Sulfur removal by sorbent injection in secondary combustion zones

An apparatus for combusting a carbonaceous fuel comprising carbon, sulfur, and noncombustibles, the apparatus comprising:

• (a) a primary combustion chamber having a head end and an exit end connected by a peripheral wall;
• (b) oxidant introduction means for introducing a flow of oxidant into the primary combustion chamber intermediate the ends in a manner to establish a high velocity swirling flow field within the primary combustion chamber;
• (c) fuel introduction means in communication with the primary combustion chamber for introducing the fuel into the primary combustion chamber in a pattern so that substantially all of the fuel is intercepted by the swirling flow field and most of the carbon contained in the fuel is converted to oxides of carbon before the fuel reaches the wall of the primary combustion chamber;
• (d) input regulation means for independently regulating the input velocities and mass flow rates of the oxidant and the fuel so that the fuel is combusted in the presence of the oxidant in the primary combustion chamber under substoichiometric combustion conditions to form liquid slag and gaseous combustion products comprising sulfur and oxides of carbon, wherein substantially all of the carbon content of the fuel is converted to oxides of carbon before the gaseous combustion products leave the primary combustion chamber, the temperature within the primary combustion chamber is maintained above the ash fusion temperature of the fuel, and a majority of the noncombustibles are driven to the peripheral wall of the primary combustion chamber to form treated gaseous combustion products that leave the primary combustion chamber and have a temperature above the ash fusion temperature of the fuel and a noncombustible content that is substantially reduced with respect to the noncombustible content of the fuel for delivery to an associated heat-utilization equipment;
• (e) slag removal means in fluid communication with the primary combustion chamber for removing a majority of the liquid slag from the primary combustion chamber;
• and
• (f) sorbent introduction means in communication with the treated gaseous combustion products for introducing a sorbent having a first sulfur capture capacity into the treated gaseous combustion products downstream from the primary combustion zone substantially as the treated gaseous combustion products are delivered to the heat-utilization equipment, the sorbent introduction means being adapted so that the sorbent is rapidly mixed with the treated gaseous combustion products to calcine the sorbent, the calcined sorbent having a second sulfur capture capacity that is greater than the first sulfur capture capacity, so that the sulfur content of the treated gaseous combustion products is capable of being substantially reduced with respect to the sulfur content of the fuel.

In a process for combustion of sulfur-containing particulate carbonaceous fuel wherein oxidizer gas and particulate fuel are introduced into a substantially cylindrical combustion zone and wherein the input velocities, relative mass-flow rates and temperatures are regulated to keep combustion temperatures in said zone above the ash-fusion temperature of non-combustible constituents of the fuel while minimizing the concentration of volatilized and liquid slag in the output gaseous products of combustion, the improvement comprising the steps of:

• (a) preheating said oxidizer gas and introducing the preheated oxidizer gas into said zone in a manner to establish a high-velocity swirling flow of a mixture comprising oxidizer and combustion products within said zone;
• (b) injecting particulate fuel into said zone near the center of one end thereof in a pattern such that substantially all of the fuel particles are intercepted by said swirling flow and most of the carbon contained in the particles is converted to oxides of carbon before the particles exit from said zone;
• (c) regulating the oxidizer and fuel input temperatures, velocities and mass-flow rates to maintain a relatively fuel-rich combustion regime within a longitudinally-extending central portion of the combustion zone, provide a relatively oxygen-rich annular region adjacent the periphery of said zone, drive substantially all the slag content of the fuel to the periphery of said zone, and keep the temperature of the gaseous combustion products substantially higher than the ash-fusion temperature of the non-combustible constituents of the fuel;
• (d) collecting substantially all liquid slag entrained in said combustion products, separately disposing of all slag, and conducting thermal energy-carrying gaseous products to an associated heat utilization equipment;
• (e) combining with said gaseous products, substantially as such products enter the heat utilization equipment,
• (i) sufficient calcium-containing sorbent to provide a calcium-to-sulfur molar ratio in the range from about 2 to about 5 and
• (ii) sufficient supplementary oxidizer to keep the temperature at which said sorbent initially contacts sulfur constituents of the gaseous products within the range from about 1600.degree. F. to about 2300.degree. F.;
• (f) with said calcium-containing sorbent being introduced into the gaseous products before such products pass into the heat utilization equipment, said supplementary oxidizer being mixed with the gaseous products after removal of substantially al non-combustible mineral constituents therefrom;
• and
• (g) maintaining a time-temperature profile for the sorbent in transit to and through the heat utilization equipment which enables the sulfur sorbent to react with and capture a preponderance of the sulfur constituents at an effective capture temperature of less than about 2300.degree. F., while maintaining a stoichiometry in the heat utilization equipment of from about 1.1 to about 1.3.

A process for combusting a carbonaceous fuel comprising carbon, sulfur, and noncombustibles, the process comprising the steps of:

• (a) introducing a flow of oxidant into a primary combustion zone having a head end and an exit end connected by a peripheral wall, the flow of oxidant being introduced intermediate the ends in a manner to establish a high velocity swirling flow field within the primary combustion zone;
• (b) introducing the fuel into the primary combustion zone in a pattern so that substantially all of the fuel is intercepted by the swirling flow field and most of the carbon contained in the fuel is converted to oxides of carbon before the fuel reaches the wall of the primary combustion zone;
• (c) independently regulating the velocities and mass flow rates of the oxidant and the fuel so that the fuel is combusted in the presence of the oxidant in the primary combustion zone under substoichiometric combustion conditions to form liquid slag and gaseous combustion products comprising sulfur and oxides of carbon, wherein substantially all of the carbon content of the fuel is converted to oxides of carbon before the gaseous combustion products leave the primary combustion zone, the temperature within the primary combustion zone is maintained above the ash fusion temperature of the fuel, and a majority of the noncombustibles are driven to the peripheral wall of the primary combustion zone to form treated gaseous combustion products that leave the primary combustion zone and have a temperature above the ash fusion temperature of the fuel and a noncombustible content that is substantially reduced with respect to the noncombustible content of the fuel for delivery to an associated heat-utilization equipment;
• (d) removing a majority of the liquid slag from the primary combustion zone;
• and
• (e) introducing a sorbent having a first sulfur capture capacity into the treated gaseous combustion products downstream from the primary combustion zone substantially as the treated gaseous combustion products are delivered to the heat-utilization equipment and rapidly mixing the sorbent with the treated gaseous combustion products to calcine the sorbent, the calcined sorbent having a second sulfur capacity that is greater than the first sulfur capture capacity, so that the sulfur content of the treated gaseous combustion products is capable of being substantially reduced with respect to the sulfur content of the fuel.

A process for combusting a carbonaceous fuel comprising carbon, sulfur, and noncombustibles, the process comprising the steps of:

• (a) introducing oxidant into a primary combustion zone having a head end and an exit end connected by a peripheral wall, the oxidant being introduced intermediate the ends in a manner to establish a high velocity swirling flow field within the primary combustion zone;
• (b) introducing the fuel into the primary combustion zone near the center of one end in a pattern so that substantially all of the fuel is intercepted by the swirling flow field and most of the carbon contained in the fuel is converted to oxides of carbon before the fuel reaches the wall of the primary combustion zone;
• (c) independently regulating the velocities and mass flow rates of the oxidant and the fuel so that the fuel is combusted in the presence of the oxidant in the primary combustion zone under stoichiometric combustion conditions to form liquid slag and gaseous combustion products comprising sulfur and oxides of carbon, wherein substantially all of the carbon content of the fuel is converted to oxides of carbon before the gaseous combustion products leave the primary combustion zone, the temperature within the primary combustion zone is maintained above the ash fusion temperature of the fuel, and a majority of the noncombustibles are driven to the peripheral wall of the primary combustion zone to form treated gaseous combustion products that leave the primary combustion zone and have a temperature above the ash fusion temperature of the fuel and a noncombustible content that is substantially reduced with respect to the noncombustible content of the fuel for delivery to an associated heat-utilization zone;
• (d) removing a majority of the liquid slag from the primary combustion zone;
• (e) passing the treated combustion products leaving the primary combustion zone through a transition zone;
• (f) introducing a sulfur sorbent into the treated gaseous combustion products downstream from where the treated gaseous combustion products leaves the primary combustion zone substantially as the treated gaseous combustion products are delivered to the heat-utilization zone, the treated gaseous combustion products having a temperature above the ash fusion temperature of the fuel, and rapidly mixing the sorbent with the treated gaseous combustion products to calcine the sorbent and to form a mixture comprising the treated gaseous combustion products and calcined sorbent, then calcined sorbent having a greater sulfur capture capacity than the introduced sorbent;
• and
• (g) after step (f), reducing the temperature of the mixture to prevent any significant deadburn of the calcined sorbent so that the calcined sorbent is capable of removing sulfur from the treated gaseous combustion products to substantially reduce the sulfur content of the treated gaseous combustion products with respect to the sulfur content of the fuel.

A process for combusting a carbonaceous fuel comprising carbon, sulfur, and noncombustibles, the process comprising the steps of:

• (a) introducing a flow of oxidant into a primary combustion zone having a head end and an exit end connected by a peripheral wall, the flow of oxidant being introduced intermediate the ends in a manner to establish a high velocity swirling flow field within the primary combustion zone;
• (b) introducing the fuel into the primary combustion zone in a pattern so that substantially all of the fuel is intercepted by the swirling flow field and most of the carbon contained in the fuel is converted to oxides of carbon before the fuel reaches the wall of the primary combustion zone;
• (c) independently regulating the velocities and mass flow rates of the oxidant and the fuel so that (i) the fuel is combusted in the presence of the oxidant in the primary combustion zone under substoichiometric combustion conditions to form liquid slag and gaseous combustion products comprising sulfur and oxides of carbon, (ii) substantially all of the carbon content of the fuel is converted to oxides of carbon before the gaseous combustion products leave the primary combustion zone, (iii) the temperature within the primary combustion zone is maintained above the ash fusion temperature of the fuel, and (iv) a majority of the noncombustibles are driven to the peripheral wall of the primary combustion zone to form treated gaseous combustion products that leave the primary combustion zone and have a temperature above the ash fusion temperature of the fuel and a noncombustible content that is substantially reduced with respect to the noncombustible content of the fuel;
• (d) removing a majority of the liquid slag from the primary combustion zone;
• (e) introducing a sorbent having a first sulfur capture capacity into the treated gaseous combustion products downstream from the primary combustion zone substantially as the treated gaseous combustions products are introduced into an associated heat-utilization zone and rapidly mixing the sorbent with the treated gaseous combustion products to calcine the sorbent, thereby forming a mixture of the sorbent and the treated gaseous combustion products, the calcined sorbent having a second sulfur capture capacity that is greater than the first sulfur capture capacity so that the sulfur content of the treated gaseous combustion products is capable of being substantially reduced with respect to the sulfur content of the fuel;
• (f) introducing the mixture into the heat utilization zone for recovering heat energy from the mixture and for reducing the temperature of the mixture to below about 2300.degree. F. to prevent any significant dead burn of the sorbent;
• and
• (g) subsequent to step (f), removing sorbent from the mixture.

In an apparatus for combustion of a carbonaceous fuel comprising carbon, sulfur, and non-combustibles in a combustion chamber wherein the fuel input rate relative to the oxidizer input rate is regulated to maintain combustion conditions such that most of the carbon is converted to oxides of carbon contained in gaseous combustion products, and most of the non-combustibles are deposited as liquid slag, the gaseous combustion products containing sulfur constituents, such apparatus being further characterized by:

• (a) means for separating most of the non-combustibles from the gaseous combustion products thereby providing treated gaseous combustion products relatively free of ash for delivery to an associated heat-utilization equipment;
• (b) means for delivering said treated gaseous combustion products to said heat utilization equipment;
• and
• (c) sorbent introduction means in communication with said treated gaseous combustion products for introducing a sorbent having a first sulfur capture capacity into said treated gaseous combustion products so that the sulfur content of said gaseous combustion products is capable of being substantially reduced with respect to the sulfur content of the fuel, the sorbent introduction means being downstream from the combustion chamber and being located for introduction of sorbent into the treated gaseous products substantially as said treated gaseous combustion products are delivered to the heat-utilization equipment, the sorbent introduction means being adapted so that the sorbent is rapidly mixed with said gaseous combustion products to calcine the sorbent, the calcined sorbent having a second sulfur capture capacity that is greater than the first sulfur capture capacity.

In a process for combusting a carbonaceous fuel comprising carbon, sulfur, and non-combustibles in a combustion zone wherein the fuel input mass-flow rate relative to an oxidizer input mass-flow rate is regulated to maintain combustion conditions such that most of the carbon is converted to oxides of carbon contained in gaseous combustion products and most of the non-combustibles are deposited as liquid slag, the improvement characterized by:

• (a) separating liquid slag from the gaseous combustion products, thereby providing gaseous combustion products relatively free of ash for delivery to an associated heat-utilization zone, the gaseous combustion products containing sulfur constituents;
• (b) delivering the gaseous combustion products to the heat-utilization zone;
• and
• (c) introducing a sorbent having a first sulfur capture capacity into the gaseous combustion products downstream from the combustion zone substantially as the gaseous combustion products are delivered to the heat-utilization zone and rapidly mixing the sorbent with the gaseous combustion products to calcine the sorbent, the calcined sorbent having a second sulfur capture capacity that is greater than the first sulfur capture capacity so that the sulfur content of the gaseous combustion products is capable of being substantially reduced with respect to the sulfur content of the fuel.