Emissions from the chemical industry sector?
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Emissions from the chemical industry sector? Let’s talk about the industry you’re in – are there any chemical process emissions? Some smaller coking plants still emit flue gases from their coke ovens; a few oilfield processing stations continue to burn off dry gas through flares. In a few coking plants, hydrogen present in the coke oven gas is recovered, but methane is not recovered and is instead released into the atmosphere. Some chlor-alkali plants burn hydrogen in flares; let’s discuss what types of exhaust gases in our own companies still have utility but are not being recycled. It is also possible to discuss how exhaust gases were previously utilized comprehensively in one’s own company, and to share experiences in order to maximize resource utilization. Any examples of energy sources that have not been utilized that one has come across can be mentioned, in order to jointly promote the development of the industry focused on the comprehensive use of energy
To spark discussion, I have been to some oil fields where the phenomenon of sky lanterns still exists to some extent. Moreover, the dry gas volume is relatively large; it’s just in a somewhat remote location. Some way should be found to make comprehensive use of it. This post was last edited by chinazwr on 2009-3-17 20:09]
For the hydrogen peroxide production process, our exhaust gas system is equipped with specialized collection devices; within these devices, the gas and liquid are separated, and the useful solvents and other components are returned to the collection tanks for re-vaporization and reuse. Nowadays, environmental regulations are stricter, and there are also significant investments required for exhaust gas treatment. :(
Where I am, there are petrochemical plants and coking plants, and their exhaust gases are incinerated – I think this is a waste. Our facility also generates waste gases, but they are acidic in nature; we use alkaline solutions to absorb them and recover the inorganic salts, which brings certain economic benefits! ! !
The exhaust gases from our facility are discharged through catalytic chimneys, sulfur recovery chimneys, acidic gas flares, and flares. There still seems to be contamination, and it’s also very wasteful. In particular, the flare is activated as soon as the dry gas pressure rises.
That’s indeed a waste. But as far as I know, companies these days place a lot of emphasis on the reuse of waste gas. Generally, the process exhaust gases emitted by various operating units when they are functioning properly are mostly recycled. For example, the gases emitted by refining plants are used to produce hydrogen or as fuel gas, among other things. Common methods include PSA, TSA, membrane separation, etc. If the unit is in an accident condition, then the only option is to use a flare. Most plants have a dedicated gas holder in the flare system for further recovery and reuse, but when the volume is too large, it still has to be burned in a flare. So for oil refining units, if you see the flare burning brightly, it usually means there are fluctuations in production!
Flares are necessary; sometimes, the cost-benefit ratio of recycling waste gases is not favorable, so it’s better to burn them directly. After all, a company’s goal is to make a profit. Another use of flare gas is to burn those substances that are difficult to recycle or that cannot be discharged safely. Of course, the recycling of materials and thermal energy should be done in a rational manner to avoid unnecessary waste
All the exhaust gas from our facility is fully utilized. Another set of exhaust gas boilers was installed; the steam generated is used for power production, and the economic benefits are quite significant. It is both environmentally friendly and energy-efficient.
The off-gases from the ammonia synthesis step in ammonia synthesis plants contain large amounts of hydrogen. This hydrogen is recovered through membrane separation or pressure swing adsorption and returned to the ammonia synthesis system as a raw material for ammonia production, thereby reducing the consumption of synthesis gas and increasing ammonia output. The exhaust gas after membrane recovery or pressure swing adsorption still contains small amounts of hydrogen and methane, which are sent to boilers for combustion in order to save fuel consumption.
Our company is a chemical enterprise with a large volume of exhaust gas. To save energy and protect the environment, a complete exhaust gas power generation system was installed. Apart from being used for our own company’s needs and supplied to nearby companies, the rest is all fed into the internet. Waste gas power generation is an energy-saving and environmentally friendly project; small units can also be used for this purpose, **and it is supported as well. The economic benefits are quite substantial.
In our company, carbon dioxide is the main pollutant emitted; it contributes to the greenhouse effect and wastes resources. If it were possible to recycle all of it into fertilizers, which can then be used by green plants to absorb nutrients, it would be a great benefit for both the country and its people.
Our company is a manufacturer of active pharmaceutical ingredients. The local authorities enforce strict regulations on waste management; environmental protection officials frequently come to the factory to monitor air quality. As for wastewater, there are sensors that are connected directly to the environmental protection agency, enabling 24/7 monitoring. The pressure related to environmental protection is very high, and the associated costs are substantial!
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Everything in our company has been put to use; for example, wet acid exhaust gases are used to produce sodium fluosilicate, sulfuric acid exhaust gases are used to produce ammonium sulfate, and the exhaust gases from the calcium salt system are neutralized with sodium salts to serve as raw materials for chemical defluorination. In essence, a fully closed-loop system has been achieved.
Our company is a sulfuric acid manufacturer; when it was designed, the SO2 concentration was set at 300 PPM, with a requirement of 420 PPM. However, due to issues such as catalyst poisoning and loss of effectiveness, current tests show a concentration of around 560 PPM. May I ask how you handle sulfuric acid exhaust gas upstairs? Directly into ammonia water?
The recovery of carbon dioxide is an inevitable trend these days, and that’s exactly what our company does. We deal with liquid carbon dioxide, with the raw gas having a purity of 85%, and the energy consumption per ton is 185 kWh
Discharge and treatment of the three types of waste from the ammonium phosphate plant: The plant’s production capacity of 300,000 tons per year of sulfuric acid and 200,000 tons per year of ammonium phosphate was designed by Yunnan Chemical Engineering Design Institute Co., Ltd., with ChenGuang Engineering Design Institute taking overall responsibility for the construction. The discharge and treatment of the three types of waste in this project are as follows: I. Wastewater Generation and treatment of domestic wastewater: Domestic wastewater includes that generated in the area in front of the factory and in various plant areas. The discharge volume is 3.2 m³/h, with a maximum of 8 m³/h. The factory is equipped with a domestic wastewater treatment station with a processing capacity of 10 m³/h. The treated water is disinfected using ultraviolet light before being reused for landscaping and road irrigation. 2. The generation of wastewater is shown in the table below: Sequence Number, Device generating wastewater, Unit, Quantity, Destination, Remarks; 1, Sulfur melting section, m³/h, 3.5, Production wastewater treatment plant; 2, Floor washing water, m³/h, 5, Production wastewater treatment plant; 3, Ammonium phosphate circulating water station, m³/h, 5, Production wastewater treatment plant; 4, Laboratory and unforeseen water sources, m³/h, 10, Production wastewater treatment plant; 5, Water returned from the slag yard, m³/h, 20, Production wastewater treatment plant. Total, m³/h, 43.5. The production wastewater treatment plant has a designed processing capacity of 60 m³/h, and the treated water is reused in the phosphate production section – 12 m³/h is reused by the grinding devices, and 31.5 m³/h is reused by the phosphate extraction devices. Implement separate systems for rainwater and sewage. The entire plant implements a separation system for rainwater and wastewater. The specific measures involve collecting rainwater from various units and tank areas into rainwater tanks 15 minutes before it starts to rain, and then using wastewater pumps to transport this water to the wastewater treatment station for processing ； After 15 minutes, or in the case of heavy rain, the water is drained into the stormwater drainage system. An accident tank is installed to temporarily store waste liquids discharged in case of accidents, maintenance, or other special situations. 4. The discharge amounts of treated wastewater are shown in the table below:
Serial Number | Waste Water Generating Unit | Unit | Quantity | Remarks
1 | Steam system | m³/h | 1 |
2 | Desalination station | m³/h | 3.8 |
3 | Thermal power plant | m³/h | 5 |
4 | Sulfuric acid circulating water station | m³/h | 20 |
Total | m³/h | 29.8 |
Exhaust gases:
1. The generation and discharge of exhaust gases are detailed in the table below:
Serial Number | Exhaust Gas Generating Unit | Pollutant | Exhaust Gas Volume (Nm³/h) | Emission Concentration (mg/Nm³) | Hourly Emission Amount (kg/h) | Annual Emission Amount (t/a) | Standard Limit (mg/Nm³) | Approval from Environmental Assessment (t/a)
1 | Sulfuric acid exhaust gas | SO2 | 66,056 | 352 | 23.2 | 185.6 | 400 | 262.264 |
2 | Sulfuric acid exhaust gas | Acid mist (SO3) | 20 | 1.32 | 10.13 | 12.203 | | |
3 | Phosphoric acid and ammonium phosphate exhaust gas | F | 56,000 | 5 | 0.28 | 2.01 | 9 | 12.16 | |
2. Exhaust gas treatment measures:
For sulfuric acid exhaust gas, treatment is carried out using approximately 3% ammonia water; the resulting sulfuric acid is reused in the phosphamic acid production process. After washing, the SO2 concentration in the exhaust gas is around 352 mg/Nm³, and that of acid mist is around 20 mg/Nm³. These exhaust gases are then discharged through an 80-meter tall chimney in compliance with regulatory standards. Treatment of F-containing exhaust gas: The exhaust gas from the extraction section is first washed in a Venturi scrubber, then sent to the first fluorine scrubber for a second wash. It is subsequently combined with F-containing steam from the filtration section; after gas-liquid separation, this mixture is sent to the second fluorine scrubber for further washing. The exhaust gas after treatment meets the emission standards ； The washing water uses a counter-current circulation washing method, and any shortage is made up by treated wastewater. III. Waste Residues 1. The generation of waste residues is shown in the table below: Sequence Number, Device that generates waste residues, Name of waste residue, Unit, Quantity, Destination. 1. Liquid sulfur filtration – Sulfur residue, t/a: 398; Sent for recovery by acid production plants. 2. Conversion unit – Vanadium-containing catalyst, t/a: 15; Recovered by domestic catalyst manufacturers. 3. Phosphoric acid filtration – Phosphogypsum (containing 525% H2O), 10,000 t/a: 70; Stored in a waste residue storage area. 2. Conditions of the waste residue storage area: Strict anti-seepage measures are implemented at the phosphogypsum storage area, and sewage collection tanks are installed to send the sewage back to the sewage treatment plant for further processing before it can be reused.
Serial Number | Waste Water Generating Unit | Unit | Quantity | Remarks
1 | Steam system | m³/h | 1 |
2 | Desalination station | m³/h | 3.8 |
3 | Thermal power plant | m³/h | 5 |
4 | Sulfuric acid circulating water station | m³/h | 20 |
Total | m³/h | 29.8 |
Exhaust gases:
1. The generation and discharge of exhaust gases are detailed in the table below:
Serial Number | Exhaust Gas Generating Unit | Pollutant | Exhaust Gas Volume (Nm³/h) | Emission Concentration (mg/Nm³) | Hourly Emission Amount (kg/h) | Annual Emission Amount (t/a) | Standard Limit (mg/Nm³) | Approval from Environmental Assessment (t/a)
1 | Sulfuric acid exhaust gas | SO2 | 66,056 | 352 | 23.2 | 185.6 | 400 | 262.264 |
2 | Sulfuric acid exhaust gas | Acid mist (SO3) | 20 | 1.32 | 10.13 | 12.203 | | |
3 | Phosphoric acid and ammonium phosphate exhaust gas | F | 56,000 | 5 | 0.28 | 2.01 | 9 | 12.16 | |
2. Exhaust gas treatment measures:
For sulfuric acid exhaust gas, treatment is carried out using approximately 3% ammonia water; the resulting sulfuric acid is reused in the phosphamic acid production process. After washing, the SO2 concentration in the exhaust gas is around 352 mg/Nm³, and that of acid mist is around 20 mg/Nm³. These exhaust gases are then discharged through an 80-meter tall chimney in compliance with regulatory standards. Treatment of F-containing exhaust gas: The exhaust gas from the extraction section is first washed in a Venturi scrubber, then sent to the first fluorine scrubber for a second wash. It is subsequently combined with F-containing steam from the filtration section; after gas-liquid separation, this mixture is sent to the second fluorine scrubber for further washing. The exhaust gas after treatment meets the emission standards ； The washing water uses a counter-current circulation washing method, and any shortage is made up by treated wastewater. III. Waste Residues 1. The generation of waste residues is shown in the table below: Sequence Number, Device that generates waste residues, Name of waste residue, Unit, Quantity, Destination. 1. Liquid sulfur filtration – Sulfur residue, t/a: 398; Sent for recovery by acid production plants. 2. Conversion unit – Vanadium-containing catalyst, t/a: 15; Recovered by domestic catalyst manufacturers. 3. Phosphoric acid filtration – Phosphogypsum (containing 525% H2O), 10,000 t/a: 70; Stored in a waste residue storage area. 2. Conditions of the waste residue storage area: Strict anti-seepage measures are implemented at the phosphogypsum storage area, and sewage collection tanks are installed to send the sewage back to the sewage treatment plant for further processing before it can be reused.