CN1398904A

CN1398904A - Dry propylene recovering and utilizing process from tail gas of polypropylene plant

Info

Publication number: CN1398904A
Application number: CN01130432A
Authority: CN
Inventors: 董京拴
Original assignee: TAIFU CHEMICAL CO Ltd DAQING CITY
Current assignee: TAIFU CHEMICAL CO Ltd DAQING CITY
Priority date: 2001-11-15
Filing date: 2001-11-15
Publication date: 2003-02-26

Abstract

The present invention belongs to the field of chemical environment protecting and energy saving technology. The present invention features that unreacted gaseous propylene from the polypropylene plant is recovered with multiple-pipe cyclonic separator, oil-free lubricated circulating propylene compressor and propylene condensator for reuse; and that there are additional deactivating discharge tank for obtaining low-pressure recovered propylene with trace oxygen and nitrogen impurity, buffering tank to reduce water content in recovered propylene and regulating valve or frequency varying regulation technique to control the pressure in the buffering tanks to make the recovered propylene capable of being used directly.

Description

Polypropylene plant tail gas propylene dry method reclaims and utilizes

The invention belongs to the chemical industry environmental protection field of energy-saving technology

One, polypropylene plant tail gas propylene reclaims and utilizes present situation

1, present domestic liquid phase noumenal method polypropylene plant tail gas propylene recovery method has the discharging torch to burn and reclaims two kinds with the gas holder compression condensation.The retrieval CSTAD has Synthetic Rubber Plant, Yueyang Petro-Chem. Complex's " polypropylene tail gas recycle " to relate to that " this project adopts novel deduster, vacuumizes joint nitrogen, and compression condensation reclaims modern technique such as propylene and builds up tail gas propylene retrieving arrangement.When propylene content in the tail gas more than 90%, oxygen level is less than 0.5%, and nitrogen content is less than 10% o'clock, and the propylene rate of recovery is greater than 90%, current consumption 348.7Kw/t." the northern technology net http://www.ntem:tj.cn/kjjxi/0410-kj-.ht of retrieval has " the production domesticization polypropylene monomer Membrane recovery unit MRU once drive success " in day nation membrane technique national project research centre to relate to that " this retrieving arrangement is to utilize membrane separation technique to reclaim the propylene monomer in the gas holder off-gas in the polypropylene building-up process, at present, nearly 40 large-scale polyolefin devices of cover of China and more than 60 cover medium and small sized units, adopt the liquid-phase bulk polymerization method to produce mostly, therefore the propylene monomer that contains higher concentration in the gas holder off-gas is admitted to torch and burns, both cause a large amount of energy dissipations, polluted environment again." above two pieces of documents all are the recovery technologies at polypropylene tail gas; contain 10% nitrogen of having an appointment etc. in gas holder, the tail gas and make and easily produce secondary pollution when reclaiming in the propylene the big and discharging non-condensable gas of water content because of adopting; the gas holder floor space is bigger; invest higher, especially very high in the north of china in winter working cost.

2, about reclaiming the present situation of utilizing of propylene

(1) is used to prepare LP gas fuel; (2) utilize (3) to produce isopropyl benzene etc. by membrane sepn or distillation technology purification back with catalytic rectification process.Retrieval Chinese science and technology journal data storehouse has " the polypropylene plant tail gas recycle is utilized technology " of chemical industry system of Tsing-Hua University to relate to that " this paper attempts utilizing catalytic rectification process to solve the absorption problem of propylene in the tail gas.Benzene and propylene are reacted the generation isopropyl benzene on catalyzer.Preliminary study shows, when to use nitrogen and propylene volume ratio be 1: 1 gas mixture, can make propylene conversion greater than 90%, and the selectivity of gained isopropyl benzene is greater than 90%.The mass space velocity of propylene can reach 1.5～2.5h ^-1, prove that catalytic rectification process is one of up-and-coming engineering in this respect." adopt gas holder to reclaim the gained propylene in a word at present to make fuel and maybe need drop into the back use of purifying of refining on the substantial contribution, tripping device because of of poor quality the degradation, cost recovery is higher, and economic benefit is relatively poor.

Two, the objective of the invention is to overcome above-mentioned the deficiencies in the prior art and provide low, the simple and practical polypropylene plant tail gas propylene dry method of a kind of cost to reclaim and utilize technology.

Three, technical scheme:

1, the source of tail gas propylene:

Polypropylene plant tail gas propylene is generally from the flash distillation still.This technology utilization 12m ³Polymeric kettle, 14～18m ³Flash distillation still, 8m ³The deactivation discharge tank is as the tail gas key equipment of originating.The deactivation discharge tank is set below the flash distillation still.The flash distillation still is used for providing the low pressure propylene to deactivation discharge tank blowing with to exhaust gas recovery system, and the deactivation discharge tank is used for the deactivation and the discharging packing (or going to granulation workshop section) of polypropylene powder.Concrete operation method is as follows:

1), recovery and material spray flash distillation:

After polyreaction finishes, responseless propylene is recovered to the middle Propylene Recovery System of pressing, after the pressure equilibrium 1.3～1.5Mpa.The gas-phase propene of remaining in the polymeric kettle 〉=0.8Mpa as in press the degree of depth to reclaim the source of tail gas propylene.Reclaim propylene behind the 08Mpa to flash distillation still material spray 3～4 times, after each material spray static about 3 minutes, open flash distillation still DN50 recovery valve then and reclaim the low pressure propylene till the system pressure balance.The flash distillation still is behind deactivation discharge tank blowing, and the flash distillation still will be in vacuum state, can return propylene to pressure-fired to the flash distillation still by recovery system.

2), the purification of deactivation discharge tank:

To deactivate earlier and jar be evacuated down to-0.08Mpa, and be vented to normal pressure behind the inflated with nitrogen 0.1MPa, and repeat to vacuumize, inflated with nitrogen, emptying manipulation 2～3 times, oxygen level≤0.5% o'clock is qualified in chemical examination jar.

3), blowing:

To deactivate jar earlier is evacuated down to-0.08Mpa, open flash distillation still dispensing valve, polypropylene powder is transferred in the deactivation discharge tank by the pressure reduction and the self-gravity action of flash distillation still overbottom pressure and vacuum take-off effect generation, generally speaking blowing operation secondary, after blowing finished, pressure was-0.02～0.03MPa.

4), displacement:

Elder generation is inflated with nitrogen 0.1Mpa in the deactivation discharge tank, and emptying vacuumizes then to normal pressure.Filling nitrogen, emptying, 2～3 oxygen level in jar≤0.5% of vacuum pumping repeatedly o'clock is qualified.

5), fill air deactivation (with effective catalyst time can save this operation) in the discharge tank to deactivation.

By above operation, responseless 〉=0.8MPa propylene is pressed degree of depth recovery system from polymeric kettle enters, and the low pressure propylene that contains trace nitrogen, oxygen impurities enters exhaust gas recovery system from the flash distillation still.

2, tail gas propylene surge tank and pressure-controlling thereof:

The tail gas propylene that comes from the flash distillation still behind the polypropylene dust that efficient multicyclone, circle fiber bag precipitator etc. are further carried secretly the separation tail gas propylene in tail gas propylene surge tank group.The surge tank group generally is made up of several placed in-line vertical or horizontal surge tanks, and surge tank group cubic capacity is advisable with 10～20 times of reclaiming with the compressor air-discharging amount.This technology replaces the propylene gas holder that extensively adopts at present with the surge tank group, its objective is that the water vapor of avoiding water generates in the gas holder, dissolved oxygen are to reclaiming the pollution of propylene.The pressure-controlling of surge tank group is at 0.02～0.2Mpa.Compress control method has three kinds: a kind of is manual control, periodical operation; Second kind is to add variable valve in the outlet of surge tank group, is parameter with surge tank group pressure, regulates the purpose that the compressor air-discharging amount reaches accurate control surge tank group pressure by PID; The third is to be parameter with surge tank group pressure, adopts variable-frequency control technique to regulate the purpose that the compressor air-discharging amount reaches accurate control surge tank group pressure.

3, compression, condensation are reclaimed and are utilized

1), the propylene of 0.8～1.5Mpa of coming from polymeric kettle after efficient multicyclone enters the compression of oil-free lubricatoin propylene recycle compressor, arrive the propylene condenser condensation, be recovered to the propylene withdrawing can and can directly measure to feed intake and be used for polypropylene production.

2), the propylene that comes from the surge tank group after oil-free lubricatoin propylene gas compressor compresses, propylene pressure reaches 1.2～1.8Mpa, again through the tail gas propylene condenser be cooled to≤30 ℃ become liquid phase and enter the recovery propylene tank.Reclaim impurity such as micro amount of oxygen, nitrogen only arranged in the propylene, can reach GB7716-98 industry propylene standard.Can be by reclaiming than the polypropylene production that is used to use effective catalyst with the fresh propylene blending, thereby reduce propylene unit consumption, energy consumption greatly, save a large amount of nitrogen, avoid reclaiming the discharging of noncondensable gas in the propylene, help environmental protection, be specially adapted to the intermittently recovery and the utilization of liquid phase noumenal method polypropylene tail gas propylene.

Four, the present invention compared with prior art has following advantage:

A part reclaims propylene and is directly used in polypropylene production from polymeric kettle after recycle compressor reclaims, and it is good to reclaim the propylene quality, utilizes cost extremely low; Owing to below this technology flash distillation still the deactivation discharge tank is set, the flash distillation still is mainly used in propylene and reclaims, so reclaim in the propylene micro amount of oxygen, nitrogen is only arranged; Since do not adopt gas holder, not moisture in the recovery propylene, can save the preposition water distributing can of compressor, surge tank group working cost is very low; The recovery propylene and the fresh propylene blending that can reach industrial propylene standard are used for polypropylene production, improve the polypropylene plant economic benefit greatly.

Claims

The present invention is a kind of polypropylene plant tail gas propylene recovery and utilizes technology, please five features below the present invention granted asylum:

1, reclaims directly with efficient multicyclone, oil-free lubricatoin propylene recycle compressor, propylene condenser that the responseless gas-phase propene of 0.8～1.5Mpa is used for polypropylene production in the polymeric kettle.
2, increase the deactivation discharge tank, make it to replace purification, displacement, deactivation, the discharging packaging process of flash distillation still, thereby make the low pressure recovery propylene that only contains micro amount of oxygen, nitrogen impurity from the flash distillation still;
3, replace gas holder with the surge tank group, thereby avoid reclaiming in the propylene moisture;
4, adopt variable valve or variable-frequency control technique control surge tank group resistance;
5, reclaim propylene and can reach GB7716-98 industry propylene standard, and produce polypropylene with effective catalyst after the fresh propylene blending.