WASTE-TO-ENERGY PRODUCTION CONJOINED WITH PORTLAND CEMENT PRODUCTION

Abstract

A Portland cement production (PCP) process is conjoined with a waste-to-energy (WTE) process using refuse-derived fuels (RDFs). Both processes operate simultaneously to reduce harmful compounds being discharged into the environment. The PCP and WTE processes are conjoined by borrowing a minor portion of pre-heated comminuted limestone from a PCP process feedstream and diverting it to the WTE process. Some of the pre-heated comminuted limestone is converted to CaO. The calcium compounds from the pre-heated comminuted limestone act as a fluxing agents and sorbents to bind with and remove undesired impurities, such as elemental particulate matter, excess CO.sub.2 and acid gasses associated with sulfur and chlorine that are released during the pyrolization of RDFs. The ash, char waste and reacted calcium compounds from the pyrolization process can be comingled and returned to the PCP process as a secondary cement meal feedstock.

Claims

1. A pair of simultaneous processes which are conjoined in order to share infrastructure, reduce thermal expenditures, and reduce pollution, said conjoined process comprising: a Portland cement production (PCP) process which receives comminuted limestone as a primary material input for the PCP process, said comminuted limestone being heated in a first preheater; a waste-to-energy (WTE) production process which receives refuse-derived fuels (RDF) as a primary material input and a minor portion of the comminuted limestone following its heating in the first preheater, said minor portion functioning as a secondary material input for the WTE process, and being commingled with the RDF and functioning as a fluxing agent and sorbent to bind with and remove undesired impurities during pyrolysis of the RDF in a pyrolysis gasifier during production of syngas; and means for removing pyrolysis byproducts, which include reacted comminuted limestone, carbonaceous char, and ash, from the pyrolysis gasifier, and transporting them back to the PCP process, where they are commingled with a major portion of the comminuted limestone from the first preheater, and cementitious meal materials in a second stage preheater before being sent to a high-temperature rotary kiln, where they are sintered and vitrified into cement clinkers.

2. The pair of simultaneous processes of claim 1, wherein the conjoined processes are located adjacent one another at a single manufacturing site.

3. The pair of simultaneous process of claim 2, wherein the processes for PCP production and for WTE conversion are conjoined for the following reasons: the WTE process is providing a component to the meal mix for the PCP process; the WTE process and the PCP processes are adjacent one another, and the comminuted limestone introduced into the pyrolysis gasifier is borrowed, as a minor portion, from a comminuted limestone feed stream of the PCP process, where it is also preheated before entry into the pyrolysis gasifier, with little loss of heat energy during conveyance to and introduction into the pyrolysis gasifier.

4. The pair of simultaneous process of claim 1, wherein the pair of processes are: thermally conjoined, in that heat generated in the PCP process is transferred to the WTE process; physically conjoined, in that they share colocation, being physically located adjacent one another; equipment conjoined, in that they share a common limestone comminutor; and materially conjoined, in that each process receives feedstock necessary to its own process from the other process.

5. The pair of simultaneous processes of claim 1, wherein the conjoined processes are located at different manufacturing sites, and the reacted comminuted limestone, char and ash from the waste-to-energy production is transported to the site of Portland cement manufacturing, and enters the Portland cement manufacturing process at a second-stage preheater and mixer stage.

6. A Portland cement production (PCP) process that is conjoined with a waste-to-energy (WTE) process, said conjoined process comprising the steps of: introducing pre-heated comminuted limestone and refuse-derived fuels (RDF) into a pyrolysis gasifier; comingling the pre-heated comminuted limestone and RDF within the pyrolysis gasifier; heating the comingled pre-heated comminuted limestone and RDF within the pyrolysis gasifier to create syngas, said pre-heated comminuted limestone acting as a fluxing agent and sorbent to react with and remove undesired impurities during pyrolysis of the RDF within the pyrolysis gasifier; capturing syngas produced within the pyrolysis gasifier and converting it to liquid organic fuels; extracting other reaction products from the pyrolysis gasifier, which include reacted comminuted limestone, biochar and ash; and introducing at least the comminuted limestone of the other reaction products into the PCP process as a component of a meal mix for sintering into cement clinkers.

7. The conjoined process of claim 6, wherein the biochar is separated from the other reaction products for use in the production of organic compounds selected from the group consisting of carbon black, carbon fiber, graphite, and graphene.

8. The conjoined process of claim 6, wherein the preheated comminuted limestone is borrowed, as a minor portion, from a comminuted limestone material feed stream associated with the PCP process.

9. The conjoined process of claim 8, wherein the reacted comminuted limestone from the pyrolysis gasifier is returned to the same comminuted limestone material feed stream associated with the PCP process at a point downstream whence the minor portion was borrowed.

10. The conjoined process of claim 6, wherein the PCP process and the WTE process are not conjoined merely because the WTE process is providing a component to the meal mix for the PCP process, but also conjoined both physically and thermally, in the sense that the WTE process and the PCP processes are adjacent one another, and the comminuted limestone introduced into the pyrolysis gasifier is borrowed, as a minor portion, from a comminuted limestone feed stream of the PCP process, where it is also preheated before entry into the pyrolysis gasifier, with little loss of heat energy during conveyance to and introduction into the pyrolysis gasifier.

11. The conjoined process of claim 10, wherein the PCP process and the WTE process share infrastructure, including limestone comminution equipment, transportation and conveyance systems, processing equipment, utilities, power, and human resources.

12. A conjoined manufacturing facility for Portland cement production (PCP) and the conversion of pulverized refuse-derived fuels (RDF) obtained from municipal solid waste (MSW) into usable liquid fuels, said conjoined manufacturing facility comprising: a supply of quaried limestone used as a principal feedstock of the PCP process; a comminutor for converting the quaried limestone into a comminuted limestone feedstream; a first-stage preheater for heating the comminuted limestone feedstream; a supply of RDF; a pyrolysis gasifier in which to partially convert the RDF to syngas; a second slipstream for diverting a minor portion of the comminuted limestone to the pyrolysis gasifier where it is comingled and heated with the RDF, said comminuted limestone within the pyrolysis gasifier acting as a fluxing agent and sorbent to bind with and remove undesired impurities during pyrolysis of the RDF in the pyrolysis gasifier during production of syngas; and a third slipstream for returning comminuted limestone, that has bound with undesired impurities within the pyrolysis gasifier, to the heated comminuted limestone feedstream for use as a secondary feedstock in the production of Portland cement.

13. The conjoined manufacturing facility of claim 12, wherein the syngas produced within the pyrolysis gasifier is removed from the pyrolysis gasifier by gas handling equipment and converted to liquid fuels by gas-to-liquid production processes.

14. The conjoined manufacturing facility of claim 12, wherein the processes for PCP production and for WTE conversion are conjoined for the following reasons: the WTE process is providing a component to the meal mix for the PCP process; the WTE process and the PCP processes are adjacent one another, and the comminuted limestone introduced into the pyrolysis gasifier is borrowed, as a minor portion, from a comminuted limestone feed stream of the PCP process, where it is also preheated before entry into the pyrolysis gasifier, with little loss of heat energy during conveyance to and introduction into the pyrolysis gasifier.

15. The conjoined manufacturing facility of claim 12, wherein infrastructure, including limestone comminution equipment, transportation and conveyance systems, processing equipment, utilities, power, and human resources, are shared for Portland cement production (PCP) and the conversion of pulverized refuse-derived fuels (RDF) obtained from municipal solid waste (MSW) into usable liquid fuels.

16. The conjoined manufacturing facility of claim 12, wherein biochar, one of the byproducts of pyrolysis within the pyrolysis gasifier, is separated from the comminuted limestone used within the pyrolysis gasifier for use in the production of organic compounds selected from the group consisting of carbon black, carbon fiber, graphite, and graphene.

17. The conjoined manufacturing facility of claim 12, which further comprises: a second-stage preheater and mixer, into which a first slipstream, containing a major portion of comminuted limestone from the first-stage preheater, the third slipstream, and other cementitious meal materials are fed and mixed together into a homogeneous limestone and meal mix; a high-temperature rotary kiln, which is continuously fed with the homogeneous limestone and meal mix from the second-stage preheater and mixer, and which produces cement clinkers, which are subsequently pulverized to produce powdered cement.

18. The conjoined manufacturing facility of claim 12, wherein Portland cement production (PCP) and the conversion of pulverized refuse-derived fuels (RDF) obtained from municipal solid waste (MSW) into usable liquid fuels are conjoined for the following reasons: the process for converting pulverized refuse-derived fuels (RDF) obtained from municipal solid waste (MSW) into usable liquid fuels is providing a component to the meal mix for the PCP process; and the process for converting pulverized refuse-derived fuels (RDF) obtained from municipal solid waste (MSW) into usable liquid fuels WTE process and the PCP process are adjacent one another, and the comminuted limestone introduced into the pyrolysis gasifier is borrowed, as a minor portion, from a comminuted limestone feed stream of the PCP process, where it is also preheated before entry into the pyrolysis gasifier, with little loss of heat energy during conveyance to and introduction into the pyrolysis gasifier.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 is a block diagram of a Portland cement production (PCP) process conjoined with a waste-to-energy (WTE) process.

DETAILED DESCRIPTION OF THE INVENTION

[0040] The invention will now be described in detail with reference to the attached drawing FIGURE. Referring now to FIG. 1, a conjoined process 100 includes a Portland cement production (PCP) process 100-A conjoined with a waste-to-energy (WTE) process 100-B, which operate simultaneously.

[0041] Both the PCP process 100-A and the WTE process 100-B are comprised of numerous steps. Not shown in FIG. 1 in connection with Process 100-A are other system elements generally comprised fore and aft of combined material flows of comminuted limestone and critical and corrective crushed additives selected from an array of fly ash, clay, bauxite, iron ore, gypsum and sand being handled by processing equipment customarily selected from an array of quarrying machinery, bulk transportation, crushing, weighing, conveyors, cyclones, calcining preheaters, rotary kiln with burners, heat recovery systems, condensers, clinker handling and ball milling with finished cement storage silos that would be collectively included in a typical plurality of materials, equipment and systems in the well-known art of PCP processes.

[0042] Also not shown in FIG. 1 in connection with the WTE process 100-B are other process elements generally comprised fore and aft of material flows composed of renewable refuse-derived fuels (RDF) and associated WTE processing equipment customarily selected from an array of municipal solid waste (MSW) aggregation equipment, waste handling, waste sorting, grinding and pulverizing equipment, conveying systems, sealed gates, RDF injecting screw augers, RDF pyrolysis gasifiers, shift reactors, steam generators, vessels, columns, gas clean-up systems, catalytic systems including Fischer-Tropsch-like synthesis gas-to-liquid (GTL) processing systems together with pumps, compressors, condensers, water recovery systems, heat recovery systems, upgrading hydrotreaters and hydrocrackers that would be included in a typical plurality of materials, equipment, piping and systems in the well-known art of pyrolysis derived synthesis GTL refining included in WTE process 100-B associated with the conjoined process 100. In order to pyrolyze RDF, various heating temperatures are utilized at different steps ranging from ordinary ambient temperature to 950 Celsius with accompanying process pressures applied to RDF streams ranging from one Bar of pressure to over 55 Bars.

[0043] In order to implement the PCP process 100-A, various heating temperatures are also utilized at different steps ranging from ordinary ambient temperature to increased calcining temperatures and, ultimately, to sintering temperatures of 1450 Celsius. In reference to the block diagram array of PCP process 100-A, quaried limestone 101 is selected as the process point to commence the illustration of the present invention. The quaried limestone 101, which is primarily CaCO.sub.2, is delivered to a comminutor 102, which pulverized it. The pulverized or comminuted limestone from the comminutor 102 is delivered to a first-stage preheater 103, which is a suitable heating containment vessel or cyclone preheater. In the first-stage preheater 103, the comminuted limestone is heated to approximately the same temperature as the operating temperature of a pyrolysis gasifier 107 of the WTE process 100-B, which can be as high as 950 Celsius. At this temperature, much of the pre-heated comminuted limestone is converted to calcium oxide, or CaO. A majority of the heated comminuted limestone is discharged and conveyed from a first port in the first-stage preheater 103, as a first slipstream 104, to a second-stage preheater and mixer 105.

[0044] A second slipstream 106 of preheated comminuted limestone is discharged and conveyed from a second port in the first stage-preheater 103 to the pyrolysis gasifier 107. As previously stated, the preheated, comminuted limestone in both the first and second slipstreams 104 and 106, respectively, are heated in the first-stage preheater 103 to a temperature approximately the same as the operating temperature of the pyrolysis gasifier 107. At temperatures approaching 950 Celsius, much of the pre-heated comminuted limestone, which initially was primarily calcium carbonate or CaCO.sub.2, is converted to calcium oxide, or CaO. After entering the pyrolysis gasifier 107, the heated comminuted limestone from the second slipstream 106 is conjointly comingled and heated with the refuse-derived fuels RDF 108 during a pyrolysis gasification step in the pyrolysis gasifier 107. The pyrolysis gasifier 107, used for suitable continuous pyrolysis of RDF 108 to produce syngas 109 for GTL renewable energy production, may be selected from an array of pyrolysis equipment such as rotary kilns being directly, indirectly fired and inductively heated, steam reforming reactors, from partial retorting reactors being designed as either updraft, downdraft, side-draft with normal air and oxygen injection being used to increase pyrolytic reforming of RDF 108 into syngas 109. For the present invention, full combustion of RDF 108 is not undertaken in the pyrolysis gasifier 107. Instead, syngas 109 is continuously released in the absence of oxygen by pyrolytic reactions of RDF 108 in the pyrolysis gasifier 107 typically operating at temperatures variously ranging up to 950 Celsius, with the produced syngas 109 being conveyed and delivered to downstream gas handling and gas-to-liquid (GTL) fuel production 110. The calcium carbonate and calcium oxide from the second slipstream 106 act as fluxing agents and sorbents to bind with and remove undesired impurities, which may include unreacted excess CO.sub.2, acid gasses associated with sulfur, chlorine, as well as other elemental particulate matter generated during the production of syngas 109. The adsorbed acid gases and particulate matter would likely be detrimental to downstream equipment or would reduce the efficiency of downstream Fischer-Tropsch catalytic GTL conversion reactions and other refining methods associated with the WTE Process 100-B. Common products of GTL fuel production are straight-chain alkanes, with carbon atom content of 10 or greater which can be used as diesel fuels and jet fuels. During the combined pyrolysis process to produce syngas 108, most of the remaining calcium carbonate (CaCO.sub.2) from the second slipstream 106 is converted to calcium oxide (CaO). Byproducts of the pyrolysis gasification step also include carbonaceous char and ash.

[0045] The reacted limestone, biochar and ash 111 are discharged from the pyrolysis gasifier 107 and transported to the second-stage preheater and mixer 105 via a third slipstream 113, thereby being returned to the PCP process 100-A, where it is combined with the preheated comminuted limestone from the first slipstream 104 and cementitious meal materials 114. The cementitious meal materials 114 can include limestone and other add mixtures of fly ash, clay, bauxite, iron ore, gypsum and sand being corrective and critical crushed additives. The reacted limestone, biochar and ash 111, the pre-heated comminuted limestone from the first slipstream 104, and the cementitious meal materials 114 are then mixed and heated to calcinating temperatures in a second-state preheater and mixer 105 for discharge as a homogeneous limestone and meal mix 115, which is conveyed into a high-temperature rotary kiln 116. Inside the high-temperature rotary kiln 116, the homogeneous limestone and meal mix 115 is superheated to sintering temperatures, which typically reach 1450 Celsius, thereby producing cement clinkers 117, which are discharged from the high-temperature rotary kiln 116. The cement clinkers 117 are then converted to cement, by pulverization, in a downstream process, which is well known in the art. In order to minimize any process heat and pressure loss during the transport of materials between the PCP process 100-A and the WTE process 100-B, and particularly during the delivery of a minor portion of the preheated comminuted limestone from the first-stage preheater 103 the pyrolysis gasifier 107, as well as the delivery of the reacted limestone, char and ash 111 from the pyrolysis gasifier 107 to the second-stage preheater and mixer 105, sealed gates and injection screw augers, which are well known to the art of material handling, may be selected to successfully transport these materials. Char that is extracted along with reacted limestone and char from the pyrolysis gasifier 107, may be optionally separated from the reacted limestone and ash as biochar 112, which can be used for the manufacture of, carbon fiber, graphite, graphene (a graphite allotrope of carbon containing numerous double bonds) or other advanced materials made from carbon. Another option is to separate the carbonaceous char and ash from the reacted limestone, before all three components enter the second-stage preheater and mixer 105, for use as additional source of renewable energy for the downstream high-temperature rotary kiln 116 during the high energy sintering process which forms cement clinkers 117.

[0046] From the previous detailed description of the invention, it should be clear that the previously disclosed art in the Description of the Related Art section fails to teach the innovation of the present invention. The present invention solves impracticalities and improves the shortcomings of Boardman, Clayson, Carlson and Liu by providing an improved method of renewable energy production independent of local oil shale production for its feedstock. For the present invention, comminuted limestone borrowed from a concurrent and co-located cement production process is used as a substitute sorbent input in place of spent oil shale char, with said limestone also containing calcium compounds comingled together with refuse derived fuel (RDF) originated from municipal solid waste (MSW) and continuously heated to produce cleaner renewable energy from synthesis gasses.

[0047] Another feature of the present invention, that distinguishes it from the disclosed related art, is that there is no return of the calcium compounds used as sorbents to their original chemical state or location in the specified calcium cycle. Instead, reacted comminuted limestone borrowed from the Portland cement manufacturing process is returned to that process downstream whence it was borrowed. Therefore, the present invention is not making claims as to chemical reactions of calcium but, rather, is implementing a conjoining of cement production with renewable energy production.

[0048] The Carlson reference (U.S. Pat. No. 9,169,440 B2) indicates that spent oil shale char contains a sufficient plurality of calcium (with available oxygen and carbon) which may react as a sorbent of produced acid gasses generated during joint MSW pyrolysis. Spent oil share char depleted of hydrocarbons is similar in chemical composition to raw limestone both having a plurality of calcium. With limestone borrowed from the Portland cement manufacturing process substituting for spent oil shale, similar resulting chemical reactions with detected acid gasses produced during joint MSW pyrolysis cause the formation of an array of trace byproduct calcium salts (such as calcium silicates and calcium aluminates along with calcium phosphate, calcium chloride, calcium sulfate, or calcium nitrate) with some excess produced water which are useful salts available for the cement production process. After the purposeful absorption and scrubbing of unwanted acid gasses and other potential carbon dioxide during RDF pyrolysis, these produced calcium salts or calcium carbonate are not retreated and then reused for scrubbing but are returned in a continuous material stream to the borrowed source to be a supplemental part of and act as components and well-known chemical enhancements to the strength and durability of Portland cement (See, for example, Neto, J. S. A., et. al., Effects of Sulfates on the Hydration of Portland CementA review, Construction and Building Materials. Volume 279, 12 Apr. 2021, 122428). Thus, the comminuted limestone, borrowed from the Portland cement manufacturing process, acts to both purify renewable synthesis gasses and to improve the cement products. Contrary to the heretofore disclosed Liu reference, the present invention discloses much different mass ratios of organic matter to inorganic matter for conducting continuous and non-linear thermal reduction process methods. While some calcium and CO2 reactions may transpire, the present invention focuses on other arguments and reactions of calcium. As such, the present invention is not calcium looping as currently known and published in the public domain.

[0049] In the known art, the calcium looping process, which is impractical for use for the present invention, is a closed cycle that always ends where it starts. The present invention, on the other hand, removal of acidic gas species found in synthesis gasses produced during pyrolysis of refuse derived fuels (RDF) obtained from Municipal Solid Wastes (MSW) is accomplished by continuously borrowing a minor portion of a comminuted calcium particle feed stream that is being conveyed to a cement making process, and continuously introducing that minor portion into a separate pyrolytic process, where that minor portion of particles is comingled with RDF and serves as a sorbent of harmful acid gasses and other harmful compounds, which are byproducts of the pyrolytic process, said minor portion of particles being at least partially converted to calcium salts. The minor portion of particles, after having performed its sorbent function, is continuously returned to the comminuted calcium particle feed stream, downstream of its previous removal, for further processing in the cement manufacturing process.

[0050] Unlike the heretofore disclosed related art, the present invention essentially uses calcium attrition and other chemical reactions selected from an array of reactions including calcium sulfation, which are typically undesirable reactions in the aforementioned calcium looping systems. The heated comminuted limestone borrowed from the Portland cement manufacturing process acts as a primary sorbent to capture reactive materials being comprised of undesirable elemental species that may be prevalent in gasification methods that are used in the production systems of renewable energy. Additionally, the borrowed comminuted limestone may also capture some carbon dioxide during the comingled calcium/RDF pyrolysis process. Friability of calcium oxide into smaller particles by attrition and kinetic action contained in, for example, a rotary kiln gasifier, it being selected from an array of similarly suitable and common gasifier equipment, is useful to create greater surface processing of concurrent elements using more available particles in motion. Furthermore, sulfur can be acidic and is a poisonous and polluting species persistent in synthesis gasses derived from pyrolysis of RDF. For the present invention, the calcium sulfation reaction and other similar calcium reactions are useful for removing and scrubbing synthesis acid gasses during pyrolysis in the presence of heated comminuted limestone. The reactions of indirect and direct calcium sulfation are given by CaO+SO2+ O2.fwdarw.CaSO4 and CaCO3+SO2+ O2.fwdarw.CaSO4+CO2 respectively. The difficult reversibility of these acidic reactions creates calcium salts that are useful compounds for the production of Portland cement. Thus, by conjoining renewable energy production with cement production, the discharge of pollution into the environment is remediated.

[0051] Although only one embodiment of the invention has been shown and described, it will be obvious to those having ordinary skill in the art that changes and modifications may be made thereto without departing from the scope and the spirit of the invention. For example, although the preferred conjoining of Portland cement manufacturing and waste-to-energy production is accomplished at a single site, where vertical integration maximizes the sharing of infrastructure, transportation systems, processing equipment, utilities, power, and human resources, it is also envisioned that the conjoining of the two processes can occur with far less vertical integration. For example, The Portland cement manufacturing and waste-to-energy production may be operated at different sites, using two sources of comminuted limestone, and transporting the reacted limestone, char and ash from the waste-to-energy production to the Portland cement manufacturing process site at the second-stage preheater and mixer 105 stage. However, such an arrangement would certainly not be optimum, as significant inefficiencies would occur. Those inefficiencies would include, but would certainly not be limited to, unnecessary duplication of processing equipment and unrecoverable loss of energy, in the form of heat, during the transport of the reacted limestone, char and ash to the Portland cement production site.