SANDSTONE DEAGGLOMERATION FOR FRAC SAND

Sand particles derived from sandstone are delivered to the crusher hopper as rocks and boulders. Unlike mine crushing where the purpose is to reduce the size of the rocks to go into mills, the goal in frac sand operations is to…

NFPA 652 DUST HAZARD ANALYSIS (DHA) STUDY
Coal & Solid Fuels handling facilities

The most recent NFPA publication applicable to cement and lime plants, NFPA 652, mandates that every industrial facility handling solid fuels needs to complete a Dust Hazard Analysis (DHA) Study by August 2018, after which deadline plants risk becoming non-compliant.

Most cement and lime plants use coal and other solid fuels for their operation and therefore come under the purview of this mandate.

NFPA 652 “Standard on the Fundamentals of Combustible Dust” was created to include several older standards (NFPA-61, 68, 654) as a single go-to source for a systematic study of fire and explosion hazards and to develop mitigation measures.

The DHA Study promotes awareness of the following principles:

• Fuel management controls.
• Ignition source controls.
• Restraining the spread of any combustion event.

It applies to equipment handling coal and other combustible dusts, including Dust Collectors, Bucket Elevators, Drag and Screw Conveyors, Pneumatic Conveying Systems, and Storage Bins and Silos.

DHA consists of 3 main steps to complete the analysis.

Material and Process Identification:

• Determine the characteristics of the dust with tests recommended in NFPA 652 to assess how combustible or explosible the dust is.

• Identify the process areas where there exists potential combustibility and explosibility

Material and Process Hazard Analysis:

• Evaluation of every process area that could promote fire and explosion hazards
• For each identifies hazard area, the following aspects are analyzed:
  • Is the dust combustible in this segment?
  • Is the dust suspended in air?
  • Is the dust concentration such as to support a deflagration?
  • Is there an ignition source that could ignite the dust cloud present?
  • What hazard management controls are in place?

 Hazard Management Plan:

The Hazard Management Plan outlines the mitigation measures to be implemented for managing the suppression of deflagration and/or isolation of the source of deflagration. A written management system is developed for operating the facility to prevent or mitigate fires, deflagrations, and explosions from combustible particulates.

NFPA 652 outlines the topics to be covered in DHA and recommends a format to present the report.

PEC Consulting can help carry out a DHA Study for new or existing cement & lime plants and help the clients to develop a Hazard Management Plan.

This article was contributed by M. Dimah, Process Engineer for PEC Consulting, Mr. Dimah has a BS in Chemical Engineering from the University of Technology, Baghdad, Iraq, and a Master’s in Chemical Engineering from the Polytechnic University of Valencia, Valencia, Spain. He can be reached at  info@peccg.com 

Copyright © PENTA Engineering Corp. 10123 Corporate Square Dr, St Louis, MO 63132

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Cement kilns offer very favorable conditions for incinerating waste fuels. High temperatures, long residence times, an oxidizing atmosphere and alkaline environment, ash absorption by clinker, and high thermal inertia all favor the use of Alternative Fuels in a cement kiln. There are many benefits tied to the use of alternative fuels in cement kilns; nonetheless, the challenges connected with their application require careful evaluation.

What are Alternative Fuels?

Alternative fuels are non-traditional fuels that have calorific value and can be used as substitutes for conventional fuels such as coal, petroleum coke, oil and natural gas in clinker manufacturing. Typically, alternative fuels are waste or byproducts from industrial, agricultural and other processes. Traditionally, they are managed through landfills, treatment or incineration and come in liquid or solid form. Liquid Alternative Fuels include solvents, mineral waste oil from used lubricants, vegetable oil and various organic liquids. Solid Waste Fuels come in different forms: used tires, pre-treated industrial and municipal waste, sewage sludge and domestic waste, Refuse Derived fuels (RDF) from pulp, paper and cardboard residues; non-recyclable plastics; Packaging and Textile industry, biomass such as animal feed, contaminated wood and wood chips, waste wood, rice husk, sawdust and sewage sludge, and used carpets.

RDF FUEL USED BY A CEMENT PLANT

Advantages of using Alternative Fuels

The main advantages of using Alternative Fuels in the Cement Industry are economic and environmental. Cement producers strive to reduce their production costs. Fuel accounts for 20 to 25% of the production cost of cement and one viable option is the use of alternative fuels at a much lower cost than conventional fossil fuels. The use of waste fuels reduces the carbon footprint that results from using fossil fuels and therefore the overall environmental impact of cement manufacturing operations. It also extends the supply of fossil fuels and is a safe way of absorbing waste which otherwise would present a waste disposal problem. The favorable conditions in a cement kiln completely destroy the organic constituents and the inorganic constituents combine with the raw materials in the kiln and exit the kiln as part of the cement clinker without generating solid residues. Free lime in cement clinker acts as a good absorbent of hazardous elements. The cement kiln therefore is a natural incinerator that has a safe thermal environment for the use of alternative fuels. Use of alternative fuels in the cement kilns hence helps resolve air pollution problems by eliminating additional emissions which would have resulted from the incinerators while destroying the wastes.

Challenges & Limitations

Consistency of the chemistry and continuous availability are two major considerations in the use of Alternative Fuels. All alternative and derived fuels are generated at sources outside the control of cement manufacturers. Therefore, there are always some limitations on the availability of consistent quality alternative fuels in adequate quantities. The suitability of Alternative Fuels for use in the cement manufacturing process, effects on plant operation, product and environment need to be studied and established before the alternative fuel is selected. The composition of the Alternative Fuel and its availability will determine the extent to which it can be used.

RDF FUEL USED BY A CEMENT PLANT

Invariably, all alternative fuels require pretreatment prior to introducing them in the kiln or precalciner. Processing an Alternative Fuel may involve significant capital investment. Modifications to the existing plant equipment and the creation of new infrastructure for the intended use of the alternative fuel will be required. For instance, feeding whole tires requires a complex system and considerable space for implementation. In addition, converting from the use of conventional fuels to alternative fuels will call for adjustments to operating parameters, raw mix design, etc.

• Safety

Safety aspects related to alternative fuels depend on the type of fuel. Safety related issues mainly include handling and storage of fuels that emanate odors or are hazardous wastes. The selection of appropriate feeding points depending on the characteristics of the alternative fuel is also a safety consideration.

• Emissions and Environmental considerations

The use of hazardous waste as an alternative fuel in cement kilns is regulated by local environmental regulations for the incineration of waste. Emissions of air polluting compounds need to be addressed while considering use of alternative fuels in the cement manufacturing process. Emissions of Carbon monoxide, Sulphur dioxide, Nitrogen oxides, Hydrogen chloride, heavy metals such as mercury, lead and cadmium, Dioxins and Furans are major concerns. They are to be controlled below prevailing emission norms irrespective of the fact that whether the manufacturing process uses traditional fuels or alternative fuels. However, this can be achieved with controlled inputs, optimized and stable operation and if required with the installation of a kiln gas by-pass system. Cement kilns fired with conventional fossil fuel or with alternative fuels of all types can meet stipulated emission limit.

• What PEC Consulting can do?

Evaluate the suitability of Alternative Fuels. Evaluate the impact on the environment and develop concepts for mitigation measures. Recommend modifications to the existing kiln system for adaptation to the Alternative Fuel. Develop the CapEx and arrangement drawings. If the project is viable, PEC Consulting can subsequently develop the engineering for handling, processing and firing of the fuels into the kiln.

USED TYRES

The main contributor to this article was Jagrut Upadhyay, Senior Process Consultant at PEC Consulting Group.  Jagrut has a Bachelor of Science in Chemical Engineering, D.D. Institute of Technology, Gujarat University, India

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Fig 1. Cement Plant Layout

Prior to starting work on general arrangement drawings, the Owner agrees to a set of codes and design criteria that will govern the design of the new plant. Another key component is a survey of the area, which is especially important for a Brownfield plant expansion.

The GA review should start in the conceptual planning stages to assure an optimum and economical equipment arrangement.

Stairs provide the primary access to floors, platforms, walkways and equipment. Equipment located more than 2 meters above floor level should be provided with stairs and a platform for access. Ladders are not used except where space is limited. It is also acceptable to use a ladder to access nuisance dust filters or some instruments to which stair access is not practical.

Layouts should provide a minimum 1 meter clearance for walkway areas and maintenance access around equipment. Some equipment requires additional space for maintenance; i.e., removal of components. Standard mandatory height clearance in access platforms need to be at least 2.2 meters minimum in all areas.

Fig 2. Belt Conveyor Arrangement with Platform Accessible by Stairs

The optimization of conveying equipment to minimize its length needs to be done without compromising design parameters. Several factors that should be reviewed include the air gravity conveyor’s slope angle, the conveyor’s load angle, speed and radius, chute angles, apron feeder’s load angles, etc.

Fig 3. Belt Conveyor Loading, Transport, and Discharge Arrangement

Various configurations of material transfer chutes are used in plant design. Considerations for chute designs should include the type and characteristics of the material handled such as particle size, moisture content, flow characteristics, and abrasiveness. Chute slope angles are specified in the Design Criteria and shall be steep enough for material to flow by gravity. Chutes having long vertical drops shall be “laddered” down in order to control momentum.

Overhead hoist beams for equipment maintenance should be provided when the equipment is not accessible by mobile hoists or when the equipment cannot be handled manually. Maximum hoist loads must be indicated on the GAs. For example, equipment that should be provided with overhead hoists includes crushers, process fans, clinker breakers, bucket elevators, pumps, air compressors, equipment drives, etc. For large equipment like roller mills, a bridge crane should be provided.

Fig 4. Hoist to Service Bucket Elevator and Belt Conveyor Drives

Dust suppression systems should be considered where dust is generated. Proper dust suppression systems are normally used at emission points followed by adequate filter sizing, and material discharge. GAs are reviewed to ensure that dust suppression/collection parameters in the Design Criteria are being followed.

Fig 5. Dust Control System at Material Transfer

Special attention shall be provided to explosion vents. Design shall ensure that no structure or walkway is close to the expansion wave from an explosion.

The above directions are general guidelines, but revisions that have a greater scope may apply depending on regulations and the Owner’s specific requirements.

The general arrangement review ensures an optimum design and an efficient and cost-effective equipment layout, adequate accessibility to install and service equipment, and a safe and dust-free workplace.

The main contributor to this article was Pompeyo D. Ríos, Senior Consultant & Project Manager – at PEC Consulting Group. Mr. Ríos has a BS in Mechanical Engineering from the Universidad Metropolitana, Caracas, Venezuela, and a Master’s in Business Administration, Finance and Accounting from Regis University, Denver, CO

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Introduction:

The handling, preparation, storage, conveying and firing of ground solid fuel have inherent operating risks. Various qualities of coal are used as fuel. Due to the combustible properties of coal in general, safe handling is important during the entire process.

Accidents are mainly caused by the unintended release of energy caused by fire and explosion. A HAZOP study identifies situations where such release of energy may occur. It also identifies and estimates the potential severity of damage and recommends mitigation measures.

• Fuel handling and storage – Raw coal receiving, storage and handling.
• Fuel preparation – Raw coal grinding.
• Fuel conveying – Fine coal storage and conveying for an indirect firing system.
• Fuel conveying – Fine coal conveying for a direct firing system.

Methodology:

• The hazards of the coal grinding and firing process,
• Engineering and administrative controls applicable to the hazards and their interrelationships,
• Detection methods (Hydrocarbon detectors & gas analyzers) and continuous process monitoring,
• Consequences of failure of engineering and administrative controls,
• Human factors affecting the operation,
• A qualitative evaluation of safety and health effects of failure of controls on employees,
• The identification of any previous incident which had a potential for catastrophic consequences.

Documentation:

• Layout and G A drawings
• Equipment lists
• Process flow sheets and Process and Instrument Diagrams
• List of Process control loops and Process and Safety Interlocks
• List of Instrumentation and Alarms and Process variables with all limits
• Operating procedures and work instructions for various modes of operation
• Maintenance procedures and work instructions
• Documentation on all auxiliary systems and Fire hydrant system
• Raw Coal and Fine Coal analysis
• Method to control bypassing the Interlocks and Alarms
• Hazardous Area Classification

Staffing:

Results:

• ensure that the coal grinding and firing system can be started, operated and shut down safely,
• recommend appropriate changes to the process design or its operation that increase safety or enhance operability,
• consider existing safety interfaces with operation software including installations such as the Coal mill baghouse, fine coal storage and dosing system, fuel firing systems, inertization systems, etc.,
• derive the recommendations and actions to eliminate potential occurrences identified as risks.

Report:

The main contributor to this Article was Jagrut Upadhyay, Senior Process Consultant at PEC Consulting Group in St. Louis.  Jagrut has a Bachelor of Science Degree in Chemical Engineering, from the D.D. Institute of Technology, Gujarat University, India

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CEMENT IMPORT TERMINAL SCOPING STUDY

For the implementation of a new Cement Import Terminal, the best practice begins with hiring an experienced consultant to perform a Feasibility Study.  As a preliminary step, prior to beginning the feasibility study, a scoping study should be executed.  The Scoping Study will examine the fundamental aspects to the project.

The Scoping Study should focus on:

• Preliminary Communications with Port Authority and Government Agencies
• Permitting
• Preliminary FOB Cement FOB Pricing for Region and Availability
• Examination of Possible Site/s location/s
• Preliminary Project CapEx, OpEx, Simple Economic Analysis
• Preliminary Conceptual Designs
• Preliminary Examination of Infrastructure and Logistics
• Social and Environmental hurdles 
• Market Study (if applicable)

The Feasibility will advance elements of the Scoping Study and will additionally cover:

• Source pricing to Cement Supply and Transport 
• Obtaining bids from Vendors and Contractors
• Develop Design Criteria, Basic Layouts and Specifications for the Port Facility terminal
• Project Schedule and Execution Strategy
• Risk Assessment
• ROI

The primary role of the Consultant will be to gather and analyze the data for the Study, while the Owner  takes an active role in advancing communications with all relevant stakeholders and consultants, which may include  the following:

• Port Authority
• Local Government Agencies
• Consultants
• Legal Counsel
• Vendors/Contractors
• Cement Suppliers
• Transport Companies
• Unions/Stevedores

FACILITY SIZING AND DESIGN FOR OPTIMIZATION

In order to optimize operations to improve margins per ton of cement, it’s important to understand all the variables.  These variables need to be examined and weighed against each other to determine the best facility type, size and level of automation.  The variables considered include:

• Cement Shipment Size
• Product Turnover
• Sizing of Unloading Equipment
• Storage Size Requirements
• Facility lot Size and Berth Capabilities
• Port Ship Size Limitations
• Port Fees
• Maintaining Separation of Deliveries
• CapEx, OpEx, and Desired Return on Investment
• Automation (CapEx) vs. Labor Costs (OpEx)
• Environmental Requirements
• Zoning Restrictions
• Any other variable that needs to be considered for the site

Cement Import Terminals Options

 Flat Storage Option

The Cement Flat Storage provides an excellent solution for a low-CapEx storage. Certain factors need to be considered and weighed to determine if a Flat Storage is desirable: 

• Labor costs
• Lease costs
• Availability of sufficient land area
• Lower CapEx is a requirement for project approval
• Compartmentalizing
• Flexibility with expanding capacity

Reclaim for Flat storage can be handled in several ways.  If labor costs are low, it would be preferable to have front loaders that feed a hopper and bucket elevator to fill the truck loadout bins.  In locations where labor costs are extremely high, there may be value in the installation of fluidized flooring.

Dome Storage Option

Domes provide a good solution for a fully automated operation.  There are various configurations that can be designed for specific operational needs.  The capital expenditure is expected to be higher than that of a flat storage, but there are benefits of a Dome Storage  such as:

• Large live storage capacity
• Full Automation
• Reduced labor costs
• Smaller footprint

In cases where multiple products are required or deliveries need to be kept separate, multiple domes or combination of dome and silos would need to be considered.

Silo Storage Option

Typically, a silo storage is a preferred method for dispersing product to local markets that cannot be accessed by large bulk carriers.  Silo storages are only seen along rivers and lakes where small 5-10kton barges are used for transporting from a production plant.  One of the benefits of this type of storage is that it takes up a very small footprint; however, the capital cost to build per ton of storage capacity is the highest.

Floating Storage

Converting an older bulk carrier into a floating storage is a low-cost storage option, however not all ports are warm to this concept. The ship unloader can be mounted on rails on the vessel deck and used to unload from the incoming vessel as well as to withdraw from the floating storage to the truck-loading bins on shore. Either a Handymax or Supramax ship could be converted and designed for a storage capacity of 40,000-50,000 metric tons in 5 or 6 compartments (holds). This is by far the most economical option. It’s important to begin early discussions with the local port authorities to discuss this option before making any investment. A permanent berthing space would need to be obtained from the Port Authority within a reasonable distance (300 m or less) from the truck loading bins on shore.

Unloading equipment

Bulk carriers can be unloaded through various methods.  The two preferred methods are by either screw or pneumatic conveying.  Typically, screw to belt is common on docksides where fixed equipment is allowed which represents an overall lower Operation cost to unloading.  Pneumatic is preferred in cases where the dock face is considered to be shared and unloaders, whether mobile or barge mounted, must be moved after unloading operations have been completed.

Some of the major considerations for ship unloader selection and design are:

• Reach requirements
• Rate of unloading
• Distance of transport
• Mobility needs

Ship unloading manufacturers can create custom solutions, however, it is important to understand that keeping the design as standard as possible offers cost savings to the project.

The main contributor to this article was Christian A. Benavides, Construction Technical Consultant at PEC Consulting Group LLC, St. Louis, Missouri, U.S.A.

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Most rotary kilns use solid fuels as the main heat source to produce cement clinker.

A training program should be developed and extensive training for coal mill system operators provided on a regular basis. Safety considerations, such as the prevention of fire or explosion are of utmost importance as is the knowledge of how to proceed under normal conditions. The training program should include the development of an operating manual which should be updated with new procedures as situations occur.

SAFETY ASPECTS

Solid Coal Unloading, Storage, and Reclaiming Areas

A major hazard associated with coal handling facilities is the possible formation of an explosive atmosphere originating from accumulation of methane and coal dust especially in enclosed areas or tunnels such as rail unloading facilities. Walls should be washed down frequently to prevent dust accumulation, and welding or electrical repair work should not be conducted in an enclosed area during unloading operations or if methane or coal dust is present. Smoking, open flames, and other potential ignition sources should be prohibited in any areas in which coal is being handled or processed.

Fires that start around the edges of coal storage piles should be removed with a front end loader, spread in a location away from the coal storage area, and allowed to cool. Water should NOT be sprayed on a smoldering coal pile. The degree of wetness in a coal storage pile is known to influence spontaneous heating.

Belt magnets and metal detectors on coal belts must always be operating properly. Pieces of metal can cause sparks or become overheated which can ignite a fire or initiate an explosion. Scrap metal in a coal mill is particularly dangerous during mill shut down or start up.

Coal Mill Operation

Fires or explosions most likely occur during startup and shutdown of a coal mill system. If a small amount of coal remains in the mill after it is shut down, it slowly increases in temperature. If the pulverized coal undergoes spontaneous heating and the coal mill is restarted with hot embers present, an explosion or fire is possible. Although this does not happen often, the chances increase when a coal mill is frequently shut down and then restarted.

A coal mill system that goes down, particularly under load, must be treated with extreme caution. In several cases, fires or explosions have occurred when an employee opened an inspection door. Air admitted to the system allows oxygen to reach a smoldering pile of pulverized coal that then ignites explosively. Also, an inrush of air may create a pulverized coal dust cloud that explodes.

Accumulations of Pulverized Coal Dust

All leaks, spills, and any accumulations of coal or coke dust must be cleaned up promptly around coal mill grinding and firing systems because of the potential for spontaneous combustion. Small piles or layers of coal or coke dust may spontaneously heat and start a fire.

Coal dust spills or leaks must be cleaned up or repaired as soon as it can be safely done. A potentially serious problem exists if coal dust is allowed to accumulate inside a building or enclosure, for example around an unloading facility or because of a leaking coal conveying line. If large accumulations of dust exist and a small explosion occurs, the dust build-up can be dispersed into the air as a result of the relatively minor first explosion and then produce a very large secondary explosion.

When coal is freshly pulverized, volatile gases such as methane can be released and the result is no longer a coal dust/air mixture but what is termed a hybrid mixture.

Coal Mill Temperatures

Coal mill hot air inlet temperatures should never be more than 600°F and the outlet temperature should not exceed 200°F on Raymond coal mills. If the flow of raw coal to the coal mill is interrupted for any reason (for example: plugging, failure of the coal feeder, etc.), the outlet temperature of the coal mill can quickly climb to dangerous levels. The risk of explosions or fires can be extreme when the coal mill inlet temperature increases to more than 600°F or the outlet temperature is more than 200°F.

Velocity in Ducts and Burner Pipes

Fuel efficiency would tend to dictate that the airflow should be varied as the coal feed rate varies. However, velocities in ducts or conveying lines must be at least 5000 fpm (25 meters per second), which has the practical effect of limiting how much the airflow can be varied without reducing the velocity below safe levels.

Burner pipes must be designed to maintain a minimum tip velocity of 8500 fpm (45 meters per second). Velocities less than 8500 fpm substantially increase the risk of the coal flame propagating into the burner pipe and potentially through the conveying lines to the coal mill causing substantial damage to the equipment.

COMMON CAUSES OF FIRES OR EXPLOSIONS IN COAL SYSTEMS

Combustible gases

Coal may contain trace amounts of gases such as methane. When coal is handled, it can release some of these gases. Methane concentrations in coal unloading systems, particularly in enclosed areas such as tunnels, elevator housings, and bins can accumulate to dangerous concentrations. Smoking, cutting, welding, or any source of open flame or high heat (such as a light bulb that could break and result in an electrical arc) should be strictly prohibited in coal handling areas.

Spontaneous combustion

Oxidation at the surface of a coal particle –which is most active when the coal has been freshly pulverized – and condensation of water onto the coal are reactions causing heat that can lead to spontaneous combustion.

The ease with which coal will oxidize is extremely variable. The total exposed surface area is important because, when more fresh surface is exposed, oxygen has a higher chance of uniting with the coal with the result that the total heat liberated in a given time for a given weight of coal will be substantially greater. When water condenses, it releases heat which can be a significant factor in the initial increase in temperature of a coal dust mass. However, oxidation is how the coal ultimately reaches its ignition temperature.

Spontaneous combustion is primarily oxidation occurring on a fresh surface of a coal particle. The rate of oxidation increases rapidly as the temperature increases. For some coals a temperature increase of 20°F (10°C) can double the rate of oxidation. If heating from oxidation occurs in a mass of coal dust, the ignition temperature of the coal can be reached quickly if enough oxygen is present.

Debris in the coal mill

Every effort must be made to prevent scrap metal and other spark producing debris to enter the coal mill system. Pieces of metal in the coal mill can also be heated to temperatures high enough to start a fire or explosion by being in the mill while it is in operation.

Solid fuel that spills over the bowl and into the area below the bowl can cause a fire since it is exposed to the hot drying air entering the coal mill. The coal mill scrapers will usually sweep the fuel pieces around to the debris chute and discharge them; however, a fire is likely to occur if a coal buildup occurs at the hot air inlet to the mill.

Hot surfaces

Hot surfaces such as hot bearings, cutting, or welding can start a coal dust fire or explosion. Any unusual temperatures must be reported immediately and steps taken to solve the problem. Cutting and welding around the coal mill system should only be done under strict supervision by qualified personnel. The system should be inerted or washed down with water prior to cutting or welding.

Coal Dust Explosions

A coal dust explosion will occur if the following three conditions exist:

1. The concentration of coal dust in the gas mixture is within the explosion limits.
2. The oxygen content in the gas mixture is sufficient for an explosion.
3. There is sufficient thermal energy to initiate an explosion.

Theoretically, the absence of one of any one of these three factors would be enough to prevent a coal dust explosion. However, it is preferable to eliminate two or, possibly, all three factors.

The thermal energy required for initiating an explosion could originate from several sources:

1. Spontaneous combustion or self-heating of the coal.
2. Overheating of the coal by hot gases used for drying that are too hot.
3. Overheated machine parts, such as hot bearings.
4. Metal entering the coal mill with the coal can cause sparks or become hot enough to start a fire or explosion.

EMERGENCY CONSIDERATIONS

On a coal grinding and firing system, maintenance work or inspections that require opening equipment should only be performed when given specific instructions and under the direct supervision of authorized personnel. Cutting or welding around or on a coal firing system can result in fires and explosions. Opening an inspection door on a coal grinding system can provide oxygen to smoldering, powdered coal and result in fires or explosions. Use extreme caution when opening an inspection door. Do not poke or disturb any coal accumulations if there is any evidence of heat, smoke, or glowing embers. Allow the system to cool further and then check again as necessary. When you are convinced everything is OK, remove any accumulations in small amounts. Before working on or around coal firing systems, the system must be inerted or washed down with water to be sure powdered coal can not ignite.

This article was contributed by Gerald L. Young, Senior Consultant at PEC Consulting Group LLC. Jerry has authored or co-authored more than 25 papers that cover cement manufacturing and emissions control. He has conducted cement plant audits and feasibility studies for new cement plants and plant expansions. He has a BSc degree in Chemistry from Missouri University of Science and Technology, Rolla, MO, and a Master’s degree in Management from the University of Redlands, CA.

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Utilizing used equipment to build a cement plant is not always economically attractive as it may appear at face value. Although the cost of the equipment appears to be favorable, there are many factors which need to be considered in the capital cost analysis (CapEx). In most cases, the equipment is sold in place at the plant being dismantled. This is true with most major process equipment. The buyer carries the cost of dismantling, transporting, and reassembling the equipment. The buyer is also responsible for all Customs imposed export and import procedures, duties and taxes.

The analysis of the feasibility of utilizing used equipment should consider the following points:

A. FINANCIAL CHALLENGES

1. The entire risk is on the Owner

Most equipment is sold on an as-is where-is basis; hence, a detailed inspection and assessment of the equipment is necessary. The seller will not provide guarantees of any kind (capacity, completeness, equipment condition warranties, etc.). The risk entirely rests with the Owner and it is high considering the ratio of equipment cost to overall investment costs, which amount to hundreds of millions of US Dollars.

2. Performance guarantees and technical support

No one, including the original OEM, will likely be prepared to provide a performance guarantee in terms of capacity, energy consumption, or quality of the equipment as is normally obtained with new equipment.

3. Schedule risks

More than likely, not all necessary plant components will be available with the existing used plant. Therefore, new parts have to be identified, ordered and then assembled. In this case, there is no advantage on the project schedule compared to using all new equipment. Production delays due to faulty equipment will result in projected cash flows not materializing because of implementation issues which may counter the savings gained from the procurement of used equipment.

B. TECHNICAL CHALLENGES

1. Capacity of the plant

Capacities of the available used equipment will dictate the new plant capacity rather than the preferred capacity according to the determination of the feasibility study.

Unless all the used equipment comes from a single process line sized for the capacity of the new line and utilizing similar raw materials and fuels, matching the equipment to the new site may require significant modifications. Buying individual equipment is even more challenging and requires a highly skilled process engineer to match equipment to requirements. Process flow sheets and equipment lists need to be developed to prepare a “shopping list” of complementary equipment. If a complete line (raw mill through clinker cooler discharge) is identified, the process engineer needs to identify the modifications required to adjust for the conditions of the new site, such as the difference in elevation which has an effect on the amount of process gases handled.

2. System configuration

Different systems such as raw grinding, coal grinding, pyro-processing system, storage and material handling systems, may or may not be the Owner’s optimal choice for the new plant. The Owner will have to make do with what is available.

3. Electrical Systems & Controls

Highly qualified electrical and control engineers need to evaluate the equipment and determine suitability for the new site conditions. If applicable, it is likely that a power distribution system will still need to be designed and new instrumentation and control system will be required for the new plant. If the source of the equipment has different voltage and frequency ratings, it is most likely that the electrical drives will not be usable as the equipment would have been designed for different motor speeds.

4. Specific transportable equipment

While heavy equipment is economical to transport due to its high value, equipment such as cyclones, bins, process ducts is not economically transportable even if in good condition. Such equipment is made of thin plates susceptible to damage. Furthermore, the transport costs are based on volume rather than weight and therefore the costs will be disproportionately high.

5. Documentation

Documentation is one of the biggest issues with the concept of building a plant with used equipment. Documentation is very important for relocation, reassembly, and also for future maintenance. Generally, the documentation is unorganized and incomplete which becomes a challenge during reconstruction. Specifically, the structural drawings designed for equipment loads, if available, need to be reexamined. More than likely, the soil conditions and wind and earthquake loads at the new location are different and therefore the foundations and structures will have to be redesigned. The availability of equipment drawings is critical to the success of the project. If equipment drawings are not available, it will be necessary to request drawings from the OEMs to avoid the tedious work of taking dimensions in the field.

6. Dismantling of equipment

Once used equipment is located, a team of engineers with extensive experience in equipment maintenance needs to be deployed to the site to evaluate its condition. Expertise in rotary kilns, mills, process fans, coolers and other major cement plant equipment is required to do this type of evaluation. It is rare to find used equipment that was shut down and maintained in good condition. Most companies quit doing maintenance on equipment if they know it will be shut down. If the equipment is idle for a long period of time, certain components will deteriorate. In this case, considerable effort and planning are required to ship equipment to maintenance shops to be overhauled. A skilled team of professionals should be in charge of dismantling the equipment. Match-marking and adding identification to facilitate reassembly, which is best done by the same team. The cost of dismantling depends on the country where the used equipment is located, which is most likely in western countries where costs are high. Often the equipment is still in place which will require hiring a local contractor to disassemble and ship to the new location. A company representative will need to be present to make sure this is done correctly. Steel structures cost more to disassemble and reassemble compared to new fabricated structural steel sourced in Asia.

7. Problems with identifying missing components

Ancillary Equipment: Unless a complete cement line is found that matches the desired production rate and elevation of the new site, purchasing individual equipment is “hit and miss”. Some equipment can be found, but others will have to be purchased new. Usually auxiliary equipment is not worth the effort to purchase used. This is technically the most difficult aspect of relocation projects. Several components could be missing or damaged during the shut-down period. Initial inspection or due diligence generally covers an overall visual inspection and does not include detailed inspection of each and every equipment and its internals. In many cases, parts are proprietary items that need to be procured from the OEMs. Such spares are expensive and will be disproportionate in cost to the value of the purchase price of the used equipment.

8. Transit damage

Transit damage risk will be carried by the buyer since the dismantling and packaging will be undertaken by the buyer’s contractor.

C. CONCLUSION

Transportable equipment is best limited to major heavy equipment. Parts made of thin plates or embedded in the concrete such as kiln base plates are either likely to be damaged or not worth transporting. Kiln shells with drive and support stations, mills, and large fans are items that may be economical to transport and reassemble.

When a cost is assigned to meet the challenges and risks mentioned above, the overall relocation project costs are generally higher than buying new equipment. However, there are always exceptions to the rule.

This article was contributed by F.M. Benavides, N. Jayaraman, and K.R. Schweigert for PEC Consulting.

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HOMOGENEOUS GEOLOGICAL FORMATIONS

• Typical Method in Open Pit Quarries:

  • A quarry rotary air drill is used to find either the top (hanging wall) or bottom (foot wall) of the deposit between core holes.

  •  Samples are taken at intervals necessary to locate the quality by simply blowing out the chips at specific intervals and placing them in sample bags for testing.
  • This can be done in advance of final drilling and blasting to make sure enough overburden is removed or that the mine does not go too deep and below the foot wall.

• Typical Method in Underground Mining:

In underground mining, the thickness of the quality seam will determine the number of lifts or layers that can be removed at one time:

• • For thicknesses of up to 10 meters, a single heading will remove all the limestone from the seam.
  • Thicker seams will require multiple lifts to remove all of the quality stone.
  • There may be a heading to remove the first layer followed by removal of the bench.
  • Sampling of the initial heading is usually done by taking samples of the top, middle and bottom of the mine face.  This is performed after the heading is cleaned out and scaling has removed any loose stone from the top and face.
  • Bench sampling can be done using the same method as the open pit quarry using the rotary air drill chip samples.

COMPLEX GEOLOGIC FORMATIONS

• Not only are you looking for head and foot wall but also geologic structures that can cause contamination in the stone.  For instance, in an anticlinal fold, the upper portion of the reserve is in tension and the bottom is in compression.  The upper portion is prone to cracks and crevices that fill with contamination from the layers above.  In faulting, the area displaced can contain similar contamination.  If the deposit is broken up in blocks, additional testing will need to be done to determine the boundaries of the good limestone.
• Sampling and testing in the mine will need to increase.  Chip samples along with face samples will be used to locate the areas of good quality stone.  Sometimes a geologist will need to visit the mine on a regular basis to assist the mine personnel in interpreting the location of quality stone.

Quality of the Limestone Feeding a Cement Plant:

• These types of limestone reserves require further testing at the cement plant prior to the raw material blending process.
• Sampling and testing must be continuous to meet certain chemical requirements.  Based upon the quality of the limestone delivered to the plant, high grade limestone, silica, alumina and iron are added to the mix to meet certain chemical properties for the formation of clinker in the kiln.
• To ensure proper mixing, the mixture is conveyed to a specially designed homogenizing silo to further blend the raw meal prior to clinkerization.
•  Most cement plants blend raw materials using an on-line analyzer.  The on-line analysis is imperative for the production of good quality clinker.

Quality of the Limestone Feeding a Lime Plant:

• In the process of converting high calcium limestone into calcium oxide in a lime kiln, the rule of thumb to follow is “the more complicated the deposit, the more sampling and testing is needed prior to the kiln”.
• There is not a whole lot that can be done with the limestone once it is fed to the kiln.
• Unlike cement, there is usually no blending system to improve the mix.  An on-line analyzer may be employed to divert low quality limestone to waste in the crushing and screening area.

The main contributor to this article was Ken Schweigert, Senior Process Consultant at PEC Consulting Group.

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What Can PEC Consulting do?

Elements of Training

Handouts and Course Material:

• Explanation on details of the subject.
• Engineering, Design and Safety features of the equipment and Process safety.
• Operational aspects.
• Theoretical and Calculation elements.

Classroom Training and Group Discussion:

• Delivering lectures and presentations.
• Sharing Knowledge and Experience.
• Discussion on critical aspects of plant operation.
• Understanding the importance and inference of process parameters.
• Analysis of process parameters.
• Understanding Process control logics and Equipment Safety logics and their consequences.

On field or In-plant Training:

• Equipment inspection.
• Information on “What to look for”.
• Physical inspection provides information on equipment conditions.
• Practical experience of process parameters measurements.
• Enhanced accuracy of measurements.
• Understanding the importance of maintenance and its effects on process parameters.

Summary

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Understanding the market landscape is one of the most important prerequisites in strategic decision-making. More often than not, the key to competing and outperforming competitors lies in a better understanding of the key growth areas and market trends. A rigorous market study helps to support strategy development by providing valuable insights on:

• Industry structure and trends
• Market segments, size and growth potential
• Demand driver dynamics and their implications
• Competitive landscape – customers, competitors, suppliers
• Service, product differentiation and branding
• Market entry modes

A good market analysis comprises at least 5 important parts.  

Part 1: Objectives of the Research

The researcher has to provide the rationale for undertaking the study. The tasks associated are:

• Scope of work
  • e.g., prepare for new product introduction, evaluate competitors, look for new market opportunities, etc.
• Application of the information obtained in the Market Study
  • e.g., support a marketing plan, measure and evaluate previous marketing decision, competitive research program, etc.

Part 2: Description of the Market

• General Description
  • A summary of the market being studied
• Target Market(s)
  • Geographic areas selected for analysis
  • Population analyzed (e.g., demographics, psychographics, behaviors)
  • Benefits seeked (i.e., what points-of-pain or problems are being solved)
  • Factors affecting purchase or use decision
  • Attitudes about the products/services currently offered
  • Product use
• Products and Services that appeal to the target market
  • In general terms (not particular brands) what is currently appealing to this market
  • What types of products/services may appeal to this market (i.e., what is used now to solve the problem).

Part 3: Market Metrics

Included in this section are:

• Size estimates (current and future) for:
  • Overall market
    • Current size
    • Potential size
    • Actual penetration of current products/service within the total market
  • Individual market segments
    • Current size
    • Potential size
    • Actual penetration of current products/service within the total market
• Growth estimates (current and future) for:
  • Overall market
  • Individual market segments
  • Relation to GDP growth

Part 4: Competitive Analysis

• Summary of Current Competitors
  • Listing by market share ranking (by each target market if possible)
• Current Competitors – full analysis of top competitors including:
  • Products & Services (e.g., description, uniqueness, pricing, etc.)
  • Market share
  • Current customers
  • Positioning and promotion strategies
  • Partnerships/Alliances/Distributors
  • Recent news
    • It is extremely important to focus attention on the SWOT section of this report. While most other information in this report can be gleaned from company and secondary materials, much of what appears in the SWOT section is based on the researcher’s own perceptions of the competitor based on the information collected. Consequently, this is often one of the hardest areas of the report to write.
  • SWOT Analysis – Strengths, Weaknesses, Opportunities & Threats
  • And other information (as: general company information, summary of business, business overview, recent news/developments, financial and market share analysis, marketing, and other issues like technology capability or partnership arrangements)
• Potential Competitors
  • Explanation (though not as detailed as Current Competitors) on who they are or maybe and why they are seen as potential competitors

Part 5: Additional Information

This section of the market study includes other information including

• Extraneous Variables
  • Discuss factors that may affect this market (e.g., technological, social, governmental, competitive, etc.)
• Market Trends
  • What is expected to happen

This article was contributed by Lucia Martínez, Research Assistant at PEC Consulting Group.  

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