Disclosure of Invention
The invention has been completed in order to at least partially solve the technical problem that the conversion rate of the silicon tetrachloride is difficult to further improve in the prior art.
The technical scheme adopted for solving the technical problem of the invention is as follows:
the invention provides a cold hydrogenation production method, which comprises the following steps:
carrying out primary reaction on the mixed gas of hydrogen and silicon tetrachloride and silicon powder;
and carrying out secondary reaction on the tail gas of the primary reaction and the silicon powder.
Optionally, before the step of reacting the mixed gas of hydrogen and silicon tetrachloride with the silicon powder for the first time, the method further comprises the following steps:
heating the hydrogen;
heating and vaporizing liquid silicon tetrachloride;
and mixing the heated hydrogen with the vaporized silicon tetrachloride according to a preset proportion to form a mixed gas of the hydrogen and the silicon tetrachloride.
Optionally, after the step of forming the mixed gas of hydrogen and silicon tetrachloride and before the step of reacting the mixed gas of hydrogen and silicon tetrachloride with silicon powder for the first time, the method further comprises the following steps:
the mixed gas of hydrogen and silicon tetrachloride is heated for the first time;
carrying out secondary heating on the mixed gas after the primary heating;
the mixed gas of hydrogen and silicon tetrachloride which is heated twice in sequence is reacted with the silicon powder for the first time.
Optionally, after the step of primarily heating the mixed gas of hydrogen and silicon tetrachloride and before the step of secondarily heating the primarily heated mixed gas, the method further comprises the following steps of:
performing heat exchange treatment on the mixed gas after primary heating by using the heat of part of tail gas of the primary reaction;
and carrying out secondary reaction on the part of tail gas subjected to heat exchange treatment and the rest of tail gas subjected to primary reaction and the silicon powder, and carrying out secondary heating on the mixed gas subjected to heat exchange treatment.
Optionally, after the step of performing the secondary reaction on the tail gas of the primary reaction and the silicon powder, the method further comprises the following steps:
and cooling the tail gas of the secondary reaction to separate out the mixture of trichlorosilane and silicon tetrachloride.
The present invention also provides a cold hydrogenation production system, which comprises:
the first-stage reactor is used for carrying out primary reaction on the mixed gas of hydrogen and silicon tetrachloride and silicon powder in the mixed gas;
and the secondary reactor is connected with the primary reactor and is used for carrying out secondary reaction on the tail gas of the primary reactor and the silicon powder in the secondary reactor.
Optionally, the cold hydrogenation production system further comprises:
the hydrogen heater is used for heating the hydrogen;
the silicon tetrachloride vaporizer is used for heating and vaporizing liquid silicon tetrachloride;
and the gas mixer is respectively connected with the hydrogen heater and the silicon tetrachloride vaporizer and is used for mixing the heated hydrogen output by the hydrogen heater and the vaporized silicon tetrachloride output by the silicon tetrachloride vaporizer according to a preset proportion to form a mixed gas of the hydrogen and the silicon tetrachloride.
Optionally, the cold hydrogenation production system further comprises:
the mixed gas primary heater is connected with the gas mixer and is used for heating the mixed gas of the hydrogen and the silicon tetrachloride output by the gas mixer for the first time;
the mixed gas secondary heater is connected with the mixed gas primary heater and is used for secondarily heating the primarily heated mixed gas output by the mixed gas primary heater;
and the mixed gas of hydrogen and silicon tetrachloride, which is heated by the mixed gas primary heater and the mixed gas secondary heater in sequence, enters the primary reactor and is subjected to primary reaction with the silicon powder in the primary reactor.
Optionally, the cold hydrogenation production system further comprises:
the mixed gas heat exchanger is respectively connected with the mixed gas primary heater, the mixed gas secondary heater and the primary reactor and is used for carrying out heat exchange treatment on the primarily heated mixed gas output by the mixed gas primary heater by utilizing the heat of part of tail gas of the primary reactor;
and the part of tail gas subjected to heat exchange treatment by the mixed gas heat exchanger and the rest of tail gas of the primary reactor enter the secondary reactor, the mixed gas subjected to heat exchange treatment by the mixed gas heat exchanger is output to the mixed gas secondary heater, and the mixed gas subjected to heat exchange treatment is secondarily heated by the mixed gas secondary heater.
Optionally, the cold hydrogenation production system further comprises:
and the cooler is connected with the secondary reactor and is used for cooling the tail gas of the secondary reactor so as to separate out the mixture of trichlorosilane and silicon tetrachloride.
Has the advantages that:
the invention optimizes the existing improved Siemens process, and the tail gas obtained by the primary reaction of the mixed gas of hydrogen and silicon tetrachloride and silicon powder is subjected to secondary reaction with the silicon powder, so that the contact time and the contact area of the mixed gas of hydrogen and silicon tetrachloride and the silicon powder are prolonged, and the reaction time of the mixed gas of hydrogen and silicon tetrachloride and the silicon powder is correspondingly prolonged, thereby effectively improving the conversion rate of the silicon tetrachloride and achieving the aim of further reducing the production cost.
Detailed Description
In order to make the technical solutions of the present invention better understood, the present invention is further described in detail below with reference to the accompanying drawings and examples.
The invention relates to a trichlorosilane production process, and the aim of improving the conversion rate of silicon tetrachloride can be achieved by using the production process, which is described in detail by specific embodiments below.
As shown in fig. 1, the present embodiment provides a cold hydrogenation production method, which includes the following steps S101 to S102.
S101, carrying out primary reaction on the mixed gas of hydrogen and silicon tetrachloride and silicon powder to generate a mixture of trichlorosilane and silicon tetrachloride.
And S102, carrying out secondary reaction on the tail gas of the primary reaction and the silicon powder.
The cold hydrogenation production method provided by the embodiment is optimized for the existing improved siemens process, and the tail gas obtained by carrying out the primary reaction on the mixed gas of hydrogen and silicon tetrachloride and the silicon powder is subjected to the secondary reaction on the silicon powder, so that the contact time and the contact area of the mixed gas of hydrogen and silicon tetrachloride and the silicon powder are prolonged, and the reaction time of the mixed gas of hydrogen and silicon tetrachloride and the silicon powder is correspondingly prolonged, thereby effectively improving the conversion rate of silicon tetrachloride and achieving the purpose of further reducing the production cost.
Before step S101, the following steps (c) to (c) may be further included.
Firstly, heating hydrogen;
heating and vaporizing the liquid silicon tetrachloride;
mixing the heated hydrogen with the vaporized silicon tetrachloride according to a preset proportion to form a mixed gas of the hydrogen and the silicon tetrachloride.
In practical application, because the reaction temperature for converting silicon tetrachloride into trichlorosilane is higher, in order to enable the reaction to be more sufficient, hydrogen and silicon tetrachloride need to be respectively heated in advance, and then the hydrogen and the silicon tetrachloride are mixed according to a certain proportion.
In this embodiment, the hydrogen gas is required to be preheated to 165-195 ℃, and the hydrogen gas can be heated by steam or electricity. The liquid silicon tetrachloride can be heated by electricity or by heat conduction oil or other heating media. The preset ratio is 2-2.5: 1, namely the molar ratio of the hydrogen to the silicon tetrachloride is 2-2.5: 1.
After the third step and before the step S101, the following fourth and fifth steps may be further included.
Fourthly, the mixed gas of the hydrogen and the silicon tetrachloride is heated for the first time;
fifthly, secondary heating is carried out on the mixed gas after primary heating.
And (4) carrying out primary reaction on the hydrogen and silicon tetrachloride mixed gas which is heated twice in sequence in the steps IV and V and the silicon powder.
In this embodiment, in order to ensure temperature uniformity, the preheated mixture of hydrogen and silicon tetrachloride needs to be heated twice and then reach the reaction temperature, and both the two heating modes can adopt electric heating. Wherein the temperature of the mixed gas after the primary heating is 300-350 ℃, and the temperature of the mixed gas after the secondary heating is 530-580 ℃.
Between the fourth step and the fifth step, the following steps can be included:
and performing heat exchange treatment on the mixed gas after primary heating by using the heat of part of the tail gas of the primary reaction, and performing secondary reaction on the part of the tail gas after heat exchange treatment and the rest of the tail gas of the primary reaction together with the silicon powder. And carrying out secondary heating on the mixed gas after heat exchange treatment.
In this embodiment, the heat of the partial tail gas of primary reaction is utilized to carry out heat exchange treatment on the gas mixture after primary heating, the heat of the tail gas of primary reaction is effectively utilized, and the energy consumption required by secondary heating is saved. Wherein the temperature of the mixed gas after heat exchange treatment is 450-510 ℃. In the tail gas of the primary reaction, 2000-25000m3The tail gas is used for carrying out heat exchange treatment on the mixed gas after primary heating, and the tail gas has the thickness of 100-3The tail gas directly reacts with the silicon powder for the second time.
After step S102, the following step (c) may be further included.
Cooling the tail gas of the secondary reaction to separate out the mixture of trichlorosilane and silicon tetrachloride.
In this embodiment, the tail gas of the secondary reaction contains some incompletely reacted hydrogen and silicon powder besides the mixture of trichlorosilane and silicon tetrachloride, and in order to recycle the mixture of trichlorosilane and silicon tetrachloride, the tail gas of the secondary reaction is cooled, the mixture of trichlorosilane and silicon tetrachloride in the tail gas of the secondary reaction can be separated, and then the mixture of trichlorosilane and silicon tetrachloride is conveyed to a rectification system to further purify and separate the mixture of trichlorosilane and silicon tetrachloride.
As shown in fig. 2, the present embodiment also provides a cold hydrogenation production method, which includes the following steps S201 to S209.
S201, heating the hydrogen.
In this step, the hydrogen gas is preheated to 165-195 ℃. The hydrogen gas can be heated by steam heating or electric heating.
S202, heating and vaporizing the liquid silicon tetrachloride.
In the step, the silicon tetrachloride is heated to be vaporized by adopting electric heating, and the liquid silicon tetrachloride can be heated by adopting heat conduction oil or other heating media to be vaporized.
S203, mixing the heated hydrogen with the vaporized silicon tetrachloride according to a preset proportion to form a mixed gas of the hydrogen and the silicon tetrachloride.
In the step, the preset ratio is 2-2.5: 1, namely the molar ratio of the hydrogen to the silicon tetrachloride is 2-2.5: 1.
And S204, carrying out primary heating on the mixed gas of the hydrogen and the silicon tetrachloride.
In the step, the temperature of the mixed gas after primary heating is 300-350 ℃.
S205, heat exchange treatment is carried out on the mixed gas after primary heating by using the heat of part of the tail gas of the primary reaction in the step S207.
In the step, the temperature of the mixed gas after heat exchange treatment is 450-510 ℃.
S206, secondary heating is carried out on the mixed gas after heat exchange treatment.
In the step, the temperature of the mixed gas after secondary heating is 530-580 ℃.
And S207, carrying out primary reaction on the mixed gas subjected to heat exchange treatment and silicon powder to generate a mixture of trichlorosilane and silicon tetrachloride.
And S208, carrying out secondary reaction on the part of tail gas subjected to heat exchange treatment in the step S205 and the rest of tail gas subjected to primary reaction and silicon powder.
In this step, in the tail gas of the primary reaction, 2000-25000m3The tail gas is used for the heat exchange part of the mixed gas after primary heating100-1000m3The tail gas directly reacts with the silicon powder for the second time.
S209, cooling the tail gas of the secondary reaction to separate out a mixture of trichlorosilane and silicon tetrachloride.
It should be noted that the sequence of the steps in the two embodiments is only a specific example provided for illustrating the two embodiments, and the present invention does not limit the sequence of the steps, and those skilled in the art can adjust the sequence as required in practical applications.
As shown in fig. 3, the present embodiment further provides a cold hydrogenation production system, which includes:
the primary reactor 7 is used for carrying out primary reaction on the mixed gas of hydrogen and silicon tetrachloride and silicon powder in the mixed gas (namely, the silicon powder is preset in the primary reactor 7);
and the secondary reactor 8 is connected with the primary reactor 7 and is used for carrying out a secondary reaction on the tail gas of the primary reactor 7 and the silicon powder in the secondary reactor (namely, the silicon powder is preset in the secondary reactor 8).
In this embodiment, both the primary reactor and the secondary reactor may be fluidized bed reactors. The cold hydrogenation production system is optimized aiming at the existing improved Siemens process, and a first-stage fluidized bed reactor and a second-stage fluidized bed reactor are connected in series, namely, high-temperature tail gas at the outlet of the first-stage fluidized bed reactor is conveyed into the second-stage fluidized bed reactor to carry out secondary reaction with silicon powder in the second-stage fluidized bed reactor, so that the retention time of the mixed gas of hydrogen and silicon tetrachloride in a fluidized bed is prolonged, the contact time and the contact area of the mixed gas of hydrogen and silicon tetrachloride and the silicon powder are prolonged, the reaction time of the mixed gas of hydrogen and silicon tetrachloride and the silicon powder is correspondingly prolonged, the conversion rate of the silicon tetrachloride is effectively improved, and the aim of further reducing the production cost is fulfilled.
As shown in fig. 3, the cold hydrogenation production system may further include:
a hydrogen heater 1 for heating hydrogen;
the silicon tetrachloride vaporizer 2 is used for heating and vaporizing liquid silicon tetrachloride;
and the gas mixer 3 is respectively connected with the hydrogen heater 1 and the silicon tetrachloride vaporizer 2 and is used for mixing the heated hydrogen output by the hydrogen heater 1 with the vaporized silicon tetrachloride output by the silicon tetrachloride vaporizer 2 according to a preset proportion to form a mixed gas of the hydrogen and the silicon tetrachloride.
In practical application, because the reaction temperature for converting silicon tetrachloride into trichlorosilane is higher, in order to enable the reaction to be more sufficient, hydrogen and silicon tetrachloride need to be respectively heated in advance, and then the hydrogen and the silicon tetrachloride are mixed according to a certain proportion.
In this embodiment, the hydrogen gas is preheated to 165-195 ℃ by the hydrogen heater 1, and the hydrogen gas is heated by the hydrogen heater 1 by steam heating or electric heating. The silicon tetrachloride vaporizer 2 can heat the liquid silicon tetrachloride by adopting electric heating, and can also heat the liquid silicon tetrachloride by adopting heat conduction oil or other heating media. The preset ratio is 2-2.5: 1, namely the molar ratio of the hydrogen to the silicon tetrachloride is 2-2.5: 1.
As shown in fig. 3, the cold hydrogenation production system may further include:
the mixed gas primary heater 4 is connected with the gas mixer 3 and is used for heating the mixed gas of the hydrogen and the silicon tetrachloride output by the gas mixer 3 for the first time;
and the mixed gas secondary heater 6 is connected with the mixed gas primary heater 4 and is used for secondarily heating the primarily heated mixed gas output by the mixed gas primary heater 4.
The hydrogen and silicon tetrachloride mixed gas which is heated twice by the mixed gas primary heater 4 and the mixed gas secondary heater 6 sequentially enters the primary reactor 7 to react with the silicon powder in the primary reactor.
In this embodiment, in order to ensure temperature uniformity, the mixture of hydrogen and silicon tetrachloride output by the gas mixer 3 needs to be heated by the mixture primary heater 4 and the mixture secondary heater 6 twice in sequence, and then reaches the reaction temperature, and the mixture primary heater 4 and the mixture secondary heater 6 can both heat the mixture by electric heating. Wherein the temperature of the mixed gas output by the mixed gas primary heater 4 is 300-350 ℃, and the temperature of the mixed gas output by the mixed gas secondary heater 6 is 530-580 ℃.
As shown in fig. 3, the cold hydrogenation production system may further include:
and the mixed gas heat exchanger 5 is respectively connected with the mixed gas primary heater 4, the mixed gas secondary heater 6 and the primary reactor 7, and is used for performing heat exchange treatment on the primarily heated mixed gas output by the mixed gas primary heater 4 by using the heat of part of tail gas of the primary reactor 7.
And the part of tail gas subjected to heat exchange treatment by the mixed gas heat exchanger 5 and the rest of tail gas of the primary reactor 7 enter the secondary reactor 8, the mixed gas subjected to heat exchange treatment by the mixed gas heat exchanger 5 is output to the mixed gas secondary heater 6, and the mixed gas subjected to heat exchange treatment is secondarily heated by the mixed gas secondary heater 6.
In this embodiment, the mixed gas heat exchanger 5 performs heat exchange treatment on the mixed gas output by the mixed gas primary heater 4 by using the heat of part of the tail gas output by the primary reactor 7, so that the heat of the tail gas of the primary reactor 7 is effectively utilized, and meanwhile, the energy consumption required by the mixed gas secondary heater 6 is saved. Wherein the temperature of the mixed gas subjected to heat exchange treatment by the mixed gas heat exchanger 5 is 450-510 ℃. 2000-25000m in the tail gas of the first-stage reactor 73The tail gas is output to a mixed gas heat exchanger 5 for heat exchange treatment of the mixed gas output by the mixed gas primary heater 4, 100-1000m3The tail gas directly enters a secondary reactor 8 to carry out secondary reaction with the silicon powder in the secondary reactor.
As shown in fig. 3, the cold hydrogenation production system may further include:
and the cooler 9 is connected with the secondary reactor 8 and is used for cooling the tail gas of the secondary reactor 8 so as to separate out a mixture of trichlorosilane and silicon tetrachloride.
In this embodiment, the tail gas of the secondary reactor 8 contains some incompletely reacted hydrogen and silicon powder besides the mixture of trichlorosilane and silicon tetrachloride, and in order to recycle the mixture of trichlorosilane and silicon tetrachloride, the tail gas of the secondary reactor 8 is cooled by the cooler 9, and the mixture of trichlorosilane and silicon tetrachloride in the tail gas can be separated out and then is conveyed to the rectification system to further purify and separate the mixture of trichlorosilane and silicon tetrachloride.
The process flow of the cold hydrogenation production system is described in detail below with reference to fig. 3:
heating hydrogen to 165-, wherein 2000-25000m3The tail gas enters a mixed gas heat exchanger 4 to heat the mixed gas, wherein the mixed gas is 100-1000m3The tail gas directly enters the secondary reactor 8 and reacts with the silicon powder again in the secondary reactor 8 so as to prolong the contact time of the mixed gas and the silicon powder and prolong the reaction time of the mixed gas and the silicon powder, thereby improving the conversion rate of the silicon tetrachloride. And after being cooled by a cooler 9, the tail gas of the secondary reactor 8 is conveyed to a rectification system for further purifying and separating the mixture of the silicon tetrachloride and the trichlorosilane.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.