From landfill to the tomato plant – purified biogas powers ... - Eco-Tec

Te Ca Fe c at s h e u n in r o elPo o g y i n Sp to t l i g h tFrom landfill to the tomatoplant – purified biogas powersgreenhouse operationThe Board of Waste Management forthe Mauricie region of Quebec, Canada,known as RGMRM, needed a gasscrubber to remove the highly corrosivelevels of hydrogen sulfide (H 2S) at itsmunicipal landfill.The aim was to purify the landfill gasfor a greenhouse on site, which also isRGMRM’s customer. The gas was to beconverted into a usable source of heatfor the greenhouse, especially during thewinter months, and into a source of CO 2to enrich the hydroponic tomatoes grownthere. In turn, the renewable source ofcarbon dioxide, present in the biogas,would eliminate the costs associated withhaving to purchase and maintain CO 2forthe operation.In 2009, RGMRM found a solutionthrough an Eco-Tec Inc. system knownas BgPur, which uses a patented, highefficiency gas-liquid contacting process,allowing H 2S to be absorbed and the gaspurified for reuse in power generation,cogeneration and heating applications.Today, the BgPur system continues to successfully removemore than 99 percent of hydrogen sulfide from the gasat RGMRM’s landfill, for reuse in its internal processes.Located among the Laurentian Mountains, RGMRM is theboard of management of waste for the Mauricie region ofQuebec, Canada, which has a population of approximately300,000 people. The public body was formed through anamalgamation ofseveral municipalitiesentrusting it tomanage the region’swaste. RGMRM’smission includesrespect for theenvironment, soundmanagementprinciples and a focuson innovation.Figure 1. The washed solid crystalline sulfurproduced by BgPur is pure sulfur, which canbe used as an agricultural supplement andresold as a valuable commodity by the client.It was RGMRM’sfirst partnership withfellow Canadianmanufacturer, Eco-Contributed by Eco-TecFigure 2. An RGMRM installationTec Inc., located in Pickering, Ontario. Eco-Tec’s in-houseResearch and Development facility has been building industrialpurification solutions since 1970, and has installed more than1,500 systems in more than 55 countries.RequirementsRGMRM needed a landfill gas scrubber that would removeH 2S and allow the gas to be used as a source of heat andCO 2for a 540,000 sq. ft. greenhouse on site. The volume ofsaturated landfill gas extracted from the wells is 3,085 Nm 3 /hour, at a maximum temperature of 40°C and with an H 2Sconcentration of 50 ppmv.The greenhouse specified that the gas needs to beprovided to them with an H 2S concentration of less than 1ppmv and dried to a maximum dew point temperature of 3°C.SolutionThe BgPur system was designed for the client to handlethe complete flow through two single contactors to remove theH 2S down to the required level. The purified gas is compressed(to 1 barg) and then chilled to meet the greenhouse’srequirements.10 Biomass Products & TechnologyJune 2011

Te c h n o l oCa g y sSp e in o tPo lTe i g i n h x tThis specific BgPur configuration – which features twocontactor tanks rather than one – was installed for RGMRMbecause of the large volume of gas coming from the landfill(3,085 Nm 3 /hour). Each contactor can handle about 1,500Nm 3 /hour.The overall system eliminated the need for 9 million m 3 /year of natural gas and, as a result, reduced Greenhouse Gas(GHG) emissions by approximately 135,000 tons of CO 2forthe client. The H 2S in the treated gas is less than 1ppmv, andgenerally below the detection limit of 0.2 ppmv more than theentire inlet concentration range.SystemThe H 2S scrubber system is designed with a patentedmass transfer technology that allows the H 2S to be absorbedinto solution where the chemistry converts it into elementalsulfur. The system takes advantage of the oxygen present inlandfill gas, which regenerates the absorption chemistry atthe same time. The elemental sulfur floats to the surface as afroth/foam where it overflows into a slurry thickening section.The slurry is pumped to a filter press which removes the solidsulfur and returns the filtrate back to the contactor for a fullyclosed-loop process.The filter press provides a 60-65 w/w sulfur cake, whichis greater than 99 percent sulfur. The washed solid crystallinesulfur produced by BgPur is pure sulfur, which can be usedas an agricultural supplement that can be resold as a valuablecommodity by the client.For RGMRM, the system also delivers a simple designand operation with no packed columns, allowing continuousreliable operation without any column to plug, foul or foam;and no labor formedia cleaningor replacement.The systemarrived factoryconstructedwith a compactdesign, whichprovides a smallfootprint, shortdelivery and lowinstalled costs.The automatedcontrol systemdetects responseto changes ingas flow-rate orH 2S compositionand suppliesautomaticreagent addition.As well,Figure 3. Single contactor schematicthere’s no wasteresulting from theoperation, onlyenvironmentally acceptable solid sulfur cake, which means noadditional waste treatment equipment or operating costs areneeded; and no disposal of potentially hazardous media. CFor more information, visit www.eco-tec.comJune 2011www.GoBiomass.com11