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Vacuum For Landfill Gas Extraction

Process Overview 

The organic waste in landfills is covered and compressed by heavy equipment to create an anaerobic condition, a biological decomposition process that does not involve oxygen and breaks down organic matter. HOFFMAN & LAMSON blowers extract the byproducts from the anaerobic digestion process. Vacuum is applied to a perforated piping system to control and withdraw the resulting gas. Primarily comprised of 50-70% methane (CH4) and 25-50% carbon dioxide (CO2), this gas is both hazardous and potentially useful. If the gas remains in the landfill, then explosions can occur. If leaked into the atmosphere, it contributes to smog as a hazardous gas known as volatile organic compounds (VOC). 

Landfills in the United States must estimate the quantity of non-methane organic compounds emitted to the atmosphere. If these landfill emissions exceed 50 tons per year, then they are required to contain and clean the gas to remove the non-methane organic compounds. Usually, the methane gas is burned off or flared, which requires a vacuum producer and compressor to remove gas from the ground and feed into the flare. 

HOFFMAN & LAMSON blowers are the ideal solution because they are engineered to handle the pressures and flows typical for landfill gas flare system demands.

If economically feasible, the gas is cleaned to pipeline quality as “renewable natural gas” or “biomethane”. The gas can be added to the gas pipeline grid and mixed with natural gas. Additionally, the biomethane gas can be used to heat water or air or heat part of an industrial process. If compressed, biomethane can power internal combustion or fuel cell vehicles. 


Landfill Gas Extraction Process Overview

Hoffman & Lamson provides durable and cost-effective blowers/exhausters for landfill gas applications. These landfill gas solutions are reliable, safe, require limited maintenance and provide:

  • Heavy-duty cast iron construction 
  • Baked phenolic coatings for long equipment lifespan in harsh environments
  • Dynamically balanced rotor assemblies 
  • Backed by more than 115 years of engineering expertise 
  • Stainless steel options for H2S corrosion prevention 
  • MAX Seal for near-zero leakage mechanical seal upgrade

Hoffman & Lamson Designs Gas Booster System for North American Wastewater Treatment Facility

The team at Hoffman & Lamson was given the challenge of engineering a system that would clean and convert the gas for use in the CHP plant.

 

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Gas Boosting System For North American WWT Facility

HOFFMAN & LAMSON blowers/exhausters for landfill gas are flexible and allow variable flow capabilities with or without a variable frequency drive (VFD), which is critical for maintaining proper flow for combustion. Moreover, our blowers/exhausters are efficient and contribute to energy and cost-savings with our custom-engineered configurations.

Additionally, our blowers/exhausters are virtually maintenance-free because of no wearing parts; although routine and preventative maintenance are recommended and performed onsite with nominal operational downtime.

Common Blower/Exhauster Capacities Used In Landfill Gas Applications

Medium Flow Performance Chart
  • Inlet Flow: 100 to 10,000 CFM (170 to 16,900 m3/h)
  • Total Differential Pressure: 0.5 to 26 psig (0.03 to 1.8 bar g) 
  • Vacuum Range: 1 to 19 inHg (35 to 640 mbar)
  • Materials Of Construction: Cast iron with carbon steel shaft and aluminum impellers 
 

Environmental Landfill Gas Process And Applications 

The landfill gas process begins with decomposition and common applications include landfill gas extraction to flare, and landfill gas to energy. 

 

Decomposition 

Organic matter is decomposed when organic waste in landfills is covered and compressed by heavy equipment. There are four stages of decomposition:
  1. Aerobic bacteria break down the material while consuming oxygen. The primary byproduct is CO2.
  2. Once the oxygen is used up, an anaerobic process converts matter to acids produced in stage two and form acetate. At this point, methane-producing bacteria begin to establish themselves.
  3. This stage starts when the anaerobic bacteria consume the organic acids produced in stage two and form acetate. At this point, methane-producing bacteria begin to establish themselves.
  4. When both the composition and production rates of landfill gas are relatively constant you are in stage four. At this point, the gas usually consists of 45-60% methane by volume, 40-60% CO2 and 2-9% other gases, such as sulfides. Gas is produced at a stable rate in this stage for about 20 years. 

Landfill Gas Extraction To Flare

The methane gas created by the anaerobic process in a waste landfill must be vented to prevent explosions. This gas is usually flared off to be safely disposed of.

Areas are carefully prepared for new landfills with a base of clay, sand, and membrane designed to prevent leachate from reaching the groundwater. A layer of garbage is added, compacted mechanically and topped with a layer of soil. 


Landfill Gas To Flare Process Overview

Another layer of garbage and more soil is added, and so on until the landfill section is deemed full. The area is then topped with special low permeability soil, an HDPE membrane, more soil and vegetation cover. Holes are bored and piping collects the potentially hazardous methane gas. The quantity of vent pipes is determined based on many factors including the rate of decomposition, climate, thickness, the number of layers, and more. A multistage centrifugal blower/exhauster forces the gas mixture, mostly methane gas and carbon dioxide, to leave the landfill and send it to the landfill gas vent flare. 

This process can use one or multiple multistage centrifugal blowers/exhausters. A single blower/exhauster could draw from twenty or fifty vent pipes;  however, the vent pipes must be engineered to draw an even vacuum. Multiple blowers/exhausters can address this potential issue. 

Landfill Gas To Energy Process Overview

Landfill Gas To Energy

The methane gas created by the anaerobic process in a waste landfill must be vented to prevent explosions. This gas can be valuable and is often saved. 

If economically feasible, the gas is cleaned to pipeline quality as “renewable natural gas” or “biomethane”. The gas can be added to the gas pipeline grid and mixed with natural gas. Additionally, the biomethane gas can be used to heat water or air or heat part of an industrial process. If compressed, biomethane can power internal combustion or fuel cell vehicles. 


After the landfill gas blower/exhauster passes the methane and carbon dioxide mixture, it is diverted to a second blower/exhauster, which goes to hydrogen sulfide removal, a dyer and scrubber tower or to clean the gas. At this time, food-grade COcan be separated from the methane. Siloxane trace contaminants are also removed and hinders combustion. An aftercooler may be required to cool the volatile methane gas after compression. The cleaned methane gas moves to a storage vessel where it can be used in the process or added to the natural gas grid. 

Downloads For Landfill Gas Extraction

Multistage Centrifugal Blowers & Systems Landfill Gas Packages

Landfill Gas Packages

Standard Packages Selection Guide

Standard Packages Selection Guide

MAX Seal Upgrade

MAX Seal Upgrade

Gas Boosting System For North American WWT Facility

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Trusted Experts 

Equipment is tested before reaching the customer or end-user. This ensures top quality and avoids operational downtime. Therefore, upholding Hoffman & Lamson’s strong reputation as the global leader of engineered solutions and producing premier quality products efficiently and economically. There are over 100,000 HOFFMAN & LAMSON multistage centrifugal blowers/exhausters in operation worldwide.

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