Urea system flush evaporative flush method and apparatus

Abstract

The present application relates to the technical field of urea production, and is a urea system flushing evaporation flushing method and device. The urea system flushing evaporation flushing method pre-raises the temperature of the evaporation system before flushing, prevents excessive crystalline substances from blocking the pipeline by intermittently flushing the relevant parts of the second-stage evaporation separator, the top gas phase pipeline of the second-stage evaporation separator, the first-stage evaporation separator and the top gas phase pipeline of the first-stage evaporation separator, ensures that the urea evaporation system runs more stably, and recovers ammonia and other substances in the gas phase separated by evaporation after condensation to reduce the emission of pollutants. The present application has a reasonable and compact structure, a simple process, simple operation, low equipment cost, conforms to the development concept of environmental protection and resource utilization, not only makes the urea product meet the national standard GB2440-2017, but also makes the evaporation system run more stably.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of urea production, and is a urea system flash evaporation flushing method and device. BACKGROUND

[0002] Urea is an important chemical product and is widely used in agriculture, chemical industry, medicine and other fields. In the current urea production process, the evaporation system is an indispensable subsystem for purifying high-concentration molten urea liquid.

[0003] In actual production, the mixed gas containing ammonia, carbon dioxide, water and urea separated by the evaporation system is prone to form crystalline substances in the pipeline / equipment, block the pipeline, reduce the evaporation vacuum degree, and thus affect the safe and stable operation of the evaporation system.

[0004] Therefore, it is necessary to intermittently flush the relevant parts to prevent the formation of excessive crystalline substances, and to recover ammonia and other substances in the gas phase separated by the evaporation after condensation to reduce the emission of pollutants. This not only makes the urea product meet the national standard GB2440-2017, but also makes the evaporation system run more stably. SUMMARY

[0005] The present application provides a urea system flash evaporation device, which overcomes the shortcomings of the prior art and effectively solves the problems of excessive crystallization and pipeline blockage in urea production.

[0006] One of the technical solutions of the present application is achieved by the following measures: a urea system flash evaporation flushing method is performed according to the following method: first, adjust the temperature of the urea evaporation system; second, open the first automatic valve and the second automatic valve in turn to introduce the flushing water to the front of the first flushing total valve and the second flushing total valve; third, open the second flushing total valve and open the seventh flushing automatic valve, the eighth flushing automatic valve and the ninth flushing automatic valve in turn to flush the top of the second evaporation separator; fourth, check that the seventh flushing automatic valve, the eighth flushing automatic valve and the ninth flushing automatic valve are all closed, open the tenth flushing automatic valve, the eleventh flushing automatic valve and the twelfth flushing automatic valve in turn to flush the elbow of the second gas phase pipeline; fifth, open the first flushing total valve and open the first flushing automatic valve, the second flushing automatic valve and the third flushing automatic valve in turn to flush the top of the first evaporation separator; sixth, check that the first flushing automatic valve, the second flushing automatic valve and the third flushing automatic valve are all closed, open the fourth flushing automatic valve, the fifth flushing automatic valve and the sixth flushing automatic valve in turn to flush the first gas phase pipeline; seventh, repeat the above steps two to six in turn twice; eighth, close the first automatic valve, open the third automatic valve, drain the remaining flushing water in the pipeline, and close the second automatic valve and the third automatic valve; ninth, adjust the temperature of the first evaporation heater and the temperature of the second evaporation heater to the index control range.

[0007] The following is a further optimization or / and improvement of one of the above technical solutions of the invention:

[0008] In the first step, the temperature of the first evaporation heater is increased from 125 DEG C to 126.5 DEG C to 130 DEG C to 132.5 DEG C, and the temperature of the second evaporation heater is increased from 134.5 DEG C to 135.5 DEG C to 139.5 DEG C to 141.5 DEG C.

[0009] In the third step, the flushing time of each place is 10s to 15s; in the fourth step, the flushing time of each place is 15s to 30s; in the fifth step, the flushing time of each place is 3s to 5s; and in the sixth step, the flushing time of each place is 15s to 30s.

[0010] In the ninth step, the temperature index control range of the first evaporation heater is 125 DEG C to 126.5 DEG C, and the temperature index control range of the second evaporation heater is 134.5 DEG C to 135.5 DEG C.

[0011] The second technical solution of the present application is realized by the following measures: a device for implementing the above-mentioned urea system flushing evaporation flushing method, comprising a urea liquid tank, a first evaporation heater, a first evaporation separator, a second evaporation heater, a second evaporation separator, a first evaporation surface condenser, a second evaporation surface condenser, and an ammonia tank, wherein the bottom outlet of the urea liquid tank is fixedly connected with the inlet of the first evaporation heater through a first urea liquid pipeline, the top outlet of the first evaporation heater is fixedly connected with the upper inlet of the first evaporation separator through a second urea liquid pipeline, the bottom outlet of the first evaporation separator is fixedly connected with the upper inlet of the second evaporation heater through a third urea liquid pipeline, the top outlet of the second evaporation heater is fixedly connected with the upper inlet of the second evaporation separator through a fourth urea liquid pipeline, the bottom outlet of the second evaporation separator is fixedly connected with a urea pipeline, the top outlet of the first evaporation separator is fixedly connected with the upper inlet of the first evaporation surface condenser through a first gas phase pipeline, the top outlet of the second evaporation separator is fixedly connected with the upper inlet of the second evaporation surface condenser through a second gas phase pipeline, the bottom outlet of the first evaporation surface condenser is fixedly connected with the ammonia tank through a first ammonia pipeline, and the bottom outlet of the second evaporation surface condenser is fixedly connected with the first ammonia pipeline through a second ammonia pipeline.

[0012] The following is a further optimization or / and improvement of the second technical solution of the above invention:

[0013] The top inlet of the above-mentioned first-stage evaporation separator is fixedly connected with a first flushing water pipeline, the water inlet of the first flushing water pipeline is fixedly connected with a flushing water pipe, the first flushing water pipeline and the first gas phase pipeline are fixedly connected with a second flushing water pipeline, the first flushing water pipeline between the flushing water pipe and the second flushing water pipeline is fixedly connected with a third flushing water pipeline and the top inlet of the second-stage evaporation separator, and the third flushing water pipeline is fixedly connected with the second gas phase pipeline.

[0014] A urine pump is fixedly installed on the above-mentioned first urea liquid pipeline, a melting pump is fixedly installed on the urea pipeline, a first sight glass is fixedly installed on the third urea liquid pipeline, a second sight glass is fixedly installed on the urea pipeline between the second-stage evaporation separator and the melting pump, and a shower guide line is fixedly connected to the first flushing water pipeline between the third flushing water pipeline and the flushing jellyfish pipe.

[0015] The outlets of the first flushing water pipeline between the second flushing water pipeline and the top of the first-stage evaporation separator and the third flushing water pipeline between the fourth flushing water pipeline and the top of the second-stage evaporation separator are both provided with three branch pipelines. The three branch pipelines at the outlet of the first flushing water pipeline are all fixedly connected to the top of the first-stage evaporation separator, and the three branch pipelines at the outlet of the third flushing water pipeline are all fixedly connected to the top of the second-stage evaporation separator. A fifth flushing water pipeline is fixedly connected between the second flushing water pipeline and the first gas phase pipeline, a sixth flushing water pipeline is fixedly connected between the fifth flushing water pipeline and the second flushing water pipeline outlet and the first gas phase pipeline, a seventh flushing water pipeline is fixedly connected between the fourth flushing water pipeline and the second gas phase pipeline, and an eighth flushing water pipeline is fixedly connected between the seventh flushing water pipeline and the fourth flushing water pipeline outlet and the second gas phase pipeline.

[0016] The first flushing water line between the flushing water pipe and the drainage line is respectively provided with a first automatic control valve and a second automatic control valve according to the flow direction of the medium. The drainage line is fixed with a third automatic control valve. The first flushing water line between the second flushing water line and the third flushing water line is fixed with a first-stage flushing main valve. The third flushing water line between the first flushing water line and the fourth flushing water line is fixed with a second-stage flushing main valve. The first flushing automatic control valve, the second flushing automatic control valve and the third flushing automatic control valve are respectively fixed on the branch lines of the first flushing water line. The sixth flushing water line is fixed with The fourth flushing automatic control valve, the fifth flushing automatic control valve is fixedly arranged on the second flushing water pipeline between the sixth flushing water pipeline and the first gas phase pipeline, the sixth flushing automatic control valve is fixedly arranged on the fifth flushing water pipeline, the seventh flushing automatic control valve, the eighth flushing automatic control valve and the ninth flushing automatic control valve are fixedly arranged on the branch pipelines of the third flushing water pipeline respectively, the tenth flushing automatic control valve is fixedly arranged on the seventh flushing water pipeline, the eleventh flushing automatic control valve is fixedly arranged on the eighth flushing water pipeline, and the twelfth flushing automatic control valve is fixedly arranged on the fourth flushing water pipeline between the eighth flushing water pipeline and the first gas phase pipeline.

[0017] The above-mentioned urea system flushing and evaporation device also includes a DCS controller, and the urine pump, melt pump, first automatic control valve, second automatic control valve, third automatic control valve, first stage flushing main valve, second stage flushing main valve and first flushing automatic control valve to twelfth automatic control valve are all electrically connected to the DCS controller.

[0018] The urea system flushing evaporation device of the present invention adopts a simple and effective method and has a reasonable and compact structure. By intermittently flushing relevant parts of the evaporation system, the formation of excessive crystals that block the pipeline is prevented, ensuring that the urea evaporation system operates more stably. At the same time, the gas phase separated by evaporation is condensed and ammonia and other substances therein are recovered, thereby reducing the emission of pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Attachment Figure 1 Schematic diagram of the process flow of the best embodiment 5 of the present invention.

[0020] The codes in the accompanying drawings are: 1 is a urea liquid tank, 2 is a first-stage evaporation heater, 3 is a first-stage evaporation separator, 4 is a second-stage evaporation heater, 5 is a second-stage evaporation separator, 6 is a first-stage evaporation surface condenser, 7 is a second-stage evaporation surface condenser, 8 is an ammonia tank, 9 is a urine pump, 10 is a melt pump, 11 is a first urea liquid pipeline, 12 is a second urea liquid pipeline, 13 is a third urea liquid pipeline, 14 is a fourth urea liquid pipeline, 15 is a urea pipeline, 16 is a first gas phase pipeline, 17 is a first ammonia pipeline, 18 is a second gas phase pipeline, 19 is a second ammonia pipeline, 20 is a flushing water pipe, 21 is a first flushing water pipeline, 22 is a second flushing water pipeline, 23 is a third flushing water pipeline, 24 is a fourth flushing water pipeline, 25 is a urea pipeline, For the shower line, 26 is the first automatic control valve, 27 is the second automatic control valve, 28 is the third automatic control valve, 29 is the first stage flushing main valve, 30 is the second stage flushing main valve, 31 is the first flushing automatic control valve, 32 is the second flushing automatic control valve, 33 is the third flushing automatic control valve, 34 is the fourth flushing automatic control valve, 35 is the fifth flushing automatic control valve, 36 is the sixth flushing automatic control valve, 37 is the seventh flushing automatic control valve, 38 is the eighth flushing automatic control valve, 39 is the ninth flushing automatic control valve, 40 is the tenth flushing automatic control valve, 41 is the eleventh flushing automatic control valve, 42 is the twelfth flushing automatic control valve, 43 is the first sight glass, 44 is the second sight glass, 45 is the fifth flushing water pipeline, 46 is the sixth flushing water pipeline, 47 is the seventh flushing water pipeline, and 48 is the eighth flushing water pipeline. DETAILED DESCRIPTION

[0021] The present invention is not limited to the following embodiments, and specific implementation methods can be determined based on the technical solutions of the present invention and actual conditions. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all chemical reagents and chemicals known and used in the prior art.

[0022] The present invention will be further described below in conjunction with the embodiments:

[0023] Example 1: A method for flushing urea system evaporation is performed according to the following steps: the first step is to adjust the temperature of the urea evaporation system to prevent the evaporation system temperature from dropping suddenly due to the flushing water entering the evaporation system, thereby causing the molten urine to crystallize; the second step is to open the first automatic control valve 26 and the second automatic control valve 27 in sequence to guide the flushing water to the front of the first flushing main valve 29 and the second flushing main valve 30; the third step is to open the second flushing main valve 30, and open the seventh flushing automatic control valve 37, the eighth flushing automatic control valve 38, and the ninth flushing automatic control valve 39 in sequence to flush the top of the second-stage evaporation separator 5; the fourth step is to check that the seventh flushing automatic control valve 37, the eighth flushing automatic control valve 38, and the ninth flushing automatic control valve 39 are all closed, and open the tenth flushing automatic control valve 40, the eleventh flushing automatic control valve 41, and the twelfth flushing automatic control valve 42 in sequence to flush the second Flush the elbow of the gas phase pipeline 18; the fifth step, open the first flushing main valve 29, open the first flushing automatic control valve 31, the second flushing automatic control valve 32, and the third flushing automatic control valve 33 in sequence to flush the top of the first stage evaporation separator 3; the sixth step, check that the first flushing automatic control valve 31, the second flushing automatic control valve 32, and the third flushing automatic control valve 33 are all closed, open the fourth flushing automatic control valve 34, the fifth flushing automatic control valve 35, and the sixth flushing automatic control valve 36 in sequence to flush the first gas phase pipeline 16; the seventh step, repeat the above second to sixth steps twice in sequence; the eighth step, close the first automatic control valve 26, open the third automatic control valve 28, drain the remaining flushing water, and close the second automatic control valve 27 and the third automatic control valve 28; the ninth step, adjust the temperature of the first stage evaporation heater and the temperature of the second stage evaporation heater to the index control range.

[0024] As needed, when large pieces of crystal material are observed falling, the flushing can be suspended until the crystal material is dissolved, and then the flushing can be continued; or the flushing time can be shortened, the flushing times can be increased, and flushing can be performed in small amounts and multiple times.

[0025] Example 2, as an optimization of the above example, in the first step, the temperature of the first stage evaporation heater is increased from 125°C to 126.5°C to 130°C to 132.5°C, and the temperature of the evaporation system of the second stage evaporation heater is increased from 134.5°C to 135.5°C to 139.5°C to 141.5°C.

[0026] Example 3, as an optimization of the above example, in the third step, the flushing time at each location is 10s to 15s; in the fourth step, the flushing time at each location is 15s to 30s; in the fifth step, the flushing time at each location is 3s to 5s; in the sixth step, the flushing time at each location is 15s to 30s.

[0027] Example 4, as an optimization of the above example, in the ninth step, the temperature index control range of the first stage evaporation heater is 125°C to 126.5°C, and the temperature index control range of the second stage evaporation heater is 134.5°C to 135.5°C.

[0028] Example 5: As shown in the attached Figure 1 As shown, the device for implementing the urea system evaporation flushing method includes a urea liquid tank 1, a first stage evaporation heater 2, a first stage evaporation separator 3, a second stage evaporation heater 4, a second stage evaporation separator 5, a first stage evaporation surface condenser 6, a second stage evaporation surface condenser 7, and an ammonia water tank 8. A first urea liquid pipeline 11 is fixedly connected between the bottom outlet of the urea liquid tank 1 and the inlet of the first stage evaporation heater 2, a second urea liquid pipeline 12 is fixedly connected between the top outlet of the first stage evaporation heater 2 and the upper inlet of the first stage evaporation separator 3, a third urea liquid pipeline 13 is fixedly connected between the bottom outlet of the first stage evaporation separator 3 and the upper inlet of the second stage evaporation heater 4, and the second stage evaporation heater 4 is fixedly connected to the first stage urea liquid pipeline 14. A fourth urea liquid pipeline 14 is fixedly connected between the top outlet of the heat exchanger 4 and the upper inlet of the second-stage evaporation separator 5, a urea pipeline 15 is fixedly connected to the bottom outlet of the second-stage evaporation separator 5, a first gas phase pipeline 16 is fixedly connected between the top outlet of the first-stage evaporation separator 3 and the upper inlet of the first-stage evaporation surface condenser 6, a second gas phase pipeline 18 is fixedly connected between the top outlet of the second-stage evaporation separator 5 and the upper inlet of the second-stage evaporation surface condenser 7, a first ammonia aqueous pipeline 17 is fixedly connected between the bottom outlet of the first-stage evaporation surface condenser 6 and the ammonia aqueous tank 8, and a second ammonia aqueous pipeline 19 is fixedly connected between the bottom outlet of the second-stage evaporation surface condenser 7 and the first ammonia aqueous pipeline 17.

[0029] The above device can be further optimized and / or improved according to actual needs:

[0030] Example 6: As an optimization of the above embodiment, as shown in the attached Figure 1 As shown, the top inlet of the first-stage evaporation separator 3 is fixedly connected to a first flushing water pipeline 21, the water inlet of the first flushing water pipeline 21 is fixedly connected to a flushing water pipe 20, the first flushing water pipeline 21 and the first gas phase pipeline 16 are fixedly connected to a second flushing water pipeline 22, the first flushing water pipeline 21 between the flushing water pipe 20 and the second flushing water pipeline 22 and the top inlet of the second-stage evaporation separator 5 is fixedly connected to a third flushing water pipeline 23, and the third flushing water pipeline 23 and the second gas phase pipeline 18 are fixedly connected to a fourth flushing water pipeline 24.

[0031] Example 7: As an optimization of the above embodiment, as shown in the attached Figure 1 As shown, a urine pump 9 is fixedly installed on the first urea liquid pipeline 11, a melt pump 10 is fixedly installed on the urea pipeline 15, a first sight glass 43 is fixedly installed on the third urea liquid pipeline 13, a second sight glass 44 is fixedly installed on the urea pipeline 15 between the second-stage evaporation separator 5 and the melt pump 10, and a shower guide line 25 is fixedly connected to the first flushing water pipeline 21 between the third flushing water pipeline 23 and the flushing water pipe 20.

[0032] Example 8: As an optimization of the above embodiment, as shown in the attached Figure 1 As shown, the outlets of the first flushing water line 21 between the second flushing water line 22 and the top of the first stage evaporation separator 3 and the third flushing water line 23 between the fourth flushing water line 24 and the top of the second stage evaporation separator 5 are each provided with three branch pipelines. The three branch pipelines at the outlet of the first flushing water line 21 are all fixedly connected to the top of the first stage evaporation separator 3, the three branch pipelines at the outlet of the third flushing water line 23 are all fixedly connected to the top of the second stage evaporation separator 5, and the second flushing water line 22 is connected to the first gas phase line 1 6, a fifth flushing water pipeline 45 is fixedly connected between the fifth flushing water pipeline 45 and the outlet of the second flushing water pipeline 22, and a sixth flushing water pipeline 46 is fixedly connected between the second flushing water pipeline 22 and the first gas phase pipeline 16, a seventh flushing water pipeline 47 is fixedly connected between the fourth flushing water pipeline 24 and the second gas phase pipeline 18, and an eighth flushing water pipeline 48 is fixedly connected between the seventh flushing water pipeline 47 and the outlet of the fourth flushing water pipeline 24, and between the fourth flushing water pipeline 24 and the second gas phase pipeline 18.

[0033] As needed, the gaseous mixture of urea and ammonia tends to form crystals at the top of the first-stage evaporation separator 3, the second-stage evaporation separator 5, and at the elbows of the first gas-phase pipeline 16 and the second gas-phase pipeline 18. Three branch pipelines are set at the outlets of the first flushing water pipeline 21 and the third flushing water pipeline 23 (with an angle of 60° between each two branch pipelines). This arrangement allows the top of the first-stage evaporation separator 3 and the top of the second-stage evaporation separator 5 to be flushed from different angles.

[0034] The second flushing water pipeline 22, the fifth flushing water pipeline 45, the sixth flushing water pipeline 46, the fourth flushing water pipeline 24, the seventh flushing water pipeline 47 and the eighth flushing water pipeline 48 can promptly flush out the crystals at the elbows of the first gas phase pipeline 16 and the second gas phase pipeline 18 to prevent the crystals from clogging the first gas phase pipeline 16 and the second gas phase pipeline 18, thereby ensuring the normal operation of the system.

[0035] Example 9: As an optimization of the above embodiment, as shown in the attached Figure 1As shown, the first flushing water line 21 between the flushing water pipe 20 and the drainage line 25 is respectively provided with a first automatic control valve 26 and a second automatic control valve 27 according to the flow direction of the medium, the drainage line 25 is fixedly provided with a third automatic control valve 28, the first flushing water line 21 between the second flushing water line 22 and the third flushing water line 23 is fixedly provided with a first stage flushing main valve 29, the third flushing water line 23 between the first flushing water line 21 and the fourth flushing water line 24 is fixedly provided with a second stage flushing main valve 30, the branch pipelines of the first flushing water line 21 are respectively fixedly provided with a first flushing automatic control valve 31, a second flushing automatic control valve 32, and a third flushing automatic control valve 33, and the sixth flushing water line 46 is fixedly provided with a There is a fourth flushing automatic control valve 34, a fifth flushing automatic control valve 35 is fixedly provided on the second flushing water pipeline 22 between the sixth flushing water pipeline 46 and the first gas phase pipeline 16, a sixth flushing automatic control valve 36 is fixedly provided on the fifth flushing water pipeline 45, a seventh flushing automatic control valve 37, an eighth flushing automatic control valve 38, and a ninth flushing automatic control valve 39 are fixedly provided on the branch pipelines of the third flushing water pipeline 23, a tenth flushing automatic control valve 40 is fixedly provided on the seventh flushing water pipeline 47, an eleventh flushing automatic control valve 41 is fixedly provided on the eighth flushing water pipeline 48, and a twelfth flushing automatic control valve 42 is fixedly provided on the pipeline of the fourth flushing water pipeline 24 between the eighth flushing water pipeline 48 and the first gas phase pipeline 16.

[0036] Example 10: As an optimization of the above embodiment, as shown in the attached Figure 1 As shown, it also includes a DCS controller, and the urine pump 9, the melting pump 10, the first automatic control valve 26, the second automatic control valve 27, the third automatic control valve 28, the first stage flushing main valve 29, the second stage flushing main valve 30, and the first flushing automatic control valve 31 to the twelfth flushing automatic control valve 42 are all electrically connected to the DCS controller.

[0037] In the present invention, unless otherwise specified, the equipment and devices used are all publicly known equipment and devices in the art.

[0038] As required, the pipelines and equipment of the urea system evaporation device may be equipped with conventional valves, thermometers, pressure gauges, etc. that are well known and used in the art according to production needs.

[0039] In summary, the urea system flushing evaporation device of the present invention adopts a simple and effective method with a reasonable and compact structure. By intermittently flushing the relevant parts of the evaporation system, it prevents the formation of excessive crystals to block the pipeline, ensuring that the urea evaporation system operates more stably. At the same time, the gas phase separated by evaporation is condensed and ammonia and other substances therein are recovered, thereby reducing the emission of pollutants.

[0040] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or removed according to actual needs to meet the requirements of different situations.

Claims

1. A urea system evaporation flushing method, characterized in that The implementation device of the flushing method includes a urea liquid tank, a first-stage evaporation heater, a first-stage evaporation separator, a second-stage evaporation heater, a second-stage evaporation separator, a first-stage evaporation surface condenser, a second-stage evaporation surface condenser, and an ammonia water tank. The top outlet of the first-stage evaporation separator and the upper inlet of the first-stage evaporation surface condenser are fixedly connected with a first gas phase pipeline, the top outlet of the second-stage evaporation separator and the upper inlet of the second-stage evaporation surface condenser are fixedly connected with a second gas phase pipeline, the top inlet of the first-stage evaporation separator is fixedly connected with a first flushing water pipeline, the water inlet of the first flushing water pipeline is fixedly connected with a flushing water pipe, the first flushing water pipeline and the first gas phase pipeline are fixedly connected with a second flushing water pipe, and the flushing water pipe and the second flushing water pipeline are fixedly connected with a first flushing water pipe. A third flushing water line is fixedly connected between the first flushing water line and the top inlet of the second-stage evaporation separator, a fourth flushing water line is fixedly connected between the third flushing water line and the second gas phase line, a shower guide line is fixedly connected to the first flushing water line between the third flushing water line and the flushing water mother pipe, three branch pipelines are provided at the outlets of the first flushing water line and the third flushing water line, a fifth flushing water line is fixedly connected between the second flushing water line and the first gas phase line, a sixth flushing water line is fixedly connected between the second flushing water line and the first gas phase line, a seventh flushing water line is fixedly connected between the fourth flushing water line and the second gas phase line, and an eighth flushing water line is fixedly connected between the fourth flushing water line and the second gas phase line; The first flushing water pipeline between the flushing water pipe and the drainage pipeline is respectively provided with the first automatic control valve and the second automatic control valve according to the flow direction of the medium. The drainage pipeline is fixedly provided with the third automatic control valve. The first flushing water pipeline between the second flushing water pipeline and the third flushing water pipeline is fixedly provided with a first-stage flushing main valve. The third flushing water pipeline between the first flushing water pipeline and the fourth flushing water pipeline is fixedly provided with a second-stage flushing main valve. The first flushing automatic control valve, the second flushing automatic control valve and the third flushing automatic control valve are respectively fixedly provided on the branch pipelines of the first flushing water pipeline. The sixth flushing water pipeline is fixedly provided with a Four flushing automatic control valves, a fifth flushing automatic control valve is fixedly provided on the second flushing water pipeline between the sixth flushing water pipeline and the first gas phase pipeline, a sixth flushing automatic control valve is fixedly provided on the fifth flushing water pipeline, a seventh flushing automatic control valve, an eighth flushing automatic control valve, and a ninth flushing automatic control valve are fixedly provided on the branch pipelines of the third flushing water pipeline, respectively, a tenth flushing automatic control valve is fixedly provided on the seventh flushing water pipeline, an eleventh flushing automatic control valve is fixedly provided on the eighth flushing water pipeline, and a twelfth flushing automatic control valve is fixedly provided on the fourth flushing water pipeline between the eighth flushing water pipeline and the first gas phase pipeline; The flushing method comprises the following steps: the first step is to adjust the temperature of the urea evaporation system; the second step is to open the first automatic control valve and the second automatic control valve in sequence, and lead the flushing water to the first flushing main valve and the second flushing main valve; the third step is to open the second flushing main valve, and open the seventh flushing automatic control valve, the eighth flushing automatic control valve, and the ninth flushing automatic control valve in sequence to flush the top of the second-stage evaporation separator; the fourth step is to check that the seventh flushing automatic control valve, the eighth flushing automatic control valve, and the ninth flushing automatic control valve are all closed, and open the tenth flushing automatic control valve, the eleventh flushing automatic control valve, and the twelfth flushing automatic control valve in sequence to flush the elbow of the second gas phase pipeline; the fifth step is to open the first flushing main valve, Open the first flushing automatic control valve, the second flushing automatic control valve, and the third flushing automatic control valve in sequence to flush the top of the first stage evaporator separator; Step 6, check that the first flushing automatic control valve, the second flushing automatic control valve, and the third flushing automatic control valve are all closed, and open the fourth flushing automatic control valve, the fifth flushing automatic control valve, and the sixth flushing automatic control valve in sequence to flush the first gas phase pipeline; Step 7, repeat the above steps 2 to 6 twice in sequence; Step 8, close the first automatic control valve, open the third automatic control valve, drain the remaining flushing water, and close the second automatic control valve and the third automatic control valve; Step 9, adjust the temperature of the first stage evaporator heater and the temperature of the second stage evaporator heater to the indicator control range.

2. The urea system evaporation flushing method according to claim 1, characterized in that: In the first step, the temperature of the first stage evaporation heater is increased from 125°C to 126.5°C to 130°C to 132.5°C, and the temperature of the second stage evaporation heater evaporation system is increased from 134.5°C to 135.5°C to 139.5°C to 141.5°C.

3. The urea system evaporation and flushing method according to claim 1 or 2, characterized in that: In the third step, the flushing time for each location is 10s to 15s; in the fourth step, the flushing time for each location is 15s to 30s; in the fifth step, the flushing time for each location is 3s to 5s; in the sixth step, the flushing time for each location is 15s to 30s.

4. The urea system evaporation flushing method according to claim 3, characterized in that: In the ninth step, the temperature index control range of the first stage evaporation heater is 125°C to 126.5°C, and the temperature index control range of the second stage evaporation heater is 134.5°C to 135.5°C.

5. The urea system evaporation and flushing method according to claim 1, 2 or 4, characterized in that: A first urea liquid pipeline is fixedly connected between the bottom outlet of the urea liquid tank and the inlet of the first-stage evaporation heater, a second urea liquid pipeline is fixedly connected between the top outlet of the first-stage evaporation heater and the upper inlet of the first-stage evaporation separator, a third urea liquid pipeline is fixedly connected between the bottom outlet of the first-stage evaporation separator and the upper inlet of the second-stage evaporation heater, a fourth urea liquid pipeline is fixedly connected between the top outlet of the second-stage evaporation heater and the upper inlet of the second-stage evaporation separator, a urea pipeline is fixedly connected to the bottom outlet of the second-stage evaporation separator, a first ammonia pipeline is fixedly connected between the bottom outlet of the first-stage evaporation surface condenser and the ammonia tank, and a second ammonia pipeline is fixedly connected between the bottom outlet of the second-stage evaporation surface condenser and the first ammonia pipeline.

6. The urea system evaporation and flushing method according to claim 5, characterized in that A urine pump is fixedly installed on the first urea liquid pipeline, a melting pump is fixedly installed on the urea pipeline, a first sight glass is fixedly installed on the third urea liquid pipeline, and a second sight glass is fixedly installed on the urea pipeline between the second-stage evaporation separator and the melting pump.

7. The urea system evaporation and flushing method according to claim 1, 2, 4 or 6, characterized in that: The three branch pipelines of the first flushing water pipeline outlet are all fixedly connected to the top of the first stage evaporation separator, and the three branch pipelines of the third flushing water pipeline outlet are all fixedly connected to the top of the second stage evaporation separator.

8. The urea system evaporation and flushing method according to claim 4, characterized in that: It also includes a DCS controller, and the urine pump, melting pump, first automatic control valve, second automatic control valve, third automatic control valve, first stage flushing main valve, second stage flushing main valve and first flushing automatic control valve to twelfth automatic control valve are all electrically connected to the DCS controller.

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