synthetic tower, more electricity consumption saving, and no lower benefit than equal pressure type considering that the following grade can use low-pressure resistant equipment. The specific number is determined by the arrangement and organization.

In order to further increase the yield and reduce the cost, the synthetic ammonia industry needs to build a large amount of plants quickly and greatly reduce the equipment price. The manufacturing of the synthetic ammonia equipment should go on the road of standardization, serialization, universalization and mass production. As in ford manufacturing automobiles. So that the price drops to only a fraction.

Large synthesis columns and other plants cannot be pursued blindly for this purpose, because of their long manufacturing period. Of course, it is not as small as possible. And the most suitable size of the equipment such as the synthesis tower should be found. The criteria for selection were: a certain synthesis tower is mature, the manufacturing period can be shortened, and the synthesis tower is suitable for greatly reducing the cost, and is easy to transport and install. The open synthetic ammonia is small and large, and the yield of the built synthetic ammonia plant is not small.

The equipment is produced in large scale, the price is greatly reduced, the capital profit rate of the built synthetic ammonia plant is improved, and the depreciation of fixed assets can be greatly reduced. Not only the synthesis section, but also other gases such as gas making and refined gas can greatly reduce the cost. In terms of gas making, a plurality of sets of equipment are combined for a long time, a plurality of gas making furnaces form a group, the gas making furnaces run in parallel, blast air alternately, queue and blow air, and the gas making furnaces are combined into a large gas making furnace. The equipment can be easily mass-produced. This should also be the case for refinery gases.

The construction period of the factory is long, which is equivalent to a large amount of fund overstocking. It should be realized that the synthetic ammonia plant only needs a few months from decision making to earth-breaking and moving to the construction and production. The investment is quickly recovered after the construction. And then is clear.

It is necessary to establish a plant for mass production of synthetic ammonia, and to integrate the production of equipment, construction of a synthetic ammonia plant, production of synthetic ammonia, and the like. The method has the advantages that decision making is unified, manufacturing is not needed, when products (equipment) are manufactured in a tightening mode on a production line, a professional synthetic ammonia equipment installation construction team exists, the workers can be tightened to break earth after receiving tasks, the equipment can be loaded on the production line, the construction site can just arrive at the equipment installation stage, no extra-large transport tool is needed to be transported away, the products can be transported to the construction site quickly, the installation is carried out quickly, the whole process is opened quickly, and accordingly professionals can check, check up the products to be qualified, try on the machine quickly and put into production quickly.

Even professional teams for equipment maintenance and catalyst replacement are established to serve each synthetic ammonia plant, so that corresponding time is greatly shortened, the operating rate is increased, the production time is prolonged, and the annual yield is increased again.

Claims

1. The open synthetic ammonia system is characterized in that after the hydrogen-nitrogen synthetic ammonia in the synthetic tower is discharged from the tower, the residual gas of the liquid ammonia is separated through cooling, and the residual gas is sent to other synthetic towers for continuous synthesis if the residual gas needs to be continuously synthesized.

2. The open type ammonia synthesis system according to claim 1, wherein a plurality of synthesis towers are connected in series to form a multi-stage system, the multi-stage system is a two-stage synthesis tower and more than two stages, the synthesis tower which is not provided with other synthesis tower residual gas at the forefront is the first stage, the adjacent stages are respectively called as the front stage and the rear stage, and the multi-stage system comprises at least two stages.

3. The open ammonia synthesis system of claim 2, wherein the gas entering the synthesis columns is any gas mainly containing hydrogen and nitrogen, wherein the gas entering the first stage of the synthesis columns is mainly fresh raw gas of methane, argon, helium and other inert gases which are not concentrated yet, and the gas entering the other stages of the synthesis columns is mainly from the rest gas of the other synthesis columns.

4. The open ammonia synthesis system of claim 3, wherein the transport path for the residual gas is from the front stage to the rear stage, except for an open ammonia synthesis system having only two stages, a first stage having no residual gas input, when having a size great difference with the second stage, and a last stage having no rear stage, allowing the input of the residual gas to establish the loop production.

5. The open ammonia synthesis system of claim 2, wherein the same stage comprises at least two synthesis towers connected in parallel, and the capacity of the synthesis tower of the stage is the sum of the capacities of the synthesis towers connected in parallel.

6. The open type ammonia synthesis system of claim 5, wherein from the first stage to the last stage, the capacity of each stage of the synthesis tower is gradually reduced along with the synthesis and cooling separation of the hydrogen and nitrogen gas to separate the liquid ammonia, the volume of the gas entering and exiting is smaller, the accumulated amount of the inert gas is gradually increased, the number of the later stages is larger than that of the former stage, until most of the hydrogen and nitrogen gas is synthesized and separated as the liquid ammonia, when the amount of the inert gas in the residual gas is insufficient to continue the production of the synthetic ammonia, the residual gas is discharged as the tail gas in one step, and the last stage establishes a loop to circulate the synthesis tower, and the capacity of the synthesis tower is not limited by the capacity.

7. The open ammonia synthesis system of claim 6, wherein the same stage must be operated at the same pressure, different stages are not constrained, and the stages are at the same or different pressures and need to be recompressed or uncompressed.

8. The open ammonia synthesis system of claim 7, wherein the residual gas from each stage of the synthesis tower is not compressed, and is a compression-free fully closed pressure-reduced open ammonia synthesis system, and the fresh gas is pressurized into the system, and then sequentially enters each stage of the synthesis tower, and is subjected to synthesis, cooling, separation, resynthesis, recooling, separation, resynthesis, … … and finally reaches the last stage of discharge system.

9. The open ammonia synthesis system of claim 7, further characterized in that the open ammonia synthesis system is an open ammonia synthesis system in which the pressure of each stage of the synthesis tower increases from low pressure to high pressure from the first stage to the last stage, or an open ammonia synthesis system in which the pressure of each stage of the synthesis tower increases and then decreases.