Treatment method and application of waste gas generated by acid steam explosion of cellulose

Abstract

The invention relates to the field of preparation of ethanol from cellulose, and discloses a treatment method and application of waste gas generated by acid steam explosion of cellulose, the treatment method comprises the following steps: (1) washing the waste gas for the first time with water at the temperature of 90-100 DEG C; (2) condensing the waste gas washed for the first time and then carrying out alkali washing; wherein the content of alkali in a detergent used for alkali washing is 2-6 wt%, and the alkali is inorganic alkali; (3) the waste gas obtained after alkali washing is subjected to secondary washing with water, and the temperature of secondary washing is 50-60 DEG C lower than that of primary washing; and (4) the waste gas washed for the second time is adsorbed by activated carbon after passing through a demister. The treatment method provided by the invention solves the problem of up-to-standard emission of waste gas generated by acid steam explosion of cellulose in the process of preparing ethanol from cellulose.

Description

Technical Field

[0001] This invention relates to the field of ethanol production from cellulose, and more specifically, to a method for treating waste gas generated from acid vapor explosion of cellulose. Background Technology

[0002] Currently, the specific process flow for treating waste steam from corn-based ethanol production is as follows: waste heat steam from the drying unit is washed in a scrubbing tower to remove solid particles and soluble waste gases. The cleaned waste steam then enters a steam exchanger for heat recovery, and finally, the non-condensable steam is discharged through a fan. However, in the process of cellulose-to-ethanol production, the above process cannot meet emission standards when treating the waste gas generated by acid vapor explosion during cellulose production. Therefore, it is urgent to design a method for treating the waste gas generated by acid vapor explosion during cellulose-to-ethanol production. Summary of the Invention

[0003] The purpose of this invention is to overcome the problem in the prior art that the waste gas generated by acid explosion of cellulose in the process of cellulose to produce ethanol cannot meet the emission standards, and to provide a method for treating the waste gas generated by acid explosion of cellulose, which makes the waste gas generated by acid explosion of cellulose far meet the emission standards.

[0004] To achieve the above objectives, a first aspect of the present invention provides a method for treating waste gas generated from cellulose acid vapor explosion, the method comprising:

[0005] (1) The exhaust gas is washed with water for the first time, and the temperature of the first wash is 90-100℃;

[0006] (2) The exhaust gas after the first washing is condensed and then subjected to alkaline washing; wherein the alkaline content of the detergent used in the alkaline washing is 2-6 wt%, and the alkaline is an inorganic alkali;

[0007] (3) The waste gas after alkaline washing is washed a second time with water. The temperature of the second washing is 50-60℃ lower than that of the first washing.

[0008] (4) The exhaust gas after the second washing is adsorbed by activated carbon after passing through the demister.

[0009] A second aspect of the present invention provides the application of the above-described processing method in the process of preparing ethanol from cellulose.

[0010] Through the above technical solution, the present invention can achieve at least the following beneficial effects: the treatment method of the present invention solves the problem of the emission of waste gas generated by acid vapor explosion of cellulose in the process of cellulose to prepare ethanol, and the preferred embodiment of the present application also effectively removes the odor in the waste gas. Attached Figure Description

[0011] Figure 1 The process flow diagrams are for Examples 1-3. Detailed Implementation

[0012] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0013] The first aspect of this invention provides a method for treating waste gas generated from cellulose acid vapor explosion, the method comprising:

[0014] (1) The exhaust gas is washed with water for the first time, and the temperature of the first wash is 90-100℃;

[0015] (2) The exhaust gas after the first washing is condensed and then subjected to alkaline washing; wherein the alkaline content of the detergent used in the alkaline washing is 2-6 wt%, and the alkaline is an inorganic alkali;

[0016] (3) The waste gas after alkaline washing is washed a second time with water. The temperature of the second washing is 50-60℃ lower than that of the first washing.

[0017] (4) The exhaust gas after the second washing is adsorbed by activated carbon after passing through the demister.

[0018] In this invention, preferably, in step (1), the conditions for the first wash may include: a temperature of 95-100℃ (for example, a range formed by any two values ​​among 95℃, 96℃, 97℃, 98℃, 99℃, and 100℃, and values ​​within that range), a pressure of -100PaG to -50PaG (for example, a range formed by any two values ​​among -100PaG, -95PaG, -90PaG, -85PaG, -80PaG, -75PaG, -70PaG, -65PaG, -60PaG, -55PaG, and -50PaG, and values ​​within that range), and a washing time of 5-30s (for example, a range formed by any two values ​​among 5s, 8s, 10s, 12s, 15s, 18s, 20s, 22s, 25s, 27s, and 30s, and values ​​within that range).

[0019] In this invention, preferably, relative to 1m 3 For the exhaust gas, the water volume for the first washing can be 0.2-1L, preferably 0.3-0.6L (for example, it can be any two values ​​formed by 0.3L, 0.4L, 0.5L, and 0.6L, or values ​​within that range).

[0020] In a preferred embodiment of the present invention, the method further includes: sending the waste gas and wastewater generated after the first washing into an evaporator for energy recovery, and then condensing them.

[0021] In this invention, preferably, the operating conditions of the evaporator include: a temperature of 70-80°C (for example, any two values ​​from 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, and 80°C, or values ​​within that range), and a pressure of -0.15 MPaG to -0.01 MPaG, preferably -0.1 MPaG to -0.05 MPaG (for example, any two values ​​from -0.1 MPaG, -0.09 MPaG, -0.08 MPaG, -0.07 MPaG, -0.06 MPaG, and -0.05 MPaG, or values ​​within that range).

[0022] In this invention, preferably, the temperature of the condensed exhaust gas is 40-60°C (for example, it can be any two values ​​formed by 40°C, 42°C, 45°C, 48°C, 50°C, 53°C, 55°C, 57°C, and 60°C, or a value within that range).

[0023] In this invention, preferably, in step (2), the alkali content in the detergent used for alkaline washing can be 3-5 wt% (for example, it can be any two values ​​formed by 3 wt%, 3.2 wt%, 3.5 wt%, 3.8 wt%, 4 wt%, 4.3 wt%, 4.5 wt%, 4.7 wt%, 5 wt%, and values ​​within that range).

[0024] In this invention, preferably, the alkali can be sodium hydroxide, more preferably, it can be a 20-35 wt% sodium hydroxide solution (for example, it can be any two values ​​formed by 20 wt%, 22 wt%, 25 wt%, 28 wt%, 30 wt%, 33 wt%, 35 wt%, and values ​​within that range).

[0025] In a preferred embodiment of the present invention, step (2) further includes: sending the alkaline washing solution after alkaline washing to the sewage treatment section by a transfer pump.

[0026] In this invention, preferably, the alkaline washing can be performed using a device commonly used in the art, such as an alkaline washing tank.

[0027] In this invention, preferably, the working conditions for alkaline washing include: a temperature of 40-60°C (for example, a range formed by any two values ​​among 40°C, 45°C, 50°C, 55°C, and 60°C, and values ​​within that range), and a pressure of -1 kPaG to 3 kPaG (for example, a range formed by any two values ​​among -1 kPaG, -0.5 kPaG, 0 kPaG, 0.5 kPaG, 1 kPaG, 1.5 kPaG, 2 kPaG, 2.5 kPaG, and 3 kPaG, and values ​​within that range).

[0028] In this invention, preferably, relative to 1m 3 The amount of detergent used in the condensate is 0.1-1L, more preferably 0.2-0.5L (for example, it can be any two values ​​formed by 0.2L, 0.3L, 0.4L, 0.5L, or values ​​within that range).

[0029] It is understood that in this invention, the detergent is an aqueous solution of alkali, and the alkali washing solution is a mixed solution after alkali washing.

[0030] In this invention, preferably, in step (3), the second washing conditions include: a temperature of 40-50°C (for example, it can be any two values ​​from 40°C, 42°C, 45°C, 48°C, 50°C, or any value within that range), and a pressure of 2-5 kPaG (for example, it can be any two values ​​from 2 kPaG, 2.2 kPaG, 2.5 kPaG, 2.8 kPaG, 3 kPaG, 3.3 kPaG, 3.5 kPaG, 3.7 kPaG, 4 kPaG, 4.3 kPaG, 4.5 kPaG, 4.8 kPaG, 5 kPaG, or any value within that range).

[0031] In this invention, preferably, relative to 1m 3 The waste gas requires 5-10L of water for the second washing (for example, it can be any two values ​​from 5L, 6L, 7L, 8L, 9L, 10L, or any value within that range).

[0032] In this invention, preferably, in step (4), the adsorbent used for adsorption can be activated carbon.

[0033] In this invention, preferably, the adsorption can be performed using a device commonly used in the art, such as an adsorption tank.

[0034] In this invention, preferably, the term relative to 1m 3For the waste gas, the amount of adsorbent used is 2-5 mg (for example, it can be any two values ​​formed by 2 mg, 2.2 mg, 2.5 mg, 2.8 mg, 3 mg, 3.3 mg, 3.5 mg, 3.7 mg, 4 mg, 4.3 mg, 4.5 mg, 4.8 mg, 5 mg, or values ​​within the range).

[0035] In this invention, preferably, the activated carbon has an average particle size of 3-5 mm (for example, it can be any two values ​​formed by 3 mm, 3.5 mm, 4 mm, 4.5 mm, and 5 mm, or a value within that range), and an iodine value of 800-1000 (for example, it can be any two values ​​formed by 800, 820, 850, 880, 900, 930, 950, 970, and 1000, or a value within that range).

[0036] In a preferred embodiment of the present invention, the treatment method after the adsorption is completed further includes: contacting the adsorbed waste gas with ozone.

[0037] In this invention, preferably, the ozone can be prepared using an ozone generator and injected into a pipeline to contact the adsorbed waste gas.

[0038] In this invention, preferably, the term relative to 1m 3 For the exhaust gas, the ozone dosage is 20-60mg; (for example, it can be any two values ​​from 20mg, 22mg, 25mg, 28mg, 30mg, 33mg, 35mg, 37mg, 40mg, 43mg, 45mg, 48mg, 50mg, 52mg, 55mg, 57mg, 60mg to form a range and values ​​within that range).

[0039] In a preferred embodiment of the present invention, the process of generating waste gas from cellulose via acid vapor explosion includes: mixing cellulose with acid and then performing closed steam cooking, and releasing the waste gas after the steam cooking is completed.

[0040] In this invention, preferably, the composition of the exhaust gas includes: pentanal content of 10-15 mg / m³. 3 The content of 2-methylbutyraldehyde is 2-10 mg / m³. 3 The furfural content is 1500-2500 mg / m³. 3 The content of 5-hydroxymethyl-2-furfural is 4-8 mg / m³. 3 The total hydrocarbon content is 2020 mg / m³. 3 The hydrogen sulfide content is 1-6 mg / m³ 3 The carbonyl sulfide content is 0.01-1 mg / m³. 3 The content of methanethiol is 1-8 mg / m³. 3 Ethyl mercaptan content is 0.01-1 mg / m³3 The content of dimethyl sulfide is 0.5-5 mg / m³. 3 The content of propyl sulfide is 0.05-0.5 mg / m³. 3 Thiophene content is 0.05-0.5 L / m 3 The content of dimethyl disulfide is 1-15 mg / m³ 3 The carbon disulfide content is 0.01-0.2 mg / m³. 3 .

[0041] A second aspect of the present invention provides the application of the above-described processing method in the process of preparing ethanol from cellulose.

[0042] The present invention will be described in detail below through examples. In the following examples, the activated carbon is a commercially available product of Zhejiang Jizhu Biotechnology Co., Ltd., brand name JZ40.

[0043] "Non-methane total hydrocarbons" refers to the total gaseous organic matter remaining after deducting methane from the total hydrocarbon measurement results. These organic compounds mainly include alkanes, alkenes, aromatic hydrocarbons, and oxygen-containing hydrocarbons.

[0044] Examples 1-3

[0045] The waste gas generated by the acid vapor explosion of cellulose is added to a scrubber for the first washing using circulating water. The washed waste gas is then sent to an evaporator for heat exchange and recovery. The condensate from the heat exchange enters a condensate collection tank for discharge. The uncondensed waste gas from the heat exchange undergoes a second condensation in a cooler. The remaining non-condensable waste gas then undergoes alkaline washing in an alkaline washing tank. The alkaline-washed waste gas is then sent from the top of the alkaline washing tank to a scrubbing tower for a second washing. The waste gas after the second washing enters a centrifugal demister to remove free water, and then is sent to an activated carbon adsorption tank. Ozone is then introduced into the discharge pipeline through an ozone generator, and the finally treated waste gas is discharged in compliance with standards. Specific parameters are shown in Tables 1 and 2. Figure 1 The process flow diagrams are for Examples 1-3.

[0046] Table 1

[0047]

[0048]

[0049] Example 4

[0050] The treatment method is the same as in Example 3, except that the pressure of the washing tower is changed to 1 kPaG during the second washing. With the exhaust gas treatment capacity of the system in Example 3 being 100%, the exhaust gas treatment capacity of the system in Example 4 is reduced by 30% compared to Example 3.

[0051] Example 5

[0052] The processing method is the same as in Example 3, except that the relative water consumption of the washer during the first wash is 0.05 L / m. 3 With the exhaust gas treatment capacity of the system in Example 3 being 100%, the exhaust gas treatment capacity of the system in Example 5 was reduced by 10% compared to Example 3.

[0053] Example 6

[0054] The treatment method is the same as in Example 3, except that the pressure of the scrubbing tower is changed to 10 kPaG. The waste gas treatment capacity of the system in Example 6 is increased by 50% compared to Example 3.

[0055] Comparative Example 1

[0056] The treatment method in Example 3 differs from that in Example 3, the exhaust gas, after being condensed by the cooler, passes through a tower scrubber, a centrifugal demister, and an activated carbon intake tank, followed by alkaline scrubbing in an alkaline scrubbing tank. Finally, ozone is introduced into the emission pipeline via an ozone generator. Within two months, the exhaust gas treatment capacity of the system in Comparative Example 1 decreased by 20%.

[0057] Comparative Example 2

[0058] The existing process for treating waste steam from corn-based ethanol production is as follows: Waste heat steam is washed in a scrubbing tower, and the washed waste steam enters an evaporator for heat exchange and energy recovery. The waste gas after passing through the evaporator is discharged by a fan. The condition parameters of the scrubbing tower are the same as those of the scrubbing tower in Example 3; the condition parameters of the evaporator are also the same as those of the evaporator in Example 3.

[0059] When using the above-mentioned process technology to remove the waste gas generated by acid vapor explosion of cellulose, the emission standards cannot be met.

[0060] Comparative Example 3

[0061] The treatment method is the same as in Example 3, except that the temperature of the second washing tower is changed to 60°C. This reduces the activated carbon usage cycle by 25% compared to Example 3.

[0062] Test case

[0063] The concentrations of exhaust gas before and after treatment were analyzed using a combination of liquid chromatography and ion chromatography.

[0064] The emission concentrations of various substances in the treated exhaust gas of the examples and comparative examples were tested using the above methods, and the specific information is shown in Tables 3 and 4.

[0065] Table 3

[0066]

[0067]

[0068]

[0069] Table 4

[0070]

[0071]

[0072] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for treating waste gas generated from the acid explosion of cellulose, characterized in that, The method includes: (1) The exhaust gas is washed with water for the first time, and the temperature of the first wash is 90-100℃; (2) The exhaust gas after the first washing is condensed and then subjected to alkaline washing; wherein the alkaline content of the detergent used in the alkaline washing is 2-6 wt%, and the alkaline is an inorganic alkali; (3) The waste gas after alkaline washing is washed a second time with water. The temperature of the second washing is 50-60℃ lower than that of the first washing. (4) The exhaust gas after the second washing is adsorbed by activated carbon after passing through the demister.

2. The processing method according to claim 1, wherein, In step (1), the conditions for the first wash include: a temperature of 95-100℃, a pressure of -100PaG to -50PaG, and a washing time of 5-30s; Preferably, relative to 1m 3 For the exhaust gas, the water consumption for the first washing is 0.2-1L, preferably 0.3-0.6L.

3. The processing method according to claim 1 or 2, wherein, The method further includes: sending the waste gas and wastewater generated after the first washing into an evaporator for energy recovery, and then condensing it; Preferably, the operating conditions of the evaporator include: a temperature of 70-80°C and a pressure of -0.15 MPaG to -0.01 MPaG, more preferably -0.1 MPaG to -0.05 MPaG.

4. The processing method according to claim 1, wherein, In step (1), the temperature of the exhaust gas after condensation is 40-60℃.

5. The processing method according to claim 1, wherein, In step (2), the alkali content in the detergent used for alkaline washing is 3-5 wt%. Preferably, the alkali is sodium hydroxide, more preferably a 20-35 wt% sodium hydroxide solution.

6. The processing method according to claim 1 or 5, wherein, In step (2), the treatment method further includes: sending the alkaline washing solution after alkaline washing to the sewage treatment section by a transfer pump; Preferably, the working conditions for the alkaline washing include: a temperature of 40-60°C and a pressure of -1 kPaG to 3 kPaG; Preferably, relative to 1m 3 The amount of detergent used in the condensate is 0.1-1L, more preferably 0.2-0.5L.

7. The processing method according to claim 1, wherein, In step (3), the conditions for the second washing include: a temperature of 40-50°C and a pressure of 2-5 kPaG; Preferably, relative to 1m 3 The waste gas requires 5-10L of water for the second washing.

8. The processing method according to claim 1, wherein, In step (4), the adsorbent used for adsorption is activated carbon; Preferably, the relative to 1m 3 For the waste gas, the amount of adsorbent used is 2-5 mg; Preferably, the activated carbon has an average particle size of 3-5 mm and an iodine value of 800-1000; Preferably, the treatment method after adsorption further includes: contacting the adsorbed waste gas with ozone; Preferably, the relative to 1m 3 For the exhaust gas, the ozone dosage is 20-60mg.

9. The processing method according to claim 1, wherein, The process of generating waste gas from cellulose via acid vapor explosion includes: mixing cellulose with acid and then performing closed steam cooking, and releasing waste gas after the steam cooking is completed. Preferably, the exhaust gas composition includes: pentanal content of 10-15 mg / m³. 3 The content of 2-methylbutyraldehyde is 2-10 mg / m³. 3 The furfural content is 1500-2500 mg / m³. 3 The content of 5-hydroxymethyl-2-furfural is 4-8 mg / m³. 3 The total hydrocarbon content is 2020 mg / m³. 3 The hydrogen sulfide content is 1-6 mg / m³ 3 The carbonyl sulfide content is 0.01-1 mg / m³. 3 The content of methanethiol is 1-8 mg / m³. 3 Ethyl mercaptan content is 0.01-1 mg / m³ 3 The content of dimethyl sulfide is 0.5-5 mg / m³. 3 The content of propyl sulfide is 0.05-0.5 mg / m³. 3 Thiophene content is 0.05-0.5 L / m 3 The content of dimethyl disulfide is 1-15 mg / m³ 3 The carbon disulfide content is 0.01-0.2 mg / m³. 3 .

10. The application of the processing method according to any one of claims 1-9 in the process of cellulose to ethanol.

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