CN102389689B

CN102389689B - Powerless low-temperature isobaric ammonia recovering method and isobaric ammonia recovering device

Info

Publication number: CN102389689B
Application number: CN 201110302728
Authority: CN
Inventors: 刘军
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-10-09
Filing date: 2011-10-09
Publication date: 2013-07-17
Anticipated expiration: 2031-10-09
Also published as: CN102389689A

Abstract

The invention relates to an ammonia recovering process and ammonia recovering equipment, namely a method and a device for recovering ammonia from gas from ammonia production plants at a low temperature and isobaric pressure. Several or all coolers of the isobaric ammonia recovering device cool ammonia water and absorb water used by ammonia by using liquid ammonia of which the temperature is lower than that of cooling water. The coolers include a double-travel internal cooler in a bubbling absorber, a coil tube type cooler, an out-tower ammonia water cooler, a demineralized water cooler, a first out-tower small ammonia water cooler, a second out-tower small ammonia water cooler. In the invention, ammonia water is cooled without using cooling water, and power is saved; the cooling area of the out-tower ammonia water coolers and the cooling area of the coolers on all layers of tower plates increase gradually from top down and are allocated according to different ammonia absorbing capacities and different dissolution heat released on all layers of tower plates and the cooler loads on the coolers on the layers of tower plates; and thus, the required cooling area is guaranteed and does not wasted, and the ammonia absorbing capacities on all layers of tower plates are fully played.

Description

The isobaric ammonia recovery method of a kind of unpowered low temperature and isobaric ammonia recovery unit

Technical field

The present invention relates to a kind of ammonia reclaiming process and equipment, i.e. the isobaric ammonia recovery method of the unpowered low temperature of synthesis ammonia plant off-gas and isobaric ammonia recovery unit.

Background technology

In prior art, aspect the technology of isobaric ammonia recovery, various coolers in the tower of various isobaric ammonia recovery towers, outside the tower all are to cool off ammoniacal liquor with the recirculated cooling water of normal temperature or with the lower phreatic water of temperature, consumption of power is wanted in the cold water of recirculated cooling water and circulation, conveying, and consumption of power is also wanted in the extraction of phreatic water and conveying.Absorbing ammonia will be with soft water or demineralized water, and preparation soft water or demineralized water need consumption of power, is sent to isobaric ammonia and reclaims cat head and soft water or demineralized water added with pump again, also wants consumption of power, and the ammoniacal liquor that is discharged to ammonia vessel also wants consumption of power to send.Be that present isobaric ammonia is recovered in and absorbs the process that ammonia prepares ammoniacal liquor and want consumption of power.

The ammonia concn of isobaric ammonia recovery tower preparation is low, concentration low below 12% (weight), higher generally about 18% (weight).The ammoniacal liquor of producing the synthesis ammonia plant recovery of urea substantially all goes to desorption system and the depth hydrolysis system of urea plant, with ammonia distillation, concentrate, ammoniacal liquor after the concentrate goes low pressure ammonia absorption system to absorb ammonia again with the gas ammonia that contains steam, the low-pressure steam consumption of desorb and depth hydrolysis's high steam consumption have been increased, also increased power consumption, increased the power consumption of low pressure ammonia absorption cooling water again, also increased the load that low pressure absorbs, the ammoniacal liquor that distillation, concentrate, recovery, the isobaric ammonia of utilization reclaim also will consume a large amount of steam and power.

Ammonia content is lower in some isobaric ammonia recovery towers outlet tail gas, but is higher than pressure swing adsorption method and membrane separation process recover hydrogen to the requirement of air inlet ammonia content.Hydrogen in the recovering discharging gas, also tail gas to be removed the clean ammonia of ammonia-cleaning tower, absorb ammonia in the off-gas tail gas again with more soft water or demineralized water, further reduce the ammonia content in the off-gas tail gas, want the weak aqua ammonia more than the delivery ratio ammoniacal liquor, these very rare ammoniacal liquor also will go the distillation of urea desorption system and depth hydrolysis system, concentrate, distillation, concentrate, reclaim, utilize these weak aqua ammonias also will consume steam and power.

Though the isobaric ammonia of ammonia has reclaimed ammonia in the recovering discharging gas, but the ammoniacal liquor that reclaims can not be directly used in production, very rare weak aqua ammonia that ammonia-cleaning tower is discharged more can not for the production of, consume a large amount of steam and electricity, with reclaiming, utilize after the distillation of ammoniacal liquor and weak aqua ammonia, the concentrate, produce a large amount of desorb waste water that contains small amount of residual ammonia, increased the weight of environmental protection pressure, increase energy consumption, improved production cost, reduced the economic benefit that ammonia reclaims.

It also is to discharge a kind of method that gas ammonia reclaims that present unpowered ammonia reclaims.Unpowered ammonia reclaims ammonia content height in the outlet tail gas, and generally about 1.2% (volume), the rate of recovery of ammonia is low, and its technical indicator is with to belong to the traditional isobaric ammonia recovery tower that is eliminated suitable.Unpowered ammonia reclaims the power consumption that has increased the freezing process ammonia compressor, has also increased the power consumption of cooling water, and the hydrogen that reclaims tail gas also will remove the clean ammonia of ammonia-cleaning tower, also will increase power consumption, has produced weak aqua ammonia again.So-called unpowered ammonia reclaims, and actual is consumption of power, just in ammonia recovery process not consumption of power or few consumption of power, and moves on to the freezing process consumption of power.

As seen, present isobaric ammonia is recovered in the preparation of soft water or demineralized water and conveying, pressurization, in the cooling procedure that absorbs ammonia, conveying, distillation, the concentrate of the weak aqua ammonia of discharging at the ammoniacal liquor that reclaims and clean ammonia, reclaim, utilize process, consumption of power is all wanted in whole ammonia recovering process, and especially distillation, the concentrate process energy consumption at ammoniacal liquor, weak aqua ammonia is higher.

Present isobaric ammonia reclaims entrance off-gas ammonia content about 50% (volume), and the ammonia that off-gas is brought into from the liquefied ammonia storage tank is a lot, and the ammoniacal liquor of generation is also just a lot, and is very unfavorable to producing.If the off-gas ammonia content is being dropped to about 20% (volume) before the isobaric ammonia recovery system with my other new technology, the ammonia amount that off-gas is brought into will reduce to 1/4th, this is very favourable to producing, but at normal temperature or a little more than under the normal temperature, the vapour pressure of 45% (weight) ammoniacal liquor ammonia reaches even surpasses the dividing potential drop contain ammonia 20% (volume) off-gas ammonia under the 2.2PMa stagnation pressure, ammonia concn can not brought up to about 45% (weight) again under these process conditions, absorb ammonia at normal temperatures, influenced recovery, utilized the improvement of ammoniacal liquor mode.

Present isobaric ammonia reclaims all uses water quench ammoniacal liquor, absorbs ammonia at normal temperature or a little more than under the normal temperature, because the ammonia concn of preparation is low, at normal temperature or a little more than under the normal temperature, the steam of low concentration ammoniacal liquor ammonia forces down, and ammonia temperature is little to the influence that absorbs ammonia; But during the high concentration ammoniacal liquor about preparation 45% (weight), ammonia temperature is but very big to the influence that absorbs ammonia, absorb ammonia at low temperatures, the steam of ammonia forces down in the ammoniacal liquor, the motive force that absorbs ammonia is big, absorb ammonia at low temperatures, can prepare than at normal temperature or a little more than absorbing the higher ammoniacal liquor of ammonia concentration under the normal temperature, the ammonia content in the tail gas is also lower.

It is many at present to bring the ammonia that isobaric ammonia reclaims into by off-gas, and ammonia concn is very low, cause the ammonia vol for preparing big thus, total water yield is also many, the concentration of these ammoniacal liquor is again far below the ammonia content of a first liquid, the not high ammoniacal liquor of concentration that has a lot of water can't be joined one of urea and inhale tower, can only go to reclaim again, utilize after the desorption system of urea and the distillation of depth hydrolysis system, the concentrate, consume a large amount of steam and power.

The present isobaric ammonia recovery unit number of plates is few, and the progression that absorbs ammonia is few, and degree of purification and ammonia recovery are not high, and the ammonia concn of recovery is not high.

The ammonia recovering effect is tower preferably, and what installed on the top in the cylindrical shell of top is the column plate of no cooler, mainly plays the adiabatic clean ammonia effect that absorbs ammonia.Because the column plate number of plies in the unit height cylindrical shell is few, is subjected to the restriction of cylindrical shell height, the number of plates of no cooler is few, and clean ammonia is not thorough.Adopt the mode of the clean ammonia of no cooler column plate, influence and limited clean ammonia effect;

When reclaiming the hydrogen of outlet tail gas, the tail gas of outlet also will remove the clean ammonia of ammonia-cleaning tower again, add soft water or demineralized water again, discharges (rare) ammoniacal liquor again.The technology that the clean ammonia of secondary, secondary add water, secondary discharge (rare) ammoniacal liquor is unreasonable, has not only consumed demineralized water more, discharges weak aqua ammonia again;

The area of cooler is not that what, what, the height of cooling load of emitting the heat of solution of ammonia that absorbs the ammonia amount by it on each layer column plate distributes on each layer column plate, it is very unreasonable that film-cooled heat distributes, influence the performance of each column plate absorbability, also influence the ammonia recovering effect.

In prior art, the technology that isobaric ammonia reclaims has the following disadvantages:

1, present isobaric ammonia recovery tower will be used in the water quench tower or the outer ammoniacal liquor of tower, consumption of power;

2, the ammoniacal liquor that isobaric ammonia recovery tower is interior with the water quench tower or tower is outer, because the temperature of cooling water is higher relatively, the ammonia temperature in the isobaric ammonia recovery tower will be higher.Absorb ammonia under higher temperature, to further raising ammonia concn, ammonia content is unfavorable in the reduction tail gas;

3, absorbing ammonia will want the consumption of power preparation, carry, and it is added in the tower with soft water or demineralized water;

4, it is also higher relatively to absorb the temperature of soft water that ammonia uses or demineralized water, the effect of influence washing ammonia, clean ammonia, and ammonia content is higher in the tail gas;

5, the ammonia concn that reclaims of isobaric ammonia recovery tower is low, and ammonia vol is big, and total water yield is big, and ammoniacal liquor can only go to reclaim, utilize after the desorption system of urea and the distillation of depth hydrolysis system, the concentrate, consume a large amount of steam and electricity, and these all want consumption of power;

6, unpowered ammonia reclaims the power consumption that has increased the freezing process ammonia compressor, and unpowered ammonia reclaims also will consume a large amount of power in fact.

7, ammonia content is higher in the isobaric ammonia recovery tower outlet tail gas of unpowered ammonia recovery and the overwhelming majority, and tail gas dehydrogenation gas also will remove clean ammonia before reclaiming, and also will consume steam and electricity, also wants consumption of power;

8, the number of plates of isobaric ammonia recovery tower is few, and absorbability is low, and the ammonia recovering effect is poor, and the ammonia concn of preparation is low, and the outlet ammonia content is higher;

What 9, installed on the top in the cylindrical shell of top is the column plate of no cooler, adopts the mode of the clean ammonia of no cooler column plate, influences and has limited clean ammonia effect;

10, the clean ammonia of secondary, secondary add water, secondary to discharge the technology of (rare) ammoniacal liquor unreasonable;

11, the area of cooler is not that what, what, the height of cooling load of emitting the heat of solution of ammonia that absorbs the ammonia amount by it on each layer column plate distributes on each layer column plate, and it is very unreasonable that film-cooled heat distributes, and influences the performance of each column plate absorbability;

12, absorb the process conditions of ammonia at present, the number of plates, the area distributions of cooler on each layer column plate, absorb the form of ammonia, the performance of ammonia recovery tower etc., after all being not suitable for dropping to entrance off-gas ammonia content about 20% (volume) with my other new technology, the ammonia concn that reclaims is brought up to about 45% (weight) about by 15% (weight), be original 1/17th absorbing that the water yield that ammonia uses reduces to, to absorbing under the very disadvantageous condition of ammonia, the ammonia content that will export tail gas again drops to the following leap of 0.0020% (volume) about by 0.5% (volume), can't realize the breakthrough that the isobaric ammonia of unpowered low temperature reclaims.

In prior art, aspect the device structure of isobaric ammonia recovery, isobaric ammonia recovery tower has various ways: one section isobaric ammonia recovery tower outlet ammonia content height that absorbs ammonia, generally more than 1% (volume), the ammonia concn of preparation is low, generally below 12% (weight), belong to the ammonia reclaimer that falls behind, is eliminated.The ammonia concn of the isobaric ammonia recovery tower preparation that effect is quite a lot of is generally about 18% (weight), concentration far below high concentration ammoniacal liquor, tower outlet off-gas tail gas ammonia content is relatively low, and generally about 0.2% (volume), tail gas will absorb ammonia through water again just can go recover hydrogen.

The bottom cylindrical shell of the isobaric ammonia recovery tower that effect is quite a lot of is thick, and diameter is at φ 1600～φ 1800, and the bottom cylindrical shell is equipped with several bigger cooling water tanks; The top barrel diameter is slightly thin, and diameter is also at φ 1000～φ 1400, and the top cylindrical shell is equipped with 8 layers to 18 layers column plate, and the performance of isobaric ammonia recovery tower is not high.The top cylindrical shell that φ about 1000 is thinner, column plate in middle part and bottom is equipped with serpentine (trombone) cooler, and top is the column plate of no cooler, φ about 1400 thicker top cylindrical shells, several little cooling water tanks are respectively arranged on the column plate of middle part and bottom, and top is the column plate of no cooler; The adiabatic clean ammonia effect that absorbs ammonia is mainly played on the top of top cylindrical shell, and not only barrel diameter is thick, and under same clean ammonia effect, the cylindrical shell height is also high, has increased weight of equipment and cost; Because the tower diameter of top cylindrical shell is thick, under the operating pressure of 1.5MPa or 2.1MPa, the off-gas flow velocity that flow is very low is extremely low, and the flow velocity of ammoniacal liquor is also very low, and the off-gas in the tower and ammoniacal liquor is bias current easily all, and influence absorbs the effect of ammonia.No matter be serpentine (trombone) cooler, still little cooling water tank can't be arranged bigger film-cooled heat in the lower very limited height between column plate, also be difficult to adjust flexibly or change the film-cooled heat of cooler on each column plate; The total film-cooled heat of one section cooling water tank is big at the bottom of the tower, and the film-cooled heat on each layer of the cylindrical shell column plate of top is very little, the total film-cooled heat of one section cooling water tank is about 10 times of film-cooled heat on each individual layer column plate of top cylindrical shell at the bottom of the tower, one section film-cooled heat with top adjacent tray differs very big at the bottom of the tower, and the film-cooled heat of top each layer of cylindrical shell column plate is all identical, cooler area distributions on each layer column plate can't be become from top to bottom increases gradually, it is unreasonable that each layer column plate film-cooled heat distributes, the film-cooled heat deficiency of some column plate, be unfavorable for bringing into play the effect of these column plates, the effect of ammonia is reclaimed in influence, and also influence improves the concentration and the ammonia content that reduces tail gas of ammoniacal liquor.

Employing cooling water tank or little cooling water tank have increased the diameter of equipment barrel artificially, have increased the wall thickness of cylindrical shell; At cylindrical shell the cooling water tank wide-bore is installed and is wanted reinforcement, cylindrical shell generally also will be thickeied, and has increased weight of equipment; The epimere of isobaric ammonia recovery tower adopts tower plate structure to wash ammonia, clean ammonia, and it is too thick that barrel diameter seems, some waste material has increased weight of equipment, has also increased equipment manufacturing cost; The part that cooling water tank and little cooling water tank stretch out cylindrical shell is the cooling dead angle substantially, has wasted film-cooled heat, has consumed material more.More than these have all increased weight of equipment and cost;

Preparation 45% (weight) high concentration ammoniacal liquor, and will export the tail gas ammonia content and drop to below 0.002% (volume), need tens of numbers of plates of increase, if isobaric ammonia recovery tower all adopts tower plate structure to absorb ammonia, the height of cylindrical shell can be higher, and equipment can be heavier, and cost will be higher also.

In prior art, isobaric ammonia recovery tower has the following disadvantages aspect device structure:

1, the cooling water tank that stretches out cylindrical shell is the cooling dead angle, and the utilization rate of film-cooled heat is low;

2, because the tower diameter of top cylindrical shell is thick, the off-gas in the tower and ammoniacal liquor is bias current easily all, and influence absorbs the effect of ammonia.

3, between column plate in the lower very limited height, the serpentine (trombone) cooler that can arrange or the film-cooled heat of little cooling water tank are little, and also the cooler on each layer column plate can't being distributed into from top to bottom, film-cooled heat increases gradually;

4, adopt serpentine (trombone) cooler or little cooling water tank in the cylindrical shell of top, artificially overstriking cylindrical shell, increased weight of equipment and cost;

What 5, installed on the top in the cylindrical shell of top is the column plate of no cooler, and not only barrel diameter is thick, and under same clean ammonia effect, the cylindrical shell height is also high, has increased weight of equipment and cost;

6, the total film-cooled heat of one section cooling water tank is big at the bottom of the tower, and the film-cooled heat on each layer of the cylindrical shell column plate of top is very little, the film-cooled heat of the top cylindrical shell bottom tray that a section is adjacent at the bottom of the tower differs about 10, it is very greatly different that the film-cooled heat of adjacent segment differs, and the film-cooled heat of top each layer column plate is all identical again, it is unreasonable that each layer column plate film-cooled heat distributes, and the film-cooled heat deficiency of some column plate is unfavorable for bringing into play the effect of these column plates;

7, only one section absorption ammonia of weak effect, eight layers to the 18 layers column plate that effect is quite a lot of, the number of plates is few, and the performance that absorbs ammonia is not high, so the ammonia concn of preparation is low, ammonia content height in the tail gas;

8, the quite a lot of isobaric ammonia recovery tower of effect all adopts tower plate structure, adopts cooling water tank or serpentine (trombone) cooler, and device diameters is thick, the wall thickness of cylindrical shell, and equipment is heavy, the cost height;

9, preparation 45% (weight) high concentration ammoniacal liquor, and will export the tail gas ammonia content and drop to below 0.002% (volume), if all adopt tower plate structure absorption ammonia, the height of cylindrical shell can be very high, and equipment can be very heavy, and cost also can be higher, and is namely unreasonable, also uneconomical.

Summary of the invention

One of purpose of the present invention is provide at above-mentioned deficiency a kind of with low-temperature liquid ammonia and cold liquefied ammonia cooling ammoniacal liquor, absorb ammonia, the isobaric ammonia recovery method of the better unpowered low temperature of ammonia recovering effect at low temperatures.

Two of purpose of the present invention is that a kind of ammonia concn that provides at above-mentioned deficiency is very high, extremely low, the better isobaric ammonia recovery unit of ammonia recovering effect of ammonia content in the tail gas.

Technical solution of the present invention is: the isobaric ammonia recovery method of a kind of unpowered low temperature is characterized in that several or whole cooler of isobaric ammonia recovery unit is lower than the liquefied ammonia cooling ammoniacal liquor of cooling water and absorbs the water that ammonia is used with temperature; Described cooler comprises the outer ammoniacal liquor cooler of round trip intercooler, coiled pipe cooler, tower, demineralized water cooler, the outer little ammoniacal liquor cooler of first tower and the outer little ammoniacal liquor cooler of second tower in the bubbling absorber.Isobaric ammonia recovery unit no longer adopts water quench, uses the cooling of low-temperature liquid ammonia and cold liquefied ammonia instead.

High concentration ammoniacal liquor, concentrated ammonia liquor, weak aqua ammonia, the isobaric ammonia recovery unit that isobaric ammonia is reclaimed with liquefied ammonia absorbs in several liquid such as water that ammonia uses one or more and is cooled to the temperature that temperature is lower than cooling water, absorbs ammonia being lower than under the cooling water temperature.

Have two layers of tower dividing plate and bubbling column plate that has cooler, gas distributor to Floor 12 in the bubbling absorber; Three meters to 12 meters of the structured packing total heights of the packing layer in the padding washing device on top more than a section or a section.Intersegmental weak aqua ammonia between two sections structured packings of padding washing device bottom removes outside cooler, returns next section packing layer after the cooling.

Before bubbling absorber off-gas entrance, be provided with circulation absorption and separation device, off-gas is introduced into circulation absorption and separation device, outside tower, absorb earlier ammonia, by ammoniacal liquor with and stream, reflux type absorb ammonia, the circulation that high concentration ammoniacal liquor does not need external power to absorb automatically, cool off, absorb between the ammoniacal liquor cooler outside circulation absorption and separation device and the tower that increases newly, external refrigeration adds inner cooling and absorbing ammonia.

Each round trip intercooler in the bubbling absorber of ammoniacal liquor cooler, the film-cooled heat of each coiled pipe cooler distribute by reducing gradually outside tower.

Increased the demineralized water cooler before or after the desalination water pump, with low-temperature liquid ammonia cooling and absorbing ammonia water; The desorb waste water of using urea instead absorbs ammonia.

A kind of isobaric ammonia recovery unit comprises isobaric ammonia recovery tower, and isobaric ammonia recovery tower is made up of the bubbling absorber of bottom, the padding washing device two parts on top.

The padding washing device comprises the cylindrical shell of band gas vent and water inlet, the cylindrical shell bottom has flange to be connected with the flange of bubbling absorber overhead, the cylindrical shell internal upper part is wire mesh demister, and liquid distribution trough is arranged below, is the packing layer more than a section or a section that structured packing is housed below the liquid distribution trough; Between two sections packing layers of first section packing layer and second section packing layer, be provided with liquid re-distributor;

Or below second section packing layer, be provided with band weak aqua ammonia first feeder, second liquid distribution trough that has an import of the rare water of ammonia and the 3rd section packing layer of once exporting, outside cylindrical shell, increase little ammoniacal liquor cooler outside first tower, and export once with weak aqua ammonia that an import is connected with the rare water of ammonia;

Or below the 3rd section packing layer, be provided with second feeder, the 3rd liquid distribution trough that has the import of weak aqua ammonia secondary and the 4th section packing layer of the outlet of band weak aqua ammonia secondary, outside cylindrical shell, increase little ammoniacal liquor cooler outside second tower, and an import is connected with the rare water of ammonia with the outlet of weak aqua ammonia secondary;

The bubbling absorber comprises cylindrical shell, and the top in the cylindrical shell is provided with the one or more layers bubbling column plate that has coiled pipe cooler, is provided with the tubular gas distributor between coiled pipe cooler and bubbling column plate; On bottom in the cylindrical shell or the following one or more layers of tower dividing plate round trip intercooler is installed, is provided with the multitube gas distributor below the round trip intercooler; No tower dividing plate below the round trip intercooler of bottom;

Every group of coiled pipe cooler is made up of one or above involute shape coil pipe, intake header, outlet header, inlet tube, outlet and a support fixation part etc., tubular gas distributor, bubbling column plate are arranged in its lower section, between bubbling column plate and cylindrical shell, be equipped with down-flow plate, in the centre of bubbling column plate riser, outer tube are installed, in its bottom baffling demister, discharge opeing liquid sealing pipe are installed.Intake header, outlet header, inlet tube, outlet are all in the same side of cylindrical shell;

Every group of round trip intercooler comprise liquid-collecting box, down liquid-collecting box, heat exchanger tube that quantity is a lot of, circle, annular gripper shoe, stretch out feed tube and the drain pipe of cylindrical shell both sides respectively, gas-liquid channel is all left at center at last liquid-collecting box, following liquid-collecting box, and also leaves bigger gas-liquid channel between the cylindrical shell; Between the inherent feed tube of last liquid-collecting box and the drain pipe dividing plate is arranged;

The film-cooled heat of each coiled pipe cooler, each round trip intercooler is all different, all from top to bottom increases gradually.

Before the bubbling absorber, be provided with circulation absorption and separation device, circulation absorption and separation device comprises cylindrical shell, circulation absorption and separation device top is provided with gas vent, liquid distribution trough, packing layer, concentrated ammonia liquor import, the middle part has porous plate, trunnion, collapsible tube, bottom that high strength ammonia water inlet, nozzle, the air jet pipe that has the hole, high strength ammonia water out, off-gas import, high concentration ammoniacal liquor outlet are arranged, and other has two interface of the level gauge; The import of concentration ammoniacal liquor, gas vent connect with the concentrated ammonia liquor outlet of bubbling absorber bottom and the off-gas import of bottom respectively, and high strength ammonia water out, high strength ammonia water inlet are connected with the high strength ammonia water entrance of the outer ammoniacal liquor cooler of tower respectively.

Padding washing device gas vent is connected with separator, and water inlet is connected with the desalination water pump; The theoretical cam curve sum of the column plate number of plies of bubbling absorber and the padding washing device that top increases newly, eight to 18 by the better tower of present ammonia recovering effect are increased to about 66, absorbability and the clean ammonia ability of isobaric ammonia recovery unit have been increased substantially, for the isobaric ammonia of unpowered low temperature reclaims the required condition of having created.

The isobaric ammonia recovery method of unpowered low temperature: will be no longer with the method with recirculated cooling water cooling ammoniacal liquor that generally adopts at present, adopt my other new technology, use from-6～0 ℃ of low-temperature liquid ammonias of ammonia recover and production surplus cold go to cool off ammoniacal liquor and the demineralized water of～15 ℃ of cold liquefied ammonia in the left and right sides;

-6～0 ℃ of low-temperature liquid ammonias from the ammonia recover are introduced into the outer ammoniacal liquor cooler cooling of tower high concentration ammoniacal liquor, most of low-temperature liquid ammonia removes each the round trip intercooler cooling concentrated ammonia liquor in the bubbling absorber afterwards, remove each coiled pipe cooler cooling ammoniacal liquor again, export out system by low-temperature liquid ammonia afterwards, remove other low temperature cool exchanger, or remove the liquefied ammonia storage tank; Another small part low-temperature liquid ammonia goes the low-temperature liquid ammonia outlet behind the removal brine cooler cooling and desalting water; The low-temperature liquid ammonia of round trip intercooler outlet also can remove the outer little ammoniacal liquor cooler of first tower and the outer little ammoniacal liquor cooler cooling weak aqua ammonia of second tower;

Cold liquefied ammonia from about 15 ℃ of ammonia recovers, remove outside first tower little ammoniacal liquor cooler cooling weak aqua ammonia outside the little ammoniacal liquor cooler and second tower through cold liquefied ammonia import, also can remove coiled pipe cooler cooling ammoniacal liquor, remove cool exchanger through cold liquefied ammonia outlet afterwards, or remove the liquefied ammonia storage tank; If low-temperature liquid ammonia is enough, then need not cold liquefied ammonia;

Replace recirculated cooling water with low-temperature liquid ammonia, cold liquefied ammonia, not only removed the heat of solution of ammonia, cooling ammoniacal liquor is consumption of power no longer, also reduced the temperature of ammoniacal liquor and demineralized water everywhere, absorb ammonia being lower than under the low temperature of cooling water temperature, changed the condition of traditional absorption ammonia, the latter is main purpose.

High strength ammonia coolant-temperature gage in the outer ammoniacal liquor cooler of tower is dropped to about 5 ℃, demineralized water in the demineralized water cooler is also dropped to about 5 ℃, by in the winter time about 20 ℃, about 40 ℃ of summer, absorb ammonia, change into and absorb ammonia throughout the year at low temperatures, thereby optimized acceptance condition greatly, improved assimilation effect significantly, can reach at normal temperature or a little more than absorbing technical indicator that ammonia is beyond one's reach and assimilation effect under the normal temperature.

The area of each cooler, be to absorb the amount of ammonia to each tower dividing plate, each bubbling column plate in minimizing gradually by ammoniacal liquor cooler outside tower, the heat of solution of emitting is also reducing gradually, the cooling load of each cooler also reduces gradually distributes, meet the actual condition that absorbs ammonia, can give full play to the effect of each absorption tray.

Isobaric ammonia recovery unit has increased absorption hop count and the absorption tray number of plies that has cooler, and film-cooled heat distributes rationally, has improved the absorbability of middle and high concentration range significantly.

With my other new technology, the ammonia recover with off-gas in ammonia content drop to about 20% (volume) about by 50% (volume), isobaric ammonia reclaims entrance off-gas gas ammonia amount and reduces to original 1/4th, the reaction heat that absorbs ammonia also reduces to original 1/4th, cooling load reduces significantly, and the water yield of adding and the ammonia vol of preparation all will reduce significantly; And at the ammonia recover temperature of off-gas also is reduced to-6～0 ℃ by traditional normal temperature or a little less than normal temperature, reduced the temperature that enters isobaric ammonia recovering discharging gas, alleviated the cooling load that isobaric ammonia reclaims again, these, not only created condition for the very limited surplus cold but ammoniacal liquor of production of top utilization, because the water yield that adds and the ammonia vol of preparation all reduce significantly, also for directly going one of urea to inhale tower, the ammoniacal liquor that isobaric ammonia is reclaimed created condition;

When entrance off-gas ammonia content drops to 20% (volume) left and right sides, be difficult to prepare 45% (weight) left and right sides high concentration ammoniacal liquor at normal temperatures, owing to absorb ammonia at low temperatures, and taked above measure again, still ammonia concn can be brought up to about 45% (weight), the high concentration ammoniacal liquor for preparation directly goes a suction tower to create condition again.

The ammonia concentration of 45% (weight) high concentration ammoniacal liquor has surpassed the concentration of urea diformazan liquefied ammonia, also surpasses the ammonia concentration of a first liquid.With my other new technology, drop to about 20% (volume) about by 50% (volume) the off-gas ammonia content of entrance after, it is original 1/4th that the water yield of adding reduces to, ammonia vol also significantly reduces; And after the concentration of ammoniacal liquor brings up to about 45% (weight) about by 15% (weight), it is original below 1/4th that the water yield that adds reduces to again, like this, the water yield that adds has reduced to original 1/17th, the water of being brought into a suction tower by ammoniacal liquor is considerably less, only account for about 0.32% of a first liquid measure, minimum to the steam/hydrocarbons ratio influence that urea is synthetic.The pressure of isobaric ammonia recovery tower is higher than the pressure of a suction tower, concentration is that the high concentration ammoniacal liquor about 45% (weight) can directly go one to inhale tower without pump, after first pump pressurization, go urea synthesizer to produce urea, ammoniacal liquor no longer goes the desorption system of urea and the distillation of depth hydrolysis system, concentrate, reclaims, utilizes isobaric ammonia to reclaim the ammoniacal liquor that produces and no longer consume a large amount of steam and power.

(or afterwards) increased the demineralized water cooler before the desalination water pump, by reducing the temperature of demineralized water, reaches and reduces the purpose that padding washing device top and middle part absorb temperature, makes the padding washing device also absorb ammonia under low temperature or lower temperature.

The theoretical cam curve of padding washing device is about 60, to absorb again about water cooling to 5 that ammonia uses ℃, improved in the padding washing device again, the absorbability on top, second section packing layer of padding washing device and the 3rd section weak aqua ammonia that packing layer falls can also be gone the outer little ammoniacal liquor cooler cooling of two towers respectively, return next section packing layer afterwards respectively, improved the ability of padding washing device bottom absorption ammonia again.By above improvement, can with the outlet tail gas ammonia content by 0.5% present (volume) about, drop to below 0.0020% (volume), the ammonia content of tail gas reduces more than 250 times, tail gas process separator is dehydrogenation gas recovery system directly, consumption of power is removed clean ammonia again, also no longer produces weak aqua ammonia, need not consume steam and electricity and remove distillation, concentrate weak aqua ammonia.

Absorbing ammonia with urea desorb waste water is twice laid, does not need specially to prepare, and desorb waste water has overbottom pressure to utilize, and the water that makes the system of joining is consumption of power not also.

Because high concentration ammoniacal liquor directly goes one to inhale tower, desalination water pump power consumption is actual to be to be used on the ammoniacal liquor that adds a suction tower, is equivalent to the desalination water pump and has done merit for two table pumps and the diformazan pump of urea.

Like this, by above improvement, can realize not consumption of power of all processes that isobaric ammonia reclaims the utilization that comprises ammoniacal liquor, realize that the isobaric ammonia of unpowered low temperature reclaims, and has improved economic benefit and environmental benefit that isobaric ammonia reclaims greatly.

For the synthesis ammonia plant of not producing urea, high concentration ammoniacal liquor can be washed the industrial ammonia that weak aqua ammonia that the weak aqua ammonia of tower and ammoniacal copper solution scrubbing generated gas ammonia reclaims blends into 20% (weight) and sold with putting forward the hydrogen high pressure ammonia, multiprocessing again, consumed some weak aqua ammonias.

Isobaric ammonia recovery unit is equivalent to isobaric ammonia reclaiming process and clean ammonia process are combined, the technology that is added water, secondary discharge (rare) ammoniacal liquor by the clean ammonia of secondary, secondary, change into once clean ammonia, once add water, once discharge the technology of high concentration ammoniacal liquor, save demineralized water, no longer discharged weak aqua ammonia.

But be not simply with isobaric ammonia recovery tower and ammonia-cleaning tower is combined, stack, if isobaric ammonia recovery tower and ammonia-cleaning tower are grouped together simply, can be interactional.In order to reach clean ammonia effect, the desalination water yield that ammonia-cleaning tower adds is bigger, and namely liquid-gas ratio is higher, so the temperature rise of weak aqua ammonia is little in the packing layer of ammonia-cleaning tower bottom, the desalination water yield that ammonia-cleaning tower adds is unrestricted, can strengthen the addition of demineralized water; But the desalination water yield that isobaric ammonia recovery unit adds is restricted, otherwise the ammonia concn of preparation is low; The desalination water yield that isobaric ammonia recovery unit adds is than lacking that ammonia-cleaning tower adds, can cause the temperature rise of weak aqua ammonia in the packing layer of padding washing device bottom to increase, influence clean ammonia effect, especially before entering isobaric ammonia recovery unit, the ammonia content of off-gas has dropped to about 20% (volume), isobaric ammonia recovery unit demineralized water consumption reduces to original 1/4th, further improved the concentration of ammoniacal liquor again, the demineralized water consumption reduces again significantly, the demineralized water consumption has only original about 1/17th, can cause the temperature rise of weak aqua ammonia in the packing layer of padding washing device bottom higher, outlet tail gas ammonia content raises, and does not reach clean ammonia index.

The present invention with the measure of low-temperature liquid ammonia cooling and desalting water, solves the temperature rise problem of weak aqua ammonia in the packing layer of middle and lower part by increased the demineralized water cooler before or after the desalination water pump; By the weak aqua ammonia of packing layer bottom is collected, the cooler of delivering to the outside goes cooling again, and the weak aqua ammonia after the cooling returns distribution again, continues to absorb, and further solves the problem of packing layer bottom weak aqua ammonia temperature rise again.

The padding washing device has not only replaced ammonia-cleaning tower, the column plate that has also replaced the no cooler on traditional isobaric ammonia recovery tower top absorbs ammonia and partly has the column plate of cooler to absorb ammonia, like this, and under same absorption ammonia effect, bubbling absorber cylindrical shell height is low, has reduced weight of equipment and cost.

Isobaric ammonia recovery unit is made up of equipment such as circulation absorption and separation device, the outer ammoniacal liquor cooler of tower, isobaric ammonia recovery tower, separator, demineralized water cooler, desalination water pump, the outer little ammoniacal liquor cooler of first tower and the outer little ammoniacal liquor coolers of second tower; Isobaric ammonia recovery tower is made up of padding washing device two parts that bubbling absorber and the top of bottom increases newly, for the ease of transporting, between connect with flange;

Circulation absorption and separation device, the outer ammoniacal liquor cooler of tower, the outer little ammoniacal liquor cooler of first tower and the outer little ammoniacal liquor cooler of second tower, demineralized water cooler are the equipment that increases newly;

The outer ammoniacal liquor cooler of tower, the outer little ammoniacal liquor cooler of first tower and the outer little ammoniacal liquor cooler of second tower, desalination water pump, demineralized water cooler are chemical industry version commonly used.

Import department has increased circulation absorption and separation device at bubbling absorber off-gas, and the ammoniacal liquor pipeline of the outer ammoniacal liquor cooler of tower is connected with circulation absorption and separation device, has formed absorption, the cooling circuit of high concentration ammoniacal liquor; The delivery port of desalination water pump is connected with the water inlet on padding washing device top, and the demineralized water cooler that increases newly is installed in before or after the desalination water pump; The tail gas outlet of padding washing device is connected with separator; The outer little ammoniacal liquor cooler of first tower and the outer little ammoniacal liquor cooler of second tower are connected with weak aqua ammonia outlet below second section packing layer of padding washing device bottom, the 3rd section packing layer respectively, afterwards, the outer little ammoniacal liquor cooler of each tower is connected with the 3rd section packing layer of padding washing device bottom, the 4th section weak aqua ammonia entrance above the packing layer respectively again.

The outer sleeve bottom of every group of coiled pipe cooler is connected with the tubular gas distributor, and the coil pipe on upper strata and the upper orifice of riser and down-flow plate top margin basic are flat.Can increase or reduce the film-cooled heat of each coiled pipe cooler neatly by increasing or reduce the radical of coil pipe.

Every group of round trip intercooler also leaves bigger hexagon gas-liquid channel in the center of following liquid-collecting box, and also leave bigger annular gas-liquid channel between the cylindrical shell, be conducive to the gas that following multitube gas distributor rises and enter between pipe smoothly, and between pipe, distribute more even; Feed tube and drain pipe stretch out, are welded in the both sides of cylindrical shell respectively, be convenient to above the round trip intercooler tower dividing plate or bubbling column plate are installed, and fixing round trip intercooler; Can increase or reduce the film-cooled heat of round trip intercooler neatly by changing length or the radical of heat exchanger tube.

At the no riser of tower dividing plate and the down-flow plate between the round trip intercooler up and down, the ammoniacal liquor outlet above the tower dividing plate is connected outside cylindrical shell with following ammoniacal liquor import, and following off-gas exports the entrance of multitube gas distributor on the external tower dividing plate of cylindrical shell.

The structured packing total height of padding washing device is generally three meters to 12 meters, establishes one section to four sections packing layer in general.If padding washing device outlet tail gas not dehydrogenation gas reclaims, the index of outlet tail gas ammonia content can be relaxed, the tail gas ammonia content can be higher than 0.002% (volume), at this moment, can cancel the outer little ammoniacal liquor cooler of second tower, the 4th section packing layer of cancellation padding washing device, maybe can cancel the outer little ammoniacal liquor cooler of first tower, the 3rd section packing layer of cancellation padding washing device, can also reduce by first section packing layer of a little padding washing devices, the filler total height of second section packing layer, even the cancellation liquid re-distributor, two sections packing layers are combined into one section packing layer.

Second section at the padding washing device increases the 3rd below the packing layer, the 4th section packing layer, increase the outer little ammoniacal liquor cooler of two towers, not only reduced the temperature that absorbs weak aqua ammonia behind the ammonia, improved the absorbability of padding washing device bottom, can also reduce the height at the superiors coiled pipe cooler place in the bubbling absorber, so that the coiled pipe cooler that the low-temperature liquid ammonia of cooling or cooling water can enter the superiors, also can reduce simultaneously the tower dividing plate that has cooler in the bubbling absorber, the number of plies of bubbling column plate, reduce the height of the thicker relatively bubbling absorber of diameter, reduce equipment manufacturing cost;

Increase the bubbling column plate which floor has the tower dividing plate of round trip intercooler or has coiled pipe cooler, can cancel the outer ammoniacal liquor cooler of circulation absorption and separation device and tower, but increased the height of bubbling absorber, the coiled pipe cooler of topmost may advance not go low-temperature liquid ammonia or cooling water, has also increased the cost of equipment.

Whether below second section packing layer the 3rd section packing layer of increase, increase little ammoniacal liquor cooler outside first tower, or increase the 4th section packing layer again, increase the outer little ammoniacal liquor cooler of second tower again, or do not increase circulation absorption and separation device and the outer ammoniacal liquor cooler of tower, mainly being to depend on process conditions and requirement, secondly is the cost that depends on equipment.

Padding washing device barrel diameter is very thin, generally between φ 200～φ 600, diameter is far below the ammonia recovering effect diameter phi 1000～φ 1400 of tower top cylindrical shell preferably, if the padding washing device of 60 polylith theoretical cam curves adopts tower plate structure, want the column plate of bubbling column plate about 80 layers and no cooler, not only diameter is thick, highly also can be very high, equipment can be very heavy, and cost also can be very high.

The advantage of the inventive method is:

1, each cooler of isobaric ammonia recovery unit is used low-temperature liquid ammonia, the cold liquefied ammonia cooling ammoniacal liquor that my other new technology ammonia recover comes instead, realizes without water quench ammoniacal liquor, has saved power;

2, isobaric ammonia reclaims the surplus cold-peace overbottom pressure cooling of the production of adopting low-temperature liquid ammonia, cold liquefied ammonia ammoniacal liquor, changed into by traditional ammonia of absorption at normal temperatures and to absorb ammonia at low temperatures, the process conditions that absorb ammonia have been optimized greatly, when entrance off-gas ammonia content drops to 20% (volume), also can prepare the high concentration ammoniacal liquor about 45% (weight), realized at normal temperatures or a little more than normal temperature absorb ammonia technical indicator and the effect that can't realize;

3, the water yield that be used for to absorb ammonia reduces to original 1/17th, and the waste water that can use the urea desorb instead absorbs ammonia, can not only save the high demineralized water of preparation cost without demineralized water, has also saved the power consumption of using demineralized water;

4, before the desalination water pump, increased the demineralized water cooler, with low-temperature liquid ammonia demineralized water or desorb waste water are cooled to about 5 ℃, realized washing at low temperatures ammonia, reduce the absorption temperature at padding washing device internal upper part and middle part, be conducive to improve the ability of padding washing device internal upper part and middle part absorption ammonia;

5, the weak aqua ammonia that goes out second, third section packing layer removes the outer little ammoniacal liquor cooler of two towers respectively, and the weak aqua ammonia between cooling section has reduced the weak aqua ammonia temperature of padding washing device bottom.

6, each the cooler area in the outer ammoniacal liquor cooler of tower and the bubbling absorber all from bottom to top reduces gradually, and it is reasonable that film-cooled heat distributes, and meets the actual condition that absorbs ammonia, improved the effect that absorbs ammonia;

7, the high concentration ammoniacal liquor about 45% (weight) of Hui Shouing with the water yield seldom, ammoniacal liquor directly goes one to inhale tower, has saved desorb and depth hydrolysis's a large amount of steam and electricity, utilizes no longer consumption of power of ammoniacal liquor;

8, increase the padding washing device on the top of bubbling display, greatly improved the clean ammonia ability of padding washing device, can reduce the ammonia content of outlet tail gas significantly;

9, outlet tail gas drops to below 0.002% (volume), and tail gas dehydrogenation gas reclaims and do not spend clean ammonia, and no longer consumption of power and demineralized water no longer produce weak aqua ammonia and save steam and the power consumption that increases thus;

10, the synthesis ammonia plant of producing urea can realize that the isobaric ammonia of real unpowered low temperature reclaims;

11, increased the outer ammoniacal liquor cooler of circulation absorption and separation device and tower, off-gas and ammoniacal liquor in circulation absorption and separation device with cross-flow, and stream, three kinds of modes of adverse current absorb, it is poor to have improved the intersegmental ammonia concn of area with high mercury, and obtaining also will good effect than in bubbling absorber one deck column plate;

12, do not need external power, the circulation that high concentration ammoniacal liquor absorbs automatically, cools off between the ammoniacal liquor cooler outside circulation absorption and separation device and tower.

The advantage of present device is:

1, the theoretical cam curve of the padding washing device on isobaric ammonia recovery tower top can provide very many theoretical cam curves more than 60 in not too high limited height, and this has brought into play important effect to reducing in the tail gas ammonia content significantly;

If the padding washing device of 2 six ten polylith theoretical cam curves adopts tower plate structure, not only diameter is thick, highly also can be very high, and equipment can be very heavy, and cost also can be very high.

3, the film-cooled heat of each cooler on the outer ammoniacal liquor cooler of tower and each layer column plate from bottom to top reduces gradually, has namely guaranteed required film-cooled heat, does not waste film-cooled heat again, and has given full play to the ability of each column plate absorption ammonia;

4, increased the outer ammoniacal liquor cooler of circulation absorption and separation device and tower, it is poor to have strengthened intersegmental ammonia concn, has alleviated the load of isobaric ammonia recovery tower, thereby has improved whole assimilation effect;

5, the bubbling absorber adopts coiled pipe cooler and round trip intercooler, can arrange bigger film-cooled heat in the lower very limited height between the bubbling column plate and between the tower dividing plate, and each cooler can be adjusted to area and have nothing in common with each other.

6, bubbling absorber barrel diameter is reduced to φ 600～φ 1400, than little many of present isobaric ammonia recovery tower lower diameter φ 1600～φ 1800, has reduced weight of equipment and cost;

7, padding washing device barrel diameter is very thin, generally between φ 200～φ 600, than little many of present isobaric ammonia recovery tower upper diameter φ 1000～φ 1400, has reduced weight of equipment and cost again;

8, the bubbling column plate has baffling demister and discharge opeing liquid sealing pipe, has reduced entrainment;

9, before or after the desalination water pump, increased the demineralized water cooler.

10, below second, third section packing layer, be provided with first feeder and second feeder, the weak aqua ammonia of collecting second, third section packing layer goes tower to cool off outward, turns back to the 3rd, the 4th section packing layer after the cooling.

11, when system shutdown, the ammoniacal liquor on each layer column plate can not fall into down one deck column plate, can not cause the ammoniacal liquor of each layer column plate in the tower all to fall at the bottom of the tower, can not influence the driving after isobaric ammonia recovery system stops.

Below in conjunction with accompanying drawing the present invention is described in further detail.

Description of drawings

Fig. 1 is process chart of the present invention.

Fig. 2 is bubbling absorber structure sketch of the present invention.

Fig. 3 is padding washing device structure diagram of the present invention.

Fig. 4 is circulation absorption and separation device structure diagram of the present invention.

The specific embodiment

The isobaric ammonia recovery method of unpowered low temperature:

Referring to Fig. 1, isobaric ammonia recovery tower is made up of padding washing device 9 two parts that bubbling absorber 8 and the top of bottom increases newly, for the ease of transportation, between connect with flange; Before the off-gas entrance 23 of bubbling absorber 8, increased circulation absorption and separation device 1, the high strength ammonia water out of circulation absorption and separation device 1 is connected with the import and export of import with the high concentration ammoniacal liquor of the outer ammoniacal liquor cooler 2 of the tower that increases newly, forms absorption, the cooling circuit of high concentration ammoniacal liquor; Padding washing device 9 gas vents are connected with separator 3, and water inlet is connected with desalination water pump 5, have increased demineralized water cooler 4 at the import or export of desalination water pump 5; Increased outside first tower little ammoniacal liquor cooler 7 outside the little ammoniacal liquor cooler 6 and second tower in the outside of padding washing device 9 bottoms, cool off the weak aqua ammonia of second section packing layer outlet and the 3rd section packing layer outlet respectively, cooled weak aqua ammonia returns the 3rd section packing layer entrance and the 4th section packing layer entrance respectively.By above improvement, increased substantially the absorbability of isobaric ammonia recovery unit, for the isobaric ammonia of unpowered low temperature reclaims the required condition of having created.

Referring to Fig. 1, Fig. 2,-6～0 ℃ of low-temperature liquid ammonias from the ammonia recover, be introduced into ammoniacal liquor cooler 2 cooling high concentration ammoniacal liquor outside the tower through low-temperature liquid ammonia import 64, most of low-temperature liquid ammonia removes each the round trip intercooler 40 cooling concentrated ammonia liquor in the bubbling absorber 8 afterwards, remove each coiled pipe cooler 39 cooling ammoniacal liquor again, go out system by low-temperature liquid ammonia outlet 66 afterwards, remove other low temperature cool exchanger, or remove the liquefied ammonia storage tank; Another small part low-temperature liquid ammonia is removed brine cooler 4, goes low-temperature liquid ammonia outlet 66 behind the cooling and desalting water; The low-temperature liquid ammonia of round trip intercooler 40 outlets also can remove the outer little ammoniacal liquor cooler 6 of first tower and the outer little ammoniacal liquor cooler 7 cooling weak aqua ammonias of second tower;

Cold liquefied ammonia from about 15 ℃ of ammonia recovers, remove outside first tower little ammoniacal liquor cooler 7 cooling weak aqua ammonias outside the little ammoniacal liquor cooler 6 and second tower through cold liquefied ammonia import 65, also can remove coiled pipe cooler 39 cooling ammoniacal liquor, remove cool exchanger through cold liquefied ammonia outlet 67 afterwards, or remove the liquefied ammonia storage tank, if low-temperature liquid ammonia is enough, then need not cold liquefied ammonia;

High strength ammonia coolant-temperature gage in the outer ammoniacal liquor cooler 2 of tower is dropped to about 5 ℃, demineralized water in the demineralized water cooler 4 is also dropped to about 5 ℃, by in the winter time about 20 ℃, about 40 ℃ of summer, absorb ammonia, change into and absorb ammonia throughout the year at low temperatures, thereby optimized acceptance condition greatly, improved assimilation effect significantly, can reach at normal temperature or a little more than absorbing technical indicator that ammonia is beyond one's reach and assimilation effect under the normal temperature.

Ammoniacal liquor cooler 2 is to bubbling absorber 8 interior each round trip intercooler 40, each coiled pipe cooler 39 outside tower, and film-cooled heat distributes by from bottom to top reducing gradually.More than the area of each cooler, be to reduce gradually to the amount that each tower dividing plate 30, each bubbling column plate 10 absorb ammonia by ammoniacal liquor cooler 2 outside tower, the heat of solution of emitting is also reducing gradually, the cooling load of each cooler also reduces gradually distributes, meet the actual condition that absorbs ammonia, can give full play to the effect of each absorption tray.

Isobaric ammonia recovery unit has increased absorption hop count and the absorption tray number of plies that has cooler, and it is reasonable that film-cooled heat distributes, and has improved the absorbability of middle and high concentration range significantly.

When entrance off-gas ammonia content drops to 20% (volume) left and right sides, be difficult to prepare 45% (weight) left and right sides high concentration ammoniacal liquor at normal temperatures, owing to absorb ammonia at low temperatures, still ammonia concn can be brought up to about 45% (weight), the high concentration ammoniacal liquor for preparation directly goes a suction tower to create condition again.

The ammonia concentration of the high concentration ammoniacal liquor about 45% (weight) has surpassed the concentration of urea diformazan liquefied ammonia, also surpasses the ammonia concentration of a first liquid.With my other new technology, drop to about 20% (volume) about by 50% (volume) the off-gas ammonia content of entrance after, it is original 1/4th that the water yield of adding reduces to, ammonia vol also significantly reduces; And after the concentration of ammoniacal liquor brings up to about 45% (weight) about by 15% (weight), it is original below 1/4th that the water yield that adds reduces to again, like this, the water yield that adds has reduced to original 1/17th, the water of being brought into a suction tower by ammoniacal liquor is considerably less, only account for about 0.32% of a first liquid measure, minimum to the steam/hydrocarbons ratio influence that urea is synthetic.The pressure of isobaric ammonia recovery tower is higher than the pressure of a suction tower, concentration is that the high concentration ammoniacal liquor about 45% (weight) can directly go one to inhale tower without pump, after first pump pressurization, go urea synthesizer to produce urea, ammoniacal liquor no longer goes the desorption system of urea and the distillation of depth hydrolysis system, concentrate, reclaims, utilizes isobaric ammonia to reclaim the ammoniacal liquor that produces and no longer consume a large amount of steam and power.

(or afterwards) increased demineralized water cooler 4 before desalination water pump 5, by reducing the temperature of demineralized water, reaches the purpose that reduces padding washing device 9 tops and middle part absorption temperature.

The theoretical cam curve of padding washing device 9 is about 60, to absorb again about water cooling to 5 that ammonia uses ℃, padding washing device 9 tops absorb ammonia at low temperatures, 9 second sections packing layers of padding washing device and the 3rd section weak aqua ammonia that packing layer falls can also be gone outer little ammoniacal liquor cooler 6 coolings of first tower respectively and go outer little ammoniacal liquor cooler 7 coolings of second tower, return next section packing layer afterwards respectively, improved the ability that padding washing device 9 bottoms absorb, wash ammonia again.By above each measure, can with the outlet tail gas ammonia content by 0.5% present (volume) about, drop to below 0.0020% (volume), the ammonia content of tail gas reduces more than 250 times, tail gas process separator 3 is dehydrogenation gas recovery system directly, consumption of power is removed clean ammonia again, also no longer produces weak aqua ammonia, need not consume steam and electricity and remove distillation, concentrate weak aqua ammonia.

To change desorb waste water with urea into demineralized water, desorb waste water is twice laid, does not need specially to prepare, and desorb waste water has overbottom pressure to utilize, and the water that makes the system of joining is consumption of power not also.

Because high concentration ammoniacal liquor directly goes one to inhale tower, desalination water pump 5 power consumptions are actual to be to be used on the ammoniacal liquor that adds a suction tower, is equivalent to desalination water pump 5 and has done merit for two table pumps and the diformazan pump of urea.

Like this, by above measure, can realize not consumption of power of all processes that isobaric ammonia reclaims the utilization that comprises ammoniacal liquor, realize that the isobaric ammonia of unpowered low temperature reclaims, and has improved economic benefit and environmental benefit that isobaric ammonia reclaims greatly.

Structure, the form of isobaric ammonia recovery unit:

Referring to Fig. 1, isobaric ammonia recovery unit is made up of equipment such as circulation absorption and separation device 1, the outer ammoniacal liquor cooler 2 of tower, isobaric ammonia recovery tower, separator 3, demineralized water cooler 4, desalination water pump 5, the outer little ammoniacal liquor cooler 6 of first tower and the outer little ammoniacal liquor coolers 7 of second tower; Isobaric ammonia recovery tower is made up of padding washing device 9 two parts that bubbling absorber 8 and the top of bottom increases newly, for the ease of transporting, between connect with flange;

Circulation absorption and separation device 1, the outer ammoniacal liquor cooler 2 of tower, the outer little ammoniacal liquor cooler 6 of first tower and the outer little ammoniacal liquor cooler 7 of second tower, demineralized water cooler 4 are the equipment that increases newly;

The outer ammoniacal liquor cooler 2 of tower, the outer little ammoniacal liquor cooler 6 of first tower and the outer little ammoniacal liquor cooler 7 of second tower, desalination water pump 5, demineralized water cooler 4 are chemical industry version commonly used.

8 off-gas import departments have increased circulation absorption and separation device 1 at the bubbling absorber, and the ammoniacal liquor pipeline of the outer ammoniacal liquor cooler 2 of tower is connected with circulation absorption and separation device 1, has formed absorption, the cooling circuit of high concentration ammoniacal liquor; The delivery port of desalination water pump 5 is connected with the water inlet on padding washing device 9 tops, and the demineralized water cooler 4 that increases newly is installed in before or after the desalination water pump 5; The tail gas outlet of padding washing device 9 is connected with separator 3; The weak aqua ammonia entrance of the outer little ammoniacal liquor cooler 6 of first tower and the outer little ammoniacal liquor cooler 7 of second tower is connected with weak aqua ammonia outlet below second section packing layer of padding washing device 9 bottoms, the 3rd section packing layer respectively, afterwards, the weak aqua ammonia outlet of the outer little ammoniacal liquor cooler 6 of first tower and the outer little ammoniacal liquor cooler 7 of second tower is connected with the 3rd section packing layer of padding washing device 9 bottoms, the 4th section weak aqua ammonia entrance above the packing layer respectively again.

Referring to Fig. 1, Fig. 2, liquefied ammonia cooling high strength ammonia water, ammoniacal liquor, weak aqua ammonia and demineralized water that each cooler of isobaric ammonia recovery unit can serviceability temperature be low, pressure is high.Described each cooler comprises: the outer little ammoniacal liquor cooler 6 of each round trip intercooler 40, each coiled pipe cooler 39, first tower in the outer ammoniacal liquor cooling 2 of tower, the bubbling absorber 8 and the outer little ammoniacal liquor cooler 7 of second tower, demineralized water cooler 4.

Referring to Fig. 4, circulation absorption and separation device 1 comprises cylindrical shell 71, be provided with gas vent 70, liquid distribution trough 72, packing layer 73, concentrated ammonia liquor import 85 on the top of cylindrical shell 71, the middle part has porous plate 84, trunnion 83, collapsible tube 82, bottom that high strength ammonia water inlet 76, nozzle 81 are arranged, has the air jet pipe 77, high strength ammonia water out 80, off-gas import 78, high concentration ammoniacal liquor outlet 79 in hole etc., is provided with interface of the level gauge 74,75 at the middle part of cylindrical shell 71.Concentrated ammonia liquor import 85, gas vent 70 are connected with the off-gas entrance 23 of bottom with the concentrated ammonia liquor of bubbling absorber 8 bottoms outlet 22 respectively; High strength ammonia water out 80, high strength ammonia water inlet 76 are connected with the high strength ammonia water entrance of the outer ammoniacal liquor cooler 2 of the tower that increases newly respectively, under the situation that does not need external power, the circulation that high concentration ammoniacal liquor absorbs automatically, cools off, absorbs between the ammoniacal liquor cooler 2 outside circulation absorption and separation device 1 and tower; In circulation absorption and separation device 1, concentrated ammonia liquor, high strength ammonia water respectively with adverse current, and stream, three kinds of absorption patterns of cross-flow absorb the ammonia in the off-gas, increased and bubbling absorber 8 bottoms between intersegmental ammonia concn poor, further improved the concentration of discharging ammoniacal liquor mouth high concentration ammoniacal liquor, obtained than in the bubbling absorber 8 interior effects that column plate is not bad.

Referring to Fig. 2, described bubbling absorber 8 comprises cylindrical shell 35, the top of cylindrical shell 35 has adpting flange 38 to be connected with the flange of padding washing device 9 bottoms, connected entrance 37 is arranged at top, and following concentrated ammonia liquor outlet 22 is connected with gas vent 70 with the concentrated ammonia liquor entrance 85 of circulation absorption and separation device 1 respectively with off-gas entrance 23.Because do not adopt water tank cooling ammoniacal liquor, so need not add thick barrel 35 diameters artificially, cylindrical shell 35 diameters are thinner, cylindrical shell 35 diameters are generally at φ 600～φ 1400, and bubbling absorber 8 cylindrical shells 35 diameters are lower than present ammonia recovering effect isobaric ammonia recovery tower preferably.Be provided with one or more layers bubbling column plate 10 in the cylindrical shell 35 from top to bottom, mounting disc chimney cooler 39 on bubbling column plate 10; On the bottom of cylindrical shell 35 or the following one or more layers of tower dividing plate 30 round trip intercooler 40 is installed, each coiled pipe cooler 39 and each round trip intercooler 40 and below bubbling column plate 10 and tower dividing plate 30 between tubular gas distributor 12 and multitube gas distributor 29 are installed; No tower dividing plate 30 below the round trip intercooler 40 that install cylindrical shell 35 bottoms.The area of each cooler all from top to bottom increases gradually in the cylindrical shell 35.

Every group of coiled pipe cooler 39 comprises one or an above involute shape coil pipe 11, the import and export of its each coil pipe 11 are connected with outlet header 33 with intake header 32 respectively, each coil pipe 11 is fixed by some support fixation elements, inlet tube 31, outlet 34 are connected with outlet header 33 with intake header 32 respectively, and intake header 32 and outlet header 33 are in the same side of cylindrical shell 35 axis.Be tubular gas distributor 12, bubbling column plate 10 below the coil pipe 11; Be provided with down-flow plate 36 on the bubbling column plate 10 below coiled pipe cooler 39 and between the cylindrical shell 35, the centre of bubbling column plate 10 is equipped with riser 14 and outer tube 13, the bottom of outer tube 13 is connected with tubular gas distributor 12, the coil pipe 11 on coiled pipe cooler 39 upper stratas is flat with upper orifice and down-flow plate 36 top margins basic of riser 14, and the centre of bubbling column plate 10 bottoms is provided with baffling demister 15 and discharge opeing liquid sealing pipe 16.Can increase or reduce the film-cooled heat of each coiled pipe cooler 39 neatly by increasing or reduce the radical of coil pipe 11.

Every group of round trip intercooler 40 comprises liquid-collecting box 19, liquid-collecting box 24, heat exchanger tube 26, several gripper shoes 25, feed tube 18 and drain pipe 27 etc. that quantity is a lot of down; The bigger gas-liquid channel of hexagon 21 is left in center at last liquid-collecting box 19, following liquid-collecting box 24, and also leaves bigger annular gas-liquid channel between the cylindrical shell 35.Leave bigger hexagon gas-liquid channel 21 in the following center of liquid-collecting box 24, and leave bigger annular gas-liquid channel between the cylindrical shell 35, be conducive to the gas that following multitube gas distributor 29 rises and enter smoothly between pipe, and between pipe, distribute more even; Feed tube 18 and drain pipe 27 stretch out, are welded in the both sides of cylindrical shell 35 respectively, so that tower dividing plate 30 or bubbling column plate 10 are installed above round trip intercooler 40, and fixing round trip intercooler 40; In the liquid-collecting box 19 dividing plate is arranged between feed tube 18, drain pipe 27.Can increase or reduce the film-cooled heat of round trip intercooler 40 neatly by changing length and the radical of heat exchanger tube 26.

At tower dividing plate 30 no riser 14 and down-flow plates 36 between the round trip intercooler 40 up and down, ammoniacal liquor outlet 17 above the tower dividing plate 30 is connected outside cylindrical shell 35 with following ammoniacal liquor import 20, the entrance of following off-gas outlet 28 multitube gas distributor 29 on cylindrical shell 35 external tower dividing plates 30.

The low concentration region of residual ammonia in the padding washing device 9 washing absorption tail gas on bubbling absorber 8 tops, reduce in the water yield that absorbs ammonia under original 1/17th the very unfavorable conditions, again the tail gas ammonia content is dropped to below 0.002% (volume) about by 0.5% (volume), it is very difficult that ammonia content descends more than 250 times again, and the theoretical cam curve about 60 need be arranged in padding washing device 9.

Referring to Fig. 3, described padding washing device 9 comprises cylindrical shell 44, owing to no serpentine (trombone) coolers in the cylindrical shell 44, also do not have little water tank, so cylindrical shell 44 diameters are very thin, cylindrical shell 44 diameters are generally at φ 200～φ 600.Cylindrical shell 44 bottoms have adpting flange 53 to be connected with the flange 38 on bubbling absorber 8 tops; Cylindrical shell 44 internal upper parts are wire mesh demisters 41, and liquid distribution trough 42 is arranged below, are the packing layers more than a section or a section that structured packing is housed below the liquid distribution trough 42.Between two sections packing layers of first section packing layer 43 and second section packing layer 46, can be provided with liquid re-distributor 45, the effect of liquid re-distributor 45 is that the liquid that the preceding paragraph packing layer gets off is distributed again equably, improve assimilation effect, also can not establish liquid re-distributor 45, but assimilation effect is weaker;

Or below second section packing layer 46, establish and have weak aqua ammonia and once export 57 first feeder 47, second liquid distribution trough 48 that has an import 56 of weak aqua ammonia and the 3rd section packing layer 49, and outside cylindrical shell 44, be provided with the outer little ammoniacal liquor cooler 6 of little ammoniacal liquor cooler 6, the first towers outside first tower and be connected with an import of the weak aqua ammonia 56 usefulness pipelines that the weak aqua ammonia of first feeder 47 once exports 57, second liquid distribution trough 48 respectively;

Or below the 3rd section packing layer 49, establish second feeder 50, the 3rd liquid distribution trough 51 that has weak aqua ammonia secondary import 54 and the 4th section packing layer 52 that has weak aqua ammonia secondary outlet 55; And outside cylindrical shell 44, be provided with little ammoniacal liquor cooler 7 outside second tower, be connected with corresponding interface with pipeline equally.

Before padding washing device 9 water inlets 58 or be provided with demineralized water cooler 4 before the desalination water pump 5, for reducing the temperature of the demineralized water that joins padding washing device 9 or desorb waste water.

Each round trip intercooler 40 in the outer ammoniacal liquor cooler 2 of tower, the bubbling absorber 8, the film-cooled heat of each coiled pipe cooler 39 from bottom to top reduce gradually, thereby have brought into play the absorbability of circulation absorption and separation device 1 with each layer tower dividing plate 30, each layer bubbling column plate 10 better.

The structured packing total height of padding washing device 9 is generally 3 meters to 12 meters, establishes 1 section to 4 sections packing layer in general.If padding washing device 9 outlet tail gas not dehydrogenation gas reclaim, the index of outlet tail gas ammonia content can be relaxed, the tail gas ammonia content can be higher than 0.002% (volume), at this moment, can cancel the outer little ammoniacal liquor cooler 7 of second tower, the 4th section packing layer 52 of cancellation padding washing device 9, maybe can cancel the outer little ammoniacal liquor cooler 6 of first tower, the 3rd section packing layer 49 of cancellation padding washing device 9, can also reduce by first section packing layer 43 of a little padding washing devices 9, the filler total height of second section packing layer 46, even cancellation liquid re-distributor 45, two sections packing layers are combined into one section packing layer.

Second section packing layer at the padding washing device increases the 3rd section packing layer 49 below 46, the 4th section packing layer 52, increase the outer little ammoniacal liquor cooler 6 and 7 of 2 towers, not only reduced the temperature that absorbs weak aqua ammonia behind the ammonia, improved the absorbability of padding washing device 9 bottoms, can also reduce the height at the superiors coiled pipe cooler 39 places in the bubbling absorber 8, so that low-temperature liquid ammonia or cooling water can enter the coiled pipe cooler 39 of the superiors, also can reduce simultaneously the tower dividing plate 30 that has cooler in the bubbling absorber 8, the number of plies of bubbling column plate 10, reduce the height of the thicker relatively bubbling absorber 8 of diameter, reduce equipment manufacturing cost;

Increase the bubbling column plate 10 which floor has the tower dividing plate 30 of round trip intercooler 40 or has coiled pipe cooler 39, can cancel the outer ammoniacal liquor cooler 2 of circulation absorption and separation device 1 and tower, but increased the height of bubbling absorber 8, the coiled pipe cooler 39 of topmost may advance not go low-temperature liquid ammonia or cooling water, has also increased weight and the cost of equipment.

Whether below second section packing layer 46 the 3rd section packing layer 49 of increase, increase little ammoniacal liquor cooler 6 outside first tower, or increase the 4th section packing layer 52 again, increase the outer little ammoniacal liquor cooler 7 of second tower again, or do not increase circulation absorption and separation device 1 and the outer ammoniacal liquor cooler 2 of tower, mainly being to depend on process conditions and requirement, secondly is the cost that depends on equipment.

Padding washing device 9 cylindrical shells 44 diameters are very thin, generally between φ 200～φ 600, diameter is far below the ammonia recovering effect diameter phi 1000～φ 1400 of tower top cylindrical shell preferably, if the padding washing device of 60 polylith theoretical cam curves 9 adopts tower plate structure, not only diameter is thick, highly also can be very high, equipment can be very heavy, and cost also can be very high.

Produce 200000 tons of synthesis ammonia plants per year for one, per hour produce 25.26 tons of ammonia, per hour the no amino of being discharged by the liquefied ammonia storage tank discharges tolerance at 880 mark rice ³About, if the ammonia content of liquefied ammonia storage tank outlet off-gas is about 50% (volume), per hour take about 667.86 kilograms of the ammonia of isobaric ammonia recovery system to from the liquefied ammonia storage tank, take about 5289 tons of the ammonia of isobaric ammonia recovery system the whole year to, 35263 tons of the ammoniacal liquor that can prepare 15% (weight), if these ammoniacal liquor go desorb, the depth hydrolysis, to consume 10578 tons of low pressure and high steams more, be worth 158.67 ten thousand yuan, the about 52890kwh of many power consumptions, 4.23 ten thousand yuan of the electricity charge, preparation ammoniacal liquor will consume 29973 tons of demineralized waters, is worth 11.99 ten thousand yuan, about 52.89 tons of the ammonia that minimizing is taken out of by isobaric ammonia recovery tower outlet tail gas, be worth 17.98 ten thousand yuan, save recirculated water and the about 237600kwh of desalination water pump power consumption, 19.00 ten thousand yuan of the electricity charge.More than add up to save 211.87 ten thousand yuan altogether the whole year.

Claims

1. the isobaric ammonia recovery method of unpowered low temperature is characterized in that several or whole cooler of isobaric ammonia recovery unit is lower than the liquefied ammonia cooling ammoniacal liquor of cooling water and absorbs the water that ammonia is used with temperature;

Described isobaric ammonia recovery unit comprises isobaric ammonia recovery tower, and isobaric ammonia recovery tower is made up of the bubbling absorber (8) of bottom and padding washing device (9) two parts on top;

Off-gas entrance (23) at bubbling absorber (8) is connected with circulation absorption and separation device (1), the high strength ammonia water out of circulation absorption and separation device (1) is connected with the import and export of import with the high concentration ammoniacal liquor of the outer ammoniacal liquor cooler (2) of tower, off-gas is introduced into circulation absorption and separation device (1), outside tower, absorb earlier ammonia, by ammoniacal liquor with and stream, reflux type absorbs ammonia, high concentration ammoniacal liquor does not need external power to absorb automatically between the ammoniacal liquor cooler (2) outside circulation absorption and separation device (1) and tower, cooling, the circulation that absorbs, external refrigeration adds inner cooling and absorbing ammonia; Padding washing device (9) gas vent is connected with separator (3), padding washing device (9) water inlet is connected with desalination water pump (5), demineralized water cooler (4) is installed in before or after the desalination water pump (5), with low-temperature liquid ammonia cooling and absorbing ammonia water, the desorb waste water of using urea instead absorbs ammonia; Increased outside first tower little ammoniacal liquor cooler (7) outside the little ammoniacal liquor cooler (6) and second tower in the outside of padding washing device (9) bottom;

Comprise cylindrical shell (35) in the described bubbling absorber (8), top in the cylindrical shell (35) is provided with the one or more layers bubbling column plate (10) that has coiled pipe cooler (39), is provided with tubular gas distributor (12) between coiled pipe cooler (39) and bubbling column plate (10); On bottom in the cylindrical shell (35) or the following one or more layers of tower dividing plate (30) round trip intercooler (40) is installed, is provided with multitube gas distributor (29) below the round trip intercooler (40); No tower dividing plate (30) below the round trip intercooler (40) of bottom;

Three meters to 12 meters of the structured packing total heights of the interior packing layer more than a section or a section of padding washing device (9) on described top; Intersegmental weak aqua ammonia between two sections structured packings of padding washing device (9) bottom removes the outer little ammoniacal liquor cooler (6) of the first outside tower and the outer little ammoniacal liquor cooler (7) of second tower, returns next section packing layer after the cooling;

Described cooler comprises the outer ammoniacal liquor cooler (2) of round trip intercooler (40), coiled pipe cooler (39), tower, demineralized water cooler (4), the outer little ammoniacal liquor cooler (6) of first tower and the outer little ammoniacal liquor cooler (7) of second tower in the bubbling absorber (8).

2. according to the isobaric ammonia recovery method of the described unpowered low temperature of claim 1, it is characterized in that the high concentration ammoniacal liquor, concentrated ammonia liquor, weak aqua ammonia, the isobaric ammonia recovery unit that isobaric ammonia are reclaimed with liquefied ammonia absorb in the water that ammonia uses one or more and be cooled to the temperature that temperature is lower than cooling water, absorb ammonia being lower than under the cooling water temperature.

3. according to the isobaric ammonia recovery method of the described unpowered low temperature of claim 1, it is characterized in that the film-cooled heat of each round trip intercooler (40) in the bubbling absorber (8) of from tower outside ammoniacal liquor cooler (2), each coiled pipe cooler (39) is by minimizing distribution gradually.

4. isobaric ammonia recovery unit that the isobaric ammonia recovery method of unpowered low temperature according to claim 1 adopts, it is characterized in that comprising isobaric ammonia recovery tower, isobaric ammonia recovery tower is made up of the bubbling absorber (8) of bottom and padding washing device (9) two parts on top;

The off-gas entrance (23) of bubbling absorber (8) is connected with circulation absorption and separation device (1), and the high strength ammonia water out of circulation absorption and separation device (1) is connected with the import and export of import with the high concentration ammoniacal liquor of the outer ammoniacal liquor cooler (2) of tower; Padding washing device (9) gas vent is connected with separator (3), and padding washing device (9) water inlet is connected with desalination water pump (5), and demineralized water cooler (4) is installed in before or after the desalination water pump (5); Increased outside first tower little ammoniacal liquor cooler (7) outside the little ammoniacal liquor cooler (6) and second tower in the outside of padding washing device (9) bottom;

Described bubbling absorber (8) comprises cylindrical shell (35), top in the cylindrical shell (35) is provided with the one or more layers bubbling column plate (10) that has coiled pipe cooler (39), is provided with tubular gas distributor (12) between coiled pipe cooler (39) and bubbling column plate (10); On bottom in the cylindrical shell (35) or the following one or more layers of tower dividing plate (30) round trip intercooler (40) is installed, is provided with multitube gas distributor (29) below the round trip intercooler (40); No tower dividing plate below the round trip intercooler (40) of bottom;

Three meters to 12 meters of the structured packing total heights of the interior packing layer more than a section or a section of padding washing device (9) on described top; Intersegmental weak aqua ammonia between two sections structured packings of padding washing device (9) bottom removes the outer little ammoniacal liquor cooler (6) of the first outside tower and the outer little ammoniacal liquor cooler (7) of second tower, returns next section packing layer after the cooling.

5. according to the described isobaric ammonia recovery unit of claim 4, it is characterized in that padding washing device (9) comprises the cylindrical shell (44) of band gas vent and water inlet (58), cylindrical shell (44) bottom has flange (53) to be connected with the flange (38) at bubbling absorber (8) top, cylindrical shell (44) internal upper part is wire mesh demister (41), liquid distribution trough (42) is arranged below, is the packing layer more than a section or a section that structured packing is housed below the liquid distribution trough (42); Between two sections packing layers of first section packing layer (43) and second section packing layer (46), be provided with liquid re-distributor (45);

Or below second section packing layer (46), be provided with the band weak aqua ammonia once export first feeder (47) of (57), second liquid distribution trough (48) that has an ammonia import of rare water (56) and the 3rd section packing layer (49), outside cylindrical shell (44), increase little ammoniacal liquor cooler (6) outside first tower, and once export (57) with weak aqua ammonia and be connected with an ammonia import of rare water (56);

Or below the 3rd section packing layer (49), be provided with second feeder (50), the 3rd liquid distribution trough (51) that has weak aqua ammonia secondary import (54) and the 4th section packing layer (52) of band weak aqua ammonia secondary outlet (55), outside cylindrical shell (44), increase little ammoniacal liquor cooler (7) outside second tower, and be connected with the rare water secondary of ammonia import (54) with weak aqua ammonia secondary outlet (55).

6. according to the described isobaric ammonia recovery unit of claim 4, it is characterized in that the film-cooled heat of each coiled pipe cooler (39), each round trip intercooler (40) is all different, all from top to bottom increase gradually;

Every group of coiled pipe cooler (39) is made up of one or an above involute shape coil pipe (11), intake header (32), outlet header (33), inlet tube (31), outlet (34) and support fixation part, tubular gas distributor (12), bubbling column plate (10) are arranged in its lower section, between bubbling column plate (10) and cylindrical shell (35), be equipped with down-flow plate (36), riser (14), outer tube (13) are installed in the centre of bubbling column plate (10), in its bottom baffling demister (15), discharge opeing liquid sealing pipe (16) are installed; Intake header (32), outlet header (33), inlet tube (31), outlet (34) are all in the same sides of cylindrical shell (35);

Every group of round trip intercooler (40) comprise liquid-collecting box (19), down liquid-collecting box (24), heat exchanger tube (26) that quantity is a lot of, circular or annular gripper shoe (25), stretch out feed tube (18) and the drain pipe (27) of cylindrical shell (35) both sides respectively, gas-liquid channel (21) is all left at center at last liquid-collecting box (19), following liquid-collecting box (24), and also leaves bigger gas-liquid channel between the cylindrical shell (35); Between the inherent feed tube of last liquid-collecting box (19) (18) and the drain pipe (27) dividing plate is arranged.

7. according to the described isobaric ammonia recovery unit of claim 4, it is characterized in that being provided with circulation absorption and separation device (1) before at bubbling absorber (8), circulation absorption and separation device (1) comprises cylindrical shell (71), circulation absorption and separation device (1) top is provided with gas vent (70), liquid distribution trough (72), packing layer (73), concentrated ammonia liquor import (85), there is porous plate (84) at the middle part, trunnion (83), collapsible tube (82), high strength ammonia water inlet (76) is arranged at the bottom, nozzle (81), have the air jet pipe (77) in hole, high strength ammonia water out (80), off-gas import (78), high concentration ammoniacal liquor outlet (79), other has two interface of the level gauge (74), (75); Concentration ammoniacal liquor import (85), gas vent (70) connect with the concentrated ammonia liquor outlet (22) of bubbling absorber (8) bottom and the off-gas entrance (23) of bottom respectively, and high strength ammonia water out (80), high strength ammonia water inlet (76) are connected with the high strength ammonia water entrance of the outer ammoniacal liquor cooler (2) of tower respectively.