Synchronous heat exchange type absorption column of gas and nox adsorption concentration technology
Technical field
The present invention relates to absorption column of gas, and NO
XThe environment protection treating of waste gas.
Background technology
Nitrogen oxide (mainly refers to NO and NO
2, common name NOx) and be emitted on the smog that can form yellow or brown in the air, be commonly called as " Huanglong ", be one of important pollution sources that cause at present atmosphere pollution.NO
XWaste gas not only can cause acid rain, acid mist, can also damage the ozone layer, and brings serious harm for natural environment and human being's production, life.Processes such as nitric acid industry, fuel combustion and automotive emission all can discharge a large amount of nitrogen oxide.According to incompletely statistics, the discharge capacity of China's nitrogen oxide in 2005 is in the prostatitis, countries in the world up to 2,220 ten thousand tons, and the atmosphere pollution and the acid rain problem that bring thus are serious, and economic loss is huge, has seriously restricted the sustainable development of Chinese society economy.Therefore control discharged nitrous oxides, strengthen the improvement of nitrogen oxides pollution, become in the environmental protection work a very urgent task.
The current technology that removes to nitrous oxides exhaust gas mainly is divided into dry method and wet method two big classes.Dry method mainly comprises catalytic reduction method, solid absorption method, plasma method, mainly is applicable to the low-concentration nitrogen oxide system, for example vehicle exhaust, fuel combustion waste gas etc.Wet method then mainly is to react the NO that absorbs high concentration by water, diluted acid, aqueous slkali
XWherein water absorbs the environmental protection technology that treatment technology is the most worth promotion, and it not only can realize NO
XThe environment protection emission of waste gas can also be with the NO in the waste gas
XAll reclaim and resource, and it is recycling for enterprise to produce the nitric acid that 1O~65% concentration does not wait according to actual needs.
The flow process of water absorbing NOx seems ordinary, absorption process is complicated unusually in fact, in absorption process, comprise the nitrogen oxide intermediate product that there are dispute in a plurality of reversible and irreversible chemical reactions and academia, the association because each reaction influences each other, wanting to study clear each step link wherein hardly may, therefore usually it was reduced to for two steps at research process: the first step is a gas phase oxidation: replenish air in the waste gas that contains nitrogen oxide, make NO be oxidized into the NO that can be absorbed by water
2: 2NO+O
2=2NO
2Second step absorbed for liquid phase: 3NO
2+ H
2O=2HNO
3+ NO, the NO of generation again with O
2Again carry out first step reaction, thereby circular response absorbs.
NO
XAbsorb the key point that concentrates and be the absorption process temperature controlling.NO
XAbsorption process is a strong exothermal reaction, if in the untimely transfer of heat of carrying out of each absorber portion, its operating temperature will raise, and will be unfavorable for NO
XAbsorption, exhaust emissions exceeds standard easily.The general operation temperature surpasses 40 ℃, and high pressure and low temperature all help absorbing, but temperature when being lower than 10 ℃ nitrogen oxide be dissolved in easily in the nitric acid and make salpeter solution band look, low temperature also can consume more chilled water and increase energy consumption simultaneously.Usually reaction absorbs the heat exchange of temperature control employing outer loop, and it realizes that simple to operate, bigger amount of liquid also makes filling surface wetting easily easily, improves the efficient of filler.Along with NO in the waste gas
XThe decline of concentration and flow, the heat of each absorber portion reaction scale and generation reduces gradually, and this moment, liquid circulation amount was all corresponding with the heat exchange amount to be reduced.
U.S. Drinkard company once proposed a kind of patent (CN96199789.3) that is used for nitric acid manufacturing, recirculation or recovery: earlier with nitric acid with NO
XNO in the source is oxidized to the nitrogen oxide of 3 valencys (as N
2O
3), aerating oxygen and water react again, generate nitric acid.This shows NO
XIn the nitric acid conversion process, also there is other reversible and irreversible reaction.Since partial reaction be the circulation carry out (be oxidized to NO as NO
2, and NO
2React again with water and to generate NO), facts have proved the method that adopts water or rare nitric acid normal pressure list tower or multitower series connection to absorb, exhaust emissions be difficult to reach discharging standards (<240mg/m3), have in addition still be " Huanglong ".It is main absorption equipment with the absorption tower that patent CN02138494.0 once proposed a kind of, and jet pump is auxiliary absorption equipment, and normal pressure absorbs the method for nitrogen oxide in the tail gas down with rare nitric acid single-stage circulation.Its actual effect remains to be investigated.The patent ZL200610039814.1 that the inventor herein is authorized has proposed a kind of a whole set of technology that reclaims nitrogen oxide of administering, comprise absorption, bleaching, concentration process, this cover technology (all adopts nitric acid to make oxidant in the enterprise that produces adipic acid, oxalic acid, DNT, again it is recycling to become high concentration nitric acid after the smoke of gunpowder absorbs) successful Application, but still there are some defectives, for example still need the outer circulation heat exchange on the one hand, so just increase many external equipments such as pump, heat exchanger, increased power consumption and running cost simultaneously; On the other hand, because reaction heat can only be just extraction heat exchange after absorption liquid is flowed through one section filler, therefore reaction heat shifts out hysteresis, cause each section filler temperature difference bigger, reaction rate is uncontrollable, and absorption efficiency is inhomogeneous, and this just needs more absorption approach level to satisfy technological requirement, make flow process longer, need 2~3 absorption towers usually.
Summary of the invention
The present invention proposes a kind of synchronous heat exchange type nitrogen oxide (NO
X) absorb concentration technology and device, guaranteeing NO
XWaste gas environment protection emission, the whole recovery become on the basis of 35~58% nitric acid, abandoned the external heat-exchanging system that high power consumes, only promptly realized carrying out synchronously of tower internal-response and heat exchange by the integrated of tower internals and optimization, saved energy consumption, improved the reaction absorption efficiency, made flow process and investment reduction significantly.
The concrete technical scheme of the present invention is as follows:
A kind of synchronous heat exchange type absorption column of gas, it is a bubble column, tower bottom has liquid outlet and air inlet, top of tower has tail gas outlet and absorption liquid outlet, as shown in Figure 1,1-3 layer heat exchange coil arranged between the bubble-cap of every layer of tower tray, heat exchange coil import and outlet are directly led to outside the tower body, as shown in Figure 2, can the flowing heat transfer medium in the heat exchange coil.Synchronous heat exchange type absorption column of gas of the present invention is applicable to the GAS ABSORPTION of obvious heat release when gas is absorbed by the absorption liquid that is adopted or heat absorption.
Above-mentioned synchronous heat exchange type absorption column of gas has 1-3 layer heat exchange coil between the bubble-cap of described every layer of tower tray, the absorption tower following, in, the number of plies that goes up the heat exchange coil between the bubble-cap of each several part tower tray can be identical or different.Because the bottom on absorption tower is absorbed the gas concentration height, thermal discharge or caloric receptivity are big, heat exchange coil can have three layers between the bubble-cap of the bottom column plate on absorption tower, the middle part column plate can have two layers of heat exchange coil, the concentration that the upper strata column plate is absorbed gas is low, thermal discharge or recept the caloric for a short time can have one deck heat exchange coil, and the number of plates ratio of upper, middle and lower portion is 2.5: 1.5: 1 usually.
Above-mentioned synchronous heat exchange type absorption column of gas, the distance between described upper, middle and lower portion column plate can be different.
Above-mentioned synchronous heat exchange type absorption column of gas, tower bottom can adopt 1-2 layer filler, can be structured packing or random packing, and every layer of filler top is furnished with liquid distribution trough, and the below is furnished with the filler bracing or strutting arrangement, and heat exchange coil is arranged in the middle of every layer of filler.
Above-mentioned synchronous heat exchange type absorption column of gas, described packing layer adopts structured packing, and row has 1 layer of heat exchange coil (as shown in Figure 3) between every dish filler, and every dish packed height is at 150mm~250mm; When adopting random packing, heat exchanger tube both can adopt the coil arrangement identical with structured packing also can be designed to vertical-type coil arrangement (as shown in Figure 4), and vertically the distance between each row of heat exchanger tube is 150mm~300mm, highly for equaling or near bed stuffing height.
A kind of nitrogen oxide (NO that adopts above-mentioned synchronous heat exchange type absorption column of gas
X) absorbing concentration technology, it is to contain NO
XWaste gas and air (1 volume NO consumes 0.75 volume O with certain proportion by the concentration of waste gas and kind
21 volume NO
2Consume 0.25 volume O
2The O that contains 0.2 volume in 1 volumes of air
2) after the mixing, at the bottom of the tower on absorption tower, enter, water or rare nitric acid as absorbent enter from cat head, gaseous mixture and absorbent be adverse current or cross-flow haptoreaction on fillers at different levels or column plate, reaction heat is in time taken away by the cooling water in the heat exchange coil on each layer filler and the column plate, gas up to standard after the purification is from the tailing column top discharge, and the certain density nitric acid that absorb, the reaction back produces is gone out by tower bottom flow.
Above-mentioned nitrogen oxide (NO
X) absorbing concentration technology, described absorption operating pressure is 0.4~1MPa (absolute pressure): when 0.4MPa≤operating pressure≤0.6MPa, adopt 30~32 theoretical stages to absorb; When 0.6MPa≤operating pressure≤0.8MPa, adopt 26~30 theoretical stages to absorb; When 0.8MPa≤operating pressure≤1MPa, adopt 22~26 theoretical stages to absorb.
Above-mentioned nitrogen oxide (NO
X) absorbing concentration technology, theoretical stage is realized by compound bubble cap plate or filler: every layer of compound bubble cap plate amounted to into 0.6 theoretical stage, and total number of actual plates is 36~54 in the absorption tower; Total nitrogen oxide (NO+NO in air inlet
2) during mass concentration higher (>30%), tower bottom also can adopt 1~2 layer of filler, packed height is 3~5m, every layer of filler top is furnished with liquid distribution trough, the below is furnished with the filler bracing or strutting arrangement, can adopt the diffusing heap or the structured packing of various acidproof materials, remainder adopts the bubble cap plate that is compounded with heat exchanger tube.
Above-mentioned nitrogen oxide (NO
X) the absorption concentration technology, heat exchange coil passes the tower wall and links to each other with the external refrigeration water circulation system, cooling water in the coil pipe in time shifts out nitrogen oxide and the heat that the water reaction is produced, and guarantees that operating temperature with the absorption reaction section between 20~40 ℃, helps reacting and carries out smoothly.
Above-mentioned nitrogen oxide (NO
X) absorb concentration technology and device, it is characterized in that the distance between plates between each layer column plate is also unequal.Because reaction is two-step reaction, and is not carrying out in the homophase respectively, the first step is gas phase oxidation 2NO+O
2=2NO
2, carry out in the main gas-phase space between each column plate; Second step absorbed for liquid phase: 3NO
2+ H
2O=2HNO
3+ NO carries out in the main liquid layer on column plate, and the NO that generates again with O
2Again carry out first step reaction.At the beginning because NO
2Concentration is higher, and liquid phase reactor accounts for leading, and heat release is many, need more heat exchange areas, so the lower panel spacing is less, between 0.35~0.5m, along with NO in the gas phase
XConcentration reduce, gas-phase reaction needs the more space and the time of staying, so distance between plates needs progressively to strengthen, between central panel spacing 0.4~0.6m, between upper board spacing 0.5~0.8m.
Adopt the nitrogen oxide (NO of synchronous heat exchange type absorption column of gas of the present invention
X) the absorption concentration technology, NO in the top discharge tail gas of absorption tower
XConcentration of emission<150ppm, speed<1kg/h; It is 35~58% nitric acid that absorption tower bottom obtains mass concentration.
The present invention has the following advantages:
1, the mode that adopts gradual reaction to move heat synchronously makes whole nox adsorption section temperature control evenly, and course of reaction approaches perfect condition, and the required practical filling material height and the number of plates reduce;
2, need not the heat exchange of big amount of liquid outer loop, greatly reduce power consumption, make whole flow process shorter compact more, a large amount of minimizings of outside corollary equipment make the investment of package unit descend significantly;
3, taken into full account the NO of variable concentrations
XThe principle and the feature of reaction, the setting of non-equidistant column plate makes the space utilization of whole piece tower reasonable more, effective;
4, waste gas pollution control and treatment is effective, NO in the tail gas
XConcentration of emission<150ppm, speed<1kg/h is lower than present discharge standard both domestic and external;
5, NO in the tail gas
XAll be recovered and be reproduced resource, generate the red fuming nitric acid (RFNA) that mass concentration 35~58% concentration are adjustable, can directly make oxidant, recycle;
6, do not produce secondary spent acid, waste water, environmental protection in the governance process;
7, apparatus of the present invention compactness, output/output investment ratio height is specially adapted to big, the NO of flow
XConcentration height, the demanding waste gas pollution control and treatment process of environment protection emission meet the development trend of present national environmental protection, energy-saving and emission-reduction, recycling economy.
Description of drawings
Fig. 1 is the compound synchronous heat exchange type nox adsorption tower structure schematic diagram of bubble-cap and packing layer, and wherein: S1 is industrial NO
xExhaust gas inlet; S2 is the outlet of 35%-58% nitric acid; S3 is the tail gas outlet; S4 is absorbent water or rare nitric acid import; 1 is filler; 2 is the packing layer heat exchanger tube; 3 is liquid distribution trough; 4 is compound bubble cap tray.
Fig. 2 is compound bubble-cap tray structure schematic diagram, and last figure is a front view, and figure below is a vertical view, and wherein: 5 is column plate; 6 is bubble-cap; 7 is the column plate heat exchange coil; 8 is downspout; 9 is tower body.
Fig. 3 is the packing layer horizontal-type heat exchanger tube schematic diagram of arranging, and wherein: 1 is filler; 2 is the packing layer heat exchanger tube; 9 is tower body; 10 are the condensed water import person in charge; 11 are the condensation-water drain person in charge.
Fig. 4 is the packing layer vertical-type heat exchanger tube schematic diagram of arranging, and wherein: 1 is filler; 9 is tower body; 10 are the condensed water import person in charge; 11 are the condensation-water drain person in charge; 12 is packing layer vertical-type heat exchanger tube.
The specific embodiment
Embodiment 1: the nitric acid of employing 40% is done the oxidant production adipic acid product, produces NO
XWaste gas, flow 5000Nm
3/ h, NO
XAverage quality concentration be 25%, wherein NO and NO
2Be about 2: 1.With waste gas and air by volume ratio enter the absorption tower after mixing at 2: 1, be that rare nitric acid waste water of 1.5% is as absorbent with mass concentration.The absorption tower operating pressure is 4.2atm, and the inner compound bubble cap plate of 50 layers of band heat exchange coil that adopts absorbs.10 of upper tray, 1 row's coil pipe between the column plate bubble-cap, distance between plates 0.8m; 15 of middle part column plates, 2 row's coil pipes, distance between plates 0.6m; 25 of bottom column plates, 3 row's coil pipes, distance between plates 0.5m.The absorption tower tower diameter is 2.4m.NO in the emptying end gas
XConcentration of emission 134ppm, speed 0.78kg/h.Flowing out mass concentration from absorber portion is that 40% nitric acid recycles.
Embodiment 2: the nitric acid of employing 55% is done the oxidant production catalyst for methanol, produces NO and NO
2Gas, about 1: 1 of ratio, flow 500Nm
3/ h.The absorption tower operating pressure is 8atm, and the top adopts the compound bubble cap plate of 30 layers of band heat exchange coil to absorb, and tower bottom is provided with 2 sections fillers, and 350Y type structured packing 4m is adopted in the top, and the high 200mm of every dish filler is provided with heat exchange coil between each dish; 38mm rectangular saddle ring filler 2m is adopted in the below, does not establish heat exchange coil.With waste gas and air by volume ratio to mix the back at 1: 2 is that the structured packing below enters the absorption tower in the middle of two sections fillers, in addition with one air (with NO
XGas volume was than 1: 1) be that rectangular saddle ring filler below enters the absorption tower and is used as bleaching high concentration nitric acid from tower bottom.4 of column plate section upper tray, 1 row's coil pipe between the column plate bubble-cap, distance between plates 0.6m; 6 of middle part column plates, 2 row's coil pipes, distance between plates 0.5m; 10 of bottom column plates, 3 row's coil pipes, distance between plates 0.4m.The absorption tower tower diameter is 1m.NO in the emptying end gas
XConcentration of emission 68ppm, speed 0.085kg/h.Flowing out mass concentration from absorption tower bottom and be 55% nitric acid recycles.
Embodiment 3: the nitric acid of employing 50% is done oxidant to produce oxalic acid, produces to contain 50% NO and NO
2Gas, flow 1500m
3/ h.With waste gas and air by volume ratio enter the absorption tower after mixing at 1: 2.5, the absorption tower operating pressure is 6.8atm, absorbent is a clear water.The top adopts the compound bubble cap plate of 30 layers of band heat exchange coil to absorb, and tower bottom is provided with 1 section filler, adopts 500Y type structured packing 3m, and the high 200mm of every dish filler is provided with heat exchange coil between each dish.9 of column plate section upper tray, 1 row's coil pipe between the column plate bubble-cap, distance between plates 0.5m; 16 of middle part column plates, 2 row's coil pipes, distance between plates 0.45m; 15 of bottom column plates, 3 row's coil pipes, distance between plates 0.4m.The absorption tower tower diameter is 1.6m.NO in the emptying end gas
XConcentration of emission 92ppm, speed 0.345kg/h.Flowing out mass concentration from absorption tower bottom and be 50% nitric acid recycles.