1. CO 2 Plants Environmental Issues TP N° 18/09 EUROPEAN INDUSTRIAL GASES ASSOCIATION AISBL AVENUE DES ARTS 3 – 5 B-1210 BRUSSELS PHONE +32 2 217 70 98 FAX +32 2 219 85 14 - E-mail: info@eiga.eu - www.eiga.eu EIGA 2009 - EIGA grants permission to reproduce this publication provided the Association is acknowledged as the source
2. DISCLAIMER All technical publications of EIGA or under EIGA’s name, including Codes of practice, Safety procedures and any other technical information contained in such publications were obtained from sources believed to be reliable and are based on technical information and experience currently available from members of EIGA and others at the date of their issuance. While EIGA recommends reference to or use of its publications by its members, such reference to or use of EIGA’s publications by its members or third parties are purely voluntary and not binding. Therefore, EIGA or its members make no guarantee of the results and assume no liability or responsibility in connection with the reference to or use of information or suggestions contained in EIGA’s publications. EIGA has no control whatsoever as regards, performance or non performance, misinterpretation, proper or improper use of any information or suggestions contained in EIGA’s publications by any person or entity (including EIGA members) and EIGA expressly disclaims any liability in connection thereto. EIGA’s publications are subject to periodic review and users are cautioned to obtain the latest edition. EUROPEAN INDUSTRIAL GASES ASSOCIATION AISBL AVENUE DES ARTS 3 – 5 - B-1210 BRUSSELS PHONE +32 2 217 70 98 - FAX + 32 2 219 85 14 - E-mail : info@eiga.eu - www.eiga.eu
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5. Environmental Impact of Carbon Dioxide Plants Blowers Compressors Scrubbers Dryers Adsorbers Purification Refrigeration Storage and Distribution Noise x Oil o Noise x Oil o Chemicals o Noise x Cooling water x Chemicals o Noise p Absorbent o Product o Chemicals x Chemicals o Noise p Absorbent o Air emissions p Air Emissions x Noise x Refigerant o Oil o Insulation o Raw gas Consumables energy Consumables energy Consumables Chemicals water Consumables energy Consumables Consumables Chemicals Refrigerant INPUTS OUTPUTS Persistent x Periodic p Occasional or accidental o Consumables Consumables
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Editor's Notes
Use this slide to get the audience to understand the use of the concept environmental impact and why it is important and how it can be used to find the most significant impacts within the gases industry. Environmental Impact Understanding what is an environmental impact is very important as it helps us understand how we may be able to reduce the impact. Impacts may be defined as any change to the environment, whether adverse or beneficial, wholly or partially resulting from an organization’s activities, products or services. For example: the contamination of water with hazardous substances or the reduction of air emissions. The use of a product that minimises environmental impact e.g. using a chemical that has no global warming impact The next few slides we are going to explain some of the impacts the gases industry has on the environment and how we may be able to reduce some of these impacts and make a positive contribution to the environment.
Trainers note- describe the process inputs and outputs as shown on the screen. Where sites have an environmental licence use this to talk througjh the impacts, monitoring checks etc Typically CO 2 recovery Plant process consists of the following key stages: Raw gas blowing (some times not needed if raw gas pressure is enough) Cooling and water scrubbing (some cases after compression) Compression stages within cooling and liquid separation (for CO 2 and for Refrigerants) Cooling transfer stages (with water and CO 2 ) Drying (Alumina typically) Purification with adsorbers for filtering (Activated carbon typically) Liquefaction by cooling transfer stages (with refrigerant) and reboiler Distillation by Stripping and subcooling Storage Loading for Distribution On the next slide we will summarise the main environmental impacts
Introduction For generating CO 2 there are different ways or sources (production of am m onia, steam methane reformers, ethylene oxide, combustion of oil and gas, etc.), here we analyze the influence of the common part of CO 2 Plants, the one of the recovery Plant from a raw gas source, with small differences between processes. Each stage has it’s own potential for environmental impact and additionally there are associated issues to consider such as storage of materials. The items which will be addressed in this session are listed on the slide. In each case the potential environmental impact is discussed together with good practice where appropriate.
The main air emissions result from any of the CO 2 recovery Plants processes are the proper CO 2 leaks and vents, the continuous venting of non condensable purge in the stripper and the possible emissions of refrigerants such as ammonia or HCFC used for refrigerating the CO 2 flow among the process. Running the Plant at the design operation conditions those emissions will be minimised. Good practice includes: Refrigerants: Leaks from valves & fittings minimized using best available techniques. Check purchases to confirm performance. Recover and recycle during maintenance. Consider alternative refrigerants with less environmental impact. Ensure the new refrigerant is compatible with the existing equipment - modification may be required. Plan well ahead for long term availability of refrigerant The recommendations are the following: Identify all the points on the refrigeration units where leaks can occur ; check there is no leak or eliminate it in case of one ; install hermetically sealed units or use refrigerants with a lower or no ozone depleting potential Collect and label all waste and used liquid solvent and return to the supplier for recycling or reuse Consider recovering refrigerant for recycling
Energy Utilisation CO 2 generation is an energy intensive process; to typically produce carbon dioxide in a CO 2 recovery Plant requires approx. 0,5 kWh/m3 Most of this energy is used in the compressor to compress the incoming gas stream and intermediate steps to reach the appropriate pressure and temperature due also compressed refrigerants heat exchange. This high-energy use results in an indirect environmental impact from the power production plants. Competitive pressures and environmental concerns have resulted in a continuous improvement in the energy efficiency of CO 2 Plants through process innovation, equipment design, maintenance and efficient operating practices. In addition increasing integration with the energy systems of the customer, and improvements in power plant performance have considerably reduced this indirect impact. By far the biggest cost of operating a CO 2 Plant is process energy to power the compressors. Clearly the whole plant must be operated at optimum efficiency if costs are to be contained. However auxiliary costs can also be important such as heating for dryers regeneration, heating for the facilities, lighting, boiler plant operation and compressed systems. A step by step system to improve overall performance can be implemented as follows: Assemble and analyse invoices to determine how much of each type of fuel is being consumed. Alternative fuels may be an option. Record power consumption trends using chart recorders to highlight possible savings. Consumption during non-production hours can be particularly informative. Check tariffs to determine if the most appropriate one is being used from the electricity supplier for the pattern of use. Compare performance and target improvements to identify how the site performs against typical standards and other locations. Survey the site by actually walking around to establish opportunities for improvement via the action plan. A walk out of normal hours can reveal a lot. Prepare and implement an action plan to carry benefits into the future. Production management may be able to input to modified operating procedures, other proposals will require engineering support for detailing and implementation.
Large volumes of water containing treatment chemicals are used and subsequently discharged from many of our sites. The water may contain chromates, zinc, phosphonates, polyacrylates etc. Solid particles will also be present. They must only be discharged in an approved manner. Condensed water from air is usually acidic and may also contain metals leaching from pipework and solder. Approved cooler materials are critical. Recycled cooling water usually contains chemical treatment products used as biocides and to control corrosion. These includes chromates, phosphonates, polyacrylates, zinc, etc.. Some of these chemicals are strictly regulated, because of their bio-toxicity. They may enter the drainage system when the cooling circuit is purged. The use of chromates in new systems is not recommended because of their eco toxicity. It is important that site drainage systems are well understood. A plan of the system should be available showing all underground pipework and locations of all connections, inspection pits, outfalls, and separators/interceptors. Certain discharges may require treatment prior to release to ensure consent conditions are met. Methods include: oil interceptors, neutralization for acid/alkaline solutions, filtration and separation of solids. Use of all methods must be adequately covered by work instructions. Analysis and monitoring requirements necessary to meet any consent conditions must be undertaken. Similarly an inventory of all liquid effluent discharges indicating the location and receiving system will help to track and minimise. There are usually legislative requirements to be met when dealing contaminated water, whether it goes to drain or is removed from site by other means. It is critical that requirements are known, documented and met. The recommendations are the following: • Use water treatment chemicals that do not harm the environment e.g. those that do not contain chromates or mercury. • Use the minimum quantity of treatment chemicals necessary to achieve adequate system protection and to make sure that the quality of the discharge complies with local and national regulation limit values. A special permit from the authorities is normally needed to regulate such discharges and this permit may cover: • Temperature of discharge • pH of discharge • Concentration of chromate and chromite or other chemicals or metals Hence water may need to be neutralised before discharge and discharges of chromate and solids and oil should be removed from water before discharging it into the sewage system. Decanting and filtration may be used to improve the water quality before discharge.
Oil from our sites can enter the wider environment from various sources. There are several points of discharge: Oil from compressors or pumps due to leaks, vapour emissions and cleaning, Oil from hydraulic systems, Oil from transformers Oil from vehicle lubrication, Fuel oil Leakage of fresh and used oils can cause soil, surface water and groundwater contamination and must be managed properly. Special care must be taken during delivery operations. Oil Precautions must be taken to prevent oil from entering drainage systems. Oil must never be mixed with other substances e.g.... water, soil, solvents. Oil must always be collected in a barrel or drum and be delivered for recycling. A containment for each compressor or pump or transformer installation should be installed to collect the potential leaks and purges and these should not be discharged directly to the sewer. Oil barrels should be stored above a catch pot . Compressors should be kept well maintained to minimise the use of oil and the quantity and types of oil used on site should be minimised. Different types of oil e.g. hydraulic oil and lubricating oil should not be mixed. Water-oil mixtures When using water soluble emulsifiers for cleaning purposes the water emulsions have to be disposed of in a way acceptable to the authorities in the particular countries. Sometimes it may be possible to dispose of the emulsion by draining it into a suitable sewage water drainage system. When no emulsifiers are used oil and water must be separated in special oil-water separators. Water can then be discharged into the drainage water system, and the oil should be recycled. Good practice for use and disposal of oils includes: Do not allow oil to enter the drainage system from normal operations. If some oil is mixed with water (cleaning or rain water for example) separate and dispose of the water into the drainage system. Install a bund (or pit) at each compressor or transformer installation to collect the oil from leaks and purges. Use drip trays. Minimise the types and quantity of fresh oils Do not mix different types of oil waste, keep them by type and label accordingly Return waste oil for treatment or recycling Prevent inhalation of oil vapours by installing filters or precipitators The following substances are used as purification media. Sulphuric acid Spent sulphuric acid must never be drained into the sewage water system. Sulphuric acid should either be returned back to the producer for purification and reuse, neutralised in the lime pits or disposed of by a specialist. Sodium hydroxide (NaOH) and sodium carbonate (Na2CO3), from the purification. Storage should be reviewed to minimise the quantity of substances on site. The material safety datasheet (MSDS) of each substance must be available and emergency planning must be done to foresee the actions in the event of a spill Measures such as secondary containment for spill prevention should also be implemented.
An important environmental impact resulting from CO 2 Plants operations relates to consumption of materials. All opportunities for reduction should be sought both for environmental and financial reasons. A whole series of steps can be taken to achieve this end. Some examples of good practice include: Clear specifications and materials handling procedures Regular audit of materials purchased against materials used Avoidance of over-ordering Regular preventive maintenance Fitting covers and traps to solvent tanks Re-evaluate shelf -life characteristics to avoid unnecessary disposal Improvement of inventory and management control procedures Change from small volume to bulk containers Avoid spillages and leaks wherever possible Collect spilled or leaked material for reuse Introduction of new or modified processes which consume less Fundamental change to, or better control of process operating conditions e.g.. to extend absorber life Improved storage systems
Wastes such as those listed may need to be stored and transported separately, they have the potential to cause soil or groundwater pollution if not disposed of properly. Additionally, disposal by landfill may be required which is becoming increasingly scarce. Local legal requirements to ensure Duty of Care for waste management must be understood and adhered to. Catalysts usually contain biotoxic metals and must be either recycled by returning to the supplier or disposed of by certified companies. Batteries and electrical cells often contain hazardous materials. according to the kind of chemicals they must be returned to the supplier for recycling or disposed of by certified companies. Insulation material may be non-hazardous and can be simply disposed of by certified companies. Where insulation contains asbestos it must be so identified. When removing this material, precautions and controls have to be taken according to the nature of the hazard of the product and the local or national regulation. Material must be disposed of by a certified company and handled in such a way to prevent the release of asbestos fibbers; this may include enclosing in a sealed bag or wetting the material. Oil filters should be replaced by maintenance. Used filters should be disposed on authorized facilities. Absorbents such as active coal and Alumina drying desiccant may be similarly contaminated and should be handled by authorized companies when spent. Uncontaminated absorbent can be disposed of as non hazardous waste. Consideration should be given to return it to the supplier.
Noise is defined as sound which is undesired by the recipient (i.e. which intrudes, disturbs or annoys) EIGA document 85 “Noise management for the Industrial gases Industry” is relevant and helps simplify a complicated issue. Noise can be considered as an environmental nuisance and when audible off site represents a potential cause for complaint from site neighbors and the public. The main sources of out-door noise at a CO 2 Plant are: • CO 2 Blowers • Compressors and other process equipment • Stationary or mobile pumps on tank trailers for the liquid gases • Venting of tanks or trailers • Noise is generated not only by compressors but also by gas venting and even by piping that contains fast moving gases. Good practice includes: When purchasing or designing machinery and equipment, the sound levels shall be considered. The additional cost of choosing equipment with a comparable low sound level is low at this stage. To afterwards reduce the sound emission is much more expensive. Take the necessary steps to reduce noise from existing plant and equipment (e.g. acoustic screens a nd booths, silencers, modified operating routines) Drive the vehicles and operate equipment to minimise the sound generation. Site layout chosen to reduce off-site noise levels (e.g. use of natural land contours to buffer noise) Efforts to reduce noise at times of start up, shut down, changes plant configuration/operation Prepare an inventory of noise at the site boundary plus close to sources for occupational health reasons
All materials on site must be stored appropriately in order that risk of release to land, water or air is minimized. Above ground storage is preferred where possible. Storage containers should be fit for purpose and capable of long term storage without risk of release to the environment. All containers should be adequately marked to show the product stored. Where level indication cannot be made available, techniques to avoid overfilling should be in place. Transportable containers should be on hard standing with location chosen to minimise risk of spills entering site drains. Secondary containment should be provided as necessary and capable of holding 110% of the capacity of the largest container. Storage and containment arrangements should be inspected on a routine basis to guarantee continued integrity. Underground storage tanks (UST) could be a source of soil and groundwater contamination through leakage and spillage if not properly controlled and maintained. The conditions of an UST and pipe work should be checked regularly and a routine maintenance programme established. Any unused tanks should be left clean and empty (or sand filled). If a tank has been leaking, immediate action should be taken to remedy the leak and assess ground contamination. If liquid or gas is to be left in unused tanks, levels or pressure should be checked regularly to identify possible leakage. All waste which will be recovered, recycled or treated by a specialised company, or which will be disposed of at authorised facilities shall be stored and transported by authorised transporters in suitable containers clearly labelled to identify the composition of the waste. Different kind of waste must not be mixed but must be separated in different containers according to their type and the treatment they will receive. The storage itself must be organized in such a way that there is no risk of mixing the containers (separations in specific area, marking, records etc).
Polychlorinated biphenyls and triphenyls are toxic and carcinogenic substances. When uncontained they pose a health and safety risk and if involved in a fire can produce dioxins. Equipment should be tested for their presence and an inventory prepared. Where practicable the equipment should be replaced or refilled with oil which is PCB/PCT free when levels are above locally accepted limits. Transformers and capacitors containing PCB/PCT should be labelled accordingly. Disposal of this product and any material which has been contaminated (for example rags and absorbent material) should be controlled by national or local regulations. PCB’s or contaminated materials must be collected into suitable sealed containers, labelled and then recovered and treated by certified waste disposal companies. Costly high temperature incineration may be required. The trigger concentration for PCB contamination according to current European legislation is 50 ppm. EU Directive 96/59 refers, phase out date for PCBs by 2010. In addition some countries are signatories of the OSPAR convention which recommends more stringent phase out dates.
It is suggested the trainer has a discussion on these and other examples of environmental incidents which have taken place on Air Separation Plants. Specific examples are: Hydrocarbon refrigerants 635 kg of R22 was released during a plant overhaul caused by failure to shut down a refrigeration unit. The cooling water was shut down which caused a pressure build up in the condenser and the relief valve lifted causing the release. Action: The refrigeration unit will be closed down automatically when the plant shut down occurs. Release of 1360 kg of R22 resulting from fatigue failure of carbon steel nipples on a refrigeration unit. Action: Replace with plugs. Ammonia refrigerants A cloud of ammonia was released from a leaking expansion valve . Carbon Dioxide 12 tones of CO 2 were released when a safety valve of an storage tank opened and freeze.
Examples of incidents resulting in releases to water include: Overground fuel oil release 50,000 liters of boiler fuel oil escaped to drain when a plastic level indicator pipe became disconnected and the bund did not contain the release. Action: Ensure the effectiveness of secondary protection and avoid fragile plastic pipes. Underground pipework leak A leak from the pipework of an underground storage tank was caused by corrosion of pipework made from the wrong material. Oil entered the drainage system. Action: Use the recommended material and institute regular checks. HCl Release Hydrochloric acid escaped to a surface water channel. The level indicator was not functioning, the tank was overfilled and acid flowed out of the ventilation pipe. Action: Improve plant maintenance and if necessary the filling procedures.
Examples of incidents resulting in releases to water include: Underground diesel storage tank leak Ground contamination was caused when an underground tank leaked diesel. Action: Regular inspection of the condition of the tank and associated equipment is required with possible decommissioning and removal.
Operating the equipment at the manufacturers optimum parameters is the most efficient method of gas production.
