The MHD generator is well established in theory and practice as utilizing high temperature, high velocity, ionized fluid to generate electric power as the fluid is directed through a static magnetic field. Practicality dictates a temperature range for the gases of at least 4000 F. Potassium compounds, referred to as "seed," are injected into the combustion chamber for enhancing the ionization of the fluid flowing through the MHD channel.
If an ample supply of clean fuel, such as gas and oil, is available and the combustion air can be brought up to a temperature of at least 2500 F., the resulting gaseous products of combustion after traversing the channel are ejected from the MHD channel and subsequently utilized to convert water to steam. The steam can then be used to power a turbine which is coupled to an electric generator. The total electric power generated by the MHD channel and steam cycle can then be compared to the energy input to the system to obtain an efficiency of approximately 50%.
Coals is in abundant supply and it is, therefore, desirable that its energy be made available to the MHD generator. There are various systems for converting solid coal into relatively low BTU content gas for the MHD generator combustor. Unfortunately, coal-to-gas conversion runs into the vicious problem of compensating for the high ash and sulfur content of this form of fossil fuel. The ash is a polluting solid particulate in the final discharge to the atmosphere. Sulfur compounds may also be discharged to the atmosphere, as at least noxious pollutants, if not corrosive and poisonous threats to the environment.
The present problem must be solved with a system which provides gasification of coal while reducing the particulate material and sulfur content of the gas to an acceptable level. Further, the combustion air required for the burning of the coal gas and its gasification must be heated by the discharge of the products of combustion from the MHD channel. Briefly, pollution to the environment is controlled and heat energy is conserved.