CN101654248A - Dehydrogenation method of carbon dioxide feed gas - Google Patents
Dehydrogenation method of carbon dioxide feed gas Download PDFInfo
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- CN101654248A CN101654248A CN200910018942A CN200910018942A CN101654248A CN 101654248 A CN101654248 A CN 101654248A CN 200910018942 A CN200910018942 A CN 200910018942A CN 200910018942 A CN200910018942 A CN 200910018942A CN 101654248 A CN101654248 A CN 101654248A
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Abstract
The invention discloses a dehydrogenation method of carbon dioxide feed gas. The method comprises the following steps: 1) injecting oxygen-enriched air in the carbon dioxide feed gas to ensure the content of oxygen to be 1.25-1.4%; 2) injecting the carbon dioxide feed gas containing oxygen-enriched air into a compression engine to compress, performing fine desulfurization, performing heat transferto the desulphurized gas, heating, sending the obtained gas to a dehydrogenation reactor to dehydrogenize to ensure the content of hydrogen and other combustible gases in the dehydrogenized carbon dioxide gas to be less than 50PPm; 3) performing heat transfer to the dehydrogenized gas, cooling, then sending the obtained gas to a CO2 vapour liquid separator to perform gas water separations and finally emptying liquid drops to obtain the gas which is used for the synthesis of urea. The dehydrogenation method of carbon dioxide feed gas adds oxygen to perform dehydrogenation and adds air to perform anticorrosion so as to avoid the problem that a great deal of nitrogen and other inert gases are generated after the dehydrogenation step, reduce the venting amount of the high pressure system, increase the conversion rate, improve the system loading, increase the urea capacity, reduce the absorption loading, desorption loading and hydrolysis loading, lower the consumption of ammonia, steam andthe like and benefit the environmental control.
Description
Technical field
The present invention relates to a kind of method of dehydrogenating of CO 2 raw material gas.
Background technology
At present, adopt CO
2When the stripping production technique is produced urea, at CO
2One section or two sections inlets of compressor add air in certain amount, its main purpose is: one, utilize airborne oxygen under the effect of catalyzer the hydrogen in the unstripped gas to be removed, guarantee that high pressure scrubber drops a hint can quick-fried component remain on can quick-fried scope outside, guarantee security of system; Two, urea production is the reaction of a kind of high temperature, high pressure, highly corrosive, for guaranteeing the long-term operation of urea production equipment, utilizes airborne oxygen to go out the oxide film of one deck densification in the passivation of high-tension apparatus inwall, prevents the high-tension apparatus corrosion.
But, have following defective: CO
2Unstripped gas purity is generally 98%, and hydrogen richness is higher in the unstripped gas, for guaranteeing security of system, prevents to contain in the high-pressure system tail gas too much hydrogen in the urea production, adds air and carries out the dehydrogenation processing, and 79% nitrogen does not participate in reaction in the air, with raw material CO
2Enter high-pressure system, take the synthetic tower effective volume, reduce Synthesis conversion.Rare gas elementes such as airborne nitrogen do not participate in reaction, must too much can increase system's emptying amount by the discharging of high pressure scrubber blow-off valve.Because the amount of releasing of high pressure scrubber blow-off valve has certain limit, the excessive lifting that just has a strong impact on system loading of emptying amount, absorption, desorb, hydrolysis load increase the weight of, and consuming increases, and the environment protection control difficulty strengthens.
Summary of the invention
At above-mentioned existing situation, be the high problem of emptying amount that solves the urea plant high-pressure system, the invention provides a kind of method of dehydrogenating of CO 2 raw material gas, the present invention proposes to add pure oxygen and carries out dehydrogenation in dehydrogenation reactor, add air and carry out anticorrosion, to produce the problem of a large amount of rare gas elementes such as nitrogen after the minimizing dehydrogenation, reduce the emptying amount of high-pressure system, improve transformation efficiency, increase system loading, simultaneously can guarantee certain nitrogen storage again, guarantee security of system.
The present invention is achieved by the following technical solutions:
A kind of method of dehydrogenating of CO 2 raw material gas may further comprise the steps:
1) be that the oxygen-rich air of 21～34% (volumes) joins in the feed carbon dioxide gas with oxygen concentration, make the oxygen level in the feed carbon dioxide gas reach 1.25～1.4% (volumes), guarantee to reach 0.65～0.8% (volume), to satisfy the requirement for anticorrosion of urea production high-pressure system equipment through the oxygen level after the dehydrogenation; Described oxygen-rich air can mix through strict measurement with air by pure oxygen and prepare;
2) CO 2 raw material gas of adding oxygen-rich air in compressor carries out smart desulfurization after compression, and total sulfur content is not higher than 0.2ppm after the desulfurization; Gas after the desulfurization is through heat exchange and be heated to 150～200 ℃, enter dehydrogenation reactor then, combustibleconstituents in oxygen and the carbon dioxide is reacted, remove combustibleconstituentss such as hydrogen in the unstripped gas, methane, carbon monoxide, hydrogeneous and other inflammable gas amount＜50PPm in the carbon dioxide after the dehydrogenation;
3) gas enters CO after the dehydrogenation behind heat exchange and water cooler to 36 ℃ ± 4 ℃
2Vapour liquid separator carries out gas-water separation, enters next section of compressor or directly outer confession behind the emptying drop, is used for the synthetic of urea.
Can directly add the certain oxygen-rich air of oxygen level in the step 1) of the present invention, or the air mixed of a certain amount of pure oxygen and corresponding proportion, join one section on compressor or two sections inlets, with avoid because of oxygen at compressor heavy wool environment incendiary unsafe factor.
When described employing pure oxygen and air mixed prepare oxygen-rich air, can in oxygen-rich air mixing device, carry out.
Described oxygen-rich air mixing device comprises a tank body, and tank body is provided with air intlet, oxygen inlet, oxygen-rich air outlet, discharge outlet, shown in Fig. 2 A, Fig. 2 B, is provided with measuring cell and thermometer in the corresponding position.Oxygen-rich air can prepare in this mixing tank, and the preparation back enters compressor from the oxygen-rich air outlet, and then joins in the CO 2 raw material gas.
Flow process and safety control that above-mentioned oxygen-rich air mixes, can take after desulfurization, the dehydrogenation oxygen level and hydrogen richness on-line analysis monitoring to carry out control operations, oxygen flow meter uses two to select two or three to select measure such as two strict measurement dominant discharge to guarantee safety operation simultaneously.
For guaranteeing the security under the whole system abnormal conditions, can increase newly and jump the car safety interlocking, promptly when any compressor or air compressor machine are jumped cars because of outage or other failure conditions, oxygen intake magnetic valve XSV-01 interlocking close, avoid oxygen to enter and directly enter compressor, have an accident thereby contact with greasy dirt etc.
The present invention adds oxygen and carries out dehydrogenation in dehydrogenation reactor, adding air carries out anticorrosion, to produce the problem of a large amount of rare gas elementes such as nitrogen after the minimizing dehydrogenation, reduce the emptying amount of high-pressure system, improve transformation efficiency, improve system loading, increase the urea production capacity, alleviate absorption, desorb, hydrolysis load, reduce consumption such as ammonia and steam, help environment protection control.
Description of drawings
Fig. 1 is the high pressure scrubber limits of explosion figure that gives vent to anger;
Fig. 2 A is the apparatus sketch of oxygen-rich air mixing device;
Fig. 2 B is the vertical view of Fig. 2 A;
Wherein, N1: air intlet; N2: oxygen inlet; N3: oxygen-rich air outlet; N4: discharge outlet.
Fig. 3 is a process flow sheet of the present invention;
Wherein, FT-01, FT-02 all represent the oxygen stoichiometry under meter, and FT-03, FT-05 represent air metered flow meter, and FT-04 represents oxygen-rich air metered flow meter; XSV-01, XSV02, XSV-03 all represent magnetic valve; FCV-01 represents the oxygen flow variable valve.
Embodiment
Actual the present invention is further illustrated below in conjunction with the operation of example and our factory's (referring to the applicant):
Example 1: a kind of method of dehydrogenating of CO 2 raw material gas, step is as follows:
1) the 1.0Mpa oxygen that divides from sky is after cutting soon, regulate, measuring, enter oxygen-rich air mixing device, in oxygen-rich air mixing device, the pressure of sending with air compressor machine is that 0.35Mpa, temperature are 40 ℃ air mixed, and oxygen content is controlled at 21%～34% in the mixed air.
2) mixed air adds two sections inlets of compressor by magnetic valve, mixes with carbon dioxide, and the oxygen level of mixing in the feed carbon dioxide gas of back reaches 1.25～1.4%, reaches 0.65～0.8% through oxygen level after the dehydrogenation; Through the compression of three sections on compressor, enter desulfurizer from three sections water-and-oil separator outlets, remove CO at this
2Sulfide in the gas, total sulfur normally are controlled at below the 0.2ppm, CO after the desulfurization
2Enter CO
2Interchanger, the CO that comes out with dehydrogenation reactor
2After the heat exchange, enter the well heater that goes into operation again, be steam heated to 150～200 ℃ with 2.5MPa, enter the dehydrogenation reactor that the palladium platinum catalyst is housed then, combustibleconstituents in oxygen and the carbon dioxide reacts, remove combustibleconstituentss such as hydrogen in the unstripped gas, methane, carbon monoxide, hydrogeneous and other inflammable gas amount＜50PPm in the carbon dioxide after the dehydrogenation, the purpose of dehydrogenation is to make the high pressure scrubber exit gas outside can quick-fried scope.
3) after the dehydrogenation gas through CO
2Temperature is reduced to 100 ℃ ± 10 ℃ by 200 ℃ after the interchanger heat exchange, presses CO in entering then
2Water cooler enters CO after being cooled to 36 ℃ ± 4 ℃
2Vapour liquid separator enters four sections inlets of compressor behind the emptying drop, final CO
2Gas is compressed to 15.0MPa and enters high-pressure system and carry out urea synthesis reaction, and last, the rare gas element that does not participate in reacting mixes a part of ammonia, CO
2Discharge from the high pressure scrubber gas phase.
The flow process of described step 1) specifically is described below as shown in Figure 3:
Regulate flow from the air after the air compressor machine pressurization by FCV-02, the FT-03 that flows through enters in the oxygen-rich air mixing device.
Oxygen is regulated flow by FCV-01, and the FT-01 that flows through, FT-02 enter oxygen-rich air mixing device, form oxygen-rich air with air after, the FT-04 that flows through enters each compressor respectively, mixes compression with carbon dioxide and enters dehydrogenation system and carry out the dehydrogenation processing.
Outlet conduit and oxygen-rich air pipeline intersection at air compressor machine are provided with three ball valves, when system condition does not satisfy adding oxygen, can carry out the switching of withdrawing from of oxygen by these three ball valves, the air capacity of using FT-05 to be metered into is guaranteed system's requirement for anticorrosion.
Nitrogen enters in the oxygen channel by magnetic valve XSV-02 control, and by the blow-off valve XSV-03 on oxygen-rich air the mixings device, the oxygen that purge oxygen is stopped using and accumulated in the back pipeline guarantees that pipe safety surrenders.
The ponding that is used to discharge in the mixing tank is fallen to drench in oxygen-rich air mixing device bottom, prevents that profit from entering compressor.
Test
1) safety analysis and comparison
For CO
2The stripping production technique, but the main unsafe factor of its system is the explosive gas content in the high pressure scrubber emptying gas, but if the explosive gas in the high pressure scrubber emptying gas too much be in can quick-fried scope in the time, run into when valve rubs situations such as producing static, compression energy, electrical spark and just can cause high pressure scrubber to produce blast, therefore for CO
2The safety analysis of stripping production technique mainly is the safety analysis that high pressure scrubber is given vent to anger.
Adjust material balance table that the urea project provides as can be known according to sky occasion designing institute at the Yanzhou Coal Mining Lunan Chemical Fertilizer Plant geminus:
Raw material CO
2Total tolerance 20000m
3/ h, wherein hydrogen richness accounts for 0.45%; Through the give vent to anger gas content of discharging of high pressure scrubber behind the urea synthesis reaction be: NH
3: 8.53%, CO
2: 2.68%, O
214.15%, N
2: 70.97%, CH
4: 3.37%, H
2: 0%, Ar:0.299%, gas gross 1074m
3/ h.
Can get the high pressure scrubber middle ammonia 91m that gives vent to anger through calculating
3/ h, methane 36m
3/ h, hydrogen 0m
3/ h, so ammonia accounts for 71.65% in the combustible gas, methane 28.35%.According to the limits of explosion calculation formula,, can calculate the blast bound of its combustible gas in oxygen according to the volume fraction of combustible gas according to the limits of explosion of ammonia and methane:
The Lower Explosive Limit of combustible gas is
L
LOX＝100/(71.65/13.5+28.35/5.5)＝9.56％
The upper explosive limit of combustible gas is
L
HOX＝100/(71.65/79+28.35/60)＝72.5％
According to above data, can make the limits of explosion figure that high pressure scrubber is given vent to anger, as shown in Figure 1.
During high pressure scrubber was given vent to anger before not transforming, indifferent gas accounted for 73.95%, and oxygen accounts for 14.15%, and combustible gas accounts for 11.96%, makes the A point in Fig. 1, can find out that it is positioned at outside the explosive range, so high pressure scrubber is safe.
After adopting the pure oxygen dehydrogenation, the noble gas content of high pressure scrubber is 169m to use pure oxygen to reduce into as calculated
3/ h, the high pressure scrubber cumulative volume of giving vent to anger becomes 1074-169=905m
3/ h, therefore wherein indifferent gas accounts for 69.15%, and oxygen accounts for 16.8%, and combustible gas accounts for 14.05%, makes the B point from Fig. 1, can find out that it also is positioned at outside the explosive range, so high pressure scrubber also is safe.
Adopt after the pure oxygen dehydrogenation gas in the high pressure scrubber as can be seen still in safety range from above checking, but more close flammable range when using the air dehydrogenation, security descends to some extent, therefore stable regulation that must the strengthening process index in operation, Optimizing operation.
2) transform the back effect:
According to design conditions CO2 tolerance 20000m
3/ h; The gas content that hydrogen richness 0.45%, high pressure scrubber are given vent to anger is: NH
3: 8.53%, CO
2: 2.68%, O
2: 14.15%, N
2: 70.97%, CH
4: 3.37%, H
2: 0%, Ar:0.299%, gas gross 1074m
3/ h.
After adopting flow process of the present invention, the employed oxygen of dehydrogenation (20000*0.45% ÷ 2=45m
3/ h) do not use air and use pure oxygen instead, therefore reduce noble gas amounts such as nitrogen (the 45 ÷ 21%*79%=169m of the system that enters
3/ h), so high pressure scrubber emptying amount reduces 169m
3/ h is 1074-169=905m
3/ h.Effectively reduce high-pressure system emptying amount 15.7%, improved the CO2 transformation efficiency, energy-saving and cost-reducing, for increase system loading, raising system throughput provide condition.
Following table 1 is a low pressure absorption tower emptying end gas analytical data, according to data in the table as can be seen urea three transform in the emptying end gas of back hydrogen richness and be 0% and (v), this shows, adopt after the oxygen enrichment dehydrogenation because oxygen content improves, the dehydrogenation effect is remarkable, and hydrogen can remove fully.
Table 1: low pressure tail gas from absorption tower analytical data
As following table 2 is urea production capacity data sheet before and after the three oxygen enrichment dehydrogenations of Yanzhou Coal Mining Lunan Chemical Fertilizer Plant urea come into operation, by the following table data as can be seen, it is 1002.8t/d that urea three adopts the highest production capacity of the preceding system of oxygen enrichment dehydrogenation, coming into operation, production capacity obviously obtains bigger raising after the oxygen enrichment dehydrogenation, the highest urea day output can reach 1266.25t, than improving (1266.25-1002.8)/1002.8=26.3% before coming into operation.
Table 2: rate schedule before and after the oxygen enrichment dehydrogenation is transformed
| Date | Output | Remarks | Date | Output | Remarks |
| April 2 | ??943.4 | Before coming into operation | April 14 | ??1166.5 | After coming into operation |
| April 3 | ??956.5 | Before coming into operation | April 15 | ??1185.5 | After coming into operation |
| April 4 | ??958.8 | Before coming into operation | April 16 | ??1176.95 | After coming into operation |
| April 5 | ??882.8 | Before coming into operation | April 17 | ??1184.4 | After coming into operation |
| April 6 | ??1002.8 | Before coming into operation | April 18 | ??1199.6 | After coming into operation |
| April 7 | ??1010.6 | The morning, 10:28 came into operation | April 19 | ??1196.15 | After coming into operation |
| April 8 | ??1027.7 | After coming into operation | April 20 | ??1114.9 | After coming into operation |
| April 9 | ??1089.05 | After coming into operation | April 21 | ??1212.05 | After coming into operation |
| April 10 | ??1087.5 | After coming into operation | April 22 | ??1212.05 | After coming into operation |
| April 11 | ??1099.2 | After coming into operation | April 23 | ??1266.25 | After coming into operation |
| April 12 | ??1124.35 | After coming into operation | April 24 | ??1184.15 | After coming into operation |
| April 13 | ??1138 | After coming into operation | April 25 | ??1190.8 | After coming into operation |
3) the scheme advantage is discussed
The emptying amount that can effectively reduce high-pressure system after the transformation reaches 15.7%, has improved CO
2Transformation efficiency provides advantageous conditions for system further improves load.
Can find out that according to the our factory real data after the oxygen enrichment dehydrogenation came into operation, daily output urea can increase production 26.3%.
Oxygen flow adopts two to select two mode to measure, and has more effectively guaranteed the accuracy of oxygen flow metering, thereby has guaranteed the oxygen amount that dehydrogenation is required.
Oxygen-rich air is gone into the compressor one section outlet and is used magnetic valve to add, and has more effectively avoided in the reversing process because of a large amount of air of reserve machine pressurization emptying cause the not enough etching apparatus of high-pressure system oxygen level, and the accident that produces red urea takes place.
Adopted safety interlock, when any compressor or air compressor machine jumping car, oxygen intake magnetic valve (XSV-8110) will cut out automatically, has stopped the possibility that oxygen contacts compressor band oil-piping separately, has effectively guaranteed the security in the oxygen use.
Claims (2)
1. the method for dehydrogenating of a CO 2 raw material gas is characterized in that, may further comprise the steps:
1) is that 21～34% oxygen-rich air joins in the feed carbon dioxide gas with oxygen concentration, makes the oxygen level in the feed carbon dioxide gas reach 1.25～1.4%;
2) CO 2 raw material gas of adding oxygen-rich air in compressor carries out smart desulfurization after compression, and total sulfur content is not higher than 0.2ppm after the desulfurization; Gas after the desulfurization is through heat exchange and be heated to 150～200 ℃, enter dehydrogenation reactor then, combustibleconstituents in oxygen and the carbon dioxide is reacted, remove combustibleconstituentss such as hydrogen in the unstripped gas, methane, carbon monoxide, hydrogeneous and other inflammable gas amount＜50PPm in the carbon dioxide after the dehydrogenation;
3) gas after the dehydrogenation enters CO after heat exchange and water cooler are cooled to 36 ℃ ± 4 ℃
2Vapour liquid separator carries out gas-water separation, behind the emptying drop, enters next section of compressor or directly outer confession, is used for the synthetic of urea.
2. the method for dehydrogenating of a kind of CO 2 raw material gas according to claim 1, it is characterized in that: oxygen-rich air obtains after strict measurement is mixed with air by pure oxygen in the described step 1).
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102424384A (en) * | 2011-09-07 | 2012-04-25 | 湖北三宁化工股份有限公司 | Carbon dioxide purification method for urea production |
| CN103673504A (en) * | 2012-09-13 | 2014-03-26 | 湖北三宁化工股份有限公司 | Pressure swing adsorption decarburization gas full-recovery method |
-
2009
- 2009-09-21 CN CN200910018942A patent/CN101654248A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102424384A (en) * | 2011-09-07 | 2012-04-25 | 湖北三宁化工股份有限公司 | Carbon dioxide purification method for urea production |
| CN103673504A (en) * | 2012-09-13 | 2014-03-26 | 湖北三宁化工股份有限公司 | Pressure swing adsorption decarburization gas full-recovery method |
| CN103673504B (en) * | 2012-09-13 | 2016-01-20 | 湖北三宁化工股份有限公司 | A kind of method that pressure swing adsorption decarbonization gas reclaims entirely |
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Open date: 20100224 |