Breve discussão sobre descarte zero de águas residuais na indústria química de carvão

1. National Environmental Protection Requirements for the Coal Chemical Industry:

(1)Zero or Standardized Wastewater Discharge: The National Energy Administration has proposed, in relevant guidance, the implementation of zero wastewater discharge requirements across the industry. This means that wastewater generated during production must not be discharged or recycled through process optimization, enhanced treatment facilities, and the adoption of advanced water-saving and wastewater recovery technologies.

Coal chemical projects must conduct water resource assessments and adhere to the principle of “water conservation.” Domestic, agricultural, and ecological water use must not be compromised, and the use of groundwater is strictly prohibited.

(2)Waste Gas Emission Control: Strict national standards for air pollutant emissions from coal chemical enterprises will be implemented, including but not limited to emission limits for sulfur dioxide (SO₂), nitrogen oxides (NOx), particulate matter (PM), and volatile organic compounds (VOCs). Desulfurization, denitrification, and dust removal treatments will also be required. Emission management of greenhouse gases (such as carbon dioxide (CO₂)) will be strengthened, and the application of carbon capture, utilization, and storage (CCUS) technology will be encouraged.

(3) Solid Waste Treatment and Resource Utilization: Coal chemical solid waste must be properly disposed of in accordance with laws and regulations. We encourage the separate collection, reduction, and resource utilization of waste to reduce landfill volume. For example, coke slag from coking and spent catalysts from coal liquefaction processes should have dedicated treatment and utilization plans.

(4)Environmental Impact Assessment and Site Selection: New construction and renovation and expansion of modern coal chemical projects must strictly comply with the “Regulations on Environmental Protection Management of Construction Projects,” obtain environmental impact assessment approval, and comply with regional development plans and environmental protection policies. Site selection should avoid sensitive ecological areas to ensure the safety of the surrounding environment, and environmental factors should be fully considered during the design phase.

(5)Energy Efficiency and Circular Economy: Promote the coal chemical industry’s transition to a green and low-carbon economy, improve energy efficiency, and reduce energy consumption per unit of product. We encourage the integration and coupling of industrial chains, develop a circular economy, and transform byproducts and waste into valuable resources.

(6)Monitoring and Supervision: Establish a comprehensive online monitoring system to monitor the emission of various pollutants in real time and ensure compliance with emission standards. Regulatory authorities will conduct random inspections and checks from time to time, severely punishing violations and irregularities to ensure the effective implementation of various environmental protection policies.

In short, the national environmental protection requirements for the coal chemical industry reflect the concept of sustainable development, emphasizing the integration of source emission reduction, full-process control, and end-of-pipe treatment to achieve a harmonious balance between the economic benefits of the coal chemical industry and ecological and environmental protection. With the continuous advancement of technology and policies, these environmental protection requirements will also be enhanced and refined.

2.Zero wastewater discharge in the coal chemical industry generally includes the following:

The zero wastewater discharge standard for the coal chemical industry means that after treatment, wastewater generated during the production process does not release any liquid waste into the environment. Instead, all substances in the wastewater are converted, recycled, or solidified into valuable resources or products, achieving the goal of “zero waste liquid discharge.” This concept emphasizes minimizing environmental impact and increasing the recycling rate of water resources.

(1)Wastewater reuse rate: This requires that treated wastewater can be fully reused, achieving a 100% reuse rate, with no wastewater discharged into the external environment.

(2)Pollutant concentration: Various pollutants in the wastewater, such as organic matter, inorganic salts, and heavy metals, must be below specified concentration limits to ensure that the treated water meets environmental requirements.

(3)Solid waste treatment: Solid waste generated during the treatment process must be properly handled to avoid secondary pollution.

(4)Treatment process and equipment: The treatment process and equipment used must comply with relevant standards and requirements to ensure treatment effectiveness and operational stability.

(5)Monitoring and Management: Companies need to establish a comprehensive monitoring system to monitor and manage the wastewater treatment process in real time to ensure compliance with discharge standards.

However, in practice, achieving complete zero wastewater discharge is often difficult. Therefore, the “zero discharge” generally accepted within the industry is a relative concept, meaning to approach zero discharge as close as possible to reduce environmental pollution risks and improve resource utilization. China and internationally have detailed regulations and technical specifications for zero wastewater discharge standards for specific industries. Companies must strictly comply with relevant laws and regulations and develop and implement scientifically sound wastewater treatment plans to meet regulatory requirements.

3. Upstream and Downstream Links of the Coal Chemical Industry Chain:

Upstream: Coal Mining and Washing: This is the foundation of the coal chemical industry. Raw coal is obtained through mining and then washed to remove impurities, improving coal utilization efficiency and product quality. Coal Transportation and Storage: Mined coal is transported to chemical plants by rail, road, or water. Supporting storage facilities are required to ensure a stable supply of raw materials.

Midstream:

(1)Basic Coal Chemical Industry:

Coal Coking: Coal is subjected to high-temperature dry distillation to produce coke. Byproducts include coke oven gas, crude benzene, and coal tar. Coke is primarily used in steelmaking, while coke oven gas and other byproducts can be further processed into chemicals.

Coal Gasification: Coal is converted into synthesis gas (primarily composed of CO and H2). Synthesis gas is a feedstock for a variety of chemical products, such as synthetic ammonia, methanol, and dimethyl ether.

Coal Liquefaction: Coal is converted into liquid fuels such as gasoline, diesel, and jet fuel through direct or indirect liquefaction technologies.

(2)Fine Coal Chemicals:

Coal-to-olefins: For example, the methanol-to-olefins (MTO/MTP) process is used to produce basic organic chemical raw materials such as ethylene and propylene.

Coal-to-ethylene glycol: Ethylene glycol is produced from synthesis gas, which is used as the primary raw material for polyester fiber production.

Coal-to-natural gas (SNG): Coal is gasified to synthesize natural gas for energy use or pipeline transportation.

Coal-to-aromatics: Aromatic hydrocarbons such as benzene, toluene, and xylene are produced through chemical reactions using coal as a raw material.

PVC by calcium carbide: Calcium carbide (CaC₂) produced by coal pyrolysis is used to synthesize vinyl chloride monomer (VCM), which is then used to produce polyvinyl chloride (PVC).

Downstream:

Chemical Product Processing: Starting from coal chemical intermediates, various chemical products such as plastics, rubber, fibers, coatings, solvents, pharmaceutical intermediates, fertilizers, and various fine chemicals are produced through a series of chemical reactions and physical processes. Energy Products: Coal chemical production produces petroleum substitutes such as gasoline, diesel, and liquefied petroleum gas, which can be used as transportation fuels. Other energy products include electricity and steam. Some large-scale coal chemical projects are equipped with their own power plants.

Overall, the coal chemical industry chain spans the entire process of coal resource conversion, value-added, and end-use applications, aiming to improve the comprehensive utilization and economic benefits of coal resources while minimizing environmental impact. With technological advancements, modern coal chemical production is placing a greater emphasis on clean, efficient, and environmentally friendly development.

4. Coal Chemical Industry Segments with Significant Environmental Impacts:

(1)Coal Mining: Coal mining can lead to ecological problems such as surface subsidence, groundwater level decline, soil damage, and biodiversity loss. Furthermore, open-pit mining produces large amounts of waste rock and mine water, which, if not properly handled, can cause environmental pollution.

(2)Coal Washing and Transportation: The coal washing process generates wastewater and coal slime, which require proper treatment. Dust pollution during coal transportation is also a significant environmental issue, especially along railway and road routes and at ports and terminals.

(3)Coal Gasification and Syngas Purification: The gas produced by coal gasification contains sulfides, nitrogen oxides, and other harmful substances. Direct discharge without desulfurization and denitrification treatment can seriously pollute the atmosphere. The wastewater generated by coal gas washing is large in volume and complex in composition, containing a variety of toxic and harmful substances such as phenols, ammonia nitrogen, and cyanide, making it one of the major sources of wastewater in the coal chemical industry.

(4)Coking Process: The coking process produces large amounts of coke oven gas, coal tar, and wastewater containing pollutants such as phenols, cyanide, ammonia, and sulfides, as well as solid waste such as coke slag. If coke oven flue gas is not effectively treated, the sulfur dioxide, nitrogen oxides, and particulate matter emitted can seriously impact air quality.

(5)Coal Liquefaction and Deep Conversion: Direct and indirect coal liquefaction processes also produce significant amounts of the greenhouse gas carbon dioxide, with direct liquefaction, in particular, producing higher CO₂ emissions. These processes also generate wastewater and waste slag, requiring stringent treatment measures to mitigate their environmental impact.

(6)Energy Consumption and Water Utilization: Coal chemical industry is energy- and water-intensive, using significant amounts of water and generating large amounts of warm wastewater. Without the implementation of cooling cycles and water-saving technologies, this can place significant pressure on water resources and potentially cause thermal pollution. To sum up, the coal chemical industry has environmental pollution risks to varying degrees in multiple links, from upstream mining to midstream processing and conversion to downstream product manufacturing. While developing coal chemical industry, it is necessary to strengthen the research and development and application of environmental protection technologies, strictly implement clean production and circular economy models, and ensure that ecological environmental protection is coordinated with industrial development.

5.Coal Chemical Wastewater Treatment Processes and Steps:

(1)Pretreatment Stage: Oil Separation: Removes floating oil from wastewater through gravity separation. Air Flotation: Uses tiny bubbles to absorb suspended solids and emulsified oil to the surface for easy removal. Filtration/Screening: Initially removes large solid particles and some suspended solids from wastewater. Phenol Removal and Ammonia Distillation: Targeted treatment of wastewater containing high concentrations of phenols and ammonia nitrogen.

(2)Biochemical Treatment Stage: A/O (Anaerobic-Oxic) Process: An anoxic-aerobic biological treatment system primarily used to degrade organic matter and ammonia nitrogen. The A/A/O (Anaerobic-Anoxic-Oxic) process: Adds anaerobic and anoxic zones to further improve nitrogen and phosphorus removal efficiency. CBR (Carrousel Bio Reactor) and SBR (Sequencing Batch Reactor): Circulating activated sludge processes and sequencing batch activated sludge processes, respectively, are suitable for treating wastewater with large load fluctuations. UASB (Upflow Anaerobic Sludge Blanket) Process: An upflow anaerobic sludge blanket reactor designed for efficient degradation of high-concentration organic wastewater.

(3)Advanced Treatment Stage: Coagulation and Sedimentation: Coagulants are added to flocculate and precipitate colloidal substances in the water. Filtration: Sand filtration, activated carbon filtration, and other methods are used to further purify the water. Ion Exchange Technology: Selectively removes specific ionic contaminants through adsorption. High-efficiency Reverse Osmosis (RO) and Nanofiltration (NF): Membrane separation technologies are used to deeply desalinate and concentrate wastewater. Ozone oxidation, electrochemical oxidation, and Advanced Oxidation Processes (AOPs): These technologies are used to degrade recalcitrant organic matter and other hazardous substances.

(4)Evaporation, Crystallization, and Drying: In pursuit of zero-emission wastewater, technologies such as multi-effect evaporation, mechanical vapor recompression (MVR), and freeze crystallization may be used to convert wastewater into solid waste, thereby achieving zero liquid discharge. These processes are often flexibly combined based on the specific wastewater quality characteristics and discharge requirements to ensure that the treated wastewater meets environmental regulations and maximizes resource recovery and sustainable development.

6.Major bottlenecks in zero-discharge coal chemical wastewater technology:

(1)Resource utilization of mixed salts: The amount of mixed salts formed during the treatment of gasification wastewater and industrial wastewater is large and complex, including various heavy metal ions and other harmful substances. Effectively separating and reusing these mixed salts is a major challenge.

(2)High cost and energy consumption: Achieving zero-discharge wastewater requires a multi-stage treatment process, including pretreatment, biochemical treatment, physicochemical treatment, and deep membrane separation. These processes are extremely costly to build and operate, and consume significant energy.

(3)Treatment system stability: Wastewater quality fluctuates significantly, especially gasification wastewater, which significantly impacts the treatment system. This leads to poor system operational stability and makes it difficult to achieve zero-discharge standards in the long term.

(4)Risk of secondary environmental pollution: Some treatment processes may generate byproducts such as sludge and concentrate. If not properly disposed of, these byproducts may cause secondary contamination of soil, groundwater, and other areas.

(5)Recovery Rate and Water Quality Requirements: While advanced technologies and equipment such as Neterfo extreme separation have been used to improve the recovery rate of recycled water, achieving a recovery rate exceeding 90% while ensuring that the effluent quality meets stringent reuse standards remains challenging in practice.

(6)Technological Innovation and Breakthroughs: There is an urgent need to develop new, more efficient, energy-saving, and economical wastewater treatment technologies and equipment to overcome the shortcomings of existing technologies in terms of treatment efficiency, stability, and environmental friendliness.

In summary, the key bottlenecks in achieving zero-discharge coal chemical wastewater technology lie in technological innovation and improvement in mixed salt resource utilization, cost-effective treatment processes, and ensuring stable system operation and water quality compliance.

7.Strategies for Breaking Through Zero Wastewater Discharge Technology Bottlenecks:

(1)Technological Research and Innovation: Enhance and optimize existing core technologies such as membrane separation, evaporative crystallization, electrochemical treatment, and advanced oxidation to improve their adaptability and treatment efficiency for complex wastewater compositions. Develop new, efficient, and economical technologies for the resource utilization of mixed salts to address the difficulty in effectively separating and disposing of mixed salts in high-concentration saline wastewater.

(2)Integrated Process Flow Optimization: Scientifically and rationally combine and optimize multiple processes, including pretreatment, biochemical treatment, physicochemical treatment, and advanced treatment, to create a comprehensive solution with higher recovery rates and lower energy consumption. Strengthen source control and process management, such as improving production processes to reduce the generation of toxic and hazardous substances and achieve clean production.

(3)Energy Conservation and Consumption Reduction and Circular Economy: Implement more efficient energy recovery systems, such as heat recovery and reuse technologies, to reduce energy consumption across the entire wastewater treatment system. Promote a circular economy model, reintroducing valuable substances extracted from wastewater into the production process, creating a closed-loop system.

(4)Policy Guidance and Financial Support: The government should introduce appropriate policy incentives, including subsidies and tax incentives, to encourage enterprises to develop and apply zero-wastewater discharge technologies. Innovative financial instruments should be used to guide private capital investment in green technology R&D and project implementation.

(5)International Cooperation and Exchange: Strengthen international technical cooperation and exchange, introduce advanced foreign technologies and experience, and jointly research and solve key problems. Establish a R&D platform that closely integrates industry, academia, research, and application to accelerate the industrialization of scientific and technological achievements.

(6)Strengthen Environmental Monitoring and Regulatory Enforcement: Strengthen monitoring of wastewater discharges to ensure that enterprises strictly comply with relevant environmental regulations, while promoting the development of more stringent industry standards and technical specifications. Through these multifaceted efforts, we can gradually overcome the technical bottlenecks of zero-wastewater discharge in the coal chemical industry and provide strong support for the sustainable development of the coal chemical industry in my country and globally.

8. New Technologies in Pollution Control in the Coal Chemical Industry:

(1)Advanced Oxidation Processes (AOPs): These include ozone oxidation, hydrogen peroxide/UV catalytic oxidation, and Fenton’s reagent oxidation. These technologies can effectively degrade difficult-to-biodegrade organic matter in coal chemical wastewater, particularly phenols and polycyclic aromatic hydrocarbons.

(2)Membrane Separation Technology: Membrane technologies such as reverse osmosis (RO), nanofiltration (NF), and ultrafiltration (UF) are widely used for advanced wastewater treatment, removing fine particles, salts, and other dissolved pollutants from water, achieving resource utilization and meeting discharge standards.

(3)Immobilized Biotechnology: By immobilizing dominant microorganisms, the removal efficiency of specific pollutants, such as pyridine and quinoline, is improved, while also enhancing the system’s stability and resistance to shock loads.

(4)Electrochemical Oxidation Technology: This technology utilizes hydroxyl radicals (·OH) generated by electrochemical reactions to oxidize and decompose organic matter in wastewater. It is particularly suitable for pretreatment or advanced treatment of high-concentration organic wastewater.

(5)Ionic Liquid Method: This method uses ionic liquids as extractants or solvents to extract harmful components from wastewater. This method has low vapor pressure and high solvency, which helps reduce energy consumption and environmental pollution.

(6)Combined Biochar Adsorption and Bioactivated Carbon Process: Biochar has excellent adsorption properties for heavy metals and organic pollutants in wastewater, while bioactivated carbon has both physical adsorption and biodegradation capabilities.

(7)Carbon Capture and Storage (CCS): CCS technology can separate greenhouse gas carbon dioxide emissions from the coal chemical production process and store them for long periods of time to reduce carbon emissions.

(8)Integrated Water-Saving and Zero-Discharge Technology System: This system integrates high-efficiency evaporation and crystallization, MVR (Mechanical Vapor Recompression) evaporation and concentration, and reverse osmosis technologies to achieve wastewater recycling and zero-discharge goals. The application of these new technologies not only improves the treatment of coal chemical wastewater, but also promotes the green and sustainable development of the industry to a certain extent. With the advancement of science and technology, new environmentally friendly technologies and comprehensive solutions are still under research and development.

9.The Significance of Zero Emissions in the Coal Chemical Industry:

(1)Environmental Pressure and Policy Requirements: With growing environmental awareness and the country’s emphasis on ecological civilization, the government is tightening environmental standards for various industrial production activities. Zero wastewater discharge is a key measure for achieving environmental sustainability and reducing pollutant emissions. Due to the coal chemical industry’s high water consumption, complex wastewater composition, and difficulty in treating it, direct discharge of wastewater without effective treatment will seriously pollute water resources, impacting the ecological environment and human health.

(2)Water Scarcity: Many regions in China with abundant coal resources, such as Xinjiang and Inner Mongolia, also face water scarcity. Coal chemical companies consume significant amounts of water and generate large amounts of wastewater. Achieving zero emissions can help alleviate the imbalance between water supply and demand and protect precious local water resources.

(3)Technological Advancement and Industrial Upgrading: The development of modern coal chemical technology has significantly improved wastewater treatment technologies, including high-efficiency separation, concentration, evaporation, and crystallization processes, providing technical support for achieving near-zero wastewater discharge. Achieving zero emissions will help promote the transformation and upgrading of the coal chemical industry towards a green, low-carbon, and circular economy, enhancing the industry’s competitiveness and social image.

(4)Economic Benefits: Advanced wastewater treatment and recycling can reduce fresh water usage and water bills. Furthermore, some treated wastewater materials can be sold as by-products or reused in the production process, generating economic benefits.

(5)Social Responsibility and International Trends: Globally, with the advancement of international agreements such as the United Nations Sustainable Development Goals (SDGs) and the Paris Agreement, it has become a universal consensus for companies to assume stricter environmental responsibilities. The coal chemical industry’s pursuit of zero discharge aligns with international environmental trends and helps establish a positive corporate citizenship image. Therefore, implementing zero wastewater discharge is not only a requirement for the coal chemical industry to fulfill its environmental obligations, but also an inevitable choice to ensure its own sustainable development, respond to national strategic goals, and adapt to market and societal needs.

10. Environmental Protection Equipment Required for Coal Chemical Enterprises:

(1)Waste Gas Treatment Equipment: Dust collectors (such as electrostatic precipitators and bag filters) are used to capture smoke and other particulate matter. Desulfurization equipment (such as wet desulfurization towers and dry desulfurization units) reduces sulfur dioxide emissions. Denitrification equipment (such as selective catalytic reduction (SCR) and non-selective catalytic reduction (SNCR)) controls nitrogen oxide emissions. VOC (volatile organic compound) treatment equipment, such as activated carbon adsorption units, RTO (regenerative thermal oxidizers), or catalytic combustion units.

(2)Wastewater Treatment Facilities: Chemical sedimentation tanks, biological contact oxidation tanks, A/O and A/A/O biochemical treatment systems, and MBRs (membrane bioreactors) provide primary and advanced wastewater treatment. Membrane separation technologies such as reverse osmosis (RO), nanofiltration (NF), and ultrafiltration (UF), as well as low-temperature evaporation technologies, are used for advanced wastewater purification and reuse. Advanced treatment processes specifically for coal chemical wastewater include catalytic micro-electrolysis, electrochemical oxidation, and ozone oxidation.

(3)Solid Waste Treatment and Resource Utilization Equipment:

Collection and storage facilities for solid wastes such as coke residue, ash, and spent catalysts.

Incinerators for high-temperature combustion of combustible solid waste, equipped with flue gas purification systems. Landfills must meet anti-seepage and gas collection and treatment requirements. Pre-treatment equipment for solid waste crushing, sorting, and pressing, as well as subsequent resource utilization equipment such as tar extraction and metal recovery, are required.

(4)Other Environmental Protection Facilities: Ecological restoration projects in coal mining areas, such as reclamation and land reclamation. Greenhouse gas emission reduction technologies, such as carbon dioxide capture, storage, and utilization (CCUS) facilities. Noise control equipment, including noise barriers and silencers.

(5)Online Monitoring System: Various online monitoring instruments are installed to monitor and record the emission concentrations of various pollutants in real time to ensure compliance with national and local environmental standards.

The selection of equipment and systems should be based on the specific production process, environmental regulations, and the environmental conditions of the project location, striving to achieve efficient, stable, and economically viable pollution control results.

11.Development Prospects of my country’s Coal Chemical Industry:

(1)Energy Strategy and Policy: With China’s continuous pursuit of energy structure optimization and increasing environmental protection requirements, coal’s position as a primary energy source is facing challenges. However, given China’s abundant and relatively stable coal resources, the coal chemical industry remains a key path to ensuring national energy security and achieving clean and efficient coal utilization. The national government will continue to promote the development of the coal chemical industry towards high-end, refined, green, and low-carbon development.

(2)Technological Innovation: Advances in modern coal chemical technologies, such as coal gasification, syngas conversion, coal-to-olefins, coal-to-natural gas (SNG), coal-to-liquids, and carbon capture, utilization, and storage (CCUS), are crucial for reducing environmental impact, improving energy efficiency, and increasing product value. In the future, technological innovation will be the core driving force for the sustainable development of the coal chemical industry.

(3)Market Demand: Continued global and domestic demand for petrochemical products, particularly clean energy and basic chemical raw materials, provides market space for coal chemical products. Furthermore, diversification and differentiation of coal chemical products, such as the development of high-value-added fine chemicals and new materials, are key to enhancing competitiveness.

(4)Environmental Regulations and Standards: Faced with increasingly stringent environmental regulations and emission standards, coal chemical companies must increase environmental investment and implement measures such as zero wastewater discharge, intensive waste gas treatment, and solid waste resource utilization to ensure compliance with environmental policies and secure long-term development approvals.

(5)Economic Benefits and Cost Control: The economic viability of coal chemical projects directly impacts their development prospects. Factors such as international oil price fluctuations, the payback period for new technology investments, energy efficiency, and raw material costs all influence the profitability of the coal chemical industry.

In summary, China’s coal chemical industry will, while strictly adhering to environmental policies, rely on technological innovation to achieve transformation and upgrading, moving towards a greener, more efficient, and more economical direction. However, due to increasing environmental pressures and technological barriers to entry, competition within the industry will intensify, with a clear trend of survival of the fittest. Only those companies that proactively address challenges and adapt to new changes will have a chance to gain a foothold and achieve long-term development in this new market environment.