Method for recovering process condensate generated in ethylbenzene dehydrogenation process of styrene device

Abstract

The invention relates to the technical field of industrial condensed water recycling and reusing, and discloses a method for recycling process condensate generated in the ethylbenzene dehydrogenation process of a styrene device. And the process condensate sequentially enters the heat exchanger, the composite fiber filter, the ultramicro iron removal filter, the polymer separation membrane filter, the anion bed, the mixed bed and the desalting water tank for desalting and then is recycled. According to the invention, process condensate of a styrene device can be treated and recovered, TOC, colloid and iron in water can be removed, and cations and anions (SO4 < 2->, NO3 <->, Cl <->, HSiO3 <-> and HCO3 <->) in water can be removed through the anion bed and the mixed bed, so that the water reaches the boiler desalted water (high-quality) water quality standard, the load of chemical water treatment equipment is reduced, the economic benefit of enterprises is improved, and the economic benefit of the enterprises is increased. And meanwhile, potential safety hazards brought to a production device when the circulating water is used for supplementing water are eliminated.

Description

Technical Field

[0001] The invention relates to the technical field of industrial condensate recovery and reuse, and in particular to a method for recovering process condensate generated during the dehydrogenation of ethylbenzene in a styrene device. Background Art

[0002] The existing styrene plants all use negative pressure adiabatic dehydrogenation process to produce styrene monomer technology for ethylbenzene dehydrogenation reaction. The process condensate produced by the dehydrogenation reaction unit is sent to the outside of the device as condensate after being treated by anthracite filter in industrial design. After oil and iron removal facilities or other simple treatments, it needs to be reused as desalted water (high-quality water).

[0003] In actual production operation, the process condensate has high contents of TOC (total organic carbon), Fe, SiO2, conductivity, etc., and contains trace aromatic hydrocarbons such as styrene, ethylbenzene, toluene, as well as particles and iron ions brought in by the catalyst. Even after the process condensate passes through anthracite filters and other treatments, it still cannot meet the water quality requirements of desalted water and can only be reused as cheap fresh water, which results in a certain waste of water and heat and causes certain economic losses to the enterprise. At the same time, the reuse of fresh water containing impurities will bring safety hazards to the normal operation of the production equipment. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for recovering process condensate produced during the dehydrogenation of ethylbenzene in a styrene device.

[0005] In order to achieve the above object, the technical solution of the present invention is: a method for recovering process condensate produced during the dehydrogenation of ethylbenzene in a styrene device, comprising the following steps:

[0006] (1) The process condensate enters the heat exchanger for heat recovery and utilization;

[0007] (2) The process condensate after heat exchange enters the composite fiber filter to remove impurities in the water;

[0008] (3) The condensate filtered by the composite fiber filter enters the ultra-fine iron removal filter to further remove iron impurities in the water;

[0009] (4) The condensate filtered by the ultrafine iron removal filter enters the polymer separation membrane filter for oil-water separation;

[0010] (5) After oil-water separation, water enters the anion bed, which is provided with anion exchange resin to remove anions from the water;

[0011] (6) Then the water enters the mixed bed, where a mixed ion exchange resin containing cations and anions is provided to further remove cations and anions from the water;

[0012] (7) The water freed of cations and anions enters the desalted water tank for desalination and recovery.

[0013] Furthermore, the heat exchanger in step (1) includes a primary heat exchanger and a secondary heat exchanger, and the process condensate enters the primary heat exchanger and the secondary heat exchanger in sequence.

[0014] Furthermore, the impurities in step (2) include TOC, colloid and iron.

[0015] Further; in step (5), the anion includes SO4 2- 、NO 3- , Cl - ,HSiO 3- , HCO 3- .

[0016] Furthermore, the process condensate flow rate is 220t / h.

[0017] Furthermore, the method further comprises step (8) wherein the desalinated water enters a heat exchanger for heat exchange and is then recovered.

[0018] Furthermore, step (8) is to recover the desalinated water after heat exchange by passing it into the heat exchanger through a heat exchanger cold water pump.

[0019] Furthermore; the heat exchanger, composite fiber filter, ultrafine iron removal filter, polymer separation membrane filter, anion bed, mixed bed, desalted water tank and heat exchanger cold water pump are all controlled by a control system, and the control system monitors, controls, alarms, data processes, data records and displays real-time / historical data curves for the entire process flow and operating conditions through a controller and a display.

[0020] The process condensate produced during the dehydrogenation of ethylbenzene in the styrene unit contains SO4 2- 、NO 3- , Cl - ,HSiO 3- , HCO 3- The ionic state of Si in the process condensate is mainly in the form of silicate ions (HSiO 3- ) exists in the form of. When the process condensate passes through the strong alkaline anion exchange resin layer, various anions in the water are adsorbed by the resin, and at the same time, the OH- in the resin is replaced and combined with H+ in the water to form water. As the running time increases, the exchange capacity of the anion resin gradually decreases, and when the effluent quality reaches the set control standard, it is considered invalid. At this time, based on the reversible characteristic of ion exchange reaction, a certain concentration of sodium hydroxide solution can be passed through the resin layer from bottom to top to restore the working capacity of the anion bed.

[0021] The process is expressed as a reaction:

[0022] ROH+HA→RA+H2O operation process

[0023] RA+OH - →ROH+A - Regeneration process

[0024] Where:

[0025] ROH, RA: represents anion exchange resin

[0026] HA: represents acidic compounds in water

[0027] OH - : Represents hydroxide ions in water.

[0028] Beneficial effects of the present invention: The present invention can process the condensate of the styrene recovery unit, remove TOC, colloid, iron in the water, and remove cations and anions (SO4 2- 、NO 3- , Cl - ,HSiO 3- , HCO 3- ) to meet the boiler desalted water (high quality) water quality standards, reduce the load of water treatment equipment, improve the economic benefits of the enterprise, and at the same time eliminate the safety hazards to the production equipment when used as circulating water replenishment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the process structure of the present invention. DETAILED DESCRIPTION

[0030] The composite fiber filter of the present invention was purchased from Beijing Zhongjing Linghang Technology Co., Ltd., model ZJSCF110 / 1800A;

[0031] The ultra-fine iron removal filter was purchased from Beijing Zhongjing Linghang Technology Co., Ltd., model ZJCI220 / 800A;

[0032] The polymer separation membrane filter was purchased from Beijing Zhongjing Linghang Technology Co., Ltd., model ZJCO220 / 2400A.

[0033] Example:

[0034] A method for recovering process condensate produced during the dehydrogenation of ethylbenzene in a styrene device comprises the following steps:

[0035] (1) The process condensate (80℃, 220t / h) enters the primary heat exchanger for heat exchange, and the process condensate (60℃, 220t / h) after heat exchange enters the secondary heat exchanger for heat recovery and utilization;

[0036] (2) The process condensate (40°C, 220t / h) after heat exchange enters the composite fiber filter to remove impurities such as TOC, colloid, and iron in the water;

[0037] (3) The condensate (40°C, 220 t / h) after being filtered by the composite fiber filter enters the ultra-fine iron removal filter to further remove iron impurities in the water;

[0038] (4) The condensate (40°C, 220 t / h) filtered by the ultrafine iron removal filter enters the polymer separation membrane filter for oil-water separation;

[0039] (5) After oil-water separation, water (40°C, 220 t / h) enters the anion bed, which is equipped with anion exchange resin to remove SO4 2- 、NO 3- , Cl - ,HSiO 3- , HCO 3- Anions;

[0040] (6) Then the water enters the mixed bed, where a mixed ion exchange resin containing cations and anions is provided to further remove cations and anions from the water;

[0041] (7) The water with cations and anions removed enters the desalination tank for desalination;

[0042] (8) The desalinated water enters the heat exchanger through the heat exchanger cooling water pump and is recovered after heat exchange.

[0043] The heat exchanger, composite fiber filter, ultrafine iron removal filter, polymer separation membrane filter, anion bed, mixed bed, desalted water tank and heat exchanger cold water pump are all controlled by a control system, and the control system monitors, controls, alarms, data processes, records data and displays real-time / historical data curves for the entire process flow and operating conditions through a controller and a display.

[0044] The initial water inlet index of the condensate of the process of the present invention is shown in Table 1, and the final water production meets the water production index, and the water production index is shown in Table 2.

[0045] Table 1 Process condensate inlet index

[0046] Serial number name Design indicators Measured value (average of three measurements) 1 TOC ≤20mg / L 6.8 2 Fe content ≤200 μg / L 165 3 Hydrogen conductivity (25℃) ≤20μS / cm 17 4 <![CDATA[SiO2]]> ≤2mg / L 1.19 5 Suspended matter ≤5ppm / 6 temperature ≤85℃ 80 7 Inlet water pressure 0.885MPa /

[0047] Table 2 Process condensate water production indicators

[0048] name Design Specifications TOC ≤0.5mg / L Fe content ≤30 μg / L Hydrogen conductivity (25℃) ≤0.2μs / cm <![CDATA[SiO2]]> ≤20 μg / L

[0049] The above-described embodiments are only preferred solutions of the present invention and are not intended to limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solutions described in the claims.

[0050] In the description of the present invention, it is necessary to understand that the terms indicating orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

Claims

1. A method for recovering process condensate produced during the dehydrogenation of ethylbenzene in a styrene device, characterized in that: The following steps are involved: (1) The process condensate enters the heat exchanger for heat recovery and utilization; (2) The process condensate after heat exchange enters the composite fiber filter to remove impurities in the water; (3) The condensate filtered by the composite fiber filter enters the ultra-fine iron removal filter to further remove iron impurities in the water; (4) The condensate filtered by the ultrafine iron removal filter enters the polymer separation membrane filter for oil-water separation; (5) After oil-water separation, water enters the anion bed, which is provided with anion exchange resin to remove anions from the water; (6) Then the water enters the mixed bed, where a mixed ion exchange resin containing cations and anions is provided to further remove cations and anions from the water; (7) The water freed of cations and anions enters the desalted water tank for desalination and recovery.

2. The method for recovering the process condensate produced in the ethylbenzene dehydrogenation process of a styrene device according to claim 1, characterized in that: The heat exchanger in step (1) includes a primary heat exchanger and a secondary heat exchanger, and the process condensate enters the primary heat exchanger and the secondary heat exchanger in sequence.

3. The method for recovering the process condensate produced in the ethylbenzene dehydrogenation process of the styrene device according to claim 1, characterized in that: The impurities in step (2) include TOC, colloid and iron.

4. The method for recovering the process condensate produced in the ethylbenzene dehydrogenation process of a styrene device according to claim 1, characterized in that: In step (5), the anion includes SO4 2- 、NO 3- , Cl - ,HSiO 3- , HCO 3- .

5. The method for recovering the process condensate produced in the ethylbenzene dehydrogenation process of a styrene device according to claim 1, characterized in that: The process condensate flow rate is 220t / h.

6. The method for recovering process condensate produced in the ethylbenzene dehydrogenation process of a styrene device according to claim 1, characterized in that: The step also includes: the desalinated water enters a heat exchanger for heat exchange and is then recovered.

7. The method for recovering the process condensate produced in the ethylbenzene dehydrogenation process of a styrene device according to claim 6, characterized in that: Step (8) is to recover the desalinated water after entering the heat exchanger through the heat exchanger cold water pump for heat exchange.

8. The method for recovering process condensate produced in the ethylbenzene dehydrogenation process of a styrene device according to claim 7, characterized in that: The heat exchanger, composite fiber filter, ultrafine iron removal filter, polymer separation membrane filter, anion bed, mixed bed, desalted water tank and heat exchanger cold water pump are all controlled by a control system, and the control system monitors, controls, alarms, data processes, records data and displays real-time / historical data curves for the entire process flow and operating conditions through a controller and a display.

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