CN107253895A - A kind of system and method by low-carbon alkanes co-producing light olefins and ammonia - Google Patents

Abstract

The present invention relates to a system and method for co-producing low-carbon olefins and ammonia from low-carbon alkanes, comprising an alkane dehydrogenation unit (100), an air separation unit (200) and an ammonia synthesis unit (300), the alkane dehydrogenation unit (100) is connected to the ammonia synthesis unit (300) through a hydrogen delivery pipeline (12), and the air separation unit (200) is connected to the ammonia synthesis unit (300) through a nitrogen delivery pipeline (22). The low-carbon alkanes are reacted in the alkane dehydrogenation unit to obtain the corresponding low-carbon olefins and hydrogen, and after separation, high-purity low-carbon olefin products and hydrogen are obtained, and the latter enters the ammonia synthesis unit to react with the high-purity nitrogen obtained from the air separation unit , generating ammonia. Compared with the existing alkane dehydrogenation process or coal-based ammonia synthesis process that produces single olefins, the present invention makes full use of the hydrogen produced by the alkane dehydrogenation process to produce ammonia, and has the advantages of short process flow, less waste discharge, and high economic and social benefits.

Description

A system and method for coproducing light olefins and ammonia from light alkanes

technical field

The invention belongs to the field of chemical industry, and in particular relates to a system and method for co-producing low-carbon olefins and ammonia from low-carbon alkanes.

Background technique

Olefins, especially low-carbon olefins, ethylene, propylene and butene (including n-butene, 2-butene and isobutene) are the basis of the entire petrochemical industry, and their output and technical level represent the country's economic and technological development level. At present, low-carbon olefins mainly come from petroleum cracking (including steam cracking and catalytic cracking). The emerging coal chemical route, that is, methanol to olefins (MTO, MTP) is mainly suitable for countries and regions rich in coal resources, because methanol can be produced with cheap coal, and it is currently developing rapidly in my country. In addition, with the exploitation of natural gas in the United States and the Middle East, especially shale gas, a large amount of ethane and propane are by-produced, and their direct dehydrogenation can also produce low-carbon olefins.

In recent years, domestic and low-carbon hydrocarbon-rich places have accelerated the pace of dehydrogenation of low-carbon alkanes to olefins, which has obvious cost advantages. However, since the light olefin dehydrogenation unit produces a large amount of hydrogen, the utilization of hydrogen has become a new issue. At present, most hydrogen is used as fuel with low added value. On the other hand, my country is a country with a large population, food and chemical fertilizers. The demand for synthetic ammonia is very large, and its production requires a large amount of hydrogen. At present, my country's ammonia synthesis route mainly adopts the coal gasification route with coal as raw material, which requires large investment, high energy consumption, and pollution of waste gas, waste residue and waste water. Therefore, the development and full use of the hydrogen produced by the dehydrogenation of low-carbon alkanes to produce synthetic ammonia has good economic, environmental and social benefits.

Contents of the invention

The object of the present invention is to provide a system and method for co-producing light olefins and ammonia from light alkanes to realize the comprehensive utilization of by-product hydrogen in the dehydrogenation process of light alkanes in order to overcome the defects of the above-mentioned prior art.

The object of the present invention can be achieved through the following technical solutions: a system for co-producing low-carbon olefins and ammonia from low-carbon alkanes, characterized in that it includes an alkane dehydrogenation unit, an air separation unit and an ammonia synthesis unit, and the alkane dehydrogenation unit The hydrogen unit is connected to the ammonia synthesis unit through a hydrogen delivery pipeline, and the air separation unit is connected to the ammonia synthesis unit through a nitrogen delivery pipeline.

The alkane dehydrogenation unit comprises alkane dehydrogenation reaction equipment, hydrogen hydrocarbon separation equipment and olefin separation equipment, the alkane dehydrogenation reaction equipment is connected with the hydrogen hydrocarbon separation equipment, and the alkane separation equipment is connected to The alkane dehydrogenation reaction equipment is connected, the hydrogen delivery pipeline is connected with the hydrogen separation equipment, and the olefins discharged from the alkane separation equipment are output through the olefin pipeline.

The ammonia synthesis unit includes a hydrogen compressor, a nitrogen compressor, an ammonia synthesis reactor and an ammonia separation device, the hydrogen compressor and the nitrogen compressor are connected to the ammonia synthesis reactor, and the ammonia synthesis reactor and the ammonia separation The equipment is connected with a circulation pipeline through a pipeline, and the circulation pipeline is a hydrogen-nitrogen synthesis gas circulation pipeline, and the ammonia separated by the ammonia separation equipment is output through an ammonia delivery pipeline.

The hydrogen compressor and the nitrogen compressor can be combined into a hydrogen-nitrogen mixed gas compressor.

The air separation device includes pressure swing adsorption separation equipment or cryogenic rectification equipment.

The method for co-producing low-carbon alkanes and ammonia by using the above-mentioned system is characterized in that it comprises the following steps:

(1) Dehydrogenation of low-carbon alkanes to produce hydrogen: After mixing low-carbon alkanes with water vapor or hydrogen, the temperature is raised at 500-650°C after heating, and enters the dehydrogenation reaction equipment to obtain the corresponding low-carbon alkanes, alkanes and The mixture of hydrogen enters the hydrogen hydrocarbon separation equipment to obtain a mixture containing olefins and alkanes and high-purity hydrogen, and the high-purity hydrogen is sent out through the hydrogen delivery pipeline;

(2) Preparation of low-carbon olefins: the mixture of olefins and alkanes obtained from step (1) enters the olefin separation equipment to obtain high-purity low-carbon olefins, which are sent out through the olefin pipeline;

(3) air separation to prepare nitrogen: air enters the air separation unit to obtain high-purity nitrogen, which is sent out through the nitrogen delivery pipeline;

(4) Ammonia synthesis: the high-purity hydrogen obtained in step (1) enters the hydrogen compressor, the high-purity nitrogen obtained in the step enters the nitrogen compressor, and the high-purity hydrogen and high-purity nitrogen enter the ammonia synthesis reactor after compression, or after mixing After boosting to the reaction pressure of ammonia synthesis, it enters the ammonia synthesis reaction equipment to generate ammonia, which is then condensed and separated by the ammonia separation equipment to obtain synthetic ammonia, and the ammonia delivery pipeline outputs high-purity ammonia.

The lower alkanes include, but are not limited to, ethane, propane, butane and pentane.

The purity of the hydrogen obtained in the step (1) is greater than 99.0%, and the purity of the nitrogen obtained in the step (3) is greater than 99.0%.

The purity of the light olefins is greater than 95.0%, and the purity of the ammonia is greater than 99.5%.

The purity of the light olefins is greater than 99.5%.

Compared with the prior art, the beneficial effect of the present invention is that the hydrogen produced in the dehydrogenation process of low-carbon alkane can be fully utilized and applied to the ammonia synthesis process. The process flow of ammonia synthesis process is shortened. Compared with the prior art, the invention has high process integration degree, less waste discharge and obvious advantages in economic and social benefits.

Description of drawings

Fig. 1 is a schematic diagram of the process flow of the present invention;

Fig. 2 is another kind of process flow diagram of the present invention.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1

A factory uses propane as raw material, and applies the system shown in Figure 1 to co-produce propylene and ammonia. The system includes an alkane dehydrogenation unit 100, an air separation unit 200 and an ammonia synthesis unit 300, wherein the alkane dehydrogenation unit 100 passes through a hydrogen delivery pipeline 12 is connected to the ammonia synthesis unit 300, and the air separation unit 200 is connected to the ammonia synthesis unit 300 through the nitrogen delivery pipeline 22.

Specifically:

The alkane dehydrogenation unit 100 comprises an alkane dehydrogenation reaction device 110, a hydrogen hydrocarbon separation device 120 and an alkane separation device 130, and the alkane dehydrogenation reaction device 110 is connected with the hydrogen hydrocarbon separation device 120, and the alkane separation device 130 is connected with the alkane circulation pipeline 13 The alkane dehydrogenation reaction equipment 110 is connected, the hydrogen delivery pipeline 12 is connected with the hydrogen hydrocarbon separation equipment 120 , and the propylene product obtained from the olefin separation equipment 130 is output through the olefin pipeline 14 .

Ammonia synthesis plant 300 includes hydrogen compressor 310 and nitrogen compressor 320, ammonia synthesis reactor 330 and ammonia separation equipment 340, ammonia synthesis reactor 330 and ammonia separation equipment are connected by pipeline 32 and circulation pipeline 33, circulation pipeline 33 It is a hydrogen-nitrogen synthesis gas circulation pipeline, and the ammonia product separated by the ammonia separation device 340 is output through the ammonia delivery pipeline 34 .

Air separation plant 200 includes cryogenic rectification equipment.

Applying the above-mentioned system to co-produce propylene and ammonia comprises the following steps:

(1) Propane dehydrogenation to produce hydrogen: after propane is mixed with water vapor, the temperature is raised to 600°C after heating, and then enters the dehydrogenation reaction equipment 110 through the pipeline 11 to obtain a mixture containing propylene, propane and hydrogen, and then enters the hydrogen hydrocarbon The separation device 120 obtains hydrogen and a mixture containing propylene and propane, and the hydrogen is sent out through the hydrogen delivery pipeline 12 to obtain hydrogen with a purity greater than 99.9%;

(2) Preparation of propylene: the mixture of propylene and propane obtained from step (1) enters the alkane separation device 130, the obtained propylene is sent out by the olefin delivery pipeline 14, and the remaining gas returns to the dehydrogenation reaction device 110 through the alkane circulation pipeline 13;

(3) Air separation to prepare nitrogen: air enters the air separation unit 200 to obtain nitrogen with a purity greater than 99.0%, and sends it out through the nitrogen delivery pipeline 22;

(4) Ammonia is synthesized: the high-purity hydrogen that step (1) obtains is input hydrogen compressor 310 boost by hydrogen delivery pipeline 12, and the high-purity nitrogen that step (3) obtains is input nitrogen compressor 320 liters by nitrogen delivery pipeline 22 pressure, and then enter the ammonia synthesis reaction equipment 330 together to generate ammonia, which is then condensed and separated by the ammonia separation equipment 340 to obtain synthetic ammonia, which is output by the ammonia delivery pipeline 34.

In this embodiment, the system and method of the present invention are applied, the hydrogen generated by the propane dehydrogenation unit can be used in the ammonia synthesis unit, the conversion rate of propane per pass is 40%, the selectivity of propylene is 84%, and the purity of the obtained propylene product is The purity of the obtained ammonia was 99.5%.

Example 2

A factory uses isobutane as raw material, and applies the system shown in Figure 1 to co-produce isobutene and ammonia. The system includes an alkane dehydrogenation unit 100, an air separation unit 200 and an ammonia synthesis unit 300, wherein the alkane dehydrogenation unit 100 is transported by hydrogen The pipeline 12 is connected to the ammonia synthesis unit 300 , and the air separation unit 200 is connected to the ammonia synthesis unit 300 through the nitrogen delivery pipeline 22 .

Wherein, the alkane dehydrogenation unit 100 includes alkane dehydrogenation reaction equipment 110, hydrogen hydrocarbon separation equipment 120 and alkane separation equipment 130, alkane dehydrogenation reaction equipment 110 is connected with hydrogen hydrocarbon separation equipment 120, and alkane separation equipment 130 passes through the alkane circulation pipeline 13 is connected to the alkane dehydrogenation reaction equipment 110, the hydrogen delivery pipeline 12 is connected to the hydrogen hydrocarbon separation equipment 120, and the obtained propylene product is output through the olefin pipeline 14.

Ammonia synthesis unit 300 comprises hydrogen compressor 310 and nitrogen compressor 320, ammonia synthesis reactor 330 and ammonia separation equipment 340, ammonia synthesis reactor 330 and ammonia separation equipment are connected by pipeline 32 and 33, and circulation pipeline 33 is hydrogen nitrogen Synthesis gas circulation pipeline, the obtained ammonia product is exported through the ammonia delivery pipeline 34 .

Air separation plant 200 includes pressure swing adsorption separation equipment.

Applying the above-mentioned system to co-produce isobutylene and ammonia comprises the following steps:

(1) Dehydrogenation of isobutane to produce hydrogen: After isobutane is mixed with hydrogen, the temperature is raised to 580°C after heating, and then enters the dehydrogenation reaction device 110 to obtain a mixture containing isobutene, isobutane and hydrogen, and then enters hydrogen The hydrocarbon separation equipment 120 obtains hydrogen and a mixture containing isobutene and isobutane, and the hydrogen is sent out through the hydrogen delivery pipeline 12 to obtain hydrogen with a purity greater than 99.9%;

(2) Preparation of isobutene: the mixture of isobutene and isobutane obtained from step (1) enters the olefin separation device 130, and the obtained isobutene is sent out by the olefin delivery pipeline 14;

(3) Air separation to prepare nitrogen: air enters the air separation unit 200 to obtain nitrogen with a purity greater than 99.0%, and sends it out through the nitrogen delivery pipeline 22;

(4) Ammonia synthesis: the high-purity hydrogen obtained by step (1) and the high-purity nitrogen obtained by step (3) enter the ammonia synthesis unit 300 through the hydrogen delivery pipeline 12 and the nitrogen delivery pipeline 22 respectively, and the ammonia synthesis unit The hydrogen and nitrogen in 300 are boosted by their respective compressors: hydrogen compressor 310 and nitrogen compressor 320, and then enter the ammonia synthesis reaction equipment 330 to generate ammonia, which is then condensed and separated by the ammonia separation equipment 340 to obtain synthetic ammonia, which is transported by the ammonia pipeline 34 outputs.

In this embodiment, the system and method of the present invention are applied, the hydrogen generated by the isobutane dehydrogenation unit can be used in the ammonia synthesis unit, the single-pass conversion rate of isobutane is 35%, and the selectivity of isobutene is 91%. The isobutene product has a purity of 99.6%, and the ammonia obtained has a purity of 99.5%.

Example 3

A factory uses propane as raw material and applies the system shown in Figure 2 to co-produce propylene and ammonia. The difference from Example 1 is that in this example, in order to reduce equipment investment, a hydrogen-nitrogen mixed gas compressor 310' is used to replace the hydrogen compressor 310 and nitrogen compressor 320 in Example 1. The alkane dehydrogenation device 100 The high-purity hydrogen and high-purity nitrogen from the air separation unit 200 are boosted by the hydrogen-nitrogen mixture compressor 310 ′, and then enter the ammonia synthesis reaction device 330 to generate ammonia.

The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and changes according to the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art shall be within the scope of protection defined by the claims.

Claims (10)

1. A system for the coproduction of low-carbon olefins and ammonia by low-carbon alkanes, characterized in that it comprises an alkane dehydrogenation unit (100), an air separation unit (200) and an ammonia synthesis unit (300), and the alkane dehydrogenation unit The device (100) is connected to the ammonia synthesis unit (300) through a hydrogen delivery pipeline (12), and the air separation unit (200) is connected to the ammonia synthesis unit (300) through a nitrogen delivery pipeline (22). 2. A system for co-producing low-carbon olefins and ammonia from low-carbon alkanes according to claim 1, characterized in that, the alkane dehydrogenation device (100) includes alkane dehydrogenation reaction equipment (110), hydrogen Separation equipment (120) and alkane separation equipment (130), described alkane dehydrogenation reaction equipment (110) links to each other with described hydrogen hydrocarbon separation equipment (120), and described alkane separation equipment (130) passes alkane circulation line ( 13) It is connected to the alkane dehydrogenation reaction equipment (110), the hydrogen delivery pipeline (12) is connected to the hydrogen separation equipment (120), and the olefins discharged from the alkane separation equipment (130) pass through the olefin pipeline (14) OUTPUT. 3. a kind of system by low-carbon alkanes coproduction low-carbon olefins and ammonia according to claim 1, is characterized in that, described ammonia synthesis unit (300) comprises hydrogen compressor (310), nitrogen compressor (320 ), ammonia synthesis reactor (330) and ammonia separation equipment (340), described hydrogen compressor (310) and nitrogen compressor (320) are all connected to ammonia synthesis reactor (330), and described ammonia synthesis reactor (330) is connected with the ammonia separation equipment through the pipeline (32) and the circulation pipeline (33), and the circulation pipeline (33) is a hydrogen-nitrogen synthesis gas circulation pipeline, and the ammonia separated by the ammonia separation equipment (340) Output through the ammonia delivery pipeline (34). 4. A system for co-producing low-carbon olefins and ammonia from low-carbon alkanes according to claim 3, characterized in that, the hydrogen compressor (310) and the nitrogen compressor (320) can be combined into hydrogen nitrogen Mixture compressor. 5. a kind of system by low-carbon alkanes co-production low-carbon olefins and ammonia according to claim 1, is characterized in that, described air separation unit (200) comprises pressure swing adsorption separation equipment or cryogenic rectification equipment . 6. A method that adopts the arbitrary described system of claim 1-5 to carry out the method for low-carbon alkane coproduction low-carbon olefin and ammonia, it is characterized in that, comprises the following steps: (1) Dehydrogenation of low-carbon alkanes to produce hydrogen: After mixing low-carbon alkanes with water vapor or hydrogen, the temperature is raised to 500-650°C after heating, and then enters the dehydrogenation reaction equipment (110) to obtain the corresponding low-carbon olefins , a mixture of alkanes and hydrogen, and then enter the hydrogen hydrocarbon separation equipment (120) to obtain a mixture containing alkenes and alkanes and high-purity hydrogen, and the high-purity hydrogen is sent out through the hydrogen delivery pipeline (12); (2) Preparation of low-carbon olefins: the mixture of olefins and alkanes obtained from step (1) enters the olefin separation device (130) to obtain high-purity low-carbon olefins, which are sent out through the olefin pipeline (14); (3) Air separation to prepare nitrogen: air enters the air separation unit (200) to obtain high-purity nitrogen, which is sent out through the nitrogen delivery pipeline (22); (4) Ammonia synthesis: the high-purity hydrogen obtained in step (1) enters the hydrogen compressor (310), the high-purity nitrogen obtained in step (3) enters the nitrogen compressor (320), and the high-purity hydrogen and high-purity nitrogen are compressed Enter the ammonia synthesis reactor (330), or after mixing, pressurize to the reaction pressure of ammonia synthesis and then enter the ammonia synthesis reaction equipment (330) to generate ammonia, and then condense and separate the ammonia synthesis equipment (340) to obtain synthetic ammonia. High-purity ammonia is output from the ammonia delivery pipeline (34). 7. The method for coproducing low-carbon alkanes and ammonia according to claim 6, characterized in that, the low-carbon alkanes include but not limited to ethane, propane, butane and pentane. 8. the method for low-carbon alkane coproduction low-carbon olefins and ammonia according to claim 6, is characterized in that, the purity of the hydrogen that step (1) obtains is greater than 99.0%, and the nitrogen purity that step (3) obtains is greater than 99.0% . 9. The method for coproducing low-carbon alkanes and ammonia from low-carbon alkanes according to claim 6, characterized in that the purity of the low-carbon olefins is greater than 95.0%, and the purity of the ammonia is greater than 99.5%. 10. The method for coproducing light olefins and ammonia from light alkanes according to claim 9, characterized in that the purity of the light olefins is greater than 99.5%.