Evaluation And Analysis Of Shenyang Minglian Boiler House Coal-to-Gas Retrofit Project

Shenyang Minglian Boiler House Coal-to-Gas Retrofit Project is a pilot project for the substitution of clean energy for coal in Shenyang.The original coal-fired boilers were built up in the 1990s with a heat supply area of 272,000 m2.With lower thermal efficiency and higher energy consumption,and out-of-service desulfurizing and dedusting equipment,the boilers had serious pollution to the environment.Moreover,they couldn't satisfy the serving standard of heat supply.Therefore,the heat source coal-to-gas retrofit project accords with the Blue Sky Program put forth by Shenyang Government for the purpose of advocating energy saving and emission reduction.The established Qin-Shen Natural Gas Transmission Trunk Line can guarantee adequate gas supply for the project.Survey results.The status quo of heat supply in Liaoning Province and Shenyang City was investigated.The heat supply area in the whole province is 785,030,000 m2,and the rate of centralized heat supply is 86%.Coal-fired boilers,heat-power cogeneration plants,and heat supplies by renewable energy account for 56%,28%,and 2.2%,respectively as to heating area.The heating area in the downtown region in Shenyang City is 242,000,000 m2,the length of trunk piping lines is 7970 km,and the rate of centralized heat supply is 90%.The serving area by boiler houses accounts for 59.9%of the total heating area of the whole city,that by heat-power cogeneration plants(including peaking heat supply plants)accounts for 27.3%of the total,and that by other energies accounts for 12.8%of the total.The utilization rate of clean energy is 3.6%in Shenyang.Viewing from energy structure,most of the heat-power cogeneration plants and boiler houses take coal as their fuel;only a few of them are fueled by natural gas or electricity.Renewable energies used for heat supply include mainly geothermal energy and solar energy.Retrofit scheme.The retrofit involves process system in the boiler house,civil construction,and control system of heat source.A gas-fired boiler house is newly built at the original place.A gas regulating station is located at the original coal yard.Two WNS10.5-1.0/115/70-Q type of automatic gas-fired hot-water boilers are chosen to take the place of the original three coal-fired boilers.Two heat-exchange units are added in the boiler house(one for high building,and the other for low building)to form the primary and the secondary piping lines.The temperature of feeding water/circulating water is 115?/70? and 70?/50?,respectively.Performance in energy saving.The thermal efficiency of gas-fired boilers is 97%,advantageous as compared with 78.2%of the original coal-fired boilers.The load regulating range is 20%-100%.The annual gas consumption and the annual electricity consumption of the boilers and their auxiliary equipment equal to 6085.5 tce.Compared with the original coal-fired boilers,the rate of energy saving is 27%.The annual water consumption is 18,000 t,representing a water saving rate of 17%.Performance of economics.Based on the actual data of the project and calculation with annual cost method,the initial capital cost of the gas-fired boiler house is 7,700,000 Yuan,averaging 28.48Yuan/m2,the annual operating expenditure is 60.15Yuan/m2,and the annual cost is 1726.4Yuan/m2.The initial capital cost is less and the annual cost is higher,compared with the original boiler house.The reason is that the auxiliary equipment of the gas-fired boiler is less whereas the gas price is higher.By sensitivity analysis,it is known that the annual cost of gas-fired boilers increases with gas price.The annual cost of both coal-fired boilers and gas-fired boilers increases with electricity price,but the extent of increase is different,with coal-fired boilers having a sharper increase.Performance with environmental protection.The emissions of gas-fired boilers are dust 1.17t/year,SO2 0.49t/year,NOx 3.06t/year,and CO2 9500t/year.Compared with coal-fired boilers,the reduction rates are 99.5%,99.8%,94.5%,and 40.6%,respectively.Above all,gas-fired boilers are not advantageous in terms of economy,but they have obvious advantages in terms of environmental protection.The operation effects of the actual project verify this conclusion.This retrofit project has become a successful pilot project for the substitution of clean energy for coal in Shenyang.