Energy-saving and efficient adjustable ammonia production process from alcohol precursor gas

Abstract

The application discloses an energy-saving, efficient and adjustable alcohol pre-gas ammonia production process method, and particularly comprises the following steps: S1, a raw material gas is separated from a pressurized coal gasification methanol device as alcohol pre-gas and is sent to a shift device of synthetic ammonia through a sealed pipeline; S2, when entering the shift device, the alcohol pre-gas is mixed with a crude synthetic gas to form a mixed gas, then high-pressure steam is introduced to adjust the water-gas and increase the mixed temperature, carbon monoxide is reacted with water vapor in the shift device, and hydrogen gas is prepared as a shift gas; S3, the shift gas is subjected to low-temperature methanol washing and liquid nitrogen washing, then nitrogen gas produced by air separation is added, a synthetic gas is prepared, and the synthetic gas is sent to an ammonia synthesis device. The energy-saving, efficient and adjustable alcohol pre-gas ammonia production process method is adopted, raw material gas is comprehensively utilized in an energy-saving mode, the methanol and synthetic ammonia production yield is flexibly adjusted, and enterprise benefits are improved.

Description

Technical Field

[0001] This invention relates to the technical field of ammonia synthesis processes, and more particularly to an energy-efficient, highly effective, and adjustable process for producing ammonia from alcohol pre-gas. Background Technology

[0002] Currently, pressurized coal gasification technology is widely used in ammonia and methanol production plants. However, different production processes result in varying contents of carbon monoxide, carbon dioxide, hydrogen, and nitrogen in the syngas. Therefore, it's impossible to directly adjust ammonia and methanol production output, meaning that product structure adjustments cannot be made to achieve better economic benefits when ammonia and methanol market prices fluctuate. To achieve product structure adjustments and greater economic benefits for production units, the following innovative transformation and invention patent projects are proposed:

[0003] Based on market conditions, and without changing the existing total production capacity of methanol and synthetic ammonia, without increasing coal and energy consumption, and while minimizing energy consumption as much as possible, we should innovate the design and flexibly adjust the ammonia-methanol product structure to improve corporate efficiency. Summary of the Invention

[0004] The purpose of this invention is to provide an energy-efficient and adjustable process for producing ammonia from methanol pre-gas, achieving comprehensive energy-saving utilization of raw material gas, flexibly adjusting methanol and synthetic ammonia production, and intelligently regulating ammonia-methanol co-production and energy saving and efficiency improvement.

[0005] To achieve the above objectives, the present invention provides an energy-efficient and adjustable process for producing ammonia from methanol pre-gas, specifically comprising the following steps:

[0006] S1. A stream of raw gas is separated from the pressurized coal gasification methanol production unit as methanol precursor gas and sent to the ammonia synthesis conversion unit through a sealed pipeline.

[0007] S2. When entering the conversion unit, the alcohol precursor gas and crude synthesis gas are mixed to form a mixed gas. Then, high-pressure steam is introduced to regulate the water vapor and increase the mixing temperature. In the conversion unit, carbon monoxide reacts with water vapor to produce hydrogen as the conversion gas.

[0008] S3. The shift gas is washed with low-temperature methanol and liquid nitrogen, and then nitrogen produced by air separation is added to form syngas, which is then sent to the ammonia synthesis unit.

[0009] Preferably, the conversion device in step S1 is a pressurized coal-water slurry conversion device for ammonia production, which includes a heater, a desulfurization tank and a conversion furnace.

[0010] Preferably, the feed gas in step S1 is methanol synthesis gas.

[0011] Preferably, in step S2, the alcohol precursor gas and crude syngas form a mixed gas after the heater, and high-pressure steam is introduced before the mixed gas enters the desulfurization tank, and carbon monoxide and water vapor react in the converter.

[0012] Preferably, in step S2, the crude syngas undergoes conversion, gas purification, and nitrogen addition to adjust its composition.

[0013] Preferably, in step S3, the ratio of hydrogen to nitrogen in the synthesis gas is 3:1.

[0014] This invention employs the above-mentioned energy-saving, efficient, and adjustable process for producing ammonia from alcohol pre-gas, which has the following beneficial effects:

[0015] (1) No additional reactor is required, and the investment is small. The appropriate reaction rate is controlled by adjusting the metering and amount of gas ①②③. The water vapor in the crude wet raw material gas of the ammonia synthesis system is fully utilized. The conversion device for ammonia production is used to save energy and reduce consumption, so as to achieve adjustable ammonia-methanol production.

[0016] (2) By installing a flow regulation DCS and a safety shut-off device SIS on the gas pipeline before alcohol, the gas can be safely discharged to the flare in an emergency, so that the two devices can be connected and disconnected, and safe operation can be achieved.

[0017] (3) The operation is simple and does not have a significant impact on the original system. Through intelligent adjustment of the interlocking design, only the high-pressure steam is appropriately increased and the steam-gas ratio is adjusted to maintain at around 1.2, thereby improving the conversion rate of carbon monoxide in the pre-methanol gas, meeting the production adjustment requirements, realizing flexible market adjustment, and increasing benefits.

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process in an embodiment of the present invention. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0022] Example 1

[0023] like Figure 1 As shown, an energy-efficient and adjustable process for producing ammonia from methanol pre-gas specifically includes the following steps:

[0024] S1. The methanol precursor gas ① is cooled by a raw material gas cooler under a pressure of 6.0 MPa and a temperature of 65℃, then buffered and separated by a gas-liquid separator, and finally metered by a flow meter before entering the ammonia conversion unit.

[0025] S2, the alcohol precursor gas ① enters the pipeline after the heater in the ammonia conversion unit, where it mixes with the crude synthesis gas to form a mixed gas, and both enter the conversion unit. The composition of the two gases is shown in Table 1 below:

[0026] Table 1 Gas Composition Table

[0027]

[0028] Because the two gases have different compositions and temperatures, the water-gas ratio and temperature of the crude synthesis gas decrease after mixing. High-pressure steam (9.8 MPa, 540℃) needs to be added through the steam flow FV regulating valve to adjust the water-gas ratio and temperature, and raise the temperature of the mixed gas to 265℃ before it enters the shift converter through the desulfurization tank. In the shift converter, carbon monoxide reacts with water vapor to produce a suitable proportion of hydrogen as the shift gas for ammonia synthesis.

[0029] S3. The shift gas is then purified by low-temperature methanol washing and liquid nitrogen washing, and then nitrogen produced by air separation is added to form a synthesis gas with a hydrogen to nitrogen ratio of 3:1, which is then sent to the ammonia synthesis unit.

[0030] Assuming the crude syngas flow rate at the ammonia conversion inlet (dry basis) is Q1, calculations show that at 6 MPa, the water-to-gas ratio is 1.33 and the temperature is 280℃. However, to meet the conversion technology requirements, the water-to-gas ratio at the conversion inlet must not be lower than 1.05 and the temperature must not be lower than 265℃ to meet the conversion rate requirements of the conversion furnace.

[0031] Based on the above converter production requirements, the volume of alcohol pre-gas ① can be calculated as follows: Q2 can be calculated in the following two cases:

[0032] (1) The volume of the pre-methanol gas ① is relatively small, so there is no need to add high-pressure steam. Based on the calculation that the water-to-steam ratio should not be lower than 1.05, the volume of the pre-methanol gas Q2 < 0.26Q1; and based on the calculation that the temperature of the mixed gas should be greater than 265℃, the volume of the pre-methanol gas transported Q2 < (15c1 / c2(265-t2))Q1. Both of the above conditions must be met.

[0033] The calculation is as follows:

[0034] Depend on Therefore, Q2 < 0.26Q1;

[0035] From c1Q1(280-265)>c2Q2(265-t2), we get: Q2<(15c1 / c2(265-t2))Q1

[0036] (2) When the amount of gas Q2 before alcohol production is large, the mixing temperature t3 = (c1Q1t1 + c2Q2t2) / (c1Q1 + c2Q2)

[0037] The calculation is as follows:

[0038] From c1Q1(t1-t3) = c2Q2(t3-t2), we get: t3 = (c1Q1t1 + c2Q2t2) / (c1Q1 + c2Q2); the water-to-gas ratio after mixing is W = 1.33Q1 / (Q1 + Q2). The required amount of high-pressure steam is calculated based on the water-to-gas ratio and the temperature after mixing.

[0039] Q3= ;

[0040] And it must satisfy Q3>0.844Q2-0.225Q1.

[0041] The calculation is as follows:

[0042] Depend on have to:

[0043] Q3= ;

[0044] Depend on:

[0045] ,

[0046] Therefore, Q3 > 0.844Q2 - 0.225Q1.

[0047] Note: C1 is the specific heat of crude syngas; C2 is the specific heat of alcohol precursor gas; C 混 The specific heat of mixing crude synthesis gas and alcohol precursor gas is given.

[0048] The above-mentioned correlation invention relates to a linked gas volume regulation process and equipment, which satisfies the purpose of intelligent regulation of ammonia-methanol co-production and energy saving and efficiency improvement.

[0049] Example 2

[0050] When adjusting the ammonia-methanol production under operating conditions 1 and 2:

[0051] Operating Condition 1: When a small amount of alcohol precursor gas needs to undergo a shift reaction to produce synthetic ammonia (alcohol precursor gas: synthetic ammonia gas ≤ 1:10):

[0052] like Figure 1 By opening the FV flow regulating valve and XZV emergency shut-off valve of the alcohol pre-gas, the pressure is controlled to 6.0MPa and sent to the ammonia synthesis conversion unit. The outlet gas temperature of the heater is adjusted to 270℃ before entering the desulfurization tank. The conversion rate in the conversion furnace is adjusted so that the CO content exiting the conversion furnace is ≤0.9%.

[0053] Operating Condition 2: When a relatively large amount of alcohol precursor gas needs to be converted to produce synthetic ammonia (ethanol precursor gas: synthetic ammonia gas ≤ 1:2-1:10):

[0054] like Figure 1By opening the FV flow regulating valve and XZV emergency shut-off valve of the alcohol pre-gas, the pressure is controlled to 6.0MPa and sent to the ammonia synthesis conversion unit. The outlet gas temperature of the heater is adjusted to 270℃. At the same time, the high-pressure steam ③ is opened to make the crude synthesis gas steam-gas ratio of 6.5MPa 1.19 and send it to the inlet gas pipe of the desulfurization tank. The conversion rate in the conversion furnace is controlled so that the CO content leaving the conversion furnace is ≤0.9%.

[0055] Operating Condition 3: When producing methanol and synthesizing ammonia separately:

[0056] like Figure 1 After shutting off gas ① and ② in a safe sequential control interlocking sequence, the FV flow regulating valve and XZV emergency shut-off valve on the methanol pre-gas pipeline are then closed. The PV vent valve is opened to the flare, and the vent is closed after safe release, thus achieving independent production of the methanol and synthetic ammonia systems.

[0057] Therefore, this invention adopts the above-mentioned energy-saving, efficient, and adjustable process for producing ammonia from methanol pre-gas. A portion of the methanol pre-gas is extracted from the centrifugal compressor of the methanol synthesis unit as feed gas. The extraction pressure is high, matching the inlet pressure of the crude synthesis gas from the conversion inlet, and has minimal impact on the methanol synthesis gas compressor, requiring no compressor modification. The reduced synthesis gas intake of the methanol unit can be addressed by adjusting operating parameters to decrease methanol production capacity. After adjusting methanol production capacity, the pressure rating of the original methanol unit equipment can meet the requirements of the modified operating conditions. Considering market conditions, and without changing the total existing methanol and ammonia production capacity, the methanol pre-gas extracted from the pressurized coal gasification methanol unit is converted by a coal-water slurry pressurized conversion unit to produce suitable hydrogen, which is then added to nitrogen produced by air separation to form synthesis gas (hydrogen:nitrogen = 3:1). This synthesis gas is then sent to the ammonia synthesis unit to produce synthetic ammonia, allowing for flexible adjustment of methanol and synthetic ammonia production.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A process for producing ammonia from alcohol precursor gas, characterized in that, Specifically, the following steps are included: S1. A stream of feed gas is separated from the pressurized coal gasification methanol production unit as methanol precursor gas and sent to the ammonia synthesis conversion unit through a sealed pipeline; the conversion unit is a pressurized coal-water slurry conversion unit for ammonia production, which includes a heater, a desulfurization tank and a conversion furnace; the feed gas is methanol synthesis gas; S2. Upon entering the shift converter, the alcohol precursor gas mixes with the crude syngas to form a mixed gas. High-pressure steam is then introduced to adjust the water-to-gas ratio and increase the mixing temperature. In the shift converter, carbon monoxide reacts with water vapor to produce hydrogen, which is then used as the shift gas. The molar percentages of carbon monoxide and hydrogen in the alcohol precursor gas are 13.59% and 79.39%, respectively. S3. The shift gas is washed with low-temperature methanol and liquid nitrogen, and then nitrogen produced by air separation is added to form syngas, which is then sent to the ammonia synthesis unit.

2. The energy-saving, efficient, and adjustable process for producing ammonia from methanol pre-gas according to claim 1, characterized in that: In step S2, the alcohol precursor gas and crude syngas form a mixed gas after the heater. High-pressure steam is introduced before the mixed gas enters the desulfurization tank, and carbon monoxide and steam react in the converter.

3. The energy-saving, efficient, and adjustable process for producing ammonia from methanol pre-gas according to claim 1, characterized in that: In step S2, the crude syngas undergoes conversion, gas purification, and nitrogen addition to adjust its composition.

4. The energy-saving, efficient, and adjustable process for producing ammonia from methanol pre-gas according to claim 1, characterized in that: In step S3, the ratio of hydrogen to nitrogen in the synthesis gas is 3:1.

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