A SYSTEM AND PROCESS FOR WASHING MONO NITROXYLENES, RECOVERING AND REUSING REACTION WASTES

CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY

The present application claims priority from Indian provisional patent application no. 202221010495 filed on the 25 ^th day of February 2022, the details of which are incorporated herein by a reference.

TECHNICAL FIELD

The present invention is related to a system and a process for the washing of nitro-mass comprising mono nitroxylenes and an integrated method of treatment of wastewater from mono nitroxylenes production. The present invention in particular relates to a system and a process for recovery of fresh water from slurry mixture of mono nitroxylene.

BACKGROUND OF THE INVENTION

In the industrial production of nitro compounds, such as mono nitro compounds or dinitro compounds, significant amounts of acidic organic by-products are formed. In mono nitroxylene production the main by-product species are nitro xylenols (i.e., an organic acid), in mono nitrobenzene production the main by-product species are nitrophenols, and in nitrotoluene production they are nitro cresols. Other minor organic by-product impurities are also present. In addition to byproducts, other impurities present in the nitrated product are sulfuric acid catalyst and unreacted starting reactants such as xylene, benzene, or toluene, in the corresponding nitration processes.

The organic acid by-products present in the crude product stream are particularly undesirable since they can adversely affect later users of the products (i.e., use in other processes, such as in the production of aniline in the case of nitrobenzene). The contaminants are therefore typically required to be removed through a series of process steps. These process steps have been described both in the prior art patents and in the literature, e.g., G. Booth, “Nitro Compounds, Aromatic”, in “Ullmann's Encyclopaedia of Industrial Chemistry, 7th Ed.”, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, (2005).

The typical prior art steps for removing by-products and impurities from the stream of nitrated product comprise the steps of water washing, alkaline washing and neutral washing.

Having removed inorganic acids (i.e., in the water washer), organic acids (i.e., in the alkaline washer) and hydroxyl-nitro-aromatics (i.e., in the neutral washer), the next step is to neutralize the nitro mass which is alkaline in nature after alkali wash to remove residual organic reactants. Some of the reactions to produce nitroaromatics are run with an excess of the organic feed reactants. For example, in the preparation of mono nitrobenzene, excess of benzene is used, wherein the excess of benzene used remains in the crude product stream. Therefore, the product leaving the washing train is typically sent, directly or indirectly, to either a stripper or a distillation column to recover the excess organic reactant, which up to this point in the process remains in solution with the nitrated product.

A distillation column can be used to remove excess organic feed reactants from the nitrated product. The main operating difference from steam stripping is that, in a distillation column, heat is introduced indirectly via a reboiler. As a result, no water condensate forms in the column and a “dry” nitrated products are obtained. Without water in the final product, salts that were dissolved in the water entrained with the organic product feed to the column precipitate out, leading to plugging of the column or downstream equipment. Some of this precipitate is carried all the way through with the nitrated product into the downstream process.

The organic product leaving the alkaline washing step typically carries with it a small amount of the base (e.g., sodium hydroxide) used in the extraction, and a small amount of the salt formed in the alkaline washer (e.g., sodium nitrophenolates in the case of nitrobenzene production). More specifically, this residual salt is carried by small water droplets entrained in the organic product leaving the alkaline washing step, rather than by the organic product itself. As discussed below, this entrained salt, if not properly removed, can present a significant challenge in the operation of the downstream equipment. To minimize the effect of salt carry-over, one or more “neutral washers” such as water having a substantially neutral pH are introduced. In the process of neutral washing multiple units can be used, operated in crossflow or counter-current-flow arrangements.

In general, properly designed neutral washers are effective in removing entrained salt from the nitrated product. However, neutral washers are also operationally sensitive. This sensitivity is exhibited by a tendency of the two phases (i.e., water and nitrated product) in the washing operation to form one relatively emulsified phase that does not properly settle out into the two phases. The resulting effect is that excessive water can be carried over into the downstream unit operations, which can lead to production shutdowns. This formation, of a single emulsified phase, can occur if the operation on the washer/separator is allowed to drift out of design conditions (e.g., flow rates, mixing intensity, temperature, etc.). It also tends to occur more frequently as one pushes the neutral washer to ever cleaner product, for example by using more than one neutral washer in counter-current flow mode or a larger flow of water in a single neutral washer. Either one of the latter two conditions are desired to achieve significant salt extraction but they are typically not practical without costly separation enhancing equipment such as electrophoresis or coalescers. Even when good separation of the two fluids (i.e., water and nitrated product) occurs within the neutral washer, whether or not enhanced by for example a coalescer, there is still a significant amount of water entrainment with the exiting product, visible by the cloudy or milky appearance of the nitrated product. This appearance is due to water present, as a “colloidal” stable form, in the product. As noted above, it is the entrained water that carries the bulk of the salt entrained in the nitrated product leaving the neutral washing stage. This concentration of “colloidal” water droplets in the product cannot be easily decreased under the typical operating conditions of the neutral washer.

Therefore, there is a long felt need to develop an efficient process for the washing of mono nitroxylenes and wastewater treatment in the production of mono nitroxylenes which reduces the amount of impurities and by-products and enables recycle, reuse, and recovery of ammonium hydroxide/ammonia and reusable water.

OBJECTS OF THE INVENTION

It is an object of this invention to provide a process for removing impurities from a product stream comprising mono nitroxylenes.

It is another object of the invention to provide a process for washing the mono nitroxylenes.

It is yet another object of the present invention to provide a process for recovering and reusing the reaction waste such as slightly alkaline and reusable water in the production of mono nitroxylene.

It is yet another object of the present invention to provide such a process for the production of mono nitroxylene with reduced amount of impurities and by-products.

SUMMARY OF THE INVENTION

Before the present system and its components are described, it is to be understood that this disclosure is not limited to the particular system and its arrangement as described, as there can be multiple possible embodiments which are not expressly illustrated in the present disclosure. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only and is not intended to limit the scope of the present application

This summary is provided to introduce concepts related to a system and a process for recovery of reusable water, and slightly alkaline water from slurry mixture of mono nitroxylene and a process for recovering and reusing the reaction waste from wastewater. This summary is not intended to identify essential features of the claimed subject matter, nor it is intended for use in determining or limiting the scope of the disclosed subject matter.

In accordance with an embodiment of the present subject matter, a system and process for washing of slurry mixture of mono nitroxylene, and a process for recovering and recycling of the alkaline water, ammonia, and reusable water are described herein. In one embodiment, a system for washing of slurry mixture of mono nitroxylene is disclosed. The system may comprise a first water washing reactor enabled for water washing of a slurry mixture of mono nitroxylene to obtain a first water-washed organic nitro-mass of mono nitroxylene. The system may further comprise a first separator unit enabled to separate the inorganic acidic mass from the first water-washed organic nitro mass and to transfer the first water-washed organic nitro mass to a second water washing reactor. The inorganic acidic mass may be transferred to a wastewater treatment unit. Further, the system may comprise the second water washing reactor enabled for a water washing of the first water-washed organic nitro mass in presence of ammonia (NH3) and water to obtain a second water-washed organic nitro-mass. The system may further comprise a second separator unit configured to separate an alkali effluent from the second water-washed organic nitro-mass and to transfer the second water washed-organic nitro-mass to a third water washing reactor. The alkaline mass may be transferred to the wastewater treatment unit. The third water washing reactor may be enabled for water washing of the second water-washed organic nitro-mass to obtain a third water- washed organic nitro-mass, and to further transfer the third water-washed organic nitro-mass to a third separator unit to separate slightly alkaline water and organic nitro mass. The third separator unit may be further configured to recycle slightly alkaline water from the third water-washed organic nitro mass to the first water washing reactor. The wastewater treatment unit may be configured for treating the inorganic acidic mass and the alkaline effluent mass to recover ammonium hydroxide/ ammonia, and reusable water.

In another embodiment, a process for washing of slurry mixture of mono nitroxylene is described herein. The process may comprise a step of water washing of slurry mixture of mono nitroxylene into a first water washing reactor to obtain a first water washed organic nitro-mass comprising mono nitroxylene. The process may further comprise a step of passing the first water washed organic nitro- mass comprising mono nitroxylene from the first water washing reactor to a second water washing reactor via a first separator unit to separate the inorganic acidic mass from the first water-washed organic nitro mass, wherein the inorganic acidic mass is transferred to a wastewater treatment unit. The process may further comprise a step of washing of the first water washed organic nitro-mass by water and ammonia solution into the second water washing reactor to obtain a second water-washed organic nitro-mass. Further, the process may comprise a step of feeding the second water washed organic nitro-mass to a second separator unit to separate an alkaline mass from the second water washed organic nitro-mass, wherein the alkaline mass obtained in the second separation unit is transferred to the wastewater treatment unit. The process may further comprise a step of transferring the second water-washed organic nitro-mass to a third water washing reactor enabled for water washing of the second water washed organic nitro mass to obtain a third water washed organic nitro- mass, wherein the third water washed organic nitro-mass is further transferred to a third separator unit for separation of the organic nitro-mass and a slightly alkaline water. The process may further comprise a step of recycling of the slightly alkaline water separated from the third water- washed organic nitro-mass by the third separator unit to the first water washing reactor. Furthermore, the process may comprise a step of recovering and recycling of the reusable water from the wastewater treatment unit.

In yet another embodiment, a process for recovering and recycling of the reusable water from the wastewater treatment unit described herein. The said process may comprise a step of receiving an alkaline mass from the alkaline mass storage to an alkaline mass receiving unit. The said process may comprise a step of alkalinization of the alkaline mass with 48% NaOH solution in an alkalinization reactor. The said process may comprise a step of ammonia stripping in an ammonia stripper unit. The said process may further comprise a step of acidification in an acidification reactor enabled to treat alkaline effluent with spent acid (H2SO4). The said process may further comprise a step of transferring an acidified alkali effluent obtained from the acidification reactor to a decanter unit. The said process may further comprise a step of neutralization in a neutralization chamber by reacting the acidified effluent with 48% NaOH and acid effluent. The said process may further comprise a step of first recovery of water by transferring a neutralized effluent to a multi-effect evaporator (MEE) unit. The said process may further comprise a step of second recovery of water from an agitated thin film dryer (ATFD) unit.

List of Abbreviations

3-NoX- 3-nitro-o-xylene

4-NoX- 4-nitro-o-xylene

ATFD- agitated thin film dryer

MVR- mechanical vapor re-compressor

ETP- effluent treatment plant

BRIEF DESCRIPTION OF DRAWINGS

The detailed description is described with reference to the accompanying Figures. In the Figures, the left-most digit(s) of a reference number identifies the Figure in which the reference number first appears. The same numbers are used throughout the drawings to refer like features and components. Figure 1 illustrates an implementation of a system (100) and components thereof for washing of slurry mixture of mono nitroxylene and recovery of slightly alkaline and reusable water, in accordance with an embodiment of the present subject matter.

Figure 2 illustrates an implementation of a wastewater treatment unit (107) for enabling wastewater treatment to recover and reuse the reaction waste, ammonium hydroxide, and fresh water.

Figure 3 illustrates a process (300) for washing of slurry mixture of mono nitroxylene and recovery of slightly alkaline and reusable water from slurry mixture of mono nitroxylene.

Figure 4 illustrates a process (400) for recovering and recycling of reusable water from the wastewater treatment unit (107).

DETAILED DESCRIPTION

Reference throughout the specification to “various embodiments,” “some embodiments,” “one embodiment,” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in various embodiments,” “in some embodiments,” “in one embodiment,” or “in an embodiment” in places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

The words "comprising," "having," "containing," and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items or meant to be limited to only the listed item or items.

It must also be noted that, the singular forms "a", "an", and "the" include plural references unless the context clearly dictates otherwise. Although any methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the exemplary methods are described. The disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms.

Various modifications to the embodiment may be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art may readily recognize that the present disclosure is not intended to be limited to the embodiments illustrated but is to be accorded the widest scope consistent with the principles and features described herein. The detailed description of the invention will be described hereinafter referring to accompanied drawings. The present invention relates to a system (100), a process (300), and a process (400) for the washing of mono nitroxylenes and also relates to an integrated method of treatment of wastewater by acidic, alkaline, and water washing in the production of nitroaromatic compounds, for example, nitroxylene, nitrobenzene, nitrotoluene or nitro xylenol, wherein the nitroaromatic compounds are produced in a reaction medium of sulfuric acid, nitric acid, and water. All commonly used Mono- and di- nitrated nitroaromatic compounds are produced by such methods. The said process (300), and process (400) integrates acid washing enabled to remove residual acid, alkaline washing enabled to remove nitrohydroxy aromatic compounds, and water washing enabled to remove any salt produced during alkaline washing of the crude nitroaromatic stream, with a wastewater treatment unit (107) to recover ammonium hydroxide/ ammonia, slightly alkaline water, and reusable water.

More specifically, wastewater comprising nitroaromatic compounds, free alkali and dissolved nitroaromatics is concentrated in a wastewater concentrator, whereby water and nitroaromatic products are recovered and recycled. When ammonia is used as the alkalinization source in nitroaromatic washing, the bulk of the free ammonia is recovered and reused in the process of washing of nitroaromatic compounds.

The mono nitroxylenes are prepared by nitration reaction between nitric acid and xylenes in presence of mixed acid. The reaction in the preparation of mono nitroxylenes produces slurry mixture which comprises of mono nitroxylenes, wastewater and impurities. This slurry mixture comprising mono nitroxylenes is further washed to remove wastewater comprising inorganic acids and alkalis. Further, the removed wastewater comprising inorganic acids and alkalis maybe treated to recover the reusable water.

The wastewater can then be introduced into the upstream alkaline washing step to recycle the recovered alkaline salt such as ammonium hydroxide (NH4(0H)) or liquid ammonia 10%. In one embodiment, a slightly alkaline water from the organic nitro-mass separation unit is obtained and a reusable fresh water, along with ammonia/NFUOH is separately recycled using effluent treatment plant i.e., wastewater treatment unit to achieve zero liquid discharge and reusable water.

The invention is depicted in Figures 1 and 2 in terms of the washing of mono nitroxylenes and recovery of alkaline water, liquid ammonia and water from the wastewater produced in the process of mono nitroxylene production. In one embodiment, the mono nitroxylene may be a 3-nitro-o-xylene (3-NOX) and a 4-nitro-o-xylene (4-NOX), 4-nitro-m-xylene, and 2-nitro-m-xylene. It will also be understood that the process will be applicable to other nitration reactions or other chemical reactions which are mass transfer limited. In one embodiment, referring to Figure 1, the system (100) may comprise a water washing reactor such as a first water washing reactor (101) (interchangeably referred to as ‘Rl’), a second water washing reactor (103) ((interchangeably referred to as ‘R2’), a third water washing reactor (108) ((interchangeably referred to as ‘R3’), a first separator unit (102) (interchangeably referred to as ‘Fl ’), a second separator unit (104) (interchangeably referred to as ‘F2’), and a third separator unit (110) (interchangeably referred to as ‘F3’). In one embodiment, the system may comprise more than three water washing reactors such as R4, R5. . Rn. In another embodiment, the system may comprise more than three separator units such as F4, F5. . Fn. The first water washing reactor (Rl) (101), the second water washing reactor (R2) (103), and the third water washing reactor (R3) (108) is further enabled to receive a fresh-water from fresh-water unit (109) for water washing of the organic nitro-mass and to separate inorganic acidic mass (interchangeably ‘acidic effluent’) and alkaline mass (interchangeably ‘alkaline effluent’) from an organic nitro-mass slurry of mono nitro-xylenes.

In an embodiment, referring to figure 1, the system (100) for washing of slurry mixture of mono nitroxylene is disclosed. The said system (100) may comprise a first water washing reactor (Rl) (101) enabled for water washing of a slurry mixture of mono nitroxylene to obtain a first water-washed organic nitro-mass comprising mono nitroxylene. The first water washing reactor (Rl) (101) is further enabled to receive a fresh-water from the fresh-water unit (109) for water washing of the organic nitro-mass.

The system (100) is configured for the initial step of water washing that uses water as the washing liquid and removes inorganic acidic mass. (The water washing step is sometimes referred to in the art as “acid washing,” because it removes acid or “water washing,” meaning the washing of the product stream with water for the purpose of removing mineral acids i.e., inorganic acids.)

The said first water washing reactor (Rl) (101) may be further enabled transfer the first water-washed organic nitro-mass to a first separator unit (Fl) (102). The said first separator unit (Fl) (102) may be configured to separate inorganic acidic mass from the first water-washed organic nitro mass and to transfer the first water-washed organic nitro to a second water washing reactor (R2) (103). In one embodiment, the inorganic acidic mass separated from the first separator unit (Fl) (102) may be transferred to a wastewater treatment unit (107).

The second water washing reactor (R2) (103) may be enabled for a washing of the first water-washed organic nitro mass in presence of ammonia (NFF) and water to obtain a second water-washed organic nitro-mass. The addition of ammonia enables proper separation of alkaline mass from the organic nitro mass without forming an emulsion or a combined layer of alkaline effluent and the organic nitro mass, and thereby enabling recovery of slightly alkaline water in the subsequent separator units. The said system (100) further may comprise a second separator unit (F2) (104) which is configured to separate the alkali effluent (alkaline mass) from the second water-washed organic nitro-mass and to transfer the second water washed organic nitro-mass to a third water washing reactor (R3) (108). In an embodiment, the alkaline mass may be transferred to the wastewater treatment unit (107).

The said third water washing reactor (R3) (108) may be further enabled for water washing of the second water-washed organic nitro-mass to obtain a third water-washed organic nitro-mass, and to further transfer the third water- washed organic nitro-mass to a third separator unit (F3) (110). The third separator unit (F3) (110) may be enabled for separation of slightly alkaline water from the third water-washed organic nitro-mass. The third separator unit (110) (F3) may be further configured to recycle the slightly alkaline water to the first water washing reactor (Rl) (101).

In one embodiment, the system (100) may further comprise the wastewater treatment unit (107) configured for treating the inorganic acidic mass and the alkaline mass to recover ammonium hydroxide/ ammonia, and reusable water.

Following the water washing step, organic by-products are extracted from the nitrated organic product by washing it with an aqueous alkaline solution. The aqueous alkaline solution of the base such as typically, but is not limited to, sodium hydroxide, sodium carbonate (soda ash) or ammonia may be used for the purpose of extracting organic by-products from the nitrated organic product. Through this washing step, referred to as “alkaline washing,” the acidic organic by-products, which are dissolved in the organic product phase, are neutralized by the base, and converted to organic salts, which readily transfer into the aqueous washing solution. To achieve industry-accepted product specifications for the acidic organic by-products, more than one stage of alkaline washing is typically used.

The above-described washing steps are carried out by mixing the two immiscible fluids together to transfer the target compounds from one phase to the other, followed by settling of the mixture back into two phases to allow separation and recovery of the two fluids, washing steps can be a single or multiple units, where multiple units can be arranged in crossflow or more commonly a counter-current flow pattern, is typically practiced.

The separated organic nitro-mass from the third separator unit (F3) (110) may then transferred to distillation unit (not shown) for recovery and separation mono nitro-xylenes such as 3-NoX and 4- NoX.

The alkaline water is a slightly alkaline water recovered from multiple washings of organic nitro mass from the first separator (Fl) unit, the second separator (F2) unit, and the third separator (F3) unit. This slightly alkaline water is also reused in acid washing, and alkaline washing treatment in first water washing reactor (Rl), the second water washing reactor (R2), and the third water washing reactor (R3) enabling use of an added fresh-water in water washing to a maximum extent.

In an embodiment, the second separator unit (104) may be further configured to pass the second water washed organic nitro mass to a wastewater treatment unit (107), wherein the wastewater treatment unit (107) is configured to recover ammonium hydroxide/ ammonia, and reusable water. The wastewater treatment unit (107) may comprise a storage unit (105) further comprising alkaline mass storage compartment (105B) and inorganic acid storage compartment (105A).

In one embodiment, referring to Figure 2, the wastewater treatment unit (107) may further comprise an alkalinization reactor (201), an ammonia stripper unit (202), an acidification reactor (203), a decanter (204), a neutralization chamber (205), a multi effect evaporator (MEE) (206), and an agitated thin film dryer (ATFD) (208) enabled to recover the reusable water.

It should be noted herein that, the first separator unit (Fl) (102) and the second separator unit (F2) (104), may be enabled as separators to separate, and transfer the by-products such as alkaline effluent, and fresh water to the waste-water treatment unit (107) for the recovery and recycle of fresh water, and ammonia in the production of mono nitroxylene. Further, the third separator unit (F3) (110) may be configured for separation of slightly alkaline water from the third water washed organic nitro-mass and to recycle the slightly alkaline mass to the first water washing reactor (Rl) for reuse of slightly alkaline water in the system for washing of slurry mixture of mono nitroxylene.

Referring to Figure 1 and Figure 2, the wastewater treatment unit (107) further comprises of one or more inorganic acids storage compartment (105 A) configured to receive inorganic acidic mass separated from the first separator unit (102), to further neutralize the inorganic acids.

Further, the wastewater treatment unit (107) comprises an alkaline mass storage compartment (105B), configured to transfer the alkaline mass to the alkaline mass (hereinafter maybe alternatively referred to as ‘alkali effluent’) receiving unit (106), which is connected to an Effluent treatment plant (ETP). Further, the wastewater treatment unit (107) comprises an alkalinization reactor (201) enabled for treating the alkaline mass (alkaline effluent) with 48% NaOH solution to further increase the pH and alkalinize the alkali effluent. Further, the wastewater treatment unit (107) comprises an ammonia stripper unit (202) enabled to receive an alkalinized alkali effluent and to remove ammonium hydroxide (10%) solution, and to transfer an ammonia stripped alkali effluent to an acidification reactor (203). The acidification reactor (203) is enabled to treat alkaline effluent with spent acid (H2SO4), by poly dosing and alum charging mechanism for acidification of the ammonia stripped alkali effluent in a batch mode. The poly dosing and alum charging of the spent acid enables effective acidification of the alkali effluent. Further, an acidified alkali effluent of the acidification reactor (203) is then transferred to a decanter (204) which is enabled to remove harmful cresol groups such as nitro-cresols from the acidified effluent. The decanter (204) is configured to reduce the formation of impurity such as nitro-cresols and transfer the acidified effluent to a neutralization chamber (205). In one embodiment, removal of nitro cresols before neutralization of the acidified effluent prohibits formation of eruptive toluene and nitro cresols and thereby aid safe treatment of effluent and effective recovery of fresh reusable water without any flammable, reactive, or eruptive components.

In one embodiment, the neutralization chamber (205) is configured for reacting the acidified effluent with 48% NaOH. In one embodiment, the neutralization chamber (205) is further configured to treat the acidified effluent, and to receive the acid effluent from the decanter (204) and/or from the inorganic acid storage compartment (105 A).

Further, a neutralized effluent obtained from the neutralization chamber (205) is transferred to a multi-effect evaporator (MEE) (206). The multi-effect evaporator (MEE) (206) is configured for evaporation of water and to further transfer condensate water for repolishing, wherein condensate water is repolished by at least one of mechanical vapor re-compressor (MVR) (207) or reverse osmosis unit (RO) (not shown). The MEE (206) is configured to concentrate the effluent and to transfer an evaporated water content to the mechanical vapor re-compressor (MVR) (207) or to the reverse osmosis (RO) unit to recompress and transfer a water condensate obtained from multi-effect evaporator (MEE). In one embodiment, the mechanical vapor re-compressor (MVR) (207) and the reverse osmosis unit are used as an alternative for recollection for reusable water. In one embodiment, the mechanical vapor re-compressor (MVR) (207) and the reverse osmosis (RO) unit is configured for recollecting a water condensate.

Again, referring to Figure 2, a concentrated effluent obtained from the multi-effect evaporator (MEE) (206) is then transferred to an agitated thin film dryer (ATFD) (208) for maximum recovery of water. In one embodiment, a mechanical vapor re-compressor (MVR) (207) is also positioned after the ATFD (208) to recompress and transfer a water condensate obtained from agitated thin film dryer (ATFD) (208) to a reverse osmosis (RO) unit. In one embodiment, a mechanical vapor re-compressor (MVR) (207) and a reverse osmosis unit are used as an alternative for recollection for reusable water from agitated thin film dryer (ATFD) (208). In one embodiment, the mechanical vapor re-compressor (MVR) (207) and reverse osmosis (RO) unit is configured for recollecting a water condensate.

In one embodiment, the agitated thin film dryer (ATFD) (208) is enabled to recover up to 80%, and up to specifically 40% of reusable water from MEE concentrate. The reusable water recovered from the multi-effect evaporator (MEE) (206), and the agitated thin film dryer (ATFD) (208) is reusable as a fresh water in multiple reactions. In one embodiment, the fresh reusable water obtained from the MEE (206) and the ATFD (208) may be transferred to the first water washing reactor (Rl) (101) of the system (100).

By, referring to figure 2 and 3, a process (300) for washing of slurry mixture of mono nitroxylene for recovery of reusable water, from slurry mixture of mono nitroxylene is disclosed. The said process (300) may comprise of various steps.

The said process (300) may comprise a step of charging the water from the fresh-water unit into a first water washing reactor (Rl) (101). The said process may comprise a step of water washing (301) of a slurry mixture of organic mono nitroxylene into a first water washing reactor (Rl) (101) to obtain a first water washed organic nitro-mass comprising mono nitroxylene. In one embodiment the said one or more inorganic acid includes but not limited to sulphuric acid and spent acid or a combination thereof.

The said process (300) further may comprise a step of passing (302) the first water washed organic nitro-mass comprising mono nitroxylene from the first water washing reactor (Rl) (101) to a second water washing reactor (103) via the first separator unit (Fl) (102) to separate the inorganic acidic mass from the first water-washed organic nitro mass. In one embodiment, the inorganic acidic mass is transferred to a wastewater treatment unit (107).

The said process (300) further may comprise a parallel step of charging water from a fresh-water unit (109) and ammonia solution in the second water washing reactor (103). The process (300) may further comprise a step of washing (303) of the first water washed organic nitro-mass by water and ammonia solution into the second water washing reactor (R2) (103) to obtain a second water-washed organic nitro-mass.

In one embodiment, the concentration of ammonia solution added to the second water washing reactor (103) maybe between 5-15%, preferably between 8-12%, more preferably 10%. The addition of ammonia solution enables reduction of emulsion formation of organic and aqueous layer and attributes in formation of separate phase layers of organic and aqueous layer.

The said process (300) further may comprise a step of feeding (304) the second water washed organic nitro-mass and predetermined amount of fresh water to a second separator unit (F2) (104) to separate the alkaline mass from the second water washed organic nitro-mass. In one embodiment, the alkaline mass obtained in the second separator unit (F2) (104) is transferred to the wastewater treatment unit (107).

The process (300) further may comprise a step of transferring (305) the organic nitro-mass to a third water washing reactor (R3) (108) enabled for water washing of the second water-washed organic nitro-mass to obtain a third water-washed organic nitro-mass, wherein the said third water-washed organic nitro-mass is further transferred to a third separator unit (F3)(l 10) for separation of slightly alkaline water from the third water-washed organic nitro-mass.

The process (300) may further comprise a step of recycling (306) of the slightly alkaline water separated from the third water- washed organic nitro-mass by the third separator unit (F3) (110) to the first water washing reactor (Rl) (101) for recycle and reuse.

In one embodiment, the process (300) may comprise a step of recovering and recycling (307) of the reusable water from the wastewater treatment unit (107). The step of recycling (306) of a slightly alkaline water separated from the organic nitro-mass in the third separator unit (F3) (110) to the first water washing reactor (Rl) (101), transferring the inorganic acidic mass obtained in the first separator unit (Fl) (102) into the wastewater treatment unit (107), and transferring the alkaline mass obtained in the second separator unit (F2) (104) into the wastewater treatment unit (107) are carried out simultaneously.

In one embodiment, one or more recovered by-products from the wastewater treatment unit (107) may include but not limited to aqueous ammonia, and reusable water as a condensate from at least one of MEE, MVR, RO, and ATFD.

Now, referring to Figure 3 and 4, a process (400) elaborating a steps of recovering and recycling (308) of reusable water from the wastewater treatment unit (107) are disclosed.

The process (400) may comprise a step of receiving (401) an alkaline mass from the alkaline mass storage (105B) to an alkaline mass receiving unit (106). The process (400) may further comprise a step of alkalinization (402) of the alkaline mass with 48% NaOH solution in an alkalinization reactor (201) to increase the pH and alkalinity of the alkaline effluent mass.

The process (400) may further comprise a step of ammonia stripping (403) in an ammonia stripper unit (202), and thereby receiving an NaOH alkalinized alkali effluent and to remove ammonium hydroxide (10%) solution, and to transfer an ammonia stripped alkali effluent to an acidification reactor (203).

The process (400) may comprise a step of acidification (404) in an acidification reactor (203) enabled to treat alkaline effluent with spent acid (H2SO4). In one embodiment, the step of acidification (404) may be carried out by poly dosing and alum charging mechanism. The poly dosing mechanism enables elimination of liquid solids by settling the solids within wastewater treatment can be achieved through the use of liquid or powdered polymers.

The process (400) may comprise a step of transferring (405) an acidified alkali effluent obtained from an acidification reactor (203) to a decanter (204) unit to remove harmful cresol groups from the acidified effluent. In one embodiment the removal of cresols is a batch wise process and may be implemented to remove all organic acid settled impurities (like nitro cresol) from the wastewater stream with the help of a decanter (204).

The process (400) may comprise a step of neutralization (406) in a neutralization chamber (205) by reacting the acidified effluent with 48% NaOH and acid effluent.

Further, the process (400) may comprise a step of first recovery of water (407) by transferring a neutralized effluent to a multi-effect evaporator (MEE) (206), and to concentrate the neutralized effluent. The step of first recovery of water (407) may further comprise a sub-step of transferring (407-1) an evaporated water condensate (content) to a mechanical vapor re-compressor (MVR) (207) to recompress and transfer a water condensate obtained from multi-effect evaporator (MEE) to a reverse osmosis (RO) unit.

The process (400) may further comprise a step of second recovery of water (408) from an agitated thin film dryer (ATFD) (208). The process (400), wherein the step of second recovery of water (408) comprises a sub-step of transferring (408-1) a concentrated water obtained from (MEE) to the agitated thin film dryer (ATFD), and then to a mechanical vapor re-compressor (MVR) (207) or a reverse osmosis (RO) unit.

The process (400) may further comprise a step of second recovery of water (408) from an agitated thin film dryer (ATFD) (208) and thereby enabling maximum recovery of reusable water up to 80%. The process (400) may further comprise an optional step of transferring a reusable water obtained from MEE (206) and ATFD (208) to the first water washing reactor (Rl) (101) of the system (100) and thereby enabling maximal utility of water in the washing.

In another example, the condensate from MVR (207) and ATFD (208) be pooled through a reverse osmosis (RO) and called recycled/reusable water. In one embodiment, by implementing the wastewater treatment unit, about 80% reusable water may be recovered and recycled in the water washing system (100) and the process (300).

The instant subject matter is further described by the following examples:

Experimental Details:

Example 1:

A system and the process to remove nitro cresols and recover fresh reusable water from the crude slurry of mono nitro xylene is provided in accordance with the embodiment of the present invention. The process comprised steps of first water washing of slurry mixture of mono nitroxylene into a first water washing reactor (Rl) to obtain a first water washed organic nitro-mass comprising mono nitroxylene. The first water washed organic nitro-mass comprising mono nitroxylene was passed to a second water washing reactor (R2) via a first separator unit (Fl) to separate the inorganic acids from the first water-washed organic nitro mass, wherein the inorganic acids are transferred to a wastewater treatment unit.

Second water washing of the first water washed organic nitro-mass was then carried out by water and ammonia solution into the second water washing reactor (R2) and thereby obtaining a second water-washed organic nitro-mass. The second water washed organic nitro-mass comprising mono nitroxylene was then fed to a second separator unit (F2) to separate an alkaline mass from the second water washed organic nitro-mass comprising mono nitroxylene, wherein the alkaline mass obtained in the second separation unit (F2) is transferred to the wastewater treatment unit.

In one embodiment, the total water volume recovered after acid wash in Fl and after alkaline wash in F2 is transferred to the third separator unit (F3) for recovery of slightly alkaline water and separation of organic nitro mass of mono-nitro xylenes. The organic nitro mass of mono-nitro xylenes is separately transferred to distillation process. The sightly alkaline water in the third separator unit (F3) is then transferred to first water washing reactor (Rl) for reuse.

Example 2: (ammonia washing of the acid washed nitro mass)

In one embodiment, the total flow of washing water and feeding rate for nitro mass comprising mono nitroxylene while using ammonia in second separator unit (F2) for acid washing is provided. Flow rate for the nitro mass comprising mono nitroxylene ranges between 610 Kg/hr- 680 Kg/hr. Further, 2%-5% solution of Ammonia is used and the formation of reduction in emulsion is evaluated by visual inspection. Further, about 2% ammonia solution having slight alkalinity remains in the final nitro mass. The alkaline effluent mass from F2 is transferred to wastewater treatment unit comprising alkaline effluent mass storage.

Example 3 (recovery of reusable water and ammonia from wastewater)

In one embodiment, again referring to figure 1 and 2, the alkaline mass receiving unit may be equipped with one inlet to receive the alkaline effluent (alkaline Effluent) water from storage and second separator unit (F2) and one outlet to discharge the effluent to the alkalinization reactor, where the effluent may be further treated with 48% NaOH solution to make the effluent strongly alkaline by increasing pH. The alkaline mass separated stream from second separator unit (F2) comprises of nitro cresols which should be removed by means of treatment. Alkaline water is having pH in the range of 7.5-8. This alkaline water pH is maintained at higher side by adding sodium hydroxide (NaOH) solution in the wastewater treatment unit. The alkalinity was increased by increasing pH, that should be in the range of 9-10. The stripping of the alkaline water was done to recover the ammonia which is of the strength of 5-10% in an ammonia stripping unit, wherein the recovered ammonia/NH4OH is recycled in process. The remaining part (wastewater) comprising the salts of organic acids, may be further subjected to an acidification reactor enabled for mixing of the spent acid to the wastewater. Again, the pH 3-5 is adjusted by adding spent acid of predefined amount and this aqueous mass is fed to decanter to remove eruptive components such as nitro-cresols. The spent acid treated alkaline effluent (hereinafter may be interchangeably referred to as “alkaline water”) maybe passed into the decanter enabled to reduce and remove the formation of impurity such as cresol. The remaining portion of spent acid alkaline effluent maybe treated with 48% NaOH and acid effluent in the neutralization chamber to increase the pH i.e., alkalinity of the acid effluent to increase the total suspended solid (TSS) settling.

The neutralized effluent is then transferred to the multi-effect evaporator (MEE) connected to a mechanical vapor re-compressor (MVR)/reverse osmosis (RO) unit to condense and recollect a reusable water up to 80%. Further the leftover concentrate separated from the MEE (206) condensate maybe fed to an agitated thin film dryer (ATFD) (208) enabled for separation of inorganic salts, wherein the rest of the water content is collected as ATFD condensate by separating inorganic salts.

The mechanical vapor re-compressor (MVR), wherein most of the water content maybe recollected as MVR condensate (which is optionally recycled in reverse osmosis unit (RO). The reverse osmosis (RO) and MVR can also be implemented interchangeably or subsequently. Example 4: (Reuse of slightly alkaline water obtained from Example 1 and 3)

The fresh water is provided to the first water washing reactor (Rl) for separation of inorganic acids with a flow rate of 2050 Kg/hr. The recycled water obtained from wastewater treatment unit and a slightly alkaline water obtained from third separator unit (F3) is passed to the first water washing reactor (Rl) with a flow rate of 725 Kg/hr. The total volume of the water recovered after acid wash and alkaline wash is 1350 Kg/hr. The total volume of water recovered and recycled to first water washing reactor (Rl) (101) after acid wash is 700 Kg/hr.

The system (100), process (300), and process (400) in accordance with the embodiments of the present disclosure has many advantages such as but not limited to:

- the reduced water consumption and reduced chemical consumption in nitroaromatic washing

- the recovery of ammonia is possible in the alkaline washing and indicating the nitro aromatic extraction efficiency is improved recovery and reuse of slightly alkaline water

It is also believed that in the new procedure lighter environmental requirements in relation to a combustion fulfils and improved public acceptance and regulatory compliance

- the elimination of aqueous sewerage compared to known treatment methods, considered so far were reduced

The process concentrates acidic and alkaline wash water to reclamation of chemicals and water. The new integrated process leads to reduced chemicals and water consumption compared to existing procedures.

Although implementations for system for washing of slurry mixture of mono nitroxylene, comprising of have been described in language specific to structural features and/or process, it is to be understood that the appended claims are not necessarily limited to the specific features or process described. Rather, the specific features and process are disclosed as examples of implementations of system for washing of slurry mixture of mono nitroxylene.