Sludge Removal by Wastewater Treatment Clarifiers

As the video below points out, dirty wastewater enters from the center of the clarifier and very slowly makes its way towards the outside where the water spills over the weir. During that retention period, the solids have enough time to settle to the bottom, where they're later picked up as sludge, and the clarified, or cleaner water, spills out along the edge. Clarifiers are made in many different shapes and sizes all work on basically the same principle. The sludge is then processed to remove water, be neutralized biologically, and reduce the levels of pathogenic organisms.

Beneficial uses of treated municipal wastewater sludges on land include agriculture and silviculture uses; application to parks, golf courses, and public lands; use in reclaiming low quality or spoiled lands; and use as landfill cover or fill material. Disposal on land includes landfilling and permanent storage of dewatered sludge or sludge incinerator ash in lagoons or piles.

Pultruded FRP Composites as an Alternate to Steel

Pultruded FRP suspendible roof structure.

Pultrusion is a term that describes a manufacturing process for producing continuous lengths of FRP (fiberglass reinforced plastic) where reinforcing fibers are saturated with resin and pulled through a heated die to form a part. The result is a straight, constant cross-section profiles similar to standard steel shapes.

Pultruded composite sections can be used to design and install lightweight, corrosion-resistant and electrically non-conductive alternatives to steel structures, particularly where speed and ease of construction are important. Pultruded FRP has performance characteristics similar to other construction metals, but unlike steel, it is EM/RF transparent and doesn’t disrupt equipment signals.

Benefits:

• Pound-for-pound stronger than steel.
• Comparable structural performance to other metals such as aluminum, but without the conductivity, corrosion or impact limitations. 
• Can be painted, coated or pigmented during manufacture for little-to-no maintenance in highly aggressive environments
• Designed for UV performance
• Enables rapid cleaning with aggressive solvents at high pressures
• Meets industry requirements for durability, smoothness, absorbency, color, corrosion resistance and washability

Typical Uses:

• Structural profiles and plates
• Decking and planking
• Platforms, stairs, ladders and cages
• Handrails, guarding and kickplates
• Grating and gridmesh
• Bridge components
• Structural building panels
• Sheet piling and round pile
• Containment systems
• Ballistic and storm panels
• Connection hardware

Pultruded FRP composites are ideal for structural elements where a strong, lightweight material is needed; corrosion is a concern for steel or other metals; RF permeability is needed; and low thermal or electrical conductivity is important.

To discuss using pultruded FRP composites on your next project, contact Process Systems Design by calling (410) 861-6437 or visit https://www.processsystemsdesign.com.

Consider the Possibility of Constituent By-products in Your Process Heating System

It is estimated that over 7,000 TBtu/year (Trillion British Thermal Units) of energy is used for process heating by the manufacturing sector in the United States. This energy is in the form of fuels—mostly natural gas with some coal or other fuels—and steam generated using fuels such as natural gas, coal, by-product fuels, and some others.

Combustion of these fuels results in the release of heat, which is used for process heating, and in the generation of combustion products that are discharged from the heating system. All major US industries use heating equipment such as furnaces, ovens, heaters, kilns, and dryers. The hot exhaust gases from this equipment, after providing the necessary process heat, are discharged into the atmosphere through stacks.  The temperature of the exhaust gases discharged into the atmosphere from heating equipment depends on the process temperature and whether a waste heat recovery (WHR) system is used to reduce the exhaust gas temperature. The temperature of discharged gases varies from as low as 200°F to as high as 3000°F.

Combustion products themselves, generated from well-designed and well-operated burners using gaseous and light liquid fuels, are relatively clean and do not contain particles or condensable components that may require “cleanup” before discharge into the atmosphere. However, during the heating process, the combustion products may react or mix with the product being heated and may pick up constituents such as reactive gases, liquid vapors, volatiles from low-melting-temperature solid materials, particulates, condensable materials, and the like.

Some or all of these constituents, particularly at high temperatures, may react with materials used in the construction of downstream heat WHR equipment and create significant problems.

Potential Problems:

• Chemical reaction of exhaust gases and their solid or vapor content with the materials used in the WHR equipment.
• Deposit of particulates in or on surfaces of WHR equipment.
• Condensation of organics such as tars and inorganic vapors such as zinc oxides and boron on heat exchanger surfaces.
• Erosion of heat exchanger components by the solids in the exhaust gases. 

Many of these problems are compounded by the high temperature of the exhaust gases, uneven flow patterns of the hot gases inside the heat exchanger, and operating variations such as frequent heating and cooling of the heat exchanger.

Dealing with industrial heating processes in which the exhaust gases are at high temperatures, or that contain all reactive constituents, or can be considered as harsh or contaminated are important considerations for the process engineer.  If unsure, professional advice from knowledgeable consultants should be sought to optimize the heating system. To discuss any process heating requirement you may have, contact Process Systems & Design at https://www.processsystemsdesign.com or by calling (410) 861-6437.

Improving Fan System Performance: A Sourcebook for Industry

Typical Fan System

Fans are widely used in industrial and commercial applications. From shop ventilation to material handling to boiler applications, fans are critical for process support and human health.

In manufacturing, fan reliability is critical to plant operation. For example, where fans serve material handling applications, fan failure will immediately create a process stoppage. In industrial ventilation applications, fan failure will often force a process to be shut down (although there is often enough time to bring the process to an orderly stoppage). Even in heating and cooling applications, fan operation is essential to maintain a productive work environment. Fan failure leads to conditions in which worker productivity and product quality declines. This is especially true for some production applications in which air cleanliness is critical to minimizing production defects (for example, plastics injection molding and electronic component manufacturing).

The document below, developed by the US DOE and the Air Movement and Control Association International provides wide ranging information about fans used in industry. You can also download your own full copy of this document from here.

Improving Fan System Performance: A Sourcebook for Industry from Process Systems & Design

Unique Rotating Dryer Design is Perfect for Forest and Agricultural Products

The exclusive technology DRYER ONE, developed by Belgium company Technic One, enables the precise drying and processing of a large range of forest and agricultural products, in addition to the recovery of waste materials.

It operates bu loading the material to be dried onto a rotating plate through which passes a hot air flow. After a 360° rotation, the partially dried material is transferred onto a second plate where it is rotated again, thereby completing the drying process. Various control processes are used to ensure the good working and to reach the desired moisture content of the product.

Typical drying applications are wood waste, wood shavings, sawdust, maize, coffee grounds, brewer's grain, corn, soy, seeds, rice, and barley.

A visual understanding of the dryer operation is explained below:

1. IN - The lower rotating plate is loaded with the material to be dried.
2. LOWER LEVEL DRYING - The material is rotated by 360°.
3. UP - The material to be dried is transferred towards the upper plate by a bucket elevator or a vertical screw conveyor.
4. HIGHER LEVEL DRYING - The material is rotated 360° by the upper rotating plate, moving in the opposite direction to that of the lower level plate. This exclusive technology ensures better distribution of heat and greater efficiency than other hot air drying techniques.
5. OUT - The dried material is exited towards the packaging or storage area.
6. HOT AIR FLOW - The hot air is sucked from the top to the bottom creating a counter current. It successively crosses the higher and lower level plates.
7. RETRIEVAL AND EXPULSION OF AIR SATURATED WITH MOISTURE - After passing through the two plates the saturated air is pushed upwards for expulsion. If necessary, filters suitable for residual particles can be installed at the final stage of the process.

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1. Hot water is brought from a cogeneration unit.
2. The heat exchanger transfers the heat from the hot water into ambient air. The heated air is then drawn into the dryer.
3. Cooled water evacuation after exchange.
4. The incoming air is dry and hot (60-90°C)(140-194°F).
5. The reverse counter-current air flow (moving from the top to the bottom of the dryer) presses through material laying on the rotating plates, this largely prevents dust dispersion.
6. The outgoing cooled air (25-30°C)(77-86°F), almost completely saturated with moisture, is evacuated via the central chimney.
7. The first rotating plate gradually and partially evaporates the moisture.
8. Material is transferred from the lower plate to the higher plate via a bucket elevator or a vertical screw conveyor. During the transfer, the material is rotated and mixed, providing better quality and even drying.
9. The second rotating plate completes the drying process and allows the hot air to absorb residual moisture.

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1. ROTATION OF MATERIAL - Each drying plate is equipped with a screw conveyor which thoroughly rotates and mixes the material to be dried. This process provides more even and better quality drying.
2. ROTATION SYSTEM - Each rotating plate is driven by a gearmotor, which ensures a constant rotation speed with complete reliability.
3. PLATE COVERINGS - The rotating plates are covered with a highly resistant synthetic grooved surface or stainless steel perforated sheeting. The load loss of the material to be dried is lower than that of the covering, leading to better diffusion of the hot air flow across the whole surface. Moisture can be extracted gradually, without thermal shock. The more even humidity level is one of the main advantages of DRYER ONE™. The coverings can easily and quickly be replaced.
4. ROTATING METAL PLATES - The rotating plates have a stainless steel grated structure with a planarity much greater than that of conveyor belts. They have high resistance to load stress and corrosion. The grated structure is divided into segments of equal size, making it much easier to carry out maintenance work or replacements in the space of just a few minutes.

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For more information on the Dryer One system, contact Process Systems & Design by calling (410) 861-6437 or visiting https://www.processsystemsdesign.com.

Biomass for Power and Heat Generation

There are many potential advantages to using biomass instead of fossil fuels for meeting energy needs. Specific benefits depend upon the intended use and fuel source, but often include: greenhouse gas and other air pollutant reductions, energy cost savings, local economic development, waste reduction, and the security of a domestic fuel supply. In addition, biomass is more flexible (e.g., can generate both power and heat) and reliable (as a non-intermittent resource) as an energy option than many other sources of renewable energy.

Biomass fuels are typically used most efficiently and beneficially when generating both power and heat through CHP (combined heat and power). CHP, also known as cogeneration, is the simultaneous production of electricity and heat from a single fuel source, such as biomass/biogas, natural gas, coal, or oil. CHP provides:

• Distributed generation of electrical and/or mechanical power.
• Waste-heat recovery for heating, cooling, or process applications.
• Seamless system integration for a variety of technologies, thermal applications, and fuel types into existing building infrastructure.

CHP is not a single technology, but an integrated energy system that can be modified depending on the needs of the energy end user. The hallmark of all well-designed CHP systems is an increase in the efficiency of fuel use. By using waste heat recovery technology to capture a significant proportion of heat created as a byproduct in electricity generation, CHP systems typically achieve total system efficiencies of 60 to 80 percent for producing electricity and thermal energy. These efficiency gains improve the economics of using biomass fuels, as well as produce other environmental benefits. More than 60 percent of current biomass-powered electricity generation in the United States is in the form of CHP.

The industrial sector currently produces both steam or hot water and electricity from biomass in CHP facilities in the paper, chemical, wood products, and food-processing industries. These industries are major users of biomass fuels; utilizing the heat and steam in their processes can improve energy efficiency by more than 35 percent. The biggest industrial user of bioenergy is the forest products industry, which consumes 85 percent of all wood waste used for energy in the United States. Manufacturing plants that utilize forest products can typically generate more than half of their own energy from woody waste products and other renewable sources of fuel (e.g., wood chips, black liquor).

Most of the electricity, heat, and steam produced by industrial facilities are consumed on site; however, some manufacturers that produce more electricity than they need on site sell excess power to the grid. Wider use of biomass resources will directly benefit many companies that generate more residues (e.g., wood or processing wastes) than they can use internally. New markets for these excess materials may support business expansion as the residues are purchased for energy generation purposes or new profit centers of renewable energy production may diversify and support the core business of these companies.

Biomass Feedstocks

The success of any biomass-fueled CHP project is heavily dependent on the availability of a suitable biomass feedstock. Biomass feedstocks are widely available in both rural and urban settings and can include:

Rural Resources:

• Forest residues and wood wastes
• Crop residues Energy crops Manure biogas

Urban Resources:

• Urban wood waste
• Wastewater treatment biogas
• Municipal solid waste (MSW) and landfill gas (LFG)
• Food processing residue

Feedstocks vary widely in their sources and fuel characteristics and therefore vary in typical considerations for their utilization. Various biomass resources can require different approaches to collection, storage, and transportation, as well as different considerations regarding the conversion process and power generation technology that they would most effectively fuel.

Process Systems & Design welcomes your inquiries in to biomass processing. With years of engineering experience in this field, PS&D is an outstanding engineering partner for any biomass-to-energy conversion process.

Contact Process Systems & Design by visiting http://www.processsystemsdesign.com or call (410) 861-6437.

Process Systems & Design: A Wide Range of Engineering Capabilities

Process Systems & Design, Inc. Capabilities from Process Systems & Design