Vapor displacement from current tank truck filling assumes a 100 gal/min fill rate with an outage loss of 2 g/s.
4.9.3 Natural Gas Transmission and Distribution
Natural gas is transported through pipelines with compressors that maintain a pressure ranging from 220 to 1100 psi. A typical distribution pressure is 800 psi. Marginal gas will be transported from West Texas or Western Canada.
The compressor power, distance, and gas throughput for several pipeline projects was summarized by AGA (AGA 1993). The average energy use is 0.014 hp/Mmscf/d. Compression energy represented on a per mile basis ranged from 0.6 to 2 hp-hr/MMscf/mi with a weighted average of 0.9 hp-hr/MMscf/mi for Western States. Emissions from compressors are based on emission rates and transportation distances in Section 4.1. The emissions database calculates emissions in g/1000 mi/100scf. Compression energy usage is calculated in terms of a percentage of 1000 mi transported.
4.10 Toxic Emissions
California Assembly Bill AB 1807 created a comprehensive program to address adverse public health impacts from emissions of toxic substances to ambient air. Toxic air contaminants are an air pollutant that may cause or contribute to an increase in mortality or an increase in serious illness. A series of compounds were identified by ARB as toxic air contaminants, five of which are related to the combustion of fuels. They are 1,3-butadiene, benzene, formaldehyde, acetaldehyde, and diesel particulates. In addition, there are several compounds that are precursors to toxic air contaminates. Polycyclic aromatic hydrocarbons (PAH) and nitro-PAH are such precursors. Combustion compounds in diesel exhaust that are PAH and nitro-PAH are given in Table 4-30.
Toxic emissions and toxic precursors were estimated for diesel engine exhaust, diesel fuel, diesel fuel vapor, natural gas, liquid petroleum gas, refinery emissions, pipeline compression engine emissions, and power plant emissions. They are given in terms of milligrams of toxics per gram of NMOG in Table 4-31. Discussion of the findings can be found in the following subsections.
Table 4-30: Polycyclic Aromatic Hydrocarbons (PAH) and Nitro-PAH Found in Diesel Exhaust