CN102266701B - A treatment method for waste gas in chemical acrylamide production - Google Patents

Abstract

The invention relates to a method for treating waste gas in the production of acrylamide by a chemical method; the waste gas enters a waste gas pre-cooler, and the temperature of the waste gas is cooled to 10-30 ℃; the cooled waste gas is sent into a waste gas adsorber, the waste gas adsorber is formed by connecting three adsorbers in series, the media filled in the adsorbers are powdered activated carbon, granular activated carbon or fibrous activated carbon, two adsorbers in the three adsorbers are connected in series for on-line work at the same time, the waste gas after adsorption treatment is directly discharged into the atmosphere, the other adsorber uses saturated steam to resolve the acrylonitrile adsorbed on the adsorption media, and the resolved acrylonitrile and the resolved steam are recycled after being cooled by a recycled acrylonitrile cooler; the three adsorbers are sequentially subjected to adsorption and analysis operations and automatically switched; the waste gas treated by the method can reach the environmental-friendly emission standard, post-treatment such as incineration or oxidation is not needed, the investment and process consumption are saved, the acrylonitrile is recycled to the maximum extent, and the purposes of energy conservation and emission reduction are achieved.

Description

A treatment method for waste gas in chemical acrylamide production

technical field

The invention relates to a method for treating waste gas in the production of chemical acrylamide.

Background technique

At present, in the production process of chemical acrylamide, the waste gas generated is usually treated by direct incineration or absorbing and recovering the acrylonitrile and then oxidized or incinerated to ensure that the emission of waste gas in the production process of acrylamide meets the requirements of environmental protection. . Due to the large amount of waste gas produced in the production process of chemical acrylamide, usually 1500Nm ³ of waste gas is produced per ton of acrylamide, a lot of fuel is required for incineration or oxidation, and it contains a lot of acrylonitrile, resulting in fuel and Acrylonitrile waste.

Contents of the invention

The purpose of the present invention is to provide a treatment method for waste gas in the production of chemical acrylamide, which can make the discharge of waste gas meet the requirements of environmental protection, and at the same time recover the largest amount of acrylonitrile and consume the least amount of energy, so as to overcome the existing methods The energy consumption is large, and the loss of acrylonitrile is large.

A method for treating waste gas in the production of chemical acrylamide, the equipment used includes a waste gas pre-cooler, a fan, a waste gas adsorber, and a cooler for recovering acrylonitrile, characterized in that the waste gas discharged in the production of chemical acrylamide first enters the waste gas In the pre-cooler, the temperature of the exhaust gas is cooled to 10-30°C, preferably 18-20°C; then the cooled exhaust gas is sent to the exhaust gas adsorber by the fan, and the exhaust gas adsorber is composed of three adsorbers connected in series , the medium filled in the adsorber is powdered activated carbon, granular activated carbon, and fibrous activated carbon. Among the three adsorbers, two adsorbers work in series and online at the same time. The waste gas after adsorption treatment is directly discharged into the atmosphere, and the other adsorber uses saturated The steam decomposes the acrylonitrile adsorbed on the adsorption medium, and the decomposed acrylonitrile and steam are recycled after being cooled by the recovery acrylonitrile cooler; the three adsorbers perform adsorption and desorption operations in sequence and switch automatically; The flow rate and the amount of acrylonitrile contained in the exhaust gas are determined, the switching time of the adsorber is determined according to the content requirement index of acrylonitrile in the exhaust gas after adsorption, and the analysis time of the adsorber is determined according to the adsorption operation time of the adsorber.

This method uses sticky-based activated carbon fibers in fibrous activated carbon with excellent adsorption properties for organic vapors. The specific surface area of the activated carbon fibers can be as high as 2600m/g, the pore size distribution is narrow, and the micropore volume can reach 1.23/g, which is especially suitable for large flow rates. Waste gas treatment.

The present invention has the following characteristics due to the adoption of the above technical scheme:

1. In the present invention, the waste gas is pre-cooled to ensure that the acrylonitrile is fully adsorbed in the adsorber.

2. The exhaust gas adsorber used in the present invention has 3 adsorbers, of which 2 adsorbers are connected in series for adsorption, and 1 adsorber is for analysis. They can be automatically switched and processed continuously, which can achieve the complete absorption of exhaust gas by the adsorber and the complete absorption of the adsorber. Analysis, to ensure that the exhaust gas is qualified after being absorbed by the exhaust gas adsorber and is not incinerated or oxidized.

3. The present invention does not require incineration or post-oxidation treatment of waste gas, not only is the method simple, but also saves a lot of energy and reduces the loss of acrylonitrile.

Description of drawings

Fig. 1 is a schematic diagram of the process of treating waste gas in the present invention.

In the figure, 1-exhaust gas adsorber A, 2-exhaust gas adsorber B, 3-exhaust gas adsorber C, 4-exhaust gas pre-cooler, 5-first-level fan, 6-secondary fan, 7-recovery acrylonitrile cooler .

Detailed ways

Taking the exhaust gas treatment process of a chemical acrylamide plant with a daily output of 150 tons of acrylamide as an example, the present invention will be further described in detail.

See Figure 1. Exhaust gas adsorber No. A1, exhaust gas adsorber No. B2, exhaust gas adsorber C3, exhaust gas pre-cooler 4, primary fan 5, secondary fan 6, and recovery acrylonitrile cooler 7.

The exhaust gas pre-cooler adopts a finned heat exchanger with a heat exchange area of 260m ² and uses 18°C cooling water for cooling; both the primary fan and the secondary fan use centrifugal fans with a processing capacity of 12000m ³ /h; exhaust gas adsorption The size of the three adsorbers of the device is 9m in length and 2.5m in diameter, and the adsorption medium adopts sticky activated carbon fiber; the recovery acrylonitrile cooler adopts shell and tube heat exchanger with a heat exchange area of 30m ² Cooling water; the steam used is low-pressure steam with a pressure of 1.0MPa.

In the specific process of the present invention, the flow rate of the waste gas discharged from the production process is 11000Nm ³ /h, and the content of acrylonitrile in the waste gas is 4000-6000μg/ml. The exhaust gas first passes through the exhaust gas pre-cooler 4, and after being cooled to 18°C, it is sent to the exhaust gas adsorber A1 by the first-stage fan 5 to absorb the acrylonitrile in it, and the exhaust gas adsorbed by the adsorber A1 is sent to the exhaust gas by the second-stage fan 6. Adsorber B2 continues to absorb the residual acrylonitrile, and the content of acrylonitrile in the waste gas absorbed by adsorber B2 is below 5 μg/ml, and such waste gas can be directly discharged into the atmosphere. When the adsorber A1 and the adsorber B2 are in the exhaust gas adsorption state, the adsorber C3 is in the state of decomposing the acrylonitrile adsorbed on the sticky activated carbon fiber with low-pressure steam, and the decomposed acrylonitrile and steam are sent to the recovery acrylonitrile cooler 7. The recovered acrylonitrile is cooled to 20°C and stored in storage tanks for recycling. According to the flow rate of the waste gas, the content of acrylonitrile in the waste gas, the emission index of the waste gas, and the ability of the waste gas adsorber to absorb acrylonitrile, the adsorption operation time of the two waste gas adsorption units is 60 minutes, and the analysis operation time of the waste gas adsorption unit is 10 minutes. When the adsorption time of the adsorber A1 reaches 30 minutes, the adsorber A1 switches to the analysis state, the adsorber C3 after the analysis is completed switches to the adsorption state, when the adsorption time of the adsorber B2 reaches 30 minutes, the adsorber B2 switches to the analysis state, and the adsorber A1 The position of the adsorber B2 is replaced by the adsorption operation, and the three adsorption units are sequentially switched between adsorption and analysis operations, and the adsorption unit of the adsorber automatically performs the switching operation according to the program setting.

Claims (1)

1. A chemical method acrylamide produce in the processing method of waste gas, the equipment used comprises waste gas precooler, blower fan, waste gas absorber, recover acrylonitrile cooler, it is characterized in that: waste gas precooler (4) adopts finned heat exchanger, and heat exchange area is 260m ², adopt the cooling water of 18 ℃ to carry out cooling; One-level blower fan (5) and secondary blower fan (6) all adopt centrifugal blower, and disposal ability is 12000m ³/ h; Waste gas absorber A(1), waste gas absorber B(2), waste gas absorber C(3) be of a size of length and be 9m, diameter is 2.5m, adsorbing medium adopts sticky based activated carbon fiber; The recover acrylonitrile cooler adopts shell-and-tube heat exchanger, and heat exchange area is 30m ², adopt the cooling water of 18 ℃; The steam used is low-pressure steam, and pressure is 1.0MPa;

   The detailed process of processing method is: the exhaust gas flow that production process is discharged is 11000Nm ³/ h, in waste gas, the content of acrylonitrile is 4000～6000 μ g/ml, at first waste gas pass through waste gas precooler (4), be cooled to after 18 ℃ and be sent to waste gas absorber A(1 by one-level blower fan (5)) absorption acrylonitrile wherein, through waste gas absorber A(1) waste gas after absorption is sent to waste gas absorber B(2 by secondary blower fan (6)) in continue wherein remaining acrylonitrile of absorption, through waste gas absorber B(2) content of acrylonitrile, will be through waste gas absorber B(2 below 5 μ g/ml in waste gas after absorption) waste gas after adsorbing directly is drained in atmosphere, at waste gas absorber A(1) and waste gas absorber B(2) when the waste gas adsorbed state, waste gas absorber C(3) in resolve the state of the acrylonitrile adsorbed on sticky based activated carbon fiber with low-pressure steam, the acrylonitrile of resolving and steam are fed to recover acrylonitrile cooler (7), and the acrylonitrile of recovery is stored in storage tank and is recycled after being cooled to 20 ℃, according to the ability of the adsorbs propylene nitrile of content, toxic emission index and the waste gas absorber of acrylonitrile in the flow of waste gas, waste gas, the adsorption operations time of two waste gas absorbers is 60min altogether, and the parse operation time of waste gas absorber is 10min, as waste gas absorber A(1) after adsorption time reaches 30min, waste gas absorber A(1) be switched to parse state, resolve complete waste gas absorber C(3) switch to adsorbed state, as waste gas absorber B(2) after adsorption time reaches 30min, waste gas absorber B(2) switch to parse state, waste gas absorber A(1) adsorption operations is carried out in position replacement waste gas absorber B(2), three waste gas absorbers adsorb and the parse operation switching successively, in three absorbers, there are two absorbers to connect and work online simultaneously, the waste gas absorber carries out handover operation automatically according to programming.

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