CN203256080U - Phosphorus-containing wastewater processing device - Google Patents
Phosphorus-containing wastewater processing device Download PDFInfo
- Publication number
- CN203256080U CN203256080U CN 201320245501 CN201320245501U CN203256080U CN 203256080 U CN203256080 U CN 203256080U CN 201320245501 CN201320245501 CN 201320245501 CN 201320245501 U CN201320245501 U CN 201320245501U CN 203256080 U CN203256080 U CN 203256080U
- Authority
- CN
- China
- Prior art keywords
- rotary kiln
- phosphorus
- containing wastewater
- cylinder
- glyphosate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Images
Abstract
The utility model provides a phosphorus-containing wastewater processing device for solving the technical problems in the existing phosphorus-containing wastewater processing method that the recovery efficiency of recycled materials is low, the secondary economic benefit is low, the process is complex, and the environmental protection effect is not ideal. The phosphorus-containing wastewater processing device is characterized by being used for carrying out the following steps of: adding acidic materials into glyphosate mother solution, evaporating and concentrating, cooling to the room temperature, and filtering to obtain high-concentration phosphorus-containing mother solution; obtaining solid materials after drying and dehydrating the high-concentration phosphorus-containing mother solution, burning the solid materials in a rotary kiln, and finally carrying out recrystallization to obtain phosphate. The phosphorus-containing wastewater processing device can be used for processing the phosphorus-containing wastewater.
Description
Technical field
The utility model relates to a kind for the treatment of unit of liquid, particularly relates to a kind for the treatment of unit of phosphorus-containing wastewater.
Background technology
Glyphosate is as the steriland herbicide of a kind of efficient, wide spectrum, low toxicity, and range of application is more and more extensive, has become at present the in the world weedicide of consumption maximum.Present Domestic prepares glyphosate and adopts glycine method and dialkyl phosphite method more.
According to the method for comprehensive utilization of recommending in " the environmental protection technology catalogue of national encourage growth " (2009 year), the glyphosate mother solution that producing glyphosate by using glycine is obtained mixes production cement slurry grinding aid and sells as byproduct with diatomite, cinder, auxiliary agent etc.Along with the continuous progress of technology, manufacture of cement producer progressively uses aqua instead and substitutes solid cement grinding aids, and the cement slurry grinding aid of glyphosate mother solution processing no longer has competitive edge, and eliminates gradually.In order to ensure the sustainability of glyphosate production, must the route that glyphosate mother solution is processed the cement slurry grinding aid be changed.
Notification number is in the Chinese invention patent application of CN101190926, a kind for the treatment of process of glyphosate mother solution is proposed, it mainly is to pass into ammonia to reclaim triethylamine in glyphosate mother solution, the ammonium glyphosate that ammonium chloride obtains concentrating is removed in the redistillation dehydration, but the concentrated ammonium glyphosate salts solution that obtains is difficult for recycling, the triethylamine rate of recovery is also lower, and the secondary benefit is low.
Notification number is to disclose a kind of method that reclaims the triethylamine in glyphosate mother liquid that the dialkyl phosphite method produces in the Chinese invention patent of CN101307002, the method has solved the low problem of the triethylamine rate of recovery, but this invented technology is loaded down with trivial details, also to use organic solvent in the treating processes, processing cost is higher, and the feature of environmental protection is bad.
Notification number is the treatment process that discloses the glyphosate mother solution that a kind of dialkyl phosphite method produces in the Chinese invention patent application of CN101985426A, and the method triethylamine rate of recovery is more than 98.5%.Although the triethylamine rate of recovery is higher, the waste water COD of discharging is less than 500mg/L, and TP is less than 1.0mg/L, and ammonia nitrogen is less than 15mg/L, and environmental benefit is outstanding not enough; Simultaneously, this invention is not made efforts to reducing the processing cost aspect, except triethylamine without other regenerants, cause processing cost higher.
The treatment process of above-mentioned several glyphosate mother solutions has shortcoming separately, seek a kind of can be high yield reclaim Recyclable in the mother liquor, can reduce again waste water and discharge, alleviate environmental protection pressure, the treatment process that can also produce higher secondary benefit and the simple glyphosate mother solution of technique simultaneously is the problem that the industry is badly in need of solution.
Along with the progress of science and technology, and cross is more and more between every profession and trade, and rotary kiln is broken away from the constraint of restraint of trade gradually, is applied in numerous industries.For example, in the treating processes of glyphosate mother solution, just can come the solid materials that obtains in the treating processes is burned with rotary kiln.Yet the problem of rotary kiln formation kiln circle has been brought very adverse influence to the burning of solid materials.
At present, the method for known removing rotary kiln circle is: when the kiln circle forms, reduce filler or stop material, moved forward gas jet several hours, improve kiln circle temperature; Then mobile gas jet several hours backward reduces kiln circle temperature; Repeatedly mobile gas jet several times, make the kiln circle be subject to colding and heat succeed each other significantly the effect and the cracking be caving.
Mainly there is following problem in the Fang of stating Fa Cheongju except the kiln circle Shang adopting:
One, material reducing or stop material and can cause reduce or stop production, the abrasion loss of fuel, electric power consumption and equipment can not reduce simultaneously, has so just caused very large financial loss.
Two, the significantly effect of colding and heat succeed each other can make the kiln lining of rotary kiln cause Local Cracking and kiln skin releasing, and the life-span of rotary kiln is reduced greatly.
Summary of the invention
The regenerant organic efficiency that exists in the existing phosphorus-contained wastewater treating method is low, the secondary economic benefit is low in order to solve, complex process and the undesirable technical problem of environment protecting, and the utility model provides that a kind of regenerant organic efficiency is high, secondary is good in economic efficiency, technique is simple and has the treatment unit of the phosphorus-containing wastewater of reasonable environment protecting.
Concrete process method step is as follows:
(1) add acidic substance in glyphosate preparation mother liquor, transfer pH to 5～13, after multiple-effect evaporation concentrated, is cooled to room temperature, filter, get filter cake, organism is removed in washing, namely gets inorganic salt, and filtrate is the high-density phosphorus mother liquor;
(2) the high-density phosphorus mother liquor of step (1) gained, the dehydration of drying equipment makes solid materials;
(3) step (2) gained solid materials, is purified through recrystallization 600～800 ℃ of lower burnings through rotary kiln, and oven dry namely gets phosphate product.
Glyphosate preparation mother liquor when adopting preparing glyphosate by glycin method, the glyphosphonic acid aqueous mother liquor of preparing behind the glyphosate crystallization or reclaimed alkaline mother liquor after the triethylamine.
Preferably, acidic substance are the pmida98 mother liquor.
Preferably, the pmida98 mother liquor is when adopting the standby glyphosate of iminodiethanoic acid legal system, the acid mother liquid of synthetic pmida98 gained, and the pH scope is 0～1.
Preferably, in the step (1), multiple-effect evaporation is concentrated into 20～60% of former weight.
Preferably, in the step (2), drying temperature is 200～400 ℃.
Preferably, in the step (3), also comprise the fume afterheat and the solid that reclaim in burning.
Preferably, in the step (1), according to the difference of product phosphoric acid salt kind, different pH are arrived in neutralization respectively:
Orthophosphoric acid salt: pH=8.5-13.
Pyrophosphate salt: pH=7.6-8.5.
Poly-phosphate: pH=5-7.6.
Adopting aforesaid method to process glyphosate preparation mother liquor has the following advantages:
One, technique is simple, efficient, the chlorion transformation efficiency is more than 98%, step (1) gained washes is after biochemical system is processed, the waste water COD of discharging is less than 20mg/L, and TP is less than 0.5mg/L, and ammonia nitrogen is less than 9mg/L, COD, TP and ammonia nitrogen reach national grade one discharge standard fully, substantially realized the zero release of waste water, efficiently solved the processing problem of phosphorus-containing wastewater, environment protecting is outstanding;
Two, the gained phosphate content is more than 97%, and the phosphorus containg substances transformation efficiency is more than 98%;
Three, the gained Industrial Salt can be used for the industries such as chemical industry, papermaking, building, and the pyrophosphate salt of gained can be used for chemical industry, plating, wool spinning, paper industry, obtains reasonable economic benefit.
In the treatment process of above-mentioned phosphorus-containing wastewater, use rotary kiln that the solid materials of step (2) gained is burned in the step (3).This rotary kiln is provided with combustion unit and cylinder of rotary kiln, and combustion unit is set on the cylinder of rotary kiln, and the outer wall of cylinder of rotary kiln is provided with percussion vibration device; The inwall of cylinder of rotary kiln is provided with movable broken circle device, and movable broken circle device one end is fixedly connected with the inwall of cylinder of rotary kiln, and the other end contacts with the cylinder of rotary kiln inwall.
Preferably, be provided with fixed block between the outer wall of percussion vibration device and cylinder of rotary kiln.
Preferably, percussion vibration device comprises striking rod, hammer and striking rod stationary installation.
The used rotary kiln of the utility model can material reducing when removing its kiln circle or is stopped material, thereby has avoided material reducing or stop expecting and the various financial losses brought; In addition, the utility model does not adopt and colds and heat succeed each other to remove the rotary kiln circle, can not impact kiln lining, and then prolong the work-ing life of rotary kiln.
Description of drawings
Fig. 1 is the one-piece construction synoptic diagram of the utility model rotary kiln;
Fig. 2 is the structural representation of the percussion vibration device on the utility model rotary kiln.
Nomenclature among the figure:
1. cylinder of rotary kiln; 2. combustion unit; 3. gas jet; 4. percussion vibration device; 5. striking rod; 6. hammer; 7. striking rod stationary installation; 8 bolts; 9. fixed block; 10. movable breaking enclosed device.
Embodiment
Be described in detail below by the treatment process of specific embodiment to phosphorus-containing wastewater.
To containing chlorion 7.8%, adding pH is 0 pmida98 mother liquor in the glyphosate mother solution of total phosphorus 2.88% (1000g), make mother liquor pH regulator to 7.8, multiple-effect evaporation is concentrated into 20% of former weight, filters, and filter cake is removed organism through washing, namely get sodium-chlor 130.2g, the chlorion transformation efficiency is 98.2%, and waste water is COD18mg/L after biochemical treatment, TP0.4mg/L, ammonia nitrogen 8mg/L, filtrate after 200 ℃ of dryings, in rotary kiln of the present utility model through 600 ℃ of burnings, recrystallization, dry to get trisodium phosphate 124.1g, content 97.6%, phosphorus containg substances transformation efficiency 98.0% reclaims fume afterheat and solid in burning simultaneously.
To containing chlorion 7.8%, adding pH is 0.5 pmida98 mother liquor in the glyphosate mother solution of total phosphorus 2.88% (1000g), after making mother liquor pH regulator to 8, multiple-effect evaporation is concentrated into 30% of former weight, filters, and filter cake is removed organism through washing, namely get sodium-chlor 130.8g, the chlorion transformation efficiency is 98.6%, and waste water is COD17mg/L after biochemical treatment, TP0.3mg/L, ammonia nitrogen 7mg/L, filtrate after 240 ℃ of dryings, in rotary kiln of the present utility model through 700 ℃ of burnings, recrystallization, dry to get trisodium phosphate 124.5g, content 97.8%, phosphorus containg substances transformation efficiency 98.5% reclaims fume afterheat and solid in burning simultaneously.
To containing chlorion 7.8%, adding pH is 1 pmida98 mother liquor in the glyphosate mother solution of total phosphorus 2.88% (1000g), after making mother liquor pH regulator to 9, multiple-effect evaporation is concentrated into 40% of former weight, filters, and filter cake is removed organism through washing, namely get sodium-chlor 130.6g, the chlorion transformation efficiency is 98.4%, and waste water is COD12mg/L after biochemical treatment, TP0.3mg/L, ammonia nitrogen 6mg/L, filtrate after 300 ℃ of dryings, in rotary kiln of the present utility model through 800 ℃ of burnings, recrystallization, dry to get sodium orthophosphate 152.5g, content 98%, phosphorus containg substances transformation efficiency 98.1% reclaims fume afterheat and solid in burning simultaneously.
Embodiment 4
To containing chlorion 7.8%, adding pH is 1 pmida98 mother liquor in the glyphosate mother solution of total phosphorus 2.88% (1000g), after making mother liquor pH regulator to 10, multiple-effect evaporation is concentrated into 20% of former weight, filter, filter cake is removed organism through washing, namely gets sodium-chlor 131.4g, and the chlorion transformation efficiency is 99.1%, waste water is COD10mg/L after biochemical treatment, TP0.1mg/L, ammonia nitrogen 5mg/L, filtrate is after 260 ℃ of dryings, in rotary kiln of the present utility model through 700 ℃ of burnings, recrystallization is dried to get sodium orthophosphate 152.8g, content 98.4%., phosphorus containg substances transformation efficiency 98.7% reclaims fume afterheat and solid in burning simultaneously.
Embodiment 5
To containing chlorion 7.8%, adding pH is 1 pmida98 mother liquor in the glyphosate mother solution of total phosphorus 2.88% (1000g), after making mother liquor pH regulator to 7.1, multiple-effect evaporation is concentrated into 25% of former weight, filters, and filter cake is removed a small amount of organism through washing, namely get sodium-chlor 131.1g, the chlorion transformation efficiency is 98.9%, and waste water is COD12mg/L after biochemical treatment, TP0.4mg/L, ammonia nitrogen 8mg/L, filtrate after 260 ℃ of dryings, in rotary kiln of the present utility model through 750 ℃ of burnings, recrystallization, dry to get sodium polyphosphate 95g, content 98.1%, phosphorus containg substances transformation efficiency 98.4% reclaims fume afterheat and solid in burning simultaneously.
To containing chlorion 7.8%, adding pH is 1 pmida98 mother liquor in the glyphosate mother solution of total phosphorus 2.88% (1000g), after making mother liquor pH regulator to 5.8, multiple-effect evaporation is concentrated into 35% of former weight, filters, and filter cake is removed a small amount of organism through washing, namely get sodium-chlor 131g, the chlorion transformation efficiency is 98.8%, and waste water is COD15mg/L after biochemical treatment, TP0.3mg/L, ammonia nitrogen 7mg/L, filtrate after 260 ℃ of dryings, in rotary kiln of the present utility model through 650 ℃ of burnings, recrystallization, dry to get sodium polyphosphate 94.8g, content 98.0%, phosphorus containg substances transformation efficiency 98.1% reclaims fume afterheat and solid in burning simultaneously.
To containing chlorion 7.8%, adding pH is 1 pmida98 mother liquor in the glyphosate mother solution of total phosphorus 2.88% (1000g), after making mother liquor pH regulator to 8.2, multiple-effect evaporation is concentrated into 40% of former weight, filters, and filter cake is removed a small amount of organism through washing, namely get sodium-chlor 131.2g, the chlorion transformation efficiency is 99%, and waste water is COD15mg/L after biochemical treatment, TP0.4mg/L, ammonia nitrogen 8mg/L, filtrate after 260 ℃ of dryings, in rotary kiln of the present utility model through 700 ℃ of burnings, recrystallization, dry to get trisodium phosphate 124g, content 98.5%, phosphorus containg substances transformation efficiency 98.8% reclaims fume afterheat and solid in burning simultaneously.
The below is described in detail employed rotary kiln in the process method step (3) of phosphorus-containing wastewater.
As shown in Figure 1, rotary kiln mainly comprises cylinder of rotary kiln 1 and combustion unit 2, and combustion unit 2 is set on the cylinder of rotary kiln 1, and cylinder of rotary kiln 1 passes combustion unit 2 and stretches out from its two ends.Be provided with some gas jets 3 in the combustion unit 2, cylinder of rotary kiln 1 ceaselessly rotates, and gas jet 3 is calcined cylinder of rotary kiln 1 uniformly.
Outer wall at cylinder of rotary kiln 1 is provided with 6 percussion vibration devices 4.As shown in Figure 2, percussion vibration device 4 comprises striking rod 5, hammer 6 and striking rod stationary installation 7.Hammer 6 is located at an end of striking rod 5, and the other end of striking rod 5 is provided with striking rod stationary installation 7; Bolt 8 and nut (not shown) couple together striking rod 5 and striking rod stationary installation 7, so that striking rod 5 can rotate as the center of circle take striking rod stationary installation 7.Percussion vibration device 4 also can arrange its quantity as required.
Striking rod stationary installation 7 is the U font, and striking rod 5 can be take striking rod stationary installation 7 rotation of 90 degree to the maximum as the center of circle.When cylinder of rotary kiln 1 rotated, the hammer 6 of percussion vibration device 4 will be knocked cylinder of rotary kiln 1 automatically along with the rotation of cylinder of rotary kiln 1, so that the kiln circle of rotary kiln inwall becomes flexible or is caving.
Striking rod stationary installation 7 also can be two opposed fixed plates, and striking rod 5 and hammer 6 can both be beaten on the both sides of striking rod stationary installation 7 like this.When cylinder of rotary kiln 1 counter-rotating, striking rod 5 and hammer 6 can oppositely be beaten.
In order to protect cylinder of rotary kiln 1 not damaged, between the outer wall of percussion vibration device 4 and cylinder of rotary kiln 1, be provided with fixed block 9.The fixed block 9 that connects striking rod stationary installation 7 and cylinder of rotary kiln 1 can be independent individuality, also can be integral with striking rod stationary installation 7.
In addition, also be provided with movable broken circle device 10 in the cylinder of rotary kiln 1.One end of movable broken circle device 10 is fixed on the inwall of cylinder of rotary kiln 1, and the other end contacts with the inwall of cylinder of rotary kiln 1.Movable broken circle device 10 is flexible material.When cylinder of rotary kiln 1 rotates, because an end of movable broken circle device 10 is fixedly connected with the inwall of cylinder of rotary kiln 1, so can dragging movable broken circle device 10, the rotation of cylinder of rotary kiln 1 rotates.Movable broken circle device 10 ceaselessly contacts with the inwall of cylinder of rotary kiln 1 always, has so just stoped the formation of kiln circle.Movable broken circle device 10 can arrange one, also can arrange many.
Rotary kiln of the present utility model is widely used, its not only can the treatment process to above-mentioned glyphosate mother solution in resulting solid materials burn, also can be applied in the burning of other phosphorous waste water or mother liquor.
Claims (3)
1. the treatment unit of a phosphorus-containing wastewater, it is rotary kiln, it is characterized in that described rotary kiln is provided with combustion unit and cylinder of rotary kiln, and described combustion unit is set on the described cylinder of rotary kiln, and the outer wall of described cylinder of rotary kiln is provided with percussion vibration device; The inwall of described cylinder of rotary kiln is provided with movable broken circle device, and the broken circle of described activity device one end is fixedly connected with the inwall of described cylinder of rotary kiln, and the other end contacts with described cylinder of rotary kiln inwall.
2. the treatment unit of phosphorus-containing wastewater according to claim 1 is characterized in that being provided with fixed block between the outer wall of described percussion vibration device and described cylinder of rotary kiln.
3. the treatment unit of phosphorus-containing wastewater according to claim 2 is characterized in that described percussion vibration device comprises striking rod, hammer and striking rod stationary installation.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201320245501 CN203256080U (en) | 2013-05-08 | 2013-05-08 | Phosphorus-containing wastewater processing device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201320245501 CN203256080U (en) | 2013-05-08 | 2013-05-08 | Phosphorus-containing wastewater processing device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN203256080U true CN203256080U (en) | 2013-10-30 |
Family
ID=49468664
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 201320245501 Expired - Lifetime CN203256080U (en) | 2013-05-08 | 2013-05-08 | Phosphorus-containing wastewater processing device |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN203256080U (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103274380A (en) * | 2013-05-08 | 2013-09-04 | 山东潍坊润丰化工有限公司 | Glyphosate mother liquid treatment method and device |
-
2013
- 2013-05-08 CN CN 201320245501 patent/CN203256080U/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103274380A (en) * | 2013-05-08 | 2013-09-04 | 山东潍坊润丰化工有限公司 | Glyphosate mother liquid treatment method and device |
| CN103274380B (en) * | 2013-05-08 | 2015-09-16 | 山东潍坊润丰化工股份有限公司 | The treatment process of glyphosate mother solution and device |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN103274380B (en) | The treatment process of glyphosate mother solution and device | |
| CN100558633C (en) | The method for preparing PHOSPHORIC ACID TECH.GRADE, food grade phosphoric acid and industrial monoammonium phosphate with phosphoric acid by wet process | |
| CN103964622B (en) | A kind of comprehensive treating process of industrial organophosphorus waste liquid and resource utilization method | |
| CN102910594B (en) | Method for concentrating waste sulfuric acid by utilizing waste heat of titanium dioxide calcinator | |
| CN1962421B (en) | Phosphorite acidolysis method | |
| WO2022061958A1 (en) | Harmless and resourceful integrated treatment method and system for oil sludge | |
| CN101913637B (en) | Process method for producing fluorine compounds and silicon compounds by cleanly utilizing fluosilicic acid | |
| CN102448877B (en) | Production of ammonium phosphates | |
| CN102874786A (en) | Processing method of glyphosate mother liquor | |
| CN104562180A (en) | Method for preparing calcium sulfate whisker from phosphogypsum | |
| CN110550793B (en) | Purification process of salt in phosphate-containing wastewater | |
| CN101857211A (en) | Method for preparing industrial grade monoammonium phosphate from wet-process phosphoric acid | |
| CN103553722A (en) | Method for preparing super phosphate by use of ardealite slag site sewage | |
| CN105197905A (en) | Production method for extracting phosphorite cogeneration feed grade monocalcium phosphate and industrial grade monoammonium phosphate | |
| CN104411626A (en) | Production of ammonium phosphates | |
| CN103420549A (en) | Harmless waste treatment method in coal chemical industry | |
| CN104071818A (en) | Method for separating calcium, magnesium and phosphorus elements from phosphate tailings by adopting water leaching and ammonium leaching | |
| CN102874983B (en) | Method for treating N-Phosphonomethyl iminodiacetic acid (PMIDA) mother liquid | |
| CN103569981A (en) | Method for producing orthophosphate products from polyphosphates through hydrolysis | |
| CN101633584B (en) | A method for producing nitrogen phosphorus potassium compound fertilizer with water-insoluble potassium-containing rock | |
| CN101591011B (en) | Method for treating waste acid into calcium hydrophosphate fertilizer | |
| CN203256080U (en) | Phosphorus-containing wastewater processing device | |
| CN102126733A (en) | Method for preparing submicron flaky magnesium hydroxide from magnesite | |
| CN206692498U (en) | A kind of saliferous phosphorus-containing wastewater recycling treatment system | |
| CN112094004A (en) | Novel sludge pyrohydrolysis treatment system and method capable of recycling carbon source |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C56 | Change in the name or address of the patentee | ||
| CP03 | Change of name, title or address |
Address after: 262737 Shandong Haiyuan Weifang Binhai Economic and Technological Development Zone Street No. 600 Patentee after: Shandong Weifang Rainbow Chemical Co.,Ltd. Address before: Haiyuan Binhai Economic and Technological Development Zone in Shandong province Weifang city 262737 Street No. 600 Patentee before: SHANDONG WEIFANG RAINBOW CHEMICAL Co.,Ltd. |
|
| CP02 | Change in the address of a patent holder |
Address after: No. 03001, chlor alkali Road, Weifang Coastal Economic Development Zone, Shandong, Shandong Patentee after: Shandong Weifang Rainbow Chemical Co.,Ltd. Address before: 262737 Shandong Haiyuan Weifang Binhai Economic and Technological Development Zone Street No. 600 Patentee before: Shandong Weifang Rainbow Chemical Co.,Ltd. |
|
| CP02 | Change in the address of a patent holder | ||
| CX01 | Expiry of patent term |
Granted publication date: 20131030 |
|
| CX01 | Expiry of patent term |