Energy-saving system and energy-saving method for aniline-pvc combination

Abstract

The present application provides aniline-PVC combined energy-saving system and energy-saving method. The energy-saving system comprises aniline unit and PVC unit; the aniline unit comprises a fluidized bed reactor, a first steam boiler, a second steam boiler, a hot water heat exchanger, a first water cooler, a gas-liquid separation tank, a hot water tank and an oxygen remover connected in sequence; the PVC unit comprises a PVC drying unit and an RVCM unit; in the PVC drying unit, a first steam heater and a first hot water heater are connected in parallel and connected in series with the drying fluidized bed respectively; and / or the RVCM unit comprises a second steam heater, an RVCM hot water user and a second hot water heater connected in series; the hot medium inlet of the first steam heater and / or the second hot water heater is connected to the hot water outlet of the hot water heat exchanger. The energy-saving system combines the aniline unit with the PVC unit, thereby improving the heat utilization rate of the aniline unit and realizing energy saving.

Description

Technical Field

[0001] This invention belongs to the field of chemical energy conservation, specifically relating to an energy-saving system and method combining aniline and PVC. Background Technology

[0002] Aniline is an important organic chemical raw material and a crucial intermediate in the synthetic rubber, organic pigment, coating, dye, and pesticide industries. Due to its wide range of applications, aniline has a very promising market potential. Currently, the main production processes for aniline include the nitrobenzene iron powder reduction method, the phenol amination method, and the nitrobenzene catalytic hydrogenation method, accounting for 5%, 10%, and 85% of the total aniline production capacity, respectively. Most companies use the nitrobenzene catalytic hydrogenation method to produce aniline. Industrially, three processes are employed: fixed-bed catalytic hydrogenation, fluidized-bed catalytic hydrogenation, and nitrobenzene liquid-phase hydrogenation. The catalysts used are copper-based, nickel-based, and precious metals such as palladium, and the catalyst supports include silica gel, zeolite, activated alumina, and diatomaceous earth. Currently, most domestic aniline production uses the fluidized-bed nitrobenzene catalytic hydrogenation process, which is a mature technology with significant technological advantages.

[0003] The catalytic hydrogenation of nitrobenzene is an exothermic reaction, as shown in the following equation:

[0004] C6H5NO2+3H2→C6H5NH2+2H2O+544kJ / mol

[0005] Since the hydrogenation of nitrobenzene is a strongly exothermic reaction, the azeotrope of aniline and water overflowing from the top of the reactor is generally at a temperature of around 200-230°C. Traditional processes typically require a four-stage condensation method to cool the high-temperature azeotrope to 40°C. In this method, most of the reaction heat is recovered through a medium-pressure steam generator and a low-pressure steam generator. However, the remaining heat is often further cooled by an air cooler and a first water cooler. This cooling process results in significant heat waste and consumes a large amount of circulating water, leading to energy waste.

[0006] CN 105418437 A discloses an energy-saving method for an aniline production unit. In this method, a portion of the gaseous material from the fluidized bed outlet of an existing gas-phase fluidized bed aniline production unit is passed through a hydrogen heat exchanger, then condensed in a condenser for gas-liquid separation. The separated hydrogen is reused, and the separated liquid material, aniline and water, is further cooled in a cooler for aniline and water separation. The other portion of the fluidized bed outlet material directly enters a tower-type direct heat exchanger, where it exchanges heat with aniline. While this process achieves energy savings to some extent, the heat utilization rate remains low, and it requires sophisticated equipment and significant modifications.

[0007] The PVC unit is used to produce PVC (polyvinyl chloride). It includes a VCM unit, a PVC drying unit, and an RVCM unit. The PVC drying unit has a closed water system for drying PVC, and the heat of the closed water system is supplied by steam. The RVCM unit also has a closed water system to provide heat to the reboilers of each distillation column, and the heat of the closed water system is also provided by steam, resulting in high energy consumption.

[0008] Conventional methods for aniline plants cannot efficiently utilize the heat carried by crude aniline at the top of a three-phase fluidized bed reactor. Furthermore, aniline plants and PVC plants belong to different fields, and there are currently no publicly available technologies that can combine aniline and PVC to achieve energy savings. Summary of the Invention

[0009] The first objective of this invention is to provide an energy-saving system combining aniline and PVC, which improves the heat utilization rate of the aniline unit and achieves energy saving by combining the aniline unit with the PVC unit.

[0010] The second objective of this invention is to provide an energy-saving method for aniline-PVC combination using the aforementioned energy-saving system. This energy-saving method enables the combined use of an aniline unit and a PVC unit, thereby improving the heat utilization rate of the aniline unit and achieving energy saving.

[0011] To achieve the first objective of this invention, the following technical solution is adopted:

[0012] An energy-saving system combining aniline and PVC, comprising an aniline unit and a PVC unit;

[0013] The aniline unit includes a fluidized bed reactor, a first steam boiler, a second steam boiler, a hot water heat exchanger, a first water cooler, a gas-liquid separator, a hot water tank, and a deaerator, all connected via material pipelines; wherein,

[0014] The fluidized bed reactor is used for the catalytic hydrogenation of nitrobenzene, and aniline is output from the top gas phase outlet.

[0015] The first steam boiler is connected to the top gas phase outlet of the fluidized bed reactor for generating S10 steam using heat from aniline in the fluidized bed reactor;

[0016] The second steam boiler is connected to the aniline outlet of the first steam boiler and is used to generate S4 steam by utilizing the waste heat from the aniline in the first steam boiler.

[0017] The aniline inlet of the hot water heat exchanger is connected to the aniline outlet of the second steam boiler, and the water inlet of the hot water heat exchanger is connected to the water outlet of the hot water tank. This is used to heat water from the hot water tank using the waste heat from the aniline in the second steam boiler as a heat medium to supply the PVC unit. The water inlet of the hot water tank is connected to the water outlet pipeline of the PVC unit to buffer the water coming out of the PVC unit.

[0018] The deaerator is connected to the inlet of the first steam boiler and the second steam boiler respectively, and is used to deaerate the input demineralized water and then deliver it as feed water to the first steam boiler and the second steam boiler respectively.

[0019] One end of the first water cooler is connected to the aniline outlet of the hot water heat exchanger, and the other end is connected to the gas-liquid separator, for further cooling of the aniline from the hot water heat exchanger before sending it to the gas-liquid separator for gas-liquid separation;

[0020] The PVC unit includes a PVC drying unit and an RVCM unit connected by material pipelines; wherein...

[0021] The PVC drying unit includes a first steam heater, a drying fluidized bed, and a first hot water heater connected by pipelines; wherein...

[0022] The first steam heater and the first hot water heater are connected in parallel and in series with the drying fluidized bed. The first steam heater is provided with a first steam feed line, and the heat medium inlet of the first hot water heater is connected to the hot water outlet of the hot water heat exchanger. The first steam heater and the first hot water heater are used to heat the effluent from the drying fluidized bed using the introduced steam and the effluent from the aniline unit, respectively, and then circulate it to the drying fluidized bed to dry the PVC inside; and / or

[0023] The RVCM unit includes a second steam heater, an RVCM hot water user, and a second hot water heater connected in series via pipelines; wherein...

[0024] The heat medium inlet of the second hot water heater is connected to the hot water outlet of the hot water heat exchanger. The second steam heater is provided with a second steam feed pipeline. The second hot water heater uses the water from the aniline unit to preheat the water from the RVCM hot water user and then circulates it to the second steam heater. The second steam heater uses the introduced steam to further heat the water preheated by the second hot water heater and then circulates it to the RVCM hot water user.

[0025] Preferably, a first valve is provided on the first steam feed pipeline, and a first temperature indication and control device is provided on the water inlet pipeline of the drying fluidized bed. The first temperature indication and control device is electrically connected to the first valve and is used to indicate the material temperature in the water inlet pipeline of the drying fluidized bed, and to control the opening degree of the first valve according to the aforementioned temperature indication.

[0026] Preferably, the PVC unit further includes a hot water recovery pipeline, one end of which is connected to the hot water outlet of the hot water heat exchanger, and the other end of which is connected to the outlet pipeline of the PVC unit, for returning excess hot water to the aniline unit; and / or

[0027] The aniline unit further includes a second water cooler, the inlet of which is connected to the outlet pipe of the PVC unit and the outlet of which is connected to the hot water tank, for cooling the water from the PVC unit to supply the hot water tank.

[0028] Preferably, a third valve is provided on the heat medium inlet pipeline of the first hot water heater; and / or

[0029] A fourth valve is installed on the heat medium inlet pipeline of the second hot water heater; and / or

[0030] A fifth valve is installed on the hot water recovery pipeline.

[0031] Preferably, a second valve is provided on the second steam feed pipeline, and a second temperature indication and control device is provided on the outlet water pipeline of the second steam heater. The second temperature indication and control device is electrically connected to the second valve and / or the fourth valve, and is used to indicate the material temperature in the outlet water pipeline of the second steam heater, and to control the opening degree of the second valve and / or the fourth valve according to the aforementioned temperature indication.

[0032] Preferably, a sixth valve is provided on the water inlet pipeline of the first water cooler, and a third temperature indication and control device is provided on the aniline pipeline from the first water cooler to the gas-liquid separator. The third temperature indication and control device is electrically connected to the sixth valve and is used to indicate the material temperature in the aniline pipeline and control the opening degree of the sixth valve according to the aforementioned temperature indication.

[0033] Preferably, the second water cooler is provided with a cold medium inlet pipeline for feeding cold medium to cool the effluent from the PVC unit; a seventh valve is provided on the cold medium inlet pipeline, and a fourth temperature indication and control device is provided on the water supply pipeline from the PVC unit outlet to the second water cooler inlet, and the fourth temperature indication and control device is electrically connected to the seventh valve for indicating the material temperature in the water supply pipeline and controlling the opening degree of the seventh valve according to the aforementioned temperature indication.

[0034] To achieve the second objective of this invention, an energy-saving method for aniline-PVC co-processing using the aforementioned energy-saving system is provided, comprising:

[0035] (1) The aniline output from the fluidized bed reactor in the aniline unit is sequentially passed through the first steam boiler, the second steam boiler and the hot water heat exchanger for energy utilization, and S10 steam, S4 steam and hot water for the PVC unit are generated sequentially and then cooled.

[0036] (2) Hot water from the hot water heat exchanger in the aniline unit is input into the PVC unit and used as the heat medium for the first hot water heater in the PVC drying unit. The first steam heater and the first hot water heater respectively use the introduced steam and the hot water from the hot water heat exchanger to heat the effluent from the drying fluidized bed and then circulate it to the drying fluidized bed to dry the PVC inside; and / or

[0037] Hot water from the hot water heat exchanger in the aniline unit is input into the PVC unit and used as the heat medium for the second hot water heater in the RVCM unit to preheat the water from the RVCM hot water user before circulating it to the second steam heater. The second steam heater uses the introduced steam to further heat the water preheated by the second hot water heater before circulating it to the RVCM hot water user.

[0038] Preferably, the energy-saving method further includes:

[0039] The temperature of the material in the inlet pipeline of the drying fluidized bed is indicated by the first temperature indication control device, and the opening degree of the first valve is controlled according to the aforementioned temperature indication.

[0040] Preferably, the energy-saving method further includes:

[0041] Excess hot water from the hot water heat exchanger is returned to the aniline unit via the hot water recovery pipeline for the purpose of recovering excess hot water.

[0042] Preferably, the energy-saving method further includes:

[0043] The second temperature indicator control device is used to indicate the material temperature in the outlet water pipeline of the second steam heater, and the opening degree of the second valve and / or the fourth valve is controlled according to the aforementioned temperature indication.

[0044] Preferably, the energy-saving method further includes:

[0045] The third temperature indicator control device is used to indicate the material temperature in the aniline pipeline, and the opening degree of the sixth valve is controlled according to the aforementioned temperature indication.

[0046] Preferably, the energy-saving method further includes:

[0047] The fourth temperature indicator control device is used to indicate the temperature of the material in the water pipeline, and the opening degree of the seventh valve is controlled according to the aforementioned temperature indication.

[0048] The beneficial effects of this invention are as follows:

[0049] (1) Conventional methods are difficult to efficiently utilize the energy in the aniline material at the top of the fluidized bed reactor in the aniline unit. This invention utilizes the waste heat from the first and second steam boilers to produce high-temperature hot water for the PVC unit, thereby maximizing the heat utilization rate of the aniline unit and saving the circulating water consumption of the aniline unit and the steam consumption of the PVC unit. The two units achieve a win-win effect. Using the energy-saving system and energy-saving method of this invention, the 180,000 tons / year aniline unit can recover 11.7-14.2 MW of heat, and the PVC unit can save 16.38-19.88 tons / hour of S10 steam.

[0050] (2) The aniline energy utilization rate in this invention is high. By linking with the heat consumption of the PVC unit, the energy consumption of both devices can be reduced. The aniline energy utilization rate is at an advanced level in the industry.

[0051] (3) This invention controls the material feed rate and feed speed in the corresponding feed pipeline by displaying the temperature of the material in the corresponding pipeline and controlling the opening of the valves on the corresponding feed pipeline according to the temperature display, thereby adjusting the temperature of the material in the corresponding pipeline, ensuring the stable operation of the energy-saving system, and will not have a negative impact on the normal operation of the two unit devices.

[0052] (4) By using heat in multiple directions at the heat-using end, the present invention can maximize the recovery and utilization of heat;

[0053] (5) This invention makes full use of the latent heat and sensible heat of crude aniline, and uses demineralized water and hot water as a medium to improve the heat utilization rate of the aniline unit and reduce the steam consumption of the PVC unit; through equipment buffering and regulation, the stability of the energy-saving system is ensured, and the purpose of heat recovery and energy consumption reduction is achieved, which has good economic benefits. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the structure of the aniline-PVC combined energy-saving system of the present invention in one embodiment;

[0055] Figure 2 This is the process flow diagram for Comparative Example 1;

[0056] Among them, PW water is demineralized water, S4 is S4 steam, S4C is S4 steam condensate, and S10 is S10 steam. Detailed Implementation

[0057] The technical solution and its effects of the present invention will be further described below with reference to specific embodiments / examples. The following embodiments / examples are only for illustrating the content of the present invention, and the invention is not limited to the following embodiments or examples. Simple modifications made to the present invention based on the concept of the present invention are all within the scope of protection claimed by the present invention.

[0058] like Figure 1 As shown, an energy-saving system combining aniline and PVC includes an aniline unit 1 and a PVC unit 2.

[0059] The aniline unit 1 includes a fluidized bed reactor 101, a first steam boiler 102, a second steam boiler 103, a hot water heat exchanger 104, a first water cooler 105, a gas-liquid separator 106, a hot water tank 107, and a deaerator 109, all connected by material pipelines.

[0060] The fluidized bed reactor 101 is used to carry out the catalytic hydrogenation reaction of nitrobenzene, and aniline is output from the top gas phase outlet;

[0061] The first steam boiler 102 is connected to the top gas phase outlet of the fluidized bed reactor 101 for generating S10 steam using heat from aniline in the fluidized bed reactor 101;

[0062] The second steam boiler 103 is connected to the aniline outlet of the first steam boiler 102 and is used to generate S4 steam by utilizing the waste heat from the aniline in the first steam boiler 102.

[0063] The aniline inlet of the hot water heat exchanger 104 is connected to the aniline outlet of the second steam boiler 103, and the water inlet of the hot water heat exchanger 104 is connected to the water outlet of the hot water tank 107, for using the waste heat from the aniline in the second steam boiler 103 to heat the water from the hot water tank 107 as a heat medium to supply the PVC unit 2; the water inlet of the hot water tank 107 is connected to the water outlet pipeline of the PVC unit 2, for buffering the water outlet from the PVC unit 2;

[0064] The deaerator 109 is connected to the inlet of the first steam boiler 102 and the second steam boiler 103 respectively, and is used to deaerate the input demineralized water and then deliver it as feed water to the first steam boiler 102 and the second steam boiler 103 respectively.

[0065] One end of the first water cooler 105 is connected to the aniline outlet of the hot water heat exchanger 104, and the other end is connected to the gas-liquid separator 106, for further cooling of the aniline from the hot water heat exchanger 104 before sending it to the gas-liquid separator 106 for gas-liquid separation.

[0066] The PVC unit 2 includes a PVC drying unit 21 and an RVCM unit 22 connected by a material pipeline; wherein,

[0067] The PVC drying unit 21 includes a first steam heater 211, a drying fluidized bed 212, and a first hot water heater 213 connected by pipelines; wherein...

[0068] The first steam heater 211 and the first hot water heater 213 are connected in parallel and in series with the drying fluidized bed 212. The first steam heater 211 is provided with a first steam feed line 214, and the heat medium inlet of the first hot water heater 213 is connected to the hot water outlet of the hot water heat exchanger 104. The first steam heater 211 and the first hot water heater 213 are used to heat the effluent from the drying fluidized bed 212 with the incoming steam and the effluent from the aniline unit 1, respectively, and then circulate it to the drying fluidized bed 212 to dry the PVC inside; and / or

[0069] The RVCM unit 22 includes a second steam heater 221, an RVCM hot water user 222, and a second hot water heater 223 connected in series via pipelines; wherein...

[0070] The heat medium inlet of the second hot water heater 223 is connected to the hot water outlet of the hot water heat exchanger 104. The second steam heater 221 is provided with a second steam feed line 224. The second hot water heater 223 uses the water from the aniline unit 1 to preheat the water from the RVCM hot water user 222 and then circulates it to the second steam heater 221. The second steam heater 221 uses the introduced steam to further heat the water preheated by the second hot water heater 223 and then circulates it to the RVCM hot water user 222.

[0071] The energy-saving system of this invention solves the problem of inefficiently utilizing the energy in the aniline material at the top of the fluidized bed reactor in an aniline unit by combining the aniline unit and the PVC unit. By adding a hot water heat exchanger 104 and a hot water tank 107 to the aniline unit, the heat from the aniline at the top of the fluidized bed reactor in the aniline unit is used to generate steam for the first and second steam boilers. Simultaneously, the residual heat is used to generate high-temperature hot water for the PVC unit, reducing the steam input to the PVC unit and saving energy, thereby maximizing the heat utilization rate of the aniline unit 1. Furthermore, the effluent from the PVC unit 2 is buffered in the hot water tank 107 and then further heated in the hot water heat exchanger 104, forming a hot water circulation, which reduces the steam consumption of the PVC unit 2 and the water consumption of the energy-saving system. In this invention, the first steam boiler 102 and the second steam boiler 103 are connected in series, and the steam production flow rate can be controlled by controlling the boiler inlet water flow rate.

[0072] Those skilled in the art will understand that the first steam boiler 102 and the second steam boiler 103 are commonly used boilers in the art. In one embodiment, the first steam boiler 102 and the second steam boiler 103 are of the BKU type, preferably retaining a large gas phase space.

[0073] In one embodiment, the outlet water temperature of the hot water heat exchanger 104 is 110-120℃, such as 111℃, 112℃, 113℃, 114℃, 115℃, 116℃, 117℃, 118℃ and 119℃.

[0074] In one embodiment, the inlet water temperature of the hot water heat exchanger 104 is 60-70°C, such as 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, and 69°C.

[0075] In one embodiment, the outlet water temperature of the hot water tank 107 is 60-70°C, such as 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, and 69°C.

[0076] In one embodiment, the hot water tank 107 has a buffer time of 0.5-2 hours for incoming water, such as 1 hour and 1.5 hours.

[0077] In one embodiment, the temperature of the demineralized water from the demineralized water tank 202 in the demineralized water heat exchanger 201 is 40-50°C, such as 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, and 49°C.

[0078] In one embodiment, the circulating water from the RVCM hot water user 222 is preheated by the second hot water heater 223 to a temperature of 80-100℃, such as 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃, 90℃, 91℃, 92℃, 93℃, 94℃, 95℃, 96℃, 97℃, 98℃, and 99℃.

[0079] In one embodiment, a first valve 215 is provided on the first steam feed line 214, and a first temperature indication and control device 217 is provided on the water inlet line of the drying fluidized bed 212. The first temperature indication and control device 217 is electrically connected to the first valve 215 and is used to indicate the material temperature in the water inlet line of the drying fluidized bed 212. The opening degree of the first valve 215 is controlled according to the aforementioned temperature indication, thereby controlling the amount of steam used. When the material temperature in the water inlet line of the drying fluidized bed 212 is high or low, the amount of steam used is reduced or increased accordingly.

[0080] In one embodiment, the PVC unit 2 further includes a hot water recovery pipeline 23, one end of which is connected to the hot water outlet of the hot water heat exchanger 104, and the other end is connected to the outlet pipeline of the PVC unit 2, for returning excess hot water to the aniline unit 1, thus preventing the direct discharge of excess hot water from the hot water heat exchanger 104 after supplying the PVC drying unit 21 and / or the RVCM unit 22, which would otherwise result in heat waste; and / or

[0081] The aniline unit 1 further includes a second water cooler 108, the inlet of which is connected to the outlet of the PVC unit 2 and the outlet is connected to the hot water tank 107, for cooling the water from the PVC unit 2 to supply the hot water tank 107.

[0082] Those skilled in the art will understand that if the outlet water temperature of the PVC drying unit 21 and / or the RVCM unit 22 is high, or if there is excess hot water produced by the hot water heat exchanger 104 in the aniline unit and there is a surplus after applying it to the PVC unit 2, the outlet water of the PVC drying unit 21 and / or the RVCM unit 22, or the excess hot water from the hot water heat exchanger 104, can be first sent to the second water cooler 108 of the aniline unit for cooling, then sent to the hot water tank 107 for buffering, and then sent to the hot water heat exchanger 104 for heating. This allows the excess energy to be utilized, stored, or consumed through the second water cooler 108 before entering the hot water heat exchanger 104 for heating to supply the PVC unit 2, thus avoiding fluctuations and impacts on the energy-saving system, especially the PVC unit 2, caused by the excess heat.

[0083] In one embodiment, a third valve 219 is provided on the heat medium inlet pipeline of the first hot water heater 213 for controlling the input of hot water from the hot water heat exchanger 104 as the heat medium to the PVC drying unit 21 and the input amount thereon; and / or

[0084] A fourth valve 229 is installed on the heat medium inlet pipeline of the second hot water heater 223 to control the input of hot water from the hot water heat exchanger 104 as the heat medium to the RVCM unit 22 and the input amount; and / or

[0085] A fifth valve 231 is installed on the hot water recovery pipeline 23 to control whether the hot water from the hot water heat exchanger 104 is returned to the aniline unit 1 and the amount of return.

[0086] In one embodiment, a second valve 225 is provided on the second steam feed line 224, and a second temperature indication and control device 227 is provided on the outlet line of the second steam heater 221. The second temperature indication and control device 227 is electrically connected to the second valve 225 and / or the fourth valve 229, and is used to indicate the material temperature in the outlet line of the second steam heater 221, and control the opening degree of the second valve 225 and / or the fourth valve 229 according to the aforementioned temperature indication, thereby adjusting and controlling the material temperature in the outlet line of the second steam heater 221.

[0087] In one embodiment, a sixth valve 110 is provided on the water inlet pipeline of the first water cooler 105, and a third temperature indicating and controlling device 112 is provided on the aniline pipeline 111 from the first water cooler 105 to the gas-liquid separator 106. The third temperature indicating and controlling device 112 is electrically connected to the sixth valve 110 and is used to indicate the material temperature in the aniline pipeline 111. The opening degree of the sixth valve 110 is controlled according to the aforementioned temperature indication, thereby controlling the amount of water flowing into the first water cooler 105 as the cooling medium, and thus adjusting and controlling the material temperature in the aniline pipeline 111, that is, the temperature of the cooled aniline.

[0088] In one embodiment, the second water cooler 108 is provided with a cold medium inlet pipeline 113 for feeding cold medium to cool the water outlet from the PVC unit 2; a seventh valve 114 is provided on the cold medium inlet pipeline 113; a fourth temperature indication and control device 116 is provided on the water supply pipeline 115 from the water outlet of the PVC unit 2 to the water inlet of the second water cooler 108, and the fourth temperature indication and control device 116 is electrically connected to the seventh valve 114 for indicating the material temperature in the water supply pipeline 115, and controlling the opening degree of the seventh valve 114 according to the aforementioned temperature indication, thereby controlling the flow rate of cold medium in the second water cooler 108, and thus adjusting and controlling the inlet water temperature of the hot water tank 107.

[0089] The aniline-PVC combined energy-saving system of the present invention uses the residual heat after the aniline in the aniline unit generates steam to produce high-temperature hot water for the PVC unit, thereby saving the circulating water consumption of the aniline unit and the steam consumption of the PVC unit. The two devices achieve a win-win effect. Through a series of control measures, the aniline-PVC combined energy saving can be safely achieved, effectively reducing the operating costs of the two devices.

[0090] The present invention also provides an energy-saving method for aniline-PVC co-processing using the aforementioned energy-saving system, comprising:

[0091] (1) The aniline output from the fluidized bed reactor 101 in the aniline unit 1 is sequentially passed through the first steam boiler 102, the second steam boiler 103 and the hot water heat exchanger 104 for energy utilization, and S10 steam, S4 steam and hot water for the PVC unit 2 are generated sequentially and then cooled.

[0092] (2) Hot water from the hot water heat exchanger 104 in the aniline unit 1 is input into the PVC unit 2 and used as the heat medium for the first hot water heater 213 in the PVC drying unit 21. The first steam heater 211 and the first hot water heater 213 respectively use the introduced steam and the hot water from the hot water heat exchanger 104 to heat the effluent from the drying fluidized bed 212 and then circulate it to the drying fluidized bed 212 to dry the PVC inside; and / or

[0093] Hot water from the hot water heat exchanger 104 in the aniline unit 1 is input into the PVC unit 2 and used as the heat medium of the second hot water heater 223 in the RVCM unit 22 to preheat the water from the RVCM hot water user 222 before circulating it to the second steam heater 221. The second steam heater 221 uses the introduced steam to further heat the water preheated by the second hot water heater 223 before circulating it to the RVCM hot water user 222.

[0094] In one embodiment, the energy-saving method further includes:

[0095] The first temperature indication control device 217 indicates the material temperature in the water inlet pipeline of the drying fluidized bed 212, and controls the opening of the first valve 215 according to the aforementioned temperature indication, thereby controlling the amount of steam introduced as the heat medium, and thus adjusting and controlling the material temperature in the water inlet pipeline of the drying fluidized bed 212.

[0096] In one embodiment, the energy-saving method further includes:

[0097] Excess hot water from the hot water heat exchanger 104 is returned to the aniline unit 1 via the hot water recovery pipeline 23 for the purpose of recovering excess hot water.

[0098] In one embodiment, the energy-saving method further includes:

[0099] The second temperature indicator control device 227 indicates the material temperature in the outlet water line of the second steam heater 221, and controls the opening of the second valve 225 and / or the fourth valve 229 according to the aforementioned temperature indication, thereby controlling the flow rate of steam and / or hot water from the hot water heat exchanger 104 as the heat medium, and thus controlling and adjusting the material temperature in the outlet water line of the second steam heater 221.

[0100] In one embodiment, the energy-saving method further includes:

[0101] The third temperature indicator control device 112 indicates the material temperature in the aniline pipeline 111, and controls the opening of the sixth valve 110 according to the aforementioned temperature indication, thereby controlling the flow rate of water as the cooling medium in the first water cooler 105, and thus adjusting and controlling the material temperature in the aniline pipeline 111, i.e. the aniline temperature after cooling.

[0102] In one embodiment, the energy-saving method further includes:

[0103] The fourth temperature indicator control device 116 indicates the material temperature in the water supply pipeline 115, and controls the opening of the seventh valve 114 according to the aforementioned temperature indication, thereby controlling the flow rate of the cooling medium in the second water cooler 108, and thus adjusting and controlling the inlet water temperature of the hot water tank 107.

[0104] The energy-saving method of aniline-PVC combination of the present invention saves the circulating water consumption of the aniline unit and the steam consumption of the PVC unit by using the residual heat after the aniline in the aniline unit steams. The two devices achieve a win-win effect. Through a series of control measures, the energy saving of aniline-PVC combination can be safely achieved, effectively reducing the operating costs of the two devices. The two units achieve a win-win effect.

[0105] The methods for measuring / calculating the relevant parameters in the following embodiments and comparative examples of the present invention are as follows:

[0106] Aniline heat utilization rate (%) = (Total heat of aniline at the top of the tower - Heat removed by water cooling - Heat removed by air cooling) / Total heat of aniline at the top of the tower * 100%;

[0107] Recovered heat (MW) = (Original steam consumption - Current steam consumption) * Available calorific value of steam / 1000 = Steam saved by PVC unit * Available calorific value of steam / 1000; where the units of original steam consumption, current steam consumption and steam saved by PVC unit are t / h, and the available calorific value of steam = 714kw / t;

[0108] Revenue (RMB 10,000 / year) = [(Aniline by-product S10 * S10 unit price) + (Aniline by-product S4 * S4 unit price) + (PVC unit steam savings * S10 unit price)] * Annual operating time / 10000; where the unit price of S10 steam is calculated at RMB 210 / t, the unit price of S4 steam at RMB 145 / t, the electricity price at RMB 0.65 / kWh, the unit price of thermal power steam at RMB 210 / t, and the annual operating time at 8000h. The unit price of S10 is calculated at RMB 210 / ton; the unit price of S4 at RMB 150 / ton; the electricity price at RMB 0.6 / kWh; and the annual operating time at 8000h.

[0109] Example 1 (S1)

[0110] Utilize Figure 1 The energy-saving system shown is an energy-saving method for the combined use of aniline and PVC; wherein, the aniline unit 1 is an aniline unit with a load of 180,000 tons / year, and the PVC unit 2 is a PVC unit with a load of 400,000 tons / year (operating at 100% load);

[0111] Energy-saving methods include:

[0112] The aniline (220°C) at the top of the fluidized bed reactor 101 in the aniline unit 1 is sequentially fed into the first steam boiler 102 and the second steam boiler 103 for energy utilization to generate S10 steam and S4 steam.

[0113] Aniline (132°C) from the second steam boiler 103 is introduced into the hot water heat exchanger 104 to produce hot water at 120°C using residual heat, and the produced hot water is divided into two streams and supplied to PVC unit 2 respectively.

[0114] One stream of hot water is input into the PVC unit 2 and used as the heat medium for the first hot water heater 213 in the PVC drying unit 21 to provide heat to its internal closed water system. The first steam heater 211 and the first hot water heater 213 respectively use the incoming hot steam and water from the hot water heat exchanger 104 to heat the water from the drying fluidized bed 212 and then circulate it to the drying fluidized bed 212 to dry the PVC inside. During this period, the material temperature in the water inlet pipeline of the drying fluidized bed 212 is indicated by the first temperature indication control device 217, and the opening degree of the first valve 215 is controlled according to the aforementioned temperature indication.

[0115] Another stream of hot water is input into the PVC unit 2 and used as the heat medium for the second hot water heater 223 in the RVCM unit 22 to provide heat to its internal closed water system. After preheating the water from the RVCM hot water user 222, it is circulated to the second steam heater 221. The second steam heater 221 uses the introduced steam to further heat the water preheated by the second hot water heater 223 and then circulates it to the RVCM hot water user 222. During this period, the material temperature in the outlet pipeline of the second steam heater 221 is indicated by the second temperature indication control device 227, and the opening degree of the second valve 225 and / or the fourth valve 229 is controlled according to the aforementioned temperature indication.

[0116] The effluent (70°C) from PVC unit 2 is fed into aniline unit 1, cooled to 60°C by the second water cooler 108, and then transported to the hot water tank 107 to reduce the impact of hot water flow fluctuations on the system. It is then sent to the hot water heat exchanger 104 to utilize the residual heat from the aniline (132°C) from the second steam boiler 103 to heat the water, forming a hot water circulation. During this process, the temperature of the material in the water pipeline 115 is indicated by the fourth temperature indication and control device 116, and the opening of the seventh valve 114 is controlled according to the aforementioned temperature indication.

[0117] The aniline (70°C) cooled by the hot water heat exchanger 104 is passed into the first water cooler 105 to be cooled to below 40°C, and then sent to the gas-liquid separator 106 for gas-liquid separation to reuse hydrogen. During this process, the material temperature in the aniline pipeline 111 is indicated by the third temperature indication and control device 112, and the opening degree of the sixth valve 110 is controlled according to the aforementioned temperature indication.

[0118] Example 2 (S2)

[0119] The only difference from Example 1 is the following:

[0120] The PVC unit in PVC cell 2 is operating at 120% load.

[0121] The effluent from the PVC unit 2 to the aniline unit 1 is 61°C.

[0122] Comparative Example 1 (D1)

[0123] Utilize Figure 2 The system shown is designed for energy conservation; wherein, the system is a 180,000-ton / year aniline unit;

[0124] Energy-saving methods include:

[0125] The deoxygenated water is fed into the deaerator 108' for deoxygenation and then supplied to the first steam boiler 102' and the second steam boiler 103'.

[0126] Aniline (214°C) at the top of the fluidized bed reactor 101' is sequentially fed into the first steam boiler 102' and the second steam boiler 103' for energy utilization to generate S10 steam and S4 steam;

[0127] Aniline (159°C) from the second steam boiler 103' is introduced into the air cooler 110' for cooling;

[0128] Aniline (60°C) from the air cooler 110' is fed into the first water cooler 105' to be cooled to 40°C, and then sent to the gas-liquid separator 106' for gas-liquid separation to reuse hydrogen.

[0129] The relevant parameters of Example 1 and Comparative Example 1 were measured, and the results are shown in Table 1.

[0130] Table 1. Measurement results of Example 1 and Comparative Example 1

[0131]

[0132]

[0133] According to Examples 1-2, Comparative Example 1, and Table 1:

[0134] In Examples 1-2 of this invention, the heat utilization rate of aniline is as high as 90% and 93%, respectively, while in Comparative Example 1, the heat utilization rate of aniline is only 75%.

[0135] Compared to Comparative Example 1, Embodiments 1-2 of the present invention both reduced air-cooled power consumption by 176kW, and the PVC units saved steam by 16.38t / h and 19.88t / h, respectively;

[0136] The revenue of Example 1 of this invention is RMB 79.2 million per year, and the revenue of Example 2 is RMB 82.8 million per year, which is RMB 20.05 million per year and RMB 23.65 million per year higher than that of Comparative Example 1, respectively, demonstrating significant energy-saving effects and economic benefits.

Claims

1. A combined energy saving system for aniline-PVC, characterized in that, The energy-saving system comprises an aniline unit (1) and a PVC unit (2); The aniline unit (1) comprises a fluidized bed reactor (101), a first steam boiler (102), a second steam boiler (103), a hot water heat exchanger (104), a first water cooler (105), a gas-liquid separation tank (106), a hot water tank (107) and a deaerator (109) connected by material pipelines; wherein, The fluidized bed reactor (101) is used for catalytic hydrogenation reaction of nitrobenzene, and aniline is output from the top gas phase outlet; The first steam boiler (102) is connected to the top gas phase outlet of the fluidized bed reactor (101) and is used for generating S10 steam by using the heat in the aniline from the fluidized bed reactor (101); The second steam boiler (103) is connected to the aniline outlet of the first steam boiler (102) and is used for generating S4 steam by using the waste heat in the aniline from the first steam boiler (102); The aniline inlet of the hot water heat exchanger (104) is connected to the aniline outlet of the second steam boiler (103), the water inlet of the hot water heat exchanger (104) is connected to the water outlet of the hot water tank (107), and the water from the hot water tank (107) is heated by using the waste heat in the aniline from the second steam boiler (103) to supply the PVC unit (2) as a heat medium; the water inlet end of the hot water tank (107) is connected to the water outlet pipeline of the PVC unit (2) for buffering the water outlet from the PVC unit (2); The deaerator (109) is connected to the water inlets of the first steam boiler (102) and the second steam boiler (103) respectively, and after deaerating the input desalted water, the deaerated water is delivered into the first steam boiler (102) and the second steam boiler (103) respectively as the water inlet; One end of the first water cooler (105) is connected to the aniline outlet of the hot water heat exchanger (104), and the other end is connected to the gas-liquid separation tank (106), and the aniline from the hot water heat exchanger (104) is further cooled and then sent to the gas-liquid separation tank (106) for gas-liquid separation; The PVC unit (2) comprises a PVC drying unit (21) and an RVCM unit (22) connected by material pipelines; wherein, The PVC drying unit (21) comprises a first steam heater (211), a drying fluidized bed (212) and a first hot water heater (213) connected by pipelines; wherein, The RVCM unit (22) comprises a second hot water heater (221), a second steam heater (222), a RVCM reactor (223) and a second water cooler (224) connected by pipelines; wherein, The first steam heater (211) and the first hot water heater (213) are connected in parallel and are connected in series with the dry fluidized bed (212) respectively, and the first steam heater (211) is provided with a first steam feeding pipeline (214), a hot medium inlet of the first hot water heater (213) is connected to a hot water outlet of the hot water heat exchanger (104), the first steam heater (211) and the first hot water heater (213) are used for heating water from the dry fluidized bed (212) respectively by using the steam and the water from the aniline unit (1) and then recycling the water to the dry fluidized bed (212) to dry the PVC in the dry fluidized bed (212); and / or The RVCM unit (22) comprises a second steam heater (221), an RVCM hot water user (222) and a second hot water heater (223) connected in series by pipelines; wherein, A hot medium inlet of the second hot water heater (223) is connected to a hot water outlet of the hot water heat exchanger (104), the second steam heater (221) is provided with a second steam feeding pipeline (224), the second hot water heater (223) is used for preheating water from the RVCM hot water user (222) by using the water from the aniline unit (1) and then recycling the water to the second steam heater (221), the second steam heater (221) is used for further heating the water preheated by the second hot water heater (223) by using the steam and then recycling the water to the RVCM hot water user (222).

2. The energy saving system of claim 1, wherein, A first valve (215) is arranged on the first steam feeding pipeline (214), a first temperature indicating control device (217) is arranged on a water feeding pipeline of the dry fluidized bed (212), and the first temperature indicating control device (217) is electrically connected with the first valve (215) to indicate the temperature of the material in the water feeding pipeline of the dry fluidized bed (212) and control the opening degree of the first valve (215) according to the temperature indication.

3. The energy saving system according to claim 1 or 2, characterized in that, The PVC unit (2) further comprises a hot water recovery pipeline (23) having one end connected to a hot water outlet of the hot water heat exchanger (104) and the other end connected to a water outlet pipeline of the PVC unit (2) to return the excess hot water to the aniline unit (1); and / or The aniline unit (1) further comprises a second water cooler (108) having a water inlet end connected to a water outlet pipeline of the PVC unit (2) and a water outlet end connected to the hot water tank (107) to cool the water from the PVC unit (2) and then supply the water to the hot water tank (107).

4. The energy saving system of claim 3, wherein, A third valve (219) is arranged on a hot medium inlet pipeline of the first hot water heater (213); and / or A fourth valve (229) is arranged on a hot medium inlet pipeline of the second hot water heater (223); and / or A fifth valve (231) is arranged on the hot water recovery pipeline (23).

5. The energy saving system of claim 4, wherein, The second steam feeding pipeline (224) is provided with a second valve (225), the water outlet pipeline of the second steam heater (221) is provided with a second temperature indicating control device (227), and the second temperature indicating control device (227) is electrically connected with the second valve (225) and / or the fourth valve (229) to indicate the material temperature in the water outlet pipeline of the second steam heater (221) and control the opening degree of the second valve (225) and / or the fourth valve (229) according to the temperature indication.

6. The energy saving system according to any one of claims 1-2 and 4-5, characterized in that, The water inlet pipeline of the first water cooler (105) is provided with a sixth valve (110), the aniline pipeline (111) from the first water cooler (105) to the gas-liquid separation tank (106) is provided with a third temperature indicating control device (112), and the third temperature indicating control device (112) is electrically connected with the sixth valve (110) to indicate the material temperature in the aniline pipeline (111) and control the opening degree of the sixth valve (110) according to the temperature indication.

7. The energy saving system of claim 6, wherein, The second water cooler (108) is provided with a cold medium feeding pipeline (113) for feeding cold medium to cool the water outlet from the PVC unit (2); the cold medium feeding pipeline (113) is provided with a seventh valve (114), and the water conveying pipeline (115) from the water outlet end of the PVC unit (2) to the water inlet end of the second water cooler (108) is provided with a fourth temperature indicating control device (116), and the fourth temperature indicating control device (116) is electrically connected with the seventh valve (114) to indicate the material temperature in the water conveying pipeline (115) and control the opening degree of the seventh valve (114) according to the temperature indication.

8. An energy saving method for aniline-PVC combination using the energy saving system according to any one of claims 1-7, characterized in that, The energy-saving method comprises: (1) the aniline output from the fluidized bed reactor (101) in the aniline unit (1) is sequentially subjected to energy utilization by the first steam boiler (102), the second steam boiler (103) and the hot water heat exchanger (104) to sequentially generate S10 steam, S4 steam and hot water for post-cooling of the PVC unit (2); (2) the hot water from the hot water heat exchanger (104) in the aniline unit (1) is input into the PVC unit (2) to be used as the heat medium of the first hot water heater (213) in the PVC drying unit (21), the first steam heater (211) and the first hot water heater (213) respectively utilize the input steam and the hot water from the hot water heat exchanger (104) to heat the water outlet from the drying fluidized bed (212) and then recycle the heated water to the drying fluidized bed (212) to dry the PVC therein; and / or The hot water from the hot water heat exchanger (104) in the aniline unit (1) is input into the PVC unit (2) and used as the heat medium of the second hot water heater (223) in the RVCM unit (22) to preheat the outlet water from the RVCM hot water user (222) and then recycle the preheated water to the second steam heater (221), which further heats the water with the steam input and then recycles the heated water to the RVCM hot water user (222).

9. The energy saving method according to claim 8, wherein, The energy saving method further comprises: The first temperature indicating control device (217) is used to indicate the material temperature in the water inlet pipeline of the dry fluidized bed (212) and control the opening of the first valve (215) according to the temperature indication.

10. The energy saving method of claim 9, wherein, The energy saving method further comprises: The excess hot water from the hot water heat exchanger (104) is returned to the aniline unit (1) through the hot water recovery pipeline (23) to recover the excess hot water.

11. The energy saving method according to claim 10, wherein, The energy saving method further comprises: The second temperature indicating control device (227) is used to indicate the material temperature in the water outlet pipeline of the second steam heater (221) and control the opening of the second valve (225) and / or the fourth valve (229) according to the temperature indication.

12. The energy saving method according to any one of claims 8-11, wherein, The energy saving method further comprises: The third temperature indicating control device (112) is used to indicate the material temperature in the aniline pipeline (111) and control the opening of the sixth valve (110) according to the temperature indication.

13. The energy saving method of claim 12, wherein, The energy saving method further comprises: The fourth temperature indicating control device (116) is used to indicate the material temperature in the water supply pipeline (115) and control the opening of the seventh valve (114) according to the temperature indication.

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