CN111234884A - System and control method for absorbing CO2 in pyrolysis gas using calcium-based absorbent - Google Patents

Abstract

The invention discloses a method for absorbing CO in pyrolysis gas by using a calcium-based absorbent₂The system comprises a front end inlet pipeline, a gas flow control device, CO which are connected in sequence₂The content testing device, the middle pipeline and the rear end outlet pipeline; the system also includes a process controller, which is separately connected to the CO₂The content testing device is connected with the middle pipeline; the middle pipeline comprises a plurality of branch pipelines, a valve is arranged at the pipeline opening of each branch pipeline, and a calcium-based absorbent is arranged in each branch pipeline; the process controller receives the CO₂CO emitted by content testing device₂Content signal and control of corresponding branch pipeA valve in the way. The system has the advantages of prolonging the service life of the absorbent (especially the absorbent with high price and small particle size), and treating CO₂The pyrolysis gas with wider content range, more stable product quality and the system can replace the absorbent without stopping working.

Description

System and control method for absorbing CO2 in pyrolysis gas using calcium-based absorbent

technical field

The technical field to which the present invention relates is the field of industrial process control, in particular to a pipeline system and a control method for a calcium-based absorbent to absorb carbon dioxide in pyrolysis gas.

Background technique

Through the thermal utilization method, the process of recycling solid waste is usually as follows: organic solid waste is heated in an inert atmosphere to generate high-temperature pyrolysis gas, the high-temperature pyrolysis gas is catalytically reformed to generate pyrolysis gas, and the pyrolysis gas is The main components are CO, H ₂ , CH ₄ , CO ₂ , nitrogen compounds and sulfur compounds; the pyrolysis gas will be an ideal gas fuel after desulfurization, denitrification and CO ₂ removal.

The difficulty of the above-mentioned ideal gas fuel from pyrolysis gas lies in how to efficiently catalytic reforming, denitrification and desulfurization, and CO ₂ removal. The CO ₂ retained in the pyrolysis gas will reduce its calorific value, and the direct emission of CO ₂ will aggravate the greenhouse effect and worsen the climate; therefore, it is necessary to remove the CO ₂ in the pyrolysis gas. The technical problem to be solved by the present invention is the removal of CO ₂ from the pyrolysis gas.

In industrial production, calcium-based circulating absorbents are often selected to remove CO ₂ , and the main chemical equation in a cycle is:

However, as the number of cycles increases, the above-mentioned absorbent will sinter, resulting in a decrease in the effective surface area and a greatly reduced absorption capacity. Therefore, prolonging the service life of absorbents is an important research topic. At present, the main idea is to chemically modify CaO or add other components to the absorbent to improve the life of the absorbent. On the other hand, the present invention provides an optimized pipeline system from the perspective of industrial process control, and cooperates with a reasonable control method to prolong the service life of the absorbent.

Experiments show that the influence factors of the adsorption capacity of calcium-based adsorbents are in descending order of significance: mixed gas flow, carbon dioxide content, carbonation temperature, and adsorbent particle size. When the carbon dioxide content in the pyrolysis gas is high, the carbon dioxide can rapidly carbonize the adsorbent, which means that the capacity of the larger particle size adsorbent to treat the high content carbon dioxide pyrolysis gas is equivalent to that of the small particle size adsorbent. When the content of carbon dioxide in the pyrolysis gas is low, the adsorption capacity of the small particle size adsorbent is stronger than that of the large particle size adsorbent. Therefore, if the content of CO ₂ in the product is required to be stable and the consumption of small particle size adsorbents is minimized, only small particle size adsorbents should be used to treat low-content CO ₂ pyrolysis gas. In the present invention, the pyrolysis gas temperature is assumed to be 600-700°C and the pyrolysis gas flow rate is controlled by a flow meter.

The infrared absorption spectrum of a molecule can reflect the functional group or chemical bond type of the molecule to infer the molecular formula; for a mixture of simple molecules, if the overlap between the characteristic peaks of the functional groups is small (that is, the characteristic wavenumber difference between the functional groups is large) and the characteristic peaks are sufficient. Intensity, and the number of the molecule is not too small, the mixture can also be quantitatively analyzed by infrared absorption spectroscopy.

After the pyrolysis gas is desulfurized and denitrified, the main components are: CO, H ₂ , CH ₄ , and CO ₂ . The characteristic functional groups or chemical bonds existing in each molecule in the pyrolysis gas are known; they are mainly (characteristic wavenumber/cm ^-1 in brackets): carbon-oxygen triple bond (2150), hydrogen-hydrogen single bond (no absorption peak in mid-infrared region) , carbon-hydrogen single bonds (2913.0, 1533.3, 3018.9, 1305.9), carbon-oxygen double bonds (2349, 1340, 667). The characteristic peaks of the above-mentioned main characteristic functional groups or chemical bonds are quite different, so it is possible to detect the CO ₂ content in the pyrolysis gas by infrared absorption spectroscopy.

Fourier transform infrared spectrometer is used in the present invention; this type of infrared spectrometer has the advantages of short scanning interval and high signal-to-noise ratio, and can meet the requirements of high-precision real-time monitoring of changes in the content of pyrolysis gas components.

SUMMARY OF THE INVENTION

The purpose of the present invention is to propose a new idea to solve the problem of how to prolong the service life of the calcium-based circulating absorbent in the application of removing CO ₂ from the pyrolysis gas with the calcium-based circulating absorbent. The common idea is to modify the absorbent, and the present invention adopts an industrial process control method to provide an optimized pipeline system, with a reasonable control method, to improve the life of the absorbent and to handle pyrolysis with a wider range of _CO2 content. gas.

The object of the present invention is achieved by one of the following technical solutions.

The invention provides a system for absorbing CO ₂ in pyrolysis gas using a calcium-based absorbent, comprising a front-end inlet pipeline, a gas flow control device, a CO ₂ content testing device, a middle pipeline and a rear-end outlet pipeline connected in sequence; The system also includes a processing controller, which is respectively connected with the CO ₂ content testing device and the intermediate pipeline; the intermediate pipeline includes several branch pipelines, each branch pipeline is provided with a valve at the pipeline mouth, and the branch pipeline is provided with calcium base Absorbent; the treatment controller receives the CO ₂ content signal sent by the CO ₂ content test device and controls the valve on the corresponding branch pipeline.

Preferably, the CO ₂ content testing device is a Fourier transform infrared spectrometer.

Preferably, the calcium-based absorbent is distributed in the middle of the branch pipes.

Preferably, the intermediate pipe includes 4-6 branch pipes.

Preferably, the particle size of the calcium-based absorbent in each branch pipe is different.

Preferably, the particle sizes of the calcium-based absorbents in each branch pipe are distributed in a gradient.

Preferably, when the pyrolysis gas flow is at 50-70ml/min and the working temperature is at 600-700°C, the volume content of _CO2 is at (6%, 10%], (10%, 14%], (14%, 18 %], (18%, 22%], the corresponding particle size ranges of calcium-based absorbents are (75μm, 120μm], (120μm, 180μm], (180μm, 250μm], (250μm, 380μm), respectively.

Preferably, the processing controller is connected with the CO ₂ content testing device and the intermediate pipeline through wires, respectively.

Preferably, the processing controller includes a signal processor and a digital power supply, the signal processor is used for receiving the _CO2 content signal sent by the _CO2 content testing device and outputting the valve switch signal, and the digital power supply receives the valve switch signal through the wire and controls the corresponding branch pipeline valve switching action.

The present invention also provides a method for controlling the system for absorbing _CO in the pyrolysis gas using a calcium-based absorbent, comprising the following steps:

(1) Set CO ₂ content intervals for each branch pipe of the processing controller and the intermediate pipe, and arrange calcium-based absorbents in each branch pipe of the intermediate pipe according to the CO ₂ content interval;

(2) pass the pyrolysis gas into the front-end inlet pipeline, and through the front-end inlet pipeline, after the flow is controlled by the gas flow control device, enter the CO ₂ content testing device to obtain the CO ₂ content;

(3) The processing controller receives the _CO2 content signal transmitted in step (2), compares it with the _CO2 content interval preset in step (1), and obtains the valve switch signal, and the processing controller controls the corresponding branch according to the valve switch signal The valve switch action of the pipeline;

(4) The pyrolysis gas flows through the branch pipe where the valve performs the opening action, the calcium-based absorbent of the branch pipe removes CO ₂ in the pyrolysis gas, and the pyrolysis gas from which CO ₂ is removed is discharged through the rear end outlet pipe.

Preferably, the pyrolysis gas is a pyrolysis gas that has been desulfurized and denitrogenated.

Compared with the prior art, the present invention has the following beneficial effects and advantages:

(1) Extend the service life of the absorbent (especially the small particle size absorbent with higher price), the system provided by the present invention can select the optimal particle size of the CO ₂ absorbent according to the carbon dioxide content of the pyrolysis gas in the pipeline , adjust the different gas guide paths of the pyrolysis gas through the intermediate pipeline, so that the gas passes through the absorbent with the optimal particle size. When the aforementioned Fourier transform infrared spectrometer detects a lower CO ₂ content, a smaller particle size absorbent with a higher price will be selected; this will play a design effect of rational and efficient use of the absorbent, and prolong the use of the absorbent life;

(2) The system provided by the present invention can process the pyrolysis gas with a wider range of CO ₂ content. For different gas guide paths of the intermediate pipeline, according to the particle size gradient distribution, the pipeline system can be used to process the thermal decomposition gas with a wider range of carbon dioxide content. relieve gas;

(3) The product quality is more stable. The absorbent is selected according to the CO ₂ content in the pyrolysis gas, and the CO ₂ content of the products produced by the back-end outlet pipeline can also be more stable. No matter whether the CO ₂ content in the pyrolysis gas is high or low, all The CO ₂ content in the product can be reduced to a qualified unified standard;

(4) The system provided by the present invention can replace the adsorbent without stopping the operation, and the operation is more convenient. When replacing the adsorbent, the use of only a certain branch pipeline can be suspended, and the other branches can continue to work, so that the system can be realized. The absorbent can be replaced without stopping work.

Description of drawings

Fig. 1 is a kind of structural representation of the system that utilizes calcium-based absorbent to absorb _CO in pyrolysis gas provided by the embodiment;

In the figure: 1-front inlet pipe; 2-intermediate pipe; 3-back end outlet pipe; 4-CO ₂ content testing device; 5-treatment controller; 6-valve; 7-calcium-based absorbent; 8-signal processing 9- digital power supply; 10- gas flow control device.

Detailed ways

The specific implementation of the present invention will be further described below with reference to specific embodiments and accompanying drawings, but the implementation of the present invention is not limited thereto.

This embodiment provides a system for absorbing CO ₂ in pyrolysis gas using a calcium-based absorbent. As shown in FIG. 1 , it includes a front-end inlet pipeline 1 , a gas flow control device 10 , a CO ₂ content testing device 4 , and a front-end inlet pipeline 1 connected in sequence. The intermediate pipeline 2 and the back-end outlet pipeline 3; the system also includes a processing controller 5, which is respectively connected with the CO ₂ content testing device 4 and the intermediate pipeline 2; the intermediate pipeline 2 includes 4 branch pipelines, each There are valves 6 at the pipe mouths of the branch pipes, which are #1, #2, #3 and #4 respectively, and the corresponding branch pipes are #1 branch pipe, #2 branch pipe, #3 branch pipe and 4# branch pipe respectively Each branch pipe is provided with calcium-based absorbent 7; the processing controller 5 receives the CO ₂ content signal sent by the CO ₂ content test device 4 and controls the valve 6 on the corresponding branch pipe.

The CO ₂ content testing device 4 is a Fourier transform infrared spectrometer. The calcium-based absorbent 7 is distributed in the middle of the branch pipe. The particle sizes of the calcium-based absorbents in each branch pipe are different. The particle size distribution among the calcium-based absorbents in each branch pipe is gradient. The particle size of the calcium-based absorbent in the #1 branch pipe is 75-120 microns, and the corresponding _CO2 content range is (6%, 10%), and the particle size of the calcium-based absorbent in the #2 branch pipe is 120-180 Micron, the corresponding CO ₂ content range is (10%, 14%], the particle size of the calcium-based absorbent in the #3 branch pipe is 180-250 microns, and the corresponding CO ₂ content range is (14%, 18%], # The particle size of the calcium-based absorbent in the 4-branch pipeline is 250-380 microns, and the corresponding CO ₂ content range is (18%, 22%), and the CO ₂ content is lower than the minimum boundary value of (6%, 10%). 1# branch pipeline, when it is higher than the highest boundary value (18%, 22%), it still corresponds to 4# branch pipeline.

The processing controller 5 is connected with the CO ₂ content testing device 4 and the intermediate pipeline 2 through wires, respectively. The processing controller 5 includes a signal processor 8 and a digital power supply 9. The signal processor 8 is used to receive the _CO2 content signal sent by the _CO2 content testing device 4 and output the valve switch signal. The digital power supply 9 receives the valve switch signal through the wire and controls the signal. The valve switch action of the corresponding branch pipeline.

The present invention also provides a method for controlling the system for absorbing _CO in the pyrolysis gas using a calcium-based absorbent, comprising the following steps:

(1) The C++ high-level programming language is used to write the processing controller code (the following is only an example):

(2) Set CO ₂ content intervals for the processing controller 5 and the 4 branch pipes of the intermediate pipe 2, and arrange the calcium-based absorbent 7 in the 4 branch pipes of the intermediate pipe 2 according to the CO ₂ content interval; control the gas flow The device 10 sets the flow rate to 60ml/min; the signal processor 8 is set to record the CO ₂ content at an interval of 20s, that is, to receive a signal from the CO ₂ content testing device 4, namely the Fourier transform infrared spectrometer, every 20s. In actual production, the input interval should be greater than the scanning interval of the Fourier transform infrared spectrometer, so as to avoid invalid calculation by the signal processor 8;

(3) Pass the denitrified and desulfurized pyrolysis gas into the front-end inlet pipeline 1, and enter the CO ₂ content testing device 4 through the front-end inlet pipeline 1 to obtain the CO ₂ content, and the present embodiment measures the _CO volume of the pyrolysis gas altogether. The content is 4%, 8%, 12%, 16%, 20%, 24% respectively;

(4) The processing controller 5 receives the CO ₂ content signal transmitted in step (2), compares it with the CO ₂ content interval preset in step (1), and obtains the valve switch signal (0 is the closing action, 1 is the opening action) , the processing controller 5 controls the valve switching action of the corresponding branch pipeline according to the valve switching signal, and the switching state of the valve 6 corresponding to each CO ₂ content is shown in Table 1;

Table 1

(5) The branch pipe where the pyrolysis gas flows through the valve 6 to perform the opening action, the calcium-based absorbent 7 of the branch pipe removes CO ₂ in the pyrolysis gas, and the pyrolysis gas from which CO ₂ is removed passes through the rear end outlet pipe 3 discharge.

The system and control method provided in this embodiment can process the pyrolysis gas with a volume content of CO ₂ ranging from 6% to 22%; and only when the pyrolysis gas with a low content CO ₂ is processed, the absorbent with large particle size and mesh size will be lost. absorbent. In addition, the quality of the product coming out of the back-end outlet pipeline remains stable despite changes in CO ₂ content. Also, if desired, calcium-based absorbents that are not in working condition can be replaced without shutting down the system.

The above-described embodiments are only preferred embodiments of the present invention, and are not intended to limit the scope of implementation of the present invention, so all changes made according to the shape and principle of the present invention should be included within the protection scope of the present invention.

Claims (10)

1. utilize calcium-based absorbent to absorb _CO in the pyrolysis gas system, it is characterized in that, comprise the front-end inlet pipeline, gas flow control device, _CO content testing device, intermediate pipeline and back-end outlet pipeline that are connected successively; The system also includes a processing controller, which is respectively connected with the CO ₂ content testing device and the intermediate pipeline; the intermediate pipeline includes several branch pipelines, each branch pipeline is provided with a valve at the pipeline mouth, and the branch pipeline is provided with calcium base Absorbent; the treatment controller receives the CO ₂ content signal sent by the CO ₂ content test device and controls the valve on the corresponding branch pipeline. 2. The system according to claim 1, wherein the _{CO 2 content} testing device is a Fourier transform infrared spectrometer. 3. The system for absorbing _CO2 in pyrolysis gas using calcium-based absorbent according to claim 1, characterized in that the calcium-based absorbent is distributed in the middle of the branch pipe. 4. The system for absorbing _CO2 in pyrolysis gas using a calcium-based absorbent according to claim 1, wherein the intermediate pipeline comprises 4-6 branch pipelines. 5 . The system for absorbing CO ₂ in pyrolysis gas using calcium-based absorbent according to claim 1 , wherein the particle size of the calcium-based absorbent in each branch pipe is different. 6 . 6 . The system for absorbing CO ₂ in pyrolysis gas using calcium-based absorbent according to claim 1 , wherein the particle size distribution between the calcium-based absorbents in each branch pipe is in a gradient distribution. 7 . 7. The system for absorbing _CO in pyrolysis gas using calcium-based absorbent according to claim 1, is characterized in that, when the flow rate of pyrolysis gas is at 50-70ml/min and the working temperature is at 600-700°C, CO ₂ The particle sizes of the calcium-based absorbents corresponding to the pyrolysis gas with volume content of (6%, 10%], (10%, 14%], (14%, 18%], (18%, 22%) are respectively ( 75μm, 120μm], (120μm, 180μm], (180μm, 250μm], (250μm, 380μm]. 8 . The system for absorbing CO ₂ in pyrolysis gas using a calcium-based absorbent according to claim 1 , wherein the processing controller is respectively connected with the CO ₂ content testing device and the intermediate pipeline through wires. 9 . 9. the system that utilizes calcium-based absorbent to absorb CO in the pyrolysis gas according to claim ₁ , is characterized in that, the processing controller comprises a signal processor and a digital power supply, and the signal processor is used to receive CO _The content testing device sends out The CO ₂ content signal and output valve switch signal, the digital power supply receives the valve switch signal through the wire and controls the valve switch action of the corresponding branch pipeline. 10. The method for controlling the system of utilizing calcium-based absorbent to absorb _CO in pyrolysis gas according to any one of claims 1 to 9, characterized in that, comprising the following steps: (1) Set CO ₂ content intervals for the processing controller and each branch pipeline of the intermediate pipeline, and arrange calcium-based absorbents in each branch pipeline of the intermediate pipeline according to the CO ₂ content interval; (2) Pass the pyrolysis gas into the front-end inlet pipeline, and after the gas flow control device controls the flow through the front-end inlet pipeline, it enters the CO ₂ content testing device to obtain the CO ₂ content; (3) The processing controller receives the CO ₂ content signal transmitted in step (2), compares it with the CO ₂ content interval preset in step (1), and obtains the valve switch signal, and the processing controller controls the corresponding branch according to the valve switch signal The valve switch action of the pipeline; (4) The pyrolysis gas flows through the branch pipe where the valve performs the opening action. The calcium-based absorbent of the branch pipe removes CO ₂ in the pyrolysis gas, and the pyrolysis gas from which CO ₂ is removed is discharged through the rear end outlet pipe.

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