Title of Invention

A PROCESS AND APPARATUS FOR CLEANING TAR AND DUST LADEN GAS TO HIGHEST LEVEL OF PURITY USING Cn TECHNOLOGY

Abstract

The present invention provides a process for cleaning tar and dust laden gas to highest level of purity using C<Sup>n</Sup> technology process comprising of: a. passing the hot tar and dust laden gas at 400-600&#730;C is through a high efficiency cyclone to reduce particulate and tar level, b. the said hot gas at temperature of 250-500&#730;C is then passed through clean water scrubber’s to achieve both cooling and cleaning, c. the said ambient temperature gas is further passed through a chilled water scrubber where chilled water at less than 10&#730;C is used to produce clean and dry gas. The present invention also provides an apparatus for cleaning tar and dust laden gas to highest level purity using C<Sup>n</Sup> technology.

Full Text

The present invention relates to a process and apparatus for cleaning tar and dust laden gas to highest level of purity using CN technology". Background Biomass derived producer gas has been found to be a cost effective fuel for power generation application via internal combustion route. This is possible by gasifying biomass in a reactor under controlled conditions and subsequendy cooling and cleaning the gas. Producer gas generated by gasification of biomass is hot and contaminated with higher molecular weight organic components called tar and carbon dust/ash. The gas has to be appropriately conditioned for use in internal combustion engines - reciprocating engines/gas turbine or in high quality burner system. The expected level of gas cleaning for such application is of the order of less than 1 - 2 ppm (parts per million). The invention that is described in this document is a gas conditioning or cleaning unit, which is herewith referred as CN technology for cleaning tar and dust laden gases to such levels that resultant gas has contaminant level at ppb level. Cleaning gas off fine dusty and tarry material is done by complex means, which include bag filters and electrostatic precipitators. Using electrostatic precipitators is hazardous, as combustible gas would be flowing through the system. Two patents, US patent 4203726 awarded to Berz on May 20, 1980 and US patent 4406672 awarded to Berz on 27 September 1983 describe cleaning of dust laden gases (no mention of tar is made) by passing through a filter bed of granular material and applying high electric potential charge across them. The objective of invention described herewith is to obviate the above drawbacks and yet provide much more effective cleaning of gas containing both tar and dust The current invention (Cn technology) differs from the prior art in the following aspects: Dust separation is achieved through passive devices, unlike the existing devices which requires high voltage to be applied, A new principle of cleaning, namely condensation of water around the dust particle, is utilized for achieving ultra-high purity. Though a filter is used in the current case, its use is only as a security device, rather than as a primary cleaning device An innovative scrubber design is used, which in addition to achieving high purity of gas, also assists in pumping the gas, thus recovering part of the energy used by the water of pumps. Furthermore, the current invention is more passive in terms of operation and is scalable so as to handle small to large quantity of tar and dust laden gases. Accordingly, the present invention provides a process for cleaning tar and dust laden gas off to highest level of purity using Cn technology process comprising of: a. passing the hot tar and dust laden gas at 400-600 °C through a high efficiency cyclone to reduce particulate and tar level, b. the said hot gas at temperature of 250-500 °C is then passed through clean water sccrubber/s to achieve both cooling and cleaning, c. the said ambient temperature gas is further passed through a chilled water scrubber where chilled water at less than 10 °C is used to produce clean and dry gas. The instant invention also provides an apparatus to clean tar and dust laden gases to highest level of purity by the process as made in claim 1 and 2 for use in high quality combustor/s for thermal application using Cn technology elements comprising of: a. high efficiency cyclone to reduce particulate and the tar levels of the hot tar and dust laden gas, b. the said high efficiency cyclone connected to clean water scrubher/s for cooling and cleaning said hot gas, c. the said clean water scrubber connected to chilled water scrubber to produce clean dry gas. Brief Description of the Drawings: The invention will now be described with reference to the accompanying drawings: Figure 1 shows the flow diagram of Cn technology for cleaning tar and dusty laden gasses to highest level of purity. Figure 2 shows a schematic of Cn technology to process tar and dust laden producer gas so as to generate 1 IcWe power using internal combustion engine. Figure 3 shows a schematic of Cn technology to process tar and dust laden producer gas so as to generate 120 kWe power using internal combustion engine. Figure 4 shows a schematic of Cn technology to process tar and dust laden producer gas so as to generate 750 kWe power using internal combustion engine. Figure 5 shows a schematic of Cn technology to process tar and dust laden producer gas so as to generate 4 MW of thermal energy. Detailed Description: Figure 1 shows the flow diagram of Cn technology for cleaning tar and particulate laden gases to highest level of purity. Firstly, the particulate and tar laden gas at about 400 -600 °C passes through a high efficiency cyclone, wherein major part of the tar and particulate matter is separated from the hot gas. There is provision for on-line purging of the separated/collected particulate matter from the hot cyclone. The gas at about 250 - 500 °C further flows through clean water scrubber/s, wherein the gas is cleaned and also cooled to ambient temperature. There is moisture trap provided at the exit of the scrubber to trap water droplets, if any. Further, the gas at ambient temperature and with residual tar and particulate matter passes through the chilled water scrubber, where chilled water is used as the scrubbing medium. The gas is dried and also the residual tar and particulate matter is separated from the gas based on the principle of condensate nucleation around a dust/tar particle. Extremely fine particulate and tar matter of sub-micron to 5-10 micron is separated off the producer gas. There is moisture trap provided at the exit of the scrubber to trap water droplets, if any. The dry and clean gas finally passes through a blower to the fabric filter for removal of residual particulate matter left if any, in the gas. The ultra clean and dry gas at about ambient temperature is available for usage in internal combustion engines for power generation or high quality burners for thermal application. The said Cn technology for gas cleaning to generate clean dry gas has been tested in laboratory and field level at 5 m /hr to 3000 m7hr gas flow rate for matching capacities of ] kWe to 1 MWe capcity of power generation using internal combustion engines or high quality burner of 5 kWth to 4 MWth capacity. The examples of such applications is given below Example 1: Figure 2 shows a schematic of Cn technology to process tar and dust laden producer gas so as to generate 1 kWe power using internal combustion engine. The gas throughput through the system is around 5m3/hr. The elements include hot gas cyclone, clean water scrubber, chilled scrubber and fabric filter. The high efficiency cyclone (1) is designed to remove the tar and particulate matter from the hot gas at 400 - 600°C; about 80 % of the particulate is separated off the gas and remaining flow with the gas steam. There is provision for on-line removal of separated particulate matter from the cyclone during the operation of the system. The clean water scrubber (2) is based on ejector design. Apart from cooling and cleaning the gas from 250 - 500 °C to ambient temperature, the water flow assists/drives the gas flow through the system. This is possible by using specially designed water spray nozzles wherein impinging jets impart momentum to the gas stream through ejector action and thereby assist the gas flow through the scrubbers. This apart, scrubber (2) eliminates tar and dust off the gas. There is moisture trap provided at the exit of the scrubber to trap water droplets. Furthermore, the ambient temperature gas is drawn through an insulated chilled scrubber (3), wherein chilled water at a temperature less than 10°C is sprayed. The complete chilled scrubber system inclusive of the conveying tube is insulated to prevent heat pickup from the ambient. The chilled scrubber spray nozzle is also of ejector type and therefore provides a pressure gain as the gas flows through it. In this particular scrubber the gas is dried/dehumidified using the principle of condensate nucleation wherein extremely fine particulate matter (submicron to 5 - 10 micron sized particles) is separated from the gas stream. There is moisture trap provided at the exit of the scrubber to trap water droplets, if any. The gas finally passes via the blower through a reusable non-woven fabric filter prior to flowing to the gas engine. The gas quality at the exit of the Cn technology cleaning has been measured using wet methods and is found to be below 1 mg/m3 or 1 ppm level. Example 2: Figure 3 shows a schematic of Cn technology to process dust and tar laden producer gas so as to generate 120 kWe power using internal combustion engine. The gas throughput through the system is around 350m /hr. The Cn technology element package is high efficiency cyclone (1) to process gas, clean water scrubbers based on the ejector principle (2 and 3) with ambient temperature water, chilled water scrubber (4) and fabric filter (5) as explained in Example 1. However, there are two clean water scrubbers instead of one shown in Example 1. In the hot cyclone there is provision made for on-line purging of the separated particulate matter. This facility assists in continuous operation of the system without any stoppage for cleaning of the cyclone. In the clean water scrubber, the water velocity exiting the water spray nozzles is maintained to in excess of 10 m/s so as to provide the desired ejector and gas cleaning effect. There is moisture trap provided at the exit of the scrubber to trap water droplets, if any. Gas drying/de-humidification and further cleaning is achieved in chilled scrubber (4) by spraying chilled water at low temperature (less than 10 °C). There is moisture trap provided at the exit of the scrubber to trap water droplets, if any. The dry and clean gas is taken through a non-wo\en fabric cloth filter (5). Measurements made using wet methods have indicated that the tar and particulate is less than 1 mg/m3'. Direct measurements on the contamination in the engines obtained by weighing the deposits on the components before entn' into the engine cylinders after running the engine for 100, 1000 hours have shown deposition to be of the order of 350 - 400 ppb. Example 3; Figure 4 shows a schematic of Cn technology to process tar and dust laden producer gas so as to generate 750 kWe using internal combustion engine. The gas throughput through the system is around 2000 m /hr of producer gas. The Cn technology elements in this package are high efficiency cyclone (1) to process gas as explained in Examples 1 and 2, clean water scrubbers based on the ejector principle (2 and 3) with ambient temperature water, chilled water scrubber (4) and duplex fabric filters (6). The design and functioning of all the elements are as explained in Example 2. There are three additional features in this particular configuration. The first is related to the provision of waste heat recovery from the outer walls of the hot cyclone to be used either for district heating application, biomass drying activity, or for any other effective waste heat utilization. The second is related to the use of vapor absorption chilling system (5) for generating cold water ( Example 4: Figure 5 shows a schematic of Cn technology to process tar and dust laden producer gas so as to generate 4 MW of thermal energy. The gas throughput through the system is around 3000 m3/hr of producer gas. The Cn technology elements in this package are high efficiency cyclone (1) with a waste heat recovery as explained in Example 3, clean water scrubbers based on the ejector principle (2 and 3) with ambient temperature water, chilled water scrubber (4). The design and functioning of all the elements is as explained in Examples 1, 2 and 3. Since there is no waste heat available other than from the hot cyclone, the chiller is operated on vapor compression cycle (5). The dry and clean gas is made available at the exit of the blower for thermal use via standard industrial class bumer/s. Measurements made using wet methods have indicated that the tar and particulate is less than 1 mg/m3, Direct in-plant measurements on contamination in the blower have shown deposition of 350 ppb at the end of 2500 hours of operation. The particle size distribution of the deposited material is around 1 micron. The use of Cn technology has resulted in excess of 1250 hours of uninterrupted operation of the system without observable deterioration of the blower operation (it is the blower that the deposits would accrue. We claim: 1. A process for cleaning tar and dust laden gas off to highest level of purity using Cn technology process comprising of: a. passing the hot tar and dust laden gas at 400-600°C through a high efficiency cyclone to reduce particulate and tar level, b. the said hot gas at temperature of 250-500°C is then passed through clean water scrubber/s to achieve both cooling and cleaning, c. the said ambient temperature gas is further passed through a chilled water scrubber where chilled water at less than 10°C is used to produce clean and dry gas. 2. A process for cleaning tar and dust laden gas off to highest level of purity for usage in high quality combustor/s for thermal application using Cn technology process as described in claim 1. 3. A process for cleaning tar and dust laden gas off to highest level of purity for use in reciprocating engines / gas turbine for power generation application using Cn technology process as described in claim 1 along with either single or duplex clean non-woven type reusable fabric filter connected to the chilled water scrubber 4. An apparatus to clean tar and dust laden gases to highest level of purity by the process as made in claim 1 and 2 for use in high quality combustor/s for thermal application using Cn technology elements comprising of: a. high efficiency cyclone to reduce particulate and the tar levels of the hot tar and dust laden gas, b. the said high efficiency cyclone connected to clean water scrubber/s for cooling and cleaning said hot gas, c, the said clean water scrubber connected to chilled water scrubber to produce clean dry gas. 5. An Apparatus to clean tar and dust laden gases to highest level of purity by the process as made in claim 1 and 3 for use in reciprocating engines / gas turbine for power generation application using Cn technology elements comprising of: a. high efficiency cyclone to reduce particulate and the tar levels of the hot tar and dust laden gas, b. the said high efficiency cyclone connected to clean water scrubber/s for cooling and cleaning said hot gas, c. the said clean water scrubber connected to chilled water scrubber and clean fabric filter to produce clean dry gas. 6. An Apparatus to clean tar and dust laden gases to highest level of purity by the process as made in claim 1, 2, 3, 4 and 5 using Cn technology elements with in¬ built/additional features like a. high efficiency cyclone with a provision for on-line removal of collected particulate matter in the cyclone b. high efficiency cyclone with an outer jacket for waste heat recovery to be utilized either for district heating, biomass drying or any other effective waste heat utilization, c- ejector designed scrubbers - both ambient and chilled water; to assist driving of the dust and tar laden gases through the system, 7. An Apparatus to clean tar and dust laden gases to highest level of purity as made in claim 1, 2, 3, 4 and 5 with either vapor compressor chiller or waste heat based vapor absorption chiller for the generation of chilled water for use in the chilled scrubber. 8. A process for cleaning tar and dust laden gas off to highest level of purity using Cn technology process substantially as herein described with reference to and as illustrated in the accompanying drawings 9. An apparatus to clean tar and dust laden gases to highest level of purity substantially as herein described with reference to and as illustrated in the accompanying drawings

Documents:

0742-mas-2001 abstract-duplicate.pdf

0742-mas-2001 abstract.pdf

0742-mas-2001 claims-duplicate.pdf

0742-mas-2001 claims.pdf

0742-mas-2001 correspondence-others.pdf

0742-mas-2001 correspondence-po.pdf

0742-mas-2001 description (complete)-duplicate.pdf

0742-mas-2001 description (complete).pdf

0742-mas-2001 drawings-duplicate.pdf

0742-mas-2001 drawings.pdf

0742-mas-2001 form-1.pdf

0742-mas-2001 form-13.pdf

0742-mas-2001 form-19.pdf

0742-mas-2001 form-26.pdf

0742-mas-2001 form-3.pdf

0742-mas-2001 form-4.pdf

0742-mas-2001 form-5.pdf

742-mas-2001-abstract.pdf

742-mas-2001-claims filed.pdf

742-mas-2001-claims granted.pdf

742-mas-2001-correspondnece-others.pdf

742-mas-2001-correspondnece-po.pdf

742-mas-2001-description(complete)filed.pdf

742-mas-2001-description(complete)granted.pdf

742-mas-2001-description(provisional).pdf

742-mas-2001-drawings.pdf

742-mas-2001-form 1.pdf