CN108862322B

CN108862322B - Preparation method of lime nitrogen

Info

Publication number: CN108862322B
Application number: CN201810665527.4A
Authority: CN
Inventors: 马韵升; 张超; 梁万根; 孙志利; 张宁; 崔卫华
Original assignee: Shandong Efirm Biochemistry and Environmental Protection Co Ltd
Current assignee: Yifeng New Material Co.,Ltd.
Priority date: 2018-06-25
Filing date: 2018-06-25
Publication date: 2020-06-26
Anticipated expiration: 2038-06-25
Also published as: CN108862322A

Abstract

The invention belongs to the field of chemical industry, and particularly relates to a method for preparing lime nitrogen by using low-temperature plasma, which comprises the steps of ionizing a mixed gas of carbon monoxide and ammonia gas by using gas discharge, and reacting the plasma with calcium oxide to generate the lime nitrogen; the low-temperature plasma method adopted by the invention has the advantages of low reaction temperature, low energy consumption, short preparation time and the like.

Description

Preparation method of lime nitrogen

Technical Field

The invention belongs to the field of chemical industry, and particularly relates to a preparation method of lime nitrogen.

Background

Calcium cyanamide also known as calx nitrogen (CaCN)₂) It is an alkaline fertilizer, one of the main raw materials of high-effective low-toxic carbendazim pesticide, can be used as weedicide, fungicide and pesticide, and can be used for producing dicyandiamide, melamine and cyanogen melt. Besides being used as a nitrogen fertilizer in agriculture, the fertilizer also has the effects of increasing ground temperature, killing insects, weeding, improving acidity of soil and the like. The number of manufacturers in China is more than 30, the annual output is 27 ten thousand tons, but with the development of market economy, the market of common lime nitrogen is over-supplied, and the development prospect of the lime nitrogen as industrial lime nitrogen is increasingly unattractive. In order to find a new economic growth point, many manufacturers aim at the field of agricultural lime nitrogen, so that the market of the agricultural lime nitrogen is further developed.

The conventional preparation method is prepared by adopting calcium carbide and calcium chloride as raw materials and reacting the raw materials with nitrogen at high temperature in a nitriding furnace, the conventional method for producing the lime nitrogen has serious environmental pollution, high energy consumption, long production period and complex process control, and is difficult to meet the requirements of new and old kinetic energy conversion, so that how to provide a low-cost and more convenient lime nitrogen preparation method becomes one of the problems to be solved urgently in the prior art.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a method for preparing lime nitrogen by using low-temperature plasma, which comprises the steps of ionizing a mixed gas of carbon monoxide and ammonia gas by using gas discharge, and reacting the plasma with calcium oxide to generate the lime nitrogen; the low-temperature plasma method adopted by the invention has the advantages of low reaction temperature, low energy consumption, short preparation time and the like.

The invention is realized by the following technical scheme:

the plasma is a fourth existing form of substance, is rich in various ions, electrons, excited atoms, molecules, radicals and other extremely active and highly active species, and is a fluid with conductivity. The energy of the energetic particles in the plasma is typically a few to tens of electron volts (eV), sufficient to provide the activation energy required for the chemical reaction. The invention adopts low-temperature plasma to prepare calcium cyanamide, and utilizes excited molecules, ions, free radicals and the like generated by the excitation of the plasma on carbon monoxide and ammonia gas to interact with calcium oxide under mild conditions to generate lime nitrogen.

The specific technical scheme of the invention is as follows:

a preparation method of lime nitrogen comprises the following steps:

c) uniformly placing calcium oxide particles in a discharge reactor, and introducing nitrogen for replacement for 10 minutes;

d) and introducing plasma discharge gas at normal temperature and normal pressure, discharging the gas by using high voltage provided by a high-voltage power supply at two ends of the electrode, reacting the formed plasma with calcium oxide, and controlling the reaction time to be 2-4 hours.

Wherein the plasma discharge gas is a mixed gas of carbon monoxide and ammonia gas;

preferably: the calcium oxide: the molar ratio of carbon monoxide to ammonia gas is 1:2:4 to 1:2:8, more preferably 1:2: 6;

the calcium oxide is one or more of powdery calcium oxide, superfine calcium oxide and high-purity calcium oxide, and preferably the high-purity calcium oxide; and the particle size of the calcium oxide particles is required to be further limited to be 40-400 meshes.

The voltage of the high-voltage power supply is controlled to be 3000-6000V, the power supply can be selected from an alternating current power supply, a direct current power supply can also be directly adopted, and generally a transformer is needed for boosting to meet the voltage requirement.

The reaction process of the invention is as follows: in the low-temperature plasma, high-energy electrons and carbon monoxide and ammonia molecules generate inelastic collision, and the energy of the electrons is transferred to the latter so as to excite the electrons to generate excited molecules, ions, free radicals and the like. Because the excited species in the plasma are very active chemically, calcium oxide is easy to react under the collision action of the excited species in the plasma. Therefore, calcium cyanamide can be produced by the interaction of calcium oxide with plasmas of carbon monoxide and ammonia under mild conditions.

In the prior art, the conventional energy supply method is high temperature, but the energy consumption of the method is high, the low-temperature plasma can generate high-energy ions and has the similar effect with the high temperature, and the low-temperature plasma has the advantages of low energy consumption and the like.

The quantity and the carried energy of the plasmas generated by the method are positively correlated with the voltage, the higher the voltage is, the higher the energy of the plasmas is, but for the convenience of production, the voltage is controlled to be in the range, the temperature of the plasmas generated by the method is maintained to be 80-120 ℃, the reaction time is controlled to be 2-4 hours, and the yield is over 80 percent. The purity reaches more than 85 percent, which is far higher than about 65 percent of the prior art.

In conclusion, the method for preparing the lime nitrogen by using the low-temperature plasma in the field for the first time has the advantages of low reaction temperature, low energy consumption, short preparation time and the like.

The specific implementation mode is as follows:

the invention is further described below by way of examples, which are not intended to limit the present invention further. It will be understood by those skilled in the art that equivalent substitutions for the technical features of the present invention, or corresponding modifications, can be made within the scope of the present invention.

Example 1

30g of calcium oxide sample with the granularity of 40-60 meshes and the content of 99 percent is placed in a cavity between a quartz glass tube and a high-voltage electrode of a plasma reactor, and nitrogen is introduced for 10 minutes to remove air in the reactor; controlling by a mass flow meter to ensure that the molar ratio is 2: 1, passing the mixed gas of ammonia and carbon monoxide through a calcium oxide bed layer at the flow rate of 600 mL/min; and (3) switching on a plasma power supply connected with a high-voltage electrode, controlling the voltage to be about 5000V, reacting for 2.0 hours, and turning off a flowmeter and the plasma power supply to obtain 40.1g of calcium cyanamide, wherein the effective nitrogen content is 30.2%, the purity is 86.3%, and the yield is 81.5%.

Example 2

30g of a calcium oxide sample having a particle size of 80 to 100 mesh and a content of 99% was placed in a cavity between a quartz glass tube and a high-voltage electrode of a plasma reactor, and nitrogen gas was introduced for 10 minutes to remove air in the reactor. Controlling by a mass flow meter to ensure that the molar ratio is 3: 1, the mixed gas of ammonia and carbon monoxide is passed through the calcium oxide bed at a flow rate of 800 mL/min. Connecting a plasma power supply connected with a high-voltage electrode, controlling the voltage to be about 6000V, reacting for 2.0 hours, turning off a flowmeter and the plasma power supply, and preparing 40.8g of calcium cyanamide, 30.6 percent of effective nitrogen, 87.4 percent of purity and 84.1 percent of yield

Example 3

30g of calcium oxide sample with the granularity of 200-400 meshes and the content of 99 percent is placed in a cavity between a quartz glass tube and a high-voltage electrode of a plasma reactor, and nitrogen is introduced for 10 minutes to remove air in the reactor; controlled by a mass flow meter, the molar ratio is 4: the mixed gas of ammonia and carbon monoxide of 1 is passed through the calcium oxide bed at a flow rate of 600 mL/min. And (3) switching on a plasma power supply connected with a high-voltage electrode, controlling the voltage to be about 3000V, reacting for 3.0 hours and 20 minutes, and turning off a flowmeter and the plasma power supply to obtain 39.8g of calcium cyanamide, wherein the effective nitrogen content is 30.1%, the purity is 86.0%, and the yield is 80.6%.

Example 4

30g of calcium oxide sample with the particle size of 100-200 meshes and the content of 99 percent is placed in a cavity between a quartz glass tube and a high-voltage electrode of a plasma reactor, and nitrogen is introduced for 10 minutes to remove air in the reactor. Controlled by a mass flow meter, the molar ratio is 4: 1 of ammonia and carbon monoxide was passed through the calcium oxide bed at a flow rate of 500 mL/min. And (3) switching on a plasma power supply connected with a high-voltage electrode, wherein the voltage is about 5000V, reacting for 4.0 hours, and turning off a flowmeter and the plasma power supply to prepare 40.5g of calcium cyanamide, 30.3% of effective nitrogen, 86.6% of purity and 82.6% of yield.

It can be seen that the purity and yield of the calcium cyanamide prepared by the invention are obviously higher than those of the prior art.

Claims

1. The preparation method of lime nitrogen is characterized by comprising the following steps: the method comprises the following specific steps:

a) uniformly placing calcium oxide particles in a discharge reactor, and introducing nitrogen for replacement for 10 minutes;

b) introducing plasma discharge gas at normal temperature and normal pressure, discharging the gas by using high voltage provided by a high-voltage power supply at two ends of an electrode, reacting the formed plasma with calcium oxide, maintaining the temperature of the plasma at 80-120 ℃, and controlling the reaction time at 2-4 hours;

wherein the plasma discharge gas is a mixed gas of carbon monoxide and ammonia gas; the calcium oxide: the molar ratio of carbon monoxide to ammonia gas is 1:2:4-1:2: 8;

the particle size of the calcium oxide particles is 40-400 meshes;

the voltage of the high-voltage power supply is controlled at 3000-6000V, and the power supply is selected from an alternating current power supply or a direct current power supply.

2. The method for preparing lime nitrogen according to claim 1, characterized in that: the calcium oxide: the molar ratio of carbon monoxide to ammonia gas is 1:2: 6.