CN101886007A - Heating method of feed gas in gas dehydration process - Google Patents

Abstract

The invention discloses a heating method of feed gas in the natural gas dehydration process. The method utilizes the heat carried by dry gas discharged by the absorption tower and triethylene glycol lean liquor in dehydration technology and comprises the following steps: two heat exchangers are arranged between the feed gas and the absorption tower; the feed gas passes through a first heat exchanger and a second heat exchanger and enters the absorption tower for dehydration; after dehydration, the obtained dry gas is discharged by the absorption tower and then enters the first heat exchanger to perform heat exchange with the feed gas; the triethylene glycol rich liquor discharged by the absorption tower is rectified by a rectifying tower to obtain the triethylene glycol lean liquor, the triethylene glycol lean liquor enters the second heat exchanger to perform heat exchange with the feed gas again; and the feed gas separately performs twice heat exchanges with the dry gas discharged by the absorption tower and the triethylene glycol lean liquor and then enters the absorption tower for dehydration. By using the invention, the exhaust heat, namely the heat of the dry gas discharged by the absorption tower and triethylene glycol lean liquor, in the technological process can be effectively utilized; and the heat exchangers have small floor space, the operation and maintenance are convenient, the production cost and operation cost are low, and the operation is safe and reliable.

Description

The heating means of unstripped gas in the natural gas dehydration process

One, technical field

What the present invention relates to is natural gas dehydration process, and what be specifically related to is the heating means of unstripped gas in a kind of natural gas dehydration process.

Two, background technology

For improving the natural gas transport quality, guarantee the natural gas transport safe operation, Sweet natural gas must carry out effective processed before entering gas pipe line.Reason is can separate out water vapour from Sweet natural gas when gas pipe line internal pressure and temperature change, and forms liquid water and accumulates in the gas pipe line lower; Under certain temperature and pressure, the part alkane molecule will form solid-state ice and snow shape hydrate in free-water and the Sweet natural gas simultaneously.These materials not only can dwindle effective conveying cross section of gas pipe line, increase transporting resistance, strengthen power consumption, and also can stop up valve, instrument even gas pipe line when serious, influence steady air feed.

Existing natural gas dehydration process is to adopt TEG Dehydration Processing, promptly will not make the Sweet natural gas (being designated hereinafter simply as unstripped gas) of processed earlier, and the input absorption tower contacts the output of dehydration back with triglycol.If the unstripped gas temperature is very low, and the triglycol soltion viscosity is bigger during low temperature, carries out thermal exchange under this condition, then can influence the dehydrating effect of unstripped gas.In order to guarantee the dehydrating effect of Sweet natural gas, water jacket heater then is set before the absorption tower, consult Fig. 1, unstripped gas is heated to enters the absorption tower when temperature required again, dehydrating effect is guaranteed like this, but in this technology after treatment the triglycol lean solution and the Sweet natural gas (being designated hereinafter simply as dry gas) after the dehydration that after processed, obtains in also carry certain heat and do not obtain utilizing, for heating raw gas water jacket heater need be set in addition, cause this technological equipment investment big, the running cost height, energy dissipation.

Three, summary of the invention

The objective of the invention is to provide the heating means of unstripped gas in a kind of natural gas dehydration process at the problems referred to above, utilizing dry gas in the technological process (i.e. dehydration back Sweet natural gas) and the entrained heat of triglycol lean solution is unstripped gas (promptly not making the Sweet natural gas of processed) heating, the waste heat that produces in the technological process is effectively utilized, reduce facility investment and running cost.

The present invention is achieved through the following technical solutions: the heating means of unstripped gas are to utilize absorption tower in the dewatering process to discharge the heat that carries in dry gas and the triglycol lean solution to heat for unstripped gas in the natural gas dehydration process, specifically are that two interchanger are installed between unstripped gas and absorption tower; Unstripped gas enters the absorption tower through first interchanger, second interchanger and dewaters; The dry gas that dehydration back obtains is discharged from the absorption tower and is entered first interchanger again and unstripped gas carries out thermal exchange; Enter second interchanger after the triglycol lean solution of triglycol rich solution that discharge on the absorption tower, carry out thermal exchange again with unstripped gas through obtaining after the rectifying tower rectifying; Dry gas that unstripped gas is discharged with the absorption tower respectively and triglycol lean solution enter the absorption tower again after through twice thermal exchange and dewater.

Adopt the positively effect of technique scheme: the present invention is by installing two interchanger between unstripped gas and absorption tower, with the waste heat that produces in the technological process is that the dry gas of absorption tower discharge and the heat of triglycol lean solution effectively utilize, interchanger can be integrated on the sledge plate with the triglycol dewatering unit, simplifies heating process; The interchanger floor space is little, convenient operating maintenance, and it is invested much smaller than process furnace, can reduce the production run cost greatly, and is the heat exchange transferring heat energy, has avoided open firing point, operating safety, reliable.

Four, description of drawings

Fig. 1 is the process flow diagram of prior art;

Fig. 2 is a process flow diagram of the present invention.

Among the figure: 1 first interchanger, 2 second interchanger, 3 absorption towers, 4 rectifying tower, 5 process furnace.

Five, embodiment: the invention will be further described below in conjunction with embodiment:

Embodiment 1: the peaceful Sweet natural gas of Daqing oil field gas gathering station adopts TEG Dehydration Processing, for 2.1 ℃ Sweet natural gas, is difficult to reach the dehydration indexes requirement, and therefore, adopting the inventive method is that unstripped gas heats, and the unstripped gas segmentation sees Table 1.

Table 1 feed gas composition table (mol%)

Wherein require the water dew point of outer gas transmission smaller or equal to-15 ℃.

1, technical process and operating parameter

(1) technical process

Technical purpose of the present invention is that the waste heat that will produce in the technological process promptly becomes triglycol lean solution entrained heat to effectively utilize with the triglycol rich solution through rectifying tower rectifying aftertreatment from the dry gas of absorption tower discharge, reduction equipment and running cost, its technical process as shown in Figure 2, first interchanger 1 in the invention is contained between unstripped gas and the absorption tower 3, second interchanger 2 is mounted between first interchanger 1 and the absorption tower 3, and pipeline is connected between first interchanger 1 and second interchanger 2, second interchanger 2 and the absorption tower 3.First interchanger 1 and second interchanger 2 are installed between the admission line and absorption tower 3 of unstripped gas in the mode that is connected in series.After unstripped gas is imported first interchanger 1 by admission line, in first interchanger, carry out entering second interchanger 2 after gas-gas heat exchange, in second interchanger, carry out entering absorption tower 3 dehydrations after the solution-air heat exchange with the triglycol lean solution with dry gas.The triglycol lean solution also enters absorption tower 3 when unstripped gas enters absorption tower 3, unstripped gas contacts in absorption tower 3 with the triglycol lean solution and dewaters, after the dry gas that the dehydration back obtains is discharged from absorption tower 3, carry out thermal exchange through first interchanger 1 and the unstripped gas that enters first interchanger 1 successively again, improve the unstripped gas temperature.The triglycol rich solution pumps into rectifying tower 4 rectifying after discharging filtration from absorption tower 3, and the triglycol lean solution through obtaining after rectifying tower 4 rectifying enters second interchanger 2 and absorption tower 3 after filtering.The triglycol lean solution and the unstripped gas that enter second interchanger 2 carry out thermal exchange, enter absorption tower 3 after, in absorption tower 3, contact with unstripped gas, unstripped gas is dewatered.The triglycol lean solution that triglycol rich solution in the technology obtains after rectifying tower 4 rectifying enters absorption tower 3 through second interchanger 2, recycles repeatedly.Entering the temperature that second interchanger 2 enters after the unstripped gas with second interchanger 2 of flowing through carries out the secondary thermal exchange in the process on absorption tower 3 again unstripped gas after the triglycol lean solution improves on the basis of the thermal exchange first time, at this moment, the temperature of unstripped gas can reach 20～30 ℃, can satisfy the required temperature condition of dehydration in absorption tower 3 fully.Like this, make flow of feed gas through two interchanger by first interchanger 1, second interchanger of installing 2, carry out thermal exchange twice with the dry gas and the triglycol lean solution of absorption tower 3 discharges respectively, guarantee that unstripped gas enters absorption tower 3 and dewaters being higher than temperature condition more than 15 ℃, guarantees dehydrating effect.

(2) device operating parameter

The device operating parameter sees Table 2.

Table 2 triglycol dewatering unit operating parameter

Wherein, the ratio that accounts for the Sweet natural gas total amount owing to the water yield that removes is very little, the mass rate G of dry gas ₂Can be approximated to mass rate G with unstripped gas ₁Identical.

2, experimental result

Unstripped gas enters first interchanger 1 and 3 dry gas of discharging carry out thermal exchange from the absorption tower, and the heat of exchange is Q ₁Because the efficient plate-fin heat exchanger of first interchanger, 1 inner employing can carry out effective heat exchange when warm end temperature difference is 0.5 ℃.Therefore in gas-gas heat exchange that first interchanger 1 carries out, the heat that unstripped gas absorbs can be approximately equal to the heat that dry gas provides, then Q ₁For: (C ₁Be the dry gas mean specific heat, kJ/kg ℃)

Q ₁＝G ₂·C ₁·(T ₄-T ₅)＝2.39×10 ⁵kJ/h

Unstripped gas enters second interchanger 2 and carries out the solution-air thermal exchange with the triglycol lean solution, and the heat of exchange is Q ₂Q then ₂For: (C ₂Be triglycol lean solution mean specific heat, KJ/kg ℃)

Q ₂＝G ₃·C ₂·(T ₆-T ₇)＝3.91×10 ⁴kJ/h

Simultaneously, the temperature of unstripped gas 1 after through first interchanger 1 rises to 18.0 ℃ by 2.1 ℃, drawn heat Q ₁=2.39 * 10 ⁵KJ/h can select efficient plate-fin heat exchanger for use, overall heat transfer coefficient: K=1260kJ/ (m ²H ℃), the temperature of dry gas after through first interchanger 1 reduced to 5.3 ℃ by 22.0 ℃.

The cold-end temperature difference of interchanger: Δ T ₁=T ₅-T ₁=3.2 ℃

Warm end temperature difference: Δ T ₂=T ₄-T ₂=4.0 ℃

The interchanger log-mean temperature difference is:

The heat interchanging area of first interchanger 1: ${\mathrm{<figure-callout\; id="1"\; label="F"\; filenames="HSA00000158155600012.png"\; state="\{\{state\}\}">F</figure-callout>}}_1=\frac{Q_1}{K\&CenterDot;\mathrm{\&Delta;T}}=\frac{239000}{1260\&times;3.6}={52.7\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="HSA00000158155600012.png"\; state="\{\{state\}\}">m</figure-callout>}}^2$

The temperature of unstripped gas after through second interchanger 2 is 21.2 ℃, drawn heat Q ₂=3.91 * 10 ⁴KJ/h can select U type tube heat-exchanger for use, overall heat transfer coefficient: K=140kJ/ (m ²H ℃), the temperature of triglycol lean solution after through second interchanger 2 reduced to 130 ℃ by 185 ℃.

The cold-end temperature difference of interchanger: Δ T ₃=T ₇-T ₂=112 ℃

Warm end temperature difference: Δ T ₄=T ₆-T ₃=163.8 ℃

The interchanger log-mean temperature difference is:

The heat interchanging area of second interchanger 2: ${\mathrm{<figure-callout\; id="2"\; label="F"\; filenames="HSA00000158155600012.png"\; state="\{\{state\}\}">F</figure-callout>}}_2=\frac{Q_2}{K\&CenterDot;\mathrm{\&Delta;}{T}^{\&prime;}}=\frac{39100}{140\&times;136.3}={2.04\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="HSA00000158155600012.png"\; state="\{\{state\}\}">m</figure-callout>}}^2$

3, experiment conclusion

From above-mentioned data as can be seen, design routinely for reaching triglycol dewatering unit air inlet requirement, if adopt existing technology then press the described technical process of Fig. 1, should be established process furnace 5, with unstripped gas by T ₁Be heated to T ₃Needed heat degree Q is and formerly with the required total heat of process furnace heating is: Q=G ₁C (T ₃-T ₁)=2.78 * 10 ⁵KJ/h (C is the unstripped gas mean specific heat, KJ/kg ℃), promptly unstripped gas is heated to 21.2 ℃ by 2.1 ℃, and the heat that needs is 2.78 * 10 ⁵KJ/h.Adopt invented technology then to utilize the 3 interior entrained waste heats of discharging dry gas from the absorption tower fully, other needs the triglycol lean solution to provide 3.91 * 10 ⁴The kJ/h heat for its slightly do additional, 1/6 of the not enough conventional heating process of its energy consumption, the whole service cost can reduce greatly.By table 2 as seen: under the situation that guarantees the normal dehydration of triglycol, the temperature of unstripped gas can be brought up to more than 20 ℃, and energy-saving effect is obvious.

Two little type heat exchangers are set in technology in view of the above, and can be integrated on the sledge plate with the triglycol dewatering unit.Aspect facility investment, the investment of two little type heat exchangers will be much smaller than process furnace, has simplified that heating process, floor space are little, convenient operating maintenance, has reduced open firing point, safe and reliable to operation, has reached energy-saving and cost-reducing purpose, has good economic benefit.

Claims (2)

1. heating means of unstripped gas in the natural gas dehydration process, it is characterized in that: this method is to utilize absorption tower in the dewatering process to discharge the heat that carries in dry gas and the triglycol lean solution to heat for unstripped gas, specifically is that two interchanger are installed between unstripped gas and absorption tower; Unstripped gas enters absorption tower (3) through first interchanger (1), second interchanger (2) and dewaters; The dry gas that dehydration back obtains from the absorption tower (3) discharge and enter first interchanger (1) again and carry out thermal exchange with unstripped gas; Enter second interchanger (2) after the triglycol lean solution of triglycol rich solution that discharge on absorption tower (3), carry out thermal exchange again with unstripped gas through obtaining after rectifying tower (4) rectifying; Dry gas that unstripped gas is discharged with absorption tower (3) respectively and triglycol lean solution enter absorption tower (3) again after through twice thermal exchange and dewater.

2. the heating means of unstripped gas in the natural gas dehydration process according to claim 1 is characterized in that: first interchanger (1) and second interchanger (2) are installed between the admission line and absorption tower (3) of unstripped gas in the mode that is connected in series.

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