CN104402768A - Technology for producing urea from low-purity liquefied ammonia as raw material - Google Patents
Technology for producing urea from low-purity liquefied ammonia as raw material Download PDFInfo
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- CN104402768A CN104402768A CN201410605700.3A CN201410605700A CN104402768A CN 104402768 A CN104402768 A CN 104402768A CN 201410605700 A CN201410605700 A CN 201410605700A CN 104402768 A CN104402768 A CN 104402768A
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Abstract
The invention belongs to the technical field of urea production and especially relates to a technology for producing urea from low-purity liquefied ammonia as a raw material. The technology comprises that urea is produced from low-purity liquefied ammonia and qualified CO2 as raw materials by a carbon dioxide gas stripping method and the low-purity liquefied ammonia has a mass concentration of 85-95%. The technology solves the problem that the existing urea production technology has high requirements on raw material purity, realizes treatment on impure liquefied ammonia in the operation initial stage of a large-scale synthetic ammonia and urea production device, effectively reduces an enterprise test run cost and forms a device process as early as possible.
Description
Technical field
The invention belongs to technical field of urea production, particularly a kind of low-purity liquefied ammonia is the technique of raw material production urea.
Background technology
Urea production process mainly contains the CO of Dutch Stamicarbon (Stamicarbon) company
2air-extraction technique and liquid structure process unit, Italian Si Namupuji carry ammonia stripping process technique, the energy-saving low cost ACES technique of Mitsui east engineering (TEC/MTC) company of pressure/Japan, the modified form CO of the forth academy of change the earliest production domesticization of (Snamprogetti) company
2air-extraction technique etc.But the current purity of all technique to raw material has comparatively strict requirement, as raw material CO
2require that purity is not less than 98.5%, total sulfur is not higher than 10ppm, H
2not higher than 0.1%, liquefied ammonia NH
3purity is not less than 99.5%, and oil-contg is not higher than 10ppm.Two kinds of raw materials are carried out the techniques such as pressure synthesis, recovery, evaporation concentration to carry out material balance, technological design production urea.Current technique is very ripe, but higher to ingredient requirement, and not reaching ingredient requirement is do not allow start-of-run.Therefore there is no at present and adopt the liquefied ammonia lower than 99.5% purity to be that raw material carries out start-of-run production urea.
Secondly, its production line of enterprise producing urea is often also maintained close ties with Ammonia Production line, and often enterprise self just builds synthetic ammonia installation.Go into trial production in process at synthetic ammonia installation, when marching to the heating reduction flow process of synthetic tower catalyzer, catalyst reduction produces a large amount of ammoniacal liquor, because device list tower throughput is larger, the synthetic tower revivification of catalyst time is longer, the ammoniacal liquor produced is more, and this ammonia concn, between 85-90%, does not reach the ingredient requirement of urea production.But because amount does not have spatial manipulation more greatly, and the storage power of spherical tank is limited, ensures that ammonia synthesizer test run flow process is got through and continue to advance, just needs to concentration a large amount of herein lower than 99.5% ammoniacal liquor process.Otherwise the test run of ammonia synthesizer will face parking, loss will be very large.
Summary of the invention
The object of this invention is to provide the technique that a kind of low-purity liquefied ammonia is raw material production urea, the defect that existing technique is higher to ingredient requirement can be improved, sale and the process problem of Mass Synthetic Ammonia Unit synthesizer heating reduction and product ammonia initial stage a large amount of impure liquefied ammonia in initial start-up can be solved again, greatly reduce the test run cost of enterprise.
For solving the problems of the technologies described above, the technical solution used in the present invention is as follows:
Low-purity liquefied ammonia is a technique for raw material production urea, with low-purity liquefied ammonia and qualified CO
2gas is that raw material adopts carbon dioxide stripping their to produce urea, and described low-purity liquid ammonia quality concentration is 85-95%.
Wherein, low-purity liquefied ammonia and carbonic acid gas carry out original feeding intake according to the amount of ammonia carbon species than for 3.0-3.3:1, and the purity of carbonic acid gas is 97%.
Preferably, the flow of original low-purity liquefied ammonia, carbonic acid gas when feeding intake calculates according to the 60-70% producing load.
Preferably, in production process, in Controlling System, water is 0.6-0.9:1 with the amount of substance ratio of carbonic acid gas.
In above-mentioned production process in Controlling System the ratio of water and carbonic acid gas refer to the process that feeds intake neutralize feed intake after the Con trolling index of water in normal course of operation and carbonic acid gas.
Preferably, the original 25-30% of rotating speed at maximum opening controlling metro-methylamine pump when feeding intake; Ammonia pump rotating speed is at the 85-90% of maximum opening.Concrete rotating speed carries out Theoretical Calculation draw according to ammonia pump, metro-methylamine pump device parameter.
Preferably, control following parameter in the reasonable scope before discharging after feeding intake: Gao Jialeng go out liquid temp 155-160 DEG C, ammonia spray temperature at 125-130 DEG C, to a high-profile water temperature difference at 10-15 DEG C; In addition, before discharging system pressure not higher than 12.5Mpa.
Preferably, can by adjustment ammonia carbon ratio, steam/hydrocarbons ratio goes out liquid temp to Gao Jialeng, ammonia spray temperature, to a high-profile water temp control.
Wherein, if original raw material proportioning ammonia carbon ratio is high, then to go out liquid temp low for Gao Jialeng, and high-pressure climbing speed is comparatively slow; If ammonia carbon ratio is low, then first cold go out liquid temp high, whether high-pressure climbing speed more hurry up, therefore can carry out the adjustment of original ammonia carbon ratio, to realize slowly raising with pressure raised temperature between 155-160 DEG C according to temperature.
Ammonia spray temperature: general temperature controls between 125-130 DEG C, when feeding intake amount of water under the minimum frequency conversion of metro-methylamine pump, ammonia spray temperature higher than this temperature, then illustrates that original charge ratio ammonia carbon ratio is low, otherwise lower than this temperature, ammonia spray temperature then illustrates that original charge ratio ammonia carbon ratio is high.
Water temperature difference is between 10-15 degree to a high-profile, and ammonia carbon ratio is the core of whole charge ratio, and ammonia carbon ratio is high or low, and the top backwater temperature difference of high water transfer all can reduce, and general original charge ratio is normal, departs from this temperature difference ammonia carbon ratio proportioning just abnormal, needs to adjust in time.
Observe the rate of pressure rise of high-pressure system, high-pressure system pressure has individual stable region at 11-11.5MPa pressure, the not super 12.5MPa of system pressure before control discharging.
Preferably, the synthetic tower controlling high-pressure system after discharging goes out fluid component steam/hydrocarbons ratio at 0.6-0.9, and ammonia carbon ratio is 3.0-3.3.
The routine techniques means that the above-mentioned means carrying out adjusting control to steam/hydrocarbons ratio, ammonia carbon ratio are grasped for those skilled in the art, repeat no more herein.
Preferably, before driving, lp system, hydrolyzing and desorbing system are transformed.
Concrete, increase low pressure and to meet an urgent need emptying, hydrolyzing and desorbing system increases emergent emptying.
Concrete, lp system is the pipeline and the valve that the gas phase pipeline before entering low pressure Carbamate Condenser increase emptying; Hydrolyzing and desorbing system is that the gas phase pipeline before entering reflux exchanger increases valve and pipeline, and object is all steam/hydrocarbons ratio in order to maintain high-pressure system and ammonia carbon ratio.
When system in production occurs unstable, the imbalance of ammonia carbon ratio, steam/hydrocarbons ratio makes NH in ammonia vessel
3and CO
2when content raises, ensure that the content sending decomposition of effluent ammonia and urea outside is less than 10ppm, need decrement that ammonia vessel liquid level is gone up, concentration must continue to raise, whole system continues to worsen, now desorb overload, cause lp system cannot absorb high-pressure system cannot consume again, when whole system is difficult to adjustment, the emergent blow-off valve of lp system is conveniently adjusted, can the suitable a part of gas desorbed of emptying, reduce the condensation number of reflux exchanger, thus reduce the load of desorb, to ensure that ammonia vessel liquid level declines, concentration reduces.Need again just can to open during the row's of parking tower hydrolysis desorption system to meet an urgent need a part of desorb water solution of the suitable emptying of blow-off valve gas out when accident tank liquor position is high, thus drag down the liquid level of accident groove, solve the difficult problem cannot arranging tower displacement because accident tank liquor position is high, and avoid too high and overflow the occurs ammonia nitrogen of ammonia vessel or accident tank liquor position to exceed standard environmental protection accident.
The present invention combines reality of driving, and with carbon dioxide stripping their urea initial start-up scheme in the past for foundation, carrying out bold trial and operation, take purity as the liquefied ammonia of 85-95% and qualified CO
2gas is that raw material carries out start-of-run, and through attempting and groping to achieve successfully.The present invention carries out theoretical calculating to the proportional quantity of original feed intake liquefied ammonia and carbonic acid gas emphatically; In the process of feeding intake, the adjustment of the proportional quantity of liquefied ammonia and carbonic acid gas is preferably carried out according to the change such as temperature, pressure.In addition, after discharging, whole high pressure water balance, ammonia carbon ratio are carried out to adjustment and controlled, this adjustment controls more useful for the carrying out of whole technique.3rd, also preferred driving early stage some little transformations have been carried out to lp system, hydrolyzing and desorbing system.
The present invention also has following meaning:
Although the activity after ammonia synthesis converter catalyst reduction is relevant with the type selecting of catalyzer, the reduction success or not of catalyzer plays vital impact by the activity of catalyzer.Therefore, the reduction of catalyzer is always that synthesis ammonia plant to produce in startup procedure an important link.The slow heating reduction of safety and stability is crucial, therefore the reduction catalysts time operating to synthesis ammonia system ammonia of the follow-up system of the present invention's realization provides guarantee, and the process problem of impure liquefied ammonia of need not worrying again, solves trouble and worry.
Compared with prior art, tool has the following advantages in the present invention:
First the present invention solves current urea production process to the too high defect of material purity requirement, also effectively solve the process problem of Mass Synthetic Ammonia Unit at the impure liquefied ammonia at test run driving initial stage simultaneously, effectively reduce the test run cost of enterprise, the flow process of getting through device as early as possible.
Accompanying drawing explanation
Fig. 1 is the transformation schematic diagram of lp system, and add low pressure and to meet an urgent need blow-down pipe, 1 is low pressure carbamate condenser.
Fig. 2 is the transformation of desorption and hydrolysis system, and add desorb and to meet an urgent need blow-down pipe, 2 is reflux exchanger.
Embodiment
With specific embodiment, technical scheme of the present invention is described below, but protection scope of the present invention is not limited thereto:
Embodiment 1
1. original liquefied ammonia and the CO of feeding intake
2
proportional quantity Theoretical Calculation process is as follows:
To adopt certain company of 500kt/a synthetic ammonia and supporting urea engineering, adopt domestic modified form CO
2air-extraction technique, its small particles device (urea product granularity is at 0.85-2.8mm) two overlaps, and macrobead device (urea product granularity is at 2-4mm) is a set of, often overlaps equal 400,000 tons/year of throughput, be production 55.6t urea per hour according to 100% load, enter system CO
2purity be 97%, five go out that (five go out to refer to raw material CO
2the gas of gas after compressor compresses, this compressor is 5 sections of compressions, five sections outlet compression high pressure gas enter high-pressure synthesis tower building-up reactions produce urea) CO
2flow is that production 1 ton of urea theory needs 372/0.97=384 m
3/ h, needs 400 m by 1 ton of urea during actual operation
3/ h calculates:
1) CO that goes out of 100% load five
2flow is 55.6 × 400=22240 m
3/ h.
2) Theoretical Calculation goes out the CO that 70% load five goes out
2flow is 55.6 × 400 × 70%=15568 m
3/ h.
3) Theoretical Calculation goes out the CO that 70% load five goes out
2flow is 15568 m
3/ h, needs the flow throwing ammonia:
According to n
nH3/ n
co2=3.1 calculate, n
nH3=n
co2× 3.1
n
co2=V/V
m=15568×0.97/22.4=674150mol
n
NH3=674150×3.1=2089865mol
m
NH3= nM
NH3=2089865×17=35527.705Kg
V
nH3=m/ density=35527.705/638=55.7 m
3
4) Theoretical Calculation goes out the CO that 70% load five goes out
2flow is 15568 m
3/ h, the flow of the water that need additionally add:
According to nH
2o/nCO
2be 0.7 calculating, nH
2o=nCO
2× 0.7
nCO
2=V/Vm=15568×97%/22.4=674150mol
nH
2O= nCO
2×0.7=674150×0.7=471900mol
mH
2O= nH2O×18=8494.2kg
VH
2O=8.494 m
3/h
5) calculating of pump amount and rotating speed
Metro-methylamine pump parameter: diameter of plunger 94mm, stroke 150mm, three pedestal plugs;
The flow (combination valve does not leak) that metro-methylamine pump bent axle often rotates a circle can be calculated:
V=3.14x(0.094/2)
2x0.15*3=0.00312m
3
If the revolution of bent axle per minute is that Y turns under the minimum frequency conversion of metro-methylamine pump, then metro-methylamine pump look up and down (water yield namely needing to add system) hourly is=0.00312xYx60
Ammonia pump parameter: diameter of plunger 105mm, stroke 180mm, three pedestal plugs;
The flow (combination valve does not leak) that ammonia pump bent axle often rotates a circle can be calculated:
V=3.14x(0.105/2)
2x0.18*3=0.00467m
3
If the revolution of bent axle per minute is that Z turns under the minimum frequency conversion of ammonia pump
Ammonia pump is hourly to be looked up and down as=0.00467xZx60
Can show roughly that original start-of-run proportioning table is as follows:
2. concrete operations:
1) after ammonia pump drops into synthesis system, vapo(u)rization system and hydrolyzing and desorbing start preheating;
2) to feed intake calculating with 70% load, discharging in about 135 minutes, normal design flow (normal design flow when producing 70% load of 400,000 tons of urea plants per year is 42t/h) when first 15 minutes of discharging is increased to 70% load the total flux that 2.5MPa steam enters device, progressively open the control valve opening that large 2.5Mpa steam enters high voltage package, 2.5mpa steam is made to enter the flow of high voltage package slightly larger than steam consumption 50t/h during production load, unnecessary use high voltage package emptying variable valve emptying.After synthetic tower liquid level reaches 70%, progressively open large synthetic tower liquid-outlet valve control synthetic tower liquid level 50%.
3) in, control turns down high voltage package emptying variable valve immediately, regulates 2.5Mpa steam to enter the variable valve of high voltage package, high voltage package pressure is increased to 1.7Mpa, and ensures that 2.5Mpa steam enters high voltage package stability of flow.When high voltage package liquid level height, notice patrols and examines out trip valve before and after high voltage package fluid, liquid level is drained into middle pressure bag.
4) stripping tower liquid level is 80% time, opens large gas stripping column liquid-outlet valve gradually and is fed to rectifying tower, and middle control regulates low-key water temp, after there is the temperature difference, low-key water inlet temperature control 55-60 DEG C is dropped into automatic control.
5) low pressure bag pressure power is reduced a little after synthetic tower display liquid level, notice is patrolled and examined and is closed the aeration valve of middle pressure steam to High Pressure Carbamate Condenser shell-side, after synthetic tower fluid is opened, low pressure bag pressure power is down to technic index, after stripping tower (gas stripping column steam, brings load) working properly, middle control regulates ammonia pump frequency conversion, slowly fall into system ammonia amount, NH
3/ CO
2be down to 2.1 ~ 2.3.
6) with the good lp system pressure of low pressure governor valve control, superpressure is strictly on guard against.Optionally progressively shut low pressure to meet an urgent need emptying, regulate low pressure at 0.25MPa.
7) under washing device according to height, high water transfer is proceeded to bottom cycle well heater by liquid temp gradually, and under in the process turned, height washes device, liquid temp is not less than 160 DEG C, shuts water jacket steam valve to a high-profile afterwards.
8) regulate the steam valve into top recirculation heater, what control rectifying tower goes out liquid temp at 130-135 DEG C, and rectifying tower level stability throws automatic control 15%.
9), during gas stripping column consumption steam, adjustment 2.5Mpa steam enters the variable valve of middle pressure bag in time, makes pressure-stabilisation at 0.8Mpa, prevents middle pressure steam superpressure.
10) according to circulatory system pressure and ammonium carbamate concentration, adjust in time into the system water yield, NH3 amount, ammonium carbamate concentration is: NH
3: 29.4%, CO
2: 35.5%, H
2o:34.8%.
11) note the quantity of circulating water regulating flash drum condenser, regulate flashing pressure 0.045Mpa, under keeping flash distillation, liquid temp is at 91-95 DEG C.
12) synthetic tower normal after, synthetic tower liquid level, gas stripping column Liquid level is normal, and stable system pressure, adjusts each parameter to technic index value.
drive by this proportioning raw materials, eventually pass through adjustment and grope to reach continuous operation, produce qualified urea product, quality product is total nitrogen content 46.2%, contracting two urine 1.2%, moisture 0.5%, create condition to front system synthesis ammonia device heating reduction simultaneously, also the impure liquefied ammonia at the initial stage of driving is consumed, solve selling pressure, in advance whole whole audience device is got through simultaneously comprehensively.
Claims (9)
1. be a technique for raw material production urea with low-purity liquefied ammonia, it is characterized in that, with low-purity liquefied ammonia and qualified CO
2gas is that raw material adopts carbon dioxide stripping their to produce urea, and described low-purity liquid ammonia quality concentration is 85-95%.
2. be the technique of raw material production urea as claimed in claim 1 with low-purity liquefied ammonia, it is characterized in that, low-purity liquefied ammonia and carbonic acid gas carry out original feeding intake according to the amount of ammonia carbon species than for 3.0-3.3, and the purity of carbonic acid gas is 97%.
3. be the technique of raw material production urea as claimed in claim 2 with low-purity liquefied ammonia, it is characterized in that, in production process, in Controlling System, water is 0.6-0.9 with the amount of substance ratio of carbonic acid gas.
4. the use low-purity liquefied ammonia as described in as arbitrary in claim 1-3 is the technique of raw material production urea, it is characterized in that, the flow of original low-purity liquefied ammonia, carbonic acid gas when feeding intake calculates according to the 60-70% producing load.
5. as claimed in claim 4 is the technique of raw material production urea with low-purity liquefied ammonia, it is characterized in that, original when feeding intake the rotating speed of metro-methylamine pump control the 25-30% of the maximum opening at pump; Ammonia pump rotating speed controls the 85-90% of the maximum opening at pump.
6. be the technique of raw material production urea as claimed in claim 4 with low-purity liquefied ammonia, it is characterized in that, after feeding intake, control following parameter in the reasonable scope before discharging: Gao Jialeng go out liquid temp 155-160 DEG C, ammonia spray temperature at 125-130 DEG C, to a high-profile water temperature difference at 10-15 DEG C; In addition, before discharging system pressure not higher than 12.5Mpa.
7. be the technique of raw material production urea as claimed in claim 6 with low-purity liquefied ammonia, it is characterized in that, the synthetic tower controlling high-pressure system after discharging goes out the steam/hydrocarbons ratio of fluid component at 0.6-0.9, and ammonia carbon ratio is 3.0-3.3.
8. be the technique of raw material production urea as claimed in claim 4 with low-purity liquefied ammonia, it is characterized in that, before driving, lp system, hydrolyzing and desorbing system are transformed.
9. as claimed in claim 8 is the technique of raw material production urea with low-purity liquefied ammonia, it is characterized in that, lp system increases low pressure and to meet an urgent need emptying, and hydrolyzing and desorbing system increases emptying of meeting an urgent need.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410605700.3A CN104402768B (en) | 2014-11-03 | 2014-11-03 | A kind of low-purity liquefied ammonia is the technique of raw material production carbamide |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410605700.3A CN104402768B (en) | 2014-11-03 | 2014-11-03 | A kind of low-purity liquefied ammonia is the technique of raw material production carbamide |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN104402768A true CN104402768A (en) | 2015-03-11 |
| CN104402768B CN104402768B (en) | 2016-10-05 |
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|---|---|---|---|
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Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1100412A (en) * | 1993-09-16 | 1995-03-22 | 中国化学工程总公司 | Stripping recirculation technology & apparatus for urea production |
-
2014
- 2014-11-03 CN CN201410605700.3A patent/CN104402768B/en active Active
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1100412A (en) * | 1993-09-16 | 1995-03-22 | 中国化学工程总公司 | Stripping recirculation technology & apparatus for urea production |
Non-Patent Citations (2)
| Title |
|---|
| 王付生: "浅析CO2汽提法尿素装置合成系统的NH3/CO2", 《化工设计通讯》 * |
| 谢群力 等: "CO2汽提法尿素装置改造及运用小结", 《化工设计通讯》 * |
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