阅读说明：本技术 一种氯氢化流化床热能回收工艺 (Heat energy recovery process for chlorohydrination fluidized bed ) 是由 周复礼 王永亮 谢岩 沈峰 胡永吉 于 2020-06-29 设计创作，主要内容包括：本发明公开一种氯氢化流化床热能回收工艺,包括如下步骤：采用多股流缠绕管式换热器作为流化床热交换器,SiCl<Sub>4</Sub>通过原料泵直接进入流化床热交换器的独立中心筒体汽化,汽化后的SiCl<Sub>4</Sub>进入流化床热交换器壳程进行换热升温,常温H<Sub>2</Sub>进入流化床热交换器壳程换热升温后与升温后的气相SiCl<Sub>4</Sub>混合,然后一起进入电加热器进一步加热,最后SiCl<Sub>4</Sub>和H<Sub>2</Sub>混合气进入FBR反应器中与硅粉发生氯氢化反应生成三氯氢硅。本发明方法整个FBR反应前的工艺流程更加简洁,不需要设计预热器、气化器设备,不需设计单程列管换热器,同时,FBR出口热物流热交换后温度降低,更有利于后冷凝系统,减少冷量投入,FBR出口热物流能量回收量达到16086KW,FBR反应前较原工艺节能1042KW。(The invention discloses a heat recovery process of a chlorohydrination fluidized bed, which comprises the following steps: the multi-strand wound tube heat exchanger is used as a fluidized bed heat exchanger, SiCl 4 Directly enters an independent central cylinder of a fluidized bed heat exchanger through a raw material pump for vaporization, and the vaporized SiCl 4 Entering a shell side of a fluidized bed heat exchanger for heat exchange and temperature rise at normal temperature H 2 Gas phase SiCl entering the shell side of the fluidized bed heat exchanger for heat exchange and heating 4 Mixing, heating in electric heater, and mixing with SiCl 4 And H 2 The mixed gas enters an FBR reactor to perform a chlorine hydrogenation reaction with the silicon powder to generate trichlorosilane. The method has the advantages that the whole process flow before FBR reaction is simpler, a preheater and gasifier equipment do not need to be designed, a one-way tube-in-tube heat exchanger does not need to be designed, and meanwhile, an FBR outlet is providedThe temperature is reduced after the heat exchange of the hot logistics, the post-condensation system is more facilitated, the cold input is reduced, the energy recovery amount of the FBR outlet hot logistics reaches 16086KW, and before the FBR reaction, the energy is saved by 1042KW compared with the original process.)

1. The heat energy recovery process of the chlorohydrination fluidized bed is characterized by comprising the following steps: the multi-strand wound tube heat exchanger is used as a fluidized bed heat exchanger, SiCl₄Directly enters an independent central cylinder of a fluidized bed heat exchanger through a raw material pump for vaporization, and the vaporized SiCl₄Entering a shell side of a fluidized bed heat exchanger for heat exchange and temperature rise at normal temperature H₂Gas phase SiCl entering the shell side of the fluidized bed heat exchanger for heat exchange and heating₄Mixing, heating in electric heater, and mixing with SiCl₄And H₂The mixed gas enters a fluidized bed reactor to perform a chlorine hydrogenation reaction with the silicon powder to generate the hydrogen trichlorideSilicon.

2. The heat recovery process of the chlorohydrination fluidized bed according to claim 1, wherein normal temperature hydrogen enters a fluidized bed heat exchanger shell side for heat exchange and is heated to 140-150 ℃.

3. The chlorohydrination fluidized bed heat energy recovery process of claim 1, wherein SiCl₄The raw material is pressurized to 38-40 bar by a raw material pump and conveyed to a central cylinder through a pipeline for vaporization, and the temperature after vaporization is 210-230 ℃.

4. The chlorohydrination fluidized bed heat energy recovery process of claim 1, wherein SiCl₄And H₂Heating the mixed gas to 550-555 ℃ by electric heating.

5. The chlorohydrination fluidized bed heat energy recovery process of claim 1, wherein SiCl₄And H₂The mixing molar ratio is 2.5-3: 1.

6. The heat recovery process of the chlorohydrination fluidized bed as claimed in claim 1, wherein a slag discharge port is designed at the bottom of the central cylinder of the fluidized bed heat exchanger for performing slag discharge operation regularly and quantitatively.

7. The chlorohydrination fluidized bed heat energy recovery process of claim 6, wherein the slag discharge port is arranged every 10-12 hours.

8. The heat recovery process of claim 1, wherein a temperature setting device is provided at the tube side outlet of the fluidized bed heat exchanger for controlling the tube side outlet temperature of the fluidized bed heat exchanger.

9. The heat energy recovery process of the chlorohydrination fluidized bed according to claim 1, wherein the design of the outlet hot material flow tube pass coil of the fluidized bed heat exchanger is that the flow velocity of the coil is 18-23 m/s.

Technical Field

The invention belongs to a heat energy recovery process, and particularly relates to a heat energy recovery process of a chlorohydrination fluidized bed.

Background

In the chlorine hydrogenation process, the most central one is heat recycling, and the heat recycling is mainly heat recycling of hot streams at an outlet of a fluidized bed reactor (FBR for short) besides heat recycling of a top material of a query (called a washing tower and a quenching tower). SiCl4 and H₂The feed design is increasingly larger, and the recycling of heat of the outlet hot stream of the FBR becomes more critical.

The hydrochlorination process uses fluidized bed as main reactor and hydrogen (H)₂) Reacting with Silicon Tetrachloride (STC) gas phase and solid-phase silicon powder in a fluidized bed to generate Trichlorosilane (TCS), and feeding H in the fluidized bed₂Heating the STC two material flows to 550 ℃ by gradually increasing the grade of a heat source, wherein the gas after the reaction at the outlet of the fluidized bed comprises H₂STC, TCS and the like are collectively called as chlorosilane gas, the chlorosilane gas at the temperature of about 540 ℃ is condensed and separated by using a cold source step by step, the heat energy of the chlorosilane gas at the outlet of the fluidized bed is fully utilized in different grades by using the principle of pinch point thermodynamics, and the remarkable energy-saving effect can be realized.

The current 25wt/a device FBR outlet hot stream heat recovery process comprises the following steps: 25wt/a device, SiCl, as shown in FIG. 1₄The feed rate of (1) is 150t/h, SiCl₄And H₂After being mixed, the mixture is vaporized and enters an FBR outlet heat exchanger for heating, then the mixture is put into an electric heater for final heating to 550 ℃, and SiCl is added₄And H₂Mixed gas enters an FBR reactor to perform a chlorine hydrogenation reaction with silicon powder to generate Trichlorosilane (TCS), a heat exchanger adopts a counter-current heat exchange single-stage mode, ASPEN software is used for simulation, the hot material flow energy at an FBR outlet is recovered by 15044KW, and the accounting result is shown in Table 1:

TABLE 1

The prior art has the following defects:

(1) the energy recovery amount of hot logistics at the outlet of an FBR in the prior art is small, the maximum recovered heat amount of 15044KW is mainly limited by process design and heat exchange equipment, and the process design has the advantages that hot public engineering is used for heating before heat exchange of cold logistics, so that the heat energy recovery amount is reduced; the tubular heat exchanger is restricted by the length, stress and the like of the tube bundle, the temperature difference is designed to be 18-25 ℃, and the recovered heat energy is less;

(2) the temperature difference stress of the FBR outlet heat exchanger is large, the equipment investment and the leakage risk are increased, the problem is usually solved by arranging expansion joints on a shell pass, allowance needs to be reserved during the design of the temperature difference stress, for example, 2 or even 3 expansion joints are arranged to relieve the temperature difference stress under various working conditions, and the equipment cost is greatly improved;

(3) in the prior art, the temperature of an auxiliary pipeline of an FBR outlet heat exchanger is high, the stress problem exists, the pipeline design is generally required to be combined with professional stress analysis, otherwise, pipeline cracks are easily caused to further influence the long-period operation of the device;

(4) silica powder is entrained in the hot material flow at the outlet of the FBR, the tube bundle of the tubular heat exchanger is easily blocked by the silica powder, and the attenuation of the recovered heat energy of the FBR outlet heat exchanger is more.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the defects in the prior art, the invention develops and designs a new heat recovery process aiming at the outlet heat flow of the FBR.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a heat energy recovery process of a chlorohydrination fluidized bed comprises the following steps: the multi-strand wound tube heat exchanger is used as a fluidized bed heat exchanger, SiCl₄Directly enters an independent central cylinder of a fluidized bed heat exchanger through a raw material pump for vaporization, and the vaporized SiCl₄Entering a shell side of a fluidized bed heat exchanger for heat exchange and temperature rise at normal temperature H₂Gas phase SiCl entering the shell side of the fluidized bed heat exchanger for heat exchange and heating₄Mixing, heating in electric heater, and mixing with SiCl₄And H₂The mixed gas enters a fluidized bed reactor to perform a chlorine hydrogenation reaction with the silicon powder to generate trichlorosilane. By adopting the multi-strand wound tube type heat exchanger and by means of the curve winding design of the heat exchange tube, the difficult problem of thermal expansion is solved, and meanwhile, the normal temperature H is achieved₂Mixing with heated STC after heating to prevent H at normal temperature₂And the gas phase STC is directly mixed with the gas phase STC to generate liquid phase STC, and the liquid phase STC is directly gasified on the surface of the coil pipe to damage the coil pipe.

Specifically, normal temperature hydrogen enters a fluidized bed heat exchanger shell side for heat exchange and is heated to 140-150 ℃.

SiCl₄The pressure is increased to 38-40 bar by a raw material pump, and the raw material is conveyed to a central cylinder body through a pipeline to be vaporized, wherein the temperature after vaporization is 210-230 ℃. The gas phase STC enters the shell side of the heat exchanger through a communicating pipeline to carry out heat exchange and temperature rise.

In particular, SiCl₄And H₂The mixed gas is heated to 550-555 ℃ by electric heating.

Wherein, SiCl₄And H₂The mixing molar ratio is 2.5-3: 1.

Preferably, a slag discharge port is designed at the bottom of the central cylinder of the fluidized bed heat exchanger, and slag discharge operation is carried out regularly and quantitatively.

Preferably, the slag discharge port is arranged once every 10 to 12 hours. Assuming that the vaporization amount of an independent center cylinder body STC of the fluidized bed heat exchanger is 125-150 t/h, trace metal impurities (B, P, Fe, Al, Ca and the like) contained in the STC are continuously enriched, the estimation is carried out according to the trace impurities being 200PPb, 600-720 g of trace elements are enriched after the center cylinder body STC of the 24h heat exchanger is vaporized, if the enriched trace metal impurities are not discharged in time, a pipeline is blocked, a slag discharge port is designed at the bottom of the center cylinder body of the heat exchanger, and slag discharge operation is carried out regularly and quantitatively (1 time of discharge every 12h and 0.2-0.5 t of discharge once), so that the trace metal impurities are prevented from being enriched.

Further preferably, a temperature setting device is provided at the tube side outlet of the fluidized bed heat exchanger for controlling the temperature of the tube side outlet of the fluidized bed heat exchanger. The temperature is a temperature range obtained by combining the material properties of the product and experimental investigation. Material(s)Trace metal impurities in the solution form metal chlorides in which AlCl₃Precipitation of AlCl theoretically occurs at 173 ℃₃The crystallization on the inner wall of the pipeline leads to the reduction of heat exchange efficiency and even the blockage of the pipeline, and AlCl passes the test₃The reduction of the precipitation temperature in the hydrogen atmosphere to what extent is the key data for the outlet temperature setting of the fluidized bed heat exchanger. The temperature of the tube pass inlet of the FBR heat exchanger is determined to be 540 ℃ from the main reaction temperature, the temperature of the tube pass outlet is determined from the physical property of an FBR outlet medium, the protection design of a common process kit is 180 ℃, and thus the heat exchanger can be designed to fully recover the heat energy of the FBR outlet heat stream in the range of 180-540 ℃. However, the design of the invention reduces the outlet temperature of the tube side to 155 ℃, so that the outlet temperature of the tube side is set to 155 ℃, the heat exchanger can still keep normal and efficient operation, and the heat energy of the FBR outlet heat flow in the range of 155-540 ℃ can be completely recovered.

Further preferably, the design of the outlet hot material flow tube pass coil of the fluidized bed heat exchanger is that the flow velocity of the coil is designed to be 18-23 m/s. The curvature of the coil pipe enables the inertia force and the centrifugal force of fluid in the pipe to be unbalanced, secondary flow occurs on the cross section of the groove, turbulence is increased, heat transfer efficiency is improved, and meanwhile self-descaling capacity is improved.

Has the advantages that: compared with the prior art, the invention has the following advantages:

(1) the STC enters the winding heat exchanger to be vaporized, and meanwhile, a slag discharging port is designed at the bottom of the central cylinder of the heat exchanger to perform slag discharging operation regularly and quantitatively so as to prevent trace metal impurities in the STC from being enriched and blocking the heat exchanger.

(2) The temperature of the outlet of the tube pass of the FBR heat exchanger is set, and is influenced by the physical properties of a medium at the outlet of the FBR, so that the temperature is set to be high, the heat energy recovery is less, the temperature is set to be low, and aluminum chloride in the medium is separated out to block a coil; the FBR heat exchanger tube side inlet temperature is determined to be 540 ℃ from the main reaction temperature, the FBR outlet temperature is determined from the physical property of an FBR outlet medium, the protection design of a process kit is usually 180 ℃, and thus the heat exchanger can be designed to fully recover the heat energy of the FBR outlet heat stream in the range of 180-540 ℃. However, the design of the invention reduces the outlet temperature of the tube pass to 155 ℃, the heat exchanger can still keep normal and efficient operation, and the heat energy of the FBR outlet heat flow in the range of 155-540 ℃ can be completely recovered.

(3) According to the design of the multi-strand wound tube type heat exchanger, normal-temperature STC directly enters the heat exchanger for vaporization and temperature rise, the heat flow energy at the outlet of a Fluidized Bed Reactor (FBR) is effectively recovered, the heat efficiency is improved, the heat exchange area is reduced, the problem of thermal expansion is solved, the temperature difference gradient between the heat flow temperature at the inlet of a tube side and the cold flow at the outlet of a shell side after the process is optimized is about 110 ℃, and the temperature difference between the heat flow at the tube side and the cold flow at the shell side of the fluidized bed heat exchanger is larger, the heat exchange area of equipment is smaller, and the whole equipment is reduced.

(4) The design of the hot material flow pass coil pipe at the outlet of a Fluidized Bed Reactor (FBR) is that the flow velocity of the coil pipe is designed to be 18-23 m/s, the curvature of the coil pipe enables the inertia force and the centrifugal force of fluid in the pipe to be unbalanced, secondary flow occurs on the cross section of a groove, turbulence is increased, the heat transfer efficiency is improved, and the self-descaling capacity is improved

(5) The FBR heat exchanger exchanges heat with liquid STC, the vaporization latent heat of the liquid STC is about 8332KW, and the heat exchanger design is reduced and the equipment investment is reduced because the temperature difference between the vaporization temperature and the FBR heat stream is large;

(6) after gasification, STC enters a shell pass at the temperature of about 210 ℃ and H is at normal temperature₂Enters a shell pass, is mixed with STC after heat exchange and temperature rise to prevent H at normal temperature₂Directly mixing with gas-phase STC to generate liquid-phase STC, and directly gasifying the liquid-phase STC on the surface of the coil pipe to damage the coil pipe;

(7) the whole process flow before FBR reaction is more concise, a preheater and gasifier equipment do not need to be designed, 3 single-pass tube-array heat exchangers do not need to be designed, the temperature of the FBR outlet hot material flow after heat exchange is reduced to 155 ℃, and compared with the original process of 180 ℃, the process flow is more beneficial to a post-condensation system, and the cold input is reduced.

Drawings

FIG. 1 is a schematic diagram of a prior art FBR outlet hot stream heat recovery process;

FIG. 2 is a schematic diagram of a heat recovery device for an outlet hot stream of a FBR in the prior art;

FIG. 3 is a schematic view of the heat recovery process apparatus of the fluid bed for chlorine hydrogenation in example 1.

Detailed Description

The present invention will be described in further detail with reference to specific examples. The examples will help to understand the present invention given the detailed embodiments and the specific operation procedures, but the scope of the present invention is not limited to the examples described below.

As shown in FIG. 3, the present invention provides a heat energy recovery process for a chlorohydrination fluidized bed, which adopts a multi-stream winding tube type heat exchanger as a fluidized bed heat exchanger, taking a 25wt/a device as an example, SiCl₄The feed rate of (1) is 150t/h, SiCl₄Pressurizing to 38-40 bar by a raw material pump, conveying to an independent central cylinder of the FBR heat exchanger through a pipeline for gasification, and performing gasification at the temperature of 210-230 ℃ and the normal temperature H₂Entering a fluidized bed heat exchanger shell pass for heat exchange, raising the temperature to 140-150 ℃, gasifying the heated STC and the heated H₂The mixed materials are mixed according to the mol ratio of 2.5-3: 1, enter a shell side of an FBR heat exchanger and are continuously heated to 430 ℃, then are fed into an electric heater and are finally heated to 550 ℃, and SiCl is added₄And H₂The mixed gas enters an FBR reactor to perform a hydrochlorination reaction with silicon powder to generate Trichlorosilane (TCS).

In a preferred embodiment, in the process, a slag discharge port is designed at the bottom of the central cylinder of the fluidized bed heat exchanger, and the slag discharge operation is carried out periodically and quantitatively. If the vaporization amount of STC is 150t/h, trace metal impurities (B, P, Fe, Al, Ca and the like) contained in STC are continuously enriched, the estimation is carried out according to the trace impurities being 200PPb, 600-720 g of trace elements are enriched after the central cylinder STC of the 24h heat exchanger is vaporized, and if the enriched trace metal impurities are not discharged in time, a pipeline is blocked.

In still another preferred embodiment, the design of the outlet hot material flow tube pass coil of the fluidized bed heat exchanger can be carried out, and the flow velocity of the coil is designed to be 18-23 m/s. The curvature of the coil pipe enables the inertia force and the centrifugal force of fluid in the pipe to be unbalanced, secondary flow occurs on the cross section of the groove, turbulence is increased, heat transfer efficiency is improved, and meanwhile self-descaling capacity is improved.

Meanwhile, heat energy can be further recovered by setting the outlet temperature of the tube pass. The temperature of the tube pass inlet of the FBR heat exchanger is determined to be 540 ℃ from the main reaction temperature, the temperature of the tube pass outlet is determined from the physical property of an FBR outlet medium, the protection design of a common process kit is 180 ℃, and thus the heat exchanger can be designed to fully recover the heat energy of the FBR outlet heat stream in the range of 180-540 ℃. The design of the invention reduces the outlet temperature of the tube pass to 155 ℃, the heat exchanger can still keep normal and efficient operation, and the heat energy of the FBR outlet heat flow in the range of 155-540 ℃ can be completely recovered.

STC and H of the invention₂Directly enters into the FBR heat exchanger to avoid preheating gasification, thus reducing the processes of a preheater and a gasifier. The energy recovery amount of the FBR outlet hot material flow reaches 16086KW, the energy is saved by 1042KW compared with the original process before FBR reaction, and simultaneously the energy consumption is synchronously reduced by the condensing unit.

The invention provides a method and a thought for recovering heat energy of a chlorohydrination fluidized bed, and a method and a way for realizing the technical scheme are many, the above description is only a preferred embodiment of the invention, and it should be noted that, for a person skilled in the art, a plurality of improvements and decorations can be made without departing from the principle of the invention, and the improvements and decorations are also regarded as the protection scope of the invention. All the components not specified in the present embodiment can be realized by the prior art.