Process Safety and Environmental Impact Evaluation of a Nitric Acid Plant - Assignment Example

Process Safety and Environmental Impact Report Name: Instructor: Institution: Date: Contents 1.0 Executive Summary 3 2.0 Safety Analysis 3 3.0 Hazard and Operability (HAZOP) Analysis Study 8 Section of the system for HAZOP analysis 9 Selection of the study node 9 Description of the Design Intent 9 Selection of the Process Parameter and Guide words 10 Causes and Consequences of More or Higher Air ammonia ratio 10 Reccommended Action 11 4.0 Environmental Issues 12 i.Gaseous Effluents 12 ii.Liquid Effluents 12 iii.Solid Effluents 13 Potential Impacts of the Effluents on the Environment 13 Mitigation Measures to Reduce the Impact of the Effluents 15 5.0 Conclusion 16 References 17 Appendix 1: MSDS for Nitric Acid 19 Appendix 2: MSDS for Ammonia (Source: Airgas Company Ltd. , Version 0.05) 27 1.0 Executive Summary This work is a presentation of a report on process safety and environmental impact evaluation of a nitric acid plant that is to be set up in Shandong province, China. This project is to be done in collaboration with an Australian explosives company called Orica, which wants to expand its presence in China by providing commercial explosives and blasting systems to the mining and infrastructure industry. The report covers three major areas including; inherent plant safety analysis using relevant MSDS sheets, HAZOP analysis on one of the nodes of the process flow diagram, and environmental issues regarding the plant effluents. A comprehensive safety analysis has been discussed and found adequate to meet the required safety standards for dealing with nitric acid. HAZOP analysis was done on the section from hot gas valve to the valve that delivers nitric acid to the absorption tower. The results of HAZOP analysis identifies operability problems to personnel and equipment that may arise from the section and provides a recommendation to install standby valves. A number of environmental issues have also been identified, including gaseous effluents, liquid effluents, and solid effluents that cause environmental pollution. Various solutions have been recommended for reducing the impact of these effluents generated from the nitric acid plant. 2.0 Safety Analysis This section deals with the analysis of safety with regard to the MSDS sheet attached in the appendix. 2.1 Hazardous Materials The hazardous materials in the production of nitric acid is the ammonia that is used as process input materials, and nitric acid that is the process product. The discussions in these sections can be referred to the MSDS for nitric acid shown in appendix 1, and that of ammonia, shown in appendix 2 at the end of the report. a) Nitric acid Nitric acid is a clear, watery or yellowish to light brown liquid. It has acrid and suffocating odor. Mists and vapors from the acid irritate eyes, skin, respiratory tract, teeth, high concentrations may cause severe eye burn, blindness or scarring, with permanent damage. The acid is poisonous to human if ingested or inhaled, and also an experimental teratogen. Nitric acid is hygroscopic and a powerful oxidizing agent. It does not burn, it decomposes releasing poisonous and corrosive nitrogen oxide gases. Many substances readily react with the acid; can cause fire when it comes into contact with oxidizable materials, and may react explosively or ignite spontaneously with organic and inorganic substances. It reacts with water to produce corrosive, toxic fumes, with heat release (Ledgard, 2014). Water is usually used to fight nitric acid fires. Tight containers filled with the acid may develop high pressure when exposed to heat. On contact with metals, extremely flammable hydrogen gas is released. Potential Health Effects The primary entry routes of nitric acid are through inhalation, ingestion, skin contact and eye contact. Acute Exposure: Nitric acid causes skin corrosion, nose, eyes, gastrointestinal and respiratory tracts, and other tissues it may come into contact with. Severe burns may occur with scarring and necrosis. May be fatal by inhalation or ingestion. Skin: Causes severe skin irritation and burns, mild cases cause skin rush. The skin becomes clammy with cyanosis. Can result in deep, penetrating skin ulcers. Eyes: Nitric acid vapor and mists may cause very severe burns that may lead to loss of vision and permanent eye damage. Ingestion: Causes burns or permanent damage to the gastrointestinal, pharynx and digestive tract. The digestive tract may be perforated. Inhalation: Nitric acid is very fatal if inhaled, although the effects may delay. May cause burns in the nose, throat, and may experience wheezing, coughing, pulmonary edema, edema of the bronchi and larynx, inflammation, chemical pneumonitis and shortness of breath. May also cause respiratory tract irritation, and possible death in severe cases. Chronic exposure: Repeated exposure to nitric acid may cause chronic bronchitis, bronchial irritation, pneumonia, coughing, lung damage, erosion of teeth and skin lesions. Effects may delay. b) Ammonia This material is hazardous and reacts corrosively when it comes in contact with human body. Inhalation: Ammonia is destructive to the mucous membranes and the respiratory tract. The symptoms include coughing, burning sensation, wheezing, shortness of breath, nausea, vomiting and headache. Inhalation of ammonia causes edema of the bronchi, pulmonary and larynx, and spasm inflammation, and pneumonitis. Ingestion: If ingested, ammonia can cause severe burns, sore throat, diarrhea and vomit. These may lead to death. Skin Contact – Contact with the skin causes pain, burns and skin irritation. If absorbed beyond the dermal layer, it may cause systematic effects. Eye Contact – When it comes into contact with the eye, it causes pain, blurred vision, severe pain and burns or even eye damage. Severe exposure causes temporary or permanent bilindness. Chronic Exposure – Prolonged skin exposure can cause dermatitis, damage of the eye, kidney, lung or liver. 2.2 Emergency The victim should seek medical attention in case of skin exposure, eye contact, ingestion or inhalation of ammonia or nitric acid. The physician should treat the patient symptomatically and supportively. Always put on a self-contained breathing apparatus in pressure-demand with a protective gear, flame retardant coat, rubber boots, gloves and helmet, like any other fire. Nitric acid is not combustible, but due to its oxidizing properties, it may result to ignition of combustible materials. Use water to keep exposed containers cool. Health Emergency Measures Skin: When in contact with nitric acid, the victim should remove contaminated clothing and flush the exposed skin with plenty of water for at least 15 minutes, followed by soap and water. Patient should be taken to a treatment facility for topical therapy if pain and irritation persists. Patients with dermal hypersensitivity reactions may need topical antihistamines or topical corticosteroids. Eyes: Hold eye lids apart and flush with plenty of water for 15-30 minutes. The patient should not keep eyes closed or rub eyes. The patient should be referred to a physician or an ophthalmologist if pain, irritation and light sensitivity persists for medical aid. Inhalation: The patient should be moved to fresh air and examined for respiratory distress, respiratory tract irritation, pneumonitis, or bronchitis. Artificial respiration or oxygen may be administered if the patient is not breathing or has difficulty in breathing. Seek medical aid. Ingestion: If ingested, immediately administer 4-8 ounces of water or milk to the patient if alert and conscious. Don’t induce vomiting. Or give anything through the mouth. Examine the patient for gastrointestinal tract burns or irritation (Hignett, 2013). Fire Emergency Measures The firefighting team is responsible for firefighting activities in case of fire break out disaster within the plant. The preferred extinguishing media for nitric acid and ammonia fire is water spray, soda ash, regular foam, CO2, fog, or dry chemical. Ammonia is not considered a fire hazard, but gives out flammable vapors, which may explode when mixed with air. Water used in extinguishing fires should not be allowed into the sewer system. Fire Fighting Procedures: (a) Do not mix water with nitric acid inside container. It will generate vapor and heat. (b) If safe, remove container from area of fire. (c) Spray water on the containers exposed to fire until fire subsides. (d) For massive fires, use unmanned monitor nozzles or hose holder; if impossible, retreat. (e) Control acid vapors using water spray. (f) If there is danger of inhalation of fumes and vapors, use a positive pressure self-contained breathing apparatus. (g) Ware chemical protective gear for safety with nitric acid fire. 3.0 Hazard and Operability (HAZOP) Analysis Study Below is a process flow diagram of a typical dual pressure nitric acid plant. Figure 1: Dual low high pressure nitric acid production PFD (Source: European Fertilizer Manufacturers’ Association (EFMA), 2000). Section of the system for HAZOP analysis The section that will be considered for Hazard and Operability study is the section between the mixing section and the catalytic reactor section. The main hazard in these sections of the nitric acid process facility is the explosion due to air ammonia mixture. Figure 2 below shows a representative diagram of the section. Figure 2: P&ID for the ammonia-air mixing section and the catalytic reactor section. Selection of the study node The study node for HAZOP analysis starts from valve 1 to the temperature sensor of the catalytic reactor. High ratio of air ammonia mixture results to a higher temperature in the catalytic reactor (Hyatt, 2003). Description of the Design Intent The design is intended to control the ratio of air ammonia mixture below the hazardous levels, and keeping the ratio at a safe range. Valve 1 is an automatic ammonia valve that regulates the amount of flow of ammonia into the mixing section. When a high air ammonia ratio is detected, the valve automatically shuts down by tripping to shut down ammonia supply. Valve 2 regulates the flow of air ammonia mixture flow into the catalytic reactor depending either on the flow measurement of the meter or the temperature measured by the catalyst gauze. The temperature sensor measures and sends signals to the controller panel which in turn sends signals to valve 2 to increase, maintain or reduce the flow of air ammonia mixture into the catalytic reactor (European Fertilizer Manufacturers’ Association (EFMA), 2000). Below are descriptions of the pieces of equipment in the P&ID: a) Valve 1 – Regulation of flow of ammonia into the mixing section b) Valve 2 – Regulation of the flow of air ammonia mixture into the catalytic section c) Mixing section – mixes air ammonia in the desired ratio. d) Catalytic reactor – Contains catalytic gauze over which air ammonia reacts. e) Temperature sensor – Measures the temperature of the catalytic reactor and sends to the control panel. Selection of the Process Parameter and Guide words The process parameter of interest is the ratio of air ammonia that is fed into the catalytic reactor. The guide word applied in this study are higher or more, that is, the air ammonia ratio is higher or more than the desired range. Thus, the deviation propagation is higher air ammonia ratio or more air ammonia ratio (Rausand, 2005). Causes and Consequences of More or Higher Air ammonia ratio The table below shows the causes and consequences for more or higher air ammonia ratio on the HAZOP anode selected from the flow diagram of nitric acid production process. Table 1: Causes and consequences of higher or more temperature Item Connection Equipment Deviation Causes Potential Consequences Valve 1 From valve 1 pipe More ammonia from valve 1 Low air ammonia ratio Increase in flow rate Valve 1 From valve 1 pipe Higher temperature in the catalytic reactor Valve 1 stuck Catalytic reactor temperature increases Valve 2 From valve 2 pipe More air ammonia ratio Low temperature in the catalytic reactor Increase flow rate of ammonia Valve 2 From valve 2 pipe More air ammonia ratio Valve 2 stuck Excess flow of air ammonia mixture into the catalytic reactor Mixing chamber From valve 1 pipe Higher ammonia from valve 1 Low air pressure –low ammonia ratio Equipment explosion Mixing chamber From valve 1 pipe Higher ammonia from valve 1 Valve 1 stuck Equipment explosion Temperature Sensor From catalytic reactor Higher temperature from reactor Improper working of the sensor Higher temperature in the catalytic reactor, exceeding design temperature – Equipment damage Temperature Sensor From catalytic reactor Higher temperature from reactor Temperature sensor stuck Excess flow of air ammonia into the reactor Catalytic reactor From temperature sensor Higher temperature Temperature senor fail or improper working Increase in temperature in the reactor, exceeding design temperature – Damage of equipment. Reccommended Action An alarm system based on safety cause should be installed for the shut down sequence of the node when the air ammonia flow is higher than the desired range, and when temperatures detected in the reactor exceed the design temperature to ensure that the process equipment and process staff are protected. After this action has been implemented, the HAZOP analysis is performed on the node again. 4.0 Environmental Issues i. Gaseous Effluents (a) Tail gas The waste gas emitted in a nitric acid plant at the outlet of the absorber include; mono-nitrogen oxides (NOx), nitrous oxide (N2O), oxygen (O2), water vapor (H2O) and nitrogen gas (N2) (Gowariker, et al., 2009). The concentrations of mono-nitrogen oxides increases during the start-up period and the shut-down of the plant until a few hours when a stable condition is achieved. Some nitrous oxide is formed during the oxidation of ammonia, and the amounts produced are dependent on the combustion conditions, i.e. temperature and pressure, burner design and catalyst (Cheremisinoff & Rosenfeld, 2010). (b) Fugitive emissions Liquid ammonia contains about 0.2% of water which forms in the ammonia vaporizer. Periodic blow-down generates smaller amounts of gaseous ammonia. ii. Liquid Effluents (a) Boiler blow-down The salt content of the water in the boiler is controlled by a water blow-down in the steam vessel. (b) Ammonia vaporizer blow-down Periodic blow-down controls the build-up of water in the liquid ammonia inside the vaporizer. (c) Purging and sampling Occasional, nitric acid solutions are emitted during the purging and sampling process. (d) Lubrication oil Rotating machines, such as the turbines, compressors and pumps require occasional lubrication, the used oil get disposed of. iii. Solid Effluents (a) Catalyst for oxidation of ammonia With time, the catalyst is slowly poisoned, and therefore, require periodic replacement. (b) Catalyst recovery catchment A getter traps losses from precious metal catalyst and require replacement as the catchment efficiency decreases. (c) Reduction catalyst for NOx The catalyst loses efficiency after some time and therefore, require a replacement. (d) Filter Cartridges There is build-up of pressure drop in the elements that are used in the filtration of air, ammonia and a mixture of the two which breaks up the cartridges. (e) Solid deposit In some parts of the plant, significant quantities of platinum can be found in solid deposits. Potential Impacts of the Effluents on the Environment NOx reacts with water and ammonia to produce nitric acid vapor. Nitric acid affects human respiratory system and growth of plants. In the presence of sunlight, the oxides of nitrogen reacts with volatile organic compounds and some organic chemical compounds to form ozone layer and other toxic products, such as, nitrate radical, nitroarenes and nitrosamines. Ozone layer is the major cause of global warming. In addition, NOx gas effluents cause global cooling by forming OH radicals which are responsible for destroying methane molecules. This counters the global warming effect. Disposal of the metals used as catalysts causes water, air and soil pollution if not properly disposed and this will affect human and plants. Boiler blow-down waste release salts and other organics rich in brine. These boiler blow-down wastes causes environmental thermal effects and, land and water pollution from the wastes. Used oils released into the environment cause suffocation and death of plants and animals (World Bank Group;United Nations Environment Programme;United Nations Industrial Development Organization, 1999). Mitigation Measures to Reduce the Impact of the Effluents Mitigation of Gaseous Effluents Mono-nitrogen Oxides (NOx) Selective catalytic reduction and extended absorption are the best techniques available for reduction of NOx. Selective Catalytic Reduction (SCR) System Lower emissions of NOx can be achieved by means of SCR. Solutions of ammonia are injected into the stream of the effluent gas, and a catalyst is used to initiate the following reactions: 6NO + 4NH3 5N2 + 6H2O 6NO2 + 8NH3 7N2 + 12H2O 3O2 + 4NH3 2N2 + 6H2O Platinum, Vanadium pentoxide, zeolites and chromium/in oxides are the catalysts that can be employed. For good operation of the SCR catalyst, the tail gas coming from the absorber is pre-heated to a low temperature. The pre-heated tail gas is the mixed with the reactant gas to and the mixture of the two gases is passed over the catalyst bed. The advantage of the SCR system is that low contents of NOx are achieved, and pollution is reduced when high efficiency catalysts are used. Nitrogen dioxide and Nitric Oxide These gases are absorbed in equal volume in a solution of sodium hydroxide to form sodium nitrite. Excess nitrogen dioxide forms sodium nitrite and nitrate. A small reduction can be realized with process conditions that are suitable, although this technique only works when the nitrate/nitrite solution can either be used or disposed in a way that it will not cause environmental pollution. Nitrous Oxide Abatement for N2O effluents can be achieved by application of Non-selective catalytic reduction (NSCR) technology, or use of a decomposition chamber installed in the burner. Mitigation of Liquid Effluents The boiler blow-down is cooled, and if necessary, it should be neutralized before release. The ammonia from the ammonia vaporizer blow-down should be vaporized and then recovered back into the system. The remaining waste oil should be reprocessed by specific firms for re-use, in the same way as lubricating oil from compressors, pumps and turbo-set machine. Waste liquids from purging and sampling should be safely pumped back to the system. Mitigation of Solid Effluents The catalyst for ammonia oxidation and catalyst getter are reprocessed by a gauze manufacturer to recover precious metals and produce new gauzes. NOx reduction catalysts are also reprocessed and re-used. Filter cartridges can be cleaned and re-used or be disposed of safely after wear. Solid deposits with precious metals should be recovered and reprocessed by metal refiner. 5.0 Conclusion Plant process hazard analysis, equipment and personnel safety, and environmental impacts are the most important evaluations that should be done before setting up a new processing plant for hazardous substances. MSDS and safety analysis has been undertaken to ensure that the plant personnel and the general public are well informed and protected against the effects of nitric acid; its uses, hazards involved in handling the acid and treatment measures, disposal, and environmental impacts. Most, if not all of the environmental effluents can be mitigated to reduce environmental impacts of the plant. HAZOP analysis done on one of the process nodes between the cooler condenser and the absorption tower can help to reduce hazards in the plant process. References Appendix 1: MSDS for Nitric Acid Section 1: Product and Company Identification MSDS Product Name: Nitric acid Synonyms: Azotic acid, Aqua Fortis, Hydrogen nitrate Chemical Names: Nitric acid Chemical Formula: HNO3 Molar mass: 63.01 gmol-1 Recommended Application and Restriction of Use Recommended application: Making Explosives Restriction of use: Mining Industry Company Identification Company Name: Linyi Luguang Chemical Co., Ltd, in partnership with Orica Ltd. Section 2: Composition/ Information on Ingredients Section3: Hazards Identification Emergency Overview Clear watery liquid or yellowish to light brown. Acrid and suffocating odor. Causes irritation, eye burn, blindness or scarring. Poisonous if ingested or inhaled. Hygroscopic. Powerful oxidizing agent. Potential Health Effects Acute exposure causes skin corrosion, nose, eyes, gastrointestinal and respiratory tracts, and other tissues. Causes severe skin irritation and burns. Contact with eyes may lead to loss of vision. Ingestion causes burns to the gastrointestinal and digestive tract. The acid is very fatal if inhaled. Exposure to nitric acid may cause chronic bronchitis, bronchial irritation, pneumonia, coughing, lung damage (Proctor, et al., 2004). Section 4: First-aid Measures Seek medical attention in case of skin exposure, eye contact, ingestion or inhalation. The physician should treat the patient symptomatically and supportively. Section 5: Fire Fighting Measures Always put on a self-contained breathing apparatus in pressure-demand with a protective gear, flame retardant coat, rubber boots, gloves and helmet, like any other fire. Flash point - Not flammable LFL – Not flammable UFL – Not flammable Auto-ignition temperature – Not flammable Extinguishing media: Use water spray, soda ash, regular foam, CO2, fog, or dry chemical. Section 6: Accidental Release Measures Spills/Leak Measures: The first precautionary step is to isolate the area of spill and keep away unnecessary people. Stop spill if it there is no risk. Spills should be cleaned immediately, observing proper protection as in Section 6 and Section 8. Use inert material e.g. vermiculite or sand to absorb spills, then place in a container. Spills may be neutralized using sodium bicarbonate. Avoid runoff into water ways. Provide ventilation and get rid of all ignition sources, making sure to stay upwind. Vapors can be reduced by use of a vapor suppressing foam or a water spray. Waste Disposal: Small spill may be covered with sodium bicarbonate, or a mixture of lime and soda ash, then adding water to form a slurry. The slurry can then be discharged in a chipped marble lined sink with plenty of water. Large spills may be diked with foamed polyurethane, sand, earth or foamed cement and later disposed in accordance to the emergency protocol (United Nations Industrial Development Organization, 2009). Section 7: Handling and Storage Safe Handling: Use proper handling equipment when around or working with nitric acid and wash with plenty of water after handling. Contaminated clothing should be removed and washed before re-use. Keep container closed. Avoid contact with skin, eyes clothing and combustible materials, or inhalation and ingestion. Do not breathe vapor, gas or mist and area of use should be well ventilated. Avoid eating or smoking in areas of use. When diluting, slowly add the acid into water while stirring. Safety showers should be provided in handling areas Storage: Store away from sparks, flame and heat, light, or near metallic powders, hydrogen sulfide, carbides, organic acids, turpentine or other combustible materials. Keep in a cool, dry and well-ventilated area (Banerjee, 2002). Section 8: Exposure Controls, Personal Controls Engineering Controls: Use adequate ventilation to suppress airborne concentrations. Exposure Limits Component TWA STEL PEL IDLH Nitric acid vapor 2 ppm 4 ppm 4 ppm 25 ppm 1 ppm is approximately 2.5 mg/m3 4ppm: Require a positive pressure SCBA. Personal Protection: Eye protection – Avoid contact with eye. Wear protective chemical safety goggles or eyeglasses. You may wear a face shield for additional protection. Skin protection – Avoid skin contact. Wear Viton gauntlet, neoprene or acid retardant PVC gloves, trousers, jacket, boots, aprons etc. to avoid skin exposure. Respiratory Protection – Wear chemical cartridge respirator. At high risk, wear SCBA. Avoid breathing vapor. Ventilation: Adequate ventilation should be maintained. Nitric acid should only be used in a fume hood. Others: Emergency shower and eye bath be provided. Section 9: Physical and chemical properties Physical State and appearance: clear to yellow to liquid  Odor: pungent - strong odor pH: 1.0  Boiling point: 122oC Melting point: -42oC Vapor density: 2.17 (1 = air) Vapor Pressure: 6.8 mm Hg  Solubility: Soluble.  Density:1.41 g/cm3 Section 10: Stability and Reactivity Reactivity: Violent reaction with alkaline substances Chemical stability: Stable under normal conditions, decompose when it comes into contact with light, air or organic matter. Hazardous reactions: Decompose on heating, no hazardous polymerization. Conditions to avoid: Violent reaction with strong alkaline substances, should not come into contact with strong reducing agents, avoid contact with incompatible substances, excessive heat. Incompatible materials: Reducing agents, alkalis, alcohols, glycols, acids, aldehydes and amides, and metals Hazardous products of decomposition: Heating produce nitrogen oxides, corrosive gases may be formed (Urben, 2013). Section 11: Toxicological Information LDLo (human) – 5000 ppm for 5 minutes LCL (human) – 150 ppm (NO2) LC50 (mouse) – 67 ppm for 4 hrs. LC50 (Rat) – 65 ppm for 4 hrs. (NO2) LCL (Gold fish) – 750 ppm for 5 hrs. Section 12: Ecological Information At low concentrations, nitric acid can harm aquatic life. Can be dangerous if it finds its way to water intakes. Expected to biodegrade. Section 13: Disposal Consideration Waste generated must be disposed of in line with the existing environmental regulations Section 14: Transportation Information Shipping name: Nitric acid Hazard class: Corrosive Marine pollutant: No Section 15: Regulatory Information Nitric acid is considered a hazardous substance and should follow Hazard Communication Standards. Appendix 2: MSDS for Ammonia (Source: Airgas Company Ltd. , Version 0.05) Read More