Inter-plant waste heat integration for industrial park using two medium fluids

doi:10.11949/j.issn.0438-1157.20181145

Abstract

Abstract:

Considering the cluster effect of industrial park, it is expectable that could improve energy efficiency of the entire park by recovering the waste heat in each single plant via inter-plant medium fluids which absorb heat in some plants and release heat into other plants. Obviously, the selection of heat exchange medium and the setting of medium heat recovery loop will highly affect the optimal design of the waste heat recovery system and the energy-saving effect. Thus, other than single medium integration strategy, this work uses both hot water and thermal oil as mediums to implement the inter-plant waste heat integration. A heat exchanger network (HEN) superstructure coupling the matches between medium fluids and inner-plant process streams and the allocation of medium streams across plants is proposed. Accordingly, a mixed-integer non-linear programming (MINLP) model is formulated for network optimization aiming at the target of minimum total annual cost. At last, an example involving three plants is studied in three synthesis cases (single medium-single loop, single medium-dual loops, and dual mediums-dual loops). The effectiveness of the proposed method was verified by comparison.

Key words: inter-plant waste heat integration, medium fluid, heat transfer, optimization, system engineering

摘要：

发挥园区集群效应，借助中间介质回路将工业园区中各单厂内的余热于厂际间进一步回收利用，能够显著提高园区整体能源效率。其中，中间介质回路的设置与介质的选择将关系到整个余热回收系统的最优设计与节能效果。因此，不同于目前研究仅采用一种中间介质的集成策略，同时选用热水和导热油为介质开展厂际余热集成研究。提出耦合介质与厂内流股换热及介质流股在厂际间分配的换热器网络超结构，以年度总费用最小为目标建立MINLP热集成数学模型，优化获得包含介质回路结构与厂内换热器网络结构等内容的园区余热集成结果。最后，在一个包含3个厂的厂际余热集成案例中，分别研究了单种介质单回路、单种介质双回路及双种介质双回路3种情况，通过对比验证了所提方法的有效性。

关键词: 厂际余热集成, 中间介质, 传热, 优化, 系统工程

CLC Number:

TQ 021.8

Changhao WU, Linlin LIU, Lei ZHANG, Jian DU. Inter-plant waste heat integration for industrial park using two medium fluids[J]. CIESC Journal, 2019, 70(2): 431-439.

吴长昊, 刘琳琳, 张磊, 都健. 采用两种中间介质的工业园区厂际余热集成[J]. 化工学报, 2019, 70(2): 431-439.

Figures/Tables 8

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Stream	F/(kW·K^-1)	T _in /℃	T _out/℃	q/kW
plant A
1	200	60	90	6000
2	200	40	100	12000
3	150	50	150	15000
4	200	50	160	22000
plant B
5	300	20	100	24000
6	600	50	70	12000
7	600	130	180	12000

Stream	F/(kW·K^-1)	T _in /℃	T _out/℃	q/kW
plant A
1	200	60	90	6000
2	200	40	100	12000
3	150	50	150	15000
4	200	50	160	22000
plant B
5	300	20	100	24000
6	600	50	70	12000
7	600	130	180	12000

Item	Case 1	Case 2	Case 3
cost of heat exchangers/(USD·a^-1)	566873	796146	889677
hot utility /kW	42000	42000	42743.1
cold utility /kW	0	0	743.1
utility cost/(USD·a^-1)	6300000	6300000	6417410
cost of piping and pumping/(USD·a^-1)	460345	428479	439814
TAC of HEN/(USD·a^-1)	7327217	7524625	7746901

Item	Case 1	Case 2	Case 3
cost of heat exchangers/(USD·a^-1)	566873	796146	889677
hot utility /kW	42000	42000	42743.1
cold utility /kW	0	0	743.1
utility cost/(USD·a^-1)	6300000	6300000	6417410
cost of piping and pumping/(USD·a^-1)	460345	428479	439814
TAC of HEN/(USD·a^-1)	7327217	7524625	7746901

A	——过程换热器面积，m²
A _hu,A _cu	——分别为热、冷公用工程面积，m²
A _f	——年度费用因子
B,D	——换热器面积费用系数
C _hu,C _cu	——分别为热、冷公用工程单位费用，USD?kW^-1?a^-1
CH	——换热器的固定安装费用，USD?a^-1
ec(p,i)	——p厂i过程流股的热负荷，kW
ec(p,j)	——p厂j过程流股的热负荷，kW
F(p,i)	——p厂中i过程流股的热容流率，kW?K^-1
F(p,j)	——p厂中j过程流股的热容流率，kW?K^-1
F _c(p,g)	——p厂g冷介质流股的热容流率，kW?K^-1
F _h(p,g)	——p厂g热介质流股的热容流率，kW?K^-1
f(p,g,p')	——p厂至p'厂g介质流股热容流率，kW?K^-1
f(p',g,p)	——p'厂至p厂g介质流股热容流率，kW?K^-1
K	——传热系数
NOK	——换热器网络总级数
piping	——管道费用，USD?a^-1
pumping	——泵送费用，USD?a^-1
q _h,q _c	——分别为热、冷中间介质与过程流股换热量，kW
q _hu,q _cu	——分别为热、冷公用工程换热量，kW
ΔT	——换热器的平均传热温差，℃
ΔT _min	——最小传热温差，℃
t(p,i,k)	——p厂i热过程流股在k级的温度，℃
t(p,j,k)	——p厂j冷过程流股在k级的温度，℃
t _c(p,g,k)	——p厂g冷中间介质流股在k级的温度，℃
t _c _, _in(p,g)	——g冷中间介质流股入p厂的温度，℃
t _c _, _out(p′,g)	——g冷中间介质流股出p′厂的温度，℃
t _h(p,g,k)	——p厂g热中间介质流股在k级的温度，℃
t _h _, _in(p,g)	——g热中间介质流股入p厂的温度，℃
t _h _, _out(p′,g)	——g热中间介质流股出p′厂的温度，℃
t _in(p,i)	——p厂i热过程流股的起始温度，℃
t _in(p,j)	——p厂j热过程流股的起始温度，℃
t _out(p,i)	——p厂i热过程流股的目标温度，℃
t _out(p,j)	——p厂j热过程流股的目标温度，℃
dt _c(p,i,g,k)	——i流股与g流股于p厂k级的温差，℃
dt _cu(p,i)	——i流股与冷公用工程于p厂的温差，℃
dt _h(p,j,g,k)	——j流股与g流股于p厂k级的温差，℃
dt _hu(p,j)	——j流股与热公用工程于p厂的温差，℃
y	——表示厂际管道是否存在的二元变量
z	——表示换热器是否存在的二元变量
Γ	——热流股与冷流股的温差最大值，℃
下角标
g	——中间介质流股
i	——热过程流股
j	——冷过程流股
k	——换热器网络级数
p	——单厂
p'	——p厂以外的其余单厂