Two Stage Catalytic Water Boiler
Development of a Compact Low Emission Wall-Mounted Catalytic Water Heating Boiler of 5-25 kW Power Based on the Two Stage Oxidation of Natural Gas
Tech Area / Field
- NNE-HCS/Heating and Cooling Systems/Non-Nuclear Energy
8 Project completed
Senior Project Manager
Mitina L M
Boreskov Institute of Catalysis, Russia, Novosibirsk reg., Akademgorodok
- Plant "Izmeritel", Russia, Smolensk reg., Smolensk\nGP Kometa, Russia, Novosibirsk reg., Novosibirsk\nScientific Research Institute of Electronic Devices, Russia, Novosibirsk reg., Novosibirsk
- Mitsubishi Heavy Industries, Ltd., Tokyo / Advanced Technology Research Center, Japan, Yokohama\nCranfield University / School of Engineering, UK, Beds, Cranfield
Project summaryProject Purpose and State of Art.
The conventional technologies for producing heat in domestic heating systems are based on the flame combustion of hydrocarbon fuels. Because fuel combustion is performed at rather high temperatures (ca. 1,200-1,500 °C), the concentration of CO and NOx in waste gases exceeds the level permitted for domestic areas. Using catalysts it is possible to decrease combustion temperature and, thus, to reduce flue gas emission of NOx and CO. This offers possibilities for development of new environmentally sound methods for heat production. The existing methods being designed for catalyst application in water heating systems are based on the combination of homogeneous combustion and heterogeneous-catalytic oxidation of natural gas. Such methods are used in Vaillant water boilers (Germany) adopted catalyst unit TEC KAT VC 107 E and in the Viessmann water boiler “Eurola” (Germany) with a matrix catalytic burner. These boilers provide CO Ј 17 mg/kWh and NOx Ј 9 mg/kWh in waste gases. The maximal range of power modulation is 1:2.25 and the boiler mass calculated per 1 kW of the generated power is about 3-5 kg/kW. According to our results of the direct catalytic oxidation for natural gas, emissions of CO and NOx are Ј 2 mg/kWh and Ј 1 mg/kWh, respectively. Therefore, the application of catalysts is a priority direction in future heating systems. To provide high profitability of the boiler, it is necessary to decrease significantly mass and dimensions of the units, to extend the range of power modulation, to improve the dynamic characteristics, and to reduce the cost. These can be accomplished through development and application of new principles of heat generation and water boiler control. The Project is meant to solve the above problems. The main goal of the Project is to design a prototype of the domestic boiler of 5-25 kW power based on the principle of catalytic oxidation of synthesis gas obtained in this device by air conversion of natural gas or by oxidation of gasification and pyrolysis products of renewable feedstock. The boiler will have the below parameters: mass per generated power Ј 2 kg/kWh, power modulation 1:5, and a system for digital control of operation regimes. It will provide CO Ј 2 mg/kWh, NOx Ј 1 mg/kWh, and CH4 Ј 40 ppm.
Technical approach and methodology.
H2 and CO, generated by air reforming of natural gas, are easily oxidized in the presence of heterogeneous catalysts. So, H2 is completely oxidized on the Pt catalysts even at room temperature and CO is oxidized at 200-300 °C. This opens a way to design a new technical approach for development of effective water boiling systems. The approach consists in the preliminary partial oxidation of methane to synthesis gas (the first process step). The partial oxidation is carried out on the Ni/Al2O3 catalyst at 800 to 900 °C, and the oxygen concentration is 30-35% from the stoichiometry required for complete methane oxidation. It is important to provide complete conversion of natural gas at the first step. For technical implementation of the first step, one should design heat-conducting metal porous catalysts and a generator of synthesis gas. At the second step, the obtained synthesis gas is oxidized to water and CO2 on the catalytic heat-exchanging surfaces. The reaction between the oxygen air added to the reaction zone and synthesis gas yields heat on the catalyst surface in a temperature region of 200-300 °C. The products of gasification or pyrolysis of the renewable feedstock can be used instead of synthesis gas at the second step. For this step, we intend to use the catalytic heat exchangers designed at the Boreskov Institute of Catalysis. The exchangers are designed as a number of metal tubes for water to be heated. Synthesis gas, fed to the intertubular area, is oxidized on the metal-porous catalyst layer, which is sintered with the outer surface of the tubes. Because of high heat conductivity of the catalyst sintered with the metal wall, heat is effectively transferred from the reaction zone on the catalyst surface to heated water. By varying the number of tubes and improving their outer surface at the expense of ribbing, one can obtain the conditions that will provide CO Ј 2 mg/kWh, NOx Ј 1 mg/kWh, and CH4 Ј 40 ppm. The catalytic heat-exchanging tubes with the supported catalyst will permit us to design a compact unit for oxidation of synthesis gas and water heating. To increase efficiency of the energy conversion to 106-108%, the boiler can be supplied with a condensation step mounted into the unit of the catalytic heat exchanger.
Expected Results and their Application.
Technical results of the Project are based on the design, manufacturing, and testing of a water boiler prototype with the following parameters: mass calculated per kW power is lower than 2 kg/kW, power modulation 1:5, digital control of the boiler operation, and efficiency of the energy conversion not lower than 96-98% (106-108% if the condensation step is used).
Environmental results are associated with a design of the boiler providing the emission of CO Ј 2 mg/kWh, NOx Ј 1 mg/kWh, and CH4 Ј 40 ppm.
Profitability of the Project is associated with an application of low-content platinum or no-platinum catalysts and a considerable saving in material upon manufacturing the water boiler, because the proposed mass of the boiler will be 2 kg/kW compared to 5-6 kg/kW of the conventional units.
Commercial benefit of the Project is associated with a design of a new-type low-cost and compact boiler whose ecological and technical parameters will be superior to the conventional boilers.
Commercial potentials of the boiler can be significantly broaden because for heat generation will use both natural gas and products of gasification of renewable non-oil feedstock.
The marketing has shown that such boilers are in large demand in the gas-producing and gas-consuming regions of our country.
Outline scope of activities:
1. Development of heat-conducting metal porous catalysts for air reforming of natural gas. Experimental study and long-term testing of the prepared catalysts.
2. Development of heat-conducting metal porous catalysts for oxidation of synthesis gas and of technologies for the catalyst sintering with the metal surface. Experimental investigations and long-term testing of the prepared catalysts.
3. Redevelopment of the benches for testing of the catalyst and boiler units.
4. Design and manufacturing of a unit for generation of synthesis gas. Investigation of the operation regimes.
5. Design and manufacturing of a catalytic heat exchanger. Investigation of the operation regimes.
6. Design of systems for start-up, digital and safety control of the boiler.
7. Development of versions for feeding and mixing of gas and air.
8. Design and manufacturing of the boiler prototype operating on the natural gas.
9. Testing of the water boiler prototype.
10. Design of versions of the boiler operating on the products of pyrolysis and gasification of the renewable feedstock.
11. Presentation of the water boiler. Preparation of the Final Report. The BIC-ISTC Kick-off Meeting “Prospects for the catalyst application in domestic heat production. Discussion of the Project results”.
Importance of the Project in meeting the ISTC goals.
In parallel with a solution of the research and technical problems, the Project will help in solving the below ISTC problems: provision of weapons engineers, particularly those possessing knowledge and skills related to production of mass destruction weapons; provision of reorientation of their experience to peaceful activities; support of basic and applied research and technology development for peaceful purposes, especially in the field of environmental protection, energy production; reinforcing of transition to the market-based economies responsive to civil needs.
Thus, the Project performance will permit us to design a new-type boiler whose operation characteristics are much better than that of the known analogues. Participation of the researchers and specialists of the armaments industry will be of great help in designing the competitive product. The cooperation between the Project parties established in the course of the Project performance will result in strong bindings between our organizations and provide actual conversion of the armaments industry enterprises for manufacturing the high tech products, which corresponds to the goals of ISTC. Total number of the person-months of the effort of weapon engineers included in the Project are 254 man months, which is 60% of the total time of work under the Project.
Competence of the Team in the Project Goals Achievement.
The Russian researchers have gained much experience in designing of heat-conducting metal porous catalysts and technologies for catalyst deposition on the metal surface as well as in application of the catalysts in heat-and-power generating systems. Ten articles and three patents considered the above problems. In 1997-1999 we had a cooperation with NWO (the Netherlands) under Project No 047-011-000-01. Since October 2000 we are working under Grant COPERNICUS ICA2-CT-2000-10004. In addition, we have a fruitful cooperation with ISTC. In 1998-2000, the ISTC Project No 763 “Development of Pollution-Free Autonomous Heating System for Domestic Needs with 25-50 kW Power Based on the Principle of Catalytic Combustion of Gas Hydrocarbon Fuels” has been successfully accomplished.
Role of the Foreign Collaborators.
Along with the Russian researchers, the institutions of the European community participate in the Project. They will perform joint testings of the catalyst samples and the boiler prototype manufactured and transferred to them in accordance with the Project Program; analyze the obtained results; provide the necessary consulting and information; analyze the potentials of the design commercialization; provide marketing of the Project results for environmentally safe conversion of energy of the non-oil feedstock.