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A&MA&M University Texas. A&MA&M University Texas Module 2 ENVIRONMENTAL CHALLENGES: OVERVIEW FACING INDUSTRY.

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Presentation on theme: "A&MA&M University Texas. A&MA&M University Texas Module 2 ENVIRONMENTAL CHALLENGES: OVERVIEW FACING INDUSTRY."— Presentation transcript:

1 A&MA&M University Texas

2 A&MA&M University Texas Module 2 ENVIRONMENTAL CHALLENGES: OVERVIEW FACING INDUSTRY

3 A&MA&M University Texas During the past years, the perceptions of pollutions have changed, industry has to find ways to make products without creating pollution or to recover and reuse the materials that we have considered wastes, this philosophy is called pollution prevention. Process Integration is highly compatible with this philosophy and complementary to it. This discipline encompasses a number of methodologies for designing and changing industrial processes, based on the unity of the whole process. This module presents an overview of the major environmental problems facing various industries in North America. It also presents Process Integration as a systematic approach to solving environmental problems. Purpose of Module 2 Two major industries (pulp and paper and petroleum refineries) are used as proof of the concept.

4 A&MA&M University Texas STRUCTURE OF MODULE 2 TIER 1: Basic Concepts TIER 2: Case Study TIER 3: Computer-Aided Module The module is divided into three tiers as follows:

5 A&MA&M University Texas TIER 1 : BASIC CONCEPTS This tier will provide a background including a general description of the major industries in North America, and focus on current environmental challenges facing the pulp and paper as well as the petroleum refining industries.

6 A&MA&M University Texas TIER 1 : BASIC CONCEPTS 1. Major Industries in North America.Major Industries in North America. 2.1 Driving forces, hurdles and potential. 2.3 Regulatory issues in North America. 2.2 Environmental discharges. 2.4 Best available environmental technologies for specific processes 2. Petroleum Industry 3. Pulp and Paper Industry 3.1 Driving forces, hurdles and potential. 3.3 Regulatory issues in North America. 3.2 Environmental discharges. 3.4 Best available environmental technologies for specific processes CONTENTS This section in broken into three sections:

7 A&MA&M University Texas

8 A&MA&M University Texas 1. MAYOR INDUSTRIES IN NORTH AMERICA The most important industrial sectors in North America were sought not through their production but reviewing the quantity of their releases and pollutants. Some statistics are organized by country : CANADA USAMEXICO

9 A&MA&M University Texas C anada is the world’s largest exporter of commodity-grade pulp and paper products, making this industry one of the most important pollutant sector. More Statistics:Canadian NPRITop 20 pollutantsMore information: C A N A D A Pulp, Paper and Paperboard mills

10 A&MA&M University Texas Top 20 Pollutants Released On Site in the Largest Quantities, 2001 C A N A D A

11 A&MA&M University Texas U S A More Statistics:TRITop 20 pollutantsMore information: Refineries and petroleum subproducts are included. T he U.S. petroleum industry is a strong contributor to the economic health of the United States, its production represents about the 25% of global production. T he Pulp and Paper industry is also important since the U.S. is the world’s largest consumer or these products, both in total tones per year and in terms of consumption per capita.

12 A&MA&M University Texas U S A

13 A&MA&M University Texas M E X I C O More information I n Mexico, the petroleum industry development is strongly linked to the employment rate, inflation, economic growth and capital investment. Hazardous Pollutants produced by Industry Petroleum industries provide raw material for the chemical industry.e.g. Gas natural Ammonia Fertilizers

14 A&MA&M University Texas Pulp and PaperPetroleum As we showed in the statistics section, there are two industries which are very important for the economy and development and also are causing serious environmental problems, making a link between the three countries. This research is attempting to show the way in which Process Integration can be used successfully. For this challenge we use the two major industries in North America:

15 A&MA&M University Texas No energy industry today is more engaged than petroleum in serving the global transportation, power generation, agricultural and consumer products sectors. Oil and natural gas are essential drivers of economic growth, that implies enormous social and environmental responsibilities..

16 A&MA&M University Texas 2.1 Driving forces, hurdles and potential. 2.4 Regulatory issues in North America. 2.3 Environmental discharges. 2.5 Best available environmental technologies for specific processes 2. Petroleum Industry 2.2 The Petroleum Refining Industry Definition Primary Products Industrial Processes in the Petroleum Refining Industry Refinery flow diagram Refinery air emission sources Types of wastewater produced in refineries Refinery Residuals Environmental discharges by process U.S. Regulations Mexican Regulations General Regulations

17 A&MA&M University Texas According to Abdallah S. Jum’ah, president of Saudi Aramco, energy today, must have three characteristics which are totally interdependent: RELIABILITY OF SUPPLY Any nation’s ability to sustain domestic development will depend on a ready resource of fuels and feedstock. No other energy supplier today is more capable of assuring such a continuity of supply than the petroleum industry. REASONABLE PRICE The petroleum industry is one of the most capital-intensive, high-maintenance, heavily regulated and excessively taxed industries operating worldwide. ENVIRONMENTAL PROTECTION Environment should be protected in order to achieve a sustainable development. In order to secure reliable supplies of oil and natural gas, there must be a price mechanism sufficiently fair and stable to maintain inflows of investment capital. In turn, the investment will help fund the industry’s considerable measures to protect environment. These three characteristics can act as: DRIVING FORCES HURDLES POTENTIALS First beak volume October 2002 The characteristics of the Petroleum Industry are related. In order to understand them, the following diagram in shown. 2.1 DRIVING FORCES, HURDLES AND POTENTIALS

18 A&MA&M University Texas The petroleum refining industry is a strong contributor to the economic health of the United States and Mexico. For Mexico, this industry has become the most important part in the national economy, it is the first source of currency for the country. Hydrocarbons will long remain the resource of choice to fuel future economic progress worldwide. This is a reason not only to protect air, water and land resources, but also to keep serving society through these products. DRIVING FORCES Economic and environmental situations are involved in the development of the petroleum industry, but its final challenge must be to fulfill the society needs.

19 A&MA&M University Texas HURDLES The petroleum industry has been dramatically impacted over the last three decades by geopolitical disruptions and volatile world oil prices. Today refiners must deal with: Increasing capital and operating costs of environmental compliance. Volatile crude prices Crude quality variability Low marketing and transport profit margins

20 A&MA&M University Texas The environmental impact produced by the petroleum industry covers the effects of all and each step in the energetic cycle, which means: explotation extraction refining transportation storage consumption releases HURDLES

21 A&MA&M University Texas POTENTIALS The natural source itself and the reliability of supply must be the greatest potential for the country that posses them. Technology plays an important role in developing the petroleum industry. Also, research and development have a great deal to do with keeping petroleum prices reasonable. In the past, new technologies had improved our methods of exploration and production, along with downstream efficiencies that yield cleaner- burning automotive fuels and higher-value products from every barrel of crude oil, allowing the increase and the improvement of the industry. The U.S. is the largest, most sophisticated producer of refined petroleum products in the world, representing about 25% of global production. Social and environmental issues will be decisive for the framework conditions for the future oil and gas industry. Technology is a tool that could help in achieving this task.

22 A&MA&M University Texas 2.2 PETROLEUM REFINING INDUSTRY Petroleum refining is the physical, thermal and chemical separation of crude oil into its major distillation fractions which are then further processed through a series of separation and conversion steps into finished petroleum products. Petroleum refineries are a complex system of multiple operations and the operations used at a given refinery depend upon the properties of the crude oil to be refined and the desired products DEFINITION

23 A&MA&M University Texas The primary products of this industry are divided into three categories: FUELS CHEMICAL INDUSTRY FEEDSTOCKS naphtha, ethane, propane, butane, ethylene, propylene, butylenes, butadiene, benzene, toluene and xylene FINISHED NON FUEL PRODUCTS solvents, lubricating oils, greases, petroleum wax, petroleum jelly, asphalt and coke motor gasoline, diesel and distillate fuel oil, jet fuel, residual fuel oil, kerosene and coke These products are used as primary input to a vast number of products: fertilizers, pesticides, paints, waxes, thinners, solvents cleaning fluids, detergents, refrigerants, anti-freeze, resins, sealants, insulations, latex, rubber compounds, hard plastics, plastic sheeting and synthetic fibers.

24 A&MA&M University Texas INDUSTRIAL PROCESSES IN THE PETROLEUM REFINING INDUSTRY The process of oil refining involves five major processes which are briefly described: SEPARATION PROCESSES These processes involve separating the different fractions of hydrocarbon compounds that make up crude oil base on their boiling point differences. Additional processing of these fractions is usually needed to produce final products to be sold within the market. Atmospheric distillation Vacuum distillation Light ends recovery (gas processing) SEPARATIONCONVERSIONTREATINGBLENDINGAUXILIARY ASSOCIATED OPERATIONS In order to understand where the environmental discharges come from, we will make a review of the refining process.

25 A&MA&M University Texas SEPARATIONCONVERSIONTREATINGBLENDINGAUXILIARY ASSOCIATED OPERATIONS Include processes used to bread down large longer chain molecules into smaller ones by heating using catalysts. Cracking (thermal and catalytic) Reforming Alkylation Polymerization Isomerization Coking Visbreaking CONVERSION PROCESSES INDUSTRIAL PROCESSES IN THE PETROLEUM REFINING INDUSTRY

26 A&MA&M University Texas SEPARATIONCONVERSIONTREATINGBLENDINGAUXILIARY ASSOCIATED OPERATIONS TREATING PROCESSES Petroleum-treating processes are used to separate the undesirable components and impurities such as sulfur, nitrogen and heavy metals from the products. Hydrodesulfurization Hydrotreating Chemical sweetening Acid gas removal Deasphalting INDUSTRIAL PROCESSES IN THE PETROLEUM REFINING INDUSTRY

27 A&MA&M University Texas SEPARATIONCONVERSIONTREATINGBLENDINGAUXILIARY ASSOCIATED OPERATIONS BLENDING/COMBINATION PROCESSES These are used to create mixtures with the various problem fractions to produce a desired final product, some examples of this are lubricating oils, asphalt, or gasoline with different octane ratings. Storage Blending Loading Unloading INDUSTRIAL PROCESSES IN THE PETROLEUM REFINING INDUSTRY

28 A&MA&M University Texas SEPARATIONCONVERSIONTREATINGBLENDINGAUXILIARY ASSOCIATED OPERATIONS AUXILIARY PROCESSES Processes that are vital to operations by providing power, waste treatment and other utility services. Products from these facilities are usually recycled and used in other processes within the refinery and are also important in regards to minimizing water and air pollution. Boilers Waste water treatment Hydrogen production Sulfur recovery plant INDUSTRIAL PROCESSES IN THE PETROLEUM REFINING INDUSTRY

29 A&MA&M University Texas Stabilizer Atmospheric Distillation Vacuum Distillation Sweetening Unit Visbreaker Hydrotreating Catalytic Cracking Solvent Extraction and Dewaxing LPH and Gas Gasoline Naphta Middle Distillates Gas Oil Lube-Base Stocks Sweet Gasoline Middle Distillates Gas Gasoline Light Gas Oil Lube Oil Waxes Gasoline, Naphtha and Middle distillates Fuel Oil Asphalt Treating and Blending Refinery fuel gas Refinery fuel oil Industrial fuels Asphalts Greases Lube oils Aviation fuels Diesels Heating oils LPG Gasoline Solvents Washed Crude REFINERY FLOW DIAGRAM

30 A&MA&M University Texas 2.3 ENVIRONMENTAL DISCHARGES Now, that we have seen an overview of the Refinery Process, we can make some questions: What is this industry discharging? How is it discharged? Where does it come from? In order to answer these questions, this section will show:  Air emission sources  Wastewater sources  Residuals  Environmental discharges by process

31 A&MA&M University Texas REFINERY AIR EMISSIONS SOURCES COMBUSTION EMISSIONS: associated with the burning of fuels in the refinery, including fuels used in the generation of electricity. EQUIPMENT LEAK EMISSIONS (fugitive emissions): released through leaking valves, pumps, or other process devices. They are primarily composed of volatile compounds such as ammonia, benzene, toluene, propylene, xylene, and others. PROCESS VENT EMISSIONS: typically include emissions generated during the refining process itself. Gas streams from all refinery processes contain varying amounts of refinery fuel gas, hydrogen sulfide and ammonia. STORAGE TAND EMISSIONS released when product is transferred to and from storage tanks. WASTEWATER SYSTEM EMISSIONS from tanks, ponds and sewer system drains.

32 A&MA&M University Texas TYPES OF WASTEWATER PRODUCED IN REFINERIES  SURFACE WATER RUNOFF is generated intermittently and may contain constituents from spills to the surface, leaks in equipment and materials in drains.  COOLING WATER which normally does not come into contact with oil streams and contains less contaminants than process wastewater. It may contain chemical additives used to prevent scaling and biological growth in heat exchanger pipes.  PROCESS WASTEWATER that has been contaminated by direct contact with oil accounts for a significant portion of total refinery wastewater. Many of these are sour water streams and are also subjected to treatment to remove hydrogen sulfide and ammonia.

33 A&MA&M University Texas REFINERY RESIDUALS Most refinery residuals are in the form of sludge, spend caustics, spend process catalysts, filter clay, and incinerator ash.  NON-HAZARDOUS RESIDUALS are incinerated, landfilled or regenerated to provide products that can be sold off-site or returned for re-use at a refinery.  HAZARDOUS WASTES are regulated under the Resource Conservation and Recovery Act (RCRA). Listed hazardous wastes include oily sludge, slop oil emulsion solids, dissolved air flotation floats, leads tank bottom corrosion solids and waster from the cleaning of heat exchanger bundles.  TOXIC CHEMICALS are also use in large quantities by refineries. These are monitored through the Toxic Release Inventory (TRI). These residuals could be classified as follows:

34 A&MA&M University Texas DISCHARGES AIR EMISSIONS LIQUID EFFLUENTS Approximately cubic meters of wastewater per ton of crude are generated when cooling water is recycled. Refineries generate solid wastes and sludges ranging from 3 to 5 kg per ton of crude processed, 80% of this sludges may be considered hazardous because or the presence of toxic organics and heavy metals. SOLID WASTES

35 A&MA&M University Texas ENVIRONMENTAL DISCHARGES BY PROCESS PART 1

36 A&MA&M University Texas ENVIRONMENTAL DISCHARGES BY PROCESS PART 2

37 A&MA&M University Texas ENVIRONMENTAL DISCHARGES BY PROCESS PART 3

38 A&MA&M University Texas ENVIRONMENTAL DISCHARGES BY PROCESS PART 4

39 A&MA&M University Texas 2.4 REGULATORY ISSUES IN NORTH AMERICA The Petroleum Refining Industry is unique in that the environmental requirements aimed at the industry are of two basic types: For the purpose of this module, we focus on refineries, which will be used to show some Process Integration techniques. Petroleum refineries are complex plants, and the combination and sequence of processes is usually very specific to the characteristics of the raw material and the products. For this reason the regulations for this sector become very specific and dispersed because an unit have regulations for water, air and land discharges, all of these managed by different official documents. Requirements directed at reducing the environmental impacts of the refineries themselves. Requirements mandating specific product qualities for the purpose of reducing the environmental impacts associated with the downstream use of the product.

40 A&MA&M University Texas In the case of the United States, there are numerous federal regulations affecting the Refinery Industry. The Environmental Protection Agency (EPA) contains several regulatory documents depending on the kind of resource that they pretend to protect, (e.g. Air, water and soil). Each one of these documents presents requirements which apply for every industrial sector. Then, when the requirements for a certain industry are needed, specific parts of the document should be used. For example, The Clean Air Act Amendments of 1990 has some programs for reducing air emissions from industry in which refineries are included: New Source Review, New Source Performance Standards National Emission Standards for Hazardous Air Pollutants At the same time, the New Source Performance Standards have some sections for Refineries: Subpart J Standards of Performance for Petroleum Refineries Subpart KKK Standards of Performance for Volatile Organic Liquid Storage Vessels. Subpart GG Standard of Performances for Stationary Gas Turbines. Subpart GGG Standards of Performance for Equipment Leaks of VOC in Petroleum Refineries U.S. REGULATIONS EPA website

41 A&MA&M University Texas All these sections contain flow diagrams, where depending on the process that is being used, it must be applied certain norm. To find more information: U.S. REGULATIONS

42 A&MA&M University Texas FEDERAL REQUIREMENTS AFFECTING THE REFINERY INDUSTRY

43 A&MA&M University Texas In Mexico, SEMARNAT (Secretaria de Medio Ambiente y Recursos Naturales) is in charge or the environmental regulations, but it does not cover all aspects of a refinery because some of them are very specific, for example, Proyecto NOM-088-ECOL-1994 Establish the maximum permissible levels of pollutants in the water discharges that become from storage and distribution of petroleum and its derivates. A classification of these norms is found in this website: Then, if the complete document is needed, you can check here: MEXICAN REGULATIONS

44 A&MA&M University Texas Besides all these complicated regulations, an specialized agency of the United Nations, the World Bank, has established emission levels for the design and operation of refineries, although country legislation should be accomplished. The guidelines given below present emissions levels normally acceptable to the World Bank Group.World Bank Group Emissions from the Petroleum Industry (milligrams per normal cubic meter) Effluents from the Petroleum Industry (milligrams per liter) Generation of sludges should be minimized to 0.3 kg per ton of crude processed, with a maximum of 0.5 kg per ton of crude processed. Solid Wastes GENERAL REGULATIONS World Band Group, Pollution Prevention and Abatement Handbook. World Bank Group. Pages

45 A&MA&M University Texas Primary wastewater treatment Consists on the separation of oil, water and solids in two stages. 1 st stage API separator or Corrugated plate interceptor. 2 nd stage Chemical and physical methods are utilized to separate emulsified oils from the wastewater. Physical methods may include the use of series of settling ponds with a long retention time, or the use of dissolved air flotation (DAF). Chemicals, such as ferric hydroxide or aluminum hydroxide are used to coagulate impurities. More information about the equipment More information about the equipment 2.5 ENVIRONMENTAL TECHNOLOGIES USED IN THE PETROLEUM INDUSTRY

46 A&MA&M University Texas Secondary wastewater treatment Dissolved oil and other organic pollutants may be consumed biologically. Biological treatment may require oxygen through different techniques: Activated sludge units Trickling filters Rotating biological contactors. Generates bio-mass waste which is treated anaerobically. Polishing Some refineries employ it as an additional stage of wastewater treatment to meet discharge limits. Activated carbon Anthracite coal Sand 2.5 ENVIRONMENTAL TECHNOLOGIES PETROLEUM INDUSTRY

47 A&MA&M University Texas In order to meet the SO x emissions limits and to recover saleable sulfur, refinery process off-gas streams should be treated. Process off-gas streams contain high concentrations of: hydrogen sulfide + light refinery fuel gases. This is accomplished by: Dissolving the hydrogen sulfide in a chemical solvent such as diethanolamine (DEA) in an absorption tower. Using dry adsorbents such as molecular sieves, activated carbon, iron sponge and zinc oxide. These fuel gases (methane and ethane) need to be separated before elemental sulfur can be recovered. Amine + hydrogen sulfide Is then heated and steam stripped to remove the hydrogen sulfide gas. Two processes are typically combined to remove sulfur from the hydrogen sulfide gas streams: Claus Process Beaven Process Scot Process Wellman-Land Process hydrogen sulfide 2.5 ENVIRONMENTAL TECHNOLOGIES PETROLEUM INDUSTRY Gas treatment and Sulfur Recovery

48 A&MA&M University Texas Other emissions sources come from periodic regeneration of catalysts, these emissions may contain: high levels of carbon monoxide + particulates + VOCs. CARBON MONOXIDE BOILER To burn carbon monoxide and VOCs ELECTROSTATIC PRECIPITATOR OR CYCLONE SEPARATOR To remove particulate matter Before being released to the atmosphere 2.5 ENVIRONMENTAL TECHNOLOGIES PETROLEUM INDUSTRY Gas treatment Solid waste treatment Sludge treatment use bioremediation or solvent extraction, followed by combustion of the residues or by use for asphalt. The residue could require stabilization before disposal to reduce the leachability of toxic metals. More information:

49 A&MA&M University Texas Pulp and PaperPetroleum As we showed in the statistics section, there are two industries which are very important for the economy and development and also are causing serious environmental problems, making a link between the three countries. This research is attempting to show the way in which Process Integration can be used successfully. For this challenge we use the two major industries in North America:

50 A&MA&M University Texas The uses and applications for paper and paper products are limitless. It is important because it gives us the opportunity or recording, storage and dissemination of information. Also, it is the most widely used wrapping and packaging material and it is also used for structural applications.

51 A&MA&M University Texas 3.1 Driving forces, hurdles and potential. 3.4 Regulatory issues in North America. 3.3 Environmental discharges. 3.5 Best available environmental technologies for specific processes 3. Paper Industry 3.2 Overview of the Pulp and Paper process Different methods Main steps of the process U.S. Regulations Canadian Regulations General Regulations

52 A&MA&M University Texas 3.1 DRIVING FORCES The U.S. forest products industry makes a strong contribution to the national economy, producing 1.2% of the U.S. GDP. The industry employed almost 1.3 million people just in the United States. Paper and wood products are used in many different applications both at home and at work. The Pulp and Paper Industry provides employment for vast number of people and plays a vital role in the overall economy of both the United States and Canada. Pulp and paper is the third largest industrial polluter to air, water and land in both Canada and the United States, and releases well over a hundred million kg of toxic pollution each year.

53 A&MA&M University Texas 3.1 HURDLES The Pulp and Paper industry in North America is threatened by:  Plantation forests of fast growing tree species are being developed such countries as Brazil, Indonesia, Chile.  Quality-stand of timber have become more difficult and costly to access.  New competitors, with lower fiber costs, have entered the market (e.g. Russia, Austria, Chile, Australia, New Zealand and Indonesia).

54 A&MA&M University Texas 3.1 POTENTIALS The strong U.S. economy of the late 1990s has revived the pulp and paper industry. Now, this industry is one with the biggest average annual pace growth. The Pulp and paper industry producers have some advantages: Potential of the US and Canadian market. Access to a substantial endowment of timber suitable for harvesting as saw and pulp logs. The high quality of wood- fiber derived from them. Access to low-cost, secure supplies of energy.

55 A&MA&M University Texas The manufacture of pulp for paper and cardboard employs different methods: CHEMIMECHANICAL A combination of the previous processes. Separates fibers by such methods as disk abrasion and billeting, this pulp can be used without bleaching to make printing papers for applications in which low brightness is acceptable. For other applications, bleaches like peroxides and hydrosulfites must be used. MECHANICAL Chemical pulps are made by cooking the raw materials, using the kraft (sulfate) and sulfite processes. Kraft processes produce a variety of pulps used mainly for packaging and high- strength papers and board. Oxygen, hydrogen peroxide, ozone, peracetic acid, sodium hypochlorite, chlorine dioxide, chlorine, and other chemicals are used to transform lignin into an alkali-soluble form. CHEMICAL 3.2 OVERVIEW OF THE PULP AND PAPER PROCESS

56 A&MA&M University Texas The main steps in pulp and paper manufacturing are: These steps are common for the three processes, although the difference is the units they use for each task. Wood yardPulpingBleaching Paper manufacture The significant environmental impacts of the manufacture of pulp and paper result from the pulping and bleaching processes. 3.2 OVERVIEW OF THE PULP AND PAPER PROCESS

57 A&MA&M University Texas PROCESSPURPOSEMAJOR TECHNOLOGIES PULPINGConvert wood chips of wastepaper into fibers suitable for papermaking. Chemical (Kraft, sulfite)- digesters, mechanical – refiners, semi chemical – digesters & refiners. CHEMICAL RECOVERY (KRAFT PULPING) Recovery of inorganic chemicals from spend pulping liquor and combustion of organic residuals to produce energy. Evaporation concentration recovery boiler, causticizing, calcining. BLEACHINGBrighten of whiten pulps by using chemicals to selectively remove lignin. Chlorine dioxide, oxygen, hypochlorite, peroxide, ozone, of chlorination- upflow of downflowtowers, vacuum washers, pumps, mixers. PAPER MANUFACTURE Prepare stock from pulp, sheet, dewater, dry, caleder. Heat box, sheet forming table. 3.2 OVERVIEW OF THE PULP AND PAPER PROCESS This table presents the purpose of each one of the processes presented before and the technologies used to reach their task.

58 A&MA&M University Texas 3.3 ENVIRONMENTAL DISCHARGES The principal solid wastes of concern include wastewater treatment sludge : kg/t of ADP. AIR EMISSIONS LIQUID EFFLUENTS SOLID WASTES ADP: Air dried pulp, defined as 90% bone-dry fiber and 10% water. t:metric ton.

59 A&MA&M University Texas U.S. REGULATIONS The key federal group responsible for the environment is the EPA, which is a regulatory agency that establish and enforce environmental standards. The purpose of the EPA is to conduct research and suggest solutions to environmental problems. Simultaneously, it has an obligation to monitor and analyze the environment. The components of the legislation that most influence the pulp and paper industry are the effluent limitation guidelines that define minimum effluent conditions for 1977 and WATER REGULATIONS AIR REGULATIONS 3.4 REGULATORY ISSUES

60 A&MA&M University Texas Up to 1970, stream quality standards in the United States were largely the responsibility of individual states. The federal government became dominant until 1970, when the Environmental Protection Agency (EPA) was established. In 1972, the Federal Water Pollution Control Act stipulated a step- wise schedule for meeting conventional discharge criteria, the first target level by 1977 being equivalent to “best practical technology” (BPT), and the second target level by 1983 being equivalent to “best available technology economically achievable”(BATEA). In the early 1980’s these regulations included toxic or sub-toxic substances through the National Pollutant Discharge Elimination System (NPDES). Among these were a number of byproducts of the chlorine bleaching process. Later, the EPA has increased the list of priority pollutants. The U.S federal regulations that deal with environmental protection change every four years. It is a constant challenge to this industry to keep up-to-date. BACKGROUND PARAMETERS TOXIC POLLUTANTS WATER REGULATIONS Other agencies: Effluent Standards and Water Quality Information Advisory Committee (ES&WQIAC). The Council of Environmental Quality. National Commission on Water Quality BACKGROUNDTOXIC POLLUTANTS GW: groundwood NI: nonintegrated

61 A&MA&M University Texas TOXIC POLLUTANTS Settlement agreement toxic pollutants:

62 A&MA&M University Texas BACKGROUND PARAMETERS GENERAL INFORMATION AIR REGULATIONS Talking about the Pulp and Paper industry, the objective of air regulations is the elimination of hazardous air pollutants such as methanol, total reduced sulfur gases, and chlorine. Maximum achievable control technology (MACT) is the level of control at the average of the best 12% of the mills in the EPA data base of that category. The MACT rules have three tiers sorted by mill type. MACT I is for chemical pulp mills including kraft, semichemical, and sulfite. MACT II is for kraft, soda, semichemical and sulfite combustion sources including recovery units, smelt dissolving tanks, and lime kilns. MACT III is for paper machines, mechanical pulping and secondary fiber and nonwood fiber. The Clean Air Act of 1963, was a benchmark piece of legislation. It represented the first allocation by the federal government of significant funds for air pollution problems. In 1970, President Richard Nixon decided to form the U.S. Environmental Protection Agency, which absorbed the National Air Pollution Control Administration. The Clean Air Act Amendments of 1970, covered three primary areas: Attainment and maintenance of National Ambient Air Quality Standards (NAAQS). Establishment of regulations covering the emission of certain pollutants from mobile and stationary sources. Establishment of New Source Performance Standards (NSPS). EPA established standards for seven pollutants: sulfur dioxide, total suspended particulates, carbon monoxide, nitrogen oxides, photochemical oxidants, hydrocarbons, and lead. NAAQS needed review every five years. The 1990 CAA is probably the most dramatically impacting air pollution legislation of all time became law in Possibly most important to the pulp and paper industry was the new air toxics control program. The 1990 law relied on technology to control emissions of 189 hazardous air pollutants. PM HAP: particulate matter hazardous material. TGO HAP: total gaseous organic hazardous material. Representative MACT II limits PARAMETERS

63 A&MA&M University Texas CANADIAN REGULATIONS In 1992, the federal Canadian government released new Pulp and Paper Effluent Regulations under the Fisheries Act. The PPER set limits on BOD5, TSS, and acute toxicity and had numerous reporting requirements. Regulations limiting the discharge of chlorinated dioxins and furans also went into effect in 1992 under the Canadian Environmental Protection Act (CEPA). The CEPA and PPER regulations resulted in a massive investment to change bleaching processes and install secondary treatment before the end of 1996 at a many Canadian mills. The first set of regulations for the pulp and paper industry, which came into force in 1971, did not limit the total amount of pollution, but rather permitted the discharge of pollutants in proportion to the production of the mill. In 1991, the federal government responded to public pressure by introducing a regulatory scheme that required mills to implement secondary treatment systems and abide by limits to control the discharge of certain harmful pollutants, including dioxins and furans. In 1992, the Pulp and Paper Effluent Regulations set minimum standards. BACKGROUNDPARAMETERS CANADIAN REGULATIONSBACKGROUND PARAMETERS MAXIMUM BDO AND MAXIMUM QUANTITY OF SUSPENDED SOLIDS AUTHORIZED FOR MILLS. WATER REGULATIONS AIR REGULATIONS THERE ARE NO LEGALLY BINDING CANADIAN FEDERAL OR PROVINCIAL REGULATIONS FOR AIR EMISSIONS FROM PULP MILLS FOR AMBIENT AIR QUALITY.

64 A&MA&M University Texas Except where an authorization or transitional authorization is issued authorizing the deposit of BDO matter or suspended solids, the maximum BDO of all BDO matter and the maximum quantity of all suspended solids that may be deposited in the case of a mill is determined by: In respect of any 24-hour period, the formula: In respect of any month the formula: Where : F = is equal to a factor of 5 in respect of BDO and 7.5 in respect of suspended solids, expressed in kilograms per tonne of finished product. RPR = is the reference production rate. D = number of days in a month. Original source: Department of Justice Canada MAXIMUM BDO AND MAXIMUM QUANTITY OF SUSPENDED SOLIDS AUTHORIZED FOR MILLS.

65 A&MA&M University Texas GENERAL REGULATIONS Emissions levels for the design and operation of each project must be established throuth the environmental assessment process on the basis of country legislation and the Pollution Prevention Handbook, which establishes the following. Air Emissions (milligrams per normal cubic meter) Liquid effluents Source: Pollution Prevention and Abatement Handbook World Bank Group. P

66 A&MA&M University Texas 3.5 ENVIRONMENTAL TECHNOLOGIES PULP AND PAPER INDUSTRY In the kraft pulping process, highly emissions of reduced sulfur compounds, measured as total reduced sulfur (TRS) and including hydrogen sulfide, methyl marcaptan, dimethyl sulfide, and dimethyl disulfide, are emitted. Sulfur oxide emissions are scrubbed with slightly alkaline solutions. The reduced sulfur-compounds gases are collected using headers, hoods, and venting equipment. Condensates from the digester relief condenser and evaporation of black liquor are stripped of reduced sulfur compounds. Stripper overhead and noncondensable are incinerated in a lime kiln or a combustion unit. Gas treatment More information: More information:

67 A&MA&M University Texas 3.5 ENVIRONMENTAL TECHNOLOGIES PULP AND PAPER INDUSTRY Wastewater treatment To remove suspended solids: Neutralization Screening Sedimentation Flotation To remove the organic content: Activated sludge Aerated lagoons Anaerobic fermentation Solid waste treatment Solid waste treatment steps include dewatering of sludge and combustion in an incinerator, bark boiler, or fossil-fuel- fired boiler. More information:

68 A&MA&M University Texas TIER 2 : STUDY CASE This tier will demonstrate the relevance of Process Integration for specific examples of key processes in the Pulp and Paper Industry as well as in Refineries.

69 A&MA&M University Texas STUDY CASE 1 KRAFT PULPING PROCESS As we saw in Tier 1, the Pulping Process can be accomplished by chemical, semichemical or mechanical methods. About 80% of the wood pulp in the United States is produced through the kraft chemical pulping process. A environmental problem associated with the kraft process is the atmospheric emission of considerable quantities of hydrogen sulfide. The serious health and environmental problems of discharging hydrogen sulfide to the atmosphere call for effective sulfur-waste reduction processes in a pulp and paper plant. The purpose of this study case is to employ the Mass Exchange Network methodology to develop an optimal design of recycle/reuse networks for reducing the emission of hydrogen sulfide for pulp and paper plants. (Dunn and El-Halwagi, 1993)

70 A&MA&M University Texas Digester DESCRIPTION OF THE KRAFT PROCESS Washers Evaporators Recovering Furnace Dissolving Tank Slaker Causticizers White Liquor Clarifier Lime Kiln CHIPS PULP Weak Black Liquor Strong Black Liquor Smelt Green Liquor Lime Mud White Liquor Lime Contaminated Condensate

71 A&MA&M University Texas Digester DESCRIPTION OF THE KRAFT PROCESS Washers Evaporators Recovering Furnace Dissolving Tank Slaker Causticizers White Liquor Clarifier Lime Kiln CHIPS PULP Weak Black Liquor Strong Black Liquor Smelt Green Liquor Lime Mud White Liquor Lime Wood chips, containing ligning, cellulose and hemicellulose are added to white liquor (NaOH, Na 2 S, Na 2 CO 3 ). The chips are cooked to solubilize the lignin. Contaminated Condensate

72 A&MA&M University Texas Digester DESCRIPTION OF THE KRAFT PROCESS Washers Evaporators Recovering Furnace Dissolving Tank Slaker Causticizers White Liquor Clarifier Lime Kiln CHIPS PULP Weak Black Liquor Strong Black Liquor Smelt Green Liquor Lime Mud White Liquor Lime The solubilized lignin leaves as black liquor, leaving the cellulose and hemicellulose which are the constituents of pulp. Contaminated Condensate

73 A&MA&M University Texas Digester DESCRIPTION OF THE KRAFT PROCESS Washers Evaporators Recovering Furnace Dissolving Tank Slaker Causticizers White Liquor Clarifier Lime Kiln CHIPS PULP Weak Black Liquor Strong Black Liquor Smelt Green Liquor Lime Mud White Liquor Lime It is sent to the bleaching of papermaking process, depending on the end product desired. Contaminated Condensate

74 A&MA&M University Texas Digester DESCRIPTION OF THE KRAFT PROCESS Washers Evaporators Recovering Furnace Dissolving Tank Slaker Causticizers White Liquor Clarifier Lime Kiln CHIPS PULP Weak Black Liquor Strong Black Liquor Smelt Green Liquor Lime Mud White Liquor Lime The main constituents of White Liquor are: NaOH, Na 2 S, Na 2 CO 3, Na 2 SO 4, Na 2 S 2 O 3, NaCl, water. Contaminated Condensate

75 A&MA&M University Texas Digester DESCRIPTION OF THE KRAFT PROCESS Washers Evaporators Recovering Furnace Dissolving Tank Slaker Causticizers White Liquor Clarifier Lime Kiln CHIPS PULP Weak Black Liquor Strong Black Liquor Smelt Green Liquor Lime Mud White Liquor Lime Contaminated Condensate The Weak Black Liquor is processed through a series of evaporators to increase the solid content from 15% to 70% approximately.

76 A&MA&M University Texas Digester DESCRIPTION OF THE KRAFT PROCESS Washers Evaporators Recovering Furnace Dissolving Tank Slaker Causticizers White Liquor Clarifier Lime Kiln CHIPS PULP Weak Black Liquor Strong Black Liquor Smelt Green Liquor Lime Mud White Liquor Lime The Strong Black Liquor is incinerated to supply energy for the pulping process and to form inorganic smelt. Contaminated Condensate

77 A&MA&M University Texas Digester DESCRIPTION OF THE KRAFT PROCESS Washers Evaporators Recovering Furnace Dissolving Tank Slaker Causticizers White Liquor Clarifier Lime Kiln CHIPS PULP Weak Black Liquor Strong Black Liquor Smelt Green Liquor Lime Mud White Liquor Lime Na 2 CO 3 and Na 2 S Contaminated Condensate

78 A&MA&M University Texas Digester DESCRIPTION OF THE KRAFT PROCESS Washers Evaporators Recovering Furnace Dissolving Tank Slaker Causticizers White Liquor Clarifier Lime Kiln CHIPS PULP Weak Black Liquor Strong Black Liquor Smelt Green Liquor Lime Mud White Liquor Lime Smelt is dissolved in water to form the Green Liquor. Contaminated Condensate

79 A&MA&M University Texas Digester DESCRIPTION OF THE KRAFT PROCESS Washers Evaporators Recovering Furnace Dissolving Tank Slaker Causticizers White Liquor Clarifier Lime Kiln CHIPS PULP Weak Black Liquor Strong Black Liquor Smelt Green Liquor Lime Mud White Liquor Lime NaOH, Na 2 S, Na 2 CO 3 and water. Contaminated Condensate

80 A&MA&M University Texas Digester DESCRIPTION OF THE KRAFT PROCESS Washers Evaporators Recovering Furnace Dissolving Tank Slaker Causticizers White Liquor Clarifier Lime Kiln CHIPS PULP Weak Black Liquor Strong Black Liquor Smelt Green Liquor Lime Mud White Liquor Lime Lime (CaO) is converted to CaOH 2 in presence of water. Contaminated Condensate

81 A&MA&M University Texas Digester DESCRIPTION OF THE KRAFT PROCESS Washers Evaporators Recovering Furnace Dissolving Tank Slaker Causticizers White Liquor Clarifier Lime Kiln CHIPS PULP Weak Black Liquor Strong Black Liquor Smelt Green Liquor Lime Mud White Liquor Lime CaOH 2 reacts with Na 2 CO 3 to form NaOH and a CaCO 3 as precipitant. Contaminated Condensate

82 A&MA&M University Texas Digester DESCRIPTION OF THE KRAFT PROCESS Washers Evaporators Recovering Furnace Dissolving Tank Slaker Causticizers White Liquor Clarifier Lime Kiln CHIPS PULP Weak Black Liquor Strong Black Liquor Smelt Green Liquor Lime Mud White Liquor Lime The CaCO 3 is heated to regenerate the CaO and release CO 2. Contaminated Condensate

83 A&MA&M University Texas Digester DESCRIPTION OF THE KRAFT PROCESS Washers Evaporators Recovering Furnace Dissolving Tank Slaker Causticizers White Liquor Clarifier Lime Kiln CHIPS PULP Weak Black Liquor Strong Black Liquor Smelt Green Liquor Lime Mud White Liquor Lime NaOH, Na 2 S, NaCO 3 and water. Contaminated Condensate

84 A&MA&M University Texas Digester EMISSION SOURCES OF THE KRAFT PROCESS Washers Evaporators Recovering Furnace Dissolving Tank Slaker Causticizers White Liquor Clarifier Lime Kiln CHIPS PULP Weak Black Liquor Strong Black Liquor Smelt Green Liquor Lime Mud White Liquor Lime Air Stripping Contaminated Condensate Air Wastewater Air Emission Evaporators Recovery Furnace Air Stripping R2 R1 R3 Three major sources in the Kraft Process are Responsible for the majority of the H 2 S emissions.

85 A&MA&M University Texas INTERNAL MASS SEPARATING AGENTS Digester Washers Evaporators Recovering Furnace Dissolving Tank Slaker Causticizers White Liquor Clarifier Lime Kiln CHIPS PULP Strong Black Liquor Smelt Lime Mud White Liquor Lime Air Stripping Contaminated Condensate Air Wastewater Air Emission Weak Black Liquor Green Liquor S2 Weak Black Liquor S3 Green Liquor S1 White Liquor Several Mass-Exchange operations such as absorption or adsorption can be employed to reduce the H 2 S emissions. Three liquid streams that already exist in the plant (process MSAs) can be used.

86 A&MA&M University Texas Three external MSAs will be considered potential candidates for recovering H 2 S: S 4, Diethanolamine (DEA) S 5, Activated Carbon S 6, 30 wt% Hot potassium carbonate solution EXTERNAL MASS SEPARATING AGENTS

87 A&MA&M University Texas REACTIVE MASS-EXCHANGE NETWORK Recovery Furnace Emissions, R1 Evaporator Emissions, R2 R3, Air Stripping Emissions R1R2R3 To atmosphere White Liquor, S1 Green Liquor, S2 Black Liquor, S3 DEA, S4 Activated Carbon, S5 Hot K 2 CO 3 solution, S6 S1 S2 S3 S4 S5 S6

88 A&MA&M University Texas REACTIVE MASS-EXCHANGE NETWORK Recovery Furnace Emissions, R1 Evaporator Emissions, R2 R3, Air Stripping Emissions R1R2R3 To atmosphere White Liquor, S1 Green Liquor, S2 Black Liquor, S3 DEA, S4 Activated Carbon, S5 Hot K 2 CO 3 solution, S6 S1 S2 S3 S4 S5 S6 Causticizer Digester Dissolving TankDigester SlakerEvaporators

89 A&MA&M University Texas DATA FOR THE KRAFT PROCESS PROBLEM DATA FOR THE WASTE STREAMS DATA FOR THE MASS SEPARATING AGENTS

90 A&MA&M University Texas The solution of this problem will follow two different approaches: ALGEBRAICGRAPHICAL DESIGN METHODOLOGY We are looking forward the potentials for waste reduction in the Kraft Process by establishing tradeoffs between environmental and economic objectives in order to obtain the optimal configuration for a Waste-reduction system.

91 A&MA&M University Texas GRAPHICAL APPROACH INTERPRET THE RESULTS These are the main steps that we will follow to find an optimal design of recycle/reuse networks for reducing the emission of hydrogen sulfide from a pulp and paper plant using a GRAPHICAL APPROACH. PLOT RICH STREAMOBTAIN PINCH POINT PLOT LEAN STREAM CREATE ONE-TO-ONE CORRESPONDENCE

92 A&MA&M University Texas GRAPHICAL APPROACH RICH COMPOSITE STREAM The first step is to plot the mass exchanged or each rich stream versus its composition. Each stream is represented as an arrow whose tail corresponds to its supply composition and its head to its target composition. The slope of the arrows will be equal to the stream flowrate and the vertical distance between the tail and the head of each arrow represents the mass of pollutant that is lost by each rich stream: MR i =G i (y i s – y i t ), i=1,2,…,N R. Each arrow should be placed starting with the waste stream having the lowest target composition.

93 A&MA&M University Texas GRAPHICAL APPROACH y The rich composite stream is obtained by applying superposition to the rich streams. This rich composite stream represents the cumulative mass of the pollutant lost by all the streams. y RICH COMPOSITE STREAM

94 A&MA&M University Texas GRAPHICAL APPROACH The second step is to generate a one-to-one correspondence among compositions of the three waste streams and the six MSAs. Consider a waste stream i, and and MSA, j, for which equilibrium is given by: y i *= f i (x j *) For any mass-exchange operation to be thermodynamically feasible, some conditions must be satisfied: x j y i * To generate the one-to-one correspondence, we use the following equation: y=f(x j +ε j ) Where ε j is the minimum allowable composition difference, which means that we are adding a driving force to allow mass transfer. A deep explanation of these concepts is given in Module 3. ONE-TO-ONE CORRESPONDENCE

95 A&MA&M University Texas GRAPHICAL APPROACH MSA1 White liquor MSA2 Green liquor Equilibrium equation y 1 = x (10) x1 y 2 = x (10) x2 Adding the driving force y 1 = x (10) (x1+ε1) ε 1 = 7.64 y 2 = x (10) (x2+ε2) ε 2 = 3.20 Supply correspondence y 1 s = x (10) ( ) y 1 s = 4.91 y 2 s = x (10) ( ) y 2 s = Target correspondence y 1 t = x (10) ( ) y 1 t = 9186 y 2 t = x (10) ( ) y 2 t = Some examples of the generation of the one-to-one correspondence are the following: The equilibrium equation for the MSA3 (Black liquor) is: y 3 =352.8 x ONE-TO-ONE CORRESPONDENCE

96 A&MA&M University Texas GRAPHICAL APPROACH The mass of pollutant that can be gained by each process MSA is plotted versus the composition scale of that MSA Mass of pollutant that can be gained by each MSA is calculated: MS j = L j c (x j t – x j s ) j=1,2,…,N SP Also in this case, the arrows represent each of the process MSA, being the tail the supply composition and the head the target composition. Once again, we used the diagonal rule of superposition to obtain the cumulative mass of the pollutant gained by all the MSAs. LEAN COMPOSITE STREAM

97 A&MA&M University Texas GRAPHICAL APPROACH Integrated Mass Exchange PICH POINT Pinch Point The next step is to plot both composite streams on the same diagram. To guarantee thermodynamic feasibility the lean composite should be above and left of the waste composite stream. The lean composite stream can be slid down until it touches the waste composite stream. The point where the two composite streams touch is called “mass exchange pinch point”. Lean Composite Stream Rich Composite Stream The vertical overlap between the two composite streams is the maximum amount of the pollutant that can be transferred from the waste streams to the process MSAs. Excess Mass Exchanged The vertical distance referred as Excess Mass Exchanged corresponds to the capacity of the process MSAs to remove pollutants that cannot be used because of thermodynamic infeasibility.

98 A&MA&M University Texas ALGEBRAIC APPROACH CREATE ONE-TO ONE CORRESPONDENCE MASS-EXCHANGE CASCADE DIAGRAM TABLE OF EXCHANGEABLE LOADS (TEL) COMPOSITION INTERVAL DIAGRAM The Algebraic Approach follows these steps:

99 A&MA&M University Texas ALGEBRAIC APPROACH COMPOSITION-INTERVAL DIAGRAM (CID) The CID is a useful tool for visualizing the mass exchange insuring thermodynamic feasibility.

100 A&MA&M University Texas ALGEBRAIC APPROACH COMPOSITION-INTERVAL DIAGRAM (CID) 1.The composition scale for the waste stream is established. 2. Corresponding composition scales for the process MSAs are created. INTERVALS

101 A&MA&M University Texas ALGEBRAIC APPROACH COMPOSITION-INTERVAL DIAGRAM (CID) 3. Each process stream is represented as a vertical arrow The tail of each arrow represents its supply composition and its head represents its target composition. S3 R1 R3 R2 S1 S2 Horizontal lines are drawn at the heads and tails of the arrows to define composition intervals. INTERVALS These intervals are numerated From top to bottom.

102 A&MA&M University Texas ALGEBRAIC APPROACH TABLE OF EXCHANGEABLE LOADS (TEL) By constructing the TEL, we want to determine the mass-exchange loads of the process streams in each composition interval. The exchangeable lead of each waste stream with passes through each interval is defined as: W i,k R = G i (y k-1 – y k ) W 1,1 R = 0.433( ) W 1,2 R = 117( ) W 2,2 R = 0.433( ) W j,k S = L j (x j.k-1 – x j,k ) W 1,4 S = 0.049( ) W 1,5 S = 0.04( ) W 2,5 S = 0.049( ) W k R = Σ W i,k R W 2 R = W 1,2 R + W 2,2 R = W k S = Σ W j,k S W 5 S = W 1,5 S + W 2,5 S =

103 A&MA&M University Texas ALGEBRAIC APPROACH k Residual Mass from Preceding Interval δ k-1 δ k Residual Mass to Subsequent Interval Material Balance of the key pollutant should be done for each interval. TABLE OF EXCHANGEABLE LOADS (TEL) Mass Recovered From Waste Streams WkRWkR Mass Transferred To MSAs WkSWkS

104 A&MA&M University Texas ALGEBRAIC APPROACH TABLE OF EXCHANGEABLE LOADS (TEL) A negative δ k indicates that the capacity of the process leans streams at that level is greater than the load of the waste streams. The most negative δ k is the excess capacity of the process MSAs when removing the pollutant.

105 A&MA&M University Texas ALGEBRAIC APPROACH TABLE OF EXCHANGEABLE LOADS (TEL) On the revised cascade diagram the location at which the residual mass was the most negative should be zero. It corresponds to the pinch point. PINCH POINT The excess capacity of the process MSA should be reduced by lowering the flowrate. The new flowrate is calculated as follows: m 3 /s Another TEL should be constructed after removing the excess capacity of the MSA.

106 A&MA&M University Texas Since the graphical approach, we saw that the pollutant could be removed just by using one MSA, so there is no need of a network. This problem has some different solutions that could be taken depending on how much we want to spend. The following figure is one solution, in which some material balance should be done in order to give the right flowrate to each absorber. Absorber 1 Absorber 2 Absorber 3 R1R2R3 White Liquor 117 m 3 /s 3.08e-5 kmol/m m 3 /s 1.19e-5 kmol/m m 3 /s 8.20e-5 kmol/m 3 2.1e-7kmol/m m 3 /s kmol/m e-4 m 3 /s kmol/m m 3 /s kmol/m kmol/m 3

107 A&MA&M University Texas Absorber R1R2R3 White Liquor 117 m 3 /s 3.08e-5 kmol/m m 3 /s 1.19e-5 kmol/m m 3 /s 8.20e-5 kmol/m m 3 /s 2.1e-7 kmol/m m 3 /s 0.32 kmol/m kmol/m 3 Another way of achieve this task is the following, in which the rich streams are for final disposal and can be mixed and treated as one stream, also, his arrange is more desirable in terms of costs because just one unit is needed.

108 A&MA&M University Texas STUDY CASE 2 PETROLEUM REFINERY WASTES A major concern in refineries is the release of phenols, although described as this, the category may include a variety of similar chemical compounds among which are polyphenols, chlorophenols, and phenoxyacids. The concern is because of their toxicity to aquatic life and the high oxygen demand they sponsor in the streams that receive it. Phenols are toxic to fish and also they can cause taste and odor problems when present in potable water.

109 A&MA&M University Texas The next study case applies some of the skills of Process Integration to show the methodology once again and make it more understandable. This case was taken from El- Halwagi, M. “Pollution Prevention through Process Integration”, “The process generates two major sources of phenolic wastewater; one from the catalytic cracking unit and the other from the visbreaking system. Two technologies can be used to remove phenol from R1 and R2: solvent extraction using light gas oil S1 (a process MSA) and adsorption using activated carbon S2(an external MSA). A minimum allowable composition difference, ε j, of 0.01 can be used for the two MSAs. By constructing a pinch diagram for the problem, find the minimum cost of MSAs needed to remove phenol from R1 and R2. How do you characterize the point at which both composite streams touch? Is it a true pinch point?” PROBLEM STATEMENT Rich stream MSAs DATA

110 A&MA&M University Texas Stabilizer Atmospheric Distillation Vacuum Distillation Sweetening Unit Visbreaker Hydrotreating Catalytic Cracking Solvent Extraction and Dewaxing LPH and Gas Gasoline Naphta Middle Distillates Gas Oil Lube-Base Stocks The first step in a petroleum refinery is to preheat the crude, then it is washed with water to remove various salts. Treating and Blending Refinery fuel gas Refinery fuel oil Industrial fuels Asphalts Greases Lube oils Aviation fuels Diesels Heating oils LPG Gasoline Solvents PROCESS DESCRIPTION Sweet Gasoline Middle Distillates Gas Gasoline Light Gas Oil Wastewater, R1 Lube Oil Waxes Gasoline, Naphtha and Middle distillates Fuel Oil Asphalt Wastewater, R2 Gas oil and heavy stocks are fed to a catalytic-cracking unit to be converted to lower molecular weight fractions. The main waste stream from this process is the condensate from stripping in the fractionating column. This condensate commonly contains ammonia, phenols and sulfides as contaminants, this has to be stripped to remove ammonia and sulfides. The bottom product of the stripper must be treated to eliminate phenols. The light gas oil leaving the fractionator can serve as a lean-oil solvent in a phenol extraction process, being this a beneficiary mass transfer because in addition to purify water, phenols can act as oxidation inhibitors and as color stabilizers. The main objectives of visbreaking are to reduce the viscosity and the pour points of vacuum-tower bottoms and to increase the feed stocks to catalytic cracking. The source of wastewater is the overhead accumulator on the fractionator, where water is separated from the hydrocarbon vapor. This water contains phenols, ammonia an sulfides

111 A&MA&M University Texas 1. PLOT THE RICH STREAM

112 A&MA&M University Texas 1. PLOT THE RICH STREAM

113 A&MA&M University Texas 2. ONE-TO-ONE CORRESPONDANCE y = m(x+ε) + b y 1 s = 2( ) = 0.04 y 1 t = 2( ) = 0.06 y 2 s = 0.02( ) = y 2 t = 0.02( ) = To generate the one-to-one correspondence, we use the following equation: y=f(x j +ε j ) Where ε j is the minimum allowable composition difference. ε j =0.01 In this case the equilibrium equation is linear:

114 A&MA&M University Texas 3. PLOT THE LEAN STREAM x1sx1s x1tx1t

115 A&MA&M University Texas y x1x1 x2x Stream 1 would not be useful, since external MSAs should be used before and after using this stream. That means that this is not a true pinch point. 4. OBTAIN THE PINCH POINT

116 A&MA&M University Texas 5. INTERPRET THE RESULTS y Unit 1 Unit 2 Unit 3 The lean stream can be moved to remove the pollutant in another range of composition, but still three units would be needed.

117 A&MA&M University Texas 5. INTERPRET THE RESULTS y x1x1 x2x Unit 1 Unit 2 If the lean stream remove the pollutant since its higher composition, just 2 units are needed.

118 A&MA&M University Texas Mass removed by Process MSA Mass removed by External MSA y 5. INTERPRET THE RESULTS

119 A&MA&M University Texas Alan P. Rossiter. Waste Minimization through Process Design. pp McGraw Hill Nicholas P. Cheremisinoff, Handbook of Pollution Prevention Practices. pp , Marcel Dekker Inc The World Bank Group. Pollution Prevention and Abatement Handbook pp , El-Halwagi, M. M. Pollution Prevention through Process Integration. Academic Press Dunn R., El-Halwagi, M. M. Optimal Recycle/Reuse Policies for Minimizing the Wastes of Pulp and Paper Plants. J. Environ. Sci. Health, A28(1), (1993). El-Halwagi, M.M., El-Halwagi, A.M., Manousiouthakis, V. Optimal Design of the Phenolization Networks for Petroleum-Refinery Wastes. Trans IChemE, Vol 70, Part B, pp August Environmental Update #12, Hazardous Substance Research Centers/Southwest Outreach Program, June Abdallah S. Jum’ah, president and CEO, Saudi Aramco. Petroleum and social responsibility: and agenda for action. News Feature. First bread volume October Energy and Environmental Profile of the U.S. Petroleum Refining Industry. December U.S. Department of Energy, Office of Industrial Technologies EPA Office of Compliance Sector Notebook Project, Profile of the Petroleum Refining Industry, September National Pollutant Release Inventory (Canada) 2001 Toxic Release Inventory Executive Summary (US) Input to the AMG Working Group Studying the Impact of Greenhouse Gas Abatement on the Competitiveness of Canadian Industries. Pulp, Paper and Paperboark Mills. Manufacturing Industries Branch. Industry Canada. March 11, 2002 Instituto Nacional de Estadistica, Geografia e Informatica (Mexico)


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