31 as SR P 35) 2 O R 4 239 996 United States Patent (19) 11 4,239,996 Bhada et al. 45) Dec. 16, 1980 54 POTASSUM CARBONATE RECOVERY 2,993,753 7/1961 Collins, Jr. ........................... 423/82 3,020, 195 2/1962 Casciani et al. ... 42.3/83 75 Inventors: Rohinton K. Bhada, Homeworth; 3,026,240 3/1962 Matty ................ ... 42.3/209 Howard B. Lange, Jr.; Stephen S. 3,127,237 3/1964 Markant ............ ... 423/428 Strom, both of Alliance, all of Ohio 3,153,609 10/1964 Markant et al. .......... ... 423/82 3,210,235 10/1965 Ferrigan, Jr. et al..... ... 423/183 (73) Assignee: The Babcock & Wilcox Company, 3,379,903 4/1968 Rosner ................................... 30/1 New Orleans, La. 3,401,010 9/1968 Guerrieri ........... ... 42.3/428 3,508,863 4/1970 Kiminki et al. ... ... 423A1.89 (21) Appl. No.: 582,066 3,873,860 3/1975 Bergman et al. ...................... 310/11 22 Filed: May 29, 1975 Primary Examiner-Delbert E. Gantz (51) Int. C.’...................... HO2K 45/00; C01B 17/02; Assistant Examiner-Gary P. Straub COD 7/00 Attorney, Agent, or Firm-Robert J. Edwards; John L. (52) U.S. C. .................................. 310/11; 423/574 L; LaPierre 423/244; 423/186; 42.3/563; 42.3/428 (58) Field of Search ........................... 310/11, DIG. 3; 57 ABSTRACT 423/186, 189, 193,200, 208, 427, 428, 56,563, A process for reacting potassium carbonate with the 152, 244, DIG. 3, 574 sulfur in an MHD gas to form potassium sulfate and for recovering the potassium carbonate for recycle as a 56 References Cited seeding material for the MHD gas. U.S. PATENT DOCUMENTS 1,979, 5 10/1934 Fricke et al. ......................... 423/428 3 Claims, 2 Drawing Figures WASE EAT WAPOR GEN SEAM CEAN FLUE GAS HaO, HaN,CO, CO2H2S PART1culATE STAM 4. O COLECTOR WAS, ET O2 KCOKS, HS,CO, O2N2H2O, ASH e C SE O 28 CLAUS HaSCO2H2N2, PLAN VENTURI H2O, CO SORB. SEPARATOR COMUSTOR COMUSTOR SLAG DSSOLVE ANs AR HO COO2N2H2O K2SK2CO3K2SO4. ASA,6HAR PRECARBON- ASH, CHAR H2S,CO2 ATION VENT CARFER ODING TANK SEPARATOR Dec. 16 U.S. Patent 9 1980 4 239,996 4,239,996 1. 2 heated air and carbonaceous fuel, preferably coal, are POTASSIUM CARBONATE RECOVERY fired in the combustor 10 to produce a high temperature gas, and potassium carbonate crystals are added to the BACKGROUND OF THE INVENTION combustor 10 either by mixing with the fuel or intro The present invention relates to the use of potassium duction into the combustion gas. The quantity of potas carbonate as the ionizing and clean-up agent of a sulfur sium carbonate added to the combustor 10 is controlled laden working gas for a magnetohydrodynamic electric to achieve the desired level of gas ionization and to generator wherein the potassium carbonate reacts with react with the sulfur in the fuel to form potassium sul the sulfur to form potassium sulfate and more particu fate. larly to a thermochemical process for recovering the 10 The high temperature gas including potassium sul potassium carbonate from the potassium sulfate. fate, carbon dioxide, oxygen, nitrogen and ash and dis The theory of magnetohydrodynamic (MHD) elec charging from the combustor 10 is conveyed to a mag tric power generation has been known for many years, netohydrodynamic (MHD) electric generator 12 of the and potential for practical application of the MHD character disclosed in U.S. Pat. No. 3,328,612. The gas principle became a reality when it was discovered that 15 leaving the MHD generator 12 is tangentially intro required gas conductivity could be obtained in combus duced into a centrifugal type separator 14 for the re tion gases attemperature as low as 3500' F. with the use moval of slag and is thereafter conveyed to a waste heat of a seeding material such as potassium carbonate. However, notwithstanding the solution of the gas con type vapor generator 16 of the character disclosed in ductivity problem the MHD generator continued to be 20 U.S. Pat. No. 2,754,807 wherein the heat of the gas is economically unattractive as a result of costs arising out used to generate steam thereby reducing the gas tem of the need for the replacement of seeding material and perature from about 2800 F. to approximately 300 F. the clean-up of MHD exhaust gas to satisfy present day The cooled gas is thence conveyed to a collector 18 for pollution criteria. the removal of potassium sulfate crystals and residual 25 ash particulates. The collector 18 may be in the form of SUMMARY OF THE INVENTION an electrostatic precipitator. The gas discharged from The invention provides a process wherein the MHD the collector 18 includes carbon dioxide, nitrogen and gas is cleaned through the removal of sulfur and the water vapor and is sufficiently clean to satisfy present potassium carbonate is recovered for use as a seeding day requirements for emission to atmosphere. material. 30 The potassium sulfate crystals and residual ash partic Accordingly, there is provided a process whereby ulates recovered by the collector 18 are conveyed to a potassium carbonate is admitted to an MHD combustor mixing tank 20 to be combined with carbonaceous fuel, and combined with the sulfur-laden fuel or combustion preferably coal, and a solution including potassium salts gas to react with the sulfur and form potassium sulfate to form a liquid of a consistency suitable for spraying and to induce ionization of the gas preparatory to its use 35 into a smelter type furnace 22 of the character disclosed as the working fluid in an MHD generator. Recovery of in U.S. Pat, No. 2,879,838. The carbonaceous fuel added the potassium carbonate is achieved by removing potas to the mixing tank 20 is in sufficient quantity to provide sium sulfate crystals from the MHD exhaust gas and the carbon necessary to sustain a thermal reduction firing the potassium sulfate in the presence of carbon process within the furnace 22. The discharge from the and under reducing conditions to obtain a molten smelt 40 mixing tank 20 is conveyed to a nozzle 24 which sprays including potassium sulfide and a gas including potas the mixture into furnace 22 wherein it is incinerated sium salts, the latter are recovered from the gas and are under a reducing atmosphere to form a smelt on the mixed with the smelt and water to form a solution in furnace hearth 26 including potassium sulfide, potas cluding potassium sulfide and potassium carbonate. The sium carbonate, potassium sulfate and residuals of char solution is contacted with carbon dioxide in sufficient 45 amount to form a precarbonated solution including and coal ash, Auxiliary fuel burners may be provided potassium carbonate and potassium bisulfide. A slurry for furnace 22 to maintain the smelt bed temperature in including potassium bicarbonate is added to the precar excess of the 1800 F. required to insure substantial bonated solution to form a mixture including potassium reduction of potassium sulfate to potassium sulfide. The bicarbonate and potassium hydrosulfide. Heat is applied 50 total combustion air supplied to the furnace 22 is main to the mixture to produce a vapor including hydrogen tained in the range of 60 to 90 percent of stoichiometric sulfide and a slurry including potassium carbonate crys air with 40 to 60 percent of the air being admitted tals, and the slurry is separated into potassium carbonate around the smelt bed to support the reduction process crystals and a saturated solution including potassium and the remaining air being introduced above the bed to salts. achieve partial combustion of the high temperature gas 55 produced by the incineration process. BRIEF DESCRIPTION OF THE DRAWING The gas leaving the furnace 22 includes potassium The drawing is a schematic representation of a system carbonate and potassium sulfide fume, hydrogen sulfide, embodying the invention as related to a process for carbon monoxide, carbon dioxide, nitrogen, water recovering potassium carbonate after its having been vapor and ash is conveyed to a waste heat vapor genera used as the ionizing and clean-up agent of a sulfur-laden tor 28 wherein the heat of the gas generates steam and working fluid for an MHD electric generator. the gas temperature is reduced from about 2000 to approximately 300' F. The vapor generator 28 is pro DESCRIPTION OF THE PREFERRED vided with a hopper 32 to collect potassium salts and EMBODIMENT 65 ash which have adhered to internal surfaces. These In the drawing there is illustrated a combustor 10 of particulates are removed during periodic cleaning of the type including a cyclone combustion chamber of the the surfaces and are passed from the hopper 32 to a character disclosed in U.S. Pat, No. 3, 179,074. Pre dissolving tank 34. 4,239,996 3 4. The cooled gas discharged by the vapor generator 28 wardly through the stripper 50A and strips the hydro is conveyed to a venturi type scrubber 36 of the charac gen sulfide gas from the gravitating mixture. ter disclosed in U.S. Pat. No. 3,284,064. The gas is con The gas leaving the stripper 50A includes hydrogen tacted by a liquid spray in the throat of venturi scrubber sulfide, water vapor and traces of carbon dioxide and is 36 and is thereafter conveyed to a centrifugal separator conveyed to a condenser 52 wherein indirect heat ex 38 situated immediately downstream flow-wise of the change with a coolant e.g., water, removes the water venturi scrubber 36 and connected thereto by a duct 40. vapor from the gas as condensate.