Destruction of VOC in a Dall Energy Biomass Gasifier at Warwick Mills

Transcription

1 Destruction of VOC in a Dall Energy Biomass Gasifier at Warwick Mills Paper # 17 Presented at the 34 th International Conference on Thermal Treatment Technologies & Hazardous Waste Combustors October 20-22, 2015 Houston, TX Authors: Jens Dall Bentzen, Managing director Dall Energy, Venlighedsvej 2, 2970 Hoersholm, Denmark. jdb@dallenergy.com homepage: Charlie Howland, Managing director Warwick Mills, at 301 Turnpike Road, PO Box 409, New Ipswich, NH. ABSTRACT Warwick Mills, a factory in New Hampshire, which produces complex fiber composites for the most challenging safety applications, has installed and commissioned a Dall Energy biomass gasification plant. The biomass plant has two main purposes: - Destroy VOC from coaters in factory - Produce steam to factory On September 30 and October 1, 2014, the emissions of the biomass plant were measured. Test September 30, 2014: The VOC content in the combustion air was at maximum: 8,000-10,000 ppmv. The VOC content in the stack was below 1 ppmv. The VOC destruction efficiency was %. Also the particulate content and the NOx in the flue gas were measured:the particulate content was below 10 mg/nm3. The NOx was below 60 mg/nm3 (30 ppmv). Test October 1, 2014 The VOC content in the combustion air at medium: approximately 3,000 ppmv. The VOC content in the stack was below 3 ppmv. The VOC destruction efficiency was 99.8 %. 1

2 Also the NOx in the flue gas was measured. The NOx was below 80 mg/nm3 (40 ppmv). The VOC content in ambient air, outside the stack, was about 5-10 ppmv, thus higher than inside the stack. INTRODUCTION A new type of biomass and waste combustion system has been developed and implemented in 3 full scale projects: 2 in Denmark and 1 in USA. The purpose was to develop a combustion system that: - Can use multiple types of fuels - Has low emissions - Can modulate The purpose of the technology is to produce thermal energy for communities and industries using low grade solid fuels (MSW, wood wastes). Further,the technology can be used for incineration of industrial wastes and destruction of VOC. This paper describe the history of the development of the technology, with focus on the plant at Warwick Mills in New Hampshire, USA. The idea behind the development was to take advantage of the benefits within updraft gasification technology in a combustion system. Updraft gasification is an old, well known technology which has been used to produce town gas for centuries. However, updraft gasification has some disadvantages: When the gas is cooled, a large amount of tars condense, thus plugging up pipes and polluting waste water from the gas condensation system. The updraft gasification technology With updraft gasification, the gasification medium (air/steam) and the produced gas flow through the gasification reactor in the opposite direction to the fuel bed. The reactor is fed from above, and the gasification media enters the reactor in the bottom. With this method of gasification, clearly defined reaction zones arise in the bulk filling. The sensitive heat of the produced raw gas is used to dry the fuel and to initiate pyrolysis. 2

3 Figure 1. Schematic diagram of an updraft gasifier [2] As it can be seen in the schematic diagram in Figure 1, the products of decomposition released in the pyrolysis zone and the steam released as a result of fuel drying are discharged directly out of the reactor with the producer gas. The tars that are produced in the pyrolysis zone are not conducted through any hot zone and can therefore not be suitably split up or oxidized. The tar content in the raw gas can thus reach values over 100 g/nm3. The Bioneer updraft gasification system During the 1980 s the Finnish company Bioneer made 9 commercial district heating systems, where an updraft gasifier produced gas for use in a gas boiler. The fuels were wood chips and peat. The plants operated fine, but tars did foul the gas pipe leading from the gasifier into the boiler. In some plants the gas line was cleaned once every 2-6 weeks (depending on the fuel properties and output of the gasifier). [1] 3

4 Figure 2. Bioneer-gasifier in the district heating plant of Kauhajoki, Finland [1] The Babcock&Wilcox Vølund gasification system During the 1990 s the Danish company Babcock&Wilcox Vølund (BWV) develop a gasification system for combined heat and power, based on updraft gasification technology. In the BWV system, the gas is cooled and cleaned and thereafter used in an internal combustion engine for production of heat and power. A demonstration plant was built in the Danish town Harboøre, and after a few years the plant was placed in commercial operation. In the BWV concept, the gas is cooled in a wet cyclone and wet electrostatic precipitator after the gasifier. There are no problems with fouling of gas pipes, but the large amounts of tar are dissolved in the scrubber water. The main technical and financial issue about this technology is the rather complex gas cleaning and waste water cleaning systems which handle the considerable amounts of tar. 4

5 Figure 3. BWV gasifier (left) and flow diagram at heat and power plant Harboøre (right) [3] The Dall Energy gasification and gas combustion concept Previous attempts to make commercial concepts by use of the updraft gasification technology had problems with the high amounts of tars that are produced in the updraft gasifier. The idea behind the Dall Energy concept is to burn the tar producing gases produced in the gasifier above the gasification section in the same reactor as where the gasification takes place. Hereby, the advantages of the updraft technology will be maintained, while the disadvantage of tar in the gas will be solved. Figure 4. Principle diagram of Dall Energy multifuel furnace. [5] 5

6 THE DEVELOPMENT AND IMPLEMENTATION OF THE DALL TECHNOLOGY 2 MW Pilot plant In 2009 a 2 MW pilot plant was designed and built in Denmark. The aim of the project was to verify the objectives of technology: low emissions, stable operation, possibility to run the plant at low load. The plan was to find a commercial host for the pilot plant when the objectives had been reached. Before the plant was built, an extensive study of the gas combustion chamber was made using CFD modeling to predict low emissions both at low load and full load. Figure 5. 2 MW Pilot plant (left) and CFD model of CO emission at 20% load [4] The results of the pilot plant were very successful: - Dust emission directly out of furnace: 20 mg/nm3 - CO emission at full load: below detection level - CO emission at 20% load: below detection level The plant operator at the local district heating plant in the town Bogense followed the tests of the pilot plant with great interest which led to negotiations for a full scale demonstrations plant. 8 MW demonstration plant in Denmark The demonstration plant needed to be able to produce 8 MW hot water for district heating. The 2 MW pilot plant could therefore not be used. A new design of an 8 MW furnace was made. 6

7 A contract between Bogense district heating company and the contractor, Weiss A/S, was made in May Dall Energy had the task to design the furnace and administrate a grant from the EUDP program. The Bogense plant was placed in un-manned, commercial operation in [6] Various types of fuels are used in the plant including garden wastes and wood wastes. Figure 6. 8 MW Demonstration plant in Bogense [4] Emission tests was made in marts 2012 Table 1. Measurements in flue gas directly out of furnace Parameter Unit Average Average Load % Date dd-mm-yy Measuring period hh:mm 11:12-14:22 16:44-20:00 Temperature C O 2 Vol % (dry) H 2O Vol % CO mg/m³(ref) < 2 < 2 NO X mg/m³(s,d) NO X mg/m³(ref) Particles * mg/m³(s,d) Particles * mg/m³(ref) Condensable in rinse and condensate mg/m³(s,d) Condensable in rinse and condensate mg/m³(ref) (s,d) indicates dry gas at standard conditions (0 C, 101,3 kpa) (ref) indicates dry gas at standard conditions (0 C, 101,3 kpa) at 10 % O2 * means "not included in accreditation no. 51" 7

8 2 MW plant for VOC destruction at Warwick Mills Warwick Mills, New Hamphire, USA is a leader in the engineering of technical textiles for protective applications. Warwick Mills develops and manufactures complex fiber composites for the most challenging safety applications. The advanced manufacturing of safety equipment includes coating of wowen materials with organic solvents. The ventilation air from the coaters contains Volatile Organic Compounds (VOC) which needs to be combusted in a thermal oxidizer before the ventilation air can be sent to the stack. The fuel bill for the oil based thermal oxidizer was constantly increasing, and the plant manager, Charlie Howland, started in 2008 to search for biomass technology which could be used instead of oil. The biomass plant needed to fulfill the strict emission regulations of New Hampshire. Mr. Howland could not find a biomass technology locally that could fulfill the emission regulations. In 2010 Mr. Howland made some search via Google and found hereby the web site of Dall Energy, who had published the results of the pilot plant. Mr. Howland decided to visit Dall Energy in January 2011 to see the pilot plant and the Bogense plant which at that time was under construction. Dall Energy and Warwick Mills made thereafter an agreement for the design and build of a biomass plant for Warwick Mills which would have several purposes: - Destruction of VOC. - Production of Steam. - Control strategy of the plant so destruction of VOC was independent of steam production - Low load for stand by during weekend - Low particle load in chimney. During the building permits were obtained and construction of the plant could start. The production of the furnace was now ready to start. The size of the plant for Warwick Mills was the same as the pilot plant built in 2010; and as the pilot plant was no longer in use, Dall Energy-Warwick agreed that Warwick Mills could buy the pilot plant. And so the pilot plant was dismantled and shipped from Denmark to USA. The first start up of the plant was done in April During the first week of operation, various points were located to be optimized and adjusted. The plant was shut down and the list of adjustments was made. The plant was started up again in June 2014 and has been in operation since then. 8

9 Figure 7 Principle diagram of Dall Energy Furnace at Warwick Mills. Emission test The plant is used for destruction of organic solvents in the ventilation air (VOC). It was written into the permit that an emission test was required at least 6 month after starting the plant. The emission test must verify that the VOC destruction efficiency was at least 98% and particulates in the flue gas had to be below 40 mg/nm3. The stack test was scheduled for two days: September 30 and October Test September 30, 2014: The VOC content in the combustion air was at maximum: ppmv. The VOC content in the stack was below 1 ppmv. The VOC destruction efficiency was 99.98%. Also the particulate content and the NOx in the flue gas was measured. The particle content was below 10 mg/nm3. The NOx was below 60 mg/nm3. (30 ppmv) Test October 1, 2014 The VOC content in the combustion air was approximately 3000 ppmv. The VOC content in the stack was below 3 ppmv. The VOC destruction efficiency was 99.8%. 9

10 Also the NOx in the flue gas was measured. The NOx was below 80 mg/nm3. (40 ppmv). Less emission in stack than in ambient air Ambient air contained VOC from various sources such as degradation of wood in forest, traffic, chimneys, etc. The VOC content in ambient air, outside the stack, was about 5-10 ppmv, thus higher than inside the stack. Figure 8 Emission test. Warwick Mills, Figure 9 Filters after emission test. Warwick Mills,

11 Operating strategies of the plant The biomass plant at Warwick Mills has two main purposes: - Destroy VOC from factory - Produce steam to the factory The amount of VOC-loaded air and the need for steam are not related so a new strategy of operating the plant was developed: Demand High Energy demand High VOC destruction demand Operating strategies Increase of primary air until energy demand fulfilled. Increase of (VOC loaded) tertiary air Idle load during weekends The factory is normally shut down during weekends. An operating strategy for low chip consumption was developed so the plant can keep warm during weekends and only use a very low amount of wood chips. On Monday morning the plant can go from weekend mode to full load in few hours.. Figure 10 Gasification plant operator, Marcel Alex, (left) and Managing director Charlie Howland (right) at the Gasifier, June A film about the plant can be viewed here: 11

12 mg/nm3 9 MW plant in Denmark During , a new 9 MW plant was planned and built in Denmark. The client is Sønderborg district heating company. The purpose of this plant is to supply cheap and renewable heat to the Sønderborg district. The plant was started up in January Emission tests were carried out in March The low emissions of the pilot plant, the Bogense plant and the Warwick plant were verified Emissions from Dall Energy plants Danish Limits Bogense Sønderborg Warwick NOx CO Dust Figure 11 Emissions of NOx, CO and Dust from three Dall Energy plants. 12

13 Figure 12 9 MW Dall Energy plant in Sønderborg. RESULTS AND DISCUSSION A new, multi-fuel, low emission combustion system has been developed. The technology has been verified in a pilot plant and 3 commercial plants: 2 district heating plants in Denmark for production of hot water and 1 industrial plant for VOC destruction and production of steam in USA. During the projects, the following features have been verified: %-99.98% VOC destruction mg/nm3 dust directly out of Furnace - Fuel flexibility: - Garden waste, wood waste, wood chips % moisture content - 1-5% ash content % operating load. - Stable operation. ACKNOWLEDGEMENTS EUDP The Danish Energy Agency support program who have contributed with financial support The Growth fund who have contributed with financial support The Danish Environmental Agency who have contributed with financial support The Ministry for Research and Innovation who have contributed with financial support 13

14 REFERENCES 1. OPET Finland, Review of Finnish gasification technologies, OPET Report 4, ESPOO Gasification Guide, Deliverable 8: Biomass gasification State of the art description. December Biomass gasification plants. From web page of Vølund: 4. Verification and further development of multifuel furnace for biomasse with low NOx and dust emissions. Danish Energy Agency. 5. Dall Energy homepage 6. Research in Bioenergy, September KEYWORDS Biomass, multifuel, gasification, VOC, Emissions, NOx, CO, Dust. Environmental 14