阅读说明：本技术 利用低温等离子体反应系统制备尿素和液态氮肥的方法 (Method for preparing urea and liquid nitrogen fertilizer by using low-temperature plasma reaction system ) 是由 黄涛 宋东平 苏怡宇 金俊勋 杜晶 刘龙飞 周璐璐 于 2020-08-06 设计创作，主要内容包括：本发明公开了一种低温等离子体反应系统,低温等离子体反应系统包括气体混合室1、反应区、过滤池、接料槽、气体混合室2；反应区包括高压端1、反应槽、高压端2和接地端,反应槽内两端分别平行相向设置气管套1和气管套2,气管套1内设置针状电极1,气管套2内设置针状电极2。本发明还公开了利用该低温等离子体反应系统制备尿素和液态氮肥的方法。本发明制备工艺简单,可直接利用氢气、二氧化碳和氮气合成尿素和生产液态氮肥,合成过程无需高温环境。本发明最高可获得89%氮转化率和43%尿素生成率。本发明获得的液态氮肥可实现本发明制备的肥料可有效提高水稻的物种干重。本发明为固氮环保技术研发提供了一种可借鉴思路。(The invention discloses a low-temperature plasma reaction system, which comprises a gas mixing chamber 1, a reaction area, a filter tank, a material receiving groove and a gas mixing chamber 2, wherein the reaction area is arranged in the gas mixing chamber; the reaction zone comprises a high-voltage end 1, a reaction tank, a high-voltage end 2 and a grounding end, wherein the gas pipe sleeve 1 and the gas pipe sleeve 2 are respectively arranged at two ends in the reaction tank in parallel and oppositely, the needle electrode 1 is arranged in the gas pipe sleeve 1, and the needle electrode 2 is arranged in the gas pipe sleeve 2. The invention also discloses a method for preparing urea and liquid nitrogen fertilizer by using the low-temperature plasma reaction system. The invention has simple preparation process, can directly utilize hydrogen, carbon dioxide and nitrogen to synthesize urea and produce liquid nitrogen fertilizer, and does not need high-temperature environment in the synthesis process. The invention can obtain 89% nitrogen conversion rate and 43% urea generation rate at the highest. The liquid nitrogen fertilizer obtained by the invention can realize that the fertilizer prepared by the invention can effectively improve the species dry weight of rice. The invention provides a reference idea for the research and development of nitrogen fixation environment-friendly technology.)

1. A low-temperature plasma reaction system is characterized by comprising a gas mixing chamber 1, a reaction area, a filter tank, a material receiving groove and a gas mixing chamber 2 in sequence; the reaction zone comprises a high-voltage end 1, a reaction tank, a high-voltage end 2 and a grounding end, wherein the two ends in the reaction tank are respectively provided with a gas pipe sleeve 1 and a gas pipe sleeve 2 in parallel and in opposite directions, the end parts of the gas pipe sleeve 1 and the gas pipe sleeve 2 are open or distributed with air holes, a needle electrode 1 is arranged in the gas pipe sleeve 1, a needle electrode 2 is arranged in the gas pipe sleeve 2, the needle electrode 1 and the needle electrode 2 are parallel, collinear and arranged in opposite directions, the tips of the needle electrode 1 and the needle electrode 2 are opposite, the root of the needle electrode 1 is connected with the high-voltage end 1, the root of the needle electrode 2 is connected with the high-voltage end 2, a gas mixing chamber 1 leads gas into the gas pipe sleeve 1 through a gas pump and a gas mass flowmeter, the gas mixing chamber 2 leads the gas into the gas pipe sleeve 2 through the gas pump and the gas mass flowmeter, and gas, and liquid and solid products generated in the reaction area are transferred into a receiving hopper through a receiving funnel.

2. The low-temperature plasma reaction system according to claim 1, wherein the high-voltage terminal 1 and the high-voltage terminal 2 are connected to a high-voltage terminal of a low-temperature plasma power supply, and the ground terminal is connected to a low-voltage terminal of the low-temperature plasma power supply.

3. The low-temperature plasma reaction system according to claim 1, wherein the material of the gas pipe sleeve 1 and the gas pipe sleeve 2 is quartz glass or polytetrafluoroethylene.

4. The low-temperature plasma reaction system according to claim 1, wherein the tips of the needle electrodes 1 and 2 are spaced apart by 1-4 cm.

5. The method for preparing urea and liquid nitrogen fertilizer by using the low-temperature plasma reaction system as claimed in any one of claims 1 to 4, is characterized by comprising the following steps:

1) introducing nitrogen and hydrogen into a gas mixing chamber 1 through a gas mass flowmeter for mixing, and uniformly mixing to obtain mixed gas 1 which is introduced into a gas pipe sleeve 1 through a gas pump and the gas mass flowmeter;

2) meanwhile, hydrogen and carbon dioxide gas are introduced into the gas mixing chamber 2 through a gas mass flow meter to be mixed, and mixed gas 2 is obtained after uniform mixing and introduced into the gas pipe sleeve 2 through a gas pump and the flow meter;

3) and (2) switching on a low-temperature plasma power supply to perform low-temperature plasma treatment, wherein in the low-temperature plasma treatment process, solid matters generated in the reaction tank are recovered through a material receiving hopper and a material receiving groove, gas generated in the reaction tank is sent to a filter tank through a negative pressure pump to be discharged later, the recovered solid part is urea, and liquid in the filter tank is liquid fertilizer.

6. The method for preparing urea and a liquid nitrogen fertilizer by using the low-temperature plasma reaction system according to claim 5, wherein the volume ratio of the hydrogen to the nitrogen is 3-6: 1.

7. The method for preparing urea and liquid nitrogen fertilizer by using the low-temperature plasma reaction system according to claim 5, wherein the volume ratio of hydrogen to carbon dioxide is 2-4: 1.

8. The method for preparing urea and liquid nitrogen fertilizer by using the low-temperature plasma reaction system according to claim 5, wherein the volume ratio of the mixed gas 1 in the gas mixing chamber 1 to the mixed gas 2 in the gas mixing chamber 2 is 2-4: 1.

9. The method for preparing urea and liquid nitrogen fertilizer by using the low-temperature plasma reaction system according to claim 5, wherein the low-temperature plasma action voltage is 10-50 kV.

Technical Field

The invention relates to the field of research and development of nitrogen fixation environment-friendly technology, in particular to a method for preparing urea and liquid nitrogen fertilizer by using a low-temperature plasma reaction system.

Background

Nitrogen fertilizers play a very important role in the development of human society. The production of nitrogen fertilizer is a nitrogen fixation process. Urea, a commonly used nitrogen fertilizer, is usually synthesized from ammonia gas and carbon dioxide gas under specific temperature and pressure conditions, and the related equipment is complex and has long production period. Meanwhile, the production of urea consumes about 80% of ammonia worldwide, and is excessively dependent on ammonia. The nitrogen in the air accounts for 78%, and most of the nitrogen in the nature on the earth exists in the atmosphere in the form of nitrogen, which is less contained in the crust of the earth. Therefore, if nitrogen can be effectively utilized to realize the conversion of nitrogen into nitrogen fertilizer, the consumption of ammonia can be obviously reduced, and effective nitrogen fixation can be realized. However, due to the high binding energy of the nitrogen-nitrogen triple bond (940.95kJ/mol), the cracking and recombination of the nitrogen-nitrogen triple bond are carried out under the operating conditions of high temperature and high pressure or the highly efficient electrocatalytic environment. For example, the traditional Haber-Bosch process for ammonia production by fixed nitrogen and hydrogen consumes about 2% of the global energy annually. The existing electrocatalysis technology has the problems of hydrogen evolution reaction competition, complex preparation process of catalytic electrode materials, instability of catalytic materials, low electrocatalysis nitrogen fixation efficiency and the like.

Therefore, in combination with the above discussion, it is very critical to solve the above problems to develop a method for directly synthesizing urea by using nitrogen and carbon dioxide under normal temperature and pressure operation environment.

Disclosure of Invention

The purpose of the invention is as follows: the technical problem to be solved by the invention is a low-temperature plasma reaction system, which can enhance the ionization and dissociation effects of gas, improve the contact and collision efficiency of different free radicals, realize separation and recovery of generated different-phase products directly under the action of gravity and diffusion, and transfer the generated solid products into a receiving hopper through a receiving hopper.

The invention also aims to solve the technical problem of providing a method for preparing urea and liquid nitrogen fertilizer by using the low-temperature plasma reaction system.

The technical scheme is as follows: in order to solve the technical problem, the invention provides a low-temperature plasma reaction system which sequentially comprises a gas mixing chamber 1, a reaction area, a filter tank, a material receiving groove and a gas mixing chamber 2; the reaction zone comprises a high-voltage end 1, a reaction tank, a high-voltage end 2 and a grounding end, wherein the two ends in the reaction tank are respectively provided with a gas pipe sleeve 1 and a gas pipe sleeve 2 in parallel and in opposite directions, the end parts of the gas pipe sleeve 1 and the gas pipe sleeve 2 are open or distributed with air holes, a needle electrode 1 is arranged in the gas pipe sleeve 1, a needle electrode 2 is arranged in the gas pipe sleeve 2, the needle electrode 1 and the needle electrode 2 are parallel, collinear and arranged in opposite directions, the tips of the needle electrode 1 and the needle electrode 2 are opposite, the root of the needle electrode 1 is connected with the high-voltage end 1, the root of the needle electrode 2 is connected with the high-voltage end 2, a gas mixing chamber 1 leads gas into the gas pipe sleeve 1 through a gas pump and a gas mass flowmeter, the gas mixing chamber 2 leads the gas into the gas pipe sleeve 2 through the gas pump and the gas mass flowmeter, and gas, and liquid and solid products generated in the reaction area are transferred into a receiving hopper through a receiving funnel.

The high-voltage end 1 and the high-voltage end 2 are connected with the high-voltage end of the low-temperature plasma power supply, and the grounding end is connected with the low-voltage end of the low-temperature plasma power supply.

The gas pipe sleeve 1 and the gas pipe sleeve 2 are made of quartz glass or polytetrafluoroethylene.

Wherein the distance between the tips of the needle electrode 1 and the needle electrode 2 is 1-4 cm.

The invention also discloses a method for preparing urea and liquid nitrogen fertilizer by using the low-temperature plasma reaction system, which comprises the following steps:

1) introducing nitrogen and hydrogen into a gas mixing chamber 1 through a gas mass flowmeter for mixing, and uniformly mixing to obtain mixed gas 1 which is introduced into a gas pipe sleeve 1 through a gas pump and the gas mass flowmeter;

2) meanwhile, hydrogen and carbon dioxide gas are introduced into the gas mixing chamber 2 through a gas mass flow meter to be mixed, and mixed gas 2 is obtained after uniform mixing and introduced into the gas pipe sleeve 2 through a gas pump and the flow meter;

3) and (2) switching on a low-temperature plasma power supply to perform low-temperature plasma treatment, wherein in the low-temperature plasma treatment process, solid matters generated in the reaction tank are recovered through a material receiving hopper and a material receiving groove, gas generated in the reaction tank is sent to a filter tank through a negative pressure pump to be discharged later, the recovered solid part is urea, and liquid in the filter tank is liquid fertilizer.

Wherein the volume ratio of the hydrogen to the nitrogen is 3-6: 1.

Wherein the volume ratio of the hydrogen to the carbon dioxide is 2-4: 1.

Wherein the volume ratio of the mixed gas 1 in the gas mixing chamber 1 to the mixed gas 2 in the gas mixing chamber 2 is 2-4: 1.

Wherein the low-temperature plasma action voltage is 10-50 kV.

The reaction mechanism of the present invention: air holes are reserved at the root parts of the air pipe sleeve 1 and the air pipe sleeve 2 and are connected with a flowmeter, and the end parts of the air pipe sleeve 1 and the air pipe sleeve 2 are open or distributed with air holes, so that discharge channels generated by the tips of the needle-shaped electrode 1 and the needle-shaped electrode 2 are overlapped and different free radicals are fully contacted. The two trachea sleeves are parallel, collinear and arranged in opposite directions. The high-voltage end 1 and the high-voltage end 2 of the low-temperature plasma reaction tank are connected with the high-voltage end of a low-temperature plasma power supply, and the grounding end is connected with the low-voltage end of the low-temperature plasma power supply, so that low-temperature plasma irradiation is realized. The needle electrodes 1 and 2 in the low-temperature plasma reaction tank are arranged in parallel, collinear and opposite directions, the tips of the two needle electrodes are opposite, and the roots of the needle electrodes 1 and 2 are respectively connected with the high-voltage end 1 and the high-voltage end 2 of the low-temperature plasma reaction tank. The needle-shaped electrode and the gas pipe sleeve in the low-temperature plasma reaction tank are arranged in parallel, collinear and opposite directions, so that the superposition of discharge channels and the shortening of the migration distance of free radicals can be realized, the ionization and dissociation effects of gas can be enhanced, and the contact and collision efficiency of different free radicals can be improved. The products in different phases can be separated and recovered directly by gravity and diffusion. The produced liquid and solid products are transferred into a receiving groove through a receiving funnel. The gas phase product is sucked into the filter tank through a negative pressure pump. After the low-temperature plasma reaction system is started, the needle electrode 1 of the high-voltage end 1 generates a discharge channel (spark and arc) with high energy density at the needle end thereof. The hydrogen and nitrogen are ionized and dissociated in the discharge channel to generate hydrogen radicals and nitrogen radicals, and the hydrogen radicals and the nitrogen radicals are further combined to generate ammonia. Meanwhile, the needle electrode 2 of the high voltage end 2 generates a discharge channel (spark and arc) of high energy density at its needle end, and hydrogen gas and carbon dioxide gas are ionized and dissociated in the discharge channel to generate hydrogen radicals and carbon radicals, oxygen radicals. The hydrogen free radical, the carbon free radical, the oxygen free radical, the carbon dioxide and the ammonia gas are mixed and react in multiple channels to generate the urea. Most of the urea is condensed and precipitated, and a small part of the urea is introduced into the filter tank along with carbon dioxide, ammonia gas, hydrogen gas and nitrogen gas. Carbon dioxide and ammonia are dissolved in the water in the filter and form ammonium carbonate, and hydrogen and residual nitrogen are discharged to the atmosphere out of the filter.

Has the advantages that: the low-temperature plasma reaction system is environment-friendly, can enhance the ionization and dissociation effects of gas, can improve the contact and collision efficiency of different free radicals, can directly separate and recover the generated different-phase products through gravity and diffusion, and can transfer the generated solid products to the material receiving groove through the material receiving funnel to be fully utilized. The invention can obtain 89% nitrogen conversion rate and 43% urea generation rate at the highest. The liquid nitrogen fertilizer obtained by the invention can realize that the fertilizer prepared by the invention can effectively improve the species dry weight of rice. The invention provides a reference idea for the research and development of nitrogen fixation environment-friendly technology.

Drawings

FIG. 1 is a low temperature plasma reaction system.

Detailed Description

The invention is further described below with reference to the figures and examples.