Large-Scale Biogas Purification for Higher Wobbe Factor

• Type: Biogas Purification
• Methods: Psa, Mea, Membrane Separation, Water Scrubbing etc
• CH4: Higher Than 95%
• Transport Package: Standard Export Packing
• Specification: Customized
• Trademark: Mingshuo
• Model NO.: Large-scale Biogas Purification to Reach Wobbe Fac
• Origin: China
• HS Code: 8414802000
• Production Capacity: 100 Sets/Year

Product Description

Biogas Upgrading System for CNG LNG Natural Gas

Biogas is produced in many different environments, including in landfills, sewage sludge and during anaerobic degradation of organic material. Biogas is comprised of methane (CH4 , about 45-75% by volume), carbon dioxide (CO2 , 25-55%), and other compounds including hydrogen sulfide, water, and other trace gas compounds.

Methane is a powerful greenhouse gas if emitted into the atmosphere, but can also represent a valuable renewable energy source, with the potential to reduce GHG emissions when it is collected and substituted for fossil fuels. Biogas can be used directly to generate power, but the large volume of CO2  reduces the heating value of the gas, increasing compression and transportation costs and limiting economic feasibility to uses that occur at the point of production.

Purification allows for a wider variety of uses, either for heat and electricity, or for vehicle fuels. For use as a fuel, purification to remove carbon dioxide (CO2 ) and hydrogen sulfide (H2S) is required, because H2S corrodes vital mechanical components within engine generator sets and vehicle engines if it is not removed, and the large volume of CO2  reduces the heating value of the gas. By below several methods, the biogas can be upgraded to natural gas and used for CNG or LNG.

Comparison of properties of different biogas upgrading technologies


1. Water scrubbing is a very simple process. In a scrubber, CO2 and H2S dissolve into the water, while CH4 does not because of their difference in solubility. Water scrubbg is used to remove CO2 and H2S from biogas since these gases are more soluble in water than methane. The absorption process is purely physical. Usually the biogas is pressurized and fed to the bottom of a packed column while water is fed on the top and so the absorption process is operated counter-currently. Water scrubbing can also be used for selective removal of H2S since H2S is more soluble than carbon dioxide in water. The water which exits the column
with absorbed CO2  and/or H2S can be regeneratand re-circulated back to the absorption column. Regeneration is accomplished by de-pressuring or by stripping with air in a similar column. Stripping with air is not recommended when high levels of H2S are handled since the water quickly becomes contaminated with elementary sulfur which causes operational problems. When cheap water can be used, for example, outlet water from a sewage treatment plant, the most cost efficient method is not to re-circulate the water.

2. In PSA processes, biogas is compressed to a vessel where it is put in contact with an adsorbent that will selectively retain CO2. PSA is a process separating molecules in a gas mixture at elevated pressure. The adsorbing materials generally used are different types of activated carbon, molecular sieves or zeolites,
depending on the gas molecular characteristics and affinity of the adsorbing material. These adsorbing materials can preferably adsorb CO2 and H2S from the biogas, thus methane concentration increases in the gas. The higher the pressure, the more gas is adsorbed. When the pressure is reduced, the gas is freed or desorbed. This process produces a separation since different molecules in a gas mixture tend to be more or less strongly attracted by different solid surfaces. When the adsorbed bed is close to saturation, the regeneration reaction takes place by reducing pressure, thereby freeing the adsorbed gases. It is then ready to cycle again.

The advantages of PSA are: high CH4 concentration (95-99%) and the gas can be directly delivered at high pressure (no need of compression). PSA disadvantages are high investment costs, high operation costs and
extensive process control needed.

3. In a similar manner to water scrubbing, it is possible to use chemicals to absorb CO2. Chemical absorption involves formation of reversible chemical bonds between the solute and the solvent. Regeneration of the solvent, therefore, involves breaking of these bonds and correspondingly, a relatively high energy input. Chemical solvents generally employ either aqueous solutions of amines (i.e. mono-, di- or tri-ethanolamine) or aqueous solution of alkaline salts (i.e. sodium, potassium and calcium hydroxides).

MEA solution can be completely regenerated by boiling for 5 min and is then ready for re-use. The advantages of chemical absorption are complete H 2 S removal, high efficiency and reaction rates compared to water scrubbing, and the ability to operate at low pressure. Because of these advantages, the process is commonly used in industrial applications, including natural gas purification.

4. Membrane separation technology is an excellent technology with good prospects for separating CO2 and CH4. Membrane separations are particularly appealing for biogas upgrading due to their lower energy consumption, good selectivity, easily engineered modules, and therefore lower costs. High CH4 recovery efficiency can be reached (>96%), while pure CO2 can be obtained. The main disadvantage of membrane
separation is that multiple steps are required to reach high purity. 28 This technology for biogas upgrading is based on gas dissolution and diffusion into polymer materials (membranes). When a differential pressure is applied on opposing sides of a polymer film, gas transport across the film (permeation) occurs. The gas rate of permeation is controlled by the solubility coefficient and diffusion coefficient of the gas-membrane system. Polysulfone, polyimide or polydimethylsiloxane are the common membrane materials for biogas upgrading.

Management System Certification: ISO9001:2008, ISO14001:2004, OHSAS18001:2007

Company Introduction: 
Shandong Mingshuo New Energy Technology Co., Ltd. Specializes in biogas project. The company is the production base of medium and large biogas equipments in China, the member of China Biogas Association, the member of China Association of Rural Energy Industry. The company is the recommended member of CCTV Website Enterprise Channel and China Import and Export Commodity Website, the most complete and excellent biogas equipments manufacturers in China. Mingshuo is a professional company integrating the scientific research, technological design, production and debugging service. The company specializes in the production of desulfurizer, desulfurization equipments and biogas equipments. Such as, Mingshuo MTZ biogas dedicated desulfurizer, MT ferric oxide desulfurizer, 889 wet desulfurization catalysts, water treatment agent, MS biogas dedicated desulfurization tanks, thioniers, biogas dedicated gas-water separators, assembled tanks, gas holders, positive-negative pressure protectors, biogas dedicated flame arresters, biogas boilers, deironing magnetic separation equipments, etc. 

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